基于PMF-FFT的高动态导航信号捕获设计与实现

发布时间：2018-04-30 10:14

本文选题：高动态 + 导航信号　；参考：《电子科技大学》2014年硕士论文

【摘要】：GPS(全球定位系统)是新一代卫星导航定位系统,在民用和军事等方面有着广泛应用。而导弹、运载火箭等载体大都是工作在高动态环境,具有较大的运动速度和加速度,导航接收机所接收到的信号和本地信号之间存在较大的多普勒频偏和伪码延时,对信号的捕获提出很高的技术要求。本文主要针对高动态环境下导航信号的捕获展开讨论,具体研究内容如下:本文先对GPS信号的结构特性进行分析,在研究导航信号捕获基本原理的基础上建立PMF-FFT捕获算法的数学模型。针对该算法存在的扇贝损失问题,分析和研究数据补零和加窗补偿等两种方法,有效消除扇贝损失的影响。通过建立高动态环境下的导航信号数学模型,分析载波多普勒频偏及其变化率和伪码延时,研究伪码延时和载波多普勒频偏对相干输出带来的影响。在此基础上对PMF-FFT的捕获系统中各项参数做详细的分析设计,并提出高动态环境下基于改进的PMF-FFT算法的捕获方案,通过MATLAB仿真实验表明,此方案的捕获性能良好。考虑FPGA芯片内部资源,提出硬件可实现的高动态捕获方案。采用自顶而下的设计方法,将整个捕获系统划分为各个子模块,并对其输入激励验证功能。采用改进的匹配滤波器结构减小芯片存储资源消耗;加入双D触发器同步电路解决跨时钟域异步问题;采用截取高位的方式对每个模块的输入输出端口做最佳精度定点量化处理,尽量做到资源优化的同时保证量化损失不影响捕获性能;通过状态机的控制将各个子模块连成一个有机整体。最后搭建高动态捕获测试闭环系统。模拟多种高动态运动场景,测试结果表明,本文捕获方法适用于20g的高动态环境。
[Abstract]:GPS (Global Positioning system) is a new generation of satellite navigation and positioning system, which is widely used in civil and military fields. However, most of the carriers, such as missiles and launch vehicles, work in high dynamic environments, with high velocity and acceleration, and there is a large Doppler frequency offset and pseudo-code delay between the signals received by the navigation receiver and the local signals. High technical requirements for signal acquisition are put forward. In this paper, the acquisition of navigation signals in high dynamic environment is discussed. The main contents are as follows: firstly, the structural characteristics of GPS signals are analyzed. On the basis of studying the basic principle of navigation signal acquisition, the mathematical model of PMF-FFT acquisition algorithm is established. Aiming at the scallop loss problem in this algorithm, two methods, data compensation and window compensation, are analyzed and studied to eliminate the effect of scallop loss. By establishing the mathematical model of navigation signal in high dynamic environment, the carrier Doppler frequency offset and its variation rate and pseudo code delay are analyzed, and the influence of pseudo code delay and carrier Doppler frequency offset on coherent output is studied. On this basis, the parameters of PMF-FFT capture system are analyzed and designed in detail, and the capture scheme based on improved PMF-FFT algorithm in high dynamic environment is proposed. The simulation results of MATLAB show that the capture performance of this scheme is good. Considering the internal resources of FPGA chip, a high dynamic capture scheme is proposed. Using the top-down design method, the whole capture system is divided into each sub-module, and the input excitation verification function is given. The improved matched filter structure is adopted to reduce the memory consumption of the chip and the synchronous circuit of double D flip-flop is added to solve the asynchronous problem across the clock domain. The input and output ports of each module are processed with the best precision fixed-point quantization in the way of intercepting the high position, so as to optimize the resource and ensure that the quantization loss does not affect the capture performance. Each sub-module is connected into an organic whole by the control of the state machine. Finally, a high dynamic capture test closed loop system is built. The simulation results show that the capture method is suitable for 20g high dynamic environment.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN967.1

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