π/4-DQPSK调制解调系统的关键技术

Research on Key Technologies in π/4-DQPSK Modulation and Demodulation System

针对π/4-DQPSK调制解调系统中成形滤波、量化误差和数字下变频中的低通滤波器等关键技术进行研究.在此基础上,对于接收端有频偏的相干解调系统采用改进的具有2个Timing Er-ror信号的Gardner位同步算法,并用simulink实现整个调制解调系统.从仿真结果可以看出,改进的Gardner同步算法能帮助系统有效地补偿频偏,并且使系统具有非常好的误码性能.

This article studies the key technologies in π/4-DQPSK modulation and demodulation system about pulse shaper, quantization error and low pass filter in DDC. On the basis of the study, it adopts betterment of Gardner bit synchronous algorithm which has two timing error signals for coherent detector in frequency excursion sink, and actualizes the whole system with Simulink. The result of emulation shows that this synchronous algorithm is compensatory to frequency excursion system, and enables the system to perform a nice error rate.