A Finite Difference Time Domain Method for Passive Intermodulation Analysis of Nonlinear Metal-Metal Contact

The passive intermodulation (PIM) has gradually become a serious electromagnetic interference in the high-power and high-sensitivity RF/microwave communication system with the existence of the nonlinear metal-to-metal (MM) contacts. This paper proposes a finite difference time domain (FDTD) method for PIM analysis of nonlinear MM contacts. There are two kinds of models, the power series model and the equivalent circuit model, to describe the nonlinear MM contacts. Then the FDTD method is applied to analyze the nonlinear models so that the nonlinear current through the MM contact can be determined. For the microwave transmission devices, the PIM power level can be obtained by fast Fourier transform of the nonlinear current. For the microwave radiation devices such as antennas, the nonlinear currents are taken as a new electromagnetic transmitting source, the far-field scattering and PIM power level can be obtained by the FDTD method. Finally, a comparison between the simulation and experimental results is illustrated to verify the validity of the proposed method.