低信噪比S模式应答信号相关检测方法

针对低信噪比条件下S模式应答信号检测概率低、虚警概率高的问题，提出一种基于数据包检测、单脉冲匹配滤波和报头多脉冲检测等三次相关检测的增强识别方法。该方法首先利用数据包相关检测得到数据包位置，从而确定报头脉冲的检测门限；然后利用单脉冲匹配滤波对信号进行降噪处理，确定脉冲位置；最后估计脉冲幅度和噪声功率，利用多脉冲相关检测识别信号报头。通过这三次相关处理，该识别算法可提高S模式应答信号的准确识别率。理论推导了检测概率的数学表达式，通过计算机仿真，在期望虚警概率下，本文方法基本达到了理论检测概率，同时对比了本文方法与传统的直接匹配滤波法、脉冲前沿检测法、基带归一化互相关法的识别性能，验证了本文算法性能的优越性。 

A correlation detection method for Mode S reply signal under low SNR

To cope with the low detection probability and high false alarm probability of Mode S reply signal detection under low SNR conditions, a novel recognition method based on triple correlations, which include detection of the whole signal, matched filtering of single pulse and correlation detection using signal preamble with multiple pulses, is proposed. Firstly, correlation of the whole signal is applied to obtain the signal position and the threshold of preamble, then matched filtering of single pulse is adopted to de-noise for signal and to determine the pulses position. Finally, the pulse amplitude and noise power are estimated and correlation of multiple pulses is applied to recognize the signal preamble. The performance of Mode S reply signal recognition is enhanced via triple correlations in this method. The theoretical derivation of detection probability is given. The simulations are conducted to indicate that detection probability of the proposed method can approach theoretical value under the expected false alarm probability, and to evaluate the performance of the proposed method and conventional methods such as direct matched filtering, pulse front edge detection and correlation detection with normalized baseband, and to illustrate the advantages of the proposed algorithm.