Modelling of a circular Fresnel zone plate lens for electromagnetic wave antenna application

The application of Fresnel lenses is often made to the receiving antennas for television and radio by way of the satellite communication, for the astronomical observation and so on. Their advantage lies in structural simplicity and low cost. A typical Fresnel zone plate lens (FZPL) consists of coaxial conductive ring bands separately placed over the surface of a dielectric plate. For the antenna application a receiving horn is provided at the focal point. In our previous work, the experiment was carried out for this arrangement, where the horn aperture is larger than the wavelength. Comparison was made with the solution of the Kirchhoff's scalar formula with reasonable agreement (Trans EIC Japan 1998; J-81-B-II(8):823-828, Trans EIC Japan 1996; J-79-B-II(11):959-963). The present work is to validate the numerical treatment. The method of moment and the theory of the physical optics are here considered with three-dimensional vectorial formulation. The focal characteristic is obtained not only for the normal incidence but also for the slightly oblique incidence. Copyright (c) 2005 John Wiley & Sons, Ltd.