Contribution to the Development of Flat Fresnel Reflectors in W Band for New Imaging Applications

This work presents an experimental study in W band about the behavior of a plane Fresnel re∞ector when the feeder changes its position on the surface of a sphere whose centre is the same of the Fresnel plate zones. For this purpose, an experimental system based on seven Fresnel plate zones and two difierent levels has been developed. The center frequency of the re∞ector is 96GHz, the focal length is 100mm and height between levels is 0.78mm. Based on this Fresnel re∞ector, an experimental set up has been developed. The horn antenna feeder is flxed and situated in far fleld and the receiver is also a horn antenna located at the Fresnel focal distance. Both the re∞ector and the receiving antenna have some rotation capability to enable measurements from difierent angles. The experimental results show a good, stable behavior in gain versus the angular position of the feeder. This special property of Fresnel re∞ectors is impossible in parabolic re∞ectors and consequently, Fresnel re∞ectors could be used in new applications as radar imaging, increasing the radar fleld of view or improving the resolution by means of several squint feeders working simultaneously on the same lens or re∞ector. Therefore, the main objective of this paper is to analyze the behavior of this experimental set up for developing new Fresnel re∞ector-based applications.