Asoke K. Bhattacharyya

Circular Loop Antenna In Unbounded Chiral Medium: A Moment Method Solution

This paper addresses the problem of a thin loop antenna of arbitrary radius radiating in an infinitely extending chiral medium. The integral equation for the problem has been formulated and solved using Numerical Electromagnetics Code modified accordingly. It is found that with the additional parameter of chirality one can control the radiation characteristics. It is observed that for a typical case of a loop of radius equal to a half wavelength the radiation resistance increases from about 140 ohms to 310 ohms when the chirality parameter changes from 0.0 (achiral) to 0.003. Also, the patterns become more directive with chirality than in the achiral case for the same electrical size of the loop. The current on the loop decays very quickly with large chirality. Some details of the numerical exercise associated with the moment solution in the chiral NEC code are discussed.

Current on a long, thin wire in a chiral medium

The propagation of current on a thin, straight wire in an infinite chiral medium is examined by solution of the integral equation for an infinite wire and also from the moment-method solution for a long wire of finite length. The current on the infinite wire is shown to consist of three components: a discrete mode that decays exponentially and two continuous-spectrum components from branch cuts from the two chiral wavenumbers. The integral equation for a finite wire in the chiral medium is solved by the method of moments using a modified version of the numerical electromagnetics code (NEC). The moment-method solution is shown to be in close agreement with the modal solution for the infinite wire, providing validation for the numerical treatment. >

On the scattering of an obliquely incident plane wave by a biisotropic cylinder

Scattering of an obliquely incident electromagnetic plane wave by an infinitely long, homogeneous, biisotropic cylinder is addressed. The ambient host medium considered is isotropic, homogeneous and dielectric-magnetic. It is observed that the constitutive coupling of the electric and the magnetic fields in the biisotropic material causes the cross-polarization component of the scattered field not to vanish even for the normal incidence case.

Wavenumbers for currents on infinite- and finite-length wires in a chiral medium

An attempt is made to determine the wavenumbers of the current waves excited on wire antennas located in an infinite chiral medium using two complementary approaches. One is an extension of an existing computer model (NEC) (see G.J. Burke and A.J. Poggio, 1981) that permits the modeling of arbitrary wire objects located in an infinite chiral medium. The other involves the development of a solution to an infinitely long cylindrical antenna, also located in an infinite chiral medium. The latter canonical problem is of interest in its own right, and it provides as well a means for achieving mutual validation with the NEC model.<<ETX>>