Degradation of BER by Group Delay in Digital Phase Modulation

One of the most important destructive factors in digital phase modulation is group delay variations (GDV) over frequency. This factor causes a larger bit error rate (BER) from expected BER at specific Eb/NO values. Thus, the effect of group delay degradation must be compensated. GDV is difficult to analyze exactly for modulation purposes in practical systems, but it is relatively simple to simulate. In this paper, we focus on the effect of group delay on digital phase modulation and simulate the effects of Ripple, Linear, and Parabolic group delays on BER to identify a suitable criterion by which the acceptable variations of group delay can be determined before the demodulator.