Nonlinear Mixing and Passive Intermodulation by Conductors with Rough Surfaces

Conductors with rough surfaces and their joints exhibit nonlinear response to high power RF signals. The resulting nonlinear signal distortions, predicted by the existing models, often differ considerably from the measurement results. These discrepancies usually originate from the concurrent effects of multiple concurrent sources of nonlinearities inherent to physical devices. This work demonstrates that surface roughness of good conductors plays a pivotal role in coupling the diverse mechanisms of nonlinear distortions of high-power RF signals. The sources of nonlinerities, both mechanical and electro-thermal, are discussed by an example of a joint of two flat conductors with randomly distributed asperities of their rough surfaces.