Prediction of Passive Intermodulation From Coaxial Connectors in Microwave Networks

Coaxial connectors are frequently the dominant contributors to passive intermodulation (PIM) distortion in high-frequency networks. This paper reports on a circuit model enabling estimation of PIM distortion by coaxial connectors in the design of high-frequency networks. A method of modeling the effect of multiple point sources of PIM is applied to coaxial connectors, allowing the prediction of the PIM of networks with several connectors. Typical ranges of PIM produced by common connectors in a two-tone test are reported. The stability and repeatability of PIM produced by a single connector is examined. Nonlinear current-voltage curves for coaxial connectors are given that predict the PIM distortion output by coaxial connectors over a broad range of input powers. An experimental verification is given showing that PIM of a system can be predicted if the characteristics of the individual components are known.