Phase Gradient Metasurface Radome Offering Beam Angle Translation and Wideband Absorption

A novel metasurface radome design is presented which combines the properties of a rasorber as well as a phase gradient metasurface (PGMS). By replacing the traditional frequency selective surface or lossless layer, in a radar absorber (i.e. a rasorber) with a PGMS, a new structure can be realised which provides dual-functionality in terms of both beam pattern control and wideband absorption. In particular, a 60
$^\circ$
phase gradient metasurface is designed which is composed of six different unit cells (with the same periodicity) while being placed a quarter-wavelength below two lossy (or resistive) layers. By this stack-up configuration, the radome structure supports complimentary beam steering translation whilst providing absorption bands from about 1.3 GHz to 5.5 GHz and 6.1 GHz to beyond 10 GHz. This design, to the best knowledge of the authors, is the first example of a phase gradient metasurface rasorber (PGMSR) and has many interesting applications for future multi-functional radomes. It can also help to reduce the requirements for mechanical steering, antenna beamformers as well as array phase shifting networks.