Research And Implementation Of Acquisition Technology In B1I Signal Of BeiDou ?

Beidou Second Generation Satellite Navigation System which developed independently by China has been successfully put into operation. The development of Beidou satellite navigation receiver is also booming, and the signal acquisition is the crucially first step. The research on signal acquisition technology mainly concentrates to improve on the performance of acquisition accuracy and sensitivity of the GPS satellite signal, but the characteristic of frequent bit polarity reversal in Beidou II B1 I signal leads to the acquisition algorithm of GPS satellite signal being unsuited to Beidou navigation receiver. Therefore, the study of the signal acquisition technology applying in Beidou II B1 I signal has an important significance for the development of navigation receiver.Firstly, the structure of B1 I signal and the traditional acquisition algorithms are analyzed and researched. To avoid the influence of frequent bit polarity reversal in B1 I signal, the rough acquisition algorithm of time domain parallel is designed, and the performance analysis and experimental verification of the algorithm are carried out.Aiming at the problem of low precision of carrier Doppler frequency which is obtained by rough acquisition, the fine acquisition algorithm of carrier frequency which combines the numerical approximation algorithm with the Chebyshev linear least square curve fitting algorithm is proposed. In addition, the performance analysis and experimental verification of the algorithm are carried out, the experimental results show that the proposed algorithm can improve the estimation accuracy of the carrier frequency to 20 Hz.To slove the problem of signal acquisition for urban, indoor and other weak signal environments, the differential non coherent integration algorithm for GEO satellites and the coherent integration algorithm modulated with NH code for IGSO/MEO satellites are designed, and the validity of the algorithm which can inprove 7dB signal gain is verified by the experimental test of weak signal.Finally, a signal acquisition system which is made up of the rough acquisition algorithm, the fine acquisition algorithm and the weak signal acquisition algorithm is realized on the navigation receiver development platform based on FPGA and DSP. Besides, the performance of the acquisition system is tested using the signal generated by the Beidou satellite signal simulator, and the results not only verify the correctness of the hardware implementation but also show that the acquisition system can perfom high precision and high sensitivity.