Architecture design of GPS software receiver and implementation of its acquisition algorithm with fine frequency estimation

The design of a global positioning system （GPS） software receiver is introduced. This design uses the concept of software radio, and it consists of the following parts： front-end, acquisition, tracking, synchronization, navigation solution and some assisting modules. In the acquisition module, the acquisition algorithm based on circular correlation is utilized. The input data and the local code are converted into the frequency domain by means of the fast Fourier transform （FFT）. After performing circular correlation, the initial phase of the C/A code can be obtained and the cartier frequency can be found in 1 kHz frequency resolution, which is too coarse to use for the tracking loop. In order to improve the frequency resolution, the fine frequency estimation through a phase relationship is then achieved, by which, the frequency resolution is improved dramatically. Experiments show that the inaccuracy of the carrier frequency can be estimated within a few hertz by the fine frequency estimation method, and the fine frequency attained can be directly used for the tracking loop.

Design and realization of synchronization circuit for GPS software receiver based on FPGA

With research on the carrier phase synchronization and symbol synchronization algorithm of demodulation module, a synchronization circuit system is designed for GPS software receiver based on field programmable gate array （FPGA）, and a series of experiment is done on the hardware platform. The result shows the all-digital synchronization and demodulation of GPS intermediate frequency （IF） signal can be realized and applied in embedded real-time GPS software receiver system. It is verified that the decision-directed joint tracking algorithm of carrier phase and symbol timing for received signals from GPS is reasonable. In addition, the loop works steadily and can be used for receiving GPS signals using synchronous demodulation. The synchronization circuit for GPS software receiver designed based on FPGA has the features of low cost, miniaturization, low power and real-time. Surely, it will become one of the development directions for GPS and even GNSS embedded real-time software receiver.

Improved Circular Correlation Methods for Acquisition in Software GPS Receiver

In this paper the authors explore the Global Positioning System （GPS） signal acquisition and tracking algorithms used in software GPS receiver. Acquisition time is the most important parameter in evaluating the performance of a software GPS receiver in terms of its speed. A trade-off study is done to seek a good balance between the acquisition accuracy and the processing time. The frequency-domain acquisition method by circular correlation, used in a software GPS receiver, has been improved by studying the power spectrum of the Coarse Acquisition （C/A） code alone. The analysis of C/A code reveals that its power spectrum is symmetrical; hence only half the points are required to perform circular correlation. Besides, either half of the spectrum is asymmetrical where a larger amount of power is concentrated in almost one-quarter of the spectrum on its either sides. This further reduces the number of points used to perform correlation. Comparative results of MATLAB simulation of full-size, half-size and quarter-size circular correlation done on actual data stored on hard disk are provided, and they agree with those obtained using GPS receiver. Further reduction in acquisition time has been achieved by investigating the effect of length of the noncoherent pre-integration period. The improved acquisition methods pave way for further development of new algorithms to enhance software GPS receiver performance.

GPS/CAPS dual-mode software receiver

The positioning of the GPS or Chinese Area Positioning System (CAPS) software receiver was developed on a software receiver platform. The structure of the GPS/CAPS dual-mode software receiver was put forward after analyzing the differences in the satellite identification, ranging code, spread spectrum, coordinate system, time system, carrier band, and navigation data between GPS and CAPS. Based on Matlab software on a personal computer, baseband signal processing and positioning procedures were completed using real GPS and CAPS radio frequency signals received by two antennas. Three kinds of experiments including GPS positioning, CAPS positioning, and GPS/CAPS positioning were carried out. Stability and precision of the results were analyzed and compared. The experimental results show that the precision of CAPS is similar to that of GPS, while the positioning precision of the GPS/CAPS dual-mode software receiver is 1-2 m higher than that of CAPS or GPS. The smallest average variance of the positioning can be obtained by using the GPS/CAPS dual-mode software receiver.

基于HyRAM软件的LNG氢能综合应用实验优化设计仿真

新能源与清洁能源装置的量化安全管理,实验教学的难点。为使学生了解未来液化天然气(LNG)接收站与氢能产业联合发展变化,以LNG接收站为实验平台,通过运用HyRAM软件模拟氢气泄漏的典型场景,对气体泄漏后发生的喷射火与蒸汽云超压的危害区域进行事故分析;根据分析结果进行保护层的优化设计。LNG接收站与HyRAM软件的结合扩展了常规安全实验室的模拟功能,使学生了解LNG接收站的具体工艺流程,锻炼学生利用氢能风险评估软件进行风险分析的能力,为安全工程复合型人才培养的实验教学提供了有益探索。

基于自适应强跟踪Kalman滤波的GNSS跟踪环路设计

为提高GNSS接收机跟踪环路在复杂环境下的跟踪性能,提出一种基于自适应强跟踪Kalman滤波(ASTKF)的跟踪环路,在传统跟踪环路的基础上,以鉴相器输出为观测量进行自适应强跟踪Kalman滤波,滤波结果用于计算导航滤波器的观测量,同时将伪码频率和载波多普勒频率反馈到码NCO和载波NCO,在ASTKF中使用基于卡方分布的渐消因子计算方法,提升跟踪环路鲁棒性。半物理仿真实验表明,相比于基于Kalman滤波的跟踪环路和基于强跟踪Kalman滤波(STKF)的跟踪环路,所提出方法在水平方向上的位置误差和速度误差减小20%以上,有效提高了卫星导航接收机的定位性能。

岸基BDS-R海面测高及其观测值加权方法

随着北斗三号卫星导航系统(BDS-3)的全球组网完成,其反射信号在全球导航卫星系统反射测量(GNSS-R)海面测高领域的应用也更加广泛。为研究BDS-3 B1C反射信号码延迟海面测高性能,以及多星测高数据组合方法,进行了基于B1C码信号的双天线岸基北斗卫星导航系统反射测量(BDS-R)码延迟海面测高实验。利用自主研发的GNSS-R测高软件接收机对实验数据进行事后处理,将测高结果与岸基同步观测的雷达测高仪所测海面高度值进行对比分析,并基于反射信号信噪比(SNR)和卫星高度角加权的方法对多星测高观测值进行加权计算,评定BDS-R海面测高精度。结果表明:自主研发的GNSS-R测高软件接收机可用于海面测高,基于B1C码信号的BDS-R海面测高精度有达到分米级的可能性;根据10 s观测数据平滑可以得到,单颗卫星B1C码信号最优测高结果的均方根误差(RMSE)为0.634 m,平均绝对误差(MAE)为0.507 m,多星测高观测值加权组合最优结果的均方根误差为0.538 m,平均绝对误差为0.500 m,明显优于单星观测精度,最大可提升70%,最小可提升17%;针对同一信号多星GNSS-R测高数据加权方法,应用综合考虑卫星高度角和反射信号信噪比的加权模型优于其他加权模型,测高精度分别比信噪比分段模型、正弦函数模型、指数函数模型、等权模型提升9.4%、9.5%、20.5%、35.2%。

车联网融合通信技术的场景仿真与分析

目前关于车联网的技术处于快速发展阶段,通信场景仿真分析尤为重要。然而,在车联网场景中有大量的移动节点,这使得在真实环境中进行实验变得困难。为此提出以virtual test drive(VTD)软件作为仿真平台,测试在车联网仿真环境中支持加载无线信道模型和编辑交通仿真场景,利用系统级仿真的方法输出5G网络和车联网网络对路面的覆盖情况并与实测环境进行仿真数据比对。仿真结果表明,车与基站通信(vehicle-to-network,V2N)得到的信噪比(signal-to-noise ratio,SNR)与参考信号接收功率(reference signal receiving power,RSRP)符合实测数据的预期,进而改善相较于传统车联网仿真在仿真测试与实际道路测试关联度较低的问题。

北斗新体制BOC B1C导航信号模拟与生成

卫星导航信号模拟与测试作为全球卫星导航定位系统研制建设及导航接收机厂家测试验证的必要环节,其相关技术的进步集中反映了一个国家卫星导航系统建设和应用的水平。随着北斗新体制BOC信号的应用推广,给导航信号模拟与测试又提出了新的要求和挑战,基于伪距迭代和时延滤波技术,实现了对北斗新体制BOC B1C信号的基带生成,并利用开源软件接收机平台对自生成的基带信号进行了捕获、跟踪、解调、定位解算,定位结果显示,三维定位误差方差优于0.74 m,二维定位误差方差优于0.43 m,该模拟信号能够满足测试要求。

基于USRP的便携式接收机设计与实现

针对通信信号抵近接收的使用需求,进行了基于软件无线电外设(USRP)平台的便携式接收机研究。接收机以USRP作为射频前端,完成中频正交(IQ)数据的提取,在通用计算机上实现信号的检测、识别、解调。采用信号源注入和实际信号接收进行测试,结果表明该便携式接收机能够有效完成通信信号接收,对新信号检测时间小于1 s,在信噪比不小于15 dB条件下信号类型识别准确率达90%以上。

定日镜成像通量计算模型

基于HFLCAL模型,在考虑考虑定日镜切向面和矢状面有效偏差后,建立定日镜成像通量计算模型。采用定日镜成像通量计算模型,进行定日镜成像通量计算模拟,并与SolTrace软件计算结果进行量化对比分析。对比分析结果表明,二者在通量分布、光斑中心、成像通量等方面基本吻合,计算精度满足工程实践要求,适用于聚焦定日镜的成像通量计算。

一种GPS软件接收机的设计

随着软件无线电技术的发展,基于软件无线电思想的GPS软件接收机技术取得了长足进展,并成为新一代GPS接收机研制的热点.基于GPS卫星C/A码信号模型,完成了一种基于FFF算法的卫星信号的捕获仿真;设计了一种基于四相鉴频器,锁频环和锁相环的混合载波跟踪算法;设计了一种导航数据的解调算法,完成了卫星信号的导航解算:仿真结果表明,所设计的软件接收机能较好地对卫星信号进行捕获,能准确跟踪含有不同变化规律多普勒频率的载波,并能正确的解调出导航数据。

GNSS-R研究进展及其关键技术

全面评述了GNSS-R技术的研究进展,主要包括海面测高、海面风场遥感、土壤湿度探测以及星载实验等几个主要方面,从软件接收机和反演模型两个方面分析了GNSS-R的关键技术,并指出了存在的问题和发展方向。

一种基于软件无线电技术的中频数字接收机的实现

本文主要讨论了一种基于软件无线电技术的中频数字接收机的实现。在系统具体实现中，提出了利用信号的镜像频谱来实现信号数字正交解调的新方法，从而使得数字正交解调的关键部分──数字ＮＣＯ只需用同采样时钟一样的参考时钟就可以对中频信号实现正交解调。实验结果表明，系统性能优良，可以满足实际需要。

基于ProCAST的大型薄壁机匣件整体熔模铸造工艺研究

为了实现大型薄壁机匣件的整体熔模铸造和获得高质量的铸件,运用ProCAST软件对一种大型薄壁机匣件的整体熔模铸造工艺方案进行数值模拟,通过对充型、凝固过程以及温度场分布的分析,发现浇注后的铸件在内、外环侧面及支板的根部易出现缩孔、缩松缺陷。经过优化设计,通过采取在浇注系统浇冒口处包裹保温毡和提高型壳预热温度等措施,较好地避免了上述铸造缺陷的产生,提高了成品率,获得了较高致密度的机匣铸件。

一种高动态GPS软件接收机方案研究

为了提高GPS接收机的捕获速度和跟踪精度,改善其动态适应性能,提出了一种GPS软件接收机方案。首先采用延迟、累积捕获结构搜索C/A码起始点,引入延迟累加器辅助频谱分析实现各卫星多普勒频移成分的分离、估计,将传统的二维捕获过程简化为两个一维搜索过程,提高了捕获速度;然后采用多重辅助结构的跟踪环路,提高载波、伪码频率和相位的跟踪精度。通过对GPS实测数据和高动态模拟数据进行仿真实验,验证了该软件接收机方案的有效性。

基于射频前端的GPS软件接收机设计与验证

介绍了基于硬件射频前端的GPS软件接收机设计与验证。针对GPS串行的搜索算法速度慢的缺点,采用了高速的并行码相位搜索算法;设计和实现了码跟踪环和载波跟踪环,并用载波环路来辅助码跟踪环路;综合考虑接收机的动态性和噪声影响,采用最优化设计思想,设计了GPS软件接收机最优环路带宽。采用GPS中频信号采样器采集实际GPS数据,对搜索和跟踪算法进行了验证。测试结果证明所设计的搜索和跟踪方法是有效的,使得用户在微弱信号处理、多路径处理和发展新的算法等方面具有更大的灵活性,为实际的高性能硬件GPS接收机设计提供的重要的基础。

软件接收机的一种实用结构

基于软件无线电高度的开放性和通用性的特点 ,文中提供了一种软件无线接收机的设计方案 ,包括硬件构成以及软件算法的介绍 .所选用的都是通用器件 ,成本低廉 ,具有很强的实用价值 .

基于软件无线电技术的GPS软件接收机的研究与实现

深入研究了GPS软件接收机的相关算法,阐述了GPS软件接收机设计过程中信号搜索、跟踪以及伪距定位等关键技术。针对搜索过程中利用信号相关法求解精频速度慢的缺点,提出了相位关系解算法;进一步分析二阶跟踪环路工作原理,对其带宽进行优化设计,使接收机具备较高的动态性能和较低噪声影响。基于Matlab环境,通过优化算法结构,设计并实现了GPS软件接收机算法应用程序。最后通过实际测试数据对算法进行了验证,该接收机可以处理12通道卫星信号,并且各项指标分析结果均达到单点伪距定位要求。

GPS信号海面散射特性和初步实验结果

2006年9月至2007年3月,在福建厦门附近进行了为期半年的实验,观测和研究GPS海面反射信号特性。一天内至少有百分之九十六的时间可以同时接收到4颗卫星海面反射信号,最多时达到8颗。观测资料用于反演有效浪高、海面高度和潮汐等海洋参量。重点讨论海面散射特性,研究海面反射波与直达波的功率比值,以及它们随电波的入射角、海面等效浪高(SWH)等的依赖关系,为星载接收机设计提供科学数据。