Research On Radar Target Multi-Dimensional Parameter Measurement And Estimation For Millimeter Wave Seeker

The battlefield threats such as tanks,armored vehicles,helicopters and UAVs take advantage of complex groud environment for the penetration,which put forward austere challenges for the target detection and recognition of the millimeter wave radar seeker in the ground clutter environment.The millimeter wave radar seeker has high measuring accuracy in the area domain,time domain,frequency domain and polarization domain,but the target classifier is limited by 1)complicated electromagnetic environment and target dynamicity,2)limited capability of data processing units due to missile-borne condition,3)high real-time requirement.Hence,the research of target recognition in millimeter wave radar seeker should focus on exploring the ability of target feature extraction to reduce the complexity of the target recognition and classification algorithm.The paper units target range,velocity,polarimetric scattering matrix and micro-motion parameters as the “target multi-dimensional parameter”,which contains all dimensional electromagnetic wave modulation effect of the target such as time,frequency,phase and polarimetry and describes the target feature fundamentally and comprehensively from multiple aspects.The measurement and estimation of target multi-dimensional parameter are the foundation of the feature extraction in millimeter wave radar seeker.In the motivation of the practical target recognition technology in the millimeter wave radar seeker,this paper conducts the thorough research concentrating on the fundamental issue of target feature extraction,that is,target multi-dimensional parameter measurement and estimation.A part of the research results are validated by the field experiments using the radar prototype designed in this paper.Firstly,the target parameter estimation(range,velocity and polarimetric scattering matrix)under frequency-stepped signal in millimeter wave radar seeker are researched.The full polarimetric HRRP mathematic models under frequency-stepped signal are analyzed,then to address the HRRP defocus caused by range-velocity coupling,a parameter estimation method that estimates the range,velocity and polarimetric scattering matrix based on Fractional Fourier Transformation(FrFT)is proposed.However,the range resolution will be limited by the synthetic bandwidth in the FFT or FrFT method.Then,a joint FrFT-MUSIC parameter estimation and imaging method is proposed for dealing with the range resolution issue,which has higher range resolution and estimation precision compared with the FrFT method.Secondly,the target rotation parameter estimation method in the pulse-doppler signal and frequency-stepped signal are researched on the background of helicopter recognition.The echo feature of the rotational scattering center under the pulse-doppler signal and the frequency-stepped signal are analyzed respectively.A new rotation parameter estimation method based on the temporal difference in the pulse-doppler signal is proposed,which is simple and has a fast computation time.A rotation parameter estimation method based on FrFT in the frequency-stepped signal is proposed,which is based on the complete mathematic model and uses the time-varying frequency modulation rate of the echo to estimate the rotation parameter.Thirdly,the target parameter estimation methods based on the joint polarimetry-micromotion feature are researched.All elements of the polarimetric scattering matrix are reserved in the full-pol time-frequency plane built through the short-time Fourier transform(STFT),while only the power of each element can be extracted in the full-pol timefrequency plane built through smoothed pesudo-Wigner-Ville distribution(SPWVD).A rotation parameter estimation method based joint polarimetry-micromotion feature is then proposed for the minor-radius rotation and the time-varying-radius rotation,which uses the time-varying period of the polarmetric scattering coefficient to extract the rotation parameter.Fourthly,concentrating on the experimental demands in the multi-dimensional parameter estimation research of the millimeter wave radar seeker,a W-band multi-dimensional target feature measuring radar prototype based on the digital variable polarimetric mode is designed.The fundamental principles and the composition of digital variable polarimetric mode are elaborated.Then,the measuring error model of the polarimetric scattering matrix is derived from the basic error model.A W-band multi-dimensional target feature measuring radar prototype based on digital variable polarimetric mode is developed.It shows that the radar prototype has the high precision measurement ability in the area domain(beamwidth 1.6°,monopulse angle measurement),time domain(range resolution 0.075 m),frequency domain(wavelength 3mm,high doppler sensibility)and polarization domain(work under H-V linearly polarized base or L-R circularly polarized base,compatibility of multiple polarimetric measuring mode).A part of the parameter estimation methods proposed in this paper are validated by the radar prototype.Finally,experimental research on the target polarmetric feature of the simple and complex target is conducted using the radar prototype.A threat target detection method based on the polarimetric scattering entropy decomposition theory is proposed,which has the ability to locate the position of a tank in typical ground surroundings(trihedral corner reflector,house and boskage)and has the characteristics of attitude-insensitivity.