The paper introduces the pi/4-QPSK and pi/4-DQPSK moderation and demodulation, specifically, the simulation focus on the pi/4-DQPSK moderation and demodulation. Generally, the pi/4-DQPSK could operate the differential moderation and demodulation effectively, especially useful in the situation that difficult to purify the carrier wave. Therefore, It is necessary to utilize the simulation in the research of the pi/4-DQPSK. In this paper, it illuminates each of the block diagrams from sender to receiver. Firstly, it introduce the principle and simulation figure of the pi/4-QPSK and pi/4-DQPSK technology, then use the MATLAB as the simulation instrument, according to analyze each simulation block of the communication system, compared the number of error between pi/4-QPSK and pi/4-DQPSK in the AWGN channel and Rayleigh channel., and the influence of result after add the RC filter. Base on the comparison of the signal noise ratio resulted from the above method, the quality of moderation and demodulation of pi/4-QPSK is superior in the same environment.
