A high-temperature superconducting diplexer for satellite communication applications

A C-band high temperature superconducting (HTS) diplexer is presented for the module of a multiplexer. The diplexer consists of a common node and two bandpass filters. The common node is designed by an open-loop microstrip line, which resonates at the frequency of 3995 MHz. Both channel filters consist of four rectangular spiral line resonators. The diplexer is fabricated by DyBa₂Cu₃O₇ (DBCO) thin films on MgO substrate with a dimension of 30 mm × 10 mm. Experiments are performed in a cryocooler at 77K. The measured insertion loss is less than 0.1 dB for two channels. The isolation between the two channels is about 50 dB. Good agreements are achieved between measurement and simulation.