CALCULATING THE RADIATION-PATTERN OF A FRESNEL-ZONE PLATE ANTENNA - ACOMPARISON BETWEEN UTD GTD AND PO

A vectorial far-field analysis of the Fresnel-zone plate antenna (FZPA ) is presented using two different calculation methods. The first meth od, Physical Optics, is based on Kirchhoff's diffraction theory and ho lds for apertures which are large in terms of the wavelength. Because this is not the case for the width of all the radiating rings of the F ZPA, a second method is used which accounts for the influence of the e dges of the rings on the incident field. This method is based on a com bination of the Geometrical Theory of Diffraction and the Uniform Theo ry of Diffraction. Expressions which describe the radiation patterns a re derived using both methods, and the differences and similarities be tween them are examined. The results of this analysis give good insigh t into the influence of the FZPA geometry on its radiation properties.