Most of the implementations of modulated metasurface (MTS) antennas consist of planar circular apertures made of sub‐wavelength patches (or slots) printed (or etched) on a grounded dielectric slab and fed at their center by a monopolar source. However, there are alternatives consisting of metal‐only structures. This chapter presents the use of quasi‐optical systems to excite holographic MTS antennas. Regardless of the implementation, this class of antenna is inherently flat and low mass, which renders it of great interest for space, in general, and particularly for CubeSats and SmallSats platforms. The chapter looks into alternative design approaches to the traditional MTS printed on dielectric substrates and other recent developments at NASA's Jet Propulsion Laboratory in collaboration with CNRS and Queen's University. It briefly recalls the design process, focusing on the metal‐only realizations. The chapter also presents in detail the designs of metal‐only MTS.
- Millimetre Wave