Automation-orientated techniques for quality-factor measurement: of high-Tc superconducting resonators

It is a common technique to use resonators to determine the surface resistance of high-temperature superconductors through the measurements of unloaded Q₀ factor and resonant frequency. As the surface resistance may change very significantly between the normal and superconducting states, the quality factor may also have a large variation between the two states. It is thus desirable to develop measurement techniques to deal with the possible large variation in Q ₀ values. Six methods are proposed in the paper for both one- and two-port coupled resonators. These techniques are suitable for a network-analyser-based automated system used for the determination of surface resistance of superconductors. Example measurements using these techniques are also given