Nonlinearities in metal contacts at microwave frequencies

Generation of intermodulation products arising from nonlinearities at metal-to-metal contacts for microwave frequencies has been investigated. Detailed studies concentrated on the intermodulation products generated at contacting faces between both similar and dissimilar metals, and included contact materials of copper, beryllium-copper, brass, oxygen-free nickel, mild steel, stainless steel, aluminum, and twelve home-made steels with various compositions. The surface properties of the materials were found to be of prime importance. Measurements were carried out at frequencies around 1.5 GHz. The variations of the 3rd- and 5th-order intermodulation product levels with power levels of the fundamental signals and with the axial force applied to the contact were studied.