Probability Distribution of Noise Due to Fading on Multisection FM Microwave Systems

The probability distribution of expected baseband noise during fading at the end of a multisection microwave radio system is an important consideration in the engineering of a long system. This paper gives measurements of fading on a single path, and derives an estimate of the probability distribution of expected noise due to fading on a particular 68-section system of which the single path is a typical part. A comparison is shown with a measured cumulative distribution curve of noise at baseband subsequently obtained on the long system under operating conditions. A numerical method of combining distribution curves was used in this case and the so-called "breaking effect," due to deep fades, is included. This method is described in the Appendix. While this paper is directed specifically to a particular microwave system, the principles described can be applied equally well to others.