Millimeter-Wave Gaussian-Beam Transmitarray Antennas For Quasi-Optical $S$ -Parameter Characterization

This article presents the design and demonstration of Gaussian-beam transmitarray antennas at millimeter-wave frequencies. The main design tradeoffs and theoretical performances are first investigated numerically. Next, two antenna prototypes are designed in ${V}$ -band and fabricated in printed-circuit-board technology. These prototypes are validated experimentally through transmission measurements in face-to-face configuration (Gaussian coupling) and near-field measurements. Experimental results are in good agreement with simulations predicting a Gaussian efficiency better than 90% and an antenna efficiency of 61.2% at 61.5 GHz. Near-field measurements demonstrate a Gaussian field distribution and a nearly planar wavefront in the focal plane at 57-66 GHz. Finally, the Gaussian-beam transmitarrays are demonstrated in a ${V}$ -band quasi-optical vectorial $S$ -parameter measurement setup. Transmitarray unit-cells are characterized in reflection and transmission at 50-70 GHz and experimental results exhibit a very good agreement with simulations.