High-T/sub c/-superconductor-sapphire microwave resonator with extremely high Q-values up to 90 K

A theoretical analysis was performed for an extremely high-Q resonator formed by a sapphire rod sandwiched by a pair of high-T/sub c/ superconductor (HTS) films. A number of these HTS-sapphire-HTS resonators at C-band and Ka-band were designed, fabricated, and tested. At 5.552 GHz, Q/sub 0/ reached 2*10/sup 6/ at 90 K, 3*10/sup 6/ at 80 K and 1.4*10/sup 7/ at 4.2 K with circulating power up to 500 kW. Formulas for calculating the resonant frequency and Q-value derived from the theoretical analysis were verified by experimental data with good agreement. Three different thin-film HTS materials-Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/, YBa/sub 2/Cu/sub 3/O/sub 7- delta / and Tl/sub 0.5/Pb/sub 0.5/Sr/sub 2/CaCu/sub 2/O/sub 7/-were tested. The sensitivity of the high Q-value and the parasitic coupling to the case modes are discussed. Applications such as frequency stabilized oscillators, filters, and HTS film characterization are described.<
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