SENSITIVITY MEASUREMENTS OF A PASSIVE INTERMODULATION NEAR-FIELD SCANNER

摘要

A passive intennodulation (PEM) near-field XY-scanner for the GSM900 frequency band has been earlier constructed to localize distortion sources in antennas and in other open structures. However, the measured inter-modulation level has been relatively high, around -90 dBm. The equipment should be able to measure distortion levels down to -115 dBm with an input power of 2x20W, since the noise floor of a GSM900 base station is typically around -110 dBm. The sensitivity is limited either by thermal noise or by residual intennodulation distortion depending on the sensor coupling. Various causes of residual intennodulation distortion in the PIM near-field measurement are considered and evaluated. Sensitivity measurements of the scanner have been carried out on two test devices. With a sensor coupling of 30 dB, sensitivities of -115 dBm and -105 dBm have been achieved with an electric and a magnetic field sensor, respectively.