中文摘要：

针对低信噪比条件下，罗兰C天波信号延迟时间估计的准确性和有效性问题，提出基于优化包络的相关系数时域法。通过分析标准罗兰C信号包络的特征，分别采用微分和二次微分方法对罗兰C信号包络进行优化，形成陡峭的包络信号上升沿；利用相关系数法对接收信号包络和参考信号包络进行匹配，形成的匹配峰值分别对应地波和天波信号到达的时刻，由此可获得天波信号的延迟时间；通过仿真分析和实测信号试验验证，证明该方法能满足数字化接收机的实际要求，并具有更高的抗干扰能力、估计准确性和自动识别功能的特点。估计的结果还可以作为判别相位跟踪和周期识别正确率的辅助依据。

英文摘要：

For insuring accuracy and validity of the Loran C signal sky wave delay estimation in low SNR, correla- tion coefficient time domain method based on optimization envelope is presented. Firstly, the characteristic of standard Loran Csignal envelope is analysed. Differential and Quadratic differential of Loran C envelope signal are used respectively in order to form the steep rise-time of envelope signal. Secondly, receiving signal envelope and reference signal envelope are matched by correlation coefficient time domain method, then the matching peak results correspond the arriving time of ground wave and sky wave signals respectively. Hence, sky wave delay estimation time isgot. Finally, through the simulation analysis and the measured signal test, it is proved that the method meets digital receiver＇s needs, and has the characteristics of higher the anti-jamming ability, estimation accuracy and automatic identification function. At the same time, the estimation result serves as auxiliary basis that iudaes the orecision rate of phase track and cycle identification,