PIM (Passive Intermodulation) interferences is a common problem in mobile phone networks. Such interferences are caused by utilizing higher and higher power levels at high frequencies. Moreover, this issue is more complicated when one antenna track is used for several systems. In such situation, these interferences trigger overlaying of TX and RX bandwidth signals. The most common direct reason of occurrence of PIM are defects of antenna track elements caused by installation faults or using low quality passive elements which can cause overlaying of TX and RX bandwidth signals.
PIM analyzers are required in order to find these faults. These devices generate two CW signals at two different frequencies of power up to 40W and test 3rd, 5th and 7th grade noises. After putting this measurement on DTF measurement it is possible to locate a problem. During a measurement the antenna track is carefully tapped in order to increase visibility and often generate interferences.
Today’s technology requires understanding and knowledge concerning causes of PIM in order to perform installations ensuring high quality.
Noise levels for generated signals
Measurement example: PIM distance