1.5-GHZ BAND-PASS MICROSTRIP FILTERS FABRICATED USING EUBACUO SUPERCONDUCTING FILMS

This letter reports the properties of 1.5-GHz band-pass microstrip filters fabricated using EuBacuO superconducting films. Although 3- and 4-pole filters constructed using a superconductor and a silver ground plane exhibited good reproducibility and very low insertion loss of 3 approximately 5 dB at 70 K, in comparison with Cu filters with 16 approximately 27 dB loss at 77 K, the insertion loss was almost constant at temperatures below 70 K. In contrast, the insertion loss in the 4-pole filter with a superconductive ground plane was 1.2 dB at 70 K and 0.6 dB at 28 K. The center frequency and bandwidth at -3 dB were, respectively, 1.45 GHz and 1.4% at temperatures below 70 K.