Study On Technologies Of Anti-jamming Performance Evaluation And Optimization For GNSS Antenna Array Receivers

Anti-jamming is one of the essential functions of military GNSS equipments.A test and evaluation method,which is accurate,efficient and comprehensive,is not only an important part of anti-jamming technology,but also a guide for both the research and the enginnering development of anti-jamming technology.The traditionnal test method and evaluation theory exposed gradually many problems in its accuracy,efficiency and comprehensiveness.The research of performance evaluation method and related theories for GNSS anti-jamming receivers has its important theoretical significance and values on application.In this thesis,the in-depth study is about the anti-jamming performance evaluation and optimization method of GNSS antenna arrays receivers.The main work and innovations are as follows:Limitation and dissatistacion exsist for the traditional wire test method of GNSS antenna arrays,mainly on the jamming-signal-ratio(JSR)simulation range and the broadband interference simulation accuracy.Complex structure,high cost and difficult to promote and apply are also problems.To solve these problems,a high-precision array signal simulation method based on cable delays is proposed in the thesis.An error model of array signal simulation was established,the factors that cause the incidence angle simulation errors were analyzed theoretically and numerically,and the channel pahse inconsistency in RF devices and the error caused by difference between the propagation velocity of electromgnetic waves in transmission lines and the velocity of light was corrected,which effectively improved the design accuracy of array simulators.The results show that under the condition of 4-element planery array,the simulation accuracy of incidence angle elevation is better than 2°,and that of azimuth is better than 1°.Anechoic chamber testing is an essential part of the development for antenna arrays anti-jamming receivers.However,due to the limited space of anechoic chambers,the incident signals are actually spherical waves,rather than planery waves in the classical theory model,i.e.,the near-field effect.In this thesis,an near-field error analysis method for anechoic chamber,which is based on array wave path equivalence,was proposed.The actual incidence angles of spherical waves are equivalent to certain incidence angles of plane wave which is identified naturally by the processing model in receivers.The influence of near-field effect towards the performance evaluaiton and test of antenna array anti-jamming receivers were studied deeply,respectively from array phase differenc,direction of arrival,nulling depth and pattern deterioration.The results show that the nearfield error has no effect on 2-element arrays,and the effect goes only on multi-element arrays.Results show that for multi-element arrays,when the incident angle is 30°,the maximum JSR test capacity of the anechoic chamber with a transceiver distance of 100 times the wavelength is about 84 d B.Singular points are a phenomenon in antenna arrays anti-jamming technology that the smaller array gain goes with the larger physical angle of signal interference,which do not accord with the traditional views.Of the anti-jamming performance test of antenna arrays,results given by test with traditional typical scene are ususlly optimistic,while traversal scene test is hard to be implemented in engineering.To solve these problems,an index system of singular points was estabulished based on the inconsistency difference between the physical angles of interferences and signals and the signal gain.This index system can be used to quantitatively analyze and accurately position the singular points corresponding to given signal DOA.Aimed at anti-jamming performance test and evaluation of antenna arrays under particular scenes in anechoic chambers and laboratories,a new rigorous test scene design method based on singular points was proposed,which simulate the bad scenes in practical application environment.The method has a larger covering square on incidence angle areas of different performance,and gives more objective results of antenna arrays' actual performance.Simulation results show that in the newly designed rigorous test scenes,the minimum physical angle between three interferences and signal is 72°while the mean value is 81°,however,the array gain at signal direction is less than-1d B,which is much lower than 6d B in usual cases.Under the conditions of strong broadband interference,due to the frequency aliasing of interference,the noise floor will be raised,the useful signals will be deteriorated,and the interference suppression performance can be worsened.Based on interference to aliasing noise ratio,the analytical model of sampling rate and extra-band suppression was established,the influence of the two factors against interference suppression performance was analyzed.A parameters optimizing method of anti-jamming receivers in restricted thermal noise deterioration conditions was proposed.The analysis results show that the effect of improving the sampling rate is inconspicuous,it is more important to improve the performance of extra-band suppression,and the interference suppression performance toward broadband interferences of different types is different.In restricted conditions(thermal noise deterioration not bigger than 3d B,sampling rate is 4 times of the bandwidth),if broadband interference of 60 d B JSR is need to be suppressed,the extraband suppression depth need at least to be 44 d B.The analysis results provide a quantitative basis for mutual balance and optimization design of the sampling rate and band suppression depth of antenna array anti-interference receivers.Finally,the research achievements and there applications are summarized,the work to be undertaken in the furture is looked forward.All the research achievements in the thesis have already been tested in practice,and have been successfully applied to the performance evaluation of anti-jamming receivers.