RF Engineering
What Is Passive Intermodulation (PIM) and How to Prevent It?
Passive intermodulation, or PIM, is interference a radio system makes for itself when two or more strong transmit signals mix in a passive part that is not perfectly linear, such as a connector, cable joint or antenna. The new signals it creates can fall straight into the receive band and quietly desensitise the receiver. This guide explains what PIM is, the formula for where its products land, a worked cellular example, how it is measured in dBc, what causes it including the rusty bolt effect, and the practical steps that keep it off a site.