Research On Key Technologies Of High Precision GNSS-R Signal Processing

Global navigation satellite system provides highly stable,long-term used free microwave signal resources of L-band,GNSS-R technology takes uses of these rich signal resources,build ground-based,space-based or space-borne receiver to accept and deal with the reflected signal from the ground,sea and other reflective surface,to analyse the characteristics of the reflective surface or forecast meteorological disaster.GNSS-R technology has a wide range of global coverage and large amout of GNSS data accessed,and as a hotspot at home and abroad,this technology has broad application prospects.Space-boene GNSS-R receiver can obtain a large number of real-time data covering wider area,is conducive to meteorological disaster warning and a wide range of geological survey,so the future trends of the space-boene receiver signal processing are real-time and multi-band.The GNSS-R projects of ESA and NASA had already been able to realize on-orbit multi-channel reflected signal real-time processing.In this paper,from the point of view of GNSS-R reflected signal processing,the aim of this study is to improve the accuracy of GNSS-R signal processing as well as improve the processing speed.This paper first introduces the basic principles of GNSS-R technology,including its geometric relations,reflected signal characteristics and the most important observation of GNSS-R,the Delay-Doppler two-dimensional correlation power.First of all,we have grasped the space-borne reflected data processing method and the signal-to-noise ratio lifting method provided by UK-DMC.Then,from the point of view of the GNSS-R reflection signal processing,the following work are: Firstly,the error cancellation and processing parameters correction method in the reflected signal processing are summarized,which reduces the influence of the signal DC component and the Doppler frequency;Secondly,a method to calibrate the reflection signal time delay in the non-coherent integrate method based on the delay extraction of specular reflection points is proposed.Thevalidity of the method is proved by the least square matching of the one dimensional waveform,and the actual processing results match well with the theoretical model;According to the requirement of GNSS-R signal real-time processing,a fast processing algorithm of GNSS-R signal based on double block zero padding(DBZP)and frequency domain rotation transformation is proposed for DDM generation.The computational burden and computational loss of parallel code phase correlation algorithm and fast algorithm are analyzed.Finally,the UK-DMC satellite-borne reflection data are processed by two algorithms and the simulation time-consuming and processing results were compared.The results show that the fast algorithm greatly shortens the DDM generation time and the loss of the processing result is small.