Abstract: The GNSS software receiver principle is introduced based on its architecture. Signal correlator and its work flow are designed firstly in this paper. Parallel code searching strategy using FFT (fast fourier transform) is discussed in detail, and the phase discriminator, frequency discriminator in the carrier loop for signal tracking are also analyzed. Various error sources are discussed such as the clock error, tropospheric error model, where a simple equivalent model for the later one is proposed for the software receiver. The implementation steps based on least square method is also proposed. Simulation result shows that the proposed signal acquisition strategy and the tracking method work well, including the parallel code searching and the PLL (phase lock loop) algorithm supported by DLL (delay lock loop) and FLL (frequency lock loop). In addition, the single point positioning result meets the demand using the least square method with the considerations of clock error, tropospheric error, ionospheric error and the earth rotation introduced error.

Key words: global navigation satellite system (GNSS), software receiver, signal acquisition, signal tracking, system simulation

摘要： 从GNSS（global navigation satellite system）软件接收机的总体结构出发，阐述了GNSS软件接收机基本原理，设计了GNSS软件接收机的信号相关器及其工作流程，介绍了基于FFT的码并行搜索策略，在信号跟踪中详细给出了载波环路中的鉴相器和鉴频器设计。对于导航定位解算，讨论了各项误差的处理方法，包括钟差和简化的等效对流层误差模型，并给出了最小二乘法的具体实现步骤。仿真结果表明，软件接收机中采用伪码并行捕获方法、DLL环与FLL环辅助下的PLL环路算法可获得良好的效果。在考虑星钟误差、对流层误差、电离层误差和地球自转引起的偏差等误差源的条件下，最小二乘法解算的单点定位结果满足要求。

关键词: 全球导航卫星系统, 软件接收机, 信号捕获, 信号跟踪, 系统仿真