SOQPSK信号的定时相位联合估计算法

Joint timing and phase estimation algorithm for SOQPSK signals

针对SOQPSK信号同步难度高、算法复杂的问题,提出了一种面向判决的定时相位联合估计算法.该算法基于SOQPSK信号的Laurent分解形式,先运用最大似然序列检测得到判决数据,然后将定时和载波相位的联合似然函数简化,得到定时似然函数,再用并行搜索法恢复出定时信息,最后利用定时信息估计出载波相位信息.通过分析SOQPSK信号的2种常见形式全响应SOQPSK-MIL和部分响应SOQPSK-TG,提出了一种联合定时和相位估计算法的低复杂度实现方案.在加性高斯白噪声信道下进行了仿真.结果表明:该算法同时适用于SOQPSK-MIL和SOQPSK-TG信号,定时估计逼近理想曲线.存在定时偏差时,载波相位标准差在10-3～10-4数量级;定时偏差为0时,载波相位估计逼近理想曲线.载波相位偏差不影响定时恢复性能.

To solve the difficulty and complexity of synchronization problem in ternary shaped-offset quadrature phase shift keying（SOQPSK）,a decision-directed joint timing and carrier phase estimation algorithm was proposed.Based on Laurent representation of SOQPSK,the symbol sequence was reco-vered by maximum likelihood sequence detection（MLSD）.The joint likelihood functions of timing and carrier phase parameter were simplified into the likelihood function of timing parameter.The estimated timing value was then recovered by parallel searching method to obtain the estimated value of carrier phase.According to the common signals of full response SOQPSK-MIL and partial response SOQPSK-TG,the complexity-reduction implementation scheme of joint timing and carrier phase estimation algorithm was proposed.Simulation was completed under additive white Gaussian noise（AWGN） channel.The results show that the proposed algorithm is suitable for SOQPSK-MIL and SOQPSK-TG.The timing error variance curve is close to the theoretical limit.The carrier phase error variance is at 10-3-10-4 order of magnitude with timing offset,and close to theoretical limit without timing offset.Carrier phase error has little effect on the timing recovery algorithm.