基于时频融合的长码直接捕获优化算法研究

长码因其码率高、周期长的特点，是现有导航系统广泛采用的军用信号体制。该文针对长码间接捕获方法的不足，以及扩展复制重叠捕获算法和均值捕获算法的局限性，提出一种以优化复杂度和搜索速度为目标的，基于扩展复制重叠捕获(XFAST)和均值算法相融合的时频捕获改进方法，给出了该算法的基本原理和捕获结果。对该算法的信噪比条件和复杂度进行了分析仿真，进一步论证了该算法应用于长码直接捕获的可行性和优良性。

Improved Long-code Direct Acquisition Algorithm Based on Time-frequency Fusion

At present, long-code with the characteristic of high bit rate and long period is widely used in satellite navigation system as military signal. To overcome the shortcomings of the indirect acquisition method for long-code, the limitations of the extended replication overlay acquisition algorithm and the mean acquisition algorithm, an improved time-frequency capture method based on the Extended replica Folding Acquisition Search Technique (XFAST) and the mean algorithm is proposed. The feasibility of the algorithm is simulated and the performance of the algorithm is analyzed. The simulation experiment shows the superiority of the proposed algorithm.