Low-Profile High-Gain and Wide-Angle Beam Scanning Phased Transmitarray Antennas

Abstract

Combining the inherent multiple beam capabilities of transmitarray antennas (TAAs) and the flexible fields launched by phased array antennas (PAAs), PAA-fed TAAs are proposed in this paper for high-gain and wide-angle beam scanning in millimeter-wave (MMW) band. After thoroughly analyzing the operating mechanisms of the PAA-fed TAAs, a divisionally multi-focal method is proposed to deploy the TAA elements, which can be better adapted to the PAA feed whereby the scanning performances are improved. Subsequently, two PAA-fed TAAs with feeding distance-to-diameter ratios ( $H/D\text{s}$ ) of mere 0.28 are numerically demonstrated at 39 GHz, wherein both TAAs are composed of the square subwavelength low-pass elements and the cavity-backed bowtie patch antenna is identified as the PAA feed element. Simulated results show that the first design example achieves a conical beam steering over ±30° with a 30.9 dBi peak gain and gain drop below 2.1 dB. The second design can scan across ±50°/±10° along the E/H planes, respectively, together with the gain losses of 3.3 and 1.6 dB from the peak value of 31.1 dBi. Finally, the first design case is fabricated and measured for experimental verification purpose, whose measured results agree reasonably well with the simulated ones.