一种矢量跟踪环路及其抗干扰性能分析

针对GPS信号在接收端的功率较弱,接收机在载噪比低的环境中很容易受到其他信号的干扰,该文提出一种基于矢量跟踪环路的接收机设计方法,在跟踪环路环节对干扰信号进行抑制。以实际的伪距、伪距率误差为状态量,量测得到的伪距、伪距率误差为观测量构建跟踪环路滤波器,利用更新后的接收机位置,计算出接收机与可视卫星间的观测矢量,完成闭合反馈回路。接收机的信号跟踪与导航解算部分融合一体,改变了传统接收机的结构。对比分析标量和矢量跟踪环路的预测伪距方差,来研究矢量跟踪环路对干扰信号的抑制性能。采用实际卫星星历进行仿真实验,验证了矢量跟踪环路比标量跟踪环路的预测伪距方差小,抗干扰能力强。     

牵引式欺骗对矢量跟踪环路的影响

牵引式欺骗能够在不引起跟踪环路失锁的条件下诱使接收机跟踪欺骗信号,是一种隐蔽性很高的欺骗干扰方式。对于标量接收机,由于其跟踪环路相互独立,因此针对单个信号进行牵引式欺骗时,不会受其他信号的影响。而矢量接收机的跟踪环路通过接收机状态耦合,存在相互影响,即牵引式欺骗对矢量和标量跟踪环路的影响存在差异。本文基于无噪声且欺骗信号与真实信号载波频率和载波相位相等的假设条件,分析牵引式欺骗对矢量跟踪环路的影响,推导出欺骗成功条件,并利用信号源模拟器和软件接收机对分析结果进行验证。研究结果表明,对矢量跟踪环路成功实施牵引式欺骗的条件较标量跟踪环路更为严苛,反映出矢量跟踪环路固有的抗欺骗干扰能力。     

矢量跟踪算法在抗远近效应中的应用

针对室内伪卫星独立定位系统中由于远近效应而导致跟踪环路失锁甚至定位失败的问题,提出了一种有效抑制远近效应的算法矢量跟踪环路（VTL）算法。通过分析 VTL 环路结构,建立了线性化的系统模型,并推导了详细的工作流程。VTL 以定位误差为状态量,以伪距、伪距率误差为观测量,结合更新后的定位结果,得到稳定的环路跟踪输入。仿真对比分析了标量跟踪环路（STL）和矢量跟踪环路对中断信号的持续跟踪性能。搭建了室内伪卫星独立定位系统,将采集到的中频信号在 VTL 软件接收机中进行定位解算,实验结果证明VTL 相对于STL 可以有效地抑制远近效应。     

基于扩展卡尔曼滤波器的矢量跟踪算法研究

该文针对矢量跟踪算法缺乏定量分析的问题,对线性化模型与跟踪误差进行了研究.为了提高矢量跟踪环的动态跟踪性能,修正了已有线性化观测矩阵忽略接收机伪距率对位置的偏导项的问题;提出了新的环路反馈量,简化了运算过程.推导出了矢量跟踪环的热噪声跟踪误差,与标量跟踪环相比跟踪门限明显降低,并且在相同条件下,观测卫星数越多,矢量跟踪环的跟踪门限越小;推导了矢量跟踪环的动态应力跟踪门限,证明矢量跟踪环可以处理高动态微弱信号.通过 Monte Carlo 仿真验证了理论分析结果的正确性.     

“北斗”B2频段导航信号伪码跟踪性能分析

与传统卫星导航信号体制不同,新一代“北斗”B2频段导航信号采用了交替二进制偏移载波调制（AltBOC）体制,因此伪码跟踪性能也与传统信号体制有较大差异。首先介绍了AltBOC调制信号原理及特点,然后根据码跟踪精度理论比较了新型调制信号与传统信号体制的性能差异,分析了不同鉴相器时B2频段信号的码跟踪误差,并对不同相关器间隔、环路带宽、前端带宽、载噪比环境条件下的伪码跟踪误差进行了仿真分析。仿真结果表明,提高信号载噪比、射频前端带宽或减小相关器间隔、环路带宽均能减小码跟踪误差。研究结果对新一代“北斗”导航信号新体制性能的评估以及“北斗”导航接收机的系统设计具有一定指导意义。     

多遮挡环境下GRU-RNN辅助的GNSS接收机VTL算法

针对城市峡谷等多遮挡环境下信号频繁短时阻塞导致全球卫星导航系统(GNSS)接收机跟踪性能下降的问题,提出了一种GRU-RNN辅助的矢量跟踪环路算法.利用卫星信号正常时导航滤波器的新息序列来训练GRU-RNN网络,网络训练完成后,当卫星信号出现频繁短时阻塞时,利用GRU-RNN网络预测各个通道的伪码相位误差和载波频率误差...     

基于I/Q支路相干积分观测滤波的GPS接收机信号跟踪方法

针对传统GPS接收机在弱信号环境下跟踪误差大,收敛速度慢的缺点,该文提出一种基于I/Q支路相干积分观测滤波的GPS信号跟踪方法。将接收机I/Q支路相干积分输出为观测量,应用无迹卡尔曼滤波(Unscented Kalman Filter, UKF)算法构建卡尔曼滤波器,得到基带数字信号处理滤波模型,闭合接收机跟踪环路。该方法能够有效减小传统GPS跟踪环路中信号参数的估计误差,提高接收机抗干扰能力和弱信号环境下环路跟踪性能。仿真对比结果表明,不同载噪比环境下相比传统GPS信号跟踪的方法,基于I/Q支路相干积分观测的信号跟踪算法能够提高跟踪精度,加快跟踪收敛速度。     

利用矢量跟踪环路的欺骗干扰检测与抑制方法

欺骗干扰的信号模型与真实卫星信号相似,具有很强的隐蔽性。近年来欺骗干扰不断威胁GPS系统因此受到了国内外学者的广泛关注。生成式欺骗干扰的延迟和功率具有可控性和变化性,因此隐蔽性和危害性更强。针对该问题,本文在欺骗干扰来向与真实卫星信号来向未知的前提下,结合阵列天线技术与矢量跟踪环路,提出一种基于矢量跟踪环路的欺骗干扰检测和抑制方法。该方法首先根据矢量跟踪环路的预测参数重构基于远滞后码的参考信号;其次根据接收信号与参考信号的相干累加结果构造欺骗干扰检测模型;然后根据阵列接收信号与参考信号的相干累加结果估计协方差矩阵;最后根据协方差矩阵中最大特征值对应的特征向量估计欺骗信号的特征向量,并根据该特征向量构造正交投影矩阵抑制欺骗干扰。理论分析和仿真实验得出了本文提出的算法具有较好的抗欺骗干扰性能。      

基于矢量跟踪的导航接收机研究综述

近年来,矢量跟踪环路的研究受到了广泛的重视。频频出现在国际会议的研讨项目之中,大量的相关文章被出版。同时,国内也出现大批的机构和学者从事于矢量跟踪的研究。目前所有的工作可大致分为以下几个方面,①矢量接收机与传统接收机性能的比较;②矢量跟踪在噪声环境和高动态下的性能分析:③矢量跟踪在其他相关方面的应用分析,如与惯性导航组合等。本文梳理了国内外的研究现状,总结了文献中的重要结论,希望对于从事矢量跟踪的学者有所帮助。     

室内外导航信号无缝链接连续性研究

对GPS的传统跟踪环路进行了分析,指出传统的载波环路不能兼顾环路的灵敏度和动态。而且,文中对多径的处理进行了分析。为了跟踪低动态的GPS弱信号,保持室内外导航定位服务的连续性,使用了基于扩展卡尔曼滤波器的矢量延迟环路,经仿真验证,即使在卫星信号消失的时候,仍然能够保持良好的导航信号跟踪,在卫星信号恢复之后不用重新捕获,并且仍能获得较好定位误差。     

Performance Analysis of GPS Receivers in Non-Gaussian Noise Incorporating Precorrelation Filter and Sampling Rate

Global positioning system (GPS) receivers find growing applications in indoor and outdoor communication environments, including urban and rural areas. Interference and noise sources for GPS receivers may assume Gaussian or non-Gaussian distributions. The GPS receiver performance under Gaussian additive noise has been studied. Non-Gaussian noise may equally contaminate the GPS satellite signals and disturb the receiver delay lock loops (DLL), producing significant tracking errors. These sources include impulsive noise, ultra-wideband (UWB) signals, and impulse and noise radar signals for target tracking and indoor imaging applications. This paper considers non-Gaussian noise of finite variance and examines its effect on the discriminator outputs for the commercial GPS receiver that uses the coarse acquisition (C/A) code. The correlator noise output components are produced from the correlation between the noise sequence and the early, late, and punctual reference C/A code. Due to the long time averaging, which is characteristic of the GPS correlation loops, these components assume Gaussian distributions. The discriminator tracking error variance is derived, incorporating the effect of noise, the front-end precorrelation filter, and the sampling rate.     

GPS接收机载波跟踪环设计与分析

针对GPS接收机载波跟踪环环宽与跟踪的动态性能问题,在分析影响GPS信号动态性能的主要参数热噪声、晶振Allan相位噪声、晶振振动相位噪声和动态应力的基础上,通过对不同阶数的锁相环、锁频环跟踪门限分析与仿真,主要解决了如何设计GPS接收机的载波跟踪环路的带宽,并使系统性能达到最佳的问题,即使用环宽为18 Hz的二阶锁相环辅助环宽为10 Hz的三阶锁频环可以跟踪动态范围小于10 g、100 g/s的高动态信号。     

GPS信号被延时后对定位影响的仿真分析

根据GPS接收通道跟踪环对信号实施跟踪解调的原理,分析了经过人为与自然延时的信号被接收机跟踪解调的必要条件。再根据GPS定位原理和定位求解方程,对被人为与自然延时的信号进入接收机进行定位解算后,信号延时值变化与接收机定位偏差之间的关系进行了仿真分析。     

压制干扰对GPS接收机码跟踪环的性能影响分析

压制干扰是GPS接收机面临的重要的人为威胁之一,对伪码跟踪的跟踪测距精度产生影响,甚至导致伪码跟踪环失锁。干扰对伪码跟踪环的影响模型涉及许多因素,建模比较困难。以常用的非相干超前减滞后功率延迟锁定环为例,建立了码跟踪环在宽带噪声干扰、窄带干扰和点频干扰下的跟踪误差模型,比较了压制干扰对C/A码和P(Y)码跟踪环性能的不同影响。通过对不同干扰方式下C/A码和P(Y)码跟踪误差的仿真,得出了对C/A码和P(Y)码跟踪环性能影响较大的干扰方式和干扰频率,为GPS接收机干扰方法和抗干扰措施的选择提供了理论依据。     

GPS卫星捕捉及跟踪算法研究

为了能完成卫星定位,需要对卫星信号进行捕获、追踪。文中针对带有C/A码的L1频段的GPS信号进行定位研究,捕获能从接收的信号中粗略地估算出可见卫星的信号参数,用于帮助接收机初始化跟踪环路,并开始跟踪信号。码跟踪和载波跟踪模块则将这些参数细化,跟踪后即可解调出导航数据。仿真结果表明,算法可准确快速地从32颗卫星中捕捉和跟踪预定的卫星信号。     

Code tracking performance analysis of GNSS signal in the presence of CW interference

Continuous wave (CW) interference can cause severe performance degradation of global navigation satellite system (GNSS) receiver. In analysing the code tracking performance of pilot channel under CW interference, the signal spectrum consists of discrete spectral lines and the interference term of the correlator output shows the characteristics of direct current or sine. Thus the traditional assumptions that the interference obeys the Gaussian distribution and that the spectrum of the signal is continuous no longer hold. Considering this fact, this paper presents the analytic expressions of the code tracking error bound for the early-minus-late power (EMLP) discriminator and the dot-product (DP) discriminator. The derived expressions can be used to assess the susceptibility of code tracking performance under CW interference for the pilot channel of GNSS signals. Then the GPS L5 signal is taken as an example of the application of the derived mathematic expressions. The effects of finite front-end bandwidth, correlator spacing, and discrete spectrum of pseudo-random noise (PRN) code on performance are discussed. It is shown that the code tracking performance can be improved by choosing proper receiver parameters and some of the L5 codes are more vulnerable to the interference compared with the average level.     

Applications of New Fuzzy Inference-Based Tracking Loops for Kinematic GPS Receiver

Carrier phase measurement is essential for high-accuracy measurement in kinematic global positioning system (GPS) applications. For GPS receiver design, a narrow noise bandwidth is desired to decrease phase jitter due to thermal noise. However, this bandwidth will deteriorate the capability of the tracking loop and result in cycle slipping. Based on bandwidth adjustment criteria, a novel intelligent GPS receiver is proposed for solving the carrier phase tracking problem in the presence of high dynamic environments. A phase error estimator is developed in the carrier loop to conduct the phase error signals; i.e., frequency and frequency ramp errors. Two kinds of fuzzy inference (FI)-based approaches, fuzzy logic control and adaptive neuro-fuzzy control methods, that are simple and have easy realization properties are designed to perform rapid and accurate control of the digital frequency phase-locked loop (FPLL). A new design procedure for kinematic GPS receiver development is also presented. The computer results show that the FI-based receivers achieve faster settling time and wider pull-in range than the conventional tracking loops while also preventing the occurrence of cycle slips.     

Interference cancellation in GPS receiver using noise subspace tracking algorithm

In this paper, we address the problem of interference cancellation in global positioning system (GPS) receiver using a two-step approach: subspace projection technique and maximum signal-to-noise ratio (MSNR) beamforming. The interference signals can be effectively suppressed by projecting the received signal on the noise subspace. Here noise subspace tracking algorithm is employed to estimate the noise subspace directly. We then apply a beamformer to maximize the signal-to-noise ratio of the interference-free signal. Simulation results show that our approach can effectively eliminate the strong interference and enhance the performance of the GPS receiver.     

基于FPGA的GPS接收机实现

利用可编程片上系统(SOPC)技术,设计了一种基于FPGA的GPS接收机。提出了基于多普勒频域移位的捕获策略,并分析了捕获时间。基于延迟锁定环与Costas环跟踪方法,给出接收机的SOPC实现。实验结果表明,该接收机的信号捕获、跟踪方法正确可行,且在静态条件下水平定位精度优于4.5m(标准差),具有良好的实时性、灵活性和可扩展性。