PIM performance of RF components — A growing concern for RF compliance testing of large wireless MIMO transmitters

The passive intermodulation (PIM) had rarely caused a concern for the Radio Frequency (RF) compliance testing of licensed wireless systems in the past. But this may change as the broadband LTE (Long-Term Evolution) systems with MIMO (multiple-input and multiple-output) technology are being rolled out nationwide. This article discusses the causes of PIM distortion in RF testing and elaborates on why the PIM performance of RF measurement components becomes so important for testing the latest wireless massive MIMO equipment for higher power application. The static PIM distortion of common RF measurement components, such as RF cables, attenuators and directional couplers was measured. The results illustrated the importance of adding PIM performance as one of selecting criteria for RF testing assets. The steps for negating PIM generation during RF compliance testing are provided as well.