PROPERTIES OF SUPERCONDUCTIVE BANDPASS-FILTERS WITH THERMAL SWITCHES

This letter reports experimental results on frequency tuning and switc hing in superconductive bandpass filters with thermal switches. The fo ur-pole microstrip filters with frequency of 1.5 GHz and bandwidth of 1.5% were fabricated using Nb or EuBaCuO films. The addition of therma l switches around conductors did not affect the filter characteristics . A negative frequency shift of - 2 MHz was confirmed at 8 K in the Nb filter with loss of less than 0.7 dB. In contrast, a positive shift o f + 5 MHz was observed at 77 K in the EuBaCuO filter. Furthermore, swi tching with a large difference of approximately 50 dB in loss was achi eved in the Nb filters.