北斗接收机基带信号处理算法关键技术研究

发布时间：2019-04-24 20:22

【摘要】：目前,全球卫星导航系统(GNSS,Global Navigation Satellite System)的发展日新月异,已成为发达国家和部分发展中国家空间领土、科技水平和军事博弈的重要战场,美国的GPS(Global Positioning System)、俄罗斯的GLONASS、欧洲的GALILEO、中国的北斗卫星导航系统(BeiDou Navigation Satellite System)等在GNSS中占有重要地位。北斗系统经过长足的发展,目前已经发展到实现亚太地区的定位、导航和短报文通信全覆盖,提供给授权用户和开放用户多种用户体验,支持大批量的用户实现较为精密的定位和导航服务,并计划到2020年实现全球覆盖。但是随着服务领域的日益增多,用户对定位导航精度和速度要求的不断提升,接收机所处恶劣环境的不断增多,都给各系统的发展提供了重要机遇,也带来了巨大挑战,因此研究定位导航接收机基带信号处理算法,提高接收机定位导航性能具有重要的现实意义和巨大发展空间。北斗接收机是北斗系统在用户端的重要平台,用户接收卫星信号,到最终完成定位导航解算,生成定位导航数据或完成其他辅助功能都是在接收机这一层面实现。各系统在不断优化发展中提高导航定位性能,常用的改进信号体制方法涉及全局规划,较难实现;优化天线选址受地形影响较大;创新天线设计带来较大的硬件损耗。本文主要研究北斗接收机基带信号处理中捕获和跟踪两个重要信号处理过程的优化和改进,先后详细分析了北斗系统定位原理、信号构成、系统组成和接收机工作原理,北斗接收机的捕获原理,以及捕获领域国内外研究现状。针对城市环境中干扰信号多,对北斗系统捕获卫星信号带来的影响,本文提出了基于小波变换的北斗系统抗干扰捕获算法,首先对接收信号进行相关积分和差分累加,使用Meyer小波进行分解,而后比较分解后各频段的能量,通过比较结果确定窄带噪声所在频带,将噪声所在频带的系数进行衰减,最后重构信号从而实现窄带干扰的剔除。实验仿真证明该方法能够实现单天线情况下抵抗窄带连续波干扰,接收机捕获增益平均提高5dB。同时,针对城市高楼林立的狭窄街道环境,北斗接收机接收卫星信号常常被遮挡,导致跟踪环路失锁而不能正常解算导航数据的问题,本文提出了基于改进的扩展卡尔曼滤波器的矢量跟踪算法,通过耦合各通道的信号特征,实现强信号辅助弱信号跟踪,从而在卫星信号被遮挡的情况下依然保持较为精准的定位。实验验证,在城市街道环境中,北斗接收机接收可见星数量不足4颗时,本文算法依然能实现较为精准的定位。本文在改进接收机基带信号处理层面,区分捕获和跟踪两个过程,有针对性地给出了每个过程算法的优化和改进,在不增加硬件损耗和算法复杂度的前提下提高了接收机定位解算的速度和精度,为北斗接收机软件优化提供了一定的借鉴和参考。
[Abstract]:At present, with the rapid development of global satellite navigation system (GNSS,Global Navigation Satellite System), it has become an important battlefield of space territory, scientific and technological level and military game between developed and some developing countries, the GPS (Global Positioning System), of the United States Russia's GLONASS, Europe's GALILEO, China's Beidou Satellite Navigation system (BeiDou Navigation Satellite System) plays an important role in GNSS. After considerable development, Beidou system has now developed to realize the positioning of the Asia-Pacific region, navigation and short message communication coverage, providing a variety of user experiences for authorized and open users. Support a large number of users to achieve more sophisticated positioning and navigation services, and plans to achieve global coverage by 2020. However, with the increasing number of service areas, the increasing requirements of users for positioning and navigation accuracy and speed, and the increasing number of harsh environments for receivers, all provide important opportunities for the development of each system, and also bring great challenges to the development of each system. Therefore, studying the baseband signal processing algorithm of the positioning and navigation receiver, and improving the performance of the positioning and navigation of the receiver has important practical significance and huge development space. Beidou receiver is an important platform of Beidou system at the client end. When the user receives the satellite signal, finally completes the positioning and navigation solution, generates the positioning and navigation data or completes other auxiliary functions, it is realized at the receiver level. In the continuous optimization and development of each system, the navigation and positioning performance is improved, and the commonly used improved signal system method involves global planning, which is difficult to realize; the optimization of antenna location is greatly affected by the terrain; and the innovative antenna design brings greater hardware loss. In this paper, the optimization and improvement of acquisition and tracking two important signal processing processes in Beidou receiver baseband signal processing are studied. The positioning principle, signal composition, system composition and receiver working principle of Beidou system are analyzed in detail. The acquisition principle of Beidou receiver and the research status in the field of acquisition at home and abroad. In view of the influence of many interference signals in urban environment on the acquisition of satellite signals by Beidou system, this paper presents an anti-jamming acquisition algorithm for Beidou system based on wavelet transform. The Meyer wavelet is used to decompose, and then the energy of each band is compared. The frequency band of narrow band noise is determined by comparing the results, and the coefficients of the band of noise are attenuated. Finally, the signal is reconstructed to eliminate the narrowband interference. The simulation results show that the proposed method can resist narrow band continuous wave interference in the case of a single antenna, and the acquisition gain of the receiver can be increased by 5 dB on average. At the same time, aiming at the narrow street environment with high buildings in the city, the Beidou receiver is often blocked from receiving satellite signals, which leads to the problem that the tracking loop is out of lock and the navigation data can not be solved normally. In this paper, a vector tracking algorithm based on the improved extended Kalman filter is proposed. By coupling the signal characteristics of each channel, strong signal-assisted weak signal tracking is realized. Thus, when the satellite signal is occluded, the location is still more accurate. Experimental results show that when the number of visible stars received by the Beidou receiver is less than 4 in the urban street environment, the algorithm in this paper can still achieve more accurate positioning. In this paper, in improving the receiver baseband signal processing level, the acquisition and tracking processes are distinguished, and the optimization and improvement of each process algorithm is given. Without increasing the hardware loss and the complexity of the algorithm, the speed and accuracy of the positioning solution of the receiver are improved, which provides some reference for the software optimization of the Beidou receiver.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN967.1

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