Noise measurements of microwave local oscillators

A method for measuring the spectral distribution of amplitude fluctuations and frequency fluctuations in microwave oscillators is described. The method provides for evaluation of (1) amplitude fluctuations in terms of signal to noise ratio; (2) frequency fluctuations in terms of two parameters: (a) rms deviation; (b) rms rate of change of deviation. In addition, the method permits estimation of the correlation between these two noise components. Some typical results of measurements are described, and certain implications of the effects of system parameters on interpretation of these results are considered. For a specific system, two measurements are shown to be sufficient to determine the effect of frequency noise on system performance.