Measurements of material and circuit properties using a microstrip ring-resonator circuit on zirconia at 77K

By using a thick-film microstrip ring-resonator circuit formed on a yttria-stabilised zirconia substrate and by measuring the frequencies of a number of resonant harmonics of the circuit, both at room temperature and when cooled with liquid nitrogen, material properties of the substrate such as the thermal expansion and dielectric constant, the dielectric constant of liquid nitrogen and the surface resistance of the conductor have been determined. This data is necessary for the accurate design of thick-film superconducting microwave circuits. Measurements have been carried out up to the 21st. harmonic of the resonator (0.5->10.4GHz) using both silver and YBa2Cu3Ox thick-film superconductor as the microstrip line and ground plane. This method has proved to be versatile and accurate, provided that a variety of factors are taken into account to enable an accurate analysis of the microstrip ring-resonator to be made. This paper presents a theoretical and experimental evaluation of the microstrip ring resonator.