A Microwave System for Measurements of AM and FM Noise Spectra

This paper describes a noise measuring system with a high degree of flexibility in regard to video frequency coverage as well as radio frequency coverage. Noise systems for S, X, and Ku-bands were constructed to obtain high sensitivity at spectral frequencies from several Hz to 30 MHz off the carrier. The measured limiting sensitivities of the X-band set over the video range 20 Hz to 325 kHz with an input power of 10 mW are --145 dB for AM noise and 0.02 Hz rms for FM noise in a 100-Hz measuring bandwidth.