TDF antenna for multisatellite reception using 3D Fresnel principle and multilayer structure

The Telediffusion de France (TDF) solution for multisatellite reception is to develop an antenna whose concept is based on diffraction theory. The first step concerns low-cost TVRO (TV receive only) for DBS (direct broadcast satellite). Then, a more sophisticated antenna could be developed for professional use (cable head-end). A parabolic Fresnel zone antenna has been designed to provide two symmetrical focal points by diffraction with spacing of approximately 40/spl deg/. Consequently, a fixed antenna is able to receive simultaneously incident plane waves with a large incidence angle over a range of some 60/spl deg/. The surface of a conventional parabolic antenna is modified by a set of concentric metal rings with an elliptical shape to provide this scanning effect. A preliminary theoretical analysis and practical experiments have confirmed the multisatellite design of the half-wavelength correction.<<ETX>>