Homayoon Oraizi

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It is proposed that the application of defected ground structures (DGS) and electromagnetic bandgap (EBG) reduce the phase velocity, increase effective permittivity of microstrips and reduce the effective the wavelength which eventually lead to the reduction of overall length of Wilkinson power dividers. Furthermore, the adjacent strip lines may approach(More)
A two-way Gysel power divider is proposed as a modification of the common five-port Gysel divider, which has several advantages such as high power-handling capability and suitability for multi-staging to increase the frequency bandwidth. The even- and odd-mode technique is used to analyze its performance and the method of least squares is used to devise a(More)
Fast full-wave computation of fields is the main reason for a radio system planner to apply the parabolic-equation method (PEM) for radio-coverage prediction. In this paper, the capability of PEM for the determination of backward electromagnetic-field scattering by single and multiple knife edges is investigated. For the wave equation, a suitable solution(More)
This paper proposes a new smart antenna for CDMA using Nelder-Mead (NM) simplex algorithm and a new structure different from the uniform linear array. This smart antenna consists of an active element in the center of a circle having a number of passive elements with variable reactances on its peripheral (it is called an electronically steerable passive(More)
In this paper, a numerical algorithm based on the method of least squares (MLS) is presented for the design and optimization of a Wilkinson power divider for arbitrary power division between its outputs in a specified frequency bandwidth incorporating source and load impedance matching. At first, its transmission, admittance, and scattering matrices are(More)
A general analysis and design procedure is developed for the asymmetrical multisection power divider with arbitrary power division ratio and arbitrary specifications of input and output impedance matching over any desired frequency bandwidth. The even- and odd-mode analysis, which was previously applied to the design of multisection Gysel power dividers,(More)
In this paper the electromagnetic wave scattering from multilayered cylindrical structures is studied for a normally incident plane wave with linear (TE or TM), circular and elliptical polarizations. The cylindrical layers may be composed of any combination of dispersive common materials and metamaterials. The addition theorems for the cylindrical waves are(More)
We introduce and investigate the applications of double zero (DZR) metamaterials (having the real parts of permittivity and permeability equal to zero) as radar absorbing materials (RAMs). We consider a perfectly electric conductor (PEC) plate covered by several layers of DZR metamaterial coatings under an oblique plane wave incidence of arbitrary(More)
The influence of semi-planar chiral metamaterial (CMM) structures on the important characteristics of circularly polarized (CP) antennas is investigated in this paper. Based on this idea, CP planar two-arm Archimedean spiral (ARSPL) antenna and helical antenna are designed and the effects of chiral covers on their gain (or directivity), axial-ratio (AR),(More)