基于信号估计的扩频测控信号快捕方法

A Rapid Capture Method of Spread Spectrum TT&C Signal Based on Signal Estimation

为进一步提高扩频测控系统的捕获速度,研究了借助辅助序列估计伪码相位的方法,分析了该估计算法的精度。针对该算法在高动态条件下估计偏差较大引起捕获概率骤降的问题,提出引入最大似然频偏估计修正相干载波的方法,显著提高捕获概率。设计了基于码相位估计和载波频率估计的快速捕获算法,仿真结果表明,该算法在载噪比较好的情况下可以有效完成捕获。为提高算法在较低载噪比时捕获的可靠性,提出将估计值作为部分匹配滤波辅助快速傅里叶变换(PMF-FFT)初值的综合捕获方法,与传统捕获方法相比,平均捕获时间显著降低,且并没有带来硬件复杂度的提高,具有一定的理论意义和工程应用价值。

In order to further increase the capture speed of spread-spectrum tracking,telemetry and com-mand （TT ＆C） system,the algorithm of state estimation for code phase with the help of auxiliary sequence is researched and the accuracy is analyzed. For the problem that the acquisition probability decreases abruptly under the high dynamic condition,the method of frequency offset estimation based on Maximum Likelihood is put forward to fix the deviation of coherent carrier frequency,and the capture probability can be signifi-cantly improved. The rapid capture algorithm based on the code phase and carrier frequency estimation is designed. The simulation result shows that the algorithm can effectively capture the signal in good case of carrier-to-noise ratio. To improve the reliability of the capture algorithm in low carrier-to-noise ratio,the integrated capture method is proposed which uses the estimated result as the initial value of partial matched filter-fast Fourier transform（ PMF-FFT）. Compared with the traditional method, the proposed method can significantly reduce the average capture time without increasing hardware complexity. The rapid capture method has certain theoretical significance and engineering application value.