【作者】 王璇； 郇浩； 陶然； 贾丽娟；

【Author】 Xuan Wang,Hao Huan,Ran Tao,Lijuan Jia Dept.of information and Electronic,Being Institute of Technology,Beijing 100081,China

【机构】 北京理工大学信息与电子学院；

【摘要】 针对高动态环境下GPS(GlobalPositioning System)接收机的接收信号同时具有较大多普勒频率及多普勒频率变化率等问题,提出了一种基于分数阶傅里叶变换的捕获方法,有效提高了捕获概率、缩短了捕获时间。该方法首先根据载波多普勒呈现近似线性调频信号的特点,利用分数阶傅里叶变换进行相干积累;其次,采用了一种新的时间频率调整技术,对相干积累的输出结果进行非相干积累,以进一步提高检测信噪比;最后,根据相干积累与非相干积累的特点,采用了一种高效的积累策略。理论分析和仿真验证表明,本文提出的基于分数阶傅里叶变换捕获方法,解决了传统方法在高动态环境下难以对信号进行长时间相干积累的难题,尤其在低信噪比情况下,更好地提高了接收机的灵敏度、缩短了捕获时间。更多还原

【Abstract】 An acquisition method based on fractional Fourier transform(FRFT) is proposed to solve the problems of GPS(Global Positioning System) receiver,which has larger Doppler frequency and Doppler changing rate under high dynamic environment.The algorithm can improve the acquisition probability and decrease the acquisition time effectively.In the approach,the FRFT is firstly introduced for coherent integration since the carrier Doppler has the same characteristics as chirp signal.Secondly, in order to improve the detectable signal-to-noise ratio(SNR),a new time-frequency adjusting technique is used to implement non-coherent integration with the outputs of coherent integration. Finally,an efficient accumulation strategy is adopted according to the characteristics of coherent integration and non-coherent integration.Theoretical analysis and the simulation results show that the proposed method can be implemented in long time coherent integration which can’t be solved by the traditional methods in high-dynamic environment.Besides,it can also improve the GPS receivers’ sensitivity and decrease the acquisition time,especially when the SNR is low.更多还原