Design of an ultra-wideband reflectarray using transformation optics

Reflector antennas realized by reflectarrays have many attractive features that are unmatched by traditional reflectors. Low-profile planar reflectarrays can be made to have high gain and electronic beam steering. However, they tend to use elements operating near their resonant frequencies for achieving a large phase range, thus limiting their bandwidth significantly. Transformation optics (TO) offers a new way to design tunable reflecting devices while preserving many of the attractive features of a reflectarray antenna. The TO device accomplishes beam collimation by using a 2-D array of sub-wavelength dipoles, which is macroscopically seen as an effective medium, to incur different phase changes of the incident fields. The proposed reflector has a relative gain bandwidth of 150%.