Semi-Transparent and Conformal Antenna Technology for Millimeter-wave Intelligent Sensing

This paper describes optically semi-transparent and flexible microstrip interconnects and patch antennas at millimeter wave frequencies. They are realized on a 5-mil thick transparent PET film by patterning honeycomb shape metal grids using a standard lithographic process. Dimensions of the employed metal grids were optimized for low insertion loss and >70% optical transmission at 77 GHz to enable integration into non-conventional surfaces for potential automotive radar applications. The fabricated microstrip lines demonstrate low-loss interconnects with <0.35dB/mm loss at 77 GHz and ~73% optical transmission from 390 nm to 700 nm. The fabricated semi-transparent microstrip patch antennas show radiation characteristics comparable to that made of standard solid metal.