面向弱信号环境的GNSS伪码设计及捕获技术研究

发布时间：2018-01-22 08:30

本文关键词： 全球导航卫星系统弱信号环境伪码设计捕获干扰分析　出处：《华中科技大学》2013年博士论文　论文类型：学位论文

【摘要】：全球导航卫星系统(Global Navigation Satellite System, GNSS)在国防和经济建设中的重要性日益凸显,许多国家和地区都在积极构建拥有自主知识产权的GNSS系统。在系统构建过程中,如何提高GNSS系统的可靠性、完好性及定位精度始终是研究的主要目标,特别是近年来随着GNSS应用范围的扩展,在信号衰减严重的弱信号应用环境中如何提高定位可靠性受到了人们的普遍关注,成为当前GNSS研究的热点。在诸多影响弱信号环境下GNSS定位性能的因素中,信号体制和接收技术是其中最重要的两个。考虑到伪码设计是信号体制设计的核心环节,在很大程度上决定了GNSS信号性能；而捕获技术则是弱信号接收技术的关键,因此本文主要针对GNSS伪码设计和弱信号捕获技术两个关键问题进行研究,以提高弱信号环境下GNSS系统的定位性能。本文的创新性主要体现在以下几点： 1)针对弱信号环境下强多址干扰引起的GNSS信号误捕获问题,提出了一种能够明显改善弱信号捕获性能的非等长伪码设计方法。这种非等长伪码设计方法克服了长伪码存在的捕获时间过长及短伪码存在的互相关隔离度过低的问题,通过令同一系统不同信号间伪码码长互质,有效的降低了伪码互相关值,改善了弱信号环境下的信号捕获性能,实现了捕获时间和捕获性能的折衷。为了充分说明非等长伪码设计方法的优势,本文从时域和频域两方面阐述了非等长码改善弱信号捕获性能的原理,并对该伪码设计方法对弱信号捕获的改善作用进行分析,之后通过仿真验证了理论分析的正确性。结果表明,在相同接收条件下,采用非等长伪码设计时信号的检测概率明显高于相当长度等长码情况。对于弱信号情况下多址干扰引起的码跟踪误差,非等长伪码设计亦有明显的改善效果。非等长伪码设计方法使多址干扰引起的码跟踪环鉴别器输出误差呈现随机变化的特点,这样码跟踪环路滤波器可方便滤除多址干扰引起的码跟踪误差,使码跟踪精度得以提高。理论分析和仿真结果验证了非等长码对弱信号环境码跟踪精度的改善作用。 2)为了克服独立捕获模式下因后相关处理增益较低而无法保证弱信号可靠捕获的问题,提出了一种改进的差分累加后相关处理技术。论文首先对独立捕获模式三种常见的后相关处理技术(即相干累加、非相干累加和差分累加)进行分析对比,得出因差分累加具有相位解旋的作用且无明显的平方损耗,同时对数据位翻转不太敏感,故更适用于弱信号环境GNSS信号捕获的结论。之后详细分析了导航数据翻转和载波频率估计误差对传统差分后相关技术处理增益造成的影响,并在此基础上针对弱信号环境提出一种改进的半比特频率补偿差分后相关技术。该技术通过在捕获环节引入多普勒频差补偿,消除了多普勒频率估计偏差引起的处理损耗,并通过半比特处理技术消除了相干积分环节数据翻转可能带来的的处理损耗,使弱信号捕获概率明显提高。理论分析和仿真结果表明,改进的后相关差分累加处理技术捕获性能明显优于传统差分累加技术,具有更高的捕获灵敏度和可靠性。 3)针对弱信号情况下非白射频干扰对信号的捕获和跟踪性能影响较大且难以分析的问题,提出了一种系统的非白干扰的白化分析方法。该方法将非白干扰通过相应的白化系数转化成易于分析的等效白噪声,简化了非白干扰的分析过程。考虑到非白干扰对捕获及载波跟踪性能的影响主要体现在即时通道,本方法在分析非白干扰对即时通道的影响时,通过首先推导白噪声分析模型,之后直接将非白干扰的等效白噪声替换已有模型白噪声的方法,简化了非白干扰对相关输出信噪比和载波跟踪精度影响的分析过程,使非白干扰的影响作用更直观；对于非白干扰对码跟踪的影响,则充分考虑了相干早迟处理码跟踪环和非相干早迟处理码跟踪环的特点,通过引入新的参数,完成了非白干扰的白化分析过程。以Betz经典的码跟踪分析方法作为参照,将本方法与现有的非白干扰分析方法的分析方法进行对比,发现本方法仿真结果与Betz方法的分析结果更趋一致,然而本方法的分析过程却较Betz经典的码跟踪分析简化了许多,因而更便于应用。
[Abstract]:The global navigation satellite system (Global Navigation Satellite System, GNSS) on the importance of national defense and economic construction has become increasingly prominent in many countries and regions are actively building GNSS system with independent intellectual property rights. In the process of the construction of the system, how to improve the reliability of the GNSS system, the integrity and the positioning accuracy is always the main goal of the research. Especially in recent years, with the expansion of the application scope of the GNSS, on how to improve the reliability of positioning signal attenuation has received extensive attention in the application of weak signal environment is serious, has become the research hotspot of GNSS.
In the factors of the positioning performance of GNSS signal environment influenced the weak, signal system and receiving technology is one of the most important two. Considering the pseudo code design is the core part of signal system design, largely determines the performance of GNSS signal; and the capture technology is the key technology of weak signal reception, so this paper the main techniques of the two key problems in design of GNSS pseudo code capture and weak signal are studied, in order to improve the positioning performance of the GNSS system in weak signal environment. The innovation of this paper is mainly reflected in the following points:
1) according to the error of GNSS signal acquisition problem in weak signal environment caused by strong Mai, a weak signal acquisition can significantly improve the performance of non isometric pseudo code design method. The design method of long pseudo code to overcome the isolation of low cross-correlation of long PN code acquisition time are too long and short PN code the existence of the problem, by making the same system among different signals PN code length relatively prime and effectively reduce the pseudo code cross-correlation values, improve the signal acquisition performance in weak signal environment, realize the acquisition time and compromise capture performance. In order to fully explain the design method of non isometric PN advantage, this paper from the two aspects of the time domain and frequency domain describes the non isometric code improvement principle of weak signal acquisition performance, and analyze the effect to improve the weak signal acquisition of the PN code design method is verified by simulation after theoretical analysis is correct . the results show that under the same conditions, the detection probability of receiving, non isometric pseudo code design signal was significantly higher than that of equivalent length equal code. For weak signal in the case of multiple access interference caused by code tracking error, the unequal pseudo code design also has obvious improvement effect. The characteristics of non long pseudo code design method the multiple access interference code tracking loop discriminator output error caused by random variation of the present, this code tracking loop filter can filter the multiple access interference caused by code tracking error, the code tracking accuracy can be improved. Theoretical analysis and simulation results prove the non equal length code tracking accuracy improvement in weak signal environment.
2) in order to overcome the capture mode for independent after the processing gain is lower and can not guarantee the reliability of weak signal capture problem, put forward the related processing technology of an improved differential accumulation. Firstly, three kinds of acquisition mode after processing technology of independent (i.e., coherent, non coherent and differential the cumulative) were compared, obtained by the phase difference accumulation has the effect of untwisting and square loss obviously, and the data bit less sensitive, so it is more suitable for weak signal environment GNSS signal acquisition and conclusion. The detail analysis of the navigation data switching and carrier frequency estimation error on the performance of the traditional difference related technical processing gain caused, and based on the weak signal environment and proposes an improved half bit frequency compensation difference and related technology. The technology through the link for the capture of Doppler frequency Error compensation, eliminates the estimation of Doppler frequency deviation caused by the loss of processing, and through the half bit processing techniques of coherent integral data flip may bring loss to eliminate the processing, the weak signal acquisition probability is improved. Theoretical analysis and simulation results show that the difference of improvement after accumulating processing technology acquisition performance is better than the traditional difference points accumulated technology, has a higher acquisition sensitivity and reliability.
3) for radio frequency interference on signal acquisition and tracking performance of large and difficult to analyze the problem of weak signal condition, proposed a system of non white interference whitening analysis method. The non white interference through the whitening coefficients corresponding into easy to analysis effect of white noise, simplified analysis the process of non white interference. Considering the effect of non white interference on acquisition and carrier tracking performance is mainly reflected in the real-time channel, this method in the analysis of non white interference effects on instant channel, through the first derivation of white noise analysis model, after the equivalent white noise interference model to replace the existing non white noise the method simplifies the analysis process, influence of non white interference on the output signal-to-noise ratio and carrier tracking accuracy, the effect of non white interference is more intuitive; for non white interference on code tracking, is sufficient Considering the coherent early late processing code tracking loop and noncoherent early late processing characteristics of the code tracking loop, by introducing new parameters, completed the albino non white interference analysis process. Taking Betz classic code tracking analysis method as a reference, comparative analysis method with the existing non white interference analysis method the results of the simulation results with Betz method is more consistent, but the analysis process of this method is compared with the classic Betz code tracking analysis simplified a lot, so it is more easy to use.

【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TN96.1

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