Spectral characteristics of convolutionally coded digital signals
Abstract
The power spectral density of the output symbol sequence of a convolutional encoder is computed for two different input symbol stream source models, namely, an NRZ signaling format and a firstorder Markov source. The effects of alternate symbol inversion on this spectrum are also considered. The mathematical results are illustrated with many examples corresponding to optimal performance codes. It is demonstrated that only for the case of a purely random input source (e.g., NRZ data with equiprobable symbols) and a particular class of codes is the output spectrum identical to the input spectrum except for a frequency scaling (expansion) by the reciprocal of the code rate.
 Publication:

IEEE Transactions on Communications
 Pub Date:
 February 1980
 Bibcode:
 1980ITCom..28..173D
 Keywords:

 Data Transmission;
 Error Correcting Codes;
 Power Spectra;
 Signal Encoding;
 Spectrum Analysis;
 Transmission Efficiency;
 Convolution Integrals;
 Digital Systems;
 Mathematical Models;
 Optimization;
 Performance Prediction;
 Spectral Correlation;
 Spectral Energy Distribution;
 Communications and Radar