Beidou Key Generic Technology Of Second Generation Satellite Navigation Receiver

Global navigation satellite system (GNSS) is an all-weather, all-space navigation system, which has significant advantages over other navigation systems. Since its significant meaning to the community, national economy and military, GNSS has become the focus of a race in space technology among some leading countries, including China. BD-Ⅱis a new generation satellite system under development, which has been taking up with Chinese independent innovation.It will contribute to the sustainable development of national economy and play an import role in the national defense in the future.As an important part of the satellite navigation system, receiver is a key factor of navigation industrialization.Along with the development of BD-Ⅱsatellite navigation system,researches on BD-Ⅱreceivers’key technologies are very demanding. This paper focuses on common technologies in signal acquisition, tracking loop and user position calculation modules of BD-Ⅱreceiver,and presents some new methods to improve performance and reduce computation complexity.In order to determine signal parameters of visible satellites in the sky, the first task of receiver is to acquire satellite signals.Since short acquisition time with low computation complexity is preferred, a parallel differential correlation acquisition algorithm in time domain is presented in this paper, which can acquire multi-satellite signals at the same time by reusing the correlation results. We also analyze computation complexity of the proposed algorithm, comparing with traditional correlation algorithm, two modified correlation algorithms in time domain and the FFT-based correlation algorithm in frequency domain.Analysis and simulation results indicate that our algorithm has advantages in computation complexity, and its computation complexity does not increase while oversampling rate increases.After acquisition, a tracking loop is used to stably track the satellite signals.The idea of 1-bit analog-to-digital-conversion (ADC) has been widely implemented in low-cost satellite navigation receivers and low-power satellite communications due to its efficiency in bit wise processing and free from automatic gain control.The accuracy of traditional arctangent phase discriminator in tracking loop degrades greatly because of 1-bit ADC.To solve this problem,a novel phase discriminator called as robust digital phase discriminator (RDPD) is presented in this paper. Different from the existing digital phase discriminator (DPD), the proposed RDPD achieves higher precision and more robustness. Analysis and simulation results indicate the proposed RDPD has superior precision than traditional arctangent phase discriminator (APD) and DPD whenever signal noise ratio(SNR) is high or low.For more widely used multi-bits quantified front-end, we propose a novel dynamic model of Doppler frequency and phase firstly, called as a polynomial prediction model (PPM).Then a new self-validating optimal filtering method, based on PPM and the unscented Kalman filter (UKF), is developed for frequency and phase estimates in carrier tracking loop of a receiver. The analytical results show that the proposed method can effectively track the Doppler frequency and phase whatever the motion between the transceivers is. The analysis is verified by the simulations and experimental results of a real live GPS receiver, which show that the proposed method is superior to most of those reported in literatures.The final task of satellite navigation receiver is to calculate user position.When user equivalent range errors (UERE) have different distributions, the weighted least-square (WLS) algorithm has better performance than the least-square (LS) algorithm. But in practice, the covariance matrix of UERE is not known.In this paper, an iterative asymptotic unbiased heteroscedastic variance estimation method is presented, which is suitable for measurement noise with arbitrary possibility distributions. With estimation results of this method, the WLS algorithm can work in practice. Simulation results verify the performance and effectiveness of our method.At last, we develop a real-time global position system (GPS) receiver based on "font-end+FPGA+PC" architecture to verify parts of algorithms proposed in this paper, and hope this receiver to be a good design reference for BD-Ⅱreceiver in the future.