An Analysis of the Finite-Difference Time-Domain Method for Modeling the Microwave Heating of Dielectric Materials Within a Three-Dimensional Cavity System

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Abstract
In this paper, an investigation of the microwave heating of a lossy material located inside a cavity by the Finite-Difference Time-Domain (FD-TD) method is undertaken. The emphasis of this work focuses on the performance of the FD-TD method when certain traditional assumptions are used within the framework of the model. The limitations of these assumptions will be deliberated and more accurate counterparts will be proposed and tested. In particular, it will be shown that when only a single mode is assumed to exist around the aperture between the wave guide and the cavity, spurious numerical resiilts arise. Further, the numerical simulation indicates that the treatment of the interfacial boundary condition located between free-space and the material becomes very important when predicting the dissipated power distribution for a lossy dielectric material. A new approximation of this interfacial boundary condition is developed and a comparison between existing and new methodologies is made. The treatment of singular field behavior near sharp edges of the cavity is also examined and a study of the effect of using different techniques to model regions where this condition arises is presented. In order to validate the numerical simulation results, comparisons against experimental data sets previously reported in the literature will be made. In summary, the new techniques proposed in this research yield a solution of high accuracy and demonstrate an increased flexibility for simulating microwave systems. It will be shown that the FD-TD method satisfies the important Maxwell equation field divergence condition everywhere within the applicator.

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