Power-handling Capability of Transmit Filters Using Superconducting Bulk Ring Resonators

The power-handling capability and frequency responses of superconducting bandpass filters (BPFs) at a center frequency around 5 GHz with a 100-MHz bandwidth were investigated for application to transmit filters. A 3-pole BPF was designed using a Chebyshev function with three pairs of the bulk ring resonators and the dielectric trimming rods with the same dimensions. Using this design, we simulated the frequency responses of the filter with low loss and passband ripple, and by adjusting positions of trimming rods a fine tuning of the filter responses was achieved. The BPF was fabricated using ring resonators made from a DyBa₂Cu₃O_y superconducting bulk and a pair of Al₂O₃ substrates in a Cu cavity with trimming mechanisms using dielectric rods. The filtering property with low insertion loss was clearly observed at 25 K. Power-handling capability of the 3-pole BPF of over 10 W (40 dBm) was observed.