A bit error probability analysis of a digital PLL based demodulator of differentially encoded BPSK and QPSK modulation

A bit error probability analysis of a digital phase locked loop (PLL)-based demodulator of differentially encoded binary phase-shift keying (BPSK) and quadrature phase-shift keying (QPSK) modulations is presented. Differential decoding is a method of resolving a phase ambiguity typical of fully modulated signals that uses two consecutive demodulated symbols to estimate the information symbols. The effects of a noisy phase reference on demodulator performance are well documented for uncoded modulations (single symbol demodulation). The performance for phase reference time variations between the two symbols is investigated. The time varying reference investigated is produced by a digital PLL. The noisy phase reference has negligible additional effects on the bit error probability for differentially encoded BPSK and QPSK