An in-phase component and a quadrature component of a digitized input DQPSK modulated signal are provided from interpolation filters, respectively. An instantaneous amplitude and an instantaneous phase of the input signal for each symbol clock are detected from the in-phase and quadrature components...http://www.google.co.uk/patents/US5590158?utm_source=gb-gplus-sharePatent US5590158 - Method and apparatus for estimating PSK modulated signals
