HIGH T-C SUPERCONDUCTING CPW BANDSTOP FILTERS FOR RADIO ASTRONOMY FRONT-ENDS

We have designed and tested a superconducting coplanar waveguide (CPW) bandstop Alter consisting of 8 coupled line sections at a center freq uency of 1.53 GHz. A packaged 94.7% bandwidth low pass Chebychev desig n yielded a filter with a center frequency of 1.56 GHz, less than 1.2 dB insertion loss in the passband and better than 28 dB rejection at 2 0 Kelvin. With a skirt selectivity of 1.53 (=BW1 dB/BW-28 dB) and low insertion loss this filter is an excellent candidate for suppressing c ontiguous spurious signals in cooled low-noise receiving front ends.