Hairpin-line/half-wave parallel-coupled-line narrowband bandpass filters using high temperature superconducting thin films

In this paper, hairpin-line and hybrid hairpin-line/half-wave parallel-coupled-line filters using High-Temperature Superconducting (HTS) thin films are proposed. The proposed structures provide more compact size than conventional parallel-coupled-line filters and hybrid hairpin-line filters reduce the spurious modes due to the surface waves in the hairpin-line filters. The designed filters using HTS have low loss, small size and narrow bandwidth characteristics with the minimum number of poles in comparison with the normal metal microstrip line filters. The 3 pole filters centered at 14.25 GHz with the bandwidth of less than 1% were designed and fabricated. These operating characteristics are simulated and fabricated using HTS and compared with the normal metal microstrip line filters.