A Noise Floor measurement tests for Rx interferers that can effect a PIM versus Time measurement. In this measurement, transmit (Tx) power is
Off, which allows you to check for external interference at the IM frequency being measured. The intermodulation distortion (IM) products of interest are in the same frequency range that is used by mobile equipment to communicate with the base station. Nearby mobiles can generate signals high enough to interfere with a PIM measurement. The Noise Floor measurement displays the signal level that is received by the MW82119A PIM Master at the IM product frequency as a function of time with TX
1 and TX
2 turned
Off. The PIM Master is in PIM vs. Time analyzer mode during a Noise Floor measurement, but only the PIM Master receiver is being used. A typical noise floor measurement is approximately –130 dBm, as shown in
Figure: Typical Noise Floor (No External Interference, No Limit Line). Refer to
PIM Testing ProcedureAnritsu recommends that you make a Noise Floor measurement before making a PIM versus Time measurement in order to rule out external interference. If external interference is present, use a spectrum analyzer (such as an Anritsu Spectrum Master with Interference Analyzer option) with a directional antenna to find the interference. After the external interference has been resolved, then begin PIM testing to see if PIM is present at the site.