北斗QPSK中频信号及BOC调制信号捕获算法研究

发布时间：2018-06-26 00:32

本文选题：北斗 + QPSK　；参考：《西安电子科技大学》2014年硕士论文

【摘要】：卫星导航系统能够保障国家安全、促进社会发展,并为人民的生产生活带来极大的便利。随着北斗卫星定位导航系统的建设与试运行,北斗系统将逐步成为可以和GPS系统相媲美的GNSS系统之一,能够为地球表面和近地空间的用户提供全天时、全天候、高精度的定位、导航和授时服务。目前,各相关单位竞相研制高性能的北斗导航接收机,而捕获环节是北斗导航接收机设计中的关键环节之一。本文将围绕接收机中的捕获算法问题展开研究,完成了如下几个方面的工作:(1)介绍北斗QPSK信号的信号结构,并对北斗中频信号进行了仿真,研究了北斗中频信号的频谱结构和自相关函数,为后续的捕获算法的仿真提供了可用的仿真信号源。(2)下一代卫星导航信号体制将采用BOC调制方式。BOC信号具有与传统BPSK信号有不同的特点,本文详细讨论了BOC信号、MBOC信号以及AltBOC信号的调制原理及其功率谱特性和自相关函数特性。BOC信号的自相关函数的多峰性为信号捕获带来了新的问题。本文对捕获BOC信号所采用的双边带捕获算法、单边带捕获算法以及BPSK-like捕获算法进行了简要的介绍和分析,并给出了一些仿真结果。(3)捕获概率和算法复杂度可以作为捕获算法性能的衡量指标。本文对北斗信号的捕获过程进行了建模,详细推导了门限与捕获虚警率和噪声功率之间的表达式,分析了捕获概率与积分时间之间的关系。本文还对基本的捕获算法(串行搜索捕获算法,并行频率搜索算法和并行码相位搜索算法)进行了详细的分析和仿真,并对可以减小虚警率的Tong算法进行了介绍。(4)在森林、城市、峡谷及隧道等环境中,由于障碍物的遮挡卫星信号受到了很大程度的衰减,这就需要依赖高灵敏度的捕获算法来捕获信号。常见的提高捕获灵敏度的方法是延长积分时间,本文分析了延长相干积分时间和非相干积分时间所带来的算法性能提升和存在的问题。本文依次介绍了差分相干累积算法,半比特/全比特算法,以及估计导航数据比特的圆周算法。通过仿真分析发现,相同积分时间的条件下,估计导航数据比特的圆周算法具有最高的捕获概率,但是该算法的计算量很大。为了减小算法的计算量,本文利用“先累积后相关”的思想,使用FFT替代相关运算以及采用并行程序结构三个方面对估计导航数据比特的圆周算法进行了优化,改进后算法的计算效率得到了较大的提升。
[Abstract]:Satellite navigation system can guarantee national security, promote social development, and bring great convenience to people's production and life. With the construction and trial operation of the Beidou Satellite Positioning and Navigation system, the Beidou system will gradually become one of the GNSS systems comparable to the GPS system, which can provide all-day, all-weather and high-precision positioning for users of the Earth's surface and near-Earth space. Navigation and time service. At present, the relevant units are competing to develop a high-performance Beidou navigation receiver, and the capture link is one of the key links in the design of the Beidou navigation receiver. In this paper, the acquisition algorithm in receiver is studied, and the following work is accomplished: (1) the signal structure of Beidou QPSK signal is introduced, and the if signal is simulated. The spectrum structure and autocorrelation function of Beidou intermediate frequency signal are studied. It provides a useful signal source for the subsequent simulation of the acquisition algorithm. (2) the next generation satellite navigation signal system will adopt BOC modulation. BOC signal has different characteristics from the traditional BPSK signal. This paper discusses in detail the modulation principle of BOC signal and AltBOC signal, its power spectrum characteristics and autocorrelation function characteristics. The multi-peak of autocorrelation function of BOC signal brings new problems for signal acquisition. This paper gives a brief introduction and analysis of the bilateral band acquisition algorithm, the single sideband acquisition algorithm and the BPSK-like acquisition algorithm, which are used to capture BOC signals. Some simulation results are given. (3) the acquisition probability and the complexity of the algorithm can be used as a measure of the performance of the capture algorithm. In this paper, the acquisition process of Beidou signal is modeled, the expression between threshold and false alarm rate and noise power is derived in detail, and the relationship between acquisition probability and integral time is analyzed. In this paper, the basic acquisition algorithms (serial search, parallel frequency search and parallel code phase search) are analyzed and simulated in detail, and Tong algorithm, which can reduce false alarm rate, is introduced. (4) in forest, In cities, canyons and tunnels, because of the large attenuation of the obstructed satellite signal, it is necessary to rely on the high sensitivity acquisition algorithm to capture the signal. The common method to improve the acquisition sensitivity is to extend the integral time. In this paper, the performance improvement and the existing problems of the algorithm brought by the extended coherent integral time and incoherent integral time are analyzed. In this paper, the differential coherent cumulation algorithm, the half-bit / full-bit algorithm, and the circle estimation algorithm for navigation data bits are introduced in turn. The simulation results show that the circumference algorithm for estimating navigation data bits has the highest acquisition probability under the same integral time, but the computation of the algorithm is very large. In order to reduce the computational complexity of the algorithm, this paper optimizes the circular algorithm for estimating navigation data bits by using FFT to replace correlation operation and parallel program structure by using the idea of "accumulate first and then correlate". The computational efficiency of the improved algorithm is greatly improved.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN967.1;TN911.3

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