Radar Detection Techniques Of Extended Targets And Their Application

Radar target detection is a classic problem in the research area of radar signal pro-cessing. Traditional research is usually for low-resolution radars and treats the target asa point target. When the target's dimensions are greater than the radar's spatial resolu-tions, i.e., when the target is an extended target, the detection techniques based on theassumption of point targets are difficult to make full use of the characteristics of the tar-get's echoes, and to obtain optimal detection performance. In recent years, the extensiveapplication of broadband radars and the expansion of radar application have brought upnew requirements for the design, robustness, and adaptability of extended target detectors.This dissertation, facing the requirements of the radar detection of extended targets andaimingtoimprovetherobustnessandadaptabilityofdetectors,studiesnewtechniquesandnewapplicationoftheradardetectionofextendedtargetsfortypicalapplicationscenarios.In the aspect of new techniques of the radar detection of extended targets, the char-acteristics of extended targets'echoes are analyzed, and some echo models of extendedtargets are established first. On this basis, for the problems of the detection of extendedtargets in noise, clutter backgrounds, new techniques of the parametric, nonparametricdetection of extended targets are studied. The work includes:·Characteristics and modeling of extended targets'echoes: An echo model based onthe geometrical theory of diffraction is established for the scattering centers of ex-tended targets. The distributions of the amplitudes and polarization of the echoes oftypical extended targets are deduced. A frequency-domain echo model and a time-domain echo model are established for high-speed and low-speed extended targets,respectively.·Parametric detection techniques of extended targets: Five single-pulse parametricdetectors are designed and analyzed for extended targets with different a priori infor-mation (amplitudes, polarization, and phases of the target's echoes, and distributionsof the target's scattering centers, etc.). A quasi-optimal multi-channel single-pulseextreme detector, which is efficient, robust, and practical, is proposed, and a high-precision approximate analysis method is proposed for its detection performanceanalysis. For low-speed extended targets, a multi-pulse parametric detector witha time-frequency-spatial and polarization domain joint processing structure is de-signed and analyzed. Based on this detector, some multi-pulse extreme detectors are proposed and analyzed for extended targets with homogeneous, non-homogeneousDoppler spectra. For the problem that a high-speed extended target is prone to crossone or more range cells during the period of the radar's multi-pulse observation, amulti-pulse parametric detection method based on the keystone transform is pro-posed and analyzed, which can significantly improve the detection performance ofhigh-speed extended targets.·Nonparametric detection techniques of extended targets: For the detection of pointtargetsinunknownclutterenvironment,anonparametricdetectornamedBlind-CFAR(constantfalsealarmrate)detectorisproposed,andtwoBlind-CFARdetectionschemes,whicharebasedonthePadéapproximationmethodandthemaximumentropymethodrespectively, are designed and analyzed. On this basis, based on the pulse integra-tion methods of non-coherent integration, extreme integration and binary integra-tion, three Blind-CFAR detectors for extended targets are proposed and analyzed.The Blind-CFAR detectors have overcome the shortcoming of the existing CFARdetectors that they are over-relied on the accuracy of parameter estimation, and areapplicable to target detection in many types of clutter environment.Based on the design and analysis of the extended target detectors, new applicationof the extended target detection techniques in the radar detection of aircraft wake vorticesis studied, and the radar detectability of aircraft wake vortices under typical atmosphericconditions is analyzed for aviation safety, anti-stealth and other applications. The workincludes:·The electromagnetic scattering mechanism and radar target characteristics of aircraftwake vortices in clear and precipitation air are analyzed. The RCSs (radar cross sec-tions) and Doppler spectra of aircraft wake vortices in clear and precipitation air areobtained based on the radar detection experiments of aircraft wake vortices and the-oretical analysis respectively. An echo model and a detection model are establishedfor the radar detection of aircraft wake vortices. A locally most powerful (LMP)detector of aircraft wake vortices and two generalized likelihood ratio test (GLRT)detectors of aircraft wake vortices with homogeneous, non-homogeneous Dopplerspectra are deduced and analyzed, which provides a theoretical basis for the radardetection of aircraft wake vortices.·Radar equations for the detection of aircraft wake vortices in clear and precipitation air are deduced. The detection range of aircraft wake vortices with typical radarsystemsisanalyzed,andiscomparedwiththeradardetectionrangeofstealthaircraft.The results show that, under precipitation conditions, the detection range of aircraftwake vortices is expected to be greater than that of stealth aircraft.The results of this dissertation on target detection are of important theoretical signifi-cance for broadband and distributed radar target detection, and the results on the detectionof aircraft wake vortices are of great potential in aviation safety, anti-stealth and otherapplications.