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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.
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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