Numerical Analysis of Passive Intermodulation Arisen From Nonlinear Contacts in HPMW Devices

A novel field-circuit hybrid numerical method is proposed to analyze the passive intermodulation (PIM) caused by nonlinear contacts. In this hybrid numerical method, the electromagnetic field part is simulated by a self-developed time-domain finite integration theory. Meanwhile, the circuit part is modeled by a number of nonlinear lumped elements, which can introduce the nonlinear feature of nonlinear contacts. After solving a multiscale problem, the field part and the circuit part can couple with each other self-consistently via the generalized Ampere's equation. To verify the accuracy of the proposed method, a practical example is discussed. The results show that the frequencies of each PIM order can match analytical results very well. Moreover, the PIM levels calculated by the proposed numerical method have a very good agreement with the measured results.