PM and AM noise of combined signal sources

The purpose of this paper is to establish a simple analytically model for computing the PM and AM noise of a signal obtained by combining the output of N, nominally independent, sources that takes into account different levels of noise and signal amplitude. Under ideal conditions, the noise of the combined signal is 1/N of the average source. This model shows that phase deviations between the combined signal and the individual sources leads to cross coupling between PM and AM noise. We find no plausible evidence for an intrinsic dependence of the noise reduction on spectral noise type in linear systems. This analysis assumes that environmental induced AM and PM noise are less than 1/3N below the noise in the individual sources and hence can be ignored.