改进环路结构的Gardner定时恢复算法  

Gardner timing recovery algorithm for improved loop structure

作　　者：李维 江虹[1] 伍春[2] 邓皓文 LI Wei;JIANG Hong;WU Chun;DENG Haowen(School of Information Engineering,Southwest University of Science and Technology, Mianyang Sichuan 621010, China;College of Defense Science and Technology,Southwest University of Science and Technology, Mianyang Sichusn 621010, China)

机构地区：[1]西南科技大学信息工程学院,四川绵阳621010 [2]西南科技大学国防科技学院,四川绵阳621010

出　　处：《计算机应用》2019年第10期3013-3017,共5页journal of Computer Applications

基　　金：国家自然科学基金资助项目(61379005)~~

摘　　要：针对经典的Gardner定时恢复算法存在同步建立时间长、同步稳定性能差等问题,提出一种改进环路结构的Gardner定时同步恢复算法。首先,该算法选用立方插值和分段抛物线插值两种插值滤波器进行插值,得到两路最佳插值序列;其次,分别计算两路插值序列对应的定时误差并求加权平均值,得到环路的定时误差;最后,以两路最佳插值序列的加权平均值作为环路输出。针对正交相移键控(QPSK)、正交幅度调制(16QAM)两种调制信号进行了仿真验证。仿真结果表明,该改进算法作用于QPSK信号时同步稳定性更好,相比作用于16QAM信号,其环路开始同步时码元的位置对应的序列数明显减小;并且该算法在信噪比为-5dB的情况下使QPSK信号星座图收敛半径为0.26左右,与类似锁频锁相(FPLL)的改进Gardner定时恢复算法相比收敛半径减小约0.08,该算法有效地缩短了同步建立的时间,提高了环路的稳定性,可广泛应用于高速解调系统。Aiming at the problems of long synchronization setup time and poor synchronization stability in classical Gardner timing recovery algorithms, a Gardner timing synchronization recovery algorithm with improved loop structure was proposed. Firstly, two interpolation filters with cubic interpolation and piece wise parabolic interpolation were used to obtain two optimal interpolation sequences. Secondly, the timing errors corresponding to the two interpolation sequences were calculated respectively and the weighted average value was obtained to gain the timing error of the loop. Finally, the weighted average value of two optimal interpolation sequences was used as the loop output. The simulation experiments of two modulated signals of Quadrature Phase Shift Keying (QPSK) and16 Quadrature Amplitude Modulation (16QAM) were performed. Simulation results show that the synchronization stability of the proposed algorithm is better on QPSK signal. Compared with performing on 16QAM signal, the number of sequences corresponding to the position of the symbols when the loop starts the synchronization is obviously reduced. Additionally by using the propposed algorithm, the convergence radius of the QPSK constellation is about 0.26 when the SNR is -5 dB. Compared with the improved Gardner timing recovery algorithm similar to Frequency and Phase Lock Loop (FPLL), the convergence radius is reduced by 0.08. This algorithm effectively shortens the synchronization setup time, improves the stability of the loop, and can be widely applied in high-speed demodulation system.

关 键 词：位同步环路结构 改进型Gardner算法 加权平均 同步建立时间 同步性能 

分 类 号：TN911.7[电子电信—通信与信息系统]