SPECTRAL SHAPE PREDICTOR FOR PCM/FM TRANSMISSIONS

Abstract

This paper will demonstrate a computer application program to predict the spectral shape and IRIG-RF bandwidth required for a PCM/FM telemetry system. A filtered PCM bit stream is constructed from a Fourier series and used to FM-modulate the RF carrier. The Fourier transform of the FM-wave is calculated numerically, and voltage amplitude levels are plotted on a Tektronix graphic display. Several PCM bit patterns are used and a composite display is formed to approximate an actual PCM/FM spectrum. A comparison of predicted and actual spectra will be presented.