Two-Dimensional Switchable Beam Transmitarray Antenna for mm-Wave Base Stations and Vehicular Networks

This article presents the design of a low-profile, two-dimensional and beam-switching transmitarray antenna for millimetre-wave (26.3-29.3 GHz) applications. The transmitarray panel is designed using two substrate layer polarization rotating phase shift elements. The phase distribution on the transmitarray panel is approximated by 0 and
$\pi $
. The phase shift element dimensions are
$0.22\lambda _{0}$
x
$0.22\lambda _{0}$
x
$0.14\lambda _{0}$
, (
$\lambda _{0}$
corresponds to frequency of 28 GHz). The overall size of the transmitarray panel is
$5.6~\lambda _{0}$
x
$5.6~\lambda _{0}$
with a focus-to-dimension (f/d) ratio of 0.5, which makes the design compact. The panel is fed by a 9-port Yagi array antenna arranged in a
$3\times $
3 configuration. The offset antennas undergo a scanning loss of 1.6 dB with a peak gain of 19.7 dBi in the main beam. The 3-dB beamwidth of 9.8-11.2° is obtained in different radiation beams. The radiation patterns of the offset antennas are tilted ± 15° with respect to the focal antenna, thus giving a radiation coverage of 30°. The antenna can be used in millimetre wave base stations for beam-switching and can also act as a repeater antenna at millimetre wave frequencies in public transport vehicles.