Viavi Solutions Inc.
Passive intermodulation (PIM) measurements in common public radio interface (CPRI) spectrum analysis

Abstract:

A test device for detecting and measuring distance to passive intermodulation (PIM) is disclosed. The test device may comprise a receiver to receive a signal from a test point of a distributed cell site comprising a remote radio head (RRH) and a baseband unit (BBU) separated and connected via an optical feeder. The test device may also comprise a processor to detect passive intermodulation (PIM) and measure distance to the PIM (internal or external). For example, the processor may replace downlink IQ data in the signal with two-tone waveform IQ data, transmit the two-tone waveform IQ data to the RRH, and to monitor uplink spectrum to detect PIM, where the uplink spectrum may comprise uplink IQ data from the RRH. The processor may also perform uplink spectrum analysis using radio frequency (RF) monitoring, measure a time delay for the two-tone waveform and the detected PIM, and calculate a distance to the PIM based on the time delay.