Circular polarization selective surface made of resonant spirals

Abstract

A Circular Polarization Selective Surface (CPSS) for circular polarized electromagnetic waves is formed from a number of resonating elements arranged in a plane. This type of surface may be used in a wide range of reflector antennas. Each resonating element is formed from a number of electrically conductive segments connected end-to-end one to the other with each segment having a predetermined length and having a total approximate length of 1.lambda.. A central segment having a length about 1/4.lambda. determines the resonant frequency for the element. This central segment extends parallel to the z-axis of a right-hand set of three mutually perpendicular axes x, y and z wherein the circular polarized electromagnetic wave is directed along the z-axis. A second segment is connected to one end of the central segment and extends parallel to the x-axis with a third segment being connected to the other end of the central segment extending parallel to the y-axis. Shorter segments connected to outer ends of the second and third segments extend parallel to this z-axis and toward each other so that a free end of one shorter segment can be connected to a free end of a shorter segment of an adjacent resonating element forming a spiral which can be mechanically supported at its outer ends. This eliminates the need for having support structures in the active area of the surface.