Investigation of coaxial cable properties for HTS filters

To decrease thermal leakage in coaxial cables, we have developed a novel coaxial cable for HTS filters. We call it the "thin outer conductor coaxial cable". The outer conductor of this new cable was made of copper film and was designed to have an optimum thickness of 0.005 mm by the simulation and experimentation of thermal and electrical performance. Coaxial cables that are 1.68 mm in diameter and 90 mm in length have an insertion loss of 0.17 dB at 2.0 GHz. Impedance analysis of the connector joint was evaluated with TDR, and we obtained results for detailed explanations of breakdown in electrical performance. The coaxial cable was tested for low temperature properties and underwent the heat cycle test; however, performance deterioration could not be found.