Research On Angle And Range Estimation In Frequency Diverse Array Radar

Frequency diverse array(FDA)radar is a state-of-the-art radar system,comparing with traditional phased array(PA)radar,the beamforming of FDA radar has the advantage of range dimension information.However,FDA radar has some problems in beamforming and target angle and range estimation.For example,the FDA radar beamforming will have the problem of periodic coupling of angle and range.FDA radar angle and range estimation will face the problem of coupling of target angle and range parameters.In addition,FDA radar combined with multiple input multiple output(MIMO)technology to form a monostatic FDA-MIMO radar can avoid the problem of target angle and range parameters estimation coupling.However,the monostatic FDAMIMO radar will have the problem of range ambiguity,which limits the maximum unambiguous detection range of the monostatic FDA-MIMO radar.In response to the above-mentioned problems faced by FDA radars and combined with angle and range parameters estimation algorithms,the main work and contribution points of this paper are summarized as follows:1)This paper derives the basic model of FDA radar and does a series of summary work on the coupling problem of FDA radar beamforming.Based on the characteristics of the FDA radar model,this paper derives the FDA radar beamforming form,and then draws the problem of angle and range coupling in the beamforming,and analyzes the reasons and characteristics of the coupling problem.In addition,this paper has done a series of concluding work on the FDA radar beamforming decoupling method,and summarizes the existing nonlinear frequency increment method and subarrays method to solve the FDA radar beamforming coupling problem.2)In this paper,a series of innovative work has been done to solve the problem of ambiguity of target range information in monostatic FDA-MIMO radar angle and range estimation.First of all,this paper analyzes the causes of the range ambiguity problem deeply;Secondly,in order to solve this problem,this paper proposes a method of dividing the subarrays at the radar transmitter to extend the maximum unambiguous detection range of the monostatic FDA-MIMO radar innovatively,which is verified by mathematical analysis and simulation,compared with the existing double pulse method,the method in this paper has the advantages of greater unambiguous detection range and less time cost of the radar system;Then,in this paper,combined with the cramérrao lower bound(CRLB)analysis of range estimation,it is concluded that the proposed subarrays method can not only extend the detection range without ambiguity,but also has the advantage of lower range estimation CRLB;Finally,aiming at the angle and range estimation problem of the proposed subarrays monostatic FDA-MIMO radar,this paper proposes angle and range maximum likelihood estimation(MLE)algorithm innovatively,and uses the alternate projection(AP)algorithm to reduce the dimensionality to achieve the purpose of reducing the amount of calculation,by comparing the angle and range estimation root mean square error(RMSE)of the proposed AP-MLE algorithm and other angle and range estimation algorithms with CRLB,it is concluded that the proposed AP-MLE algorithm has the advantages of high precision and super-resolution estimation.3)In this paper,aiming at the coupling of angle and range estimation in FDA radar,this paper has done a series of summary and innovative work.First of all,this paper comprehensively and systematically explains the reasons for the coupling problem of angle and range estimation in FDA radar;Secondly,this paper summarizes the existing FDA radar angle and range decoupling estimation methods,and finds that the existing methods require special design of the FDA radar array structure to construct a differentiated array phase factor,this will increase the complexity of the FDA radar system,and the double pulse angle and range decoupling estimation will also increase the time cost of the radar system;Next,in view of the shortcomings of the existing methods,this paper firstly proposes to use multipath reflected wave signals to solve the coupling problem of FDA radar angle and range estimation,and this method does not require special design of the array,and directly uses the multipath reflection waveform signal in the environment to realize the angle and range decoupling estimation,which is simple and effective without additional cost;Then,considering the coherence of the direct wave signal and the multipath reflected wave signal in the FDA radar multipath signal model,this paper derives the angle and range general multiple signal classification(G-MUSIC)decoherence estimation algorithm,and also gives the angle and range decoherence MLE algorithm,in order to reduce the computational cost,this paper uses the AP algorithm to reduce the dimensionality of the above two algorithms,and verifies the correctness and effectiveness of the algorithm by comparing the angle and range RMSE estimated by the algorithms to the angle and range estimation CRLB;Finally,the FDA radar multipath signal model given in this paper is the first time that FDA radar has been applied to the field of target low angle estimation,compared with the disadvantages of traditional phased array radar and phased array MIMO radar that low angle estimation requires prior information about the target range,FDA does not require prior information about the target range,and can directly realize the joint estimation of low angle and range of the target.