Reseach Of Satellite Navigation Signal Generating Based On Microwave Vector Signal Generator

The satellite navigation signal simulator, which is one of the key equipment in the development and performance evaluation of high performance receivers, can generate multi-system satellite navigation signals with complex scene errors. It can provide high precision simulation signals for the testing, evaluation and verification of navigation terminals in laboratory and other indoor environments. Based on the microwave vector signal generator, the GPS and Beidou satellite navigation signal simulation system is studied in this paper. The major contents of this paper are submitted as follows.1. The generating scheme of GPS and Beidou satellite navigation signal is designed on the hardware platform of the vector source. The satellite navigation data file is transferred to the vector signal generator through Ethernet, and the navigation data is transferred to the DDR2 by the PCI bus in the arbitrary wave mode. After reading the navigation data from DDR2, digital intermediate frequency signal is generated by parallel-to-serial conversion, data mapping, interpolation filter, up conversion and band-pass filter. The satellite navigation signal is generated by the analog intermediate frequency signal modulation, which is after digital-to-analog conversion, with a radio frequency carrier.2. In the process of system realization, the control of DDR2 is achieved by FPGA programming. The IF signal generating module of GPS and Beidou, which includes data mapping, resampling filter, carrier frequency conversion and band-pass filter is designed in this paper. In order to avoid the introduction of the DC component and carrier leakage, the sample point mapping is designed. The FARROW filter of classical structure is implemented, and solves the interpolation problem of arbitrary sampling rate data in the resampling part. In order to realize satellite navigation signal spectrum shifting to reduce spectrum aliasing, sub carrier is designed according to the CORDIC algorithm. The transfer scheme of cross clock domain which used to ensure the stability of data transmission is designed.3. The performance of the system is tested by the acquisition of intermediate frequency data file. The test results, which show that the GPS and Beidou satellite navigation signals generated by the system can be positioned correctly, verifies the feasibility of the proposed scheme.