Passive Intermodulation Distortion in Connectors With Nonlinear Interaction in Electrical Contacts and Magnetic Materials

Nonlinearities in electrical contacts and magnetic materials are two main contributors to passive intermodulation (PIM). In this study, mechanisms of thermally induced current truncation and hysteresis effect are introduced to provide explanations for PIM generation and to make predictions for the third-order intermodulation (IM3) products resulting from coaxial connectors. Equivalent circuit models are presented to provide insight into the nonlinear sources both in contact junction and body area with the relative contribution of various physical parameters. The finite element analysis (FEA) model of the central conductor of a DIN-to-N coaxial adapter is developed to identify the current density and temperature distribution in the contact area, while an FEA model of simplified connector cross section is presented to simulate the magnetization effect in the body area. Combined with two nonlinear sources, an equivalent circuit model predicting the PIM behavior is developed. The simulation results show that the material nonlinearity contributes to frequency dependence, while the power dependence is dominated by both nonlinear mechanisms. Connectors with different contact surface are obtained by designed accelerated tests, and two types of connector with different materials are manufactured. Good agreements are observed in experimental measurements, verifying the proposed model of contact-material interaction-induced PIM.