Passive Intermodulation (PIM) Testing Guidelines

Passive Intermodulation (PIM) occurs when two or more high power RF signals encounter PIM sources or materials in an RF path. These PIM sources behave like a mixer causing new signals to be generated at mathematical combinations of the original RF inputs. In the figure to the right, f1 and f2 represent two Tx frequencies present at a typical cell site and ± m•f1 ± n•f2 are the PIM signals generated by those Tx frequencies. When these PIM signals fall in the Rx band of the cell site the noise floor rises causing increased dropped calls, reduced data transmission rates and decreased system capacity. The impact of PIM on the network performance can be severe, especially for modern systems such as CDMA, UMTS or LTE.