Electronic Environment no 2 2015

A pirimer on pim

interference problem in wireless systems

What is EMI/EMC?

An introduction to interference control Standards, Methods and Issues of

Destructive High-Power Microwave Testing

on the EMC Performance of Cable Trays CONFERENCES & EXHIBITIONS page 6 • Eye on… page 12 >>>

Call for Papers April 19-21, 2016, Kistamässan, Kista Science City Electronic Areas: EMC, ESD, energy storage and environmental engineering for electronics.

The Electronic Environment magazine again plays host of the EE Conference, a recurrent event, which now is organized for the fifth time in April 2016. This time EE 2016 is arranged in parallel with S.E.E 2016, the largest meeting place in Scandinavia for the professional electronics industry, at Kista Expo, Kista Science City.

At the Electronic Environment Conference 2016 the latest findings and solutions will be presented by Europe's leading profiles and industry experts.

The qualified lectures, workshops and panel discussions will create interesting new opportunities, opportunity to exchange experiences and having creative meetings where new ideas flows, Industry, government and academia meet – exciting encounters that generate new ideas and innovative solutions.

Call for Papers We are looking for lectures and workshops aimed at practicing engineers, designers and technicians, quality managers, test and certification functions and management.

We welcome suggestions for lectures in EMC, ESD, environmental engineering for the electronics and energy storage in the following thematic areas: • Vehicles, Aviation & Marine • Industrial environment • Security & Defence • Telecom • Smart grids & DC network • Power quality • Testing & Simulation • Standards & Certification

Take the chance to present your findings, research results and experiences for a very interested and specific audiences. Share your knowledge, spread the findings of new observations or forgotten experiences. Present new regulations and standards.

Raise awareness or debate. Improve knowledge and experience, broaden the network of contacts and share your expertise.

Welcome to participate at EE Conference 2016!

• Quality assurance

Deadline for abstracts: 31 augusti 2015

Send to mail: info@justevent.se

• Extreme & Explosive environments • Other suggestions are also welcome!

We would like to have a brief description of your presentation (abstract) by August 31. The final manuscript should be submitted at latest Dec. 31, 2015.

Further instructions will be communicated in connection with the acceptance letter in October 2015.

We welcome your abstract!

Workshops, oral presentations and poster presentations The sessions are divided in various thematic categories so that the conference participant can follow a specific interest. The participant may also choose to simply follow a specific field, selected from EE 2016´s various electronics fields.

The conference program will be extended by an additional day in relation to previous years, to a total of three days. The first day is devoted to workshops, and the remaining days for oral and poster presentations.

The oral presentations are scheduled for 30 minutes each, including set-up time, and time for questions.

Poster presentations will be presented during the last two days. Presentations will be held in Swedish or English.

Speakers will receive: • Full conference documentation • Refreshments, lunch and conference dinner • Free participation on the day of the presentation Contact information The program committee looks forward to your abstract! If you have questions please feel free to contact us by phone +46 31-708 66 80, or by email info@justevent.se Project Manager: Dan Wallander, +46 31-708 66 91 dan.wallander@justevent.se Partners of Interest:

EE Conference 2016 - in parallel with S.E.E 2016 Electronic Environment Conference 2016 will be held in parallel with the Nordic region's largest meeting place for the professional electronics industry, S.E.E, 2016 at Kistamässan, giving unprecedented conditions; an incredibly exciting venue and the possibilities for interesting meetings for both conference participants and exhibitors will be large – a dynamic meeting place for new knowledge, new contacts and new business.

Kistamässans strategic location and accessibility in the heart of Kista Science City, is an excellent forum for professional meetings and creative events. Kista is a region in transition with a constant flow of people, impressions and experiences.

Kista Expo is centrally located in the north of Stockholm and its proximity to Arlanda and Bromma airports creates favorable conditions for international contacts.

In just 12 minutes by commuter train from Kista Expo you are in the heart of Stockholm. With close proximity to the E4, subway, commuter trains and buses Kista Expo can be reached easily regardless of origin. Directly adjacent to Kista Expo there are plenty of parking places.

You’ll find more information at www.electronic.nu

Organizer:

Reflections

We have now taken the next step to welcome all our new readers to the magazine Electronic Environment, which after 20 years on the Scandinavian market, is now going through a significant phase of development, with the aim of distributing the magazine worldwide.

I would like

The magazine's website , www. electronic.nu, is now bilingual, and it brings our services, products and activities together. You will find articles and news items, earlier editions of the magazine, conference pages, our e-courses and much more on the website. It also includes an international supplier guide for the electronic environment field.

I also want to welcome our new Technical Editor, Michel Mardiguian. Michel is known for his EMC work, and has written eight books on the subject. Two of them have been translated into Japanese and Chinese He has also written two books along with Don White.

Michel will contribute in each issue of the Electronic Environment, starting in this one.

start a new series in this issue, "The 10 EMC Commandments". He will hightlight PIM, which is an acronym for Passive Intermodulation, an interference problem in the wireless system. You will also find the extensive article "Standards,

Miklos Steiner will

Methods and Issues of Destructive High Power Microwave Testing".

gazine and our newsletter among your collegues.

We are currently distributing a Second Call for Papers for the EEC 2016 in Stockholm. There will be lectures and workshops aimed at practicing engineers, electrical constructors and technicians, quality managers, test and certification professionals and management. Please provide a headline with a brief description of the lecture to us (an abstract) no later than August 31.

Once again, welcome to the magazine Electronic Environment! I hope you enjoy it and I wish you a great summer!

On www.electronic.nu you will find more interesting articles in the electronic environment field. You are welcome to distribute our ma-

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Electronic Environment is published by Just Rivista AB Mässans gata 14 SE-412 51 Gothenburg Tel: +46 31-708 66 80 info@rivista.se www.rivista.se Address Changes: info@justmedia.se

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Shielded meeting rooms Turn key shielded and anechoic chambers Shielded rooms for data security Shielding materials for self-assembly: doors, windows, absorbers, ferrites, filters, gaskets and metallized textiles.

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Technical Editors: Peter Stenumgaard Miklos Steiner Michel Mardiguian

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Our technical editors reach on: info@justmedia.se

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Cover Photo: Thinkstock

www.electronic.nu – Electronic Environment online

Printed edition: Billes, Mölndal, 2015 Contents may not be reproduced in any form without the prior consent of the authors.

While every attempt is made to provide accurate information, neither the publisher nor the authors accept any liability for errors or omissions.

Content, Electronic Environment 2.2015

6

EE-Calender

8

A primer on PIM

12

Conferenser and courses

interference problem in wireless systems

Eye On: What everyone should know about EMC The ten commandments for EMC, part 1

20

14

EMC problems caused by ageing products

17

What is EMI/EMC?

30

On the EMC Performance of Cable Trays

– a real world example

An introduction to interference control

How to improve EMC performances of cable installations

Standards, Methods and Issues of

Destructive High-Power Microwave Testing

Technical Editors Michel Mardiguian

Peter Stenumgaard M.Sc. In Applied Physics and Electrical Engineering, Linköping Institute of Technology, 1988. PhD in Radio Systems Technology, Royal Institute of Technology 2001. Until 1995, he worked as systems engineer at SAAB Military Aircraft with electromagnetic effects on Aircrafts. This included e.g. Lightning, Electromagnetic Pulse (EMP) and High Power Microwaves (HPM).

He has been an adjunct professor both at the University of Gävle and at Linköping University. Today is a Research Director at the Swedish Defence Research Agency (FOI). He is specialized on electromagnetic interference on wireless communication systems. He was technical program chair for EMC Europe 2014 International Symposium on Electromagnetic Compatibility.

Miklos Steiner Miklos has vocational high school education and training in mechanics and electronics, higher education in telecommunications and electronics, and an extensive experience from service and repair of consumer electronics, electronic design and project management of microprocessorcontrolled printers, price labeling machines and dispensers, industrial control systems and installations.

Miklos has since 1995 trained a large number of engineers in EMC and is also author of the popular EMC series "Eye On" in the magazine Electronic Environment. For many years, Miklos worked as EMC consultant, with EMC design and EMC testing for many customers. He has also been an instructor and led many EMC courses for electronics engineers, mechanical engineers and installers.

Many years of experience in the development of EMC solutions in these missions have given Miklos basis, he credibly able to pass on in advice, courses and articles.

Michel Mardiguian, IEEE Senior Member, graduated electrical engineer BSEE, MSEE, born in Paris, 1941. Started his EMC career in 1974 as the local IBM EMC specialist, having close ties with his US counterparts at IBM/Kingston, USA. From 1976 to 80, he was also the French delegate to the CISPR. Working Grp on computer RFI, participating to what became CISPR 22, the root document for FCC 15-J and European EN55022. In 1980, he joined Don White Consultants (later re-named ICT) in Gainesville, Virginia, becoming Director of Training, then VP Engineering. He developed the market of EMC seminars, teaching himself more than 160 classes in the US and worldwide.

Established since 1990 as a private consultant in France, teaching EMI / RFI / ESD classes and working on consulting tasks from EMC design to firefighting. One top involvment has been the EMC of the Channel Tunnel, with his British colleagues of Interference Technology International.

He has authored 8 widely sold handbooks, two of them being translated in Japanese and Chinese, plus 2 books coauthored with Don White.

www.electronic.nu – Electronic Environment online

5

EE-Calender

CONFERENCES & EXHIBITIONS 6th Annual Electronic Warfare/Cyber Convergence Conference June 2 North Charleston, SC, USA

2015 Wireless & EMC Europe Training Tour June 23 Ratingen, Germany

Electronic Systems Design for EMC Compliance June 3 Madison, Wisconsin, USA

5G World Summit June 24-25 Amsterdam, Netherlands

ICC 2015 June 8-12 London, Storbritannien

Satellite Interference Reduction Workshop June 25 Paris, France

EMI Suppression Skills for Power Electronic System Design June 9 Rockford, Illinois, USA 15th IEEE Conference on Environmental and Electrical Engineering (EEEIC 2015) June 10 Rome, Italy

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2015 Wireless & EMC Europe Training Tour June 16 Como, Italy

2015 EOS/ESD Symposium June 30 Seoul, Korea 2015 Wireless & EMC Europe Training Tour July 1 Fleet, Hampshire, United Kingdom

2015 IEEE International Symposium on Antennas and Propagation Joint CNC/ USNC-URSI Meeting July 19 Vancouver, British Columbia, Canada Military Standard 810G Testing 4-day Course July 20 Munich, Germany Embedded Systems Conference July 20-22 Santa Clara, USA NEMO 2015 August 11 Ottawa, ON, Canada EMC Europe & IEEE International Symposium on EMC August 16-22 Dresden, Tyskland

www.electronic.nu – Electronic Environment online

EMI Suppression Skills for Power Electronic System Design September 6 Rockford, Illinois, USA Metamaterials 2015 September 7, Oxford, United Kingdom Plastic Electronics October 6-8, Dresden, Tyskland

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Engelsk annons Electronic Environment nr 2 2015.indd 1

2015-05-11 14:53:35

Electronic Environment 2.2015 Eng

For intermodulation to occur, two or more signals need to be multiplied. A common way to achieve this is to add the signals, and to pass the sum through a nonlinear device.

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www.electronic.nu – Electronic Environment online

Electronic Environment 2.2015 Eng

A Primer on PIM Background: PIM is an acronym for Passive InterModulation, an interference problem in wireless systems. The problem is not new, but has been known since long time back by designers of, for instance cell phone systems, space probes, connectors, coaxial cables, antennas and filters. The problem most frequently occurs, when dealing with high RF-currents in confined spaces. In this text, the basic theories behind PIM will be briefly discussed.

Intermodulation Intermodulation is a process where two or more signals, having frequency components ƒ1 , ƒ2 , ... etc, are mixed in such a way, that new frequency components, not belonging to the initial set of frequencies, are created. In some applications, for instance amplifiers, intermodulation causes distortion of the signal, and is not a desired property.

In mixers, modulators and demodulators however, intermodulation is used to shift signals from one frequency band to another. In this case, it is a desired feature.

Now, assume the input signal x(t) to the device consists of two cosine functions, with frequency ƒ1 and ƒ2 respectively: x(t) = cos(2πƒ 1 t)+cos(2πƒ 2 t) then, the output signal will be: y(t) = kx(t) = k cos(2πƒ 1 t)+k cos(2πƒ 2 t) The output signal only contains frequencies ƒ1 , ƒ2 , ..., the same frequencies as in the input signal. Perfect!

For intermodulation to occur, two or more signals need to be multiplied. A common way to achieve this is to add the signals, and to pass the sum through a nonlinear device. To illustrate the properties of a nonlinear device, let us start with the concept of linearity. Assume we have for instance an amplifier, with input signal x(t) and output signal y(t).

The relation between the two signals can, in a linear case, be expressed as: y(t) = kx(t), where k is the gain, which is a constant. The linear amplifier is simply a perfect proportionality, as shown in figure 1. A straight line, passing thru the origin, where k is the slope of the line.

An example can be found in figure 2.

Figure 1. The transfer curve of a linear device.

Figure 2. Example of transfer curve of a nonlinear device.

Now, for the nonlinear device, say for example that the transfer function of the amplifier is: y(t)=x3 (t), i.e. the output signal is the input signal raised to three.

www.electronic.nu – Electronic Environment online

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Electronic Environment 2.2015 Eng

This is certainly NOT a straight line, and is therefore a nonlinear transfer function. The formal requirements of a linear transfer function are:

If the same input signal as above is applied to this nonlinear device, the output signal will be:

between two materials. For example, oxidation on a contact surface may contribute a MIM-diode. MIM stands for Metal-Insulator-Metal.

This is a nonlinear quantum effect. MIM-diodes suffer from poor mechanical stability, but they can operate at very high frequencies, above 10 THz. They have also been considered for solar energy conversion.

So, to avoid PIM problems, select materials carefully, and keep your connector surfaces clean from oxide and dirt.

PIM in practice We will use a typical GSM base station to illustrate the practical problems with PIM. The GSM system is a full duplex system, which implies that all transmitters and receivers will operate simultaneously. To avoid interference, different frequencies are used. In for instance the PGSM-900 band, an uplink band is defined between 890.0 - 915.0 MHz, and a downlink band between 935.0 - 960.0 MHz. The uplink is from the handset to the base station, and the downlink the other way round.

The four terms can be rewritten as:

Here it is obvious that a number of new frequency components have been created. If we examine the expression above, we find: ƒ1 , ƒ2 , are the original frequency components, no problem. The frequency components 2ƒ1+ƒ2 , 2ƒ2+ƒ1, 3ƒ1 ,3ƒ2 are quite high frequencies, compared to the desired ones, and can often be filtered out easily. But 2ƒ1 – ƒ2 and 2ƒ2 – ƒ1 pose problems, since they are close to the desired frequencies, and cannot be removed using filters.

In this case, the nonlinearity had the exponent 3, and the frequency of the problematic intermodulation products were 2ƒ1 – ƒ2 and 2ƒ2 – ƒ1. If the exponent had been 5, the problematic frequencies would have been 3ƒ1 – 2ƒ2 and 3ƒ2 – 2ƒ1. For exponent 7, 4ƒ1 – 3ƒ2 and 4ƒ2 – 3ƒ1 would be created. In the general case, this group of intermodulation products, can be expressed as ƒIM = mƒ1 – nƒ2 , where m and n are integers. The order of the intermodulation products are obtained as m + n. So far, only odd exponents, i.e. intermodulation orders have been studied. It is an interesting fact, that even numbered orders never produce frequency components close to the desired, original frequencies, and therefore, in most cases do not present a problem.

Nonlinearities The nonlinear mechanisms considered in this context are passive. Passive means that the device does not have a power supply. Examples: connectors, cables, antennas etc. It may even suggest that mechanical, non-electric parts, e.g. cable clamps, handles and bolts can act as passive nonlinearities. Nonlinearity often gets more pronounced at higher signal levels, i.e. strong RF-currents. There are basically two situations, where a part may carry strong RF-currents.

Typically, we will find a number of pretty strong radio transmitters transmitting in the downlink band, while a number of sensitive radio receivers operate in the uplink band. Obviously, we do not want any signals from the downlink to interfere with the delicate signals in the uplink. As long as everybody stays on their allocated frequency, all will work fine. However, intermodulation has the nasty effect of creating new frequencies that are not expected...

The downlink band harbors 124 channels. If we transmit on p channels, there may occur p(p–1) problematic intermodulation products.

This means that in worst-case, 15252 intermodulation products will be generated. This is a simplified example, in reality there are many more frequency components to take into account (due to the modulation of the signals). Often, the intermodulation products may not be experienced as discrete frequencies, but rather as a general increase in the noise floor.

Where in the frequency band may the intermodulation products show up then? Doing some calculations, varying the transmitting frequencies ƒ1 and ƒ2 from the lower to the upper limit of the downlink, we can find the location of the intermodulation products. For third order products the frequency of the intermodulation products are given by 2ƒ1 – ƒ2 and 2ƒ2 – ƒ1 , for the fifth order by 3ƒ1 – 2ƒ2 and 3ƒ2 – 2ƒ1 and for the seventh order by 4ƒ1 – 3ƒ2 and 4ƒ2 – 3ƒ1. As can be seen in figure 3, the intermodulation products occur pair wise and symmetrically round the downlink band.

Yellow is the downlink. Purple is the third order, blue fifth order and pink seventh order intermodulation products. (Only intermodulation products outside the downlink band shown).

The first case is conducted current. Current originating from e.g. a strong radio transmitter. A typical situation is RF-current flowing in cables, connectors, cable joints and antennas. If, for instance, a connector act nonlinearly, intermodulation products may be created.

The second case is current induced by radiation. Metallic parts in the vicinity of a transmitter antenna, will pick up RF-power from the electromagnetic field and convert it into a RF-current in the part. If the part has a nonlinear behavior, intermodulation products may occur, which will then be reradiated as wireless interference.

But why do metallic parts have nonlinear current behavior? There are mainly two mechanisms involved. The first one is the properties of the conducting material itself. For example, some magnetic materials may exhibit a nonlinear performance, due to the fact that the current causes magnetic fields, and that magnetization curves are nonlinear for strong currents. In other cases, the nonlinearity of a material may be caused by polarization issues.

The second mechanism is caused by surface effects in the interface

10 10

Figure 3. Frequency ranges of uplink, downlink and intermodulation products outside the downlink.

The green band in figure 3 is the uplink. It is clear that the frequency range of the intermodulation products overlap considerably, and that the risk for interference is imminent. Raising the noise floor, in the sensitive uplink, degrades the performance of the radio links and the base station, thus reducing the revenue. So, at last, a word of wisdom: Stay linear!

Dag Stranneby Dag is performing PIM studies at Campus Alfred Nobel, Örebro University, in collaboration with Nolato AB in Hallsberg, Sweden.

More information can be found at: http://vimeo.com/dstranneby/pim

www.electronic.nu www.electronic.nu –– Electronic Electronic Environment Environment online online

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Electronic Environment 2.2015 Eng

EYE ON...

Vad alla bör känna till om EMC: What everyone should know about EMC:

EMC från Groundbricka planetill bricka, del 6 THE TEN COMMANDMENTS FOR EMC, PART 1

EMC is a complex topic. To achieve the desired EMC characteristics of a product, in an efficient way, often requires collaboration between different professional groups. In addition to electronics designers, all parties involved should have the understanding and basic knowledge of the subject. The most concerned may be: mechanical designers, project managers, machine builders, installers, and others.

To facilitate this collaboration, I will in this and future articles explain these concepts.

See Figure 1.

GROUND PLANE It is one of the most important concepts in EMC. Ground plane is good! Create ground plane! Create one common ground plane!

All materials with good conductivity (low impedance) can act as a ground plane at all frequencies, provided the plane is wider than the projected area of the circuit or the apparatus it is supposed to shield. The circuit or apparatus should also be placed as close to the plane as possible. A ground plane need not be plane, it may assume any shape. “Ground plane” in this context means also bounded electrically conductive structures. See figure 2."

In order to ensure that a ground plane obtains low impedance (in the entire frequency range of EMC), if the ground plane consist of more than one pies of metal, it must have as many and broad parallel bonds between parts as possible. (Many large conductive surfaces mating in the bond.)

12

A metal structure which surrounds, or is carrier of the electric and electronic circuits of the device, is sometimes called chassis ground. In practice the chassis ground is regarded as an extension of a circuit ground plane.

• Ground plane • Zoning • Shielding

Note that “ground” by definition is the metallic part of the shield!

• Slots and apertures in the shield

Examples of ground planes: unbroken copper layers in a printed circuit board, unit housings, chassis or rack, shielding plate, cable shield, cohesive installation mechanics and so on.

• Low impedance bonding

Advantages of a ground plane: • very low intrinsic impedance (inductance), see Figure 3.

• acts as “generic shield” (is part of as mentioned above) • reduces mutual impedance • reduces field coupling, crosstalk as well as far field, see Figure 4.

• enables grounding for filtering and decoupling (a shield is needed for filters).

• Cable Shielding • EMI Sources, interference victims and paths • Interference suppression, decoupling • Filters, filter placement, and assembly • Wiring and layout of modules Figure 1: The Ten Commandments, EMC

Miklos Steiner miklos@justmedia.se

www.electronic.nu – Electronic Environment online

Electronic Environment 2.2015 Eng

The impedance of a 30 µm thick copper ground plane compared to a straight wire

Figure 2. enclosing plane (shielding box).

Figure 3. The surface impedance.

A

B

E and H "wrongly" polarized = No influence

Figure 4. Shielding with ground plane (ED02)

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Electronic Environment 2.2015 Eng

"When the lamps have reached their service life, the lamp starters begin oscillating as they are trying to re-ignite the lamp"

EMC problems caused by ageing products – a real world example A new product must comply with certain EMC requirements in order to fulfill the essential requirements in the EMC directive. Mostly we take it for granted the product maintains its EMC performance through its entire lifetime. From sometimes bitter experience we know that our dear products fail occasionally, needing repair or replacement. Most people relate failure to loss of function but loss of EMC performance can also occur.

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www.electronic.nu – Electronic Environment online

Electronic Environment 2.2015 Eng

Lights turned off.

Lights turned on (zero span).

Lights turned on.

From the mobile operator.

The distance highlighted in blue. Disturb source is top left and the lighting down to the right.

The authorities try to find non compliant products by means of market surveillance but how about products in use? The authorities for sure cannot examine all products and installations regarding EMC to ensure they fit their electromagnetic environment. Well, inspections sometimes take place but given the total amount of products and installations in existence we have to face the fact it’s impossible to find everything.

In most cases EMC problems are discovered by for example users of radio spectrum, reporting radio interference problems (the classic EMC issue). Here we have a typical example from a mobile network operator experiencing a noisy environment at the uplink (listening frequency) at one of its 900 MHz base stations. In order to get good service time for the mobile telephones the transmitter power for the hand set must be kept low. Also protruding (i.e. efficient) antennas has to be avoided so it is clear that it calls for good radio system performance at the base station end. High gain antennas are used.

The Swedish authorities, in this case Elsäkerhetsverket (the Swedish national Electrical Safety Board), has had several cases with electric lighting causing radio interference. An example is ageing metal halide lamps. The lamps seems to have proper EMC performance when new, also burnt out lamps poses no EMC problems. But when the lamps have reached their service life, the lamp starters begin oscillating as they are trying to re-ignite the lamp. It’s a bit the same situation as for old fluorescent tubes, except that the oscillating rate is much faster for the metal halide lamp, making it hard to actually detect a bad lamp by the eye. Inside the luminaire there is a high voltage starter providing the igniting pulse. At each pulse there is a transient signal. As the igniting sequence normally is very quick the ignition shall pose no interference but the oscillation of a bad lamp is a different matter.

Here we can see the difference in interference level when the lightning illuminating a large shop sign is switched on. The network provider has also presented a graph showing how signal/noise ratio is affected. The sign is illuminated during the dark hours.

The operator has reported loss of network performance because of the interference. After a visit Elsäkerhetsverket has submitted the owner of the sign to correct it to stop it from interfering, this according to Swedish law. The mobile operator has dealt with a number of similar cases with aging metal halide lamps and it is a worrying situation as it is a very common type of lighting. The distance between lamps and antenna was approx 250 meters.

Henrik Olsson Elsäkerhetsverket The Swedish national Electrical Safety Board

SEES is Sweden’s Number One Forum for everyone who is interested in Product Robustness.Welcome to join and take part in interesting meetings with exchange of ideas and experience, value adding projects and annual well renowned courses.

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tel: 08-782 08 50

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Notices

Electronic Environment 2.2015 Eng

An Editor's Reflections

The networked connected society – a vision that requires EMC!

T

he total number of mobile subscriptions in the world is now as big as the world's population. At the same time actors in the mobile communication industry have launched a vision that makes today's mobile use appear only as a starting point. After the third and fourth generation mobile systems such developments are now underway to the fifth generation, 5G.

T

he overall vision for the 5G is the Networked Society, where a massive increase of connected equipment – up to 100 times more – within diverse areas of society envisaged while the data rate to networks must be significantly increased – up to 100 times higher. This time it is not a traditional development of the previous system generations.

Now, the ambition is aparadigm shift – a true connected digital society.

Performance should be raised to the limits of technology to enable applications in most sectors of society such as smart grids, remote health care, control of industrial processes, intelligent transportation systems (ITS), financial services, public safety and disaster relief (PPDR) communications, entertainment and media. The trend is thus driven by new and increased opportunities for the use of wireless technology throughout society.

T

he precondition for the wireless system to function with optimal performance is that no EMC problems limit the use. The EMC-field was born about 100 years ago due to the concern that that the new wireless service of broadcasting could be disturbed by emissions from electrical equipment. The rapid rise of wireless systems, both among private consumers and in critical applications, as predicted in the 5G-development therefore leads to that EMC issues become crucial to fulfill that vision fully. In the automotive industry, considerable steps in this direction have already been taken through the development of intelligent transport systems (ITS) where wireless systems, among other things, will be used for critical services within Active Road Safety.

T

he automotive industry is generally very visible at EMC conferences and shows examples of how EMC issues are taken seriously in their products. Thus, the automotive industry is an example of an interesting model for other industries where EMC issues can have a major impact on product performance and reliability.

W

ith the trend towards 5G, the focus on EMC matters will further increase as the technology is predicted to affect a very large number of new application areas.

Peter Stenumgaard info@justmedia.se

Customize Your Own Cables New RF Cable Assembly Designer Unveiled by Pasternack Customers Requiring Special RF Cable Assembly Configurations Can Now Customize Their Own Cables at Pasternack.com

Irvine, CA - Pasternack Enterprises, Inc., a manufacturer and supplier of RF, microwave and millimeter wave products, has just released their newest engineering resource called the Cable Assembly Designer which allows the user to design and customize RF cable assemblies with an easy-to-use online web application at Pasternack.com.

Pasternack’s new custom cable designer enables engineers and buyers to create customized RF cable assemblies that meet their specifications from any combination of compatible connectors and cables offered by the company.

Pasternack stocks and builds the industry’s most comprehensive selection of RF cable assemblies, with over 250,000 possible combinations, all available to ship the same day they are ordered. Whether you are looking for a common off-the-shelf cable or something unique to your specifications, Pasternack’s new web tool allows you to build your own custom cable assembly from over 1,300 connector types and 115 different coaxial cables (including Twinax).

The RF cable assembly designer from Pasternack lets the user select from a variety of connector and coax parameters that meet their specifications in any order they prefer, such as gender, polarity, body style, max frequency, impedance, coax attachment method and many more. After ensuring all of the parameters for the connectors and coax have been selected, including the desired cable length and quantity, an RFQ is sent to Pasternack’s sales and service team for immediate follow up with pricing, availability and a part number for the assembly. The RF cable assembly designer also allows the selection of numerous value-added services such as custom labeling, lead-free solder/ RoHS compliance and custom booting/heat shrink.

“The new Cable Assembly Designer is a great new resource for engineers looking to easily customize the products they need for their specific applications,” says Steve Ellis, Interconnect Product Manager at Pasternack. “This tool allows engineers to do what they do best – design.”

Source: Pasternack

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PREAMBLE Electro Magnetic Interference (EMI) is the generic term describing a situation whereas an electrical disturbance generated by a certain electronic/electrical equipment is causing an undesirable response to another equipment. This undesirable effect may range from a mere nuisance to a catastrophic failure, with associated financial losses or eventually human casualties. The origin of the disturbance could also be a natural phenomena like lightning strokes or ElectroStatic Discharges (ESD).

ElectroMagnetic Compatibility (EMC) is just the opposite : EMI being the disease, EMC is the cure, that is the discipline analyzing and preventing or fixing interference problems.

WHAT IS EMI/EMC? AN INTRODUCTION TO INTERFERENCE CONTROL

EMI has existed ever since our modern societies started using electricity for transportation, for domestic or industrial power, and for transmitting intelligence - mostly telecommunications and radio. As early as 1915-1920 where wireless transmission (Morse code or voice) started to be common place in military domain, it became rapidly obvious that several ships or army bataillons operating in same area were sometimes unable to properly communicate between each other or with their base station. In those early days of RF engineering, many EMI aspects like receiver selectivity and spurious response, channel separation, high harmonic contents of transmitters and the like were unknown.

So, little by little, some guidelines started popping out for reducing EMI situations to a tolera-

ble level. But more rapidly than some design and fixing rules were put into practice, the astronomical growth of electronics and RF applications after the 1930’s caused the number of EMI cases to skyrocket, in all domains: telephony and telecommunications, air navigation, public radio and TV services, mobile radio etc …. In the major industrialized countries, RF regulation agencies and private industry decided that the days of empirical approaches and EMI « gurus » were counted, and that a methodical strategy was badly needed. EMC was born, not as a new science, but as a multifacet discipline, and a certain number of essential aspects like source & victim dichotomy, coupling mechanisms and the like were set forth, along with specific components, instrumentation and measurement techniques, as will be seen next.

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A measure of this invisible threat is given by the following few examples of the many EMI incidents that occured worlwide in the 1970-1980, period where stringent EMC regulations were not yet applied. EMI manifests in all degrees, from simple nuisances : - 70.000 claims / year (USA) and about 30.000 Claims/year (major European Countries) for jammed public radio and TV reception.

- remote-controlled garage doors or car locking devices jammed by nearby airport radars - video monitors jammed (image flutter) by 50Hz power cables - surveillance cameras jammed by nearby variable speed motor drives - cash registers and electronic weighing machines in food stores displaying wrong figures because of ElectroStatic Discharges - Breath analyzers (alcoholic contents) giving wrong readings when police was using their radio transmitters pumps in gas stations displaying wrong price when drivers were using their CBs , etc … to catastrophy: - medical monitoring devices (ECG, EKG, blood analyzers) delivering wrong values when hospital or emergency squad portable transmitters or paging were used.

- 30m high crane dropping its load in harbour, when dockers were using their talkie-walkies, causing unexpected release of the crane jaws.

- six ferries crashing their piers because their propeller pitch remote control was interfered by local radio-transmitters (Seattle, 1988).

- 134 deaths (seamen and pilots) and $72 millions damage due to a radar beam unexpectedly firing a missile on the deck of aircraft carrier USS Forrestal (1967).

The full list of reported incidents – not to mention the unreported ones because they were not publicized, or the EMI cause not fully demonstrated would amount to an impressive pile.

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Wall Outlet

AC wiring

Fig. 1. Example of a situation where EMI is a simple, but frequent nuisance.

The power drill is causing radiated and conducted interference to the neighbour’s TV set. With analog TVs, degradation was progressive, like blurred, fuzzy picture. With digital TV, degradation is sudden, with loss of pixels, frozzen image or «mosaic».

Aircraft in final descent

ILS guidance beam

Runway

Car CB 27MHz

Fig. 2. Example of EMI situation that could result in a catastrophy. The aircraft, in final approach under no-visual (IFR) conditions is guided to the runway by the ILS beam. Harmonic #4 of the CB in the vehicle on the nearby lane could interfere with the 108 MHz ILS signal, causing the aircraft to miss the runway. Although rare, such incidents do happen, and it takes a well experienced pilot to recognize the anomaly and take over the flight controls.

The Source / Victim Concept Given the complexity of the interactions between the many elements and parameters that are involved, a very clear and simple way for addressing the « who-does-what » of an EMI situation is the source and victim concept (Figurer 3). It states that an EMI problem can be viewed as a theater act staging 3 players : • the source of EMI, which can be a natural phenomenon as with lightning or ESD, or a man-made device that generates high frequency intentionnaly (authorized RF transmitters) or as a byproduct of their operation (digital circuits and switch mode power supplies).

• the victim of EMI, which can be any analog or digital circuit whose low level input can be activated, and eventually damaged by undesired signals.

• the coupling between source and victim, which can be a conducted path, a radiated path or an in-between like cable-to-cable crosstalk.

These three actors are needed on the stage for the performance to exist.

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Fig.3. The source-and-victim concept, a basis of the EMI/EMC strategy. In an interference case, your equipment can be the victim, or the source.

If only one is missing, there will be no playing.

This source (or “culprit“) - coupling path - victim combination is the basis for an overall understanding of EMI, and the key to EMI control in order to reach a satisfactory level of compatibility (EMC). Then eliminating an interference problem can be accomplished by acting on one, or several of the three actors, whichever is accessible to changes, at a reasonable cost.

1) Acting on the source (left-hand column in figure 3). This is of course unfeasible for natural events. It is also hardly feasible with intentional Radio Frequency transmitters, radars etc since these systems are authorized devices, operating at allocated frequencies and designed and installed for performing specific services. Yet, even an authorized transmitter may generate spurious harmonics or other side effects that can be reduced. So, in general, only non-intentional, fortuitous RF sources can be modified so as to reduce their undesired RF emissions. Most common examples are digital circuits, switchmode power converters, motors etc …

2) Making the victim circuit less vulnerable. This carries the constraint that the essential characteristics of this circuit like detection level, bandwidth or time constant etc must not be, or only slightly, affected by the change, since they are necessary to the functional performance. Therefore this option has often a very limited range.

3) Acting on the source-to-victim coupling path. This is probably where the designer has the largest choice of solutions: shielding, filtering, grounding, physical separation or orientation, loop reduction.

An other interesting side of this concept is that it is perfectly reversible.

The mechanisms that could causes the circuit to be a victim are the same that could make it a potential source of interference.

The importance of Frequency aspects Practically all coupling mechanisms that are conveying the source emissions up to the victim’s input are frequency-dependent: as frequency increases, the coupling coefficient increases. In some cases, it may even aggravates as frequency squared.

A quick example can give a measure of this frequency aspect. Assume a long piece of wire carrying a constant value AC currrent of 1A. At 10 cm distance, this 1A current will cause, by magnetic coupling:

- at 50 Hz: 6.3 µVolts in a 100 cm2 loop - at 50 kHz: 6.3 mVolts in a100 cm2 loop - at 5 MHz: 0.63 Volts in a 100 cm2 loop

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Notices

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CE, RE, CS, RS : The four sides of the EMC cube Still based on our source / / victim principle, the reduction of EMI situations to a tolerable level will be secured by controlling the EMC performance of the equipments before they are put on the market.

Proper EMC tests will verify: a) the Emission levels of the equipments, when they are potential sources of interference to nearby systems, or more generally to the outside world. This is accomplished by measuring the amplitude of high frequency noise that is emitted by conduction and by radiation, with specific instrumentation. It is then compared to the applicable norms.

These norms have been devised to protect the users of civilian or military radio spectrum.

- Conducted Emissions (abbrev. CE) are measured on external power cables and eventually telecommunication cables, - Radiated Emissions (abbrev. RE) are measured with calibrated antennas and special receivers, b) the Susceptibility levels of the equipments , when they are confronted to the many electromagnetic threats of their surrounding environment. This is acomplished by simulating an exposure to severe conducted or radiated disturbances, while checking that the equipment under test is still functionning properly.

- Conducted Susceptibility (abbrev. CS) is tested by injecting calibrated HF (sinewave) and transients pulses on external power cables and eventually telecommunication cables, - Radiated Susceptibility (abbrev. RS) is tested by illuminating the equipment under test with strong fields, simulated in an EMC test Faraday cage.

- Some specific immunity tests like Lightning and ESD are also practiced.

The military norms have widely used these very convenient four-letter codes for identifying which EMC tests are required. For instance, RE102 test is a Radiated Emission measurement covering the spectrum from AM radio band up to the upper UHF and MicroWaves.

IntraSystem versus InterSystem EMI/EMC There is an important difference between an interference that is caused to, or suffered from the environment, and the interference inside an equipment that is disturbing itself (self-jamming). These two types of situations are referred to as Intersystem and Intrasystem EMI. IntraSystem EMC is a basic condition for making sure that the equipment is not a victim of itself. So to speak, that there is no internal source-to-victim combination that can create a performance degradation or upset. This is a designer’s responsibility to check first that IntraSystem EMC is correctly addressed, otherwise the equipment will never work properly, even in a non-critical environment.

Our series of EMC articles to appear quarterly in the next issues of the magazine will go more deeply into the essentials of what has just been outlined here: - general overview of the civilian and Military EMC norms, with their rationale, their units and practical test set-up.

- guidelines for designing right from the start a product that will be EMLC compliant, considering PCB layout, internal packaging, box shielding, I/O cables filtering and shielding - guidelines for an EMI-free system installation and - some simple hints for identifying and troubleshooting EMI problems.

Michel Mardiguian, EMC Consultant, France m.mardiguian@orange .fr

MIT Technology Review’s regional ‘Innovators Under 35’ returns Since 1999, MIT Technology Review has honored the young innovators whose inventions and research we find most exciting. The regional list recognizes technologists and scientists, all under the age of 35 whose work spans biomedicine, computing, communications, energy, materials, internet, transportation, and is changing our world.

In all, 20 regional Innovators in Asia have been named in 2014 and 2015.

The 10 selected innovators for 2016 will present a threeminute elevator pitch at EmTech Asia 2016 and will automatically become finalists for the global 35 Innovators Under 35 (TR35) list.

For Peh Ruey Feng, who made it to the 2015 list, being recognized was special because it raised awareness of their innovation to a broader community. The publicity received drove an unexpected level of interest from investors who wanted to seed fund their spin-off company, which has given them the opportunity to progress with a clinical study of their invention later this year.

Peh says, “Receiving recognition from MIT Technology Review is inspiring, as it’s important for those of us who are developing new tech in the trenches of Asia to know that innovations coming out of Asia do get noticed. It also gives investors renewed confidence in the innovation that is taking place in this part of the world, which, in reality is a vibrant scene of innovation. I encourage those who know of people doing good work in this neck of the woods to nominate them because we need to hear more Asian success stories to inspire us to better innovate."

Another finalist, Zhou Lihan received a grant for his work at MiRXES post receiving the recognition. “MiRXES has developed technologies for the detection of a novel class of gene biomarkers called the microRNAs and is applying the technology to develop blood based cancer diagnostic kits to address unmet needs in non-invasive early cancer detection. Being listed this year as an Innovator Under 35 on the regional list has brought us great visibility regionally and globally. We are now pursuing Series A funding.”

Nominations for the 2016 list are now open for submissions at www.emtechasia.com. Nominees must be under the age of 35 as of 1 October 2016. They must be citizens of (or work in) one of the following countries: Singapore, Malaysia, Cambodia, Philippines, Indonesia, Thailand, Vietnam, Laos, Myanmar, Brunei, Australia and New Zealand.

Submit your nominations now!

Timeline for Submissions and Judging • 27 April TR35 Asia nominations open • 18 September Closing of nominations • October Judging and selection process • November Announcement of 10 honourees via website and press release

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Source: EmTech Asia

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Standards, Methods and Issues of

Destructive High-Power Microwave Testing

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The possible threat of a high-power microwave (HPM) weapon that destroys electronic equipment or its function is today taken seriously, and test methods and test standards are slowly adapted to this situation. However, a complete standard methodology for destructive HPM testing of complex electronic systems does not exist.

In this article, the current status of relevant standards is reviewed, and FOIs ongoing work to contribute to the development of an up-to-date standard is mentioned.

Index Terms— High-Power Microwave (HPM), High-Power Electromagnetic (HPEM) Environment, Standards, Destructive Testing, Test Methodology, Reverberation Chamber, Vircator

Issues with HPEM Destructive Testing Four issues that have to be considered in HPEM destructive testing have been identified:

Introduction The progress in technologies pertinent to the generation of directedenergy weapons based on non-nuclear high-power electromagnetic [1][2] has reached a sufficient maturity for allowing a development of high-power microwave (HPM) weapons and for taking the step from the laboratory into the operative arena [3][4], where the objective of the HPM weapon is to intentionally destroy electronic equipment or its function. The HPM threat is acknowledged in official government reports (e.g., [5]) and compilations of hundreds of radiation sources exist [6][7].

Furthermore, HPM weapons are also mentioned as being explored to be a part of U.S. offset strategy for their global military power projection capability [8].

During the last decade there has been an increasing use of complex and networked electronics for all kinds of military applications, as for example in command, control, communications, computers, and intelligence (C4I) systems, weapons systems and even in ammunition. This trend is expected to continue to escalate in the near future. As a consequence, military missions become more and more dependent on operational reliability of electronic systems and therefore increasingly vulnerable to electromagnetic attacks (EA) in general, and HPM weapons in particular [9]. Qualification testing of military equipment with respect to this kind of intentional electromagnetic interference (IEMI) will be an important step in protecting one’s own electronic systems.

The high-power electromagnetic (HPEM) environment caused by HPM weapons has been introduced in standards and some test methods have been outlined. However, a complete standard methodology for HPM susceptibility tests on complex electronic systems does not exist. In this article, we present issues with high-power destructive HPM susceptibility tests, summarize relevant standards and outline a test methodology.

• Susceptibility testing is heavily time consuming if results are to be statistically relevant.

• Destructive tests involve the destruction of many test objects – which may be costly.

• Destructive tests are in the regime of non-linear irreversible effects.

• In an electronic device or system, different individual components might be affected when varying the frequency or the angle of incidence.

These four issues are elaborated upon in this section.

To fully determine the electromagnetic susceptibility of a device, it is required to illuminate the device under test (DUT) from many different directions, especially if the DUT is large in relation to the wavelength [10], at every frequency using at least two polarizations. Figures 1 and 2 illustrate the importance of high resolution in both direction and frequency measurements. Figure 1 shows the results of a radiation susceptibility test in an anechoic chamber using 120 angles and two polarizations [11]. The test took 48 hours. The figure clearly shows that a slight change in angle of incidence can give a large change in the electromagnetic coupling into the object. Figure 2 shows the measured shielding effectiveness of a device [12]. As seen in the figure, a slight shift in frequency can give a large difference in shielding effectiveness.

Thus, a test matrix that covers all directions as well as every frequency in a relevant frequency band will be very costly both in time and in test objects. Hence, a more efficient, but still relevant, test method is required.

As an HPM weapon aims at achieving destructive effects, the system response will be non-linear and scaling from low-level coupling measurements or disturbance tests will not be possible. It follows that testing

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must be performed in the destructive non-linear regime. It should be noted that destructive HPM effects may be due to several different physical mechanisms, mainly related to either the absorbed electric energy or to the electric field strength [13][14][15]. For example, overvoltages can lead to a high-voltage dielectric breakdown or to surface inversion due to mobile ion contaminants. An electric breakdown can result in a current surge evaporating material. Induced voltages of the same order as the circuit operating voltage may lead to a temporary upset (non-destructive) [2]. Bursts of HPM pulses can result in cumulative effects eventually breaking a component. To find out exactly which mechanism is responsible for a particular equipment failure event can be challenging. It is usually not relevant from a practical point of view which destructive mechanism is achieved, but this has to be considered in HPM susceptibility testing.

Another issue is component testing versus system testing. The Tasca curve can be expressed as the energy density required to destroy an integrated circuit as a function of the pulse length [15]. If the same component of a DUT is destroyed during a test series, the Tasca curve for the system will be related to the Tasca curve of that particular component. But if different components are destroyed at different illumination parameters, the Tasca curve of the system would be related to the envelope of the Tasca curves of different components.

of typical HPEM waveforms in the time and frequency domains as well as some examples of HPEM generators are given in annexes. The classification of HPEM sources in IEC 61000-2-13 is based on the spectral bandwidth. To include as many different HPEM sources as possible, it is recommended to select the low and high frequency limits (fl and fh) of emitted radiation pulses such that 90 % of the total pulse energy is contained within these limits. The standard gives a classification of HPEM sources based on bandwidth as given in Table 1, where the percent bandwidth, pbw, is defined as pwb = 100·2(fh-fl)/(fh+fl) and the bandratio, br, as br = fh/fl.

Table 1. Bandwidth classification of HPEM-sources [16].

Band type

Percent bandwidth

Bandratio

Hypoband or narrowband

pbw ≤ 1 %

br ≤ 1.01

Mesoband

1 % ≤ pbw ≤ 100 %

1.01 < br ≤ 3

Sub-hyperband

100 % ≤ pbw ≤ 163.64 %

3 < br ≤10

Hyperband

163.64 % < pbw ≤ 200 %

br > 10

Table 2. Narrowband electromagnetic environment [17].

Figure 1. Angular dependence of power picked up by a probe inside a DUT where the power is normalised against the external field power. The DUT is of the order of 1 m and has apertures. The test frequency is 4 GHz.

Figure 2. The shielding effectiveness of a “radio equipment” DUT as a function of frequency. The five fixed test frequencies of the Swedish microwave test facility are shown as vertical dashed lines.

Standards – HPEM Environment During the last decade several standards have emerged with descriptions of the HPEM environment relevant for the IEMI threat from HPM. IEC 61000-2-13 The International Electrotechnical Commission (IEC) in 2005 published the IEC 61000-2-13 standard with definitions of a "set of typical radiated and conducted HPEM environment waveforms that may be encountered in civil facilities" [16]. In this document high-power conditions are considered to exist if the peak electric field exceeds 100 V/m. Both single pulse radiation and bursts of pulses are considered as threats. Examples

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Frequency range (MHz)

Electric field (kV/m @ 1 km)

2000-2700

18.0

3600-4000

22.0

4000-5400

35.0

8500-11000

69.0

1400-18000

12.0

28000-40000

7.5

Table 3. Wideband electromagnetic environment [17|.

Frequency range (MHz)

Broad-band electric field distribution (mV/m/MHz @ 100 m)

30-150

33000

150-225

7000

225-400

7000

400-700

1330

700-790

1140

790-1000

1050

1000-2000

840

2000-2700

240

2700-3000

80

The state-of-the-art generator systems considered in the IEC 61000-213 are found to have a field × range-product (rEfar) of at least 15 MV (hypoband and mesoband) or several MV (sub-hyperband and hyperband). The frequency content and field strength govern the amount of disturbance (noise, transient upset, etc.) of HPEM sources, but no information is given on the energy required to destroy electronic components. It is only stated that at 1 GHz, an incident electric field strength of several kV/m is required for permanent damage of electronics in general, and that permanent damage of communications receivers is obtained at a few hundred V/m.

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MIL-STD-464C MIL-STD-464C from 2010 "establishes electromagnetic environmental effects interface requirements and verification criteria for airborne, sea, space, and ground systems" [17] . It cites other standards and documents, including them in the requirements. MIL-STD-464C recognizes subsystem and equipment electromagnetic interference, electrostatic charge, and multipaction as well as external RF electromagnetic environments, lightning, and HPM as potential sources of interference. External electromagnetic environments are defined and tabulated as electric field levels as function of frequency, while requirements are specified per type of platform. The MIL-STD-464C defines HPM as a radio frequency environment produced by sources capable of emitting microwave radiation with high power and high energy density, nominally with peak power over 100 MW, with operating frequency typically between 100 MHz and 35 GHz, in single pulses, repetitive pulses, pulses of more complex modulation, or continuous wave emissions. The standard differentiates between narrowband (pbw < 1 %) and wideband (pbw > 1 %) HPM sources, based on the underlying technology (electron beam diode or similar, and fast switching techniques and impulse generators, respectively). The definition of the HPM electromagnetic environment given in MIL-STD-464C is summarized in Tables 2 and 3. The electric field strength is here given at a distance of 1 km and 100 m, respectively, and is used in examples of calculation of standoff distances for some typical military situations.

NATO AECTP 250 The NATO def ence standard AECTP 250 2nd ed. presents "characteristics and sources for electrical and electromagnetic conditions that influence the design and operation of defence materiel" including RF environments, electrostatic phenomena, atmospheric electricity and lightning, DC and LF fields, nuclear EMP, electrical power quality, etc.

Leaflet 257 [18], treats HPM as a relatively new research area, adapting the schematic comparison of the spectral density distribution for lightning EMP, nuclear EMP and different types of HPM sources from IEC 61000-2-13. AECTP 250 defines the HPM frequency range as in MILSTD-464C and classifies HPM sources into four briefly described types coupled to possible scenarios: • Mobile/platform sources targeting infrastructure facilities from a distance • Portable sources carried into or close to a target • Conducted sources directly injecting energy into conductors • Projectile-based sources irradiating an entire facility It is recognized that the scenario details depend on a number of variables, as infrastructure topology, purpose of attack, etc. In AECTP 250, four HPM waveforms are specified: continuous wave (CW), pulsed narrowband (NB), damped sinusoid (DS), and ultra-wideband (UWB). The available power of CW sources is stated to vary from kW to tens of MW, while pulsed sources go to hundreds of MW or higher.

ITU-T K.81 The recommendation ITU-T K.81 [19], issued by the International Telecommunication Union, contains "guidance on establishing the threat level presented by intentional HPEM attack and the physical security measures that may be used to minimize this threat". The HPEM sources considered are those from IEC 61000-2-13 augmented by additional recent sources. The recommendation introduces an elaborate classification into threat portability levels, threat availability levels, intrusion areas, target vulnerability and immunity levels, etc. and tabulates several examples of HPEM threats and gives examples of required mitigation EM levels. The HPEM threats considered in ITU-T K.81 include impulse radiating antenna, commercial radar, navigation radar, magnetron generator, illegal citizen band (CB) radio, amateur radio, stun gun, lightning surge generator, CW generator, and commercial power supply. Calculated examples of peak electric field strength are given with respect to portability levels and intrusion areas (possible target distance); compiled in Table 4. Except for the first two sources, these are commercially or otherwise available sources for insurgents etc., but ITU-T K.81 does not embrace high-power narrowband HPM sources being developed for military purposes.

Table 4. Typical HPEM threats [19].

IRA (Ø 3.66 m, 60 kV)

12.8 kV/m @ 100 m

JOLT (Ø 3.048 m IRA)

72 kV/m @ 100 m

Commercial radar (5 MW)

60 kV/m @ 100 m

Navigation radar (12 kW)

385 V/m @ 100 m

Magnetron generator (1.8 kW)

475 V/m @ 10 m

Illegal CB radio (4 kW)

573 V/m @ 1 m

Amateur radio (3.5 W, stationary)

286 V/m @ 1 m

Standards – HPEM Test Methods Several standards concerning conventional EMC testing are relevant for HPM/HPEM susceptibility testing, and some of the most pertinent are cited below.

IEC/TS 61000-5-9 The IEC/TS 61000-5-9 [20], discusses methods for the assessment of system-level susceptibility, typically vehicles, aircraft and ships, to HPEM and HEMP (nuclear high-altitude electromagnetic pulse) threats. The standard emphasizes the importance to generate functional and topological descriptions of the system and subsystems before actual testing, i.e. the intentional flow of information in the system and the relative locations of physical units together with their physical interconnections. This is relevant for understanding front-door and back-door coupling paths, which together with the physical dimensions of components and cables can indicate possible weaknesses of the system as well as hints to possible protection measures. System analysis is used to identify critical subsystems and equipment and to select test points with possible high stress levels and function criticality. Actual testing can be performed on the entire system or, if this is too large, on subsystems. Low-level testing can be scaled to threat levels, but does not include non-linear effects such as arcing. High-level tests can consist of current injection into cables or surfaces, of high-level illumination with typical NB, DS or UWB pulsed HPM sources, or of reverberation chamber tests. The experimentally determined susceptibility/immunity results often need to be adjusted with a safety margin due to uncertainties in the test method and system configuration before comparison with a set of HPEM threats. Furthermore, the susceptibility/immunity has to be qualified by classification of the effect by operational criticality and duration. These classifications, as given in IEC/TS 61000-5-9, are reproduced in Table 5 and Table 6.

Table 5. Categorization of effect by criticality [20].

Level

Effect

Description

U

unknown

Unable to determine due to effects on another component or not observed.

N

no effect

No effect occurs or the system can fulfil his mission without disturbances.

I

interference

The appearing disturbance does not influence the main function or mission.

II

degradation

The appearing disturbance reduces the efficiency and capability of the system.

III

loss of main function (mission kill)

The appearing disturbance prevents that the system is able to fulfil its main function or mission.

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Table 6. Categorization of effect by duration [20].

Category

Duration

Description

U

unknown

Unable to determine due to effects on another component or no effect is observed or no effect occurs.

E

during exposure only

Observed effect is present only during exposure to HPEM environment; system functionality is completely available after HPEM environment has vanished.

T

temporary

Effect is present some time after HPEM environment has vanished, but system recovers without human intervention. Follow-up time is shorter or equal to typical reaction/operation cycle of the system.

H

resistant until human intervention

Effect is present till human intervention (e.g. reset, restart of function).

Due to the effect the system is not able to recover to normal operation within an acceptable period (e.g. typical reaction/operation cycle of the system). No replacement of hardware or reload of software is necessary.

P

permanent or until replacement of HW / SW

Effect is permanent; intervention of an operator or user does not recover normal operation. Effect has damaged hardware to the point that is must be replaced or software to the point that it must be reloaded.

The classifications are then combined in a matrix to characterize the effects obtained in testing. High-level HPEM test techniques are discussed in annex H of IEC/TS 61000-5-9. Plane-wave irradiation, as in anechoic chambers or TEM-cells, may present an environment more similar to the actual threat situation, but require an enormous number of tests to be performed at every frequency, angle of incidence and polarization. Reverberation chambers offer a statistically isotropic environment where all coupling paths are excited simultaneously which simplifies testing, but require test levels higher than the expected threat level and cannot represent all threat pulse shapes, in particular very short pulses.

IEC 61000-4-21 Reverberation chamber test methods are described in more detail in the international standard IEC 61000-4-21 [21] . This standard provides comprehensive descriptions of reverberation chamber statistical techniques, test setups, validation methods, and guides for performing radiated immunity, radiated emission, shielding effectiveness, and antenna efficiency measurements.

RTCA DO-160G and DO-357 The RTCA standard DO-160G [22], section 20, on radio frequency susceptibility (radiated and conducted) describes test procedures for injected signals from 10 kHz to 400 MHz and radiated fields between 100 MHz and 18 GHz. The purpose is to "determine whether airborne equipment will operate within performance specifications when the equipment and its interconnecting wiring are exposed to a level of RF modulated power". Equipment is categorized in thirteen categories and tested according to which electric field strengths it should withstand in operation. The standard specifies how to arrange the equipment under test (EUT) electrical bonding, grounding, length and placement of interconnecting cables, antenna orientation and positioning, shielding of enclosure, test frequency spacing, and test report contents. Two ra-

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diated susceptibility test procedures are specified in DO-160G, including field calibration, test set-up, and signal modulations to be used.

The first procedure is using directional irradiation with calibrated fields in an anechoic chamber, and the second utilizes reverberation chamber measurements. For the reverberation chamber method, field uniformity validation, chamber and receive antenna calibration, maximum chamber loading, Q factor and time constant calibration, etc. are described together with formulas for calculation of statistical quantities. A user guide with more detailed specifications and procedures for conducting the radiated and conducted tests described in DO-160G is given in DO357 [23].

MIL-STD-461F The MIL-STD-461F [24] provides interface and associated verification requirements for control of EMI emission and susceptibility characteristics of electronic, electrical, and electromechanical equipment and subsystems. Section 5.20 contains requirements for radiated susceptibility with electric fields between 2 MHz and 40 GHz. Limit electric field levels are specified per type of military platform (aircrafts, ships, submarines, ground, and space) and frequency range. Above 30 MHz, requirements must be met for horizontal and vertical polarization, while testing using circular polarization is not acceptable. Two alternative test procedures are described in MIL-STD-461F: direct EUT irradiation within a shielded enclosure (2 MHz – 40 GHz) and reverberation chamber measurements (200 MHz - 40 GHz). For both, the standard defines test setup with equipment configuration and distances, procedures for calibration of antennas and probes, procedures for EUT testing, as well as data presentation guidelines.

Status of Standards Since the descriptions of the HPEM environment for HPM are based on compilations of data on laboratory HPM sources and commercial radiation sources of lesser peak power, there is some uncertainty regarding which power levels that actually will constitute a real-world HPM threat to electronic equipment. Some standards identify threat situations with specific equipment and distance, which is relevant from a practical point of view, but for the development of test methodology idealized situations must be used and tests be conducted with specific threat pulses.

Some standards (as IEC 61000-2-13 and MIL-STD-464C) focus attention on the HPEM susceptibility as function of frequency and present limits of the electric field for different frequency intervals without regarding other properties of the HPM pulse. This is an important step but does not fully acknowledge the variation in pulse shapes generated by different threat sources. At least the following parameters of pulsed microwave radiation should be considered in the development of a testing methodology for equipment:

• Electric field strength (peak & temporal profile) • Pulse duration • Total pulse energy • Frequency content • Angle of incidence • Polarization

The susceptibility of typical electronic devices varies with frequency, but also the frequency content within the pulse as a function of time as well as the energy content at each frequency may be important for achieving effects. Frequency content, angle of incidence, and polarization determine the effectiveness of radiation coupling into wires and components in the target, while pulse energy, pulse duration, and electric field variation in the pulse (at a fixed coupling) are related to energy and power dissipation into components. This distinction makes it natural to implement a stepwise process for HPM testing: first determine the frequency for which a specific DUT is most susceptible; second investigate the susceptibility as a function of angle of incidence and polarization.

Different HPEM test methods have different advantages. Reverberation chamber testing, e.g. as described in IEC 61000-4-21, is efficient in determining an averaged susceptibility as function of frequency only, but gives no information on the susceptibility as function of polariza-

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Electronic Environment 2.2015 Eng

linear HPEM susceptibility of equipment to destructive HPM pulses needs further characterization and development of test methodology.

To contribute to the development of a standard for a test methodology for destructive HPM testing, FOI is elaborating on a test method that consists of the following two test phases:

Figure 3. Photograph showing the reverberation chamber (RC) with power amplifier and control equipment. The internal volume of the chamber is 1.24 x 0.98 x 0.82 m3, the working volume is 0.72 x 0.56 x 0.4 m3 and the lowest usable frequency (LUF) is 1 GHz. A 5 kW amplifier will generate field levels up to 20 kV/m in the S-band. A pulse length down to 2 μs is possible while complying with the DO-160 standard without having to load the chamber.

• First, the DUT is tested in a reverberation chamber (RC) where the minimum power density required to destroy the DUT is established and at which frequency this occur.

• Second, the DUT is tested for its most sensitive direction of attack and polarization using a frequency-tuned HPM generator or a GTEM cell.

To realize this test method, designated equipment for both test steps must be in place. FOI has established a facility for destructive HPM testing based on an RC for identification of susceptible frequency, lowest electric field strength and pulse length required (Figure 3), and an HPM generator (vircator) for determination of susceptibility as function of angle of incidence, polarization, pulse energy and electric field strength (Figure 4) [25][26][27].

Conclusion The IEMI threat from HPM weapons is emerging and relevant test standards are not fully up-to-date concerning this threat. FOI is dedicated to contribute to the development of standardization of a relevant method of destructive HPM testing.

Anders Larsson, Sten E Nyholm and Tomas Hurtig FOI – Swedish Defence Research Agency Norra Sorunda, Sweden

The possible threat of a high-power microwave (HPM) weapon that destroys electronic equipment or its function is today taken seriously

Figure 4. Photograph showing the HPM generator system. The system can produce a power density of the order of 10 MW/m2 over an area of a few square decimetres where the far field of the antenna begins. The vircator is of coaxial type and powered by a 400 J, 400 kV Marx generator. The system can be operated in single shot mode as well as repetitively up to a repetition rate of 10 Hz. The vircator has a cathode with sectioned electron emitter which facilitates the generation of a TE11 mode. Polarization is changed by rotating the cathode so that the direction of electron oscillation is changed.

tion, angle of incidence or pulse profile. Directional irradiation can provide information on the dependence of the susceptibility on the latter parameters, but requires extensive testing to reach an acceptable level of confidence. Since HPEM effects on particular equipment can vary, a classification scheme is needed. As elaborated in IEC/TS 61000-5-9, effects of different criticality and duration can occur in HPEM exposure.

The destructive HPM testing discussed here would according to Table 5 and Table 6 be described as IIIP. Although there exists standards defining HPM environment and standards for HPM susceptibility testing of equipment, a comprehensive and more general test methodology needs to be defined. The non-

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References: next page.

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Electronic Environment 2.2015 Eng

References [1] D. V. Giri, High-power electromagnetic radiators, Cambridge: Harward University Press (2004).

[2] J. Benford, J. Swegle and E. Schamiloglu, High power microwaves, 2nd ed., New York: Taylor & Francis (2007) [3] M. Gunzinger and Ch. Dougherty, “Changing the game: The promise of directed-energy weapons”, Center for Strategic and Budgetary Assessments, USA (2012).

[4]

R. Jackson, “CHAMP – lights out”, http:// www.boeing.com/Features/2012/10/bds_ champ_10_22_12.html (retrived 31 January 2014)

[16] "Electromagnetic Compatibility (EMC) - Part 2-13: Environment - High-power electromagnetic (HPEM) environments - Radiated and conducted", IEC 61000-2-13, 1st edition, International Electrotechnical Commission, March 2005 [17] "Electromagnetic environmental effects requirements for systems", MIL-STD-464C, Department of Defense Interface Standard, 1 December 2010 [18] "Electrical and electromagnetic environmental conditions", AECTP 250, edition 2, Leaflet 257 "HPM", NATO standardization agency, January 2011

[5] Houce of Commons Defence Committee, "Developing threats: electro-magnetic pulses (EMP)" Report No HC 1552, House of Commons, London: The Stationery Office Limited, February 2014

[19] "High-power electromagnetic immunity guide for telecommunication systems", Recommendation ITUT K.81, International Telecommuni-cation Union, August 2014.

[6] R. Hoad, C. Harper and N. Jenner, "Infrastructure assessment and protection from RFDEW and IEMI environments", presentation at the Directed Energy Systems 2013, London, United Kingdom, 6-7 March 2013.

[20] "Electromagnetic Compatibility (EMC) - Part 5-9: Installation and mitigation guidelines - System-level susceptibility assessmants for HEMP and HPEM", IEC/TS 61000-5-9, Edition 1.0, International Electrotechnical Commission, July 2009

[7] N. Mora, F. Vega, G. Lugrin, F. Rachidi and M. Rubinstein, “Study and classification of potential IEMI sources”, Summa Notes SDAN 41 (2014).

[21] "Electromagnetic Compatibility (EMC) - Part 4-21: Testing and measurement techniques - reverberation chamber test methods", IEC 61000-4-21, Edition 2.0, International Electrotechnical Commission, January 2011

[8] R. Martinage, “Toward a new offset strategy.

Exploiting U.S. long-term advantages to restore U.S. global power projection capability”, Center for Strategic and Budgetary Assessments, USA (2014).

[9] M. Suhrke, “The threat of high power microwaves to infrastructure” presentation at the Directed Energy Systems 2013, London, United Kingdom, 6-7 March 2013.

[10] P. F. Wilson, “Advances in Radiated EMC Measurment Techniques”, Radio Science Bulletin, No 311, December 2004, pp. 65-78.

[11] M. Höijer, M. Bäckström and J. Lorén, “Angular patterns in low level coupling measurements and in high level radiated susceptibility testing", in Proc.

Int. Zurich Symp. Tech. Exhibition Electromagnetic Compatibility, Zürich, Switzerland, 18-20 August 2003 [12] M. Bäckström, K.G. Lövstrand, 2004, Susceptibility of electronic systems to high power microwaves: Summary of test experiences, IEEE Transactions on Electromagnetic Compatibility, Vol. 46, No. 3, August 2004, pp. 396 – 403.

[13] J.H. Yee, W.J. Orvis, G.H. Khanaka, D.L: Lair, "Failure aVnd Switching Mechanisms in Semiconductor P-N Junction devices", IEEE Power Electronics Specialists Conference, Albuquerque, NM, USA, 6 Jun 1983, pp. 154 - 159

[22] "Environmental conditions and test procedures for airborne equipment", RTCA/DO-160G, Radio Technical Commission for Aeronautics, 8 December 2010.

[23] "User Guide Supplement to DO-160G", RTCA/DO357, Radio Technical Commission for Aeronautics, 16 December 2014.

[24] "Requirements for the control of electromagnetic interference characteristics of subsystems and equipment", MIL-STD-461F, Department of Defense Interface Standard, 10 December 2007 [25] T. Hurtig, M. Akyuz, M. Elfsberg, A. Larsson and S. E. Nyholm, "Methodology and equipment for destructive high-power microwave testing", EMC Europe 2014, Gothenburg, Sweden (2014).

[26] T. Hurtig, L. Adelöw, M. Akyuz, M. Elfsberg, A. Larsson and S. E. Nyholm, "Methodology for destructive HPM testing", Electronic Environment, #1.2015, pp 22-27 (2015).

[27] T. Hurtig, L. Adelöw, M. Akyuz, M. Elfsberg, A. Larsson and S. E. Nyholm, "Destructive high-power microwave testing of simple electronic circuit in reverberation chamber", EMC Europe 2015, Dresden, Germany, 16-22 August 2015.

[14] R. Blish, N. Durrant, "Semiconductor Device Reliability Failure Models", International SEMATECH, Technology Transfer #00053955A-XFR, 2000 [15] D. M. Tasca, "Pulse Power Failure Modes in Semiconductors", IEEE Transactions on Nuclear Science, vol. 17, pp. 364-372, 1970.

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Welcome to BK Services!

Sweden’s fastest growing compliance test center for electronic products!

Fully anechoic chamber for radio and EMC tests.

In our fully anechoic chamber we perform radio and EMC measurements up to 26 GHz. Ideal for products with e.g. WLAN, Bluetooth, Zigbee, 868 MHz, RFID etc.

BK Services help you with your compliance testing, enabling you to place your products on the market in a fast and safe manner.

Through our expertise in compliance testing and experience in development we help you through the complete CE-marking process.

Our semi-anechoic chamber for most types of EMC tests.

Our test center is located in Linköping, Sweden just a few minutes from the E4.

Radio - EMC - Electrical Safety - CE-marking Phone: +46 (0)13 - 21 26 50 - www.bk-services.se - info@bk-services.se BK Services, Westmansgatan 47A, 582 16 Linköping, Sweden

Notices

Electronic Environment 2.2015 Eng

New ScopeCorder firmware adds direct MATLAB file saving plus enhanced measurement and recording capabilities Yokogawa has released firmware Version 3.20 for the DL850 ScopeCorder series of instruments, which combine the features of a high-speed oscilloscope and those of a traditional data acquisition recorder in a single, portable instrument.

A key feature of the new firmware is direct file saving into the Mathworks MATLAB® data analysis and visualisation environment, offering users quicker and easier import of measurement data. By supporting MATLAB’s .MAT file format on the ScopeCorder, the measurement results can be conveniently imported into MATLAB more speedily and with smaller file size. The .MAT file format on the ScopeCorder is compatible with Level 5 MAT-files, the latest file format from MATLAB. Other new features include support of an external USB printer for printing on long rolls of paper, and a “sure delete” function for erasing data from the ScopeCorder’s hard disk drive where this is required for security reasons.

In order to support customers that require direct printout of measurement data, such as users of Yokogawa’s earlier SL1400 and OR1400 recorders, the new firmware enables the DL850 ScopeCorder to reprint measurement results on A4 size roll paper using a Brother PJ623/PJ663 USB printer.

Typical customers requiring this facility are found in nuclear power stations and marine applications.

The Version 3.20 firmware also enables the measurement data in the internal storage devices of the ScopeCorder to be deleted completely before leaving a test site. This scenario is sometimes required for security reasons in applications such as government research or in companies working on confidential projects.

In addition to these new capabilities, the Version 3.20 firmware also incorporates a number of enhancements to existing capabilities of the ScopeCorder DL850, including the ability to store GPS position information, an extra fifth

division to the T-Y waveform display, an “infinite” setting for the number of e-mails sent in the “action on trigger” menu, and the addition of a 1A:1V setting to the current probe attenuation.

The GPS capability is useful in on-board vehicle testing such as test drives in remote locations, where data can be stored on trigger events at different locations. It is equally suited to monitoring power distribution networks or smart grids, where the user can trigger in diverse locations and store GPS position data to distinguish transient locations. Similarly, a ScopeCorder can be taken on board a train to store the locations at which certain trigger conditions occur.

The extra “5-division” setting on the T/Y waveform display offers additional flexibility, particularly when using real-time math channels, while the “Infinite” setting for “action on trigger” e-mails adds more flexibility for longtime monitoring.

The new firmware Version 3.20 is now released and is installed on all ScopeCorders delivered from the factory from the end of March 2015. It is available for downloading from the 27 th April 2015. It is applicable to ScopeCorder models DL850, DL850V, DL850E and DL850EV.

Source: Yokogawa

Customized EMC-Solutions KAMIC have more than 30 years of experience, regarding developing and installation of units and products within the electrical environmental area. We are today helping a number of hundreds individual customers and bigger companies with our knowledge in questions related to EMC and improved electrical environment. Welcome to us - we will guide you to your particular customized solution.

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KAMIC Components Box 278, SE-651 07 Karlstad, Sweden Tel: +46 54-57 01 20, www.kamicemc.se

Electronic Environment 2.2015 Eng

Notices

Fairview Microwave Introduces New Family of Broadband RF Amplifiers Broadband Amplifiers with Operation from 0.5 to 40 GHz Released by Fairview Microwave Fairview Microwave Inc., a supplier of on-demand microwave and RF components, announces the release of their expanded offering of broadband RF amplifiers operating in octave bands between 0.5 and 40 GHz with noise figures ranging from 2.5 to 6 dB across the entire frequency range.

Fairview Microwave’s new broadband amplifier portfolio consists of 18 part numbers to choose from that are commonly employed in a wide spectrum of military and commercial applications including wireless communications, telecom infrastructure, radar, electronic warfare, sensors, test instrumentation, microwave backhaul and many others. These wideband amplifiers feature highly efficient GaAs PHEMT semiconductor technology with 50 Ohm hybrid MIC circuits that are enclosed in environmentally sealed metal packages with nickel or gold plating.

The new RF amplifiers from Fairview have gain levels ranging from 20 dB to 48 dB, gain flatness as low as ±0.5 dB and power output ratings (P1dB) from 20 mW to 2 Watts. DC voltage supply ranges from +8.5 to +15 Vdc while bias current ranges from 125 mA to 2500 mA. These broadband amplifiers utilize either stainless steel SMA or 2.92mm connectors and some of the modules are hermetically sealed with field replaceable connectors. The 2.92mm connectorized model operates to 40 GHz. – The expansion of our offering of active RF components is an ongoing company initiative to help meet the demand of our customers and the market, says Brian McCutcheon, VP and General Manager at Fairview Microwave.

– This new portfolio of broadband amplifiers is a sign of commitment to our customers that we will continue to be their on-demand source for all urgently needed RF products.

Environmental testing Ensure the durability of your product A product needs to work in its intended environment, and to withstand transportation. By allowing us to test your product at an early stage of development, we can help to prevent costly redesigns.

Your product will be tested by skilled and experienced staff in one of the Nordic region’s best equipped and most advanced laboratories for vibration, impact, drop and climate testing.

We carry out testing in accordance with levels of standards such as ASTM, ETSI, IEC, IEEE, ISO, ISTA and MIL. www.innventia.com/environmental-testing

Accredited vibration testing since 1994 We are accredited for vibration testing in accordance with the following methods: • • • • • •

IEC 60068-2-6 IEC 60068-2-27 IEC-60068-2-31 IEC 60068-2-57 IEC 60068-2-64 GR-63-CORE

Sinusoidal Shock Rough handling shock Time history method Random Earthquake

Source: Fairview Microwave

CST STUDIO SUITE Student Edition

The CST STUDIO SUITE® Student Edition has been developed with the aim of introducing you to the world of electromagnetic simulation, making Maxwell’s equations easier to understand than ever. With this edition you have, bar some restrictions, access to our powerful visualization engine and some of the most advanced solvers of CST STUDIO SUITE. The CST STUDIO SUITE Student Edition includes time domain solvers, frequency domain solvers, and a selection of static and thermal solvers.

For the CST STUDIO SUITE Student Edition the mesh count available for a solver, as well as some other features, have been restricted. To accompany the CST STUDIO SUITE Student Edition, we have prepared some examples, which are typical of the type of textbook problems you may encounter during your studies of electromagnetic theory or other related courses. If you follow the examples link in the navigation tree, you will find that included with each tutorial is descriptive text, a CST file and also a short video, which shows how to construct each of the models.

Accredited climate tests In our climate tests, cold, heat, moisture and, in certain cases, salt mist are combined and cycled in various ways to meet most testing standards, such as: • • • • • •

IEC 60068-2-1 IEC 60068-2-2 IEC 60068-2-14 IEC 60068-2-30 IEC 60068-2-38 IEC 60068-2-78

Cold Dry heat Change of temperature Damp heat cyclic Composite temp./humidity cyclic test Damp heat, steady state

Boosting business with science

Source: MTT Design and Verification AB

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Electronic Environment 2.2015 Eng

On the EMC Performance of Cable Trays

How to improve EMC performances of cable installations

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Electronic Environment 2.2015 Eng

Shielding and crosstalk measurements have been performed on a selection of cable trays and their implementation. The purpose of the testing was to quantify the shielding and crosstalk (see definitions in side text) performance due to different cable tray systems, and to quantify the impact of poor versus optimal installation of trays and cabinets on EMC for a system (system = a collection of different apparatus with electrical or electronic components). The major conclusion from the study is that cable trays are an integral part of the ground structure (actually, it forms the ground if correctly done; nothing else is needed), which can perform as a shielding structure for the enclosed electronic systems.

The major quality parameter is the connections between the tray parts and the corresponding cabinets. Furthermore, it is found that separation of cables on trays provides little improvement as long as there is no well defined ground structure.

Introduction The use of cable trays for handling of cable routing is mainly focused on the mechanical and geometrical aspects of finding a proper way of routing cables between different systems and apparatus in an installation. From an EMC point of view, however, we must also consider the electrical characteristics of the configuration.

This work was initiated by the Wibe Corporation – a fully owned subsidiary to Schneider Electric – to address the question: is there a difference in the EMC performance between different cable tray types and the electrical connections between mechanical members of the system? In order to answer those questions, we need to expand the question and consider the actual meaning of EMC performance of trays.

The definition of EMC requires a system that can cause interference or be interfered with, i.e. some type of electronics that is performing a function. A cable tray, however, is usually a metal structure that is supporting a set of cables (which in turn do not contain electronics). In order to analyze the EMC performance, we must include the entire system including the electronics sub-systems, the interconnecting cables, the enclosures for the electronics, and finally the metal trays enclosing the cables. The cable trays may thus be a sub-part of a more or less shielding ground structure. The effectiveness of the shield is dependent on the entire quality of the sub-parts and – most of all – their installation.

The importance of installation quality is emphasized in the EMC directive 2004/108/EC [1], which states that the installation shall be designed using good engineering practice. However, there is very little information on what this good engineering practice consists of. Specific technical advice may be found in modern literature [2], though. Focusing on cabling systems, information is also found in installation standards such as EN 50174-2 [4]. Technical specifications on this aspect are also found in the EMMA handbook [3]. The intention of this article is to describe the impact on EMC with different installation quality.

This article contains the test results from shielding and crosstalk performance testing that was performed on a selection of cable trays and their installation. The purpose of the testing was to • quantify the shielding and crosstalk performance of different cable tray systems • quantify the impact of poor versus optimal installation of trays and cabinets on EMC for a system Theoretically, a cable tray installation is usually large compared to the wavelength of most types of disturbances. If the wavelength of the disturbance is comparative to or smaller than the size of the installation, resonance may occur which degrades EMC characteristics. On the other hand a cable tray system may improve the EMC characteristics if the system is small compared with the wavelength. Thus, a cable tray system may mainly improve the EMC behaviour of an electrical or electronic system from 0 Hz up to at the most 10 – 100 MHz, depending on the system size. In the low frequency range 0 – 100 MHz we find for example transients due to short circuits of the power system, leaky power frequency currents, leaky currents from switching

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devices, harmonics to the power frequency, lightning related transients, radio frequency emissions and susceptibility, and more.

Definition of test items and configurations A. Test items The test items were cable tray sections of DEFEM wire trays, Wibe cable trays and Wibe metal trays, as listed in TABLE I. Also a main part of the test set up is a sheet of metal used as a ground reference plane (GRP).

Commercial cabinets were used to make the test object similar to typical installations. The paint was removed from the bottom plate, so that low impedance connection was maintained between the measurement equipment, the cabinets and the ground reference plane (GRP).

The paint was also removed at the interconnection points for trays, cable terminations, and cable connectors.

Figure 2. Typical tray installation (A).

Table 1. List of test items Figure 1. Cable tray types used for the configurations. From right to left: KHZ, W1 and Defem.

Type of equipment

Brand

Description

Tray

Wibe

KHZ

Tray

DEFEM

Cable tray 320/60

Tray

Wibe

W1

Tray

Stago

KB 184 (similar to W1)

Cabinet

Rittal

Rittal compact cabinet AE Conductive wires and plates

Interconnects GRP

Figure 3. Relevant total installation, variant CA with shortest possible connections (lowest connection impedance).

Metal sheet

1.5 x 8mv

Figure 4. Relevant total installation, variant CD with long equipotential connections

B. Cable tray configurations A metallic sheet (GRP) was placed on the floor underneath the test set up to simulate a building ground system and to stabilize the measurements due to an electrically undefined floor. The cable tray structure was connected to this GRP by one or more wires or plates from the ends depending on test set up. The GRP formed the reference for the measured signals. Different cable tray configurations were used for different measurements. The cable trays were laid on consoles mounted on a wall of plasterboards. Three main configurations – A, B, and C – were used: • A consists of one 5 m long section connected to GRP with a wire in each end, see Figure 2. This is the so-called typical tray installation.

The word “typical” relates to the practice of applying equipotential bonding by use of long wires. In these tests, the wires are rather short in comparison.

• B consists of one 5 meters long section, and two vertical sections closely connected to the GRP. This is the so-called optimal tray instal-

32

lation. The word “optimal” relates to making a low RF impedance connection, in contrast to the equipotential bonding practices as above.

• C consists of one 5 m long tray section connected to two cabinets.

This is the so-called relevant total installation. Relevant, in this case, means that we try to resemble a real life installation.

The installation configuration C is used with five variants: • CA: tray and cabinets interconnected with each other with pieces of trays making the shortest possible connections with the lowest interconnect impedance, as shown in Figure 3.

• CB: tray and cabinets connected with two medium long wires (approx. 10 cm).

• CC: tray only connected at one end to a cabinet with one single medium long wire (approx. 10 cm).

• CD: trays connected to the cabinets with very long connections, simulating connection to the equipotential bonding bar in a cabinet, see Figure 4.

• CE: tray and cabinets connected with shortest possible connections (as CA), and the GRP is removed.

Reference measurements were performed with test cables on wooden supports.

II. Development of test methods The characteristics measured and test methods chosen were based on discussions between WIBE and EMC Services, since no specific EMC test methods are available for cabling systems. Several types of tests were developed and performed. These results are documented in [5].

When summarising the results, we found that the following tests were the most descriptive, providing the best information on the EMC performance of the system: • Common Mode (CM) crosstalk between two cables placed within the configuration.

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• Field emission reduction (i.e. shielding effectiveness) from a CM source within the configuration.

Field susceptibility was not chosen because it should give the same answer as field emission reduction, i.e. shielding effectiveness works in both directions.

A. Crosstalk setup The CM coupling between a power cable and a signal cable (not shielded) was measured with a vector network analyser in the frequency range 20 kHz to 200 MHz. The wires of the power cable and the wires of the signal cable were each short-circuited in both ends. One end of each cable was connected to the ground plane (GRP) via resistors of 47 ohm. The output terminal (channel 1 selected) of the network analyser was connected to the power cable and the input terminal (channel 2) was connected to the signal cable, see Figure 5. The reference terminals were connected to the ground plane via a shielding connection box.

Near end cross talk was measured. General cable positions were: a = 25 mm, b = 150 mm, see Figure 6. A view of the configuration C (relevant total installation) is found in Figure 7.

B. Shielding effectiveness setup The emitted electric field due to injected CM signals in a signal cable was measured to evaluate the effect of different cable tray designs. A

Figure 5. Measurement of cable-to-cable nea end coupling (CM crosstalk) in the tray configurations. R1 and R2 = 47 W.

Figure 6. Cable configuration within tray. S1 = transmitter, R1 = receiver.

Figure 8. Principle for generation of CM mode signal and the measurement of high frequency field emission. R = 47 W.

signal generator (a tracking generator) connected to a power amplifier drove a CM mode signal in a centered 2-wire cable shorted in both ends, with one end connected to the ground plane (GRP) via a 47 ohm resistor and the other to the amplifier, see Figure 9. The antenna was connected to the spectrum analyzer (SA) via a pre-amplifier.

The vertical emitted electrical field was measured with a rod antenna (as specified in EN 55025 [7]) in the frequency range 100 kHz – 30 MHz at a distance of 3 m perpendicular to the centre of the cable tray.

The antenna height above the ground was 1 meter.

The vertical and horizontal emitted electrical field was measured with a biconical antenna in the frequency range 30 MHz – 200 MHz at a distance of 3 m perpendicular to the centre of the cable tray, which is similar to the method in EN 55011 [8]. The antenna height above the ground was 1 meter. A view of this setup is given in Figure 8.

Generator and antenna measurement set-up for shielding effectiveness measurement, biconical antenna shown (standby rod antenna to the left), measurement on configuration C, tray KHZ. III. Crosstalk measurements Some examples from the crosstalk measurements are displayed below.

The effect of cable separation is displayed in Figure 10. Here, the typical configuration, A, was used. The results show that there is practically no difference in the results for different separation distances, nor for the difference in tray type. The result is limited by the relatively high RF (Radio Frequency) impedance in the tray connection to GRP. Crosstalk measurements were made on the mesh tray (Defem) in the relevant total installation C, as presented in Figure 11. Here, the results vary drastically with installation type. With a single point grounding of the tray, we even obtain an amplification of the crosstalk compared to a wooden board. With improved RF connection, the crosstalk is decreased accordingly. With the removal of the GRP, we found very little change compared to the continuous tray configuration, implicating that the tray system in itself is the primary ground structure for the test setup.

In the graph for the KHZ system, we see the similar pattern but with lower reduction, see Figure 12. However, the amplification is somewhat

Figure 7. Test set-up for crosstalk measurement, configuration CA (cabinets and continuous tray) with tray KHZ.

Figure 9. Crosstalk measurements. Results for tray system Defem and Stago for different cable placements using configuration A.

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Figure 10. Crosstalk measurements. Results for tray system Defem and Stago for different cable placements using configuration A.

Figure 12. Crosstalk measurements. Results for tray system KHZ for different installation variants.

The results for the KHZ system showed similar behavior but with lower shielding values overall – but with very low field amplification for the single point ground variant. For frequencies above 30 MHz, the field reduction was marginal.

Figure 11. Crosstalk easurements. Results for tray system Defem for different installation (C) variants.

reduced in the single point ground result. Above 10 MHz we find a strong resonance behavior, indicating the general problem of making high frequency measurements with large structures. In addition, a poor quality tray installation – from an EMC point of view – increases the resonant behavior.

IV. Shielding measurements Some examples from the field attenuation (i.e. shielding) measurements are displayed below for the relevant total installation C. The attenuation is calculated as the quotient between the measured field for the given configuration, and the field from the reference measurement using a wooden board.

The results for the W1 tray system in the range 100 kHz – 30 MHz is displayed in Figure 13. For the single point ground we obtain negative shielding, i.e. amplification of the emitted field. However, with improved RF connection, the field is decreased accordingly. Similar to the crosstalk measurement result, we find only a small change compared to the continuous tray configuration with the removal of the GRP. The results for the W1 tray system in the range 30 – 200 MHz is displayed in Figure 14. Due to the large system size (compared to the signal wavelength) the measurements show a resonant behavior. Still, it is possible to analyze differences between the configurations in a broader sense. Here, we find very little improvement of the shielding when using the wire ground connections. Only when applying a continuous tray connection, a reduction in the range of 20 dB is obtained. This means that cable tray systems may provide a shielding effect even up to 200 MHz, but only with optimal low RF impedance connection between tray members and cabinets. The corresponding result for the Defem tray system is shown in Figure 15. The results are similar to the ones obtained for the W1 tray, but with slightly reduced values.

34

V. conclusions A well designed tray system with optimal performance should provide as low crosstalk as possible. In the measurements on the configuration C, the results show that a poorly implemented tray system amplifies crosstalk between cables. The crosstalk reduction is improved with reduced length of interconnects between trays and cabinets (equaling lower connection impedance). The measurements also showed that the crosstalk is independent of cable separation if the RF ground impedance for the system is poor (= high).

The results of the measurements show, that single wire grounding of trays may amplify the field emission at medium frequencies (100 kHz – 30 MHz). Short wire grounding at both ends (configuration CB) gives some improvements, while long wire grounding (configuration CD) has a very small effect. At higher frequencies, only the continuous trays using W1 or Defem gave any field attenuation.

When looking at the system configuration and the corresponding results, we find that the cable tray system (including the cabinets at both end, the interconnects, and the cable tray) very much behaves as a shielding enclosure for an electric or electronic system. The behavior is in practice identical to that for a regular shielded system – consisting of shielded enclosures, shielded connectors and cable shields. For this type of system, the shielding effectiveness is limited by the quality of the shielded connector. There is little use of a high quality cable shield if a high quality connector is not specified. The corresponding behavior of a cable tray system has been found in this measurement study.

With this in mind, the following conclusions may be drawn.

• Cable trays are an integral part of the ground structure, which can perform as a shielding structure for the enclosed electronic systems. If well designed and implemented, it actually forms the ground system.

• The major quality parameters are the connections between the tray parts and corresponding cabinets. This ground plane structure (trays and cabinets) must be greater than the protected system (i.e. no cables shall be outside the shielding structure).

• Separation of cables on the tray is futile as long as there is no well defined RF ground structure.

• If there is no high frequency connection between trays and cabinets, a solid tray provides an amplification of disturbances in the system. In such a case, a plastic tray is preferred and a coarse grid tray is a good neutral option.

• With long wire grounds, so called equipotential bonding (for electrical safety purposes), the impact of the trays is neutral (neither good nor bad).

• Only in the case of high quality (low RF impedance) connections between the tray parts, the shielding effect of a solid tray may be utilized in its full range.

• If a metallic tray system with good high frequency interconnects between parts is maintained, there is no need for any other ground structure,

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Electronic Environment 2.2015 Eng

Figure 13. Field attenuation relative to reference measurement for rod antenna measurement 100 kHz – 30 MHz, W1 tray in different installation configurations.

Figure 14. Field attenuation relative to reference measurement for biconical antenna measurement 30 – 200 MHz horizontal polarisation, W1 tray.

Acknowledgment The authors would like to thank Wibe Corporation for the funding of the project and fruitful technical discussions on the electromagnetic quality of installations.

Figure 15. Field attenuation relative to reference measurement for biconical antenna measurement 30 – 200 MHz horizontal polarisation, Defem tray.

i.e. the system itself becomes a shielding equipotentializing system. A wooden or plastic external weather protection may then be used.

• The use of trays as an enforced electromagnetic protection of electronic systems is a promising technique. However, the knowledge within the installation industry is very sparse. Moreover, the present installation standards provide little help for understanding the importance of the quality of the interconnections between ground structure parts in a system. The implementation of good engineering practice is therefore still a challenge for the future.

References [1] Directive 2004/108/EC of the European Parliament and of the Council, of 15 December 2004, on the approximation of the Laws of Member States relating to electromagnetic compatibility.

[2] Tim Williams, Keith Armstrong, EMC for systems and installations, 2000, Newnes, ISBN 0750641673.

[3] Electromagnetic environment handbook – EMMA, ISBN M7773001271, Swedish Defence Material Administration, Sweden, Part 3 2005.

[4] EN 50174-2 “Information technology – Cabling installation – Part 2: Installation planning and practices inside buildings”, CENELEC, issue 2.

[5] “EMC performance of cable trays – shielding tests”, Report RE10273-17181, EMC Services, Sweden, 2008-03-31, (is available from Wibe Corp. Mora, Sweden) [6] EN 55025 “Radio disturbance characteristics for the protection of receivers used on board vehicles, boats, and on devices - Limits and methods of measurement”, CENELEC, Issue 2.

[7] EN 55011 “Industrial, scientific and medical (ISM) radiofrequency equipment – Radio disturbance characteristics – Limits and methods of measurement”, CENELEC, Issue 4

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Lennart Hasselgren and Ulf Nilsson EMC Services Corp.

SE-431 66 Molndal, Sweden lennart.hasselgren@emcservices.se emculf@gmail.com

35

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Electronic Environment 2.2015 Eng

Background and Comments on the

EMC Performance of Cable Trays T

he study “On the EMC Performance of Cable Trays” (see article in this magazine), started with a contact between EMC Services and the Defem company. Their problem was that their design had been given a lot of criticism in the standard EN 50174-2:2000 (on page 25). The standard was found to contain a lot of formulations on EMC, but there was no rationale for the text – nor were they complete. When we first were introduced to the Defem type of cable tray system we became quite curious: could this be a good alternative to sheet metal cable trays from an EMC point of view? Could this wire mesh tray, built up with metal wires going in parallel (essential for our thoughts) to cables placed on them, be a “ground” as good as sheet metal? We had the feeling it could be so because we saw the resemblance to a transmission line (for common mode currents). We also understood that because of the mesh buildup, a more flexible and continuous ground system could be constructed (among other benefits) in an easier way compared to sheet metal cable trays.

This seemed to be a realistic way of achieving a good ground system compared to the regular split-up “non-ground” ladder type of cable trays, as we saw it. The idea for performing the tests described in “On the EMC Performance of Cable Trays” was to see if this could be the case.

But then again, what do we mean with the word “ground”? Is it a metal rod driven into the soil at the transformer? Is it a bolt in the bottom of the installation cabinet?

Maybe we are using the wrong word, because we actually want to build a shielding metal structure. So we should use the word “shield” instead? Or at least we should say “ground plane” so that the shape is described.

The principle of ground plane and signal transmissions From an EMC point of view, power and signal cables should – together with corresponding cabinets – be placed above a ground plane. This ground plane does not need to be much wider than the cable bundles. Compare with the corresponding printed circuit board (PCB) techniques, where the ground plane always shall be larger than the trace routing.

Zo

Schema

b h

>>b

Tvärsnitt

Figure 1. Simple transmission line called “strip line”.

Figure 2. DM versus CM.

A ground is one of two parts in a transmission line; the “return wire” where the signal current comes back to its origin.

A simple type of transmission line is a conductor placed over a continuous ground plane at a constant height together with the signal and receiving circuits, see Figure 1. This is the same technique as in used in PCBs. The benefits of using a well designed transmission line for signal transmission are several: the signal will be transmitted and received as sent (i e no resonances will occur) and the coupling (field emission, field pickup) to the surrounding will be minimal. To minimize the coupling to the surrounding it is also benefi-

cial to reduce the distance (height) between the signal conductor and the ground plane.

In Figure 1, the characteristic impedance of the transmission line Z0 is due to the height h and the conductor width d. The ground plane shall be quite wider than the signal conductor. The output and input impedances of the driving and receiving circuits shall have the same value as Z0. The signal will be distorted if the width, height or circuit impedances vary – and increased resonance effects, crosstalk and emission will occur.

In our case – consisting of electronic components, cables, cabinets and trays – it is not the intended

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differential power feeds or signals between conductors within cables which are of interest; it is the unwanted common mode (CM) voltages and currents which are of interest. It is those voltages and currents that create the unwanted couplings such as crosstalk, radiated emission and pickup of unwanted fields.

The intention is thus to minimize the CM coupling • between cables (crosstalk) • to cables (immunity to fields) • from cables (emission) by placing them on an high frequency wise high performance, and thus from EMC point of view, cable tray system. Of course, designing and building electrical and

37

Electronic Environment 2.2015 Eng

electronic systems with a minimum of CM voltages and currents (see below) on cables is the first step, but this is seldom achieved in common industrial systems of today. Thus, the next step to minimize CM coupling would be to implement the RF ground plane technique for the CM voltages and currents then designing and building electric or electronic systems.

The simple way to do so would be to implement a ground plane, as good as possible, in the buildup of systems.

The concept of CM and DM Maybe a short explanation of the CM and DM definitions should be given.

Specific for interfering powers and currents are that they can perform in both differential mode (DM) and common mode (CM) unlike a general signal or a power voltage, what only is intended to perform in differential mode. Moreover, CM current can flow without hardwired connection to some return; there is of course always capacitance to the environment. DM voltage is the differential voltage between a pair of conductors (current in opposite directions in the pair). CM voltage performs with the same polarity and amplitude on all wires in a cable relative to a common reference (ground), see the Figure 2. CM current flows in the same direction on all conductors in a cable (including shields).

CM voltage creates no differential voltage between conductors in a cable, unless there is imbalance.

There is always an imbalance, and that is why CM currents are regarded as the major problem when working with EMC. Application to cable trays and the related electronic systems The idea, which is not new for the EMC community, is to adapt existing cable trays to provide a conducting structure as continuous as possible close to the cables. Due to practicalities it is more difficult to achieve continuous common mode impedance in cable tray systems, but the goal should be to do so.

In the article referred to you may see that this idea works quite well: • Traditional cable tray ladders are not providing anything but cable support.

• Trays made by parallel strings (mesh trays) are

38

almost as good as sheet metal cable trays.

• To be of any help for EMC, the cable trays need to be connected together and to the metal cabinets or boxes.

Then all types of trays will provide a protection.

to tell how to design circuits for creation of little CM, but in the article it is mentioned that cable shields, if used, should be connected very well to the cabinets or boxes – at both ends – with high RF quality.

• If mesh and metal trays are only connected at one end, they will act as amplifiers of disturbances.

Who is using this technique – no one?

We mentioned above that the described technique is not new to the EMC community. What´s new is that the tests and experiments performed in the article have not, as far as we know, been performed before. Although other types of tests in this field have been performed indicating the same conclusion:

By making low impedance (wide and short) electrical connections between the metallic members of the system there are also other benefits achieved:

Build cable tray systems as ground planes and make all connections between tray members as short and wide (one wide or several parallel connections) as possible.

• Electrical safety due to low resistance between all electrical parts in the system. Actually, only one connection is needed from a system built like this to the ground point (rod) at the feeding power transformer.

However, all electronic systems will mostly have a separate safety ground wire (PE) anyway.

But no extra equi-potential bonding wires are needed since the resistance of the cable tray system will be far less than such a conductor (maybe some labeling will be needed, but that is a safety issue that we are not experts on).

Our wondering is why people don´t use this simple and cost saving technique in the industry?

• The shorter and wider (or several in parallel) the interconnections (the bondings) are, the better (best high frequency performance).

Why bother about this at all?

Now, if very few industries are using the possibility of making a high frequency low impedance shield for their systems – by using the cable trays – things seem to work anyway? So why bother?

The reason why it – mostly – seems to be working today may be a number of things, here is a short list: • The users do not realize that they have interference, but communications are very slow for some reason.

• For all its drawbacks, the CE marking have created improvements and set a minimum level of EMC performance of apparatues.

• Experienced product designers do not trust the electricians who make the installations.

They add extra precautions and test for worst case – unprotected cable installation.

• The proposed RF shield structure (which is the EMC label for an equi-potential grounding system) will work for relatively high frequencies. That means that it also works for low and medium frequencies, including transient phenomena such as lightning. If the industrial site has a set of over voltage lightning protection (OVP) devices, the function of these will depend on the existence of a low impedance ground reference. If there is no ground plane, the OVPs will be hanging loose in the air and do no good. The RF shield structure (trays and cabinets combined) will provide this critical support.

It is mentioned above that trying to reduce CM noise is basic. How to do so? Well, it is not the place

Figure 3. Photo of the three types of trays that were studied: Defem wire mesh tray, Stago metal tray, and Wibe ladder tray

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39

• For a long time, the industrial electronics has been allowed to emit about 10 dB extra emission (compared to domestic use), since the use of radio communication (broadcast radio mostly assumed) is not regarded critical and therefore not worth the same protection as in domestic environment. This will work anyway if you have the margins on your side.

So if it is working today (at least we would like to think so), why shouldn’t it keep on working? So again, why bother?

Well, the absence of problems in the future would be based on a set of assumptions – and will they hold? Again, a short list • All product designers will be just as skilled and experienced as before, and remember all historical previous problems – maybe...

• All electronics will be working in the same way as today, business as usual – but that means that there will be no development...

• Radio communication is not going to increase, we use cables still – but the reality is the opposite; ”wireless industry” is a big slogan...

In short, electromagnetic environment is not a static situation – it is constantly evolving. But in industrial locations, old equipment is always mixed with new technology – and now we are starting to mix new radio communication systems with old, high RF (radio frequency) emitting existing equipment. New

janlinders .com

sensor technology is also a feature.

So what will you do if you encounter problems with your noise margin for the new system? The solutions could be • Throw out all old equipment and start all over again.

• Increase radio output power (if you have a loud kindergarten, the teacher need to shout louder).

• Use improved communication protocols, works at least for transient phenomena.

• Use the existing installation material, and combine it to a low impedance shield that reduces the field from old equipment inside the shield.

• Our paper describes the last bullet in the list. We think it is worth trying. Which one is the cheapest? Which is the most effective one?

Who should bother, and how?

If the technique of shielding by use of the installation material is not used, it depends on that the stake holders in the industry are not acting on it.

Education To begin with, EMC education is not mandatory in any type of Swedish college education, not even for electronic engineering.

So, tray designers get to know even less, not to mention the installation electricians.

EMC aspects on industrial installations is not very sexy for a Ph. D student either, they tend to focus on complex mathematical calcula-

tions – which is very good and needed, but not in this problem.

Authorities To our knowledge, the authorities (like Elsäkerhetsverket) are focusing on monitoring CE-marked equipment and also to make inspections on premises where there are complaints. This is all very good and needed. But when it comes to EMC requirement on installations, the EMC directive in itself is very vague – giving very little support to the authority on how to monitor compliance. What is a “good engineering practice” in installation?

Our article could be a supporting piece that the authority could use to provide guidelines to the industry. This could be the most effective way to reach out to the industry with relevant information.

Standardization organizations From what we have seen, standardization has been focused on several aspects – but not the ones we have presented here. There is a new version of the EN 50174 series emerging, but we have no new knowledge of this. However, since the standardization is brought forward by the industrial stakeholders in the particular field, it is most likely to be governed by their interests and knowledge. However, with a new version it will be possible to take new steps of improvements if a dialogue with the EMC society (such as IEEE EMC) would take place (which is not the case today).

they will only achieve EMC knowledge on their own based on corporate activities. There is a risk that industrial EMC design is based on traditional principles which are not supported by EMC professionals of today. Since there are so many other aspects of industrial buildings, EMC is often doomed to be of low priority. If EMC is addressed, it is often directed to the use of equi-potential bonding (with the use of long wires that are useless at RF) or the use of cutting off the cable shield on cables (which is also wrong).

The industry needs updated knowledge.

Component suppliers The suppliers of installation material are not used to RF principles. Shielding is not a part of the game. They need to look outside their own products (which are sub-parts of an installation) and realize that the EMC performance is governed by the entire installation. You cannot make a good fix in the middle.

Final words We, the authors, still believe that there are vital improvements that can be made in the industry – and it does not need to cost a lot of money. But the knowledge on how to do it fades away in the abundance of rumors, myths, and old traditions.

So maybe we should apply the kindergarten methodology – we all shout louder? But we would like to see an improved communication instead.

Industry owners Since the industry hires persons that have been educated by the universities and other schools,

Ulf Nilsson emculf@gmail.com Lennart Hasselgren EMC Services lennart@emcservices.se

Modern equipment and front edge competence = correct data values. www.janlinders.com, +46 31-744 38 80, info@janlinders.com

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