The effect of superconducting ground plane on microwave characteristics ofunpatterned superconducting films in the mixed state

The microwave characteristics of a multilayer structure made of a type-II s uperconducting thin film and a dielectric substrate together with a superco nducting ground plane is studied theoretically by using the model of the se lf-consistent treatment of vortex dynamics. The dependence of reflection co efficient on the temperature and static magnetic field is reduced owing to the existence of the superconducting ground plane, especially at temperatur es near Te and at higher fields. Comparison of the interesting oscillation phenomenon in re associated effective surface resistance between the Meissn er state (b = 0) and mixed state (b not equal 0) is made, We find that the superconducting ground plane not only strongly narrows down the resonant pe ak shape but also enhances the peak height. Finally, a similar layered stru cture made of a superconducting thin film on a dielectric substrate shielde d by a buffer layer is also considered. We specifically demonstrate that th e buffer layer has essentially no substantial influence on microwave reflec tance, transmittance, and complex surface impedance. The role played by the buffer layer is in great contrast to that in a planar transmission line.