Narrow-band YBCO superconducting parallel-coupled coplanar waveguide band-pass filters at 10 GHz

High-T/sub c/-superconducting coplanar-waveguide (CPW) three-pole, four-pole, and five-pole bandpass filters fabricated from in situ sputter-deposited YBa/sub 2/Cu/sub 3/O/sub 7-x/ thin-films on LaAlO/sub 3/ substrates with dimensions 10 mm*25 mm are presented. The design is based on the evaluation of CPW test chips integrating different resonators and transmission line structures. The measured data were fed into a CAD (computer-aided design) program using general transmission line elements instead of CPW elements. Both YBCO and gold versions were constructed and mounted in gold-plated brass test fixtures. At liquid nitrogen temperature (77 K), the filters were characterized by center frequencies at 10 GHz and bandwidths smaller than 1.3%. Total insertion loss and out-of-band rejection values of the complete packaged devices were better than 2.2 dB and 30 dB, respectively.<>