Shahwan Khoury

A RECONFIGURABLE U-KOCH MICROSTRIP ANTENNA FOR WIRELESS APPLICATIONS

In this paper, a low-cost multiband printed-circuit-board (PCB) antenna that employs Koch fractal geometry and tunability is demonstrated. The antenna is fabricated on a 1.6mm-thick FR4- epoxy substrate with dimensions 4cm £ 4.5cm, is microstrip-line fed and has a partial ground plane ∞ushed with the feed line. The proposed antenna is simulated using the Finite-Element Method for three difierent switching cases and the return loss is measured for each case. It is shown that the antenna can cover the bands of several applications including 3G, WiFi, WiMAX as well as a portion of the UWB range. The radiation patterns are satisfactorily omnidirectional across the antennas operation bands.

A linear control system simulation toolbox using spreadsheets

A new method is presented for simulating linear control systems using modern spreadsheet programs. The method is characterized by its flexibility, simplicity, and availability. It was verified for various cases, and examples were given for illustration. It is particularly useful for educational exercises that require calculations to be repeated with different parameters and values.

Electromagnetic coupling between two half-space regions separated by multiple slot-perforated parallel conducting screens

Considers the problem of electromagnetic coupling between two half-space regions separated by multiple slot-perforated parallel conducting screens. The fields are considered to be excited by either a transverse electric (TE) or a transverse magnetic (TM) plane wave. A characteristic mode solution is used for the computation of the fields in each half-space. Special attention is given to the power transmitted from one half-space to the other through the slots and to its functional dependence on various parameters. Numerical examples are presented for illustration and comparison. >

Electromagnetic coupling to conducting objects behind apertures in a conducting body

A procedure for computing characteristic modes for the problem of electromagnetic coupling to arbitrary shape conducting objects behind arbitrary shape apertures in a conducting body is developed starting from the operator formulation of the currents. The mode currents are obtained from the admittance and impedance operators. This formulation is general and characterized by its simplicity and efficiency. This method is applied to a finite thin wire backed by a rectangular aperture in a conducting plane in an unbounded medium. The integral equations in terms of the magnetic and electric current distributions are derived for the magnetic and electric fields. The moment method is used to obtain matrix equations approximating the integral equations. The expansion functions are chosen to satisfy the continuity equations and to vanish at the wire endpoints. Finally, modal solutions are computed to illustrate the convergence of the solution as the number of modes increases.

Electromagnetic radiation and scattering at the American University of Beirut

This paper presents the work carried out at the American University of Beirut on electromagnetic radiation and scattering, using the characteristic-modes theory. Several problems of various two-dimensional and three-dimensional geometrics have been considered: slots in a plane, slots in a conducting cylinder, a parallel plate-fed slot antenna, an aperture-fed waveguide, a rectangular aperture in a perfectly conducting plane, a cavity-backed aperture. The characteristic modes for each geometry were first computed, and the convergence of the solution was tested for all these problems. A combined characteristic-modes formulation, for the problem of electromagnetic coupling to conducting objects behind arbitrary apertures in a conducting plane, has been developed and used to solve many of these problems.