Narrowband superconducting filters for mobile communication

Abstract

Supcrconducting planar filters exhibit higher selectivity, bigger out-of-band rejection and smaller interference between adjacent channels than metallic planar filters. Using ideas of a modified hairpin, the Chebyshev approximation and cross coupling between non-adjacent resonators, we have designed two HTS filters utilising YBa2CU307-6 thin films on a 58mmx 14mmxO.3mrn LaAlO3 substrate. A 12-pole superconducting bandpass filter for centre frequency of 1.84 GHz and bandwidth of 5 MHz exhibits simulated passband insertion loss of 0.1 dB and the out-of-band rejection of 50 dB at I MHz from the passband. A HTS bandstop filter was designed using the same type of the resonator as the bandpass filter to obtain 50 dB attenuation for the frequency from 1.621 GHz to 1.625 GRz (Iridium satellite).