Architecture and implementation of a universal real-time GNSS signal simulator

This paper presents flexible and scalable architecture of the universal real-time GNSS signal simulator which has the capability of multi-user, multi-constellation and multi-frequency joint simulation. The simulator employs the network-topology framework and the architecture based on modular design includes three sub-systems: the software modeling sub-system, the GNSS RF signal generation sub-system and the interference generation sub-system. Each sub-system can run independently. The GNSS RF signal generation sub-system is a complicated part in the whole system and the implementation of this sub-system is to be considered seriously. The GNSS RF signal generation sub-system is composed of four modules, including the system clock generator, the controller, the signal generation modules and the RF module. An implementation based on the "CPU + DSP + FPGA + DAC + Analog Front-End" structure is introduced in this paper. Finally, a prototype of the universal real-time GNSS signal generator developed by Beijing Institute of Technology is exhibited.