Cross-coupled narrow-band filter for the frequency range of 2.1 GHz using YBCO resonators with artificial magnetic pinning lattices

Narrow-band microstrip cross-coupled band-pass filters based on the quadruplet geometry are designed for wireless-communication applications. We have fabricated the high-T/sub c/ superconducting filters by pattering YBa/sub 2/Cu/sub 3/O/sub y/ (YBCO) films deposited on LaAlO/sub 3/ substrates. The flux pinning in YBCO resonators is increased with an artificial magnetic lattice of Nd/sub 0.2/Sr/sub 0.8/MnO/sub 3/ (NSMO) pinning dots. The 4-pole 15-mm-square filter has a pair of transmission zeros near the pass-band edge, a 2.18-GHz center frequency with a 9.8-MHz bandwidth and a 1.48-dB minimum insertion loss at 77 K. The results are discussed and compared with that of an identical YBCO filter without NSMO pinning dots. The influences of the flux pinning on filter performance are discussed.