卫星信道下混合信号频偏的估计方法

Estimating Method of Frequency-Offset for Mixing Signals in Satellite Channels

针对非协作卫星通信场合中同调制参数的MSK单通道混合信号的载波频偏估计问题进行研究,推导了卫星信道条件下MSK混合信号的循环谱表达式。通过搜索零频率处循环频率轴上的大强度谱线进行混合信号频偏估计,并针对谱线选择时存在的模糊问题,利用循环谱快速算法中的泄漏谱线包络辅助进行模糊消除。仿真结果表明在信噪比大于-20 dB时,对混合信号载波频偏估计较为准确。该方法对混合信号载波初相和时延等未知参数影响不敏感,并且不需要任何先验信息,其估计精度能够满足后续信号处理的需要。

Aimed at non-cooperative satellite communication applications, a carrier frequency-offset estimation method was proposed for MSK mixing signals, and the expression of cyclic spectrum was deduced for the signals. The carrier frequency-shift was estimated by searching high-intensity spectral lines along cyclic frequency axis at zero frequency. The envelop of spectral leakage introduced by fast cyclic spectrum algorithm was applied to eliminate the illegibility of spectral line selection. Simulation results show its good estimating performance with SNR greater than -20 dB. The method is insensitive to unkown parameters of mixing signals, such as carrier phase and timing offset. It does not require any prior information and the estimation accuracy can meet the needs of subsequent signal processing.