YBaCuO disk resonator filters operating at high power

We have developed and successfully operated a compact tunable one-pole filt er at 2 GHz for transmitter combiners in mobile radio base stations. The co ncept is based on edge-current free modes in circular symmetric resonators. Unloaded quality factors Q(0)>5.10(5) were achieved with double-sided 2"-d iameter YBaCuO films on Czochralksi-grown LaAlO3. The dielectric loss tange nt limited Q(0) around 60K to values below 10(5). A circulating (transmitte d) power of 800kW (130W), 700kW (115W) and 90kW (15W) could be handled in p ulsed operation (pulse duration 10 ms, duty cycle 3%) at 23, 45 and 76K, re spectively, without measurable Q-degradation. These results approach the be st microwave field performance measured so far with unpatterned films at 19 GHz. The power handling of the filter degraded in proportion to the duty c ycle, indicating heating as the dominant limitation. The filter could be tu ned by 3% by moving a plunger film by 36 mu m above the ring-shaped groundp lane of the resonator. The CW power handling was not affected by the tuning , but the radiation losses and the maximum achievable power levels were deg raded compared to the fixed-frequency filter.