Millimeter-Wave Low-Profile Metasurface Antenna With Beam Direction Manipulation Enabled by Near-Field Huygens Metasurface

This communication proposes a low-profile metasurface antenna capable of beam direction manipulation that operates within the millimeter-wave frequency spectrum. The design encompasses a nonoffset substrate-integrated waveguide (SIW) slot array antenna and a near-field Huygens metasurface. The SIW slot array antenna functions as a source, providing spherical wave excitation, whereas the near-field Huygens metasurface enables precise tailoring of the phase distribution above the SIW slot array antenna. The Huygens response of the meta-atom and the suppression of the open stopband (OSB) in the nonoffset SIW slot array antenna are comprehensively illustrated. A simulation model that integrates the functionalities of both wave port and Floquet port is introduced to achieve more accurate electromagnetic responses from the near-field Huygens meta-atom; thereby facilitating enhanced control over electromagnetic wave propagation. To validate the aforementioned benefits, three prototype antennas with varying pointing angles were meticulously designed, fabricated, and experimentally evaluated. The results exhibit good concordance between the simulations and measurements across several key parameters, including the reflection coefficient and radiation pattern.