Modeling of Passive Intermodulation in Coaxial Connectors Under Sub-Zero-Temperature Conditions

Sub-zero-temperature environments can alter the dielectric state and current transport characteristics of coaxial connector contact interfaces, thereby affecting their passive intermodulation (PIM) performance. To address this issue, a PIM modeling method for coaxial connectors operating under low temperature conditions was proposed. First, an equivalent dielectric film formation model was developed based on water vapor transport and evolution processes, through which the relationship between ambient temperature and film thickness was obtained. The resulting film thickness was then incorporated into a finite element (FE) model of the connector inner conductor to investigate the temperature-dependent dielectric properties of the film and the corresponding variations in the local electric field and surface current density distributions. On this basis, a temperature-dependent equivalent impedance model of the film covered region was established, and an effective nonlinear interfacial constitutive relation was introduced to characterize the nonlinear response of the film-covered contact interface and develop the PIM power prediction model. Finally, a low temperature PIM measurement platform was constructed, and experiments were conducted using different ambient temperatures. The results demonstrate that the proposed model accurately captures the variation in connector PIM power under sub-zero-temperature conditions, providing a theoretical basis for PIM prediction and reliability evaluation of coaxial connectors operating in low temperature environments.