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What is Passive Intermodulation (PIM) Distortion, and how can it be Mitigated?

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  • Passive intermodulation (PIM) distortion is a wireless communication system degrading phenomenon that has been a concern for cellular telecommunications, satellite communications, and wireless network development. PIM is such a concern in cellular/wireless communications that there are entire distinct Low PIM Components and Cable Assemblies product lines designed to aid in preventing or mitigating PIM distortion.

    PIM occurs only in parts of a signal chain and wireless communication channels that are passive and where two or more signals are present. When the conditions are right and two or more signals pass through a PIM generation condition, the result is nonlinear distortion products. If the input signal power levels are high enough, these distortion products could result in relatively high-power distortion signals within one or more receive bands of a sensitivity receiver. If this happens, the receiver could be desensitized, the noise floor may increase, and in extreme conditions, the receiver may be damaged by the combination of PIM distortion products combining with the power level of other signals.

    Where nonlinear distortion is common and expected with active devices and can therefore be predicted and readily mitigated, it is very difficult to predict and troubleshoot for PIM. PIM issues may also appear over time and may be difficult to identify and determine the PIM generator(s). There are a variety of potential PIM generators, including close proximity of dissimilar metals in the signal path, oxides/metallic contact points, loose connectors, damaged cable conductors, dirty/debris laden connections, poor quality duplexers, corroded antennas etc. The common anecdote on PIM generators is that a PIM source could be virtually any conductor, even a rusty bolt on the antenna tower or mast.

    Common Low PIM RF Components

    Low PIM Adapters

    Low PIM Antennas

    Low PIM Cable Assemblies

    Low PIM Cables

    Low PIM Connectors

    Low PIM Couplers

    Low PIM Power Dividers

    Low PIM Surge Protectors

    Low PIM Tap Power Dividers

    Low PIM Tappers

    Low PIM Terminations

    Hence, it is generally a challenge to deal with PIM issues, as one or more PIM generators could be at play. With the growing diversity of wireless communication and sensing services increasing the threshold for potential intermodulation distortion issues, designing wireless networks and sensing systems to handle PIM is becoming increasingly critical. This is why there are now more distinct Low PIM RF products available, as in some cases it is advantageous to use Low PIM components in advance to prevent PIM thresholds being too high during initial installation, and also to lower the PIM response by retrofitting older systems that may have aged and PIM thresholds have risen. A Low PIM component is simply a version of an RF component that has specifically been designed and tested to ensure a PIM response that is below industry standard levels.

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