一种新型的GPS弱信号精捕获方法

Novel fine acquisition method for weak GPS signal

为提高GPS接收机在低信噪比环境中的捕获精度和灵敏度,提出了一种新的弱信号精捕获算法。该算法采用差分相干积分缓解平方损耗,并利用积分结果的相位信息修正载波频率,使其估计精度不再受到频移搜索步长的限制。此外,该算法根据载波多普勒和码多普勒的比例关系,直接对本地码相位进行校正,保证了信号积累时间较长时不同相关峰之间的重叠性,有助于提高捕获灵敏度并能够得到接收信号末端精确的码相位。仿真结果表明,载波频率和码相位的估计误差分别小于20 Hz和1个采样点,在给定的信号积累时间下,本地码相位校正对捕获灵敏度的提升可达3.2 d B。

To improve the acquisition accuracy and sensitivity of GPS receiver in low signal-to-noise ratio（SNR） environment, a new kind of acquisition method for weak signal is proposed.This method makes use of differential coherent integration to reduce power loss, and breaks the restriction of searching step size on the estimation accuracy of carrier Doppler shift by utilizing the phase information of integration results.Moreover, based on the relationship between carrier and code Doppler shifts, this method can directly amends the local code phase.As a result, it ensures different correlation peaks＇ overlap with each other and can obtain accurate code phase of the received signal.Simulation results show that the estimation errors of carrier Doppler shift and code phase can be kept to less than 20 Hz and one sampling point respectively, and, in a given case, the acquisition sensitivity is improved by about 3.2 d B.