Francis R. Cooray

Analysing radiation from a cylindrical-rectangular microstrip patch antenna loaded with a superstrate and an air gap, using the electric surface current model

This paper presents an analysis of radiation from a cylindrical-rectangular microstrip patch antenna loaded with a superstrate and an air gap between the substrate and the superstrate, using the full-wave approach and the electric surface current model. Numerical results are presented in the form of normalized radiation patterns for various thicknesses of the air gap and also for superstrates made of lossy dielectric material, to show the effects of these on the radiation from the antenna.

Numerical and experimental studies of a dual-polarized planar connected-array antenna for the Australian Square Kilometer Array Pathfinder

Good agreement with measured radiation patterns of the connected-array antenna have been obtained by use of GEMS, MWS and an efficient CBFM approach that we have developed. The results give confidence in this component of the FPA system-modeling capability.

SCATTERING BY A PERFECT ELECTROMAGNETIC CONDUCTING ELLIPTIC CYLINDER

An exact analytic solution is presented to the problem of scattering of a plane wave from a perfect electromagnetic conducting (PEMC) elliptic cylinder, using the method of separation of variables. The formulation is carried out by expanding the incident as well as the scattered electromagnetic flelds in terms of appropriate angular and radial Mathieu functions and a set of expansion coe-cients. The incident fleld expansion coe-cients are known, but the scattered fleld expansion coe-cients are unknown. Imposing the boundary conditions at the surface of the elliptic cylinder leads to the determination of the unknown expansion coe-cients in closed form. Results are presented as normalized scattering widths for elliptic cylinders of difierent sizes and PEMC admittances, to show the efiects of these on scattering.

Scattering of a Plane Wave by a Homogeneous Anisotropic Elliptic Cylinder

A formal series solution to the problem of scattering of a normally incident plane wave from an infinite homogeneous anisotropic elliptic cylinder is presented. The formulation of the problem is accomplished by assuming that the permittivity and the permeability tensors of the anisotropic material referred to the elliptic cylindrical coordinate axes are mainly biaxial and diagonal, and expanding each field associated with the problem in terms of a series of suitable Mathieu functions and expansion coefficients. The incident field expansion coefficients are known, but those associated with the scattered and transmitted fields are unknown. The unknown expansion coefficients are obtained by imposing appropriate boundary conditions at the surface of the anisotropic cylinder. Numerical results are presented as normalized bistatic and backscattering widths for elliptic cylinders of different sizes and permeabilities to show the effects of the material anisotropy on scattering.

TE scattering by a perfect electromagnetic conducting semi-elliptic-cylindrical boss on a perfectly conducting plane

An exact analytic solution is presented to the problem of scattering of a plane wave by a perfect electromagnetic conducting semi-elliptic-cylindrical boss located on an infinite perfectly conducting ground plane. The problem is formulated by expressing the incident, reflected, as well as the scattered electromagnetic fields in terms of appropriate angular and radial Mathieu functions and three sets of expansion coefficients. The coefficients associated with the incident and reflected field expansions are known, but those associated with the scattered field expansions are unknown. The unknown expansion coefficients can be determined analytically, by imposing appropriate boundary conditions at the surface of the associated perfect electromagnetic conducting elliptic cylinder. Results are presented as normalized scattering widths for semi-elliptic-cylindrical bosses of different sizes and admittances, to show the effects of these on scattering.

Analysis of radiation from two separate axisymmetric horns using the method of moments

A method of moments (MoM) technique is described for analyzing the radiation from two parallel axisymmetric horns whose apertures are non-coplanar. Using the equivalence principle and appropriate boundary conditions, a set of integral equations is obtained with currents on the horn surfaces as the unknowns. These integral equations are solved by the MoM to yield the surface currents. The radiation patterns of the two horns as well as the coupling between them are calculated from these surface currents. Numerical results are presented for a pair of axisymmetric horns.

Analysis of radiation from a horn with a superquadric aperture

This paper presents an analysis of radiation from a horn with a superquadric aperture, modeled using a cascade of superquadric waveguides. Electromagnetic fields within each waveguide are expressed in terms of a set of orthogonal modes derived from polynomial functions based on a Cartesian coordinate system. The scattering matrix at the horn aperture is obtained by calculating the scattering matrix at each of the waveguide junctions using mode matching, and cascading them appropriately. Radiation patterns corresponding to both x- and y-polarizations of the input excitation are then obtained by integrating the aperture field. The computed numerical results are validated by comparing them with the corresponding results obtained from measurements.

Analysis of radiation from two separate circular cylindrical waveguides by the method of moments

A method of moments (MOM) technique is described for analyzing the radiation from two parallel perfectly conducting circular cylindrical waveguides whose apertures may be noncoplanar. By means of an equivalence principle and the appropriate boundary conditions, a set of integral equations is obtained with surface currents as the unknowns. These integral equations are solved by the MOM to yield the surface currents, from which the radiation patterns for the two waveguides are calculated. Numerical results are presented for two uniform waveguides and for two stepped waveguides. To validate the analysis, these results are compared with corresponding results obtained from other numerical methods and also with practical measurements.

Analysing radiation from a superstrate loaded cylindrical–rectangular microstrip patch antenna with a spaced substrate, using the electric surface current model

Radiation from a superstrate loaded cylindrical–rectangular microstrip patch antenna with an air gap between the ground and the substrate is analysed using the full-wave approach and the electric surface current model. Results are presented in the form of normalised radiation patterns and directivity patterns for various thicknesses of the air gap, to show the effects of the air gap on the radiation from the antenna. Both axial and azimuthal current elements are considered.