Physical Mechanisms of Passive Intermodulation: A Short Review

This paper describes the physical mechanisms of passive intermodulation generation, including nonlinearity in metal contacts and materials. The nonlinearity in metal contact considers the weakly nonlinear conduction mechanism under microscopic condition, surface roughness, mechanical stress and symmetry of contact interfaces. The nonlinearity in material considers the multiphysics coupling effects inside the transmission line, such as thermo-electricity coupling, nonlinear source scattering effects, and other structural factors. Finally, the future development direction is clarified according to the research trends.