Metal-only Reflecting Luneburg Lens Design for Sub-THz Applications

This paper presents a metasurface (MTS) beam-former based on Reflecting Luneburg Lenses (RLLs) operating in the sub-THz range. RLLs consist of two circular parallel plate waveguides (PPWs) vertically stacked. The bottom wall of the lower PPW is loaded with a MTS with an axially symmetric modulation. The wave launched by a primary feed in the bottom PPW is collimated in the top one, so that a plane wave is identically generated for any azimuthal position of the source. The proposed solution uses a bed of nails, well-suited to fabrication by Si micromachining, to implement the RLL refractive index profile. Simulation results yield a 30% -3dB directivity bandwidth around the center frequency (280 GHz). This device can be used as a beam-former for multi-beam antennas for Earth observation or for front- and back-hauling in beyond 5G wireless.