该文针对伽利略搜救系统中TOA高精度估计的需求，考虑了实际接收的COSPAS-SARSAT信号中信息位宽的不确定度和调制不对称度，提出了基于多维联合极大似然估计的TOA估计算法。文章首先介绍了含调制不对称度的COSPAS-SARSAT信号模型，然后推导了算法原理，并给出了具体的实现过程。Monte Carlo仿真结果表明，在34.8 dBHz的处理门限、调制不对称度为5%和-5%的极端条件下该算法得到的TOA估计的均方根误差小于13.5 s，满足15 s的系统指标要求，优于其他算法的估计精度。
According to the high precision demand of estimating TOA in Galileo Search And Rescue (SAR) system, and considering the uncertainty of message bit width and the asymmetry degree of modulation in actual COSPAS-SARSAT signal, a new TOA estimation algorithm based on Multiple dimensions Joint Maximum Likelihood Estimation (MJMLE) algorithm is proposed. The COSPAS-SARSAT signal model containing the asymmetry degree of modulation is introduced first. Then the principle of the algorithm is derived and the concrete realization is given. Monte Carlo simulation results show that when Carrier to Noise Ratio (CNR) equals to the threshold of 34.8 dBHz and the asymmetry degree of modulation is the extreme condition with 5% and -5%, root-mean-square errors (rmse) of TOA estimation of this algorithm is less than 13.5 s, which can satisfy the system requirement of 15 s and better than that of other estimation algorithms.