Abstract: In this paper, a new algorithm of digital signal processing for QPSK demodulation is proposed,This algorithm directly processes the phase of the received signal, thus realizing the demodulation of the QPSK。In contrast to other known methods it allows it allows free-running carrier oscillators. The analysis of the noise property of the algorithm is also presented. The computer simulation results indicate that the algorithm is a new method with a bright future for application.

Key words: digital signal processing, carrier synchronization, kalman filter, digital communication, quadrature demodulation