基于星座图统计的盲载波同步算法

Blind carrier synchronization algorithm based on statistical constellation

卫星通信信号中90%以上采用相位或幅相联合调制方案,包括多进制相位键控(multiple phase shift keying,MPSK),多进制正交幅度调制(multiple quadrature amplitude modulation,MQAM),多进制幅相键控(multiple amplitude phase shift keying,MAPSK)等,此外短波通信、移动通信中MPSK也是最常用的信号类型之一。载波同步是信号解调中十分关键与核心的部分。针对非合作接收条件下幅相调制类信号星座图分布特性进行了深入研究,提出了一种基于星座图密度统计的载波同步算法,实现了一定信噪比条件下盲频偏消除与星座图恢复,此方案不需要预先进行调制识别,对数据量要求不高,复杂度低,抗噪性能好,可广泛应用于常规信号以及未知、猝发信号解调。仿真表明,在接近或高于解调信噪比的条件下,该方法频偏估计性能接近克拉美罗限,可应用于工程实践。

More than 90% of the signal in the satellite channel use phase or amplitude and phase united modulation scheme including MPSK, MQAM, MAPSK, etc. In shortwave communications and mobile commu- nications, MPSK is also one of the most common signal types in addition. Carrier synchronization is crucial and the central part in signal demodulation. A thorough research on the constellation distribution of amplitude-phase modulated （APM） signal is conducted under the condition of non-cooperation receiving, and then a synchroniza- tion algorithm is proposed based on constellation density statistics which realizes the blind elimination of carrier offset and constellation recovery. This algorithm does not require a modulation recognition in advance, less a- mount of data, low complexity, good anti-noise performance, and it can be widely used in conventional signals and unknown, burst signal demodulation. The simulation results show that the performance of the algorithm gets close to Cramer-Rao bound under the condition that the signal to noise ratio gets close to the bound of de- modulation, and verify the reliability to engineering practice.