Evaluation of Passive Intermodulation Using Full-Wave Frequency-Domain Method With Nonlinear Circuit Model

Passive intermodulation (PIM) arising from metallic contact junctions on the reflector antenna may cause the degradation of a satellite communication system. A time-domain method such as time-domain physical optics (TD-PO) can solve the nonlinear problems of PIM; however, the error accumulation is unacceptable in the analysis of electrically large objects. The rigorous full-wave frequency-domain method of electrically large objects is not suitable because it only can be applied at single frequency. An equivalent circuit model coupled with full-wave frequency-domain method is proposed to solve the PIM problems of electrically large objects. The responses of the nonlinearities at metal-insulator-metal (MIM) contacts are analyzed by the circuit method; the electromagnetic field distribution is evaluated by the rigorous full-wave frequency-domain method. Finally, the analysis of PIM on a reflector antenna illuminated by a practical horn is performed to exemplify the usefulness of the method presented in this paper.