Research On The Key Techniques Of Bei Dou Receiver

In recent years, our country is building a Beidou 2nd generation regional satellite navigation system which can extend to the world, the system will realize navigation positioning, measuring speed, timing and the message communication function in and around China. The positioning accuracy and capture sensitivity of beidou receiver are widely focused in by scholars. In this paper, a detailed study of multi-frequency combination positioning and code capture algorithm under the condition of low signal-to-noise ratio and the big doppler frequency offset is made, the following research contents are completed.1. This paper discusses the signal of beidou navigation system, with analysis of beidou navigation positioning observation model and error sources. Capture and positioning principle of beidou navigation receiver are introduced.2. The Optimal selection coefficients of beidou multi-frequency combination have been studied. Aiming at beidou receiver multi-frequency combination observations have a demand of three performance including long wavelength, low noise and less ionospheric disturbance, this paper analyses the multi-frequency combination selection coefficients under the condition of a single performance demand and further analyzes mutual restriction relations of three performance including long wavelength, low noise and less ionospheric disturbance,proposes the optimal coefficients of dual-frequency and triple-frequency combination on comprehensive performances. In addition, this paper proposes a new algorithm of using least squares method to solve coefficients of multiple frequency carrier phase pseudorange linear combination by analyzing the function extreme value method with conditions of Geometry-Based and Geometry-Free model.3. The beidou multi-frequency pseudorange single point positioning and precision positioning have been studied. Based on the optimal combination coefficients of beidou dual-frequency and triple-frequency, firstly, the multi-frequency pseudorange single point positioning is analysed, secondly, the multi-frequency precision positioning accuracy is analysed. Simulation results show that the precision of the singlefrequency has advantages over the dual-frequency without the ionosphere combination and that the precision of the triple-frequency is equal to the dual-frequency with good conditions. However, the dual-frequency and the triple-frequency pseudorange single point positioning can improve the accuracy of beidou pseudorange single point positioning with poor conditions. Horizontal direction is 0.074 m and height direction is 0.153 m of precision positioning accuracy at B3 single frequency, but precision positioning accuracy of triple-frequency combination with 0.068 m at horizontal direction and 0.062 m at height direction has advantages over B3 single frequency. Precision positioning of B3 single frequency and B1B2B3 triple-frequency have achieved good results.4. A code capture algorithm under the condition of low signal-to-noise ratio and the big doppler frequency offset has been studied. This paper proposes an improved partial matching filter FFT code capture algorithm which is realized by coherent accumulation and non-coherent accumulation of multiple code elements to increase the signal gain on the basis of an partial matching filter FFT code capture algorithm. The improved algorithm realizes fully capturing satellite navigation signal long codes at-40 d B signal-to-noise ratio and resisting 5 KHz doppler frequency offset.