A 19-pole cellular bandpass filter using 75-mm-diameter high-temperature superconducting thin films

A 19-pole bandpass filter designed for the 900-MHz cellular communication band with 25-MHz bandwidth is reported using a compact forward-coupled approach in microstrip configuration. The filter was fabricated using 75-mm-diameter, double-side-coated YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO) high-temperature superconducting (HTS) thin films grown by a single-source MOCVD technique on a LaAlO/sub 3/ substrate. Measurement of the filter at 77 K showed a dissipation loss of 0.5 dB, corresponding to an average unloaded Q-factor of 10000 in 75-mm-diameter microstrip resonators. A minimum return loss of 15 dB was obtained from measurements at 77 K. >