This paper addresses guided wave propagation in threedimensional open omega waveguides. The analy... more This paper addresses guided wave propagation in threedimensional open omega waveguides. The analysis uses a mode matching technique, is focused on the discrete modes and includes both guidance and leakage behavior. It is shown that, in some ranges of operation, the discrete surface modes turn into leaky modes due to TE-TM mode coupling, an effect already known for isotropic dielectric waveguides. The numerical results show the influence of the medium and geometrical parameters on the attenuation and phase constants of these leaky modes.
The 2-D finite-difference frequency-domain method (FDFD) combined with the surface impedance boun... more The 2-D finite-difference frequency-domain method (FDFD) combined with the surface impedance boundary condition (SIBC) was employed to analyze the propagation characteristics of hollow rectangular waveguides at Terahertz (THz) frequencies. The electromagnetic field components, in the interior of the waveguide, were discretized using central finite-difference schemes. Considering the hollow rectangular waveguide surrounded by a medium of finite conductivity, the electric and magnetic tangential field components on the metal surface were related by the SIBC. The surface impedance was calculated by the Drude dispersion model at THz frequencies, which was used to characterize the conductivity of the metal. By solving the Eigen equations, the propagation constants, including the attenuation constant and the phase constant, were obtained for a given frequency. The proposed method shows good applicability for full-wave analysis of THz waveguides with complex boundaries.
The pseudochiral or omega medium is an artificial complex medium obtained by doping a host medium... more The pseudochiral or omega medium is an artificial complex medium obtained by doping a host medium with omega shaped conducting microstructures. We investigate the occurrence of complex modes on planar waveguides containing pseudochiral media. In a dielectric asymmetric pseudochiral waveguide in which both the film and the substrate are pseudochiral media but with an isotropic superstrate, it is shown that, when the pseudochiral parameter exceeds a certain transition value, power leakage occurs. These modes are termed semileaky modes since one of the two characteristic waves is not internally reflected at the film-substrate interface. Numerical results are presented for the phase and leakage constants of the semileaky modes.
We present a new variational approach to analyze dispersion-managed solitons in wavelength-divisi... more We present a new variational approach to analyze dispersion-managed solitons in wavelength-division- -multiplexed communication systems. Based on this approach, the periodic dispersion maps that minimize residual frequency shifts in a two-channel system can be easily determined. Comparison with results from the split- -step Fourier method ensures the accuracy of our formulation
This paper addresses the use of metamaterials in the design of an NRD contra-directional coupler.... more This paper addresses the use of metamaterials in the design of an NRD contra-directional coupler. The coupling between two parallel NRD waveguides, with the same phase constant but with antiparallel power flow provides new features that can be used in the design of novel devices for signal processing. We analyse the contra-directional interaction in a NRD waveguide coupler, in which, a metamaterial slab replaces one of the common isotropic slabs. The propagation of a backward wave in phase synchronism will cause a strong contra-directional interaction with significant interchange of energy. INTRODUCTION The analysis of unconventional media with both negative electric permittivity and negative magnetic permeability has recently received increased attention [1]-[3]. In such media, usually termed metamaterials, left-handed media or backward media, the direction of the Poynting vector is anti-parallel to the direction of the phase velocity [4]. However, most interesting effects associat...
Recent experimental verification of metamaterials with negative index of refraction – also known ... more Recent experimental verification of metamaterials with negative index of refraction – also known as DNG (double negative) media as their permittivity and permeability are both negative – has led to the widespread research of guiding structures that are made of (or include) these new metamaterials. The unusual properties exhibited by DNG materials, such as backward wave propagation and antiparallel phase and group velocities, makes them suitable for new microwave devices. One such device is the DNG open waveguide studied by Shadrivov et al. (I. V. Shadrivov, A. A. Sukhorukov, and Y. S. Kivshar, Phys. Rev. E, 67, 057602, 2003) where the propagation properties of guided modes were analyzed. We present a variation of this waveguide and study not only guided modes but also leaky modes. The study of leaky modes in open dielectric waveguides was analyzed by Tamir and Oliner back in 1963 (T. Tamir, A. Oliner, Proc. IEE, 110, 310-334, 1963). In this paper a symmetrical DPS-DNG structure, as shown in the inset of Figure 1, is analyzed. The modal equation is obtained for TE and TM modes. However, surface as well as leaky modes were investigated when numerically solving the modal equation. Figure 1 shows the dispersion curve of the fundamental TE mode, where v is a normalized frequency. In the presentation, the dispersion diagrams for both surface and leaky modes will be discussed. The appearance of stop-bands in guided modes and the occurrence of leaky modes (for 1 eff n > ) are addressed – two effects that do not exist in conventional or DPS (double positive) waveguides. Finally, a comparison between this structure and a conventional DPS-DPS waveguide is given in order to highlight the new specific characteristics that are induced by the DNG material
This paper treats electromagnetic wave propagation in anisotropic, chiral and pseudochiral 3D str... more This paper treats electromagnetic wave propagation in anisotropic, chiral and pseudochiral 3D structures. The analysis is focused on radiation and leakage behavior and includes a discussion of the effect of the media parameters on the electromagnetic characteristics of these structures. I.
The interaction between users and devices tends to be increasingly flexible. The need for harmoni... more The interaction between users and devices tends to be increasingly flexible. The need for harmonization of IT platforms with the user has strongly increased. With a single gesture we can control the TV sound, turn off the lights or even call the emergency number. This feature revolutionizes applications in various fields, including areas such as home automation, health of the elderly and children, games, etc. Actually, most of the deployed solutions based on sensors and computer vision. However, the price of this vision sensor-based technology and the difficulty of installation turns out to be complicated its development on a large scale. This dissertation addresses gesture recognition through the reflection of electromagnetic waves. The aim is to develop a sustainable and realistic technology for gesture recognition based on the reflection of electromagnetic waves, giving solution to the challenges related to this issue, such as getting the gestures information, influence of dynamic elements in this context, fundamental utility of Doppler Effect, minimizing interference, safety issues associated and the effect of multipath approach.
A computational tool for application to educational Electromagnetics is presented. Integrating a ... more A computational tool for application to educational Electromagnetics is presented. Integrating a set of numerical modules, it allows the simulation and demo of several radio wave-propagation scenarios at the Earth surface. The application was developed using MATLAB and includes field interference due to ground reflection, ray-tracing in a stratified atmosphere, sub-refraction mirage effects, single or multiple obstacles and mobile communication urban environments. The final application includes a graphical user interface (GUI) for data input, which is structured in a building-block approach easily expandable to include other features.
This paper addresses the material dispersion effects on the propagation characteristics of an ome... more This paper addresses the material dispersion effects on the propagation characteristics of an omega nonradiative dielectric (NRD) waveguide. The omega NRD waveguide is an H-guide, working in the closed-waveguide regime, where the common isotropic slab is replaced by an omega slab. For the first time, a single-resonance lossless model is used for the material constitutive parameters of the omega NRD waveguide. The dispersion diagrams reflect the dispersive characteristics of the medium. In addition to the surface guided modes, proper leaky modes are found to propagate in the frequency range above the resonance, where some of the constitutive parameters become negative.
A complete spectral representation for the electromagnetic field of planar multilayered waveguide... more A complete spectral representation for the electromagnetic field of planar multilayered waveguides inhomogeneously filled with omega media is presented. The problem of guided electromagnetic propagation is reduced to an eigenvalue equation related to a 2 2 × matrix differential operator. Using the concept of adjoint waveguide, general bi-orthogonality relations for the hybrid modes (either from the discrete or from the continuous spectrum) are derived. For the special case of homogeneous layers the linear operator formalism is reduced to a simple 2 2 × coupling matrix eigenvalue problem. Finally, as an example of application, the surface and the radiation modes of a grounded omega slab waveguide are analyzed. Keywords—Metamaterials, linear operators, omega media, layered waveguide, orthogonality relations
A Lagrangian formulation is used to describe the dynamics of a two-channel, filtered and periodic... more A Lagrangian formulation is used to describe the dynamics of a two-channel, filtered and periodically amplified, dispersion managed soliton system. Two-step periodic dispersion maps that minimize residual time displacements due to inter-channel collisions are obtained.
This paper treats electromagnetic wave propagation in anisotropic, chiral and pseudochiral 3D str... more This paper treats electromagnetic wave propagation in anisotropic, chiral and pseudochiral 3D structures. The analysis is focused on radiation and leakage behavior and includes a discussion of the effect of the media parameters on the electromagnetic characteristics of these structures.
This article addresses the influence of the metamaterial losses and dispersion on the performance... more This article addresses the influence of the metamaterial losses and dispersion on the performance of double negative H-guides. The lossy dispersive Lorentz model is adopted for both the electric permittivity and the magnetic permeability. The dispersion properties of the longitudinal section magnetic modes and their root dynamics in the complex plane of the longitudinal wavenumber are analyzed. To emphasize that the modal characteristics must be analyzed taking losses into consideration, results for the lossless approximation are also presented. Finally, it is shown that the effect of metamaterial losses may suggest some potential applications.
Journal of Physics: Conference Series, Sep 1, 2018
Conjugate impedance matched metamaterials are shown to be effective traps for electromagnetic wav... more Conjugate impedance matched metamaterials are shown to be effective traps for electromagnetic waves. Objects made of such materials are able to receive radiation even when it is not directly incident on their surface. Here, we develop methods of physical modeling of such objects and investigate interactions of conjugate impedance matched superabsorbers with passing electromagnetic radiation. We study realizations of such metamaterials with meshes of loaded transmission lines and develop a theory of electromagnetic wave propagation and absorption in such media. Peculiar wave propagation, wave trapping and absorption effects in metamaterial black holes and wormholes are demonstrated. Possible modifications under the goal of optimizing absorption while minimizing complexity of the involved metamaterials are discussed. Conjugate-impedance matched superabsorbers may find applications as efficient harvesters of electromagnetic radiation, and as novel antennas and sensors.
Proceedings. Electrotechnical Conference Integrating Research, Industry and Education in Energy and Communication Engineering', 1989
... Microwave Theory Tech., vol. MTT-35, pp. 937-945, Nov. 1987. [3] AA Mostafa, CM Krowne ... De... more ... Microwave Theory Tech., vol. MTT-35, pp. 937-945, Nov. 1987. [3] AA Mostafa, CM Krowne ... Dec. 1987. [4] A. Knoesen, TK Gaylord and MG Moharam, "Hy-brid guided modes in uniaxial dielectric planar waveg-uides",J. Lightwave Tech., vol. LT-6, pp. 1083-1104, June 1988. ...
This paper addresses guided wave propagation in threedimensional open omega waveguides. The analy... more This paper addresses guided wave propagation in threedimensional open omega waveguides. The analysis uses a mode matching technique, is focused on the discrete modes and includes both guidance and leakage behavior. It is shown that, in some ranges of operation, the discrete surface modes turn into leaky modes due to TE-TM mode coupling, an effect already known for isotropic dielectric waveguides. The numerical results show the influence of the medium and geometrical parameters on the attenuation and phase constants of these leaky modes.
The 2-D finite-difference frequency-domain method (FDFD) combined with the surface impedance boun... more The 2-D finite-difference frequency-domain method (FDFD) combined with the surface impedance boundary condition (SIBC) was employed to analyze the propagation characteristics of hollow rectangular waveguides at Terahertz (THz) frequencies. The electromagnetic field components, in the interior of the waveguide, were discretized using central finite-difference schemes. Considering the hollow rectangular waveguide surrounded by a medium of finite conductivity, the electric and magnetic tangential field components on the metal surface were related by the SIBC. The surface impedance was calculated by the Drude dispersion model at THz frequencies, which was used to characterize the conductivity of the metal. By solving the Eigen equations, the propagation constants, including the attenuation constant and the phase constant, were obtained for a given frequency. The proposed method shows good applicability for full-wave analysis of THz waveguides with complex boundaries.
The pseudochiral or omega medium is an artificial complex medium obtained by doping a host medium... more The pseudochiral or omega medium is an artificial complex medium obtained by doping a host medium with omega shaped conducting microstructures. We investigate the occurrence of complex modes on planar waveguides containing pseudochiral media. In a dielectric asymmetric pseudochiral waveguide in which both the film and the substrate are pseudochiral media but with an isotropic superstrate, it is shown that, when the pseudochiral parameter exceeds a certain transition value, power leakage occurs. These modes are termed semileaky modes since one of the two characteristic waves is not internally reflected at the film-substrate interface. Numerical results are presented for the phase and leakage constants of the semileaky modes.
We present a new variational approach to analyze dispersion-managed solitons in wavelength-divisi... more We present a new variational approach to analyze dispersion-managed solitons in wavelength-division- -multiplexed communication systems. Based on this approach, the periodic dispersion maps that minimize residual frequency shifts in a two-channel system can be easily determined. Comparison with results from the split- -step Fourier method ensures the accuracy of our formulation
This paper addresses the use of metamaterials in the design of an NRD contra-directional coupler.... more This paper addresses the use of metamaterials in the design of an NRD contra-directional coupler. The coupling between two parallel NRD waveguides, with the same phase constant but with antiparallel power flow provides new features that can be used in the design of novel devices for signal processing. We analyse the contra-directional interaction in a NRD waveguide coupler, in which, a metamaterial slab replaces one of the common isotropic slabs. The propagation of a backward wave in phase synchronism will cause a strong contra-directional interaction with significant interchange of energy. INTRODUCTION The analysis of unconventional media with both negative electric permittivity and negative magnetic permeability has recently received increased attention [1]-[3]. In such media, usually termed metamaterials, left-handed media or backward media, the direction of the Poynting vector is anti-parallel to the direction of the phase velocity [4]. However, most interesting effects associat...
Recent experimental verification of metamaterials with negative index of refraction – also known ... more Recent experimental verification of metamaterials with negative index of refraction – also known as DNG (double negative) media as their permittivity and permeability are both negative – has led to the widespread research of guiding structures that are made of (or include) these new metamaterials. The unusual properties exhibited by DNG materials, such as backward wave propagation and antiparallel phase and group velocities, makes them suitable for new microwave devices. One such device is the DNG open waveguide studied by Shadrivov et al. (I. V. Shadrivov, A. A. Sukhorukov, and Y. S. Kivshar, Phys. Rev. E, 67, 057602, 2003) where the propagation properties of guided modes were analyzed. We present a variation of this waveguide and study not only guided modes but also leaky modes. The study of leaky modes in open dielectric waveguides was analyzed by Tamir and Oliner back in 1963 (T. Tamir, A. Oliner, Proc. IEE, 110, 310-334, 1963). In this paper a symmetrical DPS-DNG structure, as shown in the inset of Figure 1, is analyzed. The modal equation is obtained for TE and TM modes. However, surface as well as leaky modes were investigated when numerically solving the modal equation. Figure 1 shows the dispersion curve of the fundamental TE mode, where v is a normalized frequency. In the presentation, the dispersion diagrams for both surface and leaky modes will be discussed. The appearance of stop-bands in guided modes and the occurrence of leaky modes (for 1 eff n > ) are addressed – two effects that do not exist in conventional or DPS (double positive) waveguides. Finally, a comparison between this structure and a conventional DPS-DPS waveguide is given in order to highlight the new specific characteristics that are induced by the DNG material
This paper treats electromagnetic wave propagation in anisotropic, chiral and pseudochiral 3D str... more This paper treats electromagnetic wave propagation in anisotropic, chiral and pseudochiral 3D structures. The analysis is focused on radiation and leakage behavior and includes a discussion of the effect of the media parameters on the electromagnetic characteristics of these structures. I.
The interaction between users and devices tends to be increasingly flexible. The need for harmoni... more The interaction between users and devices tends to be increasingly flexible. The need for harmonization of IT platforms with the user has strongly increased. With a single gesture we can control the TV sound, turn off the lights or even call the emergency number. This feature revolutionizes applications in various fields, including areas such as home automation, health of the elderly and children, games, etc. Actually, most of the deployed solutions based on sensors and computer vision. However, the price of this vision sensor-based technology and the difficulty of installation turns out to be complicated its development on a large scale. This dissertation addresses gesture recognition through the reflection of electromagnetic waves. The aim is to develop a sustainable and realistic technology for gesture recognition based on the reflection of electromagnetic waves, giving solution to the challenges related to this issue, such as getting the gestures information, influence of dynamic elements in this context, fundamental utility of Doppler Effect, minimizing interference, safety issues associated and the effect of multipath approach.
A computational tool for application to educational Electromagnetics is presented. Integrating a ... more A computational tool for application to educational Electromagnetics is presented. Integrating a set of numerical modules, it allows the simulation and demo of several radio wave-propagation scenarios at the Earth surface. The application was developed using MATLAB and includes field interference due to ground reflection, ray-tracing in a stratified atmosphere, sub-refraction mirage effects, single or multiple obstacles and mobile communication urban environments. The final application includes a graphical user interface (GUI) for data input, which is structured in a building-block approach easily expandable to include other features.
This paper addresses the material dispersion effects on the propagation characteristics of an ome... more This paper addresses the material dispersion effects on the propagation characteristics of an omega nonradiative dielectric (NRD) waveguide. The omega NRD waveguide is an H-guide, working in the closed-waveguide regime, where the common isotropic slab is replaced by an omega slab. For the first time, a single-resonance lossless model is used for the material constitutive parameters of the omega NRD waveguide. The dispersion diagrams reflect the dispersive characteristics of the medium. In addition to the surface guided modes, proper leaky modes are found to propagate in the frequency range above the resonance, where some of the constitutive parameters become negative.
A complete spectral representation for the electromagnetic field of planar multilayered waveguide... more A complete spectral representation for the electromagnetic field of planar multilayered waveguides inhomogeneously filled with omega media is presented. The problem of guided electromagnetic propagation is reduced to an eigenvalue equation related to a 2 2 × matrix differential operator. Using the concept of adjoint waveguide, general bi-orthogonality relations for the hybrid modes (either from the discrete or from the continuous spectrum) are derived. For the special case of homogeneous layers the linear operator formalism is reduced to a simple 2 2 × coupling matrix eigenvalue problem. Finally, as an example of application, the surface and the radiation modes of a grounded omega slab waveguide are analyzed. Keywords—Metamaterials, linear operators, omega media, layered waveguide, orthogonality relations
A Lagrangian formulation is used to describe the dynamics of a two-channel, filtered and periodic... more A Lagrangian formulation is used to describe the dynamics of a two-channel, filtered and periodically amplified, dispersion managed soliton system. Two-step periodic dispersion maps that minimize residual time displacements due to inter-channel collisions are obtained.
This paper treats electromagnetic wave propagation in anisotropic, chiral and pseudochiral 3D str... more This paper treats electromagnetic wave propagation in anisotropic, chiral and pseudochiral 3D structures. The analysis is focused on radiation and leakage behavior and includes a discussion of the effect of the media parameters on the electromagnetic characteristics of these structures.
This article addresses the influence of the metamaterial losses and dispersion on the performance... more This article addresses the influence of the metamaterial losses and dispersion on the performance of double negative H-guides. The lossy dispersive Lorentz model is adopted for both the electric permittivity and the magnetic permeability. The dispersion properties of the longitudinal section magnetic modes and their root dynamics in the complex plane of the longitudinal wavenumber are analyzed. To emphasize that the modal characteristics must be analyzed taking losses into consideration, results for the lossless approximation are also presented. Finally, it is shown that the effect of metamaterial losses may suggest some potential applications.
Journal of Physics: Conference Series, Sep 1, 2018
Conjugate impedance matched metamaterials are shown to be effective traps for electromagnetic wav... more Conjugate impedance matched metamaterials are shown to be effective traps for electromagnetic waves. Objects made of such materials are able to receive radiation even when it is not directly incident on their surface. Here, we develop methods of physical modeling of such objects and investigate interactions of conjugate impedance matched superabsorbers with passing electromagnetic radiation. We study realizations of such metamaterials with meshes of loaded transmission lines and develop a theory of electromagnetic wave propagation and absorption in such media. Peculiar wave propagation, wave trapping and absorption effects in metamaterial black holes and wormholes are demonstrated. Possible modifications under the goal of optimizing absorption while minimizing complexity of the involved metamaterials are discussed. Conjugate-impedance matched superabsorbers may find applications as efficient harvesters of electromagnetic radiation, and as novel antennas and sensors.
Proceedings. Electrotechnical Conference Integrating Research, Industry and Education in Energy and Communication Engineering', 1989
... Microwave Theory Tech., vol. MTT-35, pp. 937-945, Nov. 1987. [3] AA Mostafa, CM Krowne ... De... more ... Microwave Theory Tech., vol. MTT-35, pp. 937-945, Nov. 1987. [3] AA Mostafa, CM Krowne ... Dec. 1987. [4] A. Knoesen, TK Gaylord and MG Moharam, "Hy-brid guided modes in uniaxial dielectric planar waveg-uides",J. Lightwave Tech., vol. LT-6, pp. 1083-1104, June 1988. ...
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Papers by António Topa