D-Band Demonstration of Quasi-Optical and Analog Beam Reconfiguration Using Phased Array and Lens for 6G Applications

In this paper, a hybrid quasi-optic and analogue beamforming approach is presented, involving an elliptical lens with an active focal plane array at D-band (110-170 GHz). Beamwidth reconfigurability and steering in two planes with enhanced performance are demonstrated. The quasi-optic technique minimizes the beam squint over frequency. Analogue phase shift in the focal plane array is used to increase the lens steering range. A prototype including two 4-channel D-band transceivers with on-chip antennas has been built as demonstrator. The resulting active focal plane array consists of 2x4 antenna elements, which are tuned in amplitude and phase to reconfigure the beam. The advantages of using a resonant leaky-wave cavity combined with a coherent array of feeds are discussed and quantified. Radiation pattern measurements performed with the calibrated active antenna validate the beam reconfiguration concept in two planes at 140 GHz. A steering loss reduction ranging from 2 to 4.5 dB is achieved in the whole D-band at 22° scan angle by applying beam steering in the feed radiation.