Whitepaper that discusses passive inter-modulation sources and
cancellation methods. When two or more signals of different
frequencies pass through a nonlinear system, intermodulation
distortion (IMD) occurs, resulting in the formation of spurious
distortion signals. IMD is most commonly found in active circuits
of a radio system, but it can also be found in passive wireless
components such as lters, transmission lines, connectors, antennas,
attenuators, and so on, especially when transmit power is quite
high. Passive intermodulation (PIM) distortion is the name given to
the IMD in the latter scenario. With the evolution of radio systems
and the scarcity of radio spectrum, PIM interference is being
recognized as a potential stumbling block to a radio network's
maximum capacity. This article classifies the PIM sources in BS
radio systems into two categories, internal and external sources.
Internal sources are the radio's passive components such lters,
transmission lines, connections, antennas, and so on. External
sources, on the other hand, are passive items that are located
outside of the BS antenna but inside the RF signal path, such as
metallic and rusted objects in the antenna near eld. The high power
current flowing through such passive devices can cause nonlinear
behavior, resulting in IMD for both types of sources. Also, a
review of PIM mitigation techniques is presented in the
article.
Read more https://packetstormsecurity.com/files/166422/PIM_YUPANA.pdf