中文说明：
研究了一种数字中频 GPS 信号生成方法。给出了数字中频信号数学模型，模型考虑了各种因素对信号的影响。通过导航电文分析，提出信号传播时延、多普勒频移以及信号入射方向的估计方法。给出了中频信号产生的流程，对其中时延的设置，信号的上变频、信号幅度设置以及方向信息的导入进行了阐述。对所生成的信号模型进行了仿真分析，给出了信号产生各个阶段的频谱，对所生成的信号进行了相关捕获。仿真结果表明频谱特征符合理论分析，能够被捕获并找出信号时延从而实现定位。证明该信号模型能作为信号源应用于 GPS接收机研制中。
English Description：
A method of digital IF GPS signal generation is studied. The mathematical model of digital IF signal is given. The influence of various factors on the signal is considered in the model. Through the analysis of navigation message, the estimation methods of signal propagation delay, Doppler frequency shift and signal incident direction are proposed. The process of IF signal generation is given, including the setting of time delay, up conversion of signal, setting of signal amplitude and importing of direction information. The simulation analysis of the generated signal model is carried out, the spectrum of each stage of signal generation is given, and the correlation acquisition of the generated signal is carried out. The simulation results show that the spectrum characteristics conform to the theoretical analysis, and can be captured and the signal delay can be found to achieve positioning. It is proved that the signal model can be used as a signal source in the development of GPS receiver