Behavior Modeling of Cascading Passive Intermodulation in Coaxial Connectors with Nonlinear Transfer Function

A nonlinear transfer function, incorporating even-order terms, is developed to analyze the performance of passive intermodulation (PIM) in cascaded connectors. By conducting carefully designed two-tone tests, coefficients in the mathematical expression are determined. Numerical simulations utilizing the proposed model demonstrate the impact of second-order nonlinear products on third-order intermodulation (IM3) in series systems. By considering both the second-order nonlinear term and the superposition effect of multiple PIM sources, IM3 powers in series connector systems across various signal frequencies are predicted. Experimental measurements on ten N-type coaxial connectors in the GSM 900 MHz frequency band validate the theoretical calculations, showing a reduced average prediction error of 0.15 dB compared to our previous PIM model.