A Passive Intermodulation Source Identification Measurement System Using a Vibration Modulation Method

A measurement system which uses acoustic vibration to locate passive-intermodulation (PIM) sources in base station antennas is presented. This measurement system uses mechanical vibration to modulate the PIM signal. The modulation of the PIM signal is detected, and its strength or presence/absence is used as guidance for selecting the location of the vibrating transducer. For the method to be successful, the PIM signal must be caused by loose mechanical contacts or loose nonlinear materials. By introducing the acoustic vibration at different locations in the base station antenna and observing if the PIM signal is modulated by the acoustic frequency, the most likely location of the PIM source is identified.