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Research On Key Technologies Of Novel Portable 8mm Passive Focal Plane Array Imaging System

Posted on:2016-02-16Degree:DoctorType:Dissertation
Country:ChinaCandidate:W WangFull Text:PDF
GTID:1108330503455247Subject:Electronic Science and Technology
Abstract/Summary:PDF Full Text Request
By passively detecting the millimeter wave radiation energy which existed naturally in the target scene, passive millimeter wave(PMMW) imaging system can form an image at any time. Focal plane array(FPA) imaging technology promotes the development of PMMW imaging, specifically the imaging methods. FPA imaging gradually turns to be the high performance multi-beam coverage scanning method. Meanwhile, the single beam scanning method is barely used nowadays. FPA imaging has many advantages, such as, simple structure, large amount of information, real time and high accuracy. It is also not easily affected by the changes of surrounding, time and climate. All these salient features make it widely used in military and civil fields.Aiming at the application requirements of portable 8mm passive FPA imaging system, this study researches on its key techniques, which includes: the imaging characteristics of focusing lens, high gain planar antipodal linearly tapered slot antenna(ALTSA), high resolution of receiver array, and the integrated structure of ALTSA feed and high-sensitivity radiometer receiver, and etc. This paper accomplishes the design of the key components in the portable imaging system, also completes the assembling of the imaging prototype and its experimental system. All these studies set the solid theoretical and technical basis for the design of practical imaging product, and have important theoretical significance and engineering application value for promoting the development of portable PMMW imaging technology.According to the diameter maximum application efficiency and antenna beam minimum block design principles, the focusing lens is more suitable for a portable imaging system than the reflector antenna. By grooving the lens, a more even and wider range of the focusing characteristics will be obtained. Based on the analysis and simulation results on the imaging distribution characteristics of the target scene after focusing by lens, this paper completes the simulation of the spacing constraint between feeding elements under different partial focal arrangement. These researches establish the theoretical and design basis for the subsequent design of the feeding antenna unit and the feed array.Afterwards, this paper gives the detailed design of three new antenna structures and feeding constructs which differ with the traditional tapered slot antenna(TSA). Three ALTSA utilize the extending metalized via of substrate integrated waveguide(SIW) and the adding periodical slots on the top. Three kinds of planar wideband SIW to coaxial connector surface-mounted transitions are applied, which include: microstrip to SIW transition, triangle-coupling-slot grounded coplanar waveguide(GCPW) to SIW transition and linearly-coupling-slot GCPW to SIW transition. The simulation and test results demonstrate that these three new antennas have better performance than the traditional TSA. The main-lobe gain is increased by 1.92 dB, side-lobe has a 1.7dB reduction, 3dB beam width is narrowed by 12 degree, and especially the rear lobe level has an 8dB reduction.Later, this paper launches the design of the portable 8mm passive FPA feeding system. The FPA feeding system is made up of ALTSA array and single refracting hyperbolic zoned lens. Based on the imaging characteristics of lens, three different single-layer-structure arrangement of ALTSA feed arrays are designed, which include: ALTSA units arranged in curve on the focal plane faced the refraction surface center of lens, ALTSA units arranged in straight line on the focal plane side by side and ALTSA units arranged in curve on the focal plane side by side. The simulation and measurement results indicate the better performances of ALTSA feeding element, by the comparisons between ALTSA feed and the same-aperture traditional horn antenna feed. Specifically, the gain of ALTSA is 1.9dB higher, and the side-lobe level is 12 dB lower after focusing by lens, as well as, the beam width is 7.5 degree narrower. Especially, the upheavals which arise on the offset focusing radiation pattern of the horn did not occur on ALTSA.Furthermore, the integrated structure of the ALTSA feed and radiometer receiver is researched and designed, in order to fatherly improve the imaging system’s portability and integration. Through simulation analysis and actual testing, this paper researches the integrated structure on its impedance performance, radiation characteristics and receiver sensitivity. The simulation and test results present that the antenna radiation characteristics and receiver sensitivity of the ALTSA-radiometer integrated structure are better than the non-integrated one. These studies provide a solid technical foundation and show a great reference value for the further integrated design of the portable PMMW imaging system.Finally, a principle prototype of 8-channel portable 8mm passive PFA imaging system is assembled. This paper also completes the construction of the experimental system, and carries out the verification experiments of the prototype’s system performances. The calibration method and imaging processing flow is researched and designed for the portable imaging system. As well as, the system control software is compiled. The software contains the function of turntable control and multi-channel data acquisition together. The portable prototype implements the imaging experiments on several typical target scenes. By comparing and analyzing these experimental result images, this paper gives us a conclusion that the portable prototype can bring out the millimeter wave images of buildings and grounded vehicles at all time and under all kinds of weather conditions.
Keywords/Search Tags:Passive focal plane array imaging, Single refracting hyperbolic zoned lens, Antipodal linearly tapered slot antenna, Substrate integrated waveguide, Portable passive millimeter wave imaging system
PDF Full Text Request
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