Millimeter-Wave Ultra Wideband Multilayer Superconducting Filter

Ultra wideband (UWB) millimeter-wave filters are needed in the realization of analog front ends of superconductor digital receivers. In this paper, a multi-layer niobium-based superconducting bandpass filter operating over the frequency range 30-60 GHz is demonstrated for the first time. The filter is realized in a co-planar waveguide structure, where cross-overs in the multilayer structure are employed to reduce the filter size. The paper also illustrates how these cross-overs can be utilized to fine tune the filter performance. An 8-pole superconductor niobium-based filter with a size of 0.88 × 2.2 mm designed with a center frequency of 45 GHz and a bandwidth of 30 GHz has been developed, fabricated, and tested. The results demonstrate the feasibility of monolithically integrating UWB millimeter-wave filters with a superconductor receiver on single-chip.