一种基于FFT的弱信号快速捕获算法

A Fast Weak-signal Acquisition Algorithm Based on FFT

为提高弱信号环境下导航信号的捕获灵敏度,可通过增加相干积分时间和非相干累加次数提高处理增益。针对传统高灵敏度捕获算法运算量大、非相干累加带来平方损耗等问题,提出了一种基于FFT的弱信号快速捕获算法,首先对输入信号按伪码长度进行块叠加之后再做FFT循环相关运算来降低相干计算量;其次,采用差分相干累加算法消除传统算法的平方损耗;最后,对捕获的载波频率进行了精化处理以防止后续跟踪失锁,提高了载波频率分辨率。仿真结果表明,改进算法较传统算法在弱信号捕获性能上具有更快的捕获速度,并且在捕获精度相同情况下,提高了弱信号的捕获能力。

In order to enhance the acquisition sensitivity of navigation signal in weak signal environment,a method of increasing the coherent integration time and the number of non-coherent accumulation can improve the processing gain. For the traditional high sensitivity acquisition algorithm having large amounts of computation,and non-coherent accumulation algorithm binging square loss and other issues,this paper proposes a fast weak-signal acquisition algorithm based on Fast Fourier Transform（FFT）. Firstly,the input signals get blocks superposition according to the pseudo code length,then FFT circulation related operations is obtained to reduce the coherence of calculation.Secondly,the differential coherent accumulation algorithm is used to eliminate the square loss of traditional algorithm.Finally,in order to prevent the follow-up tracking from losing lock,the carrier frequency is refined,which improves the carrier frequency resolution in the elaboration of processing. Simulation results show that the proposed algorithm has faster capture speed than traditional algorithm on the performance of weak signal acquisition,and it improves the ability of weak signal acquisition under the same circumstances accuracy.