Modeling microwave contact discontinuities

The microwave contact discontinuities are some of the most frequent, though less studied, discontinuities one can encounter in microwave circuits and components. Some examples are the fixed contacts in connectors and cables, mobile contacts in electromechanical switches and RF MEMS switches and contacts in test setup probes and boards, etc. The paper deals with the physical model of the mobile microwave contacts in electromechanical switches and RF MEMS switches; however, many of the findings presented can be applied to other types of microwave contacts. The main parameters characterizing the microwave contacts are analyzed and estimated. A novel experimental method is presented that derives a correlation between the DC contact resistance and the measured RF scattering parameters that can be used for evaluating the RF performance over temperature by monitoring the DC contact resistance. In the non-linear case, the Passive Intermodulation (PIM) phenomenon is analyzed and the intermodulation levels are estimated using a 5th order model based on measured current-voltage contact characteristic.