YBaCuO disk resonator filters operating at high power

We have developed and successfully operated a compact tunable one-pole filter at 2 GHz for transmitter combiners in mobile radio base stations. The concept is based on edge-current free modes in circular symmetric resonators. Unloaded quality factors Q/sub 0/>5.10/sup 5/ were achieved with double-sided 2´´-diameter YBaCuO films on Czochralski-grown LaAlO/sub 3/. The dielectric loss tangent limited Q/sub 0/ around 60 K to values below 10/sup 5/. A circulating (transmitted) power of 800 kW (130 W), 700 kW (115 W) and 90 kW (15 W) could be handled in pulsed operation (pulse duration 10 ms, duty cycle 3%) at 23, 45 and 76 K, respectively, without measurable Q-degradation. These results approach the best microwave field performance measured so far with unpatterned films at 19 GHz. The power handling of the filter degraded in proportion to the duty cycle, indicating heating as the dominant limitation. The filter could be tuned by 3% by moving a plunger film by 36 /spl mu/m above the ring-shaped groundplane of the resonator. The CW power handling was not affected by the tuning, but the radiation losses and the maximum achievable power levels were degraded compared to the fixed-frequency filter.