Research on Key Technology of Low-Cost GNSS Receiver in Harsh Environment

Abstract

The global navigation satellite system (GNSS) is playing a uniquely significant role in the navigation of military and civil since it is superior in providing high-precision, all-weather, all-time positioning, navigation and timing solutions. Whereas, the GNSS signals are vulnerable, especially in the high-dynamic and signal-fading scenarios. This thesis aims to achieve the research goal of developing the low-cost GNSS receiver in harsh environments by investigating three key techniques including standalone baseband signal processing, vector tracking, and ultra-tightly coupled GNSS/inertial navigation system (INS) integration. Firstly, in terms of the high-dynamic and weak GNSS signal, three baseband processing algorithms are investigated to enhance the resistance towards such tricky issue on the receiver side. At first, an improved acquisition algorithm is proposed using the fractional Fourier transform (FRFT). Hence, the acquisition performance has been improved. Then, a fast frequency rate estimation algorithm is proposed based on the FRFT. The proposed algorithm has improved the estimation accuracy and the computational efficiency of the digital FRFT (DFRFT). Besides, a carrier tracking algorithm is proposed based on the extended Kalman filter (EKF) with the dual adaptive covariance matrices. It has achieved the higher tracking sensitivity and the lower tracking error. Secondly, in terms of the signal fading caused by the various blockages on the ground, two vector tracking algorithms are investigated to improve the navigation performance and reduce the inherent error in the vector receiver. On the one hand, an improved cascaded vector tracking algorithm is proposed using an optimal parameter configuration. The proposed algorithm has achieved the higher performances in tracking and positioning. On the other hand, a time-correlated error suppressed vector tracking algorithm is proposed by introducing Allan variance. The proposed algorithm has increased the positioning accuracy of the vector receiver. Finally, in terms of the issue that sharp power reduction occurs in multiple channels, the adaptive cascaded ultra-tightly coupled GNSS/consumer-level INS integration algorithms are proposed by using the vector tracking information. The proposed algorithm has raised the tracking sensitivity, navigating solution availability, and has increased the carrier-based high-precision positioning performance of the GNSS receiver.