A novel approach for the solution of forward and inverse problems associated with near field microwave imaging systems

Date

2023-8

Author

Dalkılıç, Akın

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In recent near field microwave imaging systems, the transmitters and receivers are arranged in multiple-input multiple-output (MIMO) configuration. In these systems, imaging is regarded as an inverse problem. For the solution of the inverse problem, the forward problem is required to be constructed with certain approximations. Among principal ones of these approximations is the low contrast assumption between the electrical properties of the object and the ambient medium. The object being in the far zone of the transducers and vice versa is another principal approximation. Although these approximations are crucial for the solution of the inverse problem, they limit the accuracy of the solution, because the approximations are often not realistic in representing the actual object properties and modeling the measurement setup. This thesis study presents three significant contributions in the field of near-field microwave imaging techniques. Firstly, for image reconstruction, an optimization problem involving the current density distribution and the dielectric and conductivity profile of the body is addressed using the alternating minimization technique. By handling the subproblems for each unknown variable separately and utilizing total variation regularization, the proposed reconstruction method enables efficient and fast solutions for the inverse problem. Secondly, the study investigates the impact of different antenna polarizations and the number of antennas on imaging performance, a crucial aspect previously overlooked in experimental studies. The results demonstrate the potential of polarization diversity to enhance imaging results in space-constrained settings. Lastly, by efficiently utilizing near-field data obtained from full-wave analyses of antennas, the proposed methodology overcomes the computational complexity of full-wave solution approaches for the forward problem and allows for practical implementation in the image reconstruction process.

Subject Keywords

Near field microwave imaging, Forward problem, Inverse problem, Image reconstruction, Polarization diversity, Alternating minimization

URI

https://hdl.handle.net/11511/105227

Collections

Graduate School of Natural and Applied Sciences, Thesis