It is well known that active components will generate nonlinearities in systems. Various techniques have been developed to improve the performance of such devices during both the design and operational phase. It is easy to neglect that the passive devices can also introduce nonlinear effects; although sometimes relatively small, these nonlinearities can, if not corrected, have serious effects on system performance.
PIM stands for “passive intermodulation.” It represents the intermodulation products generated when two or more signals transit through a passive device with nonlinear properties. The interaction of mechanical components generally causes nonlinear elements. This is particularly evident at the junction of two different metals. Examples include: loose cable connections, dirty connectors, poor performance duplexers, or aged antennas.
PIM has been highlighted as a serious problem for service providers and equipment suppliers. Detecting and, where possible, solving the problem delivers increased system reliability and reduced operation cost. In this article we attempt to review the sources and causes of the PIM, along with technologies proposed to detect and solve it.
