基于PXIe总线架构的GPS导航信号模拟源设计及实现

卫星导航信号模拟源为用户终端设备的设计、验证、测试提供输入信号源,是用户终端设备研发和卫星导航信号系统验证的重要工具.早期的射频合成技术产生的信号的精度和通道一致性较差,随后的模拟中频合成技术存在通道间偏差的问题,而目前常用的数字中频合成技术存在相位抖动问题,所以本文基于PXI Express(PXIe)总线的软件无线电架构,设计并实现了一款采用数字基带合成技术的软硬件结合模拟源.模拟源上位机数学仿真软件采用图形化编程语言LABVIEW开发,实现简单,开发效率高,最终生成数字基带合成信号;模拟源硬件则使用美国国家仪器公司(NI)模块化的虚拟仪器,接收并处理上位机产生的数字基带合成信号,最终产生用户终端设备可以接收的全球定位系统(GPS)射频信号.利用频谱分析仪观察模拟源输出信号的频率和带宽,验证了GPS模拟源仿真信号的正确性;利用商用接收机进行定位解算,分析静态和动态场景下的信号质量、定位结果及三轴定位误差,验证了GPS模拟源仿真信号的准确性和有效性.

Design and implementation of GPS navigation signal simulator based on PXIe bus architecture

The satellite navigation signal simulator is an important tool for the research and development of user terminal equipment and verification of satellite navigation signal system, which provides input signal source for the design, verification and testing of user terminal equipment. The accuracy and channel consistency of the signals generated by the early RF synthesis technology are poor. The subsequent analog IF synthesis techniques have the problem of channel-to-channel skew. While the commonly used digital IF synthesis techniques will introduce phase jitter problems. Therefore, based on the software defined radio(SDR) architecture of PXI Express (PXIe) bus, this paper designs and implements a software and hardware combination simulator using digital baseband synthesis technology. LABVIEW graphical programming language, simple and high efficiency, is adopted to develop mathematics simulation software in the host computer, and the software finally generates synthesized digital baseband signals. The modular virtual instruments of national instruments(NI) are utilized to receive and deal with the synthesized digital baseband signal generated by the host computer, and then generate global positioning system(GPS) RF signals that can be received by user terminal equipment. The simulated GPS signal is verified to be correct by utilizing spectrum analyzer to analyze the frequency and bandwidth of simulator output signal. And also it verified to be accurate and effective by utilizing commercial receiver to figure out the position and to analyze the signal quality, positioning results and positioning error in static and dynamic scenes.