New Type of Microwave High-T_c Superconductor Microstrip Resonator and Its Application Prospects

A new type of planar high-Tc superconductor (HTS) resonator, proposed by the authors, is described. Its feature is excitement with whispering gallery modes (WGM) unlike the known microstrip resonators excited with the lower modes. The resonant structure of two-planar disks and two microstrip lines was simulated and made on the basis of a DyBa₂Cu₃O_7-δ superconductor epitaxial film of 600-nm thickness using photolithography technique. The film was deposited on MgO single crystal substrate of thickness h = 0.5 mm. Microwave response in a form of Q-factor and resonant frequency depending on temperature was measured in K-And Ka-bands. The obtained results show higher values of Q-factor of WGM microstrip HTS resonators in comparison with the known HTS microstrip resonators with lower modes. In the authors' opinion, these resonators open prospects for development of new planar microwave devices and techniques. The response of HTS disk resonators obtained earlier and about six months later at approximately the same conditions showed the lowering Q-factor, which may be explained by the degradation of HTS film properties and requires further study.