| Terahertz(THz) radar not only has the advantage of high spatial resolution, goodangular resolution, strong antijamming ability, distinct Doppler characteristics,interference-free to smoke, fog and sand, but also has the anti-stealth capability as wellas penetrating the plasma sheath. Rotating antenna is one of the important componentsof the military targets, and has many characteristics that is conducive to identify by theterahertz wave irradiation. This paper focuses on the rotating antenna class targets,researches on the radar target characteristics of paraboloid reflector antenna and planarwaveguide slotted array antenna in THz regime. Basing on this, we study the syntheticaperture imaging problem of rotating paraboloid reflector antenna with THz radarsystem.The first chapter introduces the background and significance of this research topic.We summarize the development progress on terahertz science and technology, sum upthe research progress and development status of three related key techniques, which areTHz target characteristics, THz imaging radar systems and Micro-Doppler propertiesextraction and detection. The major scientific contributions of this dissertation arepresented at the end of this chapter.Chapter II exemplifies the parabolic reflector antenna of full-size models and scalemodel, studies the electromagnetic scattering mechanism and compares the results ofTHz regime with that of X-band. The CAD model of the parabolic reflector antennatarget in the optical area is established. Using the high-frequency asymptotic solver ofCST Microwave Studio2010software, the backscattered field of parabolic reflectorantenna is predictively estimated and the antenna’s single-station complex RCS matrixis computed. The target electromagnetic scattering characteristics are analyzed, such asRCS, high-resolution one-dimensional range profile, two-dimensional turntable image,time-frequency distribution etc. Finally, we research the RCS prediction problem of theplanar slotted waveguide array antenna in the terahertz regime. A hybrid method ofphysical optics and method of moments is adopted to give the calculated result of RCS.Chapter III presents a kind of wideband echo modeling method for rotatingparabolic reflector antenna target. On one hand, we establish the rotating parabolicantenna target’s RCS model in the spotlight SAR spatial Geometry, which describes thetime-varying relationship between the target’s backward scattering coefficient androtating motion. On the other hand, we study the observation system model in spotlightSAR mode, and in the range-frequency and azimuth-angle domain, we deduce thebroadband echo signal expression for point target under arbitrary movement. Theconvolution inverse projection algorithm is used to achieve the two-dimensional SARimage, then the image feature and micro-Doppler features of rotating parabolic reflector antenna are analyzed.The fourth chapter expatiates the frequency modulated continuous wave signalsystem, which is commonly used in THz radar, and points out that the distinctionbetween FMCW SAR and traditional pulse SAR lies in the continuous wave pulse dutycycle of100%, thus the "stop and go" assumption no longer holds. Examples are givento explain the parameters design principles of FMCW terahertz radar systems. Based onthe third chapter, further propose the method for micro-motion target broadband echogeneration in FMCW-SAR mode and synthetic the rotating parabolic reflector antennatarget’s Dechirp echo signal. Referring some existing FMCW-SAR imaging algorithm,we introduce the frequency scaling algorithm to simulate the point target imaging interahertz regime.The research work and main innovative contributions of this dissertation areconcluded in Chapter V. We outlook some next-step works to be done in the future. |
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