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This article presents an accurate finite-difference time domain (FDTD) dispersive modelling suitable for complex dispersive media. A quadratic complex rational function (QCRF) is used to characterise their dispersive relations. To obtain accurate coefficients of QCRF, in this work, we use an analytical approach and a particle swarm optimisation (PSO) simultaneously. In specific, an analytical approach is used to obtain the QCRF matrix-solving equation and PSO is applied to adjust a weighting function of this equation. Numerical examples are used to illustrate the validity of the proposed FDTD dispersion model. [ABSTRACT FROM PUBLISHER]

Recently, based on a quadratic complex rational function, a simple and accurate finite-difference time-domain algorithm was introduced for the study of electromagnetic wave propagation in dispersive media. It is of great necessity to investigate the numerical stability of the quadratic complex rational function–finite-difference time-domain to fully utilize this finite-difference time-domain algorithm. In this work, using the von Neumann method with the Routh–Hurwitz criterion, the numerical stability conditions of the quadratic complex rational function–finite-difference time-domain are investigated. It is shown that the numerical stability conditions of the quadratic complex rational function–finite-difference time-domain are not same as those of the conventional finite-difference time-domain schemes. [ABSTRACT FROM AUTHOR]

Recently, based on a quadratic complex rational function, an attractive finite-difference time-domain algorithm was suggested for dispersive modeling of complex media because it is accurate and easy to implement. To fully utilize the quadratic complex rational function finite-difference time-domain, it is essential to investigate its numerical errors based on an exact mathematical approach. Toward this purpose, the exact expression of the numerical permittivity is first derived. From this numerical permittivity, the numerical dispersion, numerical dissipation, and numerical anisotropy inherent to the quadratic complex rational function finite-difference time-domain are examined. Numerical examples illustrate that the numerical errors of the quadratic complex rational function finite-difference time-domain is almost same as those of the nondispersive finite-difference time-domain. [ABSTRACT FROM AUTHOR]

Mode-matching analysis of a coaxially fed annular slot surrounded by corrugations is conducted in this study. An electromagnetic boundary value problem of a coaxially fed annular slot surrounded with corrugations is rigorously solved based on the Hankel transform, eigenfunction expansion, and mode-matching method. The radiated field is represented in a fast-convergent series that is amenable to numerical analysis. Numerical results are presented to illustrate the radiation behaviors in terms of the geometries of the corrugations and compared with measurement data. [ABSTRACT FROM AUTHOR]

Electromagnetic transmission through a slit surrounded by rectangular grooves in a conducting plane is investigated. An electromagnetic boundary-value problem associated with a slit surrounded by rectangular grooves in a conducting plane is rigorously solved based on the Fourier transform, eigenfunction expansion and mode matching method. The transmission coefficient through the slit is represented in a series. Computation is performed to illustrate the effect of the groove geometry on the transmission behaviours. [ABSTRACT FROM AUTHOR]

Enhanced transmission through a circular aperture surrounded by concentric surface corrugations in a conducting plane is investigated. A boundary-value problem of electromagnetic wave scattering from a circular aperture surrounded by concentric surface corrugations is rigorously solved based on the Hankel transform, eigenfunction expansion, and mode-matching method. The transmission coefficient is represented in a fast-convergent series that is amenable to numerical analysis. Computation is performed to illustrate the transmission behaviors in terms of the geometries of the concentric corrugations. The effects of the higher-order modes on the transmission coefficients are also discussed. [ABSTRACT FROM AUTHOR]

Directional emission from a slit surrounded by rectangular grooves on the exit surface in a conducting plane is investigated. An electromagnetic boundary-value problem dealing with a slit surrounded by rectangular grooves on the exit surface in a conducting plane is rigourously solved based on the Fourier transform, eigenfunction expansion, and mode-matching method. The radiation pattern from the slit is represented in a series and computed to illustrate the radiation behaviors in terms of the groove geometry. [ABSTRACT FROM PUBLISHER]