Research On The Compatibility Of The SAR Signal And GNSS Signals

Nowadays,the world major countries are scrambling to develop and actively improve the independent global navigation satellite system.With the number of the signal structures of GNSS is in constant increase,the satellite navigation spectrum resources are limited,it is inevitable that satellite navigation systems have to share the same frequency band,the compatibility between the signal analysis is increasingly important.With respect to compatibility between GPS system and Galileo system,or Compass system with GPS system and Galileo system,are depending on spectral separation coefficients which reflected the degree of signal overlap,and effective carrier to noise ratio degradation which reflected the degree of signal degradation.The currently widely accepted definition of compatibility and evaluation criteria is that the performance degradation caused by multiple GNSS system or a single GNSS system interference is within an acceptable range,and the two parameters of spectral separation coefficients and effective carrier to noise ratio degradation are used as compatibility criteria.In this paper,the compatibility evaluation between the SAR signal as the interference signal and the signals of the various GNSS systems,is judged based on the analysis results of the receiver capture and tracking performance.According to the spectral separation coefficients determines the power spectral density of signal overlapping degree,and as an intermediate parameter to calculate the effective carrier to noise ratio,the effective carrier to noise ratio can be used for the capture and tracking of GNSS signals are interferenced by the SAR signal.Based on the AGC model of RF in the front end of receiver,the effective carrier to noise ratio and the effective carrier to noise ratio degradation under different AGC strategies are analyzed.In the capture performance analysis,the capture of the signal is generally determined by detecting the non-coherent integration amplitude.However,the receiver uses the AGC strategy and the actual situation is different,by comparing the case of the same false alarm probability and different AGC response time,the carrier to noise ratio and capture probability relationship to assess capture performance.The influence of SAR interference signal on carrier tracking of GNSS signals is the same as that of capture.The carrier-loop accuracy is calculated by the effective carrier to noise ratio.The accuracy of the PLL carrier tracking loop studied in this paper is mainly related to the bandwidth of the loop,carrier to noise ratio,and coherent integration time.In the case of a given interference signal power,the effective carrier to noise ratio is deduced and the effect of the interference on the carrier performance can be analyzed by using the effective carrier to noise ratio into the carrier tracking loop precision.Analysis of SAR signal as the interference signal interference on GNSS signals pseudo random code tracking,according to the influence of the pseudo random code tracking accuracy evaluation by Betz and PN code tracking precision analysis model is established.From the perspective of power spectrum,useful signal power spectrum,pulse interference power spectrum,using useful signal and the spectral separation coefficient and the effective carrier to noise ratio in the code tracking accuracy evaluation models based on coherent EML(Early Minus Late)and non-coherent EMLP(Early Minus Late Power)tracking loops.The influence of interference on the code tracking performance can be analyzed by calculating the code tracking error based on the effective carrier to noise ratio and the evaluation model.