PIM (passive intermodulation) occurs when 2 or more signals are present in a passive device that exhibits a non-linear response. The nonlinearity is caused by dissimilar metals, anodic effects or loose connections. This nonlinearity does not manifest itself at low input signal levels, and is therefore also a function of the high power level transmit signals in the system. The resultant products are referred to as 3rd, 5th, order intermodulation products, etc. The 3rd order products are typically the focus in most system design. The real problem occurs if the 3rd order PIM products generated by the transmitter channels fall within adjacent receiver channels. This upsets the adaptive settings of the receiver and desensitization will occur. The result is typically a dropped call.
