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ABSTRACT: In this work, we present a marching-on-in-degree (MOD) method in a finite difference time-domain (FDTD) framework for analyzing transient electromagnetic responses in a general dispersive media.The two issues related to the finite difference approximation of the time derivatives and the time-consuming convolution operations are handled analytically using the properties of the associated Laguerre functions. The basic idea here is that we fit the transient nature of the fields, the flux densities, the permittivity and the permeability with a finite sum of orthogonal associated Laguerre functions. Through this novel approach, not only the time variable can be decoupled analytically from the temporal variations but also the final computational form of the equations is transformed from FDTD to a FD formulation through a Galerkin testing. We also propose a second MOD formulation based on the Helmholtz wave equation. Representative numerical examples are presented for transient wave propagation in general Debye, Drude, or a Lorentz dispersive medium. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:925–930, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26696
Microwave and Optical Technology Letters 02/2012; 54(4):925 - 930. · 0.62 Impact Factor
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ABSTRACT: A discrete finite time domain pulse is designed under the constraint of the Federal Communications Commission (FCC) ultrawideband (UWB) spectral mask. This pulse also enjoys the advantage of having a linear phase over the frequency band of interest and is orthogonal to its shifted version of one or more baud time. The finite time pulse is designed by an optimization method and concentrates its energy in the allowed bands specified by the FCC. Finally, an example is presented to illustrate how these types of wideband pulses can be transmitted and received with little distortion.
IEEE Transactions on Antennas and Propagation 05/2011; · 2.15 Impact Factor
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ABSTRACT: The objective of this letter is to present a solution methodology for the analysis of arbitrary frequency-dependent losses on conducting structures in a time-domain electric field integral equation. The analysis of arbitrary frequency-dependent losses is incorporated in the newly developed marching-on-in-degree (MOD) method to solve the time-domain electric field integral equation. The novelty of this methodology is that both the arbitrary temporal dependence of the frequency-dependent losses and the transient current variations on the conducting structures are expanded in terms of the causal orthonormal associated Laguerre functions. The advantage of implementing these temporal expansion functions is that the convolution between two functional variations, namely the loss factor and the current density, can be treated in an analytical fashion resulting in an accurate and efficient solution methodology. Numerical examples dealing with both time-varying concentrated loads and skin-effect losses on electrically large conducting structures are analyzed to illustrate the potential of this method.
IEEE Antennas and Wireless Propagation Letters 02/2011; · 1.37 Impact Factor
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ABSTRACT: In this paper, we solve the scattering and radiation problem of conducting objects with loading by applying time domain electric field integration equation (TD-EFIE). Marching-on-in-degree (MOD) method is used in the solving procedure in order to acquire an absolute late-time stable result. We also use a combination of Laguerre polynomials as temporal basis function so that the equation can be simplified.
Antennas and Propagation Society International Symposium (APSURSI), 2010 IEEE; 08/2010
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ABSTRACT: In this paper, a marching-on in degree solution to the problem of time domain electric field integer equation is presented where the higher order basis functions are employed for the spatial expansion. The marching-on in degree method can obtain a solution that is late-time stable, which is marching-on in time method cannot. Numerical result is presented to show the accuracy of the MOD method with higher order basis functions.
Antennas and Propagation Society International Symposium, 2009. APSURSI '09. IEEE; 07/2009
