Special on Marine Acoustics / Numéro spécial sur l 'acoustique sous-marine M o d e l i n g u n d ... more Special on Marine Acoustics / Numéro spécial sur l 'acoustique sous-marine M o d e l i n g u n d e r w a t e r s o u n d p r o p a g a t i o n f r o m a n a i r g u n a r r a y u s i n g THE PARABOLIC EQUATION METHOD
2015 31st International Review of Progress in Applied Computational Electromagnetics (ACES), 2015
A passive, low-profile multi-resonant Planar-Inverted-F Antenna (PIFA) element well-suited for po... more A passive, low-profile multi-resonant Planar-Inverted-F Antenna (PIFA) element well-suited for portable communications is presented. The antenna combines the optimal low-profile geometry of a planar inverted-F antenna with a double-tuned structure to create a multi-resonant element with monopole-class radiation properties. The form factor and overall dimensions are held constant for comparisons to a similar single-resonant antenna in different near-field environments.
Uludağ University Journal of The Faculty of Engineering, 2011
A two-dimensional FDTD-based subsurface imaging virtual tool is introduced. The Ground Penetratin... more A two-dimensional FDTD-based subsurface imaging virtual tool is introduced. The Ground Penetrating Radar (GPR) virtual tool can be used to generate synthetic scattering data for various subsurface scenarios. The virtual tool may be used for both educational and research purposes. Effects of different transmit/receive antenna configurations/locations, signal waveforms, scan alternatives, etc., may all be investigated. Signal and/or image processing groups can test different imaging algorithms on the scattering data generated via GrGPR and do performance analyses.
IEEE Antennas and Propagation Society International Symposium 1992 Digest, 1992
A novel approach utilizing one-dimensional (1D) wave equation based finite difference time domain... more A novel approach utilizing one-dimensional (1D) wave equation based finite difference time domain (FDTD) formulations for Lorentz-type Epsilon-Negative (ENG) medium is developed. To demonstrate the validity and accuracy of the formulation, reflection of a plane wave normally incident at free space-ENG interface is compared with the analytical solution. Moreover, propagation characteristics of Lorentz-type ENG medium is investigated using the FDTD formulations both for wave equation and Maxwell's curl equations in 1D case. Comparisons of memory and computational time requirements of both formulations are given.
Turkish Journal of Electrical Engineering Computer Sciences, Apr 4, 2006
Public understanding of science and scientific literacy is discussed. Scientific method, scientif... more Public understanding of science and scientific literacy is discussed. Scientific method, scientific process and scientific filter are reviewed accordingly. Basic terms of measurement and numerical calculation are outlined. Finally, fundamental requirements of scientific literacy and critical response skills are presented.
International Journal of RF and Microwave Computer-Aided Engineering, 2013
This special issue entitled ''Modeling and Simulation Challenges in Microwave Engineering'' conta... more This special issue entitled ''Modeling and Simulation Challenges in Microwave Engineering'' contains invited/ selected articles from The 12th Mediterranean Microwave Symposium (MMS 2012, http://mms.dogus.edu.tr), which was held at Dogus University during September 2-5, 2012 at the same time together with The 6th URSI-Turkey National Assembly and Congress (URSI-Turkey 2012, http://ursi.dogus.edu.tr). Technical programs of MMS 2012 covered a vast array of electromagnetic and microwave topics, including microwave circuit design and applications, the latest breakthroughs in antenna design, wireless communications, exotic materials, biomedical applications, numerical methods, etc. A series of short courses/tutorials were also organized by esteemed experts/scientists (all are IEEE Fellows/Distinguished Lecturers): Prof. Pyotr Ya. UFIMTSEV (father of the PTD and stealth design), Prof. Dr. Constantine BALANIS (world-wide known antenna master), Prof. Dr. Levent GÜ REL (world record holder of electromagnetic solvers with billions of unknowns), Prof. Dr. Shiban K KOUL (worldwide expert on microwave teaching), Prof. Dr. Sembiam RENGARAJAN (master on waveguide slot antennas), and Prof. Dr. Ö zlem Aydın Ç _ IV _ I (European lecturer on MEMS). It was also once in a lifetime opportunity having two keynote speeches on the History of the Diffraction during the opening session with two esteemed scientists. First, Prof. Ufimtsev addressed ''Fifty Year of Physical Theory of Diffraction (PTD).'' Then, Prof. Balanis summarized ''Geometric/Uniform Theory of Diffraction and Its Applications.'' The first article in this issue, entitled ''Fifty Years of Diffraction,'' prepared by Balanis, Sevgi, and Ufimtsev summarizes these keynote speeches. The other articles discuss different modeling and simulation aspects in electromagnetics and microwave engineering. I express my gratitude to all contributing authors.
This paper aims at a broad-brush look at certain technological and educational challenges that co... more This paper aims at a broad-brush look at certain technological and educational challenges that confront wave-oriented electromagnetic (EM) engineering in the 21 st century, in a complex computer and technology-driven world with rapidly shifting societal and technical priorities. Simulation strategies for complex EM systems, both analytic and numerical, are reviewed and categorized, and are illustrated on selected practical complex multicomponent system scenarios currently under investigation in Turkey. Educational issues to ensure proper multidisciplinary exposure of new generations of computer-weaned students, who will have to deal with these problems, are touched upon as well.
─ Analysis of the structure of the level sets of transducer power gain and voltage gain of a two-... more ─ Analysis of the structure of the level sets of transducer power gain and voltage gain of a two-port network enables a semi-analytical method for finding the extrema these performance indicators as the port terminations vary in bounded rectangles in the complex plane. In particular, we show that the extrema are necessarily attained in small-dimensional subsets of the given rectangles. This provides efficient means to assess the impact of variability in the port terminations numerically. As an example, we study how variability in the port terminations affects the performance of a biotelemetry system composed of magnetically coupled small loops with highly sensitive impedance matching properties. Index Terms ─ Sensitivity analysis, tolerance analysis, transducer power gain, two-port networks, voltage gain.
─ In this paper, a new perfect magnetic conductor (PMC) substrate for improving the directivity o... more ─ In this paper, a new perfect magnetic conductor (PMC) substrate for improving the directivity of patch and dipole antennas is introduced. We used biased grounded ferrite to construct this new substrate. The most important difference between this substrate and the other artificial magnetic conductor (AMC) structures is the homogeneity. A conventional electromagnetic AMC has a periodic nature and as a result it is not homogenous but this novel substrate is homogenous. The results show that the directivity of both the patch and the dipole antennas is improved surprisingly in the presence of this novel homogenous PMC substrate. The physical reasons for the improvements are also given. Moreover, at the last section, we have calculated the magnetic loss of this magnetic anisotropic substrate. Index Terms ─ Biased-grounded ferrite, dipole antenna, directivity, Faraday rotation, magnetic loss, patch antenna.
Special on Marine Acoustics / Numéro spécial sur l 'acoustique sous-marine M o d e l i n g u n d ... more Special on Marine Acoustics / Numéro spécial sur l 'acoustique sous-marine M o d e l i n g u n d e r w a t e r s o u n d p r o p a g a t i o n f r o m a n a i r g u n a r r a y u s i n g THE PARABOLIC EQUATION METHOD
2015 31st International Review of Progress in Applied Computational Electromagnetics (ACES), 2015
A passive, low-profile multi-resonant Planar-Inverted-F Antenna (PIFA) element well-suited for po... more A passive, low-profile multi-resonant Planar-Inverted-F Antenna (PIFA) element well-suited for portable communications is presented. The antenna combines the optimal low-profile geometry of a planar inverted-F antenna with a double-tuned structure to create a multi-resonant element with monopole-class radiation properties. The form factor and overall dimensions are held constant for comparisons to a similar single-resonant antenna in different near-field environments.
Uludağ University Journal of The Faculty of Engineering, 2011
A two-dimensional FDTD-based subsurface imaging virtual tool is introduced. The Ground Penetratin... more A two-dimensional FDTD-based subsurface imaging virtual tool is introduced. The Ground Penetrating Radar (GPR) virtual tool can be used to generate synthetic scattering data for various subsurface scenarios. The virtual tool may be used for both educational and research purposes. Effects of different transmit/receive antenna configurations/locations, signal waveforms, scan alternatives, etc., may all be investigated. Signal and/or image processing groups can test different imaging algorithms on the scattering data generated via GrGPR and do performance analyses.
IEEE Antennas and Propagation Society International Symposium 1992 Digest, 1992
A novel approach utilizing one-dimensional (1D) wave equation based finite difference time domain... more A novel approach utilizing one-dimensional (1D) wave equation based finite difference time domain (FDTD) formulations for Lorentz-type Epsilon-Negative (ENG) medium is developed. To demonstrate the validity and accuracy of the formulation, reflection of a plane wave normally incident at free space-ENG interface is compared with the analytical solution. Moreover, propagation characteristics of Lorentz-type ENG medium is investigated using the FDTD formulations both for wave equation and Maxwell's curl equations in 1D case. Comparisons of memory and computational time requirements of both formulations are given.
Turkish Journal of Electrical Engineering Computer Sciences, Apr 4, 2006
Public understanding of science and scientific literacy is discussed. Scientific method, scientif... more Public understanding of science and scientific literacy is discussed. Scientific method, scientific process and scientific filter are reviewed accordingly. Basic terms of measurement and numerical calculation are outlined. Finally, fundamental requirements of scientific literacy and critical response skills are presented.
International Journal of RF and Microwave Computer-Aided Engineering, 2013
This special issue entitled ''Modeling and Simulation Challenges in Microwave Engineering'' conta... more This special issue entitled ''Modeling and Simulation Challenges in Microwave Engineering'' contains invited/ selected articles from The 12th Mediterranean Microwave Symposium (MMS 2012, http://mms.dogus.edu.tr), which was held at Dogus University during September 2-5, 2012 at the same time together with The 6th URSI-Turkey National Assembly and Congress (URSI-Turkey 2012, http://ursi.dogus.edu.tr). Technical programs of MMS 2012 covered a vast array of electromagnetic and microwave topics, including microwave circuit design and applications, the latest breakthroughs in antenna design, wireless communications, exotic materials, biomedical applications, numerical methods, etc. A series of short courses/tutorials were also organized by esteemed experts/scientists (all are IEEE Fellows/Distinguished Lecturers): Prof. Pyotr Ya. UFIMTSEV (father of the PTD and stealth design), Prof. Dr. Constantine BALANIS (world-wide known antenna master), Prof. Dr. Levent GÜ REL (world record holder of electromagnetic solvers with billions of unknowns), Prof. Dr. Shiban K KOUL (worldwide expert on microwave teaching), Prof. Dr. Sembiam RENGARAJAN (master on waveguide slot antennas), and Prof. Dr. Ö zlem Aydın Ç _ IV _ I (European lecturer on MEMS). It was also once in a lifetime opportunity having two keynote speeches on the History of the Diffraction during the opening session with two esteemed scientists. First, Prof. Ufimtsev addressed ''Fifty Year of Physical Theory of Diffraction (PTD).'' Then, Prof. Balanis summarized ''Geometric/Uniform Theory of Diffraction and Its Applications.'' The first article in this issue, entitled ''Fifty Years of Diffraction,'' prepared by Balanis, Sevgi, and Ufimtsev summarizes these keynote speeches. The other articles discuss different modeling and simulation aspects in electromagnetics and microwave engineering. I express my gratitude to all contributing authors.
This paper aims at a broad-brush look at certain technological and educational challenges that co... more This paper aims at a broad-brush look at certain technological and educational challenges that confront wave-oriented electromagnetic (EM) engineering in the 21 st century, in a complex computer and technology-driven world with rapidly shifting societal and technical priorities. Simulation strategies for complex EM systems, both analytic and numerical, are reviewed and categorized, and are illustrated on selected practical complex multicomponent system scenarios currently under investigation in Turkey. Educational issues to ensure proper multidisciplinary exposure of new generations of computer-weaned students, who will have to deal with these problems, are touched upon as well.
─ Analysis of the structure of the level sets of transducer power gain and voltage gain of a two-... more ─ Analysis of the structure of the level sets of transducer power gain and voltage gain of a two-port network enables a semi-analytical method for finding the extrema these performance indicators as the port terminations vary in bounded rectangles in the complex plane. In particular, we show that the extrema are necessarily attained in small-dimensional subsets of the given rectangles. This provides efficient means to assess the impact of variability in the port terminations numerically. As an example, we study how variability in the port terminations affects the performance of a biotelemetry system composed of magnetically coupled small loops with highly sensitive impedance matching properties. Index Terms ─ Sensitivity analysis, tolerance analysis, transducer power gain, two-port networks, voltage gain.
─ In this paper, a new perfect magnetic conductor (PMC) substrate for improving the directivity o... more ─ In this paper, a new perfect magnetic conductor (PMC) substrate for improving the directivity of patch and dipole antennas is introduced. We used biased grounded ferrite to construct this new substrate. The most important difference between this substrate and the other artificial magnetic conductor (AMC) structures is the homogeneity. A conventional electromagnetic AMC has a periodic nature and as a result it is not homogenous but this novel substrate is homogenous. The results show that the directivity of both the patch and the dipole antennas is improved surprisingly in the presence of this novel homogenous PMC substrate. The physical reasons for the improvements are also given. Moreover, at the last section, we have calculated the magnetic loss of this magnetic anisotropic substrate. Index Terms ─ Biased-grounded ferrite, dipole antenna, directivity, Faraday rotation, magnetic loss, patch antenna.
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Papers by Levent Sevgi