High-Q tunable YBCO disk resonator filters for transmitter combiners in radio base stations

Results on the development of a tunable HTS resonator structure for transmitter combiners of radio base stations are reported. The design goal was the minimization of the dissipative insertion loss of a one-pole filter with a 3-dB bandwidth of 630 kHz under the impediment of a required tunability of the center frequency between 1.93 and 1.99 GHz and a power handling capability for 10 W transmitted power. At 70 K the quality factor of the utilized disk resonator structure turned out to be limited to 10/sup 5/ due to dielectric losses in LaAlO/sub 3/ substrate, but in a lower temperature range where dielectric losses are no longer dominating, Q/sub 0//spl ap/290000 was obtained for the tunable version.