A Comparison of Several Types of Modulation

This report presents a brief mathematical analysis of various modulation-demodulation combinations which may be used in data-link systems. Both digital and analog transmission systems are discussed. For some of the more important digital (binary) systems, the probability of making an error in detecting a binary symbol (using the solutions of Cahn, and Berry and Garbedian) is used to compare the various systems. It is shown that there is no one binary information transmitting system that is superior under all circumstances. Analog systems are discussed in terms of mean-square error (variance), and this criterion provides a convenient method for comparing digital and analog systems. There is a discussion of transmitter and receiver bandwidth-an important consideration for spectrum utilization. A time multiplex PAM system is discussed, along with crosstalk and noise level considerations for such a system. Most of the methods presented here are not new; however, it is hoped that the compilation and direct comparisons of the various modulation systems will be useful and timely for the systems engineer.