Low-Cost and Low-Profile Sub-Terahertz Luneburg Lens Beamformer on Polymer

A Luneburg lens is used to excite a leaky-wave antenna (array of slots) in the sub-terahertz (sub-THz) frequency range. The antenna is built on a 140-mu m thick cyclic Olefin copolymer (COC) substrate. The radiating slots (58x24 slots) are etched on the polymer by a photolithographic process, for which the gold (Au) layers are first deposited by evaporation on the COC and, then, patterned by chemical etching. No metalized vias or drilling are applied to the substrate. The full system is fed by a standard WR03 waveguide, and it has been fabricated and tested. Experimental results show an input reflection coefficient better than -7 dB over a 25% fractional bandwidth, spanning from 220 to 290 GHz. The radiated beam can be steered in elevation from -80 degrees to -20 degrees over the same band. The antenna efficiency is estimated to be 20% at the center frequency (260 GHz). This solution provides a simple alternative for low-cost and low-profile beam-scanning antennas in the sub-THz range.