Evanescent field used to restore high frequncy in far field signal

摘要

An antenna system 60, or a method of its operation, comprises processing a far field RF signal to restore high frequency components by producing an evanescent field which is focused on to a plane 72 where it is detected. The evanescent field is focused on to a detection plane 72 by a negative-refractive-index lens assembly 66 possibly including Pendry slab lenses. The evanescent field may be provided by a metal masking plate 64 with a plurality of apertures arranged in a grid which samples a far field RF signal. The diameter and effective path length of each aperture may be selected to obtain a desired gain profile. An aperture may be filled with dielectric material to adjust the effective path length of the aperture. The planar RF detector 72 may be an array of fractional wavelength antennas. Infinitesimal gaps are used between the elements of the system to avoid attenuation in the RF signal. The detected RF signal may then be subjected to digital signal processing to demodulate the far field RF signal received.