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Papers by Hongjin Choi

Research paper thumbnail of Communication Numerical Stability and Accuracy of CCPR-FDTD for Dispersive Media

IEEE Transactions on Antennas and Propagation

Research paper thumbnail of Accurate and Efficient Finite-Difference Time-Domain Simulation Compared with CCPR Model for Complex Dispersive Media

IEEE Access

Recently, it has received a great deal of attention to analyze the electromagnetic wave problems ... more Recently, it has received a great deal of attention to analyze the electromagnetic wave problems in dispersive media by using the finite-difference time-domain (FDTD) method. Accordingly, it is of great importance to employ a proper dispersion model which can fit the frequency-dependent permittivity of a medium considered. The reported dispersion models include Debye, Drude, Lorentz, modified Lorentz, quadratic complex rational function, complex-conjugate pole-residue (CCPR) models. The CCPR dispersion model has advantage over other dispersion models in the fact that accurate CCPR dispersion parameters can be simply extracted by using the powerful and robust vector fitting tool which has been widely used in the circuit theory. However, the arithmetic operation of CCPR-based FDTD implementation is involved with complex-valued numbers and thus its numerical computation is not efficient. In this work, we propose an accurate and efficient FDTD simulation for complex dispersive media. In specific, an accurate CCPR dispersion model is simply obtained using the vector fitting tool and then the CCPR dispersion model is converted to the modified Lorentz dispersion model which leads to the arithmetic operation of only real-valued numbers in its FDTD implementation. Numerical examples are used to illustrate the accuracy and efficiency of our dispersive FDTD simulation. INDEX TERMS Dispersion model, dispersive media, finite-difference time-domain (FDTD) method, human tissue, plasmonics.

Research paper thumbnail of Comprehensive Study on Numerical Aspects of Modified Lorentz Model Based Dispersive FDTD Formulations

IEEE Transactions on Antennas and Propagation

Research paper thumbnail of Newmark-FDTD Formulation for Modified Lorentz Dispersive Medium and Its Equivalence to Auxiliary Differential Equation-FDTD with Bilinear Transformation

International Journal of Antennas and Propagation

The finite-difference time-domain (FDTD) method has been popularly utilized to analyze the electr... more The finite-difference time-domain (FDTD) method has been popularly utilized to analyze the electromagnetic (EM) wave propagation in dispersive media. Various dispersion models were introduced to consider the frequency-dependent permittivity, including Debye, Drude, Lorentz, quadratic complex rational function, complex-conjugate pole-residue, and critical point models. The Newmark-FDTD method was recently proposed for the EM analysis of dispersive media and it was shown that the proposed Newmark-FDTD method can give higher stability and better accuracy compared to the conventional auxiliary differential equation- (ADE-) FDTD method. In this work, we extend the Newmark-FDTD method to modified Lorentz medium, which can simply unify aforementioned dispersion models. Moreover, it is found that the ADE-FDTD formulation based on the bilinear transformation is exactly the same as the Newmark-FDTD formulation which can have higher stability and better accuracy compared to the conventional AD...

Research paper thumbnail of FDTD Modeling for the Accurate Electromagnetic Wave Analysis of Graphene

Journal of Electrical Engineering & Technology

Research paper thumbnail of Communication Numerical Stability and Accuracy of CCPR-FDTD for Dispersive Media

IEEE Transactions on Antennas and Propagation

Research paper thumbnail of Accurate and Efficient Finite-Difference Time-Domain Simulation Compared with CCPR Model for Complex Dispersive Media

IEEE Access

Recently, it has received a great deal of attention to analyze the electromagnetic wave problems ... more Recently, it has received a great deal of attention to analyze the electromagnetic wave problems in dispersive media by using the finite-difference time-domain (FDTD) method. Accordingly, it is of great importance to employ a proper dispersion model which can fit the frequency-dependent permittivity of a medium considered. The reported dispersion models include Debye, Drude, Lorentz, modified Lorentz, quadratic complex rational function, complex-conjugate pole-residue (CCPR) models. The CCPR dispersion model has advantage over other dispersion models in the fact that accurate CCPR dispersion parameters can be simply extracted by using the powerful and robust vector fitting tool which has been widely used in the circuit theory. However, the arithmetic operation of CCPR-based FDTD implementation is involved with complex-valued numbers and thus its numerical computation is not efficient. In this work, we propose an accurate and efficient FDTD simulation for complex dispersive media. In specific, an accurate CCPR dispersion model is simply obtained using the vector fitting tool and then the CCPR dispersion model is converted to the modified Lorentz dispersion model which leads to the arithmetic operation of only real-valued numbers in its FDTD implementation. Numerical examples are used to illustrate the accuracy and efficiency of our dispersive FDTD simulation. INDEX TERMS Dispersion model, dispersive media, finite-difference time-domain (FDTD) method, human tissue, plasmonics.

Research paper thumbnail of Comprehensive Study on Numerical Aspects of Modified Lorentz Model Based Dispersive FDTD Formulations

IEEE Transactions on Antennas and Propagation

Research paper thumbnail of Newmark-FDTD Formulation for Modified Lorentz Dispersive Medium and Its Equivalence to Auxiliary Differential Equation-FDTD with Bilinear Transformation

International Journal of Antennas and Propagation

The finite-difference time-domain (FDTD) method has been popularly utilized to analyze the electr... more The finite-difference time-domain (FDTD) method has been popularly utilized to analyze the electromagnetic (EM) wave propagation in dispersive media. Various dispersion models were introduced to consider the frequency-dependent permittivity, including Debye, Drude, Lorentz, quadratic complex rational function, complex-conjugate pole-residue, and critical point models. The Newmark-FDTD method was recently proposed for the EM analysis of dispersive media and it was shown that the proposed Newmark-FDTD method can give higher stability and better accuracy compared to the conventional auxiliary differential equation- (ADE-) FDTD method. In this work, we extend the Newmark-FDTD method to modified Lorentz medium, which can simply unify aforementioned dispersion models. Moreover, it is found that the ADE-FDTD formulation based on the bilinear transformation is exactly the same as the Newmark-FDTD formulation which can have higher stability and better accuracy compared to the conventional AD...

Research paper thumbnail of FDTD Modeling for the Accurate Electromagnetic Wave Analysis of Graphene

Journal of Electrical Engineering & Technology

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