Introduction to panel discussion on mobile radio vehicular interference

Abstract

Vehicular electrical systems have the inherent capability of generating broad-band type impulsive interference, which, if effective control measures are not taken, will seriously degrade the performance of mobile communications receivers installed in the vehicle or installed in nearby vehicles. Thus we have two distinct problems: one, the interference to the communications receiver by the vehicular carrier; two, interference to the communications receiver from the electrical systems of nearby vehicles. The term broad-band interference describes the spectrum character of this interference which manifests its presence over a broad spectrum of frequencies extending from the very low radio frequencies to at least 1,000 mc. Figure 1 illustrates some of the properties of broad-band impulsive type interference. It will be noted that the idealized case of a pulse of infinite height and infinitesimal duration will result in a uniform spectrum from dc to infinity. More realizable pulses of rectangular and triangular shape respectively would have a spectrum such as shown in the lower portion of Figure 1. It will be noted that the spectrum amplitude, in the flat portion of the spectrum is substantially a function of only the volt-time area of the pulse, whereas at the higher frequencies the spectrum amplitude is a function of both the volt-time area and the pulse shape.