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The finite-difference time-domain (FDTD) technique for simulating electromagnetic wave interaction with a dispersive chiral medium is extended to include the simulation of dispersive bianisotropic media. Due to anisotropy and frequency dispersion of such media, the constitutive parameters are represented by frequency-dependent tensors. The FDTD is formulated using the Z-transform method, a conventional approach for applying FDTD in frequency-dispersive media. Omega medium is considered as an example of bianisotropic media, the frequency-dependent tensors of which are based on analytical models. The extended FDTD method is used to determine the reflection and transmission coefficients of co-and cross-polarized electromagnetic waves from omega slabs, illuminated by normally incident plane waves. Three cases are simulated: 1) a slab of uniaxial omega medium with its optical axis parallel to the propagation vector; 2) a slab of rotated uniaxial omega medium with its optical axis not parallel to the propagation vector; and 3) a slab of biaxial omega medium. The results are validated by means of comparisons with analytical solutions.Index Terms-Bianisotropic media, chiral medium, dispersive media, finite-difference time-domain (FDTD), omega medium, Z-transform method.

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This paper studies the radiation properties of aperture antennas above imperfect ground using Discrete Complex Image Method (DCIM). The present method is simple and has high accuracy. In this approach, based on linear approximating a function to an exponential series, equivalent complex images have been obtained. Number, intensity and location of images are obtained using Generalized Pencil Of Function (GPOF) technique. We assume current distribution over the aperture be combination of electric and magnetic currents in vertical and horizontal direction. The obtained results are comparable with analytical computation in limited cases. In spite of Sommerfeld integral based methods, this method is simple with lower computational time.

This paper describes the design and realization of a multimode tracking feed antenna system, for a circularly polarized wave, which can generate sum and difference patterns suitable for monopulse tracking in remote sensing earth stations. It uses TE 11 and TE 21 modes, in a smooth circular waveguide, to obtain the sum and difference patterns. The higher order mode, TE 21 generated within the feed is separated from the fundamental mode, TE 11 by using a mode coupler. Circular polarization is converted to linear polarization by pin polarizer septum. The design of the multimode corrugated horn and polarizer are described in some details. The prototyped horn designed here operates in the frequency range of 7.2-8.8 GHz. Sum and delta patterns and polarizer axial ratio are presented. The close agreement between measured and simulated data validates the present design.