【作者】 梁坤；

【导师】 施浒立；

【作者基本信息】 中国科学院研究生院（国家天文台） ， 天文技术与方法， 2008， 博士

【摘要】 目前,GPS (Global Positioning System,全球定位系统)已经在全世界得到了广泛的应用,但大多都是在信号条件较理想的环境中。当信号条件不理想时,例如在室内、森林和城市环境条件下,遮挡、多径和干扰等现象较严重,GPS就不能得到很好的应用。在GPS领域内,室内、森林和城市等复杂环境被统称为室内环境。与普通环境相比,GPS信号在室内环境中,能量有更多的削弱和衰落,到达时间有更大的延迟,接收信噪比有更大程度的恶化,所以,其可用性和普通GPS接收机的定位精度都会大大下降,GPS的总体性能会严重恶化,这样普通的GPS接收机将难以捕获和跟踪导航卫星信号。而室内环境恰是人类活动的主要环境之一,在室内环境中有很多重要的GPS应用需求,又高灵敏度GPS接收技术是一种满足室内环境要求的定位技术,所以,高灵敏度GPS接收技术的研究非常必要,高灵敏度GPS接收机已成为当前的研究热点。本文介绍了GPS信号特点,分析了室内环境GPS信号的特性,针对高灵敏度GPS接收技术中的几个关键问题,设计并实现了高灵敏度GPS接收技术研究平台。在此基础之上,设计了高灵敏度GPS接收机系统结构,对高灵敏度GPS捕获和跟踪技术进行了较深入的分析和研究,构造了高灵敏度GPS载波跟踪结构和高灵敏度GPS码多普勒补偿方法,创造性地提出了两种高灵敏度GPS互相关减轻方法∶并行互相关减去法和基于频差因子的并行互相关减去法,及两种高灵敏度GPS码相位测量精化方法∶二阶最小二乘拟合精化法和广义延拓逼近精化法。仿真实验结果表明∶互相关减轻的两种新方法去除互相关效果良好,较前人构造的方法实用性更强,基于频差因子的并行互相关减去法在计算量方面有更大的优势,可以加快高灵敏度GPS接收机信号捕获速度,节省基带信号处理时间;与其它方法相比,码相位测量精化的两种新方法在精确性、稳定性和跟踪作用等方面都分别具有较大优势。广义延拓逼近精化法的精化精度和跟踪精度最高,二阶最小二乘拟合精化法的稳定性最好,且该两种方法计算量小、易于实现,在低信噪比、大码多普勒的情况下引导跟踪,可以使码相位测量达到更好的效果。总之,这些方法在室内环境的高灵敏度GPS接收机中有较好的应用价值。更多还原

【Abstract】 Now, GPS is applied broadly in the world, but in the situation, the users are usually in the environments where there are good GPS signals. When the users are in the environments where there are not good signals, such as, indoor, in forests and in cities, GPS will not be able to be used well because of shading, multipath, and interference and so on. Indoor, forests and cities and so on are able to be called indoor environments. Compared with the common circumstance, signal power, TOA and reception S/N of GPS signals will be worsened much severely, and positioning precision of GPS receivers, availability of GPS signals and general performances of GPS will be declined in the indoor circumstance, so usual GPS receivers will be hard to acquire and track the signals from navigation satellites. However, the indoor environment is one of the main environments where humans live. In indoor environments, there are a lot of application needs of GPS, and high sensitivity GPS receiving technique is a kind of technique meeting the needs of positioning in indoor environments, so researches on high sensitivity GPS receiving technique are necessary in the extreme and the researches on high sensitivity GPS receivers become hot points currently.In the dissertation, at first, traits of GPS signals were introduced, and the characteristics of indoor GPS signals were analyzed. In terms of several crucial problems in high sensitivity GPS receiving techniques, the research plat of high sensitivity GPS receiving techniques was designed and implemented. On the basis of them, the system architecture for high sensitivity GPS receivers was designed, high sensitivity GPS acquisition and tracking techniques were analyzed and researched deeply, high sensitivity GPS carrier tracking architecture and the method of compensating for code Doppler were constructed, and two new methods of cross correlation mitigation : the parallel cross correlation subtraction method and the parallel cross correlation subtraction method based on frequency difference coefficient, and two new methods of code phase measurement fining : the LS(Least Square) fitting fining method and the generalized extended approximation fining method were created.By simulation tests, the effects of the two cross correlation mitigation methods were good and the practicality of them was high compared with the foregoing methods. The parallel cross correlation subtraction method based on frequency difference coefficient had much advantage on computation quantity, and was able to accelerate the acquiring speed of high sensitivity receivers and save the time of baseband signals processing.Simulation tests proved that the two new methods of code phase measurement fining had great advantages in accuracy, stability, and tracking performance separately over the other methods. The accuracy and tracking performance of the fining method by generalized extended approximation were the best, and the stability of the fining method by LS (Least Square) fitting was highest. Their computation quantity was little, and they were able to be implemented very easily. In the situations of low signal noise ratio and great Doppler frequency, they can induct tracking and acquire code phase measurement fining effects.In conclusion, the new methods have good application values to high sensitivity GPS receivers in indoor environments.更多还原