General Method for Calculating the Spectrum of a Zero Substitution Coded Signal

Abstract

This paper describes a general method for calculating the power spectra of zero substitution coded signals and applies this method to calculate the B3ZS signal spectrum of the DS-3. Many digital radio systems transmit a signal which consists of DS-3 level baseband signals. Therefore, knowledge of the B3ZS spectral characteristics is important in DS-3 level interference and systems studies. The method used for calculating spectral densities of substitution coded signals is based on signal-flow graph analysis. While signal-flow graph identities and Mason's gain formula have been used in the past in the calculation of some substitution coded spectra, they become unduly cumbersome when applied towards complex spectra such as that of the B3ZS signal. In place of the graph identities and gain formula, two matrix techniques are introduced that can be used in general to simplify spectral calculations for substitution coded signals. The methodology used in analyzing these communication signals can also be applied to other related fields such as coding of signals for magnetic recordings.