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Yayın A multi-frequency iterative method for reconstruction of rough surfaces separating two penetrable media(Institute of Electrical and Electronics Engineers Inc., 2024-12-18) Sefer, Ahmet; Yapar, Ali; Bağcı, HakanA numerical scheme that uses multi-frequency Newton iterations to reconstruct a rough surface profile between two dielectric media is proposed. At each frequency sample, the scheme employs Newton iterations to solve the nonlinear inverse scattering problem. At every iteration, the Newton step is computed by solving a linear system that involves the Frechet derivative of the integral operator, which represents the scattered fields, and the difference between these fields and the measurements. This linear system is regularized using the Tikhonov method. The multi-frequency data is accounted for in a recursive manner. More specifically, the profile reconstructed at a given frequency is used as an initial guess for the iterations at the next frequency. The effectiveness of the proposed method is validated through numerical examples, which demonstrate its ability to accurately reconstruct surface profiles even in the presence of measurement noise. The results also show the superiority of the multi-frequency approach over single-frequency reconstructions, particularly in terms of handling surfaces with sharp variations.Yayın An Inverse recursive algorithm to retrieve the shape of the inaccessible dielectric objects(Ramazan YAMAN, 2024-10-16) Sefer, AhmetA regularized electromagnetic iterative inverse algorithm is formulated and im-plemented to reconstruct the shape of 2D dielectric objects using the far-fieldpattern of the scattered field data. To achieve this, an integral operator thatmaps the unknown boundary of the object onto the far-field pattern of thescattered field is defined and solved for the unknown boundary. The addressedinverse problem has an ill-posed nature and inherits nonlinearity. To over-come these, the proposed solution is linearized via Newton and regularized byTikhonov in the sense of least squares. Besides, the dominance of the shadowregion in the inverse-imaging process is exceeded by considering the superpo-sition of multi-incoming plane waves, leading to less computational cost and avery fast inversion process. Comprehensive numerical analyses are carried outto ascertain the algorithm’s feasibility, revealing that it is very efficient andpromising.
