Laser-Drilled All-Dielectric Huygens’ Transmit-Arrays as 120 GHz Band Beamformers

An all-dielectric Huygens' transmit-array is proposed and experimentally demonstrated in the 120-GHz-band. The proposed transmit-array is fabricated using a high-precision laser-drilling process providing high fabrication precision and accuracy. A non-uniform Huygens' surface is next placed on top of a planar high gain slot-array antenna for far-field beamforming. Full-wave simulations are first used to demonstrate the beamforming capability by generating difference-pattern beams as an example. A uniform transmit-array was then fabricated and characterized to investigate the effect of the transmit-array on the antenna performance, along with showing very low fabrication tolerances and minimal dimensional variation due to the laser drilling process. Next, a phase-gradient transmit-array for beam-tilting is experimentally demonstrated as a practical example of beamforming. The proposed all-dielectric structure is the first Huygens' structure to be demonstrated at these frequency bands, and represents an attractive alternative to conventional metallic Huygens' metasurfaces based on standard printed circuit board (PCB) solutions.