Filter Distortion and Intersymbol Interference Effects on PSK Signals

The combined effects of filter distortion and the associated intersymbol interference on coherently detected biphase and quadriphase PSK signals are studied in white Gaussian noise. A determination is made of the system performance degradation from matched-filter detection resulting from the use of a linear channel model that focuses attention on the critical filters in the communication link. The critical filters that affect performance consist of transmission filters in the transmitter and/or transponder, receiver predetection filters, and data filters associated with the detector. Numerical results for adjacent symbol interference are given for detection using both integrate-and-dump filters as well as more general data filters, particularly an undumped 2-pole Butterworth data filter. The numerical results include symmetrical band limiting, broad-band filtering with a frequency offset, mismatched data filtering, cascaded filter chains, and the effects of pure phase distortion.