Microwave multipole lowpass and bandpass filters fabricated by high-Tc superconducting thin films

摘要

The design, fabrication, and measurement of 7-pole microstrip lowpass filters and 4-pole parallel coupled-line bandpass filters using superconducting YBa2Cu3O7-x epitaxial thin films are presented. The YBa2Cu3O7-x films were grown in situ at 770°C and 200 mTorr oxygen partial pressure in a pulsed laser deposition system. The 7-pole microstrip-line lowpass filter and 4-pole parallel coupled-line bandpass filter patterned on the laser ablated YBCO films with dimension of 20 cm×10 cm×0.5 mmt were generated using photolithographic and wet etching processes. The complete devices packaged in a 3-component type brass test-fixture were characterized. The results showed the center frequency of 11.2 GHz with 6% bandwith and less than 1 dB insertion loss(IL) for the case of bandpass filters below 77 K.