Nonlinear response of Gd-Ba-Cu-O and Y-Ba-Cu-O microstrip resonators on sapphire

HF power-induced nonlinear effects, including the two-tone intermodulation distortion (IMD), were examined by using 2.3 GHz microstrip resonators prepared from double-sided YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) and GdBa/sub 2/Cu/sub 3/O/sub 7-x/ (GBCO) films on CeO/sub 2/ buffered sapphire. Both, the YBCO and the GBCO resonators exhibited similarly high performance with low IMD level. The third-order interception points varied linearly with temperature from P/sub TOI/~1500 W of the circulating power, P/sub circ/, at 4.2 K to P/sub TOI/~90 W at 77.4 K. The dependence of the IMD products on the P/sub circ//P/sub TOI/ ratio was found to be the same at all measurement temperatures. Similarly, the variation of the microwave surface resistance (delta)R/sub S/ versus P/sub circ//P/sub TOI/ was found to be temperatureindependent. The combination of these dependences provided a universal relation between the power of the IMD signals and (delta)R/sub S/, which was exhibited by both YBCO and GBCO resonators in the entire examined temperature range.