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在GPS微弱信号捕获算法设计中,为提高捕获灵敏度,采用相干积分与非相干积分结合的方式消除数据码长度对相干积分增益的影响,采用差分相干积分减小非相干积分中的平方衰耗。为了提高信号捕获速度和精度,利用FFT工具进行伪码与载波频率捕获,采用延迟锁定环(DLL)与锁相环(PLL)实现GPS微弱信号的跟踪。最后对GPS微弱信号的捕获跟踪算法进行仿真实现。应用结果表明:通过仿真技术能有效地复现出捕获和跟踪载噪比为25dB.Hz-1的GPS微弱信号,差分相干积分捕获灵敏度比相干-非相干积分高0.8dB,频率捕获误差小于1.25Hz,码捕获误差小于0.1码元。
In the design of GPS weak signal acquisition algorithm, in order to improve the acquisition sensitivity, the coherent integration and non-coherent integration are used to eliminate the effect of data length on the coherent integration gain. The coherent integration is used to reduce the squared attenuation in the noncoherent integration. In order to improve the speed and accuracy of signal acquisition, the FFT tools are used to capture the pseudo-code and carrier frequency, and the GPS weak signals are tracked by DLL and PLL. Finally, the acquisition and tracking algorithm of GPS weak signal is simulated. The simulation results show that the acquisition and tracking of GPS weak signal with carrier-to-noise ratio of 25dB.Hz-1 can be effectively reproduced by simulation technology. The differential coherent integration acquisition sensitivity is 0.8dB higher than coherent-non-coherent integration and the frequency acquisition error is less than 1.25 Hz, code capture error less than 0.1 symbol.