Konstantinos Prokopidis | Aristotle University of Thessaloniki (original) (raw)

Papers by Konstantinos Prokopidis

Research paper thumbnail of Authors' Reply to “On the Equivalence of the Stability of the D-E and J-E ADE-FDTD Schemes for Implementing the Modified Lorentz Dispersive Model&#x201D

IEEE Microwave and Wireless Components Letters, 2015

Research paper thumbnail of A higher-order spatial FDTD scheme with CFS PML for 3D numerical simulation of wave propagation in cold plasma

A novel 3-D higher-order finite-difference time-domain framework with complex frequency-shifted p... more A novel 3-D higher-order finite-difference time-domain framework with complex frequency-shifted perfectly matched layer for the modeling of wave propagation in cold plasma is presented. Secondand fourth-order spatial approximations are used to discretize Maxwell's curl equations and a uniaxial perfectly matched layer with the complex frequency-shifted equations is introduced to terminate the computational domain. A numerical dispersion study of second-and higher-order techniques is elaborated and their stability criteria are extracted for each scheme. Comparisons with analytical solutions verify the accuracy of the proposed methods and the low dispersion error of the higher-order schemes.

Research paper thumbnail of On the development of efficient FDTD-PML formulations for general dispersive media

International Journal of Numerical Modelling: Electronic Networks, Devices and Fields, 2008

A novel implementation of the perfectly matched layer (PML) absorbing boundary condition (ABC) to... more A novel implementation of the perfectly matched layer (PML) absorbing boundary condition (ABC) to terminate the finite-difference time-domain (FDTD) algorithm for general dispersive and negative index materials is presented. The proposed formulation also adopts the complex frequency-shifted (CFS) approach, involves simple FDTD expressions and avoids complex arithmetic. Several FDTD-PML simulations with different parameters are conducted for the termination of various dispersive media validating the stability, accuracy and effectiveness of the schemes and indicating the advantage of the CFS-PML.

Research paper thumbnail of A nonorthogonally-oriented higher-order FDTD technique for 3-D waveguide and antenna structures on curvilinear grids

2000 5th International Symposium on Antennas, Propagation, and EM Theory. ISAPE 2000 (IEEE Cat. No.00EX417), 2000

A generalized higher-order FDTD technique for the accurate modeling of complex waveguide and ante... more A generalized higher-order FDTD technique for the accurate modeling of complex waveguide and antenna configurations in 3-D nonorthogonal curvilinear coordinates, is presented in this paper. The novel methodology which introduces conventional and nonstandard differencing concepts, embodies an efficient treatment of the div-curl problem on an unstructured lattice and develops enhanced Perfectly Matched Layer absorbers for the truncation of unbounded domains. Moreover, a progressively mesh expanding algorithm leads to a serious decrease of the overall mesh. In the temporal variable, the four-stage Runge-Kutta integrator is also invoked, whereas the wider spatial increments are effectively limited by a new class of self-adaptive compact operators. Numerical verification illustrates that the proposed technique offers a significant mitigation of dispersion errors, yields precise values for the S-parameters and performs promising radiation pattern computations for various kinds of contemporary antennas.

Research paper thumbnail of Time-domain modeling of dispersive and lossy liquid-crystals for terahertz applications

Optical Materials Express, 2014

A numerical framework based on the finite-difference timedomain method is proposed for the rigoro... more A numerical framework based on the finite-difference timedomain method is proposed for the rigorous study of electro-optically tunable terahertz devices based on liquid crystals. The formulation accounts for both the liquid-crystal full-tensor anisotropy and the dispersion of its complex refractive indices, which is described via modified Lorentzian terms. Experimentally characterized liquid-crystalline materials in the terahertz spectrum are fitted and modeled in benchmark examples, directly compared with reference analytical or semi-analytical solutions. In addition, the efficiency of broadband time-domain modeling of the proposed technique is also demonstrated by accurately reproducing time-domain spectroscopy measurements.

Research paper thumbnail of Transparent Nanoprobes in Integrated Plasmonic Circuits Based on Plasmonic Cloaking

Physical Review Applied, 2014

ABSTRACT Cloaking of nanoscopic objects via the scattering-cancellation technique is theoreticall... more ABSTRACT Cloaking of nanoscopic objects via the scattering-cancellation technique is theoretically demonstrated in integrated plasmonic circuits with deep subwavelength confinement in the infrared. By proper design of the cloaking shell, transparency of the cloaked objects can be achieved, even when these objects occupy the whole cross section of a metal-insulator-metal waveguide. The effects of material losses, possible implementations, and potential applications are discussed.

Research paper thumbnail of Modeling of Dielectric Properties of Biological Tissues by Vector Fitting

A novel application of the vector fitting (VF) technique is developed to calculate the Debye mode... more A novel application of the vector fitting (VF) technique is developed to calculate the Debye model parameters of biological tissues directly from measurement data. The proposed formulation is applied for several tissues and the relative error of the fitting is estimated in comparison with other fitting techniques. The present method is proved to be simple, accurate and instructive for biomedical and biotechnological applications involving nanopulses.

Research paper thumbnail of Modeling of ground-penetrating radar for detecting buried objects in dispersive soils

2005 IEEE/ACES International Conference on Wireless Communications and Applied Computational Electromagnetics, 2005

ABSTRACT A three-dimensional (3-D) time-domain numerical method is used for simulation of ground ... more ABSTRACT A three-dimensional (3-D) time-domain numerical method is used for simulation of ground penetrating radar (GPR) on Debye-dispersive soil. The radar unit is modeled with two transmitters and one receiver in order to eliminate undesired signals. The impact of radar frequency, soil parameters and object depth upon the ability to detect buried targets is investigated through several FDTD simulations.

Research paper thumbnail of An ADI-FDTD Formulation With Modified Lorentz Dispersion for the Study of Plasmonic Structures

Photonics Technology Letters, IEEE, 2014

ABSTRACT This letter presents an alternating-direction implicit finite-difference time-domain sch... more ABSTRACT This letter presents an alternating-direction implicit finite-difference time-domain scheme for the efficient study of plasmonic systems. The material dispersion is described by generalized modified Lorentzian terms and it is implemented via the auxiliary differential equations technique employing an order reduction. The computational domain is backed by a properly designed convolution perfectly matched layer. The efficiency of the proposed method is validated in benchmark examples and its unconditional stability is evidenced by the Fourier method.

Research paper thumbnail of Rigorous broadband investigation of liquid-crystal plasmonic structures using finite-difference time-domain dispersive-anisotropic models

Journal of the Optical Society of America B, 2013

A finite-difference time-domain scheme is proposed for the rigorous study of liquid-crystal photo... more A finite-difference time-domain scheme is proposed for the rigorous study of liquid-crystal photonic and plasmonic structures. The model takes into account the full-tensor liquid-crystal anisotropy as well as the permittivity dispersion of all materials involved. Isotropic materials are modeled via a generalized critical points model, while the dispersion of the liquid-crystal indices is described by Lorentzian terms. The validity of the proposed scheme is verified via a series of examples, ranging from transmission through liquid-crystal waveplates and cholesteric slabs to the plasmonic response of arrays of gold nanostripes with a liquid-crystal overlayer and the dispersive properties of metal-liquid-crystal-metal plasmonic waveguides. Results are directly compared with reference analytical or frequency-domain numerical solutions.

Research paper thumbnail of A Unified FDTD/PML Scheme Based on Critical Points for Accurate Studies of Plasmonic Structures

Journal of Lightwave Technology, 2000

ABSTRACT A generalized auxiliary differential equation (ADE) finite-difference time-domain (FDTD)... more ABSTRACT A generalized auxiliary differential equation (ADE) finite-difference time-domain (FDTD) dispersive scheme is introduced for the rigorous simulation of wave propagation in metallic structures at optical frequencies, where material dispersion is described via an arbitrary number of Drude and critical point terms. The implementation of an efficient perfectly matched layer for the termination of such media is also discussed and demonstrated. The model’s validity is directly compared with both analytical and numerical results that employ known dispersion schemes, for the case of two benchmark examples, transmission through a thin metal film and scattering from a metallic nanocylinder. Furthermore, the accuracy of the proposed method is also demonstrated in the study of the optical properties of Ag and Au metal-insulator-metal waveguides, filters, and resonators, which also involve dielectrics whose material dispersion is described by the Sellmeier model.

Research paper thumbnail of An FDTD Algorithm for Wave Propagation in Dispersive Media using Higher-Order Schemes

Journal of Electromagnetic Waves and Applications, 2004

A fourth-order accurate in space and second-order accurate in time, Finite-Difference Time-Domain... more A fourth-order accurate in space and second-order accurate in time, Finite-Difference Time-Domain (FDTD) scheme for wave propagation in lossy dispersive media is presented. The formulation of Maxwell's equations is fully described and an elaborate study of the stability and dispersion properties of the resulting algorithm is conducted. The efficiency of the proposed FDTD(2,4) technique compared to its conventional FDTD(2,2) counterpart is demonstrated through numerical results.

Research paper thumbnail of Numerical modeling of an indoor wireless environment for the performance evaluation of WLAN systems

IEEE Transactions on Magnetics, 2000

A site-specific numerical model, based on the finite-difference time-domain method, is developed ... more A site-specific numerical model, based on the finite-difference time-domain method, is developed in this paper for the indoor radio channel. The scenario of interest is concerned with wave propagation in a typical office environment, for which several simulations are performed considering different placements of the transmitting antenna. Both the 2-and 5-GHz bands are examined, where contemporary wireless local area networks operate. Important channel characteristics are evaluated via the estimation of received power levels, as well as the examination of small-scale fading and time dispersion. Index Terms-Finite-difference time-domain (FDTD) method, indoor propagation, wireless communications.

Research paper thumbnail of The effect of substrate dispersion on the operation of square microstrip antennas

IEEE Transactions on Magnetics, 2000

The effect of dispersive substrates upon the operation of microstrip antennas is evaluated with a... more The effect of dispersive substrates upon the operation of microstrip antennas is evaluated with a simple and efficient finite-difference time-domain technique. Two single-feed corner-truncated patches with Debye-modeled substrates are simulated; the reflection coefficient and the input impedance are calculated and compared with the lossless case demonstrating that mainly the input impedance and slightly the resonant frequencies are influenced. An unsplit perfectly matched layer is also proposed for the termination of computational domains with dispersive media.

Research paper thumbnail of Performance optimization of the PML absorber in lossy media via closed-form expressions of the reflection coefficient

IEEE Transactions on Magnetics, 2003

Research paper thumbnail of Investigation of the Stability of ADE-FDTD Methods for Modified Lorentz Media

IEEE Microwave and Wireless Components Letters, 2000

This letter addresses the stability problem of two auxiliary differential equation (ADE) finite-d... more This letter addresses the stability problem of two auxiliary differential equation (ADE) finite-difference time-domain (FDTD) methods for the case of modified Lorentz media, using the combination of the von Neumann method and the Routh-Hurwitz criterion. A rigorous investigation supported by FDTD simulations designates that the stability criterion of the conventional FDTD method can be preserved via the proper selection of the difference and averaging operators. A set of conditions for the dispersive medium parameters is derived, providing the stability limit for both FDTD schemes with practical guidelines for evaluating the fitting of experimentally studied materials.

Research paper thumbnail of Higher-order FDTD(2,4) scheme for accurate simulations in lossy dielectrics

Electronics Letters, 2003

Research paper thumbnail of Efficient FDTD algorithms for dispersive Drude-critical points media based on bilinear z-transform

Electronics Letters, 2013

ABSTRACT Finite-difference time-domain (FDTD) schemes based on the bilinear z-transform are intro... more ABSTRACT Finite-difference time-domain (FDTD) schemes based on the bilinear z-transform are introduced for modelling time-domain wave propagation in dispersive Drude-critical points media. The accuracy and efficiency of the proposed technique are verified by comparisons with other FDTD algorithms and analytical solutions.

Research paper thumbnail of FDTD Algorithm for Microstrip Antennas with Lossy Substrates Using Higher Order Schemes

Electromagnetics, 2004

needed to accomplish equivalent levels of accuracy with the classical FDTD algorithm. Higher orde... more needed to accomplish equivalent levels of accuracy with the classical FDTD algorithm. Higher order FDTD schemes exhibit lower dispersion errors and enable the efficient simulation of electrically large practical problems. Fang (1989) first introduced fourthorder spatial and second-(and fourth-) order temporal accuracy algorithms. In Young, , an efficient compact scheme was merged with a Runge-Kutta integrator and in Hadi and Piket-May (1997) a modified version was introduced for modeling electrically large structures. In Georgakopoulos et al. , higher order schemes were combined with subgridding techniques to handle any fine features of the structure, while Prokopidis and Tsiboukis presented an extension of the FDTD (2,4) technique to lossy dielectrics and its application to a two-dimensional waveguide problem.

Research paper thumbnail of A higher-order unsplit-field perfectly matched layer for the reflectionless truncation of 3-D spherical FDTD lattices

Electrical Engineering, 2002

An enhanced higher-order finite-difference timedomain (FDTD) method for the systematic implementa... more An enhanced higher-order finite-difference timedomain (FDTD) method for the systematic implementation of 3-D reflectionless perfectly matched layers (PML) in spherical coordinates is presented. By establishing a topologically unsplit-field formulation, the novel technique introduces accurate nonstandard schemes that eliminate the notably intricate lattice dispersion errors. Moreover, the wider spatial increments are treated via self-adaptive compact operators, while a mesh expansion process yields a significant reduction of the absorber's depth. For the temporal variable, the proposed method employs a multistage leapfrog integration that guarantees stability and excitation universality. Hence, because of the optimal configuration of the new PML, it attains a critical annihilation of both propagating and spurious wave families, even for complicated domains. Numerical investigation verifies the superiority of the higher-order algorithm via several unbounded radiation and scattering spherical problems.

Research paper thumbnail of Authors' Reply to “On the Equivalence of the Stability of the D-E and J-E ADE-FDTD Schemes for Implementing the Modified Lorentz Dispersive Model&#x201D

IEEE Microwave and Wireless Components Letters, 2015

Research paper thumbnail of A higher-order spatial FDTD scheme with CFS PML for 3D numerical simulation of wave propagation in cold plasma

A novel 3-D higher-order finite-difference time-domain framework with complex frequency-shifted p... more A novel 3-D higher-order finite-difference time-domain framework with complex frequency-shifted perfectly matched layer for the modeling of wave propagation in cold plasma is presented. Secondand fourth-order spatial approximations are used to discretize Maxwell's curl equations and a uniaxial perfectly matched layer with the complex frequency-shifted equations is introduced to terminate the computational domain. A numerical dispersion study of second-and higher-order techniques is elaborated and their stability criteria are extracted for each scheme. Comparisons with analytical solutions verify the accuracy of the proposed methods and the low dispersion error of the higher-order schemes.

Research paper thumbnail of On the development of efficient FDTD-PML formulations for general dispersive media

International Journal of Numerical Modelling: Electronic Networks, Devices and Fields, 2008

A novel implementation of the perfectly matched layer (PML) absorbing boundary condition (ABC) to... more A novel implementation of the perfectly matched layer (PML) absorbing boundary condition (ABC) to terminate the finite-difference time-domain (FDTD) algorithm for general dispersive and negative index materials is presented. The proposed formulation also adopts the complex frequency-shifted (CFS) approach, involves simple FDTD expressions and avoids complex arithmetic. Several FDTD-PML simulations with different parameters are conducted for the termination of various dispersive media validating the stability, accuracy and effectiveness of the schemes and indicating the advantage of the CFS-PML.

Research paper thumbnail of A nonorthogonally-oriented higher-order FDTD technique for 3-D waveguide and antenna structures on curvilinear grids

2000 5th International Symposium on Antennas, Propagation, and EM Theory. ISAPE 2000 (IEEE Cat. No.00EX417), 2000

A generalized higher-order FDTD technique for the accurate modeling of complex waveguide and ante... more A generalized higher-order FDTD technique for the accurate modeling of complex waveguide and antenna configurations in 3-D nonorthogonal curvilinear coordinates, is presented in this paper. The novel methodology which introduces conventional and nonstandard differencing concepts, embodies an efficient treatment of the div-curl problem on an unstructured lattice and develops enhanced Perfectly Matched Layer absorbers for the truncation of unbounded domains. Moreover, a progressively mesh expanding algorithm leads to a serious decrease of the overall mesh. In the temporal variable, the four-stage Runge-Kutta integrator is also invoked, whereas the wider spatial increments are effectively limited by a new class of self-adaptive compact operators. Numerical verification illustrates that the proposed technique offers a significant mitigation of dispersion errors, yields precise values for the S-parameters and performs promising radiation pattern computations for various kinds of contemporary antennas.

Research paper thumbnail of Time-domain modeling of dispersive and lossy liquid-crystals for terahertz applications

Optical Materials Express, 2014

A numerical framework based on the finite-difference timedomain method is proposed for the rigoro... more A numerical framework based on the finite-difference timedomain method is proposed for the rigorous study of electro-optically tunable terahertz devices based on liquid crystals. The formulation accounts for both the liquid-crystal full-tensor anisotropy and the dispersion of its complex refractive indices, which is described via modified Lorentzian terms. Experimentally characterized liquid-crystalline materials in the terahertz spectrum are fitted and modeled in benchmark examples, directly compared with reference analytical or semi-analytical solutions. In addition, the efficiency of broadband time-domain modeling of the proposed technique is also demonstrated by accurately reproducing time-domain spectroscopy measurements.

Research paper thumbnail of Transparent Nanoprobes in Integrated Plasmonic Circuits Based on Plasmonic Cloaking

Physical Review Applied, 2014

ABSTRACT Cloaking of nanoscopic objects via the scattering-cancellation technique is theoreticall... more ABSTRACT Cloaking of nanoscopic objects via the scattering-cancellation technique is theoretically demonstrated in integrated plasmonic circuits with deep subwavelength confinement in the infrared. By proper design of the cloaking shell, transparency of the cloaked objects can be achieved, even when these objects occupy the whole cross section of a metal-insulator-metal waveguide. The effects of material losses, possible implementations, and potential applications are discussed.

Research paper thumbnail of Modeling of Dielectric Properties of Biological Tissues by Vector Fitting

A novel application of the vector fitting (VF) technique is developed to calculate the Debye mode... more A novel application of the vector fitting (VF) technique is developed to calculate the Debye model parameters of biological tissues directly from measurement data. The proposed formulation is applied for several tissues and the relative error of the fitting is estimated in comparison with other fitting techniques. The present method is proved to be simple, accurate and instructive for biomedical and biotechnological applications involving nanopulses.

Research paper thumbnail of Modeling of ground-penetrating radar for detecting buried objects in dispersive soils

2005 IEEE/ACES International Conference on Wireless Communications and Applied Computational Electromagnetics, 2005

ABSTRACT A three-dimensional (3-D) time-domain numerical method is used for simulation of ground ... more ABSTRACT A three-dimensional (3-D) time-domain numerical method is used for simulation of ground penetrating radar (GPR) on Debye-dispersive soil. The radar unit is modeled with two transmitters and one receiver in order to eliminate undesired signals. The impact of radar frequency, soil parameters and object depth upon the ability to detect buried targets is investigated through several FDTD simulations.

Research paper thumbnail of An ADI-FDTD Formulation With Modified Lorentz Dispersion for the Study of Plasmonic Structures

Photonics Technology Letters, IEEE, 2014

ABSTRACT This letter presents an alternating-direction implicit finite-difference time-domain sch... more ABSTRACT This letter presents an alternating-direction implicit finite-difference time-domain scheme for the efficient study of plasmonic systems. The material dispersion is described by generalized modified Lorentzian terms and it is implemented via the auxiliary differential equations technique employing an order reduction. The computational domain is backed by a properly designed convolution perfectly matched layer. The efficiency of the proposed method is validated in benchmark examples and its unconditional stability is evidenced by the Fourier method.

Research paper thumbnail of Rigorous broadband investigation of liquid-crystal plasmonic structures using finite-difference time-domain dispersive-anisotropic models

Journal of the Optical Society of America B, 2013

A finite-difference time-domain scheme is proposed for the rigorous study of liquid-crystal photo... more A finite-difference time-domain scheme is proposed for the rigorous study of liquid-crystal photonic and plasmonic structures. The model takes into account the full-tensor liquid-crystal anisotropy as well as the permittivity dispersion of all materials involved. Isotropic materials are modeled via a generalized critical points model, while the dispersion of the liquid-crystal indices is described by Lorentzian terms. The validity of the proposed scheme is verified via a series of examples, ranging from transmission through liquid-crystal waveplates and cholesteric slabs to the plasmonic response of arrays of gold nanostripes with a liquid-crystal overlayer and the dispersive properties of metal-liquid-crystal-metal plasmonic waveguides. Results are directly compared with reference analytical or frequency-domain numerical solutions.

Research paper thumbnail of A Unified FDTD/PML Scheme Based on Critical Points for Accurate Studies of Plasmonic Structures

Journal of Lightwave Technology, 2000

ABSTRACT A generalized auxiliary differential equation (ADE) finite-difference time-domain (FDTD)... more ABSTRACT A generalized auxiliary differential equation (ADE) finite-difference time-domain (FDTD) dispersive scheme is introduced for the rigorous simulation of wave propagation in metallic structures at optical frequencies, where material dispersion is described via an arbitrary number of Drude and critical point terms. The implementation of an efficient perfectly matched layer for the termination of such media is also discussed and demonstrated. The model’s validity is directly compared with both analytical and numerical results that employ known dispersion schemes, for the case of two benchmark examples, transmission through a thin metal film and scattering from a metallic nanocylinder. Furthermore, the accuracy of the proposed method is also demonstrated in the study of the optical properties of Ag and Au metal-insulator-metal waveguides, filters, and resonators, which also involve dielectrics whose material dispersion is described by the Sellmeier model.

Research paper thumbnail of An FDTD Algorithm for Wave Propagation in Dispersive Media using Higher-Order Schemes

Journal of Electromagnetic Waves and Applications, 2004

A fourth-order accurate in space and second-order accurate in time, Finite-Difference Time-Domain... more A fourth-order accurate in space and second-order accurate in time, Finite-Difference Time-Domain (FDTD) scheme for wave propagation in lossy dispersive media is presented. The formulation of Maxwell's equations is fully described and an elaborate study of the stability and dispersion properties of the resulting algorithm is conducted. The efficiency of the proposed FDTD(2,4) technique compared to its conventional FDTD(2,2) counterpart is demonstrated through numerical results.

Research paper thumbnail of Numerical modeling of an indoor wireless environment for the performance evaluation of WLAN systems

IEEE Transactions on Magnetics, 2000

A site-specific numerical model, based on the finite-difference time-domain method, is developed ... more A site-specific numerical model, based on the finite-difference time-domain method, is developed in this paper for the indoor radio channel. The scenario of interest is concerned with wave propagation in a typical office environment, for which several simulations are performed considering different placements of the transmitting antenna. Both the 2-and 5-GHz bands are examined, where contemporary wireless local area networks operate. Important channel characteristics are evaluated via the estimation of received power levels, as well as the examination of small-scale fading and time dispersion. Index Terms-Finite-difference time-domain (FDTD) method, indoor propagation, wireless communications.

Research paper thumbnail of The effect of substrate dispersion on the operation of square microstrip antennas

IEEE Transactions on Magnetics, 2000

The effect of dispersive substrates upon the operation of microstrip antennas is evaluated with a... more The effect of dispersive substrates upon the operation of microstrip antennas is evaluated with a simple and efficient finite-difference time-domain technique. Two single-feed corner-truncated patches with Debye-modeled substrates are simulated; the reflection coefficient and the input impedance are calculated and compared with the lossless case demonstrating that mainly the input impedance and slightly the resonant frequencies are influenced. An unsplit perfectly matched layer is also proposed for the termination of computational domains with dispersive media.

Research paper thumbnail of Performance optimization of the PML absorber in lossy media via closed-form expressions of the reflection coefficient

IEEE Transactions on Magnetics, 2003

Research paper thumbnail of Investigation of the Stability of ADE-FDTD Methods for Modified Lorentz Media

IEEE Microwave and Wireless Components Letters, 2000

This letter addresses the stability problem of two auxiliary differential equation (ADE) finite-d... more This letter addresses the stability problem of two auxiliary differential equation (ADE) finite-difference time-domain (FDTD) methods for the case of modified Lorentz media, using the combination of the von Neumann method and the Routh-Hurwitz criterion. A rigorous investigation supported by FDTD simulations designates that the stability criterion of the conventional FDTD method can be preserved via the proper selection of the difference and averaging operators. A set of conditions for the dispersive medium parameters is derived, providing the stability limit for both FDTD schemes with practical guidelines for evaluating the fitting of experimentally studied materials.

Research paper thumbnail of Higher-order FDTD(2,4) scheme for accurate simulations in lossy dielectrics

Electronics Letters, 2003

Research paper thumbnail of Efficient FDTD algorithms for dispersive Drude-critical points media based on bilinear z-transform

Electronics Letters, 2013

ABSTRACT Finite-difference time-domain (FDTD) schemes based on the bilinear z-transform are intro... more ABSTRACT Finite-difference time-domain (FDTD) schemes based on the bilinear z-transform are introduced for modelling time-domain wave propagation in dispersive Drude-critical points media. The accuracy and efficiency of the proposed technique are verified by comparisons with other FDTD algorithms and analytical solutions.

Research paper thumbnail of FDTD Algorithm for Microstrip Antennas with Lossy Substrates Using Higher Order Schemes

Electromagnetics, 2004

needed to accomplish equivalent levels of accuracy with the classical FDTD algorithm. Higher orde... more needed to accomplish equivalent levels of accuracy with the classical FDTD algorithm. Higher order FDTD schemes exhibit lower dispersion errors and enable the efficient simulation of electrically large practical problems. Fang (1989) first introduced fourthorder spatial and second-(and fourth-) order temporal accuracy algorithms. In Young, , an efficient compact scheme was merged with a Runge-Kutta integrator and in Hadi and Piket-May (1997) a modified version was introduced for modeling electrically large structures. In Georgakopoulos et al. , higher order schemes were combined with subgridding techniques to handle any fine features of the structure, while Prokopidis and Tsiboukis presented an extension of the FDTD (2,4) technique to lossy dielectrics and its application to a two-dimensional waveguide problem.

Research paper thumbnail of A higher-order unsplit-field perfectly matched layer for the reflectionless truncation of 3-D spherical FDTD lattices

Electrical Engineering, 2002

An enhanced higher-order finite-difference timedomain (FDTD) method for the systematic implementa... more An enhanced higher-order finite-difference timedomain (FDTD) method for the systematic implementation of 3-D reflectionless perfectly matched layers (PML) in spherical coordinates is presented. By establishing a topologically unsplit-field formulation, the novel technique introduces accurate nonstandard schemes that eliminate the notably intricate lattice dispersion errors. Moreover, the wider spatial increments are treated via self-adaptive compact operators, while a mesh expansion process yields a significant reduction of the absorber's depth. For the temporal variable, the proposed method employs a multistage leapfrog integration that guarantees stability and excitation universality. Hence, because of the optimal configuration of the new PML, it attains a critical annihilation of both propagating and spurious wave families, even for complicated domains. Numerical investigation verifies the superiority of the higher-order algorithm via several unbounded radiation and scattering spherical problems.