Radiation-enhancing reflector

We show that it is possible to realize a passive planar reflector whose reflectivity (close to the resonant frequency of the reflector structure) is larger than unity. This reflector is strongly coupled to evanescent fields of external sources and most effectively extracts power from them. Next, this power can be launched into far zone if the surface of the reflector is perturbed by some small passive scatterers. Used as electrically large reflector antennas, such planar surfaces show superdirectivity properties (the effective area is larger than the geometrical area of the reflector) while there is no need for careful subwavelength control over the amplitude and phase of the surface currents.