Man-made impulsive noise on the 137 MHz VHF LEOSAT channel

Abstract

Personal communications has produced a demand for low-Earth orbit satellite (LEOSAT) implementation. A proposed LEOSAT link at VHF would provide paging and radio-location services to subscribers in automobiles.

Link performance has traditionally been determined by thermal background noise produced internally as well as externally to the radio receiver. Most recently, however, man-made noise has become the dominant source of link interference at VHF frequencies and below. This thesis examines the statistical behavior of man-made noise through a series of in situ measurements, and implements a statistical-physical mathematical model to provide bit-error rate (BER) predictions for system designers. The model is also applied in an attempt to scale the statistics for bandwidths other than the noise measurement receiver.

Man-made noise is inherently impulsive, due to switching processes in the AC power distribution system. Gaussian noise models are therefore inappropriate for the description of man-made noise statistics. A model by Middleton was developed around the Poisson mechanism to accurately predict the amplitude probability distribution (APD) of the received noise. Unlike empirical models, the constants employed by the Middleton model posses physical significance.