  Microwave properties of High Temperature Superconductors (HTS) exhibit
dependence on RF power levels. Effects of nonlinear phenomena causing this
dependence can be modelled using lumped element circuits. Several RLC circuits
to model the surface impedance of HTS were investigated (with equations
expressing transmitted power derived) and assessed. Linear, quadratic and
exponential dependences of surface resistance RS and inductance LS on the RF
power for the model chosen as the best have been examined and used in
simulations of electromagnetic responses of superconducting films in a
Hakki-Coleman dielectric resonator.
