Khalid A. Nabulsi

A new approximation and a new measurable constraint for slab profile inversion

A new approximation and a new measurable constraint for slab profile inversion is introduced. A comparison is given between the Born, the exact, and the new approximation. The new approximation and constraint can be utilized along with other methods such as the integral equation, the iterative or perturbed Born, and the alternating projection approaches. The latter is considered. The results obtained are superior to those obtained under the Born approximation.

Enhanced electromagnetic power deposition in a lossy medium

It is demonstrated that an aperture antenna, excited by a leaky wave, will transfer power into an homogeneous lossy half-space at levels exceeding expectation. However, such local enhancements are only possible in the near-field region in the central part of the array. With the proper choice of parameters, enhancements of the order of 15 dB can be achieved. The calculated results are relevant to hyperthermic heating in cancer therapy and to related problems in biological hazards. >

Hybrid formulations for scattering from the dielectric slab

For transient excitation, it is well known that the ray optic solution is useful for early time descriptions but is not, in general, suitable for late time. On the other hand, the singularity expansion method (SEM) is a late time technique that is not in general suitable for early time. Perfectly conducting circular cylinder studies have shown that it is possible to obtain two hybrid formulations that utilize the advantages of both the ray optic and the SEM solutions. The hybrid methods yield more efficient representations for both early and late times. Two hybrid formulations that pertain to the dielectric slab are presented. The simplicity of the structure makes it possible to obtain exact and asymptotic representations, where only asymptotic representations are possible for the circular cylinder. >

Space and time wave shaping for transmission into a lossy medium

Electromagnetic waves traveling into a lossy medium suffer distortion in both time and space. This situation poses a design problem if it is desired to have a specified form, in both time and space, for the fields at a given location in the lossy medium. An analytical procedure is presented so that the specified field in a lossy conducting half-space can be realized with a discrete array of concentric loop currents on the surface. Each loop current is stepped on at a finite sequence of discrete times. The procedure could be applied in geophysical subsurface probing, hyperthermic cancer therapy, and digital signal transmission. >

Preforming an electromagnetic field of the axis of a conducting cylinder

An analytical method is described for producing a given spatial form of the electric field along the axis of a conducting homogeneous cylinder. The required excitation on the surface of the cylinder is determined. A confirming forward calculation is also shown using a discrete array of circumferential slots cut in an encasing cylindrical metal sheath. >

On the interaction between the input signal and the singularity expansion method

Abstract For transient excitation, it is well known that the Singularity Expansion Method (SEM) is a late time technique that is not in general suitable for early time. Lossy dielectric slab studies, with bounded integrable finite-duration input signal, have shown that the SEM representation for early time requires an additional branch cut contribution and a modification of the SEM series for completeness. Other researchers indicated that the SEM representation is not complete for most cases of practical interest and that it may not converge for early time. In this paper, we present an approach, using the input signal, to obtain a convergent SEM series that is valid for early as well as for late time. In this approach the branch cut contribution is not needed and instead we have pole contributions form the input signal and a modified SEM series. In addition, two forms of SEM representations will be presented, the traditional form and the time varying coupling coefficient form. Furthermore, the interaction and the effect of the input signal choice on the SEM representation will be clarified. This will be done for a dielectric slab backed by a perfect conductor.

Modified concentric loop for focused electromagnetic heating of limbs and torsos

An idealized two-dimensional model of modified concentric loop for focused electromagnetic heating of limbs and torsos is considered. In contrast to the uniform current excitation, the scheme has two current nulls diametrically opposite to one another. In this case, the circumferential electric field dose not vanish on the axis, which overcomes the principal criticism of the uniform loop. >

Strong magnetic fields near a leaky wave aperture in a lossy medium

The concept that a leaky wave, in a lossy medium, will grow in amplitude in the direction of phase propagation is examined for a finite aperture source. It is shown that local growth is indeed possible if the traveling wave excitation is suitably chosen. Specific calculated results are shown for the magnetic field in a lossy half-space adjacent to the aperture. Enhancements on the order of 20 dB are possible over what one would expect on the basis of classical skin depth theory. >