Multi-system Satellite Navagation Signal Simulator

The Global Positioning System(GPS) is a U.S.-owned utility that provides users with positioning, navigation, and timing(PNT) services. The Beidou satellite navigation system(BeiDou(COMPASS) Navigation Satellite System) is being implemented in China for self-development, independent operation of global satellite navigation systems. With the rapid development of satellite navigation and positioning technologies, navigation systems occupy an increasingly important position in the economic, military, and everyday life. Research and development of various types of receiver products is also increasing. In order to guarantee the stability and accuracy of the receiver in all cases, we need to test the performance of the receiver. It costs a lot to test its performance under real conditions, and it’s not realistic to find a variety of different environments for testing. Therefore, the study of satellite signal simulation technology is very important.The multi-system signal simulator plays a very important role in research and development and testing stages of the receiver. It can provide simulation environment for the receiver, and the desired signal for daily location in some harsh environments. This article describes the implementations of baseband signal of the GPS &BDII multi-system signal simulator. First, the structure of the satellite signal is discribed, comprising the modulation of signal, the generation of pseudo-random sequence, spread spectrum signal processing, and navigation message data format. Then, the realization is introduced in detail, including each part of the baseband signal components and baseband system model of the multi-channel multi-system signal simulator based on DSP and FPGA technology. Then the principle and method of each signal processing modules are described, and the correctness of each module structure is verified. Thereafter, the interface of DSP and FPGA is introduced, including assignment of parameter register and definition of the communication protocol of the entire system. Finally, the function testing of this system is reported.