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Abstract-This paper demonstrates the one-dimensional computational results of the propagation of Gaussian electromagnetic pulse through dielectric slabs of finite thickness with variation in permittivity. The numerical approach used is the characteristic-based method solving the time-domain Maxwell curl equations involved with nonuniform permittivity. In the numerical model, all dielectric slabs are assumed to be isotropic, lossless, and linear. The permittivity of dielectric slab may increase or decrease linearly or sinusoidally. The numerical permittivity is finely discretized such that the variation between two adjacent grids is so small that the non-uniform permittivity is assumed to be piecewise continuous and consequently can be modeled as an individual block. The numerical results of various electric fields, both in the time-and frequency-domain, are presented and compared based on the dielectric slab of constant permittivity for close investigating the effects of the non-uniform permittivity distribution on the electromagnetic fields. It is also shown that under certain arrangement of Gaussian electromagnetic pulse and dielectric slab thickness the pattern of field propagation, reflection and transmission, can be reproduced in different time scales and frequency ranges.

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Abstract-In this report one-dimensional simulation of Electromagnetic pulses reflected from moving and/or vibrating perfectly conducting surfaces is presented. The computational results are obtained through the application of the method of characteristics with the aid of the characteristic variable and the relativistic boundary conditions. The reflecting perfect surface is set to constantly travel at relatively high speed and/or sinusoidally vibrate with very high frequency in order to easily observe the relativistic effects on the reflected pulses. To validate the numerical method, the reflected electric fields and the corresponding spectra are demonstrated side-by-side for comparisons with the theoretical Doppler shift values. It is found that the computational results and the theoretical values are in good agreement.

Abstract-In this paper, a new numerical technique, passing center swing back grids (PCSBG's) for the resolution of the grid distortion difficulty due to the rotational motion of objects is introduced. This proposed swing-back-grids approach alongside of the method of characteristics (MOC) is developed to solve EM scattering problems featured with rotating objects. The feasibility of such combination is apparent from the fact that MOC defines all field quantities in the centroid of the grid cell. The scattered EM fields from a rotating circular cylinder under the excitation of an EM pulse are predicted in two dimensions and the electric field distributions recorded at several time instances are demonstrated. In order to confirm that the cylinder is rotating and scattering EM fields simultaneously, the circular cylinder is uniformly divided into an even number of slices with one perfect reflector and one non-reflector alternatively since a rotating circular cylinder causes no relativistic effects.

TwoJinite-direrence time-domain (FDTD) algorithms for computing scattered electromagnetic fields are compared. The Yee algorithm [IJ is compared to a characteristic-based algorithm [2] using a simple twodimensional geometry.The scattered Jields cf a conducting strip given an incident transverse magneticshort-duration Gaussian pulse are computed using both algorithms. The characteristics qf the scattered fields are compared.

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