Resolution Properties Of Passive Radar System Based On GNSS Signals

There are many advantages of passive radar system with GNSS(Global Navigation Satellite System)satellite as the non-cooperative illumination,such as wide signal coverage,short revisit period,considerable amounts of available illumination,simple structure,good adaptability in application and so on,which make it well suited for image monitoring in high-risk landslides,glaciers and snows.By using this passive radar system,the shortcomings of the traditional SAR system,such as long revisit period and high cost,will be overcomed in the future application for real-time warning for natural disasters such as landslides,glacial debris flow.So this passive system has been drawing more and more attention in recent years.Due to the narrow-band signal of GNSS,the resolution corresponding to the signal bandwidth for a bistatic passive radar system with a GNSS satellite as illuminator and a fixed receiving station is too low to meet the requirement of practical applications.Therefore,a multi-aperture passive radar imaging system,which consists of multiple GNSS illuminators and a few fixed ground receivers,or even single one,is studied in this paper.Because of the increase in number of illuminator and receiver and extension of aperture,the resolution of the system is effectively improved.The GNSS signal structure and the satellite orbits are constant for passive radar system,the number of the receiver stations and its location is the only two adjustable parameters to optimize the resolution fo this system.This paper mainly focuse on the relationship between the system imaging resolution and configuration of receiver station,and the optimization method for configuration of receiver station is also discussed.First of all,the spatial spectrum theory is introduce to research the spatial spectral characteristics of bistatic or multiple passive radar system based on the GNSS signals.Because the system resolution is a direct result of the size of the total support region in spatial spectrum,the theoretical analysis and experimental simulation is implemented to analyze the change of total support region caused by varying configuration of receiver station and its effect on the system resolution.The analysis results show that the theoretical resolution of the passive system with multiple GNSS illuminators and single receiver is not changed with the varying of the receiver location.According to the analysis results,some guideline for optimization of configuration of receiver station is summarized in this paper.Secondly,ambiguity function is an important tool for analyzing the imaging resolution,so it is used to further analyze the influence of receiver station configurations on the system resolution.The the ambiguity function formula of a passive radar system with multiple GNSS illuminators and multiple receivers is deduced,and the 3d B projected contour area of ambiguity function is introduced as resolution cell to evaluate the system resolution quantitatively.Experimental simulation shows that the location of the receiver has no influence on the resolution of the system.Finally,the comprehensive utilization of various satellite navigation systems is researched.Some guideline for satellite selecting and optimization of configuration of receiver station is summarized.