Noise Power Ratio (NPR) Testing of HF Receivers: Using notched noise to evaluate dynamic receiver performance

摘要

Noise-power ratio (NPR) testing is a performance test technique in which a notched noise-band is applied to the input of the DUT, and the output of the DUT is connected to a selective level meter whose bandwidth is less than that of the notch in the noise spectrum. The ICN (idle-channel noise) is measured with the noise-band (1) not notched and (2) notched The theory behind the NPR test is that the incident noise outside the notch will cause reciprocal mixing noise and multiple IMD products, which will appear in the idle channel (the passband of the selective level meter) and raise the ICN (idle-channel noise). This test method is used in characterising multi-channel FDM/FM systems (terrestrial microwave and satcom), where a notched noise-band of equal bandwidth to the baseband is applied at the transmit end, and a receiver with a channel filter as wide as (or narrower than) the notch is used to measure ICN with and without the notch inserted in the noise-band.