全球定位系统预解扩延时相乘捕获算法

针对全球定位系统(GPS)信号捕获中延时相乘捕获算法检测率低的问题,提出一种预解扩延时相乘捕获算法,以提高信号捕获的检测率.首先对信号进行码相位搜索和解扩,然后在延时相乘操作前、后分别使用窄带滤波器来减小噪声带宽和功率,以提高信噪比和检测率.通过蒙特卡罗方法对其检测率特性进行仿真.结果表明,相比于延时相乘捕获算法,该算法检测率明显提高,并且保持了捕获过程中不受频偏影响的优势.在软件接收机中应用该算法对GPS信号成功捕获,证明了算法的有效性.

A Pre-Despreading Delay-and-Multiplication Method for Global Positioning System Signal Acquisition

A pre-despreading delay-and-multiplication (PDDM) acquisition method was proposed to improve the probability of detection of the delay and multiplication acquisition method for global positioning system (GPS) signal. The PDDM first searches for the pseudo random code phase to de-spread the signal; then two narrow-band filters are applied before and after the delay-and-multiplication operation to reduce the noise power. The signal to noise ratio and the probability of detection are improved consequently. The Monte Carlo simulation shows that while keeping the advantage of not being affected by the frequency offset, the PDDM improves the probability of detection significantly compared to the delay-and-multiplication acquisition method. The effectiveness and practicality of the PDDM was examined by applying it to a software receiver. The GPS signal was successfully acquired.Key words：