Research On In-Pulse Fine Feature Analysis Of Frequency Modulated Signal In Radar

The detection and classification of complex radar signal has been a keytechnology for electronic warfare.The traditional method employing direction ofarrival,carrier frequency,time arrival,pulse width and amplitude can not meet therequirements of application in signal processing of electronic warfare withever-increasing number of radar emitters and different radar waveforms.It isnecessary to analyze and extract the in-pulse fine features of radar signals forefficient recognition of radar signals.In this thesis,the extraction of in-pulse finefeature of frequency modulated signals in radar is investigated,and the fast andaccurate parameter estimation and detection of multicomponent frequencymodulated signals are studied extensively.The main results are as follows:1.The conception and construction of electronic warfare are introduced.Thepresent research of in-pulse fine feature analysis of radar signals in modern warfareis presented.And the content,evolution and present status of nonstationary signalanalysis are concluded.The origin of time frequency analysis in the point of signalrepresentation is reviewed.And the development trend of time frequency analysis isintroduced.2.Smoothed pseudo polynomial Wigner-Ville distribution (SP-PWVD) isproposed to reduce interference terms which present when higher order polynomialphase signal (PPS) is represented by lower order polynomial Wigner-Villedistribution (PWVD).The properties of SP-PWVD are concluded.High orderPWVD is designed by optimal method.The scale transformation of the non-uniformsampling of the signals in the high order instantaneous moment of PWVD isperformed by fast Fourier transform (FFT) interpolation.3.After making an in-depth analysis of the interference terms and localdiffusion behavior of the adaptive diffusion process,we combine the adaptivediffusion with difference method to eliminate the stubborn interference terms.Andwe substitute the Hesse matrix for the gradient square tensor to obtain the local diffusion direction,and thus improve the readability of the adaptive diffusiondistribution.A scheme of digital realization is provided.4.The FFT and quadratic interpolation are used to improve the precision ofproduct high order ambiguity function (PHAF).A method based on iterativefiltering and RELAX is proposed to provide accurate parameter estimation for highorder muticomponent PPS at low signal to noise ratio (SNR).Difficulties indetection of higher order and multi-component PPS by PHAF are discussed.Adetector based on iterative filtering and maximum magnitude of PHAF is proposedafter an analysis of detector based on PHAF magnitude.And the selection of orderand delay sets is studied.5.A detector based on second order difference of Radon ambiguity transform(RAT) is proposed to improve detection probability of linear frequency modulatedsignal (LFM) after analysis of problems with detector based on magnitude of RATin low SNR.A secondary search strategy of RAT is proposed for fast and accurateparameter estimation of LFM.Dechirp based on FFT and quadratic interpolation isproposed to analyze LFM at low SNR.Comparisons of Radon Wigner transform,dechirp,PHAF and product cubic phase function are performed and the emphasis isplace on time collapsed,signal to noise ratio threshold and number of samplesbetween dechirp and PHAF.6.At last,the whole dissertation is concluded.And some further researchfrontiers of frequency modulated signal detection and parameters estimation arepointed out.