Single-Feed Near-Field Excited Quad-Beam Metasurface Antenna

In this letter, we propose the design of a single-feed low-profile digitally coded metasurface antenna for generation of quad-beam radiation. The design procedure involves initial synthesis of the desired reflection phase profile using far-field plane-wave illumination, followed by application of a correction factor which considers presence of near-field excitation source generating spherical waves. The profile of the proposed quad-beam metasurface antenna is significantly minimized using a coax-fed printed dipole as exciter, instead of the high-gain helical or horn antennas placed at a distance for feeding conventional reflectarrays. Furthermore, use of 1-bit coding scheme considerably reduces the design complexity of the metasurface. Full-wave EM simulations based on CST Microwave Studio (CST-MWS) and experimental measurements on fabricated prototype confirm that the dipole-excited metasurface with aperture size <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$11\lambda _{0} \times 11\lambda _{0}$</tex-math></inline-formula> (where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{0}$</tex-math></inline-formula> is the free-space wavelength at 10 GHz) generates four symmetrical beams in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\theta =45^{\circ}$</tex-math></inline-formula> plane with peak gain of 11.7 dBi. The proposed low-profile quad-beam metasurface antenna has potential to be used in future 6G communications as well as X-band radar applications.