Enhancement of SAR Image Resolution with Implementation of Circular GB-SAR System

University essay from Blekinge Tekniska Högskola/Sektionen för ingenjörsvetenskap

Abstract:

Radars were used for surveillance and remote sensing but nowadays they handle a vast range of applications, radar imagery being one of them. The need for high resolution images was inevitable which lead to Synthetic Aperture Radar (SAR) systems. SAR plays a prominent role in remote sensing applications and geophysical studies. SAR is an imaging radar which inherits advantages over conventional optic sensors since they can be used irrespective of the climatic conditions and sunlight due to the merits of microwaves. In addition to these benefits SAR generates a finer resolution 2-D image which cannot be achieved with conventional real aperture radar. Ground-based SAR has a wide range of applications like monitoring of post land slide surface to estimate slope displacements, observation of Tsunami affected area for ground surface movements, etc... In the modern times, improvement in the resolution was still anticipated and this requirement for technological advancement forces the researchers to implement new strategies for the enhancement of SAR image resolution in both azimuth and range directions. In this thesis we use the circular aperture technique for resolution enhancement with practical implementation of an experimental model at the laboratory and analyzing the results with those corresponding to linear aperture. In this thesis we make use of Ultra wideband–Ultra wide beam (UWB) ground based SAR system (GB-SAR) system which achieves better resolution SAR images in both azimuth and range directions. GBP (Global Back Projection) algorithm is used to reconstruct the image from the pulse compressed back scattered echo signal. This thesis is divided into two parts: the first part concentrates on the establishment and data processing of GB-SAR where as the second part focuses on the resolution enhancement of SAR images using circular apertures. In the first part experimental GB-SAR system is introduced and the data processing with radar signal reconstruction and image processing technique is explained in detail. The SAR image formed by the experimental data is examined and compared with the assessments in theory. In the second part an experiment with circular aperture i.e. GB-CSAR system is performed to obtain the enhancement of image resolution. The SAR image formed with the experimental CSAR data is compared with the experimental LSAR image and resolution is investigated. Thus analysis on efficiency of radar resolution between Linear SAR and Circular SAR is established with practical implementation of SAR system at the laboratory. Results emphasize the significance of Circular SAR over Liner SAR.

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