Wireless Power Design (Extract)

Wireless Power Design Wireless power transmission has gained significant global interest, particularly with the rise of electric vehicles and the Internet of Things (IoT).

It’s a technology that allows the transfer of electricity without physical connections, offering solutions for everything from powering small devices over short distances to long-range energy transmission for more complex systems.

Wireless Power Design provides a balanced mix of theoretical knowledge and practical insights, helping you explore the potential of wireless energy transfer and harvesting technologies. The book presents a series of hands-on projects that cover various aspects of wireless power systems, each accompanied by detailed explanations and parameter listings.

The following five projects guide you through key areas of wireless power: > Project 1: Wireless Powering of Advanced IoT Devices > Project 2: Wireless Powered Devices on the Frontline: The Future and Challenges > Project 3: Wireless Powering of Devices Using Inductive Technology > Project 4: Wireless Power Transmission for IoT Devices > Project 5: Charging Robot Crawler Inside the Pipeline

Dr. Mohamed Zied Chaari holds a BSc in Electronic Engineering, an MSc in Electronics Telecommunications, and a PhD in Wireless Power Transmission. He is the author of three technical books and more than 90 articles on wireless power harvesting, IoT, and related fields. A chartered electrical engineer and Senior Member of the Institute of Electrical and Electronics Engineers (IEEE), Dr. Chaari has also reviewed numerous manuscripts for IEEE, MDPI journals, and Springer.

These projects explore different aspects of wireless power, from inductive charging to wireless energy transmission, offering practical solutions for real-world applications. The book includes projects that use simulation tools like CST Microwave Studio and Keysight ADS for design and analysis, with a focus on practical design considerations and real-world implementation techniques.

Elektor International Media www.elektor.com

Wireless Power Design • Mohamed Zied Chaari

From Theory to Practical Applications in Wireless Energy Transfer and Harvesting

Wireless Power Design From Theory to Practical Applications in Wireless Energy Transfer and Harvesting

Academy Pro Title by

Mohamed Zied Chaari

Wireless Power Design

From Theory to Practical Applications in Wireless Energy Transfer and Harvesting

● Mohamed Zied Chaari

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● This is an Elektor Publication. Elektor is the media brand of Elektor International Media B.V.

PO Box 11, NL-6114-ZG Susteren, The Netherlands Phone: +31 46 4389444

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They do not assume, or hereby disclaim, any liability to any party for any loss or damage caused by errors or omissions in this book, whether such errors or omissions result from negligence, accident, or any other cause.

The author expresses his sincere gratitude to Arrow Electronics and Trenz Electronic for granting permission to include various tables, figures, and program codes in this book.

● ISBN ​978-3-89576-668-8 Print ISBN 978-3-89576-669-5

eBook

● © Copyright 2025 Elektor International Media www.elektor.com

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Contents

Contents General Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Section 1: An Overview of Wireless Power Technology and Its History . . . . . . . . . 11 Chapter 1 • Early History of Wireless Transmission of Electrical Energy . . . . . . . . 12 1.1 Heinrich Hertz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.2 Nikola Tesla . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.3 William Brown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Chapter 2 • Microwave Technology Based on Wireless Power Transfer . . . . . . . . . 14 2.1 The Microwave Station . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.2 Antennas for Microwave Energy Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.3 The Rectenna (Rectifying Antenna) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.4 Cyclotron Wave Rectifier (CWC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Chapter 3 • Wireless Power Transfer-Based Electromagnetic Induction Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Chapter 4 • Industry Applications of WPT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 4.1 Ground-to-Ground Microwave Transmission . . . . . . . . . . . . . . . . . . . . . . . . 23 4.2 Wireless Charging of an Electric Vehicle (Inductive Solution) . . . . . . . . . . . . . . . . 24 4.3 Drone Wireless Power Charging (Inductive Solution) . . . . . . . . . . . . . . . . . . . . . . 25 4.4 Wireless Charging Mobile Phone (Inductive Solution) . . . . . . . . . . . . . . . . . . . . . 25 4.5 Laser Wireless Power Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 4.6 Ultrasonic Wireless Power Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Chapter 5 • Concerns Regarding Safety and Security . . . . . . . . . . . . . . . . . . . . . . . 29 5.1 Beam Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 5.2 Frequency Allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 5.3 WPT and Sustainability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 5.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Section 2: Investigation and Construction of Microwave Transmitter Sources . . . 31 Chapter 6 • Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Chapter 7 • Microwave Transmitter Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 7.1 Gyrotron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 7.2 Klystron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

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7.3. Magnetron Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 7.3.1 The operating frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 7.3.2 Operation of magnetrons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 7.3.3 Effect of the Magnetic Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 7.3.4 Magnetron power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 7.3.5 Description of the operating sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 7.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Section 3: Rectenna and Energy Harvesting Circuit . . . . . . . . . . . . . . . . . . . . . . . . 42 Chapter 8 • Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Chapter 9 • Conventional Rectenna (Rectifying Antenna) . . . . . . . . . . . . . . . . . . . 44 9.1 Matching Circuit Designs Using an Advanced Design System (ADS) . . . . . . . . . . . 44 9.2 The Diode Choice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 9.3 Diode Model Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 9.4. Linear Equivalent Circuit of the HSMS 2820 Schottky Diode . . . . . . . . . . . . . . . . 49 9.5 Voltage Multiplication Circuit Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 9.6 Simulation of Multiplication Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 9.7 Storage Element for WPT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 9.8 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Section 4: Five Wireless Power Harvesting Circuits . . . . . . . . . . . . . . . . . . . . . . . . 58 Chapter 10 • Project 1: Wireless Powering of Advanced IoT Devices . . . . . . . . . . 59 10.1 Objective of This Project: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 10.2 Transmitter Antenna Fabrication, Experimental and Simulation . . . . . . . . . . . . . 59 10.3 Harvesting Antenna Fabrication, Experimental Measurements, and Simulation Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 Twin Antenna Without an Inset-Fed Patch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 10.4.1 Directivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 10.4.2 Reflection coefficient of the antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 10.4.3 3D radiation pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 10.4.4 Current distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 10.4.5 Smith plot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 10.5 Twin Inset-Fed Patch Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 10.5.1 Directivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

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10.5.2 The reflection coefficient of the antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 10.5.3 Radiation pattern 3D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 10.5.4 Current distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 10.5.5 Smith plot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 10.6 Power Budget . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 10.7. Rectifier Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 10.7.1 Single-stage voltage double RF energy harvesting circuit . . . . . . . . . . . . . . . . 79 10.7.2. RF harvesting circuit design uses a bridge rectifier . . . . . . . . . . . . . . . . . . . . 80 10.7 Prototype result and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 10.9. Conclusion: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Chapter 11 • Project 2: Wireless Powered Devices on the Frontline: The Future and Challenges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 11.1 Objective of This Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 11.2 Soldier and Battery in the Battlefield . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 11.3 Power Budget . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 11.4 RF Microwave Transmitter System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 11.5 Power Harvesting Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 11.5.1 Rectangular Patch Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 11.5.2 Rectifier Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 11.6 Prototype Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 11.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 Chapter 12 • Project 3: Wireless Powering of Devices Using Inductive Technology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 12.1 Objective of This Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 12.2 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 12.3 Design Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 12.4 Transmission Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 12.4.1 Frequency oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 12.4.4 Switched mode power amplifier circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 12.5 Receiver Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 12.6 Test System and Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 12.7 Discussion and Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

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12.8 Warming a Coffee Mug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 12.9 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 Chapter 13 • Project 4: Wireless Power Transmission for IoT Devices . . . . . . . . 116 13.1 Objective of This Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 13.2 The Impact of WPT on IoT or 4.0 Technologies . . . . . . . . . . . . . . . . . . . . . . . . 116 13.3 Design of the Harvester Coil Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 13.4 Dimension of the Receiver Coil Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 13.4.1 Simulation and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 13.4.2 Directivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 13.4.3 Reflection coefficient of the antenna: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 13.4.4 VSWR plot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 0 13.4.5 Radiation pattern 3D . . . . . . . . . . . . . . . . . . . . . . . . . . .

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13.4.6 Current distribution: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 13.5 Energy Harvester Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 13.6 Prototype Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 13.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Chapter 14 • Project 5: Charging Robot Crawler Inside the Pipeline . . . . . . . . . . 129 14.1 Objective of This Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 14.2 Pipeline Inspection System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 14.2.1 X-ray radiography inspections of pipelines . . . . . . . . . . . . . . . . . . . . . . . . . . 129 14.2.2 Pipe robot crawler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 14.2.3 Robot crawler problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 14.3 Pipeline as a Transmission Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 14.4 Study and design of the Tx and Rx conical horn antenna . . . . . . . . . . . . . . . . . . 140 14.4.1 Simulation and results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 14.4.2 S-Parameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 14.4.3 Current distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 14.5 Construction setup of Rx and Tx antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 14.6 Rectifier Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 14.6.1 A multistage voltage multiplier design rectenna . . . . . . . . . . . . . . . . . . . . . . . 145 14.6.2 Assembly system of a rectifier circuit (receiver) . . . . . . . . . . . . . . . . . . . . . . . 148 14.7 Testing and Measurements Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

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14.8 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 Chapter 15 • Conclusion and Final Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155

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General Introduction A survey by Fortune Business Insights projects the size of the wireless power transmission market to rise from $15 billion in 2024 to $38 billion by 2032. Many studies expect the wireless power transmission market to develop at a compound annual growth rate (CAGR) of approximately 13% between 2024 and 2032. Wireless power transmission comprises a transmitter, a traveling wave, and a receiver. Numerous applications must send electricity wirelessly over distances varying from several centimeters in typical scenarios to hundreds of meters in advanced applications. Wireless energy transfer transmits electrical power without the use of any physical medium. The method facilitates the delivery of energy to inaccessible regions. The technique conveys microwave energy either via directed waves or through the atmosphere. Microwave radiation is captured and transformed into direct current (DC) using a large-area antenna, facilitating substantial radiated power and satisfactory gain. An additional technique primarily employed in recent years is energy transfer through induction. This technique is particularly effective for short distances, and the challenge is the alignment of the coils. Numerous implantable medical devices and sensors, including implantable optogenetic devices, bio-impedance sensors, and cardiac devices, can be charged and powered using wireless power transfer. Multiple techniques and solutions exist for energy transfer, including laser, mechanical vibrations, and ultrasonic methods, which we shall briefly present. Recently, wireless energy power systems have become more environmentally friendly. Numerous research emphasizes this technology as a sustainable solution.

This book delineates the various elements of wireless energy transfer and discusses five projects that provide wireless power to charge batteries and devices over considerable distances in civilian and military applications.

The book is segmented into five sections: Section I provides a comprehensive introduction to wireless power technology and its historical development.

Section II examines the microwave transmitter and demonstrates the applicability of an RF source for transferring microwave energy.

Section III focuses on the study and design of RF-DC conversion circuits, analyzing how microwave energy is converted into high-efficiency direct current (DC).

Section IV presents five wireless power harvesting projects, exploring various concepts and solutions for wireless powering devices.

Section V, Conclusion and final remarks.

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Section 1: An Overview of Wireless Power Technology and Its History

Section 1: An Overview of Wireless Power Technology and Its History

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Chapter 1 • E arly History of Wireless Transmission of Electrical Energy This section will examine wireless energy transfer technologies that have existed since the 1890s. Three principal ideas by Heinrich Hertz, Nikola Tesla, and William Brown encapsulate the initial history of wireless electrical energy transmission.

1.1 Heinrich Hertz Heinrich Hertz, a renowned German physicist, demonstrated that wireless delivery of electricity was possible. Hertz conducted remarkable experiments in 1887 to test Maxwell’s proposition. Each oscillator included polished copper coils linked to an induction coil, with a minute gap allowing sparks to arc between them. Hertz proposed that each series of sparks would emit electromagnetic waves if Maxwell’s predictions were correct. Hertz constructed a basic receiver with a wire loop to validate this. A narrow interval distinguished two knobs at either extremity of the loop. The receiver and the oscillator source established a distance of several meters. Hertz laid the groundwork for wireless communication and power transmission.

1.2 Nikola Tesla Nikola Tesla was born in the former Yugoslavia at midnight on July 9, 1856. He initially proposed and demonstrated wireless transmission of electrical energy as an alternative method for power distribution. In 1899, Tesla showed that the first practical phosphorescent lamps were illuminated twenty-five miles from their power source without cables. One of these concepts was the wireless transmission of energy. He could illuminate 200 bulbs 26 miles from his laboratory during this experiment.

Figure 1. Tesla tower concept Figure 1 illustrates Tesla’s Tower, which was primarily engineered for the wireless transmission of electrical energy rather than for telegraphy transfer. Tesla’s research concentrated on longer wavelengths, whereas Hertz performed tests utilizing radio waves for power transmission.

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Chapter 1 • Early History of Wireless Transmission of Electrical Energy

1.3 William Brown After the progression of microwave tubes in World War II, William initiated his research and development of wireless energy transfer in 1960. He developed a rectifying antenna (rectenna) to convert microwave radiation into direct current (DC). In 1963, he created the first rectifying antennas, achieving a high efficiency of around 50%. His conversion circuit enabled microwave power transmission from tethered to aerial helicopters. Brown and his team accomplished a similar microwave power transmission at the Venus Site in Goldstone, California. The rectifying antenna array, spanning 3.4 meters by 7.2 meters, was 1600 meters from the transmitting parabolic antenna. Figure 2 explains the basis and the concept of the initial and most comprehensive WPT (Wireless Power Transfer) test in 1975.

Figure 2. The concept of the first and most extensive WPT test in 1975

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Wireless Power Design

Chapter 2 • Microwave Technology Based on Wireless Power Transfer Microwave energy transfer received considerable attention almost a decade after its invention during World War II. In 1958, researchers initiated studies on wireless energy transfer for solar-powered satellites, supported by funding from Raytheon, NASA, and the US Air Force. Since 1980, all sponsors have investigated microwave energy transfer, with NASA as the primary sponsor.

Diverse techniques for wireless energy transmission have been established, encompassing Radio Frequency (RF), electromagnetic induction, ultrasonic-guided waves, and laser beams. The most advanced method for energy transfer is wireless transmission using radio frequencies. The microwave power transmission system is a technique that conveys energy to almost inaccessible locations. Maintaining the self-sufficiency of Internet of Things (IoT) devices necessitates a harvesting circuit for power storage. Figure 3 illustrates the considerable variability of wireless power methods, influenced by numerous characteristics such as frequency, distance between transmitter and receiver, and specific applications. Electric vehicles, drones, consumer electronics, and wearable electronics can all employ WPT for near-field applications, namely MC-WPT (Magnetic Coupling Wireless Power Transfer) and EC-WPT (Electric-Field Coupling Wireless Power Transfer). Far-field applications encompass advanced technologies and military uses, such as MPT (Microwave Power Transmission) and LPT (Laser Power Transmission).

Figure 3. Different types and ranges of wireless power transmission Figure 4. displays the block diagram of the wireless power transmission system.

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Chapter 2 • Microwave Technology Based on Wireless Power Transfer

Figure 4. The block diagram of a wireless energy system The wireless energy transmission structure consists of three parts: • Microwave energy source, • Traveling wave area, • Rectenna (Rectifying Antenna) or Cyclotron wave rectifier (CWC).

The necessity for a restricted distance between coils hinders the advancement of electromagnetic induction technology. Currently, four modalities of wireless energy transmission are employed. We enumerate four categories of electromagnetic radiation in ascending order of frequency: • Microwaves (Long-range distance), • Lasers (long-range distance), • Electromagnetic induction (Short-range distance), • Ultrasonic waves (Short-range distance).

Wireless power transfer technology can be divided into electromagnetic-based WPT technology and mechanical-based WPT technology according to indirect energy, as shown in Figure 5. Electromagnetic-based WPT technology can be classified into the magnetic field principle, electric field-principle WPT, microwave-principle WPT, and laser-principle WPT. Mechanical-based WPT technology can be classified into ultrasonic-principle WPT and mechanical vibration-principle WPT. The WPT technologies in aviation include inductive wireless power transfer, magnetic coupling resonant, laser, and microwave wireless power transfer. Inductive and conventional cognitive radios are classified as near-field WPT technologies, and laser and microwave are far-field WPT technologies.

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Wireless Power Design

Figure 5. Classification of wireless power transfer technologies Energy harvesting, a crucial component of wireless power transmission, is an innovative technology that delivers electricity to historically unreachable locations. This method, known as RF harvesting, is especially significant for its ability to energize electronic devices with minimal power requirements in remote and complex settings. It is also referred to as radio frequency harvesting. It can wirelessly energize electronic gadgets with minimal power usage. Researchers have recently attracted significant interest because they can wirelessly charge sensors in complex environments. Much research has examined wireless power charging by RF energy harvesting. The fundamental principle of this technology is to capture the RF energy surrounding the antenna or receiver to energize sensors.

Consequently, the IoT sensors must possess battery-free power supply methods. In the future, substantial resources will be required to sustain IoT devices due to the prevalence of numerous sensors in wireless sensor networks. Consequently, each sensor must be battery-free to ensure maintenance-free operation. Wireless power transfer, or RF energy harvesting, is a promising technique because it can supply power to IoT devices over greater distances than alternative methods, as illustrated in Figure 6.

Numerous distinguished researchers have advanced RF energy harvesting through various approaches and strategies. Chang-Yeob Chu et al. investigated system design for electric car charging, considering a broad spectrum of coupling coefficient variations due to coil misalignment. Koichiro Ishibashi and colleagues proposed the radio frequency characteristics of rectifying devices for ambient energy harvesting. Mohamed Zied et al. examined the influence of wireless power transmission on the future of warfare globally and its implications for ranking nations by military might. The investigation considered two factors: the impact of the microwave power sources and the effect of the distance on the attenuation. They investigated establishing energized IoT sensors through RF energy recovery. Mohamed Zied et al. concluded that all parameters efficiently supply energy to

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wirelessly power 5 W LED bulbs at distances exceeding five meters. Nermeen A. Eltresy et al. studied a CPIFA antenna to harvest the RF energy at three different frequency bands: GSM 900, GSM 1800, and Wi-Fi 2400. According to their analysis, the aim of designing a matching circuit is to match the proposed antenna with a rectifier to get maximum power transfer and minimum loss. They successfully harvested an output of 624 mV at 0 dBm input power. Diffa Pinto et al. evaluated the performance and established a relationship between process parameters to harvest energy and the number of rectifier circuits. They developed a framework for a Wi-Fi energy harvesting system based on the 7-stage Villard rectifier voltage multiplier circuit, which was analyzed and simulated using Agilent Design Systems (ADS). The output of the multiplier circuit is given to the power management unit circuit (PMU). With the increase in applications related to smart home communication, the Internet of Things (IoT), intelligent health care, and environmental monitoring, the demand for low-power electronic devices has increased significantly.

Figure 6. Typical block diagrams of the powering IoT devices wirelessly This solution ensures two essential components for IoT in smart homes: a reliable electrical supply for the wireless charging of electronic device batteries and ongoing self-energization of any IoT sensor utilizing RF energy, employing signals such as Wi-Fi, 4G, WiMax, 5G, or any ambient radiofrequency. This technology can power numerous electrical devices using IoT’s integrated and stationary harvesting systems. This aspect illustrates the effectiveness of wireless power harvesting in smart cities, enhancing intelligence and safety in daily life.

Figure 7 demonstrates that the rectifier circuit efficiently converts the received RF energy through Schottky diodes, a power management circuit, and a low-pass filter, all directly connected to the IoT device.

Figure 7. Block diagram to energize IoT devices through RF wireless power transfer.

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Wireless Power Design

2.1 The Microwave Station An RF transmitter or microwave station’s fundamental necessity is its ability to effectively convert AC power into microwave energy and emit that power in a regulated environment with low attenuation and high efficiency. A wireless energy transmission system must effectively transmit adequate RF energy from an antenna to devices. The receiving end must focus much power on attaining this capacity rather than scattering it omnidirectionally.

Table 1 presents the assessment of RF devices.

Max output

The most common

Directional antennas

Found (W)

frequency (MHz)

available

CB Radio

4

26

No

GSM class II

8

900

Yes

GSM class III

5

900

Yes

GSM class III

4

1800

Yes

Marine radio

25

156

No

FRS/GRMS Radio

5

465

No

Trucking radio

15

800

Yes

Wireless access point

0.2

2400

Yes

Wireless bridge

2

2400

Yes

Audio/video transmitter

2

2400

Yes

Device

Table 1. Evaluation of RF devices After assessing the devices shown in Table 1, a trucking radio most efficiently meets the requirements for a transmitter in wireless power transfer or energy harvesting technology.

2.2 Antennas for Microwave Energy Transmission A microwave power transmission apparatus may utilize several antenna types, including horn antennas, parabolic reflectors, patch antennas, Yagi-Uda antennas, phased array antennas, and cross-rhombic antennas.

2.3 The Rectenna (Rectifying Antenna) For many types of wireless power transmission (WPT) systems, the diode-type rectenna is the best (and the simplest) device for back-conversion of microwaves into D.C. Diode-type rectennas have played and play a fundamental role at the stage of principal demonstration of the possibilities of highly efficient wireless power transmission by microwaves. Rectenna technology has seen significant advancements over the years, primarily driven by the need for efficient wireless power transmission and energy harvesting solutions. Early research focused on basic rectenna designs for capturing solar energy in space and transferring it to the Earth’s surface utilizing microwave radiation. Recent developments, however, have extended to terrestrial applications, including powering RFID tags, charging batteries, and supplying power to remote sensors and IoT devices. The rectifying antenna (Rectenna) is the only part of the wireless microwave transmission. McSpadden conceived this and

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Chapter 2 • Microwave Technology Based on Wireless Power Transfer

defined a rectenna as consisting of the parts shown in Figure 8. Usually, a large parabolic antenna is selected as a fixed target of the MPT system because it can capture and collect the maximum amount of energy. It is considered that the receiving antenna is part of the rectifying antenna (Rectenna).

Figure 8. McSpadden’s (1998) rectenna (rectifying antenna)

2.4 Cyclotron Wave Rectifier (CWC) Therefore, we investigate an alternative device that alleviates several principal drawbacks of rectennas, including inadequate output voltage requiring the series arrangement of diodes and a heightened risk of degradation: the potential for danger persists even at modest levels of microwave or direct current overloads and insufficient power output from individual rectenna elements. Perspectives on the Cyclotron Wave Converter (CWC) for converting microwaves into direct current (DC). Nevertheless, its appeal has diminished for prospective high-power industrial wireless power transfer systems. Industrial energy systems consistently require and utilize high-power and high-voltage apparatus to minimize losses and enhance reliability. This section addresses an alternative device that mitigates the principal detrimental characteristics of diode-type rectennas: • The low power level of a single rectenna element • Low output voltage and therefore the necessity to connect diodes in series • The possibility of high breakdown, which is dangerous even at relatively small levels of microwave or DC overloads Microwaves at any frequency generate a transverse electric field within the coupler gap of the resonant cavity. The resonator is placed within the external magnetic field.

Consequently, the electron beam, generated by an electron gun and introduced into the resonator, acquires cyclotron rotation at a specific frequency, which excites a rapid cyclotron wave of the electron beam. The conversion zone follows the resonant cavity, where the external magnetic field alters direction and magnitude. Figure 9 illustrates the principle of CWC developed by Istok Corp.

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Wireless Power Design

Figure 9. Scheme of Cyclotron Wave Converter

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Index

Index A Alternating current (AC) Advanced Design System ATmega328P Antenna Magus B Bandwidth Battery

21, 109 44 39, 106 140

94 95

C Cyclotron Wave Rectifier (CWC) 15, 19 Compound annual growth rate (CAGR) 23 Cockcroft-Walton voltage multiplier 52 Coupled mode theory (CMT) 104 D DC/DC converter Dickson charge pump Direct current (DC) E Electric vehicle, 24 EMROD

46 51 13, 43, 95, 109

24, 25, 26 96

J Jammer

87

K Klystron

32

L LPT (Laser power transmission) 14, 26, 27 M Magnetrons Microwave technology MPT (Microwave power transmission) Micro-harvester circuit Multi-micro harvester circuit

33 14 116 121 128

P Power management unit circuit (PMU) 17 Pipe robot crawler 130 Pipeline 129

23

F Federal Communications Commission (FCC) Free-space path loss

29 91

G Gyrotron Gyro-klystrons Gyro-traveling wave tubes Gyro-twisting

32 33 33 33

H HSMS 2820 Harvester coil antenna

49 117

I Internet of Things (IoT)

Inductive solution ISM band

R Radio frequency (RF) Receiver circuit Rectenna (Rectifying Antenna) Reverse leakage current

14, 29 108 18 48

S Strongly Coupled Magnetic Resonance (SCMR) 21 Schottky diode 44, 82, 98, 121 SMS 7621 45 SMS 7630 45, 78 Smith chart 55 Supercapacitor 56 T TRIAC

39

14, 59, 116

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Wireless Power Design

V Voltage multiplier circuit

55

W William Brown 13 WPT (Wireless Power Transfer) 13, 23, 29, 56, 104, 116 Wireless power harvesting (WPH)

59

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Wireless Power Design Wireless power transmission has gained significant global interest, particularly with the rise of electric vehicles and the Internet of Things (IoT).

It’s a technology that allows the transfer of electricity without physical connections, offering solutions for everything from powering small devices over short distances to long-range energy transmission for more complex systems.

Wireless Power Design provides a balanced mix of theoretical knowledge and practical insights, helping you explore the potential of wireless energy transfer and harvesting technologies. The book presents a series of hands-on projects that cover various aspects of wireless power systems, each accompanied by detailed explanations and parameter listings.

The following five projects guide you through key areas of wireless power: > Project 1: Wireless Powering of Advanced IoT Devices > Project 2: Wireless Powered Devices on the Frontline: The Future and Challenges > Project 3: Wireless Powering of Devices Using Inductive Technology > Project 4: Wireless Power Transmission for IoT Devices > Project 5: Charging Robot Crawler Inside the Pipeline

Dr. Mohamed Zied Chaari holds a BSc in Electronic Engineering, an MSc in Electronics Telecommunications, and a PhD in Wireless Power Transmission. He is the author of three technical books and more than 90 articles on wireless power harvesting, IoT, and related fields. A chartered electrical engineer and Senior Member of the Institute of Electrical and Electronics Engineers (IEEE), Dr. Chaari has also reviewed numerous manuscripts for IEEE, MDPI journals, and Springer.

These projects explore different aspects of wireless power, from inductive charging to wireless energy transmission, offering practical solutions for real-world applications. The book includes projects that use simulation tools like CST Microwave Studio and Keysight ADS for design and analysis, with a focus on practical design considerations and real-world implementation techniques.

Elektor International Media www.elektor.com

Wireless Power Design • Mohamed Zied Chaari

From Theory to Practical Applications in Wireless Energy Transfer and Harvesting

Wireless Power Design From Theory to Practical Applications in Wireless Energy Transfer and Harvesting

Academy Pro Title by

Mohamed Zied Chaari