A 2-Bit Metasurface Design for Millimeter-Wave Beam Scanning

This paper proposes a 2-bit millimeter-wave metasurface unit with ultra-wide-angle stability, where the reflection characteristics are controlled by manipulating two PIN diodes embedded in the unit. The unit's center frequency is 28.5 GHz, with a 2-bit phase operation range spanning 28.25-28.75 GHz. The unit exhibits excellent angular stability, maintaining superior amplitude and phase performance under oblique incidence of plane waves up to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 75^{\circ}$</tex> in the E-plane <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\varphi=90^{\circ})$</tex>. By employing an optimal arrangement method for directive beam metasurfaces, the proposed units were arrayed into a 16-by-16 meta surface. At the center frequency, the meta surface achieved beam scanning of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 65^{\circ}$</tex> in the E-plane <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\varphi=90^{\circ})$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 60^{\circ}$</tex> in the H-plane <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\varphi=0^{\circ})$</tex>, with a peak maximum gain of 24.28 dBi and an aperture efficiency of 23.28%. The -1 dB gain bandwidth covers the range from 28 GHz to 29 GHz.