Digitally phase modulated (DPM) signals

Conditions of spectrum congestion have led to the search for new narrow-band digital modulation techniques. Phase modulation has a constant carrier envelope, and it is, therefore, well suited for communication systems which must exhibit good spectrum compactness, even after being passed through a nonlinear amplifier. Such requirements are found in mobile communications and satellite communication systems. The present paper is concerned with signals generated by digital circuits. Such 'staircase type' signals (e.g., PSK) do not belong in the strict sense to the class of continuous phase modulation (CPM) schemes. However, these signals may be considered to represent a practical approximation to this class of signals. Attention is given to the autocorrelation of a stationary phase modulated signal, the autocorrelation function of a DPM signal, and the effect of oversampling.