Superconducting filters for wireless communication applications

In this paper we summarize recent results in a development of narrow-band HTS bandpass filters on sapphire substrate for future wireless communications systems. The filters are designed to have 5 or 10 MHz pass band in the UMTS base stations receive band. The filters exhibit quasi-elliptic function response for higher selectivity with a reduced number of resonators. They are implemented with either a cascaded-quadruplet (CQ) or a cascaded-quadruplet-triplet (CQT) coupling structure. The filters were fabricated on 0.43 mm-thick sapphire wafers with double-sided YBCO films. Measured results of the filters are presented, showing excellent performance.