The elliptical Fresnel-zone plate antenna

The growing number of direct broadcast satellites (DBS) asks for simple, low-cost home receiving systems. The use of the Fresnel-zone plate antenna (FZPA), which is related to the optical lens, is also promising for this application. The aperture of the FZPA is plane and its structure is determined by the well-known Fresnel ellipsoids. In a practical situation the Fresnel zones are often attached to a window of a building. Then, the line between satellite and receiver is not perpendicular to the aperture and, consequently, the rings become elliptical. In the paper this elliptical FZPA is analysed for both linear and circular polarization. The latter is included because most of the future DBS will transmit circularly polarized waves. For this particular polarization a squint of the antenna beam is expected, because of the asymmetric antenna geometry. Kirchhoff´s diffraction theory is used to calculate the mainlobe, the first sidelobe and the corresponding crosspolar lobes of elliptical FZPAs with absorbing rings