Additively Manufactured Wideband Low-Profile Bidirectional 2-D Beam-Scanning Antenna Using Double Folded Transmitarrays with Curved Polarizers

This article presents a wideband low-profile bidirectional 2-D beam-scanning antenna for millimeter-wave applications. It achieves independently controlled bidirectional beams by two orthogonally mirrored folded transmitarrays (TAs) overlapping in space, significantly reducing the antenna profile. The folded TA consists of a feed source, a curved polarizer, and a receive-transmit (R-T) array. The feed source is realized by an all-metal wideband miniaturized magnetoelectric (ME) dipole based on the metal 3-D-printing technique. The curved metal grating acts as a polarizer, which achieves reflection and transmission for ${y}$ -polarized and ${x}$ -polarized waves, respectively. Using the additively manufactured electronics (AME) technique, the R-T array element is realized by two wideband tightly coupled bow-tie dipole antennas connected by a pair of differential microstrip-line phase shifters with true-time delay and continuous 360° tuning range. Finally, 2-D beam scanning with constant beam direction across the operation band is achieved by adjusting the polarizer along the ${x}$ - and ${y}$ -directions. The height diameter ratio ( ${H}/{D}$ ) is 0.5, while the measured 2-D bidirectional beam scanning range covers ±10° in both the E- and H-planes within 27-39 GHz, with a maximum scan loss of 1.9 dB. The measured peak gain is 27.1 dBi, and the maximum aperture efficiency is 53.4%. The measured 1- and 3-dB overlapped gain bandwidths for 0° and 180° beams are 30-36.2 (18.7%) and 27-40 GHz (38.8%), respectively.