基于扫频算法的QPSK载波恢复技术研究

针对欧洲DVB-S及DVB-S2协议标准均采用的QPSK调制解调方法,探讨一种有效的载波恢复技术。扫频算法具有强大的频偏捕获能力,在此基础上,本文结合判决自导方法,实现了很大范围内频偏的捕获与跟踪;改进了扫频门限的设定方法,使得该算法可适用信噪比大大降低;引入维特比译码反馈机制,自动调整系统参数,增强了同步系统的自适应能力。Matlab仿真结果表明,该方法性能可靠,稳定工作信噪比可至0.5 dB,频偏捕获范围甚至可达几倍符号率,适用于全数字高速数传QPSK接收系统,同时也可移植、推广至mPSK全数字雷达接收机中。

Research Based on QPSK Carrier Recovery Method of Sweeping Algorithm

With the reference to the relevant specifications of DVB-S and DVB-S2,an effective QPSK carrier recovery method is integrated.Based on the great capability of sweeping algorithm to capture frequency offset,capturing and tracking of that in big range is accomplished associated with decision directed method.Also an improved design of sweeping threshold is used under greatly decreased Signal to Noise Rate(SNR).After a scheme of Viterbi decoding feedback employed here to adjust system parameters automatically,the system gets the enhanced adaptive ability.The simulation results with Matlab shows that the method discussed is of reliability and reaches several times symbolic rate capturing range,which applies to not only all digital transmission QPSK receiving system,but also could be transplanted and generalized to mPSK digital radar receivers.