Study of effects of HTSC nonlinearity on current distribution over a microstrip line

The applications of high temperature superconducting (HTSC) microwave circuits are limited to low power levels. The surface resistance of HTSC materials increases significantly with the power. For some applications, such as the transmitters in the base station of wireless communication systems, we have to push the input power level high enough to meet practical requirements. It is necessary to investigate the nonlinear effects of HTSC planar microwave integrated circuits at these high power levels. In this paper, a HTSC microstrip transmission line is analysed to investigate the nonlinear effects on the current distribution due to high applied powers. The current density distribution and the power handling capability of the HTSC planar microstrip line are studied, and the conductor loss as a function of the applied power obtained. In this study, a new approach based on combination of the moment method (MoM) and harmonic balance (HB) technique is used for the analysis of high power nonlinearities in HTSC planar microwave circuits. The field interactions and fringe fields outside the superconductor are included in the MoM formulation by using appropriate Green´s functions, and the nonlinear analysis is carried out by the HB technique.