Yazar "Aydoğan, Ahmet" seçeneğine göre listele

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    A Coarse-fine mesh approach for improved solution of 3-D inverse problems in unbounded media
    (IEEE, 2020) Aydoğan, Ahmet; Kılıç, Emre; Taygur, Mehmet Mert; Eibert, Thomas F.
    A coarse-fine mesh approach is proposed to enhance the inverse scattering method for a three-dimensional problem. The problem is decomposed into exterior and interior problems to reduce the computational cost by invoking the equivalence principle. The exterior radiation problem is formulated by a boundary integral equation which enables to estimate the unknown surface current densities. The estimated current densities form the boundary conditions of the interior problem to extract the dielectric profile. The interior problem is formulated by the finite element technique and solved by the Gauss-Newton method. The associated surfaces and volumes are respectively discretized by triangular and tetrahedral meshes in the decomposed problems. The interior problem is solved with increasingly finer meshes and restricted iteration numbers for the coarser meshes. The exterior problem is solved for each mesh to form the boundary conditions with the associated discretization while the extracted profile in the previous step is used as the initial solution in the interior problem.
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    Design of wideband impedance matching for waveguides with inhomogeneous dielectrics
    (IEEE, 2020) Aydoğan, Ahmet
    In this study, synthesis of multilayer dielectric structures is proposed to provide broadband impedance matching with waveguides. The dielectric values of the layers that fills the cross-section of the waveguide are predetermined for practical usability. It is aimed to minimize the back reflection by optimizing the unknown layer thickness values. The obtained results show that a wideband impedance matching can be performed by compact structures.
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    Dielectric measurement via partially filled and short-circuited circular waveguides
    (Ieee, 2020) Aydoğan, Ahmet; Sağlam, Serkan; Akleman, Funda
    In this study, the dielectric measurement of homogeneous materials via short-circuited circular waveguides is examined. The proposed method is numerically tested against homogeneous materials with varying permittivities, as well as in different shapes and positions. Synthetic data is generated via the moment method solution of the related integral equation. In the inversion algorithm, Newton-Raphson method with multi-frequency data is used. The complex part of the material is modeled in a linear fashion.
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    An efficient determination of field distributions in E-plane dielectric loaded waveguides
    (Taylor & Francis Ltd, 2024) Aydoğan, Ahmet
    This paper proposes a new, fast, and efficient method for determining the electromagnetic field distribution in two-port E-plane dielectric-loaded uniform rectangular waveguides. The analysis region is divided into individual blocks in the absence and presence of dielectric obstacles. The non-zero electric and magnetic field components are constructed throughout the system via the proposed method by utilizing the generalized scattering matrix method between blocks for unimodal or multimodal excitation. The resulting field distributions are compared to those obtained from commercial software, with very close agreement achieved, but with a significantly reduced computational time for the proposed method. The method is applicable in a straightforward manner and has been tested on both a filter device with relatively complex geometry and a disjoint system with a modal coupling challenge between its elements. The field components' accuracy is also tested by calculating the Poynting vector along the system. Additionally, this approach provides the global scattering parameters at the physical ports as a co-product. The proposed method has the potential to be applied to various two-port networks by using the proposed method according to the considered problem.
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    Frequency analysis of rounded shaped inductive metallic objects in waveguides via some PEC approximations and GSM method
    (2022) Aydoğan, Ahmet
    A hybrid method is proposed for the frequency analysis of rounded metallic objects inductively loaded in rectangular waveguides. The proposed method combines the efficiency of the generalized scattering matrix method (GSM) and the flexibility of the method of moments (MoM) and the fact that fields cannot exist inside perfect electric conductors. Metallic discontinuities are modelled as a dielectric medium with extreme conductivity and the volume is emptied except the surrounding area. The proposed method is tested against several structures including a band-pass filter composed of metallic rods and an arbitrarily shaped discontinuity. The accuracy of the method is compared to commercial software based on the finite element method. The proposed method is exclusively competent for the frequency analysis of rounded or arbitrarily shaped metallic discontinuities.
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    An inclusive analysis of inductive dielectric and/or metallic discontinuities in a rectangular waveguide
    (Wiley, 2021) Aydoğan, Ahmet
    An inclusive method is introduced for the analysis of different types of inductively loaded rectangular waveguides with dielectric and/or metallic obstacles. The proposed method utilizes the efficiency of the generalized scattering matrix (GSM) method on scattering analysis and the flexibility of the method of moments on problem configuration. The inductive metallic discontinuities are treated as a dielectric medium with high conductivity and the scattering analysis is accelerated by several cost reduction attempts in conjunction with GSM method and procedure of method of moments. The examined approach is tested against several structures including a metal insert filter, anH-planefilter, and a dielectric-metal obstacle-loaded waveguide both for the dominant mode region and the double-mode region. The convergence analyses on the number of calculated modes and the size of the discretized cells in the computational procedure are carried out for a comprehensive explanation of the numerical analysis. The accuracy of the method is compared to commercial software based on the finite element method. The proposed method is particularly competent for the frequency analysis of metallic and inhomogeneous dielectric discontinuities horizontally aligned in cuboid shapes.