<title>Characterization of high-Tc coplanar transmission lines and resonators</title>

Abstract

Coplanar transmission lines made from high-Tc superconducting thin films are investigated theoretically. A full wave analysis is performed for the coplanar waveguide structure by a partial wave synthesis. For modeling the superconducting behavior the two- fluids model and the London theory are applied. The authors use two ways of analysis. The first is to calculate the electromagnetic field for the structure assuming ideal conductors and to introduce the conductor losses afterwards by using the surface impedance matrix. The surface impedance matrix takes into consideration the coupling of the tangential magnetic fields on both surface planes of a thin superconducting film. Thus the thickness of the film may be in any range compared with the London penetration depth. This method is compared with the accurate solution obtained by calculating the electromagnetic field also within the conductor. Transmission line structures are analyzed. The behavior of measured and published coplanar waveguide (lambda) /2 resonators made of high-Tc superconducting thin films is discussed. Micrometer structures are considered in the frequency range up to 100 GHz. Such transmission line structures are of special interest for low loss, low dispersion chip-to-chip interconnections. The results obtained with superconductors are compared to the results obtained for the same geometry with normal conductors.