全球定位系统(GPS)是全球导航卫星系统(GNSS)中应用最广的一种系统。目前，GPS市场已经进入了广泛型发展阶段，各种类型的应用在方便用户的同时，也对GPS接收机的性能提出了更高的要求。面对市场份额主要为国外大型GPS芯片厂商所占据的现状，研发具有自主知识产权的高性能GPS接收机芯片具有重要的实用价值和巨大的经济意义。而基带的核心算法，直接影响着整个接收机的灵敏度、定位精度、首次定位时间(TTFF)等性能，也决定了芯片的成本。本论文围绕GPS接收机基带设计中所涉及的两项核心技术——捕获和跟踪的算法展开研究，力求提高GPS信号捕获灵敏度，改善跟踪稳健性和定位精度，并设计实现一款GPS高灵敏度快速捕获引擎。论文的主要研究内容与贡献包括： 1.提出了一种通用的伪码并行搜索门限设定方法，该方法可以方便地对近似门限进行准确的补偿，并具有良好的鲁棒性。 2.深入研究了循环相关结合FFT的高灵敏度GPS信号快速捕获算法，设计了一种GPS高灵敏度快速捕获方案，并推导了信号捕获的虚警概率和发现概率，为捕获门限和驻留时间的设计提供了理论依据。 3.改进了载波跟踪数字锁相环(DPLL)的环路参数设计准则并使用可控根(Controlled—Root)法对DPLL进行了建模仿真。基于该模型分析了环路参数对瞬态、稳态响应的各项特性和热噪声性能的影响。 4.提出了一种多相关支路混合间距延迟锁定环的新型码跟踪环结构。基于该结构提出了两种码跟踪环算法——窄相关扩展延迟锁定环(NcExtDLL)和窄相关选择延迟锁定环(NcSelDLL)，解决了现有DLL设计不能兼顾跟踪精度和牵引范围的问题，提高了环路的稳健性，改善了用户的定位精度。 5.设计实现了一款采用循环相关结合FFT算法的GPS高灵敏度快速捕获引擎，捕获灵敏度达到了-178dBW。 关键词：GPS，高灵敏度，捕获，跟踪，延迟锁定环

The Global Positioning System (GPS) is one of the most widely used Global Navigation Satellite Systems (GNSS). The popularization of GPS conveniences the customers, and imposes higher performance demands on GPS receivers at the same time. At present the market is occupied by several overseas GPS chip vendors and thereby it is of great significance to research and design our own GPS chipsets. GPS baseband signal processing algorithm determines the structure of GPS chipset and directly affects the performance of a GPS receiver, such as sensitivity, Time-to-First-Fix (TTFF) and positioning accuracy. This dissertation focuses on study of the key algorithms such as GPS signal acquisition and tracking, aiming to improve the performance of the acquisition sensitivity, the tracking robustness and the positioning accuracy. In addition, a GPS acquisition engine with high sensitivity and high search speed is designed and implemented. The main contributions of this dissertation are as follows: 1.A generalized threshold setting rule with good performance and robustness for parallel PN code acquisition is proposed and successfully used in the GPS receiver design. 2.The rapid acquisition algorithm based on the combining circular correlation with FFT is studied in detail, and a GPS acquisition scheme with high sensitivity and high search speed is proposed. The false-alarm probability and the detection probability of the algorithm are analyzed to provide theoretical basis for settings of the acquisition threshold and the dwell time. 3.The loop parameters of the digital Phase-Locked Loop (DPLL) used for carrier synchronization are optimized, and based on the 'controlled-root' scheme, the DPLL is modeled, and the transient response, the steady-state response and the noise performance are analyzed. 4.A novel code tracking scheme named Multi-correlator with Hybrid Spacing (MCHS) is proposed. Based on the scheme, two algorithms are developed, which are Narrow Correlator ExtDLL (NcExtDLL) and Narrow Correlator SelDLL (NcSelDLL). The two algorithms overcome the problem that the code tracking range and tracking accuracy can not be achieved simultaneously in conventional DLL circuits, and improve the stability of the code tracking and the positioning accuracy. 5.A GPS acquisition engine using the circular correlation combined with FFT algorithm is designed and implemented, by which the acquisition sensitivity is improved to -178dBW with high search speed. Keywords: GPS, High Sensitivity, Acquisition, Tracking, DLL