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Arturo Vegas - One of the best experts on this subject based on the ideXlab platform.

  • Stability and Accuracy of a Finite-Difference Time-Domain Scheme for Modeling Double-Negative Media With High-Order Rational Constitutive Parameters
    IEEE Transactions on Microwave Theory and Techniques, 2008
    Co-Authors: Ana Grande, Oscar Gonzalez, JosÉ A. Pereda, Arturo Vegas
    Abstract:

    This paper introduces an extension of the original finite-difference time-domain (FDTD) method for modeling double-negative media characterized by high-order frequency-dependent permittivity and permeability. The approach basically consists of adding electric and magnetic current densities to Maxwell's curl equations and considering Ohm's law as a constitutive relationship. Current densities are discretized by using a weighted average in time and Ohm's law by applying the Mobius Transformation technique. The extended FDTD formulation is validated and its numerical features are carefully examined. More specifically, analytical stability conditions are derived for several types of double-negative media and the numerical dissipation issue is discussed. In addition, the numerical dispersion equation for general high-order double-negative media is given and the order of accuracy of the scheme is studied. Finally, the definition of numerical refractive index is addressed and it is shown that, when the discretization parameters of the problem are not properly chosen, a negative refractive index may become a positive one in the discrete world, thus changing the physics of the problem.

  • FDTD Modeling of Chiral Media by Using the Mobius Transformation Technique
    IEEE Antennas and Wireless Propagation Letters, 2006
    Co-Authors: J.A. Pereda, Andrew Grande, Oscar Gonzalez, Arturo Vegas
    Abstract:

    This letter introduces a new technique for finite-difference time-domain (FDTD) modeling of electromagnetic wave propagation in frequency-dispersive chiral media. First, Maxwell's curl equations are discretized according to Yee's scheme. Then the constitutive relations, expressed in the Laplace domain, are discretized using the Mobius Transformation technique and appropriate digital-processing methodologies. The resulting formulation is explicit and preserves the second-order accuracy of the conventional FDTD technique. To show the validity of the method, the reflection and transmission coefficients of a chiral slab are computed and compared to the exact results, with good agreement being obtained

  • FDTD modeling of chiral media by using the Mobius Transformation technique
    IEEE Antennas and Wireless Propagation Letters, 2006
    Co-Authors: J.A. Pereda, Andrew Grande, Oscar Gonzalez, Arturo Vegas
    Abstract:

    This paper introduces a technique for finite-difference time-domain modeling of wave propagation in general Mth-order dispersive media. Ohm's law in the Laplace domain with an Mth-order rational model for the complex conductivity is considered as a constitutive relation. In order to discretize this model, the complex conductivity is mapped onto the Z-transform domain by means of the Mobius Transformation. This leads finally to a set of difference equations that is consistent with Yee's scheme. The resulting formulation is explicit, it has a second-order accuracy, and the need for additional storage variables is minimal. The numerical stability problem is discussed and the numerical dispersion equation for Mth-order media is given

  • An extension of the lumped-network FDTD method to linear two-port lumped circuits
    IEEE Transactions on Microwave Theory and Techniques, 2006
    Co-Authors: O. Gonzalez, J.A. Pereda, A. Herrera, Arturo Vegas
    Abstract:

    The lumped-network finite-difference time-domain (LN-FDTD) technique is an extension of the conventional finite-difference time-domain (FDTD) method that allows the systematic incorporation of linear one-port lumped networks (LNs) into a single FDTD cell. This paper presents an extension of the LN-FDTD technique, which allows linear two-port (TP)-LNs to be incorporated into the FDTD framework. The method basically consists of describing a TP-LN by means of its admittance matrix in the Laplace domain. By applying the Mobius Transformation technique, we then obtain the admittance matrix of the TP-LN in the Z-transform domain. Finally, appropriate digital signal-processing methodologies are used to derive a set of difference equations that models the TP-LN behavior in the discrete-time domain. These equations are solved in combination with the Maxwell-Ampere's equation. To show the validity of the TP-LN-FDTD technique introduced here, we have considered the equivalent circuit of a chip capacitor and a linear circuit model of a generic metal-semiconductor field-effect transistor. These LNs have been placed on a microstrip gap and the scattering parameters of the resulting hybrid circuit have been computed. The results are compared with those obtained by using the electromagnetic simulator Agilent HFSS in combination with the circuital simulator ADS, and with those calculated by ADS alone. For the chip capacitor, experimental measurements have also been carried out. The agreement among all the simulated results is good. Generally speaking, the measured results agree with the simulated ones. The differences observed are mainly due to the influence of the subminiature A connectors and some mismatching at the ports.

  • FDTD modeling of wave propagation in dispersive media by using the Mobius Transformation technique
    … Theory and Techniques IEEE …, 2002
    Co-Authors: J.A. Pereda, Arturo Vegas, AG Prieto
    Abstract:

    This paper introduces a technique for finite-difference time-domain modeling of wave propagation in general th-order dispersive media. Ohm’s law in the Laplace domain with an th-order rational model for the complex conductivity is considered as a constitutive relation. In order to discretize this model, the complex conductivity is mapped onto the -transform domain by means of the Mobius Transformation. This leads finally to a set of difference equations that is consistent with Yee’s scheme. The resulting formulation is explicit, it has a second-order accuracy, and the need for additional storage variables is minimal. The numerical stability problem is discussed and the numerical dispersion equation for th-order media is given.

J.A. Pereda - One of the best experts on this subject based on the ideXlab platform.

  • FDTD Modeling of Chiral Media by Using the Mobius Transformation Technique
    IEEE Antennas and Wireless Propagation Letters, 2006
    Co-Authors: J.A. Pereda, Andrew Grande, Oscar Gonzalez, Arturo Vegas
    Abstract:

    This letter introduces a new technique for finite-difference time-domain (FDTD) modeling of electromagnetic wave propagation in frequency-dispersive chiral media. First, Maxwell's curl equations are discretized according to Yee's scheme. Then the constitutive relations, expressed in the Laplace domain, are discretized using the Mobius Transformation technique and appropriate digital-processing methodologies. The resulting formulation is explicit and preserves the second-order accuracy of the conventional FDTD technique. To show the validity of the method, the reflection and transmission coefficients of a chiral slab are computed and compared to the exact results, with good agreement being obtained

  • FDTD modeling of chiral media by using the Mobius Transformation technique
    IEEE Antennas and Wireless Propagation Letters, 2006
    Co-Authors: J.A. Pereda, Andrew Grande, Oscar Gonzalez, Arturo Vegas
    Abstract:

    This paper introduces a technique for finite-difference time-domain modeling of wave propagation in general Mth-order dispersive media. Ohm's law in the Laplace domain with an Mth-order rational model for the complex conductivity is considered as a constitutive relation. In order to discretize this model, the complex conductivity is mapped onto the Z-transform domain by means of the Mobius Transformation. This leads finally to a set of difference equations that is consistent with Yee's scheme. The resulting formulation is explicit, it has a second-order accuracy, and the need for additional storage variables is minimal. The numerical stability problem is discussed and the numerical dispersion equation for Mth-order media is given

  • An extension of the lumped-network FDTD method to linear two-port lumped circuits
    IEEE Transactions on Microwave Theory and Techniques, 2006
    Co-Authors: O. Gonzalez, J.A. Pereda, A. Herrera, Arturo Vegas
    Abstract:

    The lumped-network finite-difference time-domain (LN-FDTD) technique is an extension of the conventional finite-difference time-domain (FDTD) method that allows the systematic incorporation of linear one-port lumped networks (LNs) into a single FDTD cell. This paper presents an extension of the LN-FDTD technique, which allows linear two-port (TP)-LNs to be incorporated into the FDTD framework. The method basically consists of describing a TP-LN by means of its admittance matrix in the Laplace domain. By applying the Mobius Transformation technique, we then obtain the admittance matrix of the TP-LN in the Z-transform domain. Finally, appropriate digital signal-processing methodologies are used to derive a set of difference equations that models the TP-LN behavior in the discrete-time domain. These equations are solved in combination with the Maxwell-Ampere's equation. To show the validity of the TP-LN-FDTD technique introduced here, we have considered the equivalent circuit of a chip capacitor and a linear circuit model of a generic metal-semiconductor field-effect transistor. These LNs have been placed on a microstrip gap and the scattering parameters of the resulting hybrid circuit have been computed. The results are compared with those obtained by using the electromagnetic simulator Agilent HFSS in combination with the circuital simulator ADS, and with those calculated by ADS alone. For the chip capacitor, experimental measurements have also been carried out. The agreement among all the simulated results is good. Generally speaking, the measured results agree with the simulated ones. The differences observed are mainly due to the influence of the subminiature A connectors and some mismatching at the ports.

  • FDTD modeling of wave propagation in dispersive media by using the Mobius Transformation technique
    … Theory and Techniques IEEE …, 2002
    Co-Authors: J.A. Pereda, Arturo Vegas, AG Prieto
    Abstract:

    This paper introduces a technique for finite-difference time-domain modeling of wave propagation in general th-order dispersive media. Ohm’s law in the Laplace domain with an th-order rational model for the complex conductivity is considered as a constitutive relation. In order to discretize this model, the complex conductivity is mapped onto the -transform domain by means of the Mobius Transformation. This leads finally to a set of difference equations that is consistent with Yee’s scheme. The resulting formulation is explicit, it has a second-order accuracy, and the need for additional storage variables is minimal. The numerical stability problem is discussed and the numerical dispersion equation for th-order media is given.

Oscar Gonzalez - One of the best experts on this subject based on the ideXlab platform.

  • Stability and Accuracy of a Finite-Difference Time-Domain Scheme for Modeling Double-Negative Media With High-Order Rational Constitutive Parameters
    IEEE Transactions on Microwave Theory and Techniques, 2008
    Co-Authors: Ana Grande, Oscar Gonzalez, JosÉ A. Pereda, Arturo Vegas
    Abstract:

    This paper introduces an extension of the original finite-difference time-domain (FDTD) method for modeling double-negative media characterized by high-order frequency-dependent permittivity and permeability. The approach basically consists of adding electric and magnetic current densities to Maxwell's curl equations and considering Ohm's law as a constitutive relationship. Current densities are discretized by using a weighted average in time and Ohm's law by applying the Mobius Transformation technique. The extended FDTD formulation is validated and its numerical features are carefully examined. More specifically, analytical stability conditions are derived for several types of double-negative media and the numerical dissipation issue is discussed. In addition, the numerical dispersion equation for general high-order double-negative media is given and the order of accuracy of the scheme is studied. Finally, the definition of numerical refractive index is addressed and it is shown that, when the discretization parameters of the problem are not properly chosen, a negative refractive index may become a positive one in the discrete world, thus changing the physics of the problem.

  • FDTD modeling of chiral media by using the Mobius Transformation technique
    IEEE Antennas and Wireless Propagation Letters, 2006
    Co-Authors: J.A. Pereda, Andrew Grande, Oscar Gonzalez, Arturo Vegas
    Abstract:

    This paper introduces a technique for finite-difference time-domain modeling of wave propagation in general Mth-order dispersive media. Ohm's law in the Laplace domain with an Mth-order rational model for the complex conductivity is considered as a constitutive relation. In order to discretize this model, the complex conductivity is mapped onto the Z-transform domain by means of the Mobius Transformation. This leads finally to a set of difference equations that is consistent with Yee's scheme. The resulting formulation is explicit, it has a second-order accuracy, and the need for additional storage variables is minimal. The numerical stability problem is discussed and the numerical dispersion equation for Mth-order media is given

  • FDTD Modeling of Chiral Media by Using the Mobius Transformation Technique
    IEEE Antennas and Wireless Propagation Letters, 2006
    Co-Authors: J.A. Pereda, Andrew Grande, Oscar Gonzalez, Arturo Vegas
    Abstract:

    This letter introduces a new technique for finite-difference time-domain (FDTD) modeling of electromagnetic wave propagation in frequency-dispersive chiral media. First, Maxwell's curl equations are discretized according to Yee's scheme. Then the constitutive relations, expressed in the Laplace domain, are discretized using the Mobius Transformation technique and appropriate digital-processing methodologies. The resulting formulation is explicit and preserves the second-order accuracy of the conventional FDTD technique. To show the validity of the method, the reflection and transmission coefficients of a chiral slab are computed and compared to the exact results, with good agreement being obtained

D Giannacopoulos - One of the best experts on this subject based on the ideXlab platform.

  • finite element time domain solution of the vector wave equation in doubly dispersive media using Mobius Transformation technique
    IEEE Transactions on Antennas and Propagation, 2013
    Co-Authors: Ali Akbarzadehsharbaf, D Giannacopoulos
    Abstract:

    Several finite-element time-domain (FETD) formulations to model inhomogeneous and electrically/magnetically/doubly dispersive materials based on the second-order vector wave equation discretized by the Newmark-β scheme are developed. In contrast to the existing formulations, which employ recursive convolution (RC) approaches, we use a Mobius Transformation method to derive our new formulations. Hence, the obtained equations are not only simpler in form and easier to derive and implement, but also do not suffer from the intrinsic limitations of the RC methods in modeling arbitrary high-order media. To obtain the formulations, we first demonstrate that the update equation for the electric field strength {e} in the mixed Crank-Nicolson (CN) FETD formulation, which is based on expanding the electric and magnetic field in terms of the edge and face elements in space and discretizing the resultant first-order differential equations using Crank-Nicolson scheme in time, is equivalent to the unconditionally stable (US) second-order vector wave equation for the same variable ( {e}) discretized by the Newmark- β method with β = 1/4. In addition, we show that the update equation for the magnetic flux density {b} in CN-FETD is the same as the second-order vector wave equation for {b} on the dual grid discretized again by a similar Newmark-β method. Subsequently, thanks to the mixed FETD formulation properties, we derive update equations for the constitutive relations using a Mobius Transformation method separately. In addition, we use the shown equivalence to derive formulations based on the vector wave equation. Finally, several numerical examples are solved to validate the developed formulations.

V. Hansen - One of the best experts on this subject based on the ideXlab platform.

  • Fullwave analysis of planar microwave circuits by integral equation methods and bilinear Transformations
    IEEE Transactions on Microwave Theory and Techniques, 1992
    Co-Authors: A. Janhsen, B. Schiek, V. Hansen
    Abstract:

    Planar microwave circuits are simulated by a mixed space-spectral domain integral method which allows the consideration of space-varying impedances. For an efficient computation of scattering parameters of circuits containing lumped elements within this fullwave analysis, a bilinear Transformation is used. Furthermore, by this so-called Mobius Transformation it is possible to decide whether an impedance region of finite size can be interpreted as a lumped element or not. Applications to microstrip circuits are discussed.