基于FFT处理的分段匹配滤波器是动态长PN码捕获的主要方法。滤波器参数的最佳设置是实践中经常面临问题。文章在建立其数学模型的基础上,对高斯白噪声及瑞利衰落信道下FFT输出的概率密度公式进行了推导,证明在恒虚警条件下,存在最佳分段数和FFT点数组合,可以使总体运算量最小,检测概率最高。 Fractional matched filter based on FFT processing is the main method of dynamic long PN code acquisition. The best setting of the filter parameters is often a problem in practice. Based on the mathematical model, the paper deduces the probability density formula of FFT output under Gaussian white noise and Rayleigh fading channel. It proves that under the constant false alarm condition, there exists the optimal combination of segment number and FFT point number, So that the overall calculation of the smallest, the highest detection probability.