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Carlisle Interconnect Technologies UTiPHASE™ Cables for Applications Requiring Minimal or Linear Phase versus Temperature Change Deborah M. Dolan, RF Design Engineer, Carlisle Interconnect Technologies Inc.
Abstract--Carlisle Interconnect Technologies' has developed UTiPHASE™ a family of flexible coaxial microwave cables with a Fluoroplastic Foam Resin which flattens the phase versus temperature response curve. UTiPHASE™ cables are designed to be used in phase critical flexible cable applications where changes in the electrical phase length with temperature are undesirable.
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I. THE PROBLEM
icrowave cable assemblies have an electrical length that varies with temperature. Often it is advantageous for this length to vary minimally or linearly with temperature. The electrical length of the cable assembly is primarily dependent on the choice of the dielectric material. The dielectric of choice for many microwave cable applications is typically a form of Polytetrafluoroethylene (PTFE). While PTFE generally exhibits excellent electrical and mechanical properties, at around 19°C it experiences a structural phase change that results in dramatic dimensional changes which affect the electrical phase length of cable assemblies. Figure 1 depicts the typical phase versus temperature performance for flexible cables manufactured from ultra-low-density PTFE. This type of abrupt phase length versus temperature performance can pose challenges for system designers who require linear or minimal phase change with temperature.
II. THE DESIGN A. Design Approach The UTiPHASE™ series of flexible cable was developed utilizing a Fluoroplastic Foam Resin. The cables sizes were chosen to be consistent with current Carlisle Interconnect Technologies' flexible cable offerings to utilize existing proven connector options for assemblies. B. Materials Figure 2 depicts the typical UTiPHASE™ cable configuration which consists of a center conductor (1), a dielectric (2), an outer conductor (3), an outer shield (4) and an outer jacket (5).
Fig 2: Typical UTiPHASE™ Cable Construction
g 1: Typical Phase Change vs. Temperature for Cables ULTRA Low-Density PTFE Dielectric.
Fi with
The center conductor (1) types meet the requirements of MIL-DTL-17. The center conductors are either silver-plated copper (SPC) or silver-plated copper-weld steel (SPCW). The cables detailed herein have a Fluoroplastic Foam Resin dielectric (2). The outer conductor (3) is silver plated copper per ASTM B-298. The outer shields (4) are either silver plated copper per ASTM B-298 or ARACONâ (Silver plated poly-paraphenylene terephthalamide) for up to 15% weight savings. 12/18/19
2 The outer jacket (5) is either extruded fluorinated ethylene propylene (FEP) or ethylene tetrafluoroethylene (ETFE) in accordance with ASTM D-3159. Table I lists the center conductor materials, outer shield and outer jackets for the UTiPHASE™ cables discussed in this article.
Figure 3 shows the typical phase change for UTiPHASE™ cables versus flexible cables with ultra-low-density PTFE dielectric.
TABLE I UTIPHASE™ CENTER CONDUCTOR, OUTER SHIELD AND OUTER JACKET MATERIALS
UTiPHASE™ Part Number MCX088D UFP088D MCX142A UFP142A MCX205A UFP205A MCX311A UFP311A
Center Conductor Material SPCW SPCW SPC SPC SPC SPC SPC SPC
Outer Shield
Outer Jacket
ARACON SPC ARACON SPC ARACON SPC ARACON SPC
ETFE FEP ETFE FEP ETFE FEP ETFE FEP
C. Physical Dimensions
Fig 3: Typical Phase Change vs. Temperature for Flexible Microwave Cables
Direct comparison of the UTiPHASE™ product and cables manufactured with other dielectric materials reveals superior performance in maintaining electrical phase length. Figure 4 shows the typical phase change for UTiPHASE™ cables versus flexible cables with various PTFE dielectrics.
The physical dimensions of each cable size were selected to be consistent with Carlisle Interconnect Technologies' UTiFLEX™ flexible cable product line to enable using the same connectors. Table II lists the outer diameter and nominal weight for the UTiPHASE™ cables discussed in this article. TABLE II UTIPHASE™ OUTER DIAMETER NOMINAL WEIGHT
UTiPHASE™ Part Number MCX088D UFP088D MCX142A UFP142A MCX205A UFP205A MCX311A UFP311A
Outer Diameter (IN) 0.088 0.088 0.142 0.142 0.250 0.250 0.311 0.311
Nominal Weight (g/ft) 3.3 4.0 8.4 9.5 15.9 18.7 35.6 45.7
III. THE SOLUTION
Fig 4: Typical Phase Change vs. Temperature for Flexible Microwave Cables with Different Dielectrics
IV. CONCLUSION The UTiPHASE™ series of cable can be used wherever flexible cables are needed that exhibit minimal or linear phase change with temperature. UTiPHASE™ is a trademark of Carlisle Interconnect Technologies
Multiple lots of cable were tested for electrical length from 65°C to 100°C with startling results. The abrupt phase change and total change inherent in PTFE dielectrics was eliminated. .
12/18/19