HIGH-TC 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(c). superconductor (HTS) films. A number of these HTS-sapphire-HTS resonators in C-band and Ka-band were designed, fabricated and tested. At 5.552 GHz, Q(o) reached 2 x 10(6) at 90 K, 3 x 10(6) at 80 K and 1.4 x 10(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: Tl2Ba2CaCu2O8, YBa2Cu3O7-delta and Tl0.5Pb0.5Sr2CaCu2O7 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 characterization for HTS films are described.