The Experts below are selected from a list of 2076 Experts worldwide ranked by ideXlab platform
Eng Leong Tan - One of the best experts on this subject based on the ideXlab platform.
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UNCONDITIONALLY STABLE LEAPFROG ADI-FDTD METHOD FOR Lossy Media
Progress In Electromagnetics Research M, 2012Co-Authors: Theng Huat Gan, Eng Leong TanAbstract:This paper presents an unconditionally stable leapfrog alternating-direction-implicit flnite-difierence time-domain (ADI- FDTD) method for Lossy Media. Conductivity terms of Lossy Media are incorporated into the leapfrog ADI-FDTD method in an anal- ogous manner as the conventional explicit FDTD method since the leapfrog ADI-FDTD method is a perturbation of the conventional explicit FDTD method. Implementation of the leapfrog ADI-FDTD method for Lossy Media with special consideration for boundary con- dition is provided. Numerical results and examples are presented to validate the formulation.
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Lyapunov and Matrix Norm Stability Analysis of ADI-FDTD Schemes for Doubly Lossy Media
IEEE Transactions on Antennas and Propagation, 2011Co-Authors: Ding Yu Heh, Eng Leong TanAbstract:Lyapunov and matrix norm stability analysis is applied on various alternating-direction-implicit finite-difference time-domain (ADI-FDTD) schemes for doubly Lossy Media. The stability analysis is performed rigorously in both time and Fourier domains. Among the schemes considered are averaging, forward-backward, backward-forward, forward-forward, exponential time differencing and backward-backward. From the analysis, it is found that all schemes except backward-backward scheme are unconditionally stable. For backward-backward scheme, the condition for stability is determined.
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unified efficient fundamental adi fdtd schemes for Lossy Media
Progress in Electromagnetics Research B, 2011Co-Authors: Ding Yu Heh, Eng Leong TanAbstract:This paper presents the unifled e-cient fundamen- tal alternating-direction-implicit flnite-difierence time-domain (ADI- FDTD) schemes for Lossy Media. The schemes presented include aver- aging, forward-forward, forward-backward and novel exponential time difierencing schemes. Uniflcations of these schemes in both conven- tional and e-cient fundamental forms of source-incorporated ADI- FDTD are provided. In the latter, they are formulated in the sim- plest, most concise, most e-cient, and most fundamental form of ADI-FDTD. The unifled update equations and implementation of the e-cient fundamental ADI-FDTD schemes are provided. Such e-cient fundamental schemes have substantially less right-hand-side update co- e-cients and fleld variables compared to the conventional ADI-FDTD schemes. Thus, they feature higher e-ciency with reduced memory indexing and arithmetic operations. Other aspects such as fleld and parameter memory arrays, perfect electric conductor and perfect mag- netic conductor implementations are also discussed. Numerical results in the realm of CPU time saving, asymmetry and numerical errors as well as speciflc absorption rate (SAR) of human skin are presented.
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Generalized Stability Criterion of 3-D FDTD Schemes for Doubly Lossy Media
IEEE Transactions on Antennas and Propagation, 2010Co-Authors: Ding Yu Heh, Eng Leong TanAbstract:This paper presents the generalized stability criterion of 3-D finite-difference time-domain (FDTD) schemes for doubly Lossy Media, where both electric and magnetic conductivities coexist. The generalized stability criterion is applicable for all 3-D FDTD schemes, such as time-average (TA), time-forward (TF), time-backward (TB) and exponential time differencing (ETD). It is reducible to either electrically Lossy, magnetically Lossy or lossless Media. The stability criterion for perfectly matched layer (PML) matching condition can also be obtained as a special case to the doubly Lossy Media. It is shown that, for doubly Lossy Media, the stability criterion for ETD and TF becomes even more relaxed, and for TB, even more stringent compared to either electrically Lossy, magnetically Lossy or lossless Media. On the other hand, the stability criterion for TA remains unchanged even in doubly Lossy Media. As numerical demonstration, the tunneling of electromagnetic wave through a very thin doubly Lossy conductor is simulated. Numerical experiments further show the maximum allowed time step as dictated by the derived stability criterion for different schemes.
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Dispersion Analysis of FDTD Schemes for Doubly Lossy Media
Progress In Electromagnetics Research B, 2009Co-Authors: Ding Yu Heh, Eng Leong TanAbstract:This paper presents the 3-D dispersion analysis of flnite- difierence time-domain (FDTD) schemes for doubly Lossy Media, where both electric and magnetic conductivities are nonzero. Among the FDTD schemes presented are time-average (TA), time-forward (TF), time-backward (TB) and exponential time difierencing (ETD). It is flrst shown that, unlike in electrically Lossy Media, the attenuation constant in doubly Lossy Media can be larger than its phase constant. This further calls for careful choice of cell size such that both wavelength and skin depth of the doubly Lossy Media are properly resolved. From the dispersion analysis, TF generally displays higher phase velocity and attenuation errors due to its flrst-order temporal accuracy nature compared to second-order ETD and TA. Although both have second-order temporal accuracy, ETD has generally lower phase velocity and attenuation errors than TA. This may be attributed to its closer resemblance to the solution of flrst-order difierential equation. Numerical FDTD simulations in 1-D and 3-D further conflrm these flndings.
Nicola Tedeschi - One of the best experts on this subject based on the ideXlab platform.
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An Analytical Study of Electromagnetic Deep Penetration Conditions and Implications in Lossy Media through Inhomogeneous Waves.
Materials (Basel Switzerland), 2018Co-Authors: Paolo Baccarelli, Fabrizio Frezza, Patrizio Simeoni, Nicola TedeschiAbstract:This paper illustrates how the penetration of electromagnetic waves in Lossy Media strongly depends on the waveform and not only on the Media involved. In particular, the so-called inhomogeneous plane waves are compared against homogeneous plane waves illustrating how the first ones can generate deep penetration effects. Moreover, the paper provides examples showing how such waves may be practically generated. The approach taken here is analytical and it concentrates on the deep penetration conditions obtained by means of incident inhomogeneous plane waves incoming from a lossless medium and impinging on a Lossy medium. Both conditions and constraints that the waveforms need to possess to achieve deep penetration are analysed. Some results are finally validated through numerical computations. The theory presented here is of interest in view of a practical implementation of the deep penetration effect.
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Inhomogeneous wave penetration in Lossy Media
2016 URSI International Symposium on Electromagnetic Theory (EMTS), 2016Co-Authors: Paolo Baccarelli, Fabrizio Frezza, Patrizio Simeoni, Nicola TedeschiAbstract:The penetration properties of inhomogeneous waves are illustrated. A theoretical approach is presented and a leaky-wave antenna design is proposed in order to verify the theoretical implications. Practical aspects related to the excitation of leaky waves able to give rise to deep penetration effects in Lossy Media are discussed and the possible implementation issues are commented.
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On the electromagnetic power transmission between two Lossy Media: discussion.
Journal of the Optical Society of America. A Optics image science and vision, 2012Co-Authors: Fabrizio Frezza, Nicola TedeschiAbstract:An overview of the problems involved in the study of electromagnetic power transmission between Lossy Media is presented. Starting from the well-known problem of the transmission at a dielectric–conductor interface, the different representations of the complex propagation vector of the plane waves are introduced. Analytical expressions to convert from one formulation to the other are obtained. Moreover, the transmission of a plane wave at the interface between two Lossy Media is taken into account. An explanation of the strange behavior of the transmitted wave is developed by means of power considerations. Finally, the interesting effect of the parallel-attenuated transmitted wave is presented, and its properties as a function of the incident phase vector amplitude are deduced.
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Deeply penetrating waves in Lossy Media.
Optics Letters, 2012Co-Authors: Fabrizio Frezza, Nicola TedeschiAbstract:The incidence of an inhomogeneous plane wave on the interface between two Lossy Media is analyzed. The analytical expressions of the incidence angle of the phase vector, for which the transmitted wave has the phase or the attenuation vector parallel to the interface, are obtained. The transmitted wave with the attenuation vector parallel to the interface is physically interpreted, finding a wave in a Lossy medium without attenuation away from the interface. The same effect appears at the interface between a lossless medium and a Lossy one.
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Generalized plane-wave expansion of cylindrical functions in Lossy Media convergent in the whole complex plane
Optics Communications, 2011Co-Authors: Fabrizio Frezza, Giuseppe Schettini, Nicola TedeschiAbstract:Abstract Electromagnetic scattering by buried objects may involve a plane-wave expansion of the related fields, which depends on the objects' geometry. Furthermore, involved Media in realistic cases are Lossy, which requires the analytic continuation of formulae known for the lossless cases, due to the complex nature of the wave vectors. This problem has been covered in a previous paper, but the expression found still does not converge in some areas of space. In this paper, a new, convergent, expression of the spectrum of cylindrical functions in Lossy Media is analytically computed and its convergence limits are discussed.
Richard Bayford - One of the best experts on this subject based on the ideXlab platform.
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Absorption and optimal plasmonic resonances for small ellipsoidal particles in Lossy Media
Journal of Physics D: Applied Physics, 2017Co-Authors: Mariana Dalarsson, Sven Nordebo, Daniel Sjöberg, Richard BayfordAbstract:A new simplified formula is derived for the absorption cross section of small dielectric ellipsoidal particles embedded in Lossy Media. The new expression leads directly to a closed form solution f ...
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absorption and optimal plasmonic resonances for small ellipsoidal particles in Lossy Media
arXiv: Classical Physics, 2017Co-Authors: Mariana Dalarsson, Sven Nordebo, Daniel Sjöberg, Richard BayfordAbstract:A new simplified formula is derived for the absorption cross section of small dielectric ellipsoidal particles embedded in Lossy Media. The new expression leads directly to a closed form solution for the optimal conjugate match with respect to the surrounding medium, i.e., the optimal permittivity of the ellipsoidal particle that maximizes the absorption at any given frequency. This defines the optimal plasmonic resonance for the ellipsoid. The optimal conjugate match represents a metamaterial in the sense that the corresponding optimal permittivity function may have negative real part (inductive properties), and can not in general be implemented as a passive material over a given bandwidth. A necessary and sufficient condition is derived for the feasibility of tuning the Drude model to the optimal conjugate match at a single frequency, and it is found that all the prolate spheroids and some of the (not too flat) oblate spheroids can be tuned into optimal plasmonic resonance at any desired center frequency. Numerical examples are given to illustrate the analysis. Except for the general understanding of plasmonic resonances in Lossy Media, it is also anticipated that the new results can be useful for feasibility studies with e.g., the radiotherapeutic hyperthermia based methods to treat cancer based on electrophoretic heating in gold nanoparticle suspensions using microwave radiation.
Sven Nordebo - One of the best experts on this subject based on the ideXlab platform.
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Physical Meaning of the Dipole Radiation Resistance in Lossless and Lossy Media: What is the Radiation Resistance of Antennas in Lossy Media?
IEEE Antennas and Propagation Magazine, 2020Co-Authors: Mohammad Sajjad Mirmoosa, Sven Nordebo, Sergei A. TretyakovAbstract:In this tutorial, we discuss the radiation from a Hertzian dipole into uniform isotropic Lossy Media of infinite extent. If the medium is lossless, the radiated power propagates to infinity, and the apparent dissipation is measured by the radiation resistance of the dipole. If the medium is Lossy, the power exponentially decays, and the physical meaning of radiation resistance needs clarification. Here, we present explicit calculations of the power absorbed in the infinite Lossy host space and discuss the limit of zero losses. We show that the input impedance of dipole antennas contains a radiation-resistance contribution that does not depend on the imaginary part of the refractive index. This means that the power delivered by dipole antennas to surrounding space always contains a contribution from far fields unless the real part of the refractive index is zero. Based on this understanding, we discuss the fundamental limitations of power coupling between two antennas and possibilities of removing the limit imposed by radiation damping.
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On the optical theorem and optimal extinction, scattering and absorption in Lossy Media
2020 14th European Conference on Antennas and Propagation (EuCAP), 2020Co-Authors: Sven Nordebo, Mats Gustafsson, Yevhen IvanenkoAbstract:This paper reformulates and extends some recent analytical results concerning a new optical theorem and the associated physical bounds on absorption in Lossy Media. The analysis is valid for any linear scatterer (such as an antenna), consisting of arbitrary materials (bianisotropic, etc.) and arbitrary geometries, as long as the scatterer is circumscribed by a spherical volume embedded in a Lossy background medium. The corresponding formulas are here reformulated and extended to encompass magnetic as well as dielectric background Media. Explicit derivations, formulas and discussions are also given for the corresponding bounds on scattering and extinction. A numerical example concerning the optimal microwave absorption and scattering in atmospheric oxygen in the 60 GHz communication band is included to illustrate the theory.
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Absorption and optimal plasmonic resonances for small ellipsoidal particles in Lossy Media
Journal of Physics D: Applied Physics, 2017Co-Authors: Mariana Dalarsson, Sven Nordebo, Daniel Sjöberg, Richard BayfordAbstract:A new simplified formula is derived for the absorption cross section of small dielectric ellipsoidal particles embedded in Lossy Media. The new expression leads directly to a closed form solution f ...
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absorption and optimal plasmonic resonances for small ellipsoidal particles in Lossy Media
arXiv: Classical Physics, 2017Co-Authors: Mariana Dalarsson, Sven Nordebo, Daniel Sjöberg, Richard BayfordAbstract:A new simplified formula is derived for the absorption cross section of small dielectric ellipsoidal particles embedded in Lossy Media. The new expression leads directly to a closed form solution for the optimal conjugate match with respect to the surrounding medium, i.e., the optimal permittivity of the ellipsoidal particle that maximizes the absorption at any given frequency. This defines the optimal plasmonic resonance for the ellipsoid. The optimal conjugate match represents a metamaterial in the sense that the corresponding optimal permittivity function may have negative real part (inductive properties), and can not in general be implemented as a passive material over a given bandwidth. A necessary and sufficient condition is derived for the feasibility of tuning the Drude model to the optimal conjugate match at a single frequency, and it is found that all the prolate spheroids and some of the (not too flat) oblate spheroids can be tuned into optimal plasmonic resonance at any desired center frequency. Numerical examples are given to illustrate the analysis. Except for the general understanding of plasmonic resonances in Lossy Media, it is also anticipated that the new results can be useful for feasibility studies with e.g., the radiotherapeutic hyperthermia based methods to treat cancer based on electrophoretic heating in gold nanoparticle suspensions using microwave radiation.
Fabrizio Frezza - One of the best experts on this subject based on the ideXlab platform.
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An Analytical Study of Electromagnetic Deep Penetration Conditions and Implications in Lossy Media through Inhomogeneous Waves.
Materials (Basel Switzerland), 2018Co-Authors: Paolo Baccarelli, Fabrizio Frezza, Patrizio Simeoni, Nicola TedeschiAbstract:This paper illustrates how the penetration of electromagnetic waves in Lossy Media strongly depends on the waveform and not only on the Media involved. In particular, the so-called inhomogeneous plane waves are compared against homogeneous plane waves illustrating how the first ones can generate deep penetration effects. Moreover, the paper provides examples showing how such waves may be practically generated. The approach taken here is analytical and it concentrates on the deep penetration conditions obtained by means of incident inhomogeneous plane waves incoming from a lossless medium and impinging on a Lossy medium. Both conditions and constraints that the waveforms need to possess to achieve deep penetration are analysed. Some results are finally validated through numerical computations. The theory presented here is of interest in view of a practical implementation of the deep penetration effect.
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Inhomogeneous wave penetration in Lossy Media
2016 URSI International Symposium on Electromagnetic Theory (EMTS), 2016Co-Authors: Paolo Baccarelli, Fabrizio Frezza, Patrizio Simeoni, Nicola TedeschiAbstract:The penetration properties of inhomogeneous waves are illustrated. A theoretical approach is presented and a leaky-wave antenna design is proposed in order to verify the theoretical implications. Practical aspects related to the excitation of leaky waves able to give rise to deep penetration effects in Lossy Media are discussed and the possible implementation issues are commented.
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On the electromagnetic power transmission between two Lossy Media: discussion.
Journal of the Optical Society of America. A Optics image science and vision, 2012Co-Authors: Fabrizio Frezza, Nicola TedeschiAbstract:An overview of the problems involved in the study of electromagnetic power transmission between Lossy Media is presented. Starting from the well-known problem of the transmission at a dielectric–conductor interface, the different representations of the complex propagation vector of the plane waves are introduced. Analytical expressions to convert from one formulation to the other are obtained. Moreover, the transmission of a plane wave at the interface between two Lossy Media is taken into account. An explanation of the strange behavior of the transmitted wave is developed by means of power considerations. Finally, the interesting effect of the parallel-attenuated transmitted wave is presented, and its properties as a function of the incident phase vector amplitude are deduced.
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Deeply penetrating waves in Lossy Media.
Optics Letters, 2012Co-Authors: Fabrizio Frezza, Nicola TedeschiAbstract:The incidence of an inhomogeneous plane wave on the interface between two Lossy Media is analyzed. The analytical expressions of the incidence angle of the phase vector, for which the transmitted wave has the phase or the attenuation vector parallel to the interface, are obtained. The transmitted wave with the attenuation vector parallel to the interface is physically interpreted, finding a wave in a Lossy medium without attenuation away from the interface. The same effect appears at the interface between a lossless medium and a Lossy one.
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Generalized plane-wave expansion of cylindrical functions in Lossy Media convergent in the whole complex plane
Optics Communications, 2011Co-Authors: Fabrizio Frezza, Giuseppe Schettini, Nicola TedeschiAbstract:Abstract Electromagnetic scattering by buried objects may involve a plane-wave expansion of the related fields, which depends on the objects' geometry. Furthermore, involved Media in realistic cases are Lossy, which requires the analytic continuation of formulae known for the lossless cases, due to the complex nature of the wave vectors. This problem has been covered in a previous paper, but the expression found still does not converge in some areas of space. In this paper, a new, convergent, expression of the spectrum of cylindrical functions in Lossy Media is analytically computed and its convergence limits are discussed.
