Thermally-Induced Currents in Coaxial Signal Cables

Polymer insulated coaxial signal cable can produce thermally induced signals in service, known as pyroelectnc response. The source of such pyroelectric signals was studied extensively over a wide range of cables with various dielectrics, including one inorganic material. Our results indicate that the pyroelectric response of polymer-insulated coaxial signal cables under standardized conditions can vary by several orders of magnitude with variation in cable structure and dielectrics. Such pyroelectric signals are generated by rapid inhomogeneous thermal expansion of the cable dielectrics in conjunction with polarization (space charge and/or dipolar polarization) in one or more cable insulation layers. The variation of the magnitude of pyroelectric signal with cable structure and dielectric is explained based on the physical properties of cable dielectrics and on the variation of manufacturing processes. This study provides a basis for qualitative prediction of pyroelectric error signals from coaxial signal cables in service, as well as a basis for predicting pyroelectric response during cable design.