Full-space metasurface at millimeter-wave frequencies

Conventional metasurfaces provide control over the electromagnetic waves in a single working frequency operating either in transmission or reflection. Full-Space Metasurfaces (FSM) are an extension that allows operation at two different frequencies with independent functionalities in transmission and reflection. This paper presents a gradient index FSM device based on a 3-layered unit cell where the phase modulation is implemented following the Pancharatman-Berry (PB) principle. The device is designed to operate at millimeter waves, with the lowest frequency operating in reflection and the highest one in transmission. To check the structure performance, a metasurface was designed to provide beam steering in reflection at 49.4 GHz and an amplitude image hologram in transmission at 104 GHz.