Sensitivity of PSK Modulation Techniques to Nonlinear Distortions

A model of a PSK transmitter including the modulator, a filter, and a nonlinear amplifier is considered. The envelope fluctuations of the filtered signal and the spectral spreading effect, resulting from nonlinear distortion are analyzed, considering three PSK modulation techniques: conventional four-phase PSK (
Q
-PSK), offset PSK(
O
PSK) and logic-PSK(
L
-PSK). The last technique exhibits the smallest envelope fluctuations and the lowest sidelobe levels after nonlinear distortion, particularly when the nonlinear element operates near saturation.