Research And Implementation Of Weak Signal Acquisition In B1Band For BD Ⅱ

BeiDou Navigation Satellite System (BDS) has covered most parts of Asia Pacificwith regional service capabilities, which is independent operation with proprietaryintellectual property rights of our country.With the rapid increase of location serviceapplications based on BDS, the technology of navigation and positioning in indoor andurban environments has become a hot research topic, and the capture of weak signal isone of the key techniques.In order to solve the problem of the weak signal acquisition on the B1spectrum ofthe second generation of Beidou, this paper analyzes Doppler frequency shift, itsinfluence on the ranging code, and the effects on coherent integration from themodulation with Hoff code. Then, this article presents the optimization differencecoherence estimation method and NH code modulate local pseudo-code coherencemethod combining with the capture of weak signal about GPS and the theoreticalknowledge of BDS. In the MATLAB environment, the proposed methods are verifiedand compared with the actual sampling data. The correct code phase and Dopplerfrequency offset are acquired. The results show that the proposed methods are effectiveand practical, of which the effects are more significant than that of the ordinary method.Finally, this paper introduces the hardware environment and software methodbased on DSP development platform, and the steps of NH code modulate localpseudo-code difference noncoherent method with its verification.