Design of high temperature superconducting contiguous-band diplexer

A high temperature superconducting (HTS) contiguous-band diplexer was designed and fabricated. The HTS contiguous-band diplexer was made using 2-inch-diameter LaA1O₃ wafers coated with epitaxial thin film YBO on both sides, and was made up of two 4-pole singly-terminated low-pass prototype bandpass channel filters connected in parallel. Its operation frequency was centered at 3.25GHz and 3.75GHz with 500-MHz-wide channels. The HTS diplexer operated at 77 K shows excellent performance. The insertion loss in the pass-band is less than 0.8 dB and the rejection between per channel is greater than 30dB. In comparison with the conventional diplexer, the HTS diplexer offers more than 2dB improvement in insertion loss performance and 3/4 volume reduction. This design concept can be applied to the design of HTS multiplexer and the future HTS ESM channeliser systems.