GPS信号延时相乘捕获算法的检测率仿真  

Simulation of Probability of Detection for the Delay-and-Multiply Method in GPS Signal Acquisition

作　　者：范江涛[1,2] 马冠一[1] 

机构地区：[1]中国科学院国家天文台,北京100012 [2]中国科学院研究生院,北京100049

出　　处：《天文研究与技术》2013年第1期30-35,共6页Astronomical Research & Technology

基　　金：国家重点基础研究发展计划"973"项目(2007CB815501);中国科学院新兴与交叉学科布局试点项目(KJCX2-EW-J01);中国科学院知识创新工程重要方向项目(KGCX2-EW-4071)资助

摘　　要：对全球定位系统(Global Positioning System,GPS)信号捕获中的延时相乘捕获算法的检测率进行了仿真分析。延时相乘捕获算法消除了多普勒频偏的影响,适用于高动态环境下信号的捕获。但算法的缺点是延时相乘操作增加了噪声量,从而降低了信噪比,影响检测性能。针对算法的缺点,通过理论计算与蒙特卡罗方法仿真,分析了算法中检测变量的噪声分布。从仿真结果看,检测变量的噪声符合高斯分布。根据噪声分布,计算了在不同信号载噪比(C/N0)条件下延时相乘捕获算法的检测率与虚检率的关系。通过减小噪声带宽和延长积分时间,可以提高算法的检测率。The first step of the working process of a GPS receiver is signal acquisition,which is to detect the presence of the GPS signal and obtain necessary parameters for the tracking module.Many acquisition methods have been developed for various applications.Most of them require large numbers of steps to implement two-dimensional search for code-phase and frequency offset.The performance of these methods is affected by the Doppler frequency of the signal.The Delay-and-Multiply acquisition method avoids the effect of the Doppler frequency,and adopts a one-dimensional search process which significantly reduces searching steps.The method is thus suitable to be used in highly dynamic situations with high Doppler frequencies.However,the method has a disadvantage of introducing additional noise in the Delay-and-Multiply operation so as to lower the signal-to-noise ratio（SNR） and deteriorate the detection performance.This paper studies the performance of the Delay-and-Multiply acquisition method for GPS signal.Monte Carlo simulations are used to analyze the probability density functions of detected noise and signal.We have found that the distribution of noise is nearly Gaussian.The paper further calculates the probability of detection（Pd） and the probability of false alarm（Pf） according to the distributions of noise and signal,and presents the relations of Pd and Pf for different values of C/N0.Compared to the traditional acquisition methods,the Pd is much lower under the same values of Pf and C/N0 because of stronger noise.In order to improve the Pd,the noise is reduced by lowering the sampling frequency and extending the integration time.Simulation results show that the performance of the Delay-and-Multiply acquisition method is improved following the noise reduction.

关 键 词：GPS 延时相乘捕获算法 检测率 噪声分布 蒙特卡罗仿真 

分 类 号：TN967.1[电子电信—信号与信息处理]