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  5. Synthesis of surfaces coherent images in the Fresnel region based on multichannel and multiposition signal processing

Synthesis of surfaces coherent images in the Fresnel region based on multichannel and multiposition signal processing

V. Volosyuk, S. Zhyla, M. Kripak
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Description: In the paper the process of high-resolution coherent images restoration is divided into two stages. Firstly the primary image should be recovered in the fixed multichannel antenna array and then taking into account different position and viewing angles the synthesized images can be obtained. For developing primary signal processing algorithm the geometry of remote sensing in the near-field Fresnel region is proposed and analytical expressions for the observed field at each point of the receiving area are specified. Having analyzed these expressions, basic mathematical operations of the primary coherent images restoration in multi-channel optical or radio engineering systems were developed. Resolution of these images is investigated and possible ways of its increase at the stage of the secondary processing are shown. Mainly they consist in variation the coordinates of position or viewing angles. The images obtained after the secondary processing are suggested to be called synthesized coherent images and the algorithmic or physical operations of such processing are called aperture synthesis. To study the possibilities of obtaining synthesized images, several surface remote sensing geometries have been proposed. Methods of observation according to these geometries are called multi-look mode, strip mapping mode and spotlight mode. In all these cases, it is a question of the possibility of obtaining as a result of the synthesis of aperture a new ambiguity function. Width of this function must be at least several times smaller than the width of the ambiguity function characterizing the resolution of the primary imaging system. For proposed methods of observation the basic principles of synthesized images reconstruction are developed and their resolution is analyzed. Researches show that it is not possible to increase the spatial resolution in the case of multi-look mode. Strip mapping mode allows to obtain improved resolution, that corresponds to the dimensions of the observation area. The spotlight mode have the highest resolution which is determined by the dimensions of the synthesized aperture.


Keywords: synthesized image, near-field Fresnel region, multiposition processing

Reference:
 Volosiuk, V.K., Zhyla, C.C. and Krypak, N.A. (2018), “Syntez koherentnыkh yzobrazhenyi poverkhnostei v zone Frenelia na osnove mnohokanalnoi y mnohopozytsyonnoi obrabotky syhnalov” [Synthesis of surfaces coherent images in the Fresnel region based on multichannel and multiposition signal processing], Information Processing Systems, Vol. 3(154), pp. 12-18. https://doi.org/10.30748/soi.2018.154.02.