A Wideband Low-Profile Reconfigurable Transmitarray Using Magnetoelectric Dipole Elements

Abstract

A wideband 1 bit reconfigurable transmitarray antenna (RTA) with low-profile characteristic is presented. First, a wideband element for the RTA is designed by combining two centrally fed magnetoelectric (ME) dipoles. Two p-i-n diodes are integrated within the element to achieve 1 bit reconfigurable phase states. Next, the folded scheme is adopted to achieve multiple reflections between the feed source and the RTA, and thus, the height-to-diameter ratio (H/D) is reduced to about one-third of that of the conventional transmitarray. A reflective surface with polarization conversion function is designed beneath the RTA around the source, the unit cell of which is a special <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C$ </tex-math></inline-formula> -shaped polarizer operating over a wide frequency band. Finally, a low-profile RTA with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$12 \times \mathbf {12}$ </tex-math></inline-formula> elements is designed, fabricated, and measured. The whole structure has an aperture size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathbf {5}.\mathbf {75} \boldsymbol {\lambda }_{\mathbf {0}}\times \mathbf {5}.\mathbf {75} \boldsymbol {\lambda }_{\mathbf {0}}$ </tex-math></inline-formula> , and H/D is 0.28. Measured results show that the proposed RTA has the beam-scanning capability to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm \mathbf {40}^{\circ }$ </tex-math></inline-formula> in both E- and H-planes over a bandwidth of 32%. The realized gain is up to 19 dBi and the peak aperture efficiency is 20.5%.