Compatibility Analysis Of GNSS Signals Under Multipath Interference

GNSS radio frequency compatibility is currently the focus of the multinational since been new questions in the past ten years. With multiple satellite navigation systems built around the world, multiple GNSS systems are combined to provide seamless global navigation and positioning services to our users. The signal spectrum from GPS, GLONASS, Galileo and Beidou are overlapped on L1 band. So the problem of compatibility between multiple systems or signal must be solved for the system performance and the national security concerns. The influence of multipath interference ignored by traditional evaluation methods is still one of the main error sources are difficult to eliminate at present. So evaluation results in the traditional methods are not enough accurate. Aiming at this problem and considering the influence of the multipath interference, the estimation method of equivalent carrier-to-noise ratio and its attenuation in GNSS intrasystem and intersystem interference were corrected in this article. In this paper, the main research works are as follows:1. Multipath signal model is set up and the mathematical expressions of navigation signals autocorrelation function and power spectral density under the multipath interference were derived and the corresponding simulation analysis. There was a conclusion that the multipath signal power spectral density increased a spectral shift and a power amplitude factor.2. In view of the BDS constellation complex constitute, simulated different satellites in satellite-earth link loss using the STK tool. Then through MATLAB simulation, impact on the rest of the system together, it effectively solved the difficult problem of complex constellation simulation.3. The mathematical expressions of equivalent carrier-to-noise ratio and its attenuation in GNSS intrasystem and intersystem interference were derived and compared with the traditional calculation method of the interference, the more comprehensive system calculation methods were put forward. The experimental results show that the GPS C/A signal intrasystem interference with the largest in the global distribution of an average of 1 to 1.2 dB and for global distribution, the value of intrasystem interference and visible satellite number are the linear relationship; The minimum intersystem interference by the total system for B1 signal with a mean of 0.045 dB, and intersystem interference by the total system for E1OS signal is the largest, with a mean of 0.7 dB.4. Considering the influence of the multipath interference, the estimation method of equivalent carrier-to-noise ratio and its attenuation were corrected. The experimental simulations were performed with the multipath interference. The experimental results show that maximum multipath interference on the C/A signal intrasystem interference with a mean variation of the equivalent carrier-to-noise ratio attenuation about 0.7 dB, while for B1 signal, mean variation is about 0.3 dB; BDS with minimum intrasystem interference and Galileo with maximum intrasystem interference; Compared to the results with multipath interference, the introduction values of the equivalent carrier-to-noise ratio attenuation are about 0.3 to 0.7 dB. For accurate GNSS compatibility evaluation, this should not be ignored, but for a rough evaluation, it can be ignored due to complexity increase with multipath interference.