极低信噪比环境下的P码二维直接捕获改进算法  

An Improved Algorithm for P-Code Two Dimension Direct Capture in Extra-low SNR Condition

作　　者：卢虎[1,2] 廉保旺[1] 沈淑渭[2] 王聪敏[3] 

机构地区：[1]西北工业大学电子信息学院,陕西西安710072 [2]空军工程大学理学院,陕西西安710051 [3]空军工程大学导弹学院,陕西三原713800

出　　处：《空军工程大学学报（自然科学版）》2009年第5期45-49,共5页Journal of Air Force Engineering University(Natural Science Edition)

基　　金：陕西省自然科学基础研究计划资助项目(SJ08F12);航空科学基金资助项目(20090196004);陕西省电子信息系统综合集成重点实验室基金资助项目(200908A)

摘　　要：针对极低信噪比环境下GPS系统中超长精密测距码(P码)直接捕获的问题,传统的滑动相关法已无法满足P码直接快速捕获的要求,分析了现有常用FFT校频快速捕获技术性能以及FFT运算长度与信号输入信噪比的关系,指出了现有算法的不足,在此基础上提出一种在极低信噪比环境下的码捕获新方法———利用非对称FFT计算和视频积累相结合的P码直接捕获改进算法,仿真结果表明,即使在-35 dB的极低信噪比情况下,算法也可快速实现P码的直接捕获,最后给出算法的FPGA实测结果,进一步验证了算法的可实现性及有效性。This paper investigates the synchronization of digitalized DSSS receiver in high - dynamic and Extra - low SNR environment, presents and realizes the methods of direct P - code acquisition in GPS. This paper introduces several conventional code acquisition methods and the reason why they are not fit for direct P - code acquisition. In the precondition of good cross correlation and partial autocorrelation of P - code, a direct P - code acquisition scheme based on Unsymmetrical FFT is proposed and realized in FPGA. Compared with the conventional slipping con＇elation method, the time of direct P - code acquisition scheme based on Unsymmetrical FFT is reduced by more than ten times and the calculation is reduced rapidly. It＇s useful for other direct long PRN codes acquisition.

关 键 词：P码直接捕获 局部相关 非对称FFT 视频积累 

分 类 号：TN927.23[电子电信—通信与信息系统]