Browsing by Author "Chen, Shaohua"

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    Improvement of Carrier Phase Tracking Based on a Joint Vector Architecture
    (2017-07-30) Chen, Shaohua; Gao, Yang
    Carrier phase measurements are essential to high precision positioning. Usually, the carrier phase measurements are generated from the phase lock loop in a conventional Global Navigation Satellite System (GNSS) receiver. However there is a dilemma problem to the design of the loop parameters in a conventional tracking loop. To address this problem and improve the carrier phase tracking sensitivity, a carrier phase tracking method based on a joint vector architecture is proposed. The joint vector architecture contains a common loop based on extended Kalman filter to track the common dynamics of the different channels and the individual loops for each channel to track the satellite specific dynamics. The transfer function model of the proposed architecture is derived. The proposed method and the conventional scalar carrier phase tracking are tested with a high quality simulator. The test results indicate that carrier phase measurements of satellites start to show cycle slips using the proposed method when carrier noise ratio is equal to and below 15 dB-Hz instead of 21 dB-Hz with using the conventional phase tracking loop. Since the joint vector based tracking loops jointly process the signals of all available satellites, the potential interchannel influence between different satellites is also investigated.
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    Improving Low-Cost GNSS Receiver Carrier Phase Tracking for High Precision Applications
    (2017) Chen, Shaohua; Gao, Yang
    Low-cost Global Navigation Satellite System (GNSS) receivers capable of high precision positioning have drawn increased attentions due to strong application demands. High-precision positioning techniques, such as Real-Time Kinematic and Precise Point Positioning, require the use of carrier phase measurements. High precision positioning solution however is currently not available in most low-cost GNSS receivers in harsh environments due to the poor quality of carrier phase measurements limited by the antenna and the oscillator quality and the lack of proper tracking algorithms. The research in this thesis aims at solving several challenging issues of carrier phase tracking of low-cost GNSS receivers. To improve carrier phase tracking sensitivity performance, a joint vector phase lock loop (VPLL) architecture is proposed and implemented in a software receiver. The transfer function model of the joint VPLL is analysed. To assess the sensitivity performance, a simulator test is conducted and the results show that the carrier phase tracking sensitivity using the proposed method is improved about 6 dB. The influence of vibration-induced oscillator phase noise on carrier phase tracking is analysed. Using hardware simulator and field tests, the performance of both the joint VPLL and scalar tracking are analysed and compared under oscillator vibration conditions. The results show that the proposed joint VPLL can improve the robustness of the carrier phase tracking compared to the scalar PLL. The performance of the joint VPLL in carrier phase prediction and tracking sensitivity is further investigated under kinematic mode. The phase prediction method based on the joint VPLL is implemented and its performance is compared with a conventional prediction strategy. A field vehicle test shows that the prediction performance of the proposed method is much better. The sensitivity of the joint VPLL under kinematic mode is analysed and compared with the scalar tracking. Based on the characteristics of the joint VPLL, an adaptive joint VPLL has been proposed for high dynamic applications. The performance of the proposed adaptive joint VPLL is analyzed with a simulation and a field test. The results demonstrate the better performance of the proposed adaptive joint VPLL compared to the joint VPLL without adaptive techniques.