Research On Bistatic Radar Imaging And Feature Extraction Of Ballistic Targets

Radar is the key sensor of the ballistic missile defense (BMD) system and it playsan important role in detection, tracking, imaging, feature extraction and recognition,guiding, interception and damage assessment of ballistic missiles. The rivalry betweenballistic missile attack and defense becomes more and more drastic. The means ofjamming and decoying become more and more complex, which makes the monostaticradar meet a great challenge. Bi-and multi-static radar systems have the ability to detectstealth target, anti-jamming and information fusion, so they regain more attention.What’s more, new developments in frequency synthesis, digital communications, andhigh-speed computing allow us to utilize these advantages. With the desirability ofapplying the bi-and multi-static radar systems for BMD, This paper studies the bistaticimaging and feature extraction method of ballistic targets. After analyzing the bistaticscattering characteristics of ballistic targets, the dynamic echo modeling in widebandbistatic radar, bistatic one-dimensional profiling and feature extraction, two-dimensionalimaging and feature extraction methods are investigated. The main contents of thisdissertation include:1. Bistatic Scattering Characteristics Analysis and Dynamic Echo Modeling ofBallistic Targets.With the equivalent electromagnetic current method, the bistatic scatteringcoefficients of rotationally symmetrical warhead model are derived in the highfrequency region and it proves that the bistatic scattering centers of this type target arelocated at the same places as the monostatic scattering centers observed on the bisectorof the bistatic angle. The wideband bistatic scattering coefficients of several types ofwarhead models are obtained via the multilevel fast multipole method electromagneticmethod and the above conclusion is validated. The bistatic scattering centers slip on thetarget when the target, transmitter and receiver is moving, so they are named as slipperybistatic scattering centers. Based on the type of scattering center model, the movingmodel of each scattering center is derived with the target translation, rotation andprecession, which provides an exact mathematic description of the moving rule of eachscattering center. Then, the dynamic echo modeling and simulation method of ballistictargets in wideband bistatic radar is introduced based on the moving model andelectromagnetic calculation data.2. Feature Extraction Based on Bistatic High-Range Resolution Profiles(HRRPs)The echo of the high speed target in wideband bistatic radar is modeled and it is thesame as the monostatic case formally, while the physical meanings are different. Theeffect on the bistatic HRRP of the velocity, acceleration and bistatic angle is analyzed. Then motion compensation is performed based on the multi-component polynomialphase signal frequency estimation and the time-range distribution image is constructedwith the HRRP sequence. A method of estimating the precession frequency and residualvelocity is proposed based on mutual correlation of the time-range distribution and thestable estimation results can be achieved. Afterwards, the whole structure andprecession features are simultaneously extracted by utilizing the symmetricalcharacteristics of ballistic targets and extended Hough transform (EHT), which providesa solution to the coupling problem of micro-motion and structure parameters undersome conditions.In the wideband T/R-R radar system, the T/R and R receivers obtain the lengthsand the locations of the monostatic and bistatic HRRPs separately. Combined with thetarget localization method, the target length and attitude angle are estimated, and thesimulation results are provided for analyzing the effect of the target location andbaseline length on the estimation errors. This is helpful for overcoming the problem thatthe length of the monostatic HRRP is sensitive to the target attitude. Then, the model ofmulti-aspect observation is introduced and a novel algorithm, which is based on themulti-aspect observed HRRP sequences, is proposed to estimate the precession angleand real target length jointly. And the effect of the radars’ distribution on theestimated errors is discussed. For the spinning targets, a method for feature extraction isproposed based on T/R-R bistatic radars. In this method, each receiver estimates someparameters via EHT firstly, then parameter association and fusion processing areperformed, finally the real rotational radius is obtained. This method is helpful forovercoming the problem that the extracted rotational radius via monostatic radar isusually shorter than the real value.3. Bistatic Two-dimensional (2-D) ISAR Imaging and Feature ExtractionThe2-D images of spinning targets obtained via the narrowband monostatic radarare always smaller than the real size. So, a novel2-D imaging algorithm is presentedbased on the connections between the mono-and bistatic echoes of the same scattererand the classical Hough transform (HT), allowing both the mono-and bistatic2-Dimages projected on the spinning plane to be obtained simultaneously. Both mono-andbistatic2-D images reflect the real size of the spinning target, so it is helpful targetrecognition.The bistatic ISAR imaging model of precession target is introduced and theoptimum imaging time is derived. Afterwards, through selecting the optimum bistaticHRRPs, a clear bistatic ISAR is obtained via the classical fast Fourier transformprocessing on condition that the procession parameter is estimated based on the mono-and bistatic HRRP sequences and EHT. When the precession parameters are unknown,the time-frequency transform method is proposed for producing the mono-and bistatic range instantaneous Doppler (RID) image sequences, then both mono-and bistaticISAR images are scaled via image registration of mono-and bistatic RID images. Thismethod overcomes the problem that the image registration precision is limited by theprecession angle in the monostatic radar. Finally, a novel method is proposed forestimating the procession angle by utilizing the moving rule of the dominant scatteringcenter in the un-scaled and scaled ISAR image sequence.