Miniature Wideband Non-Uniform Metasurface Antenna Using Equivalent Circuit Model

Abstract

A miniaturized wideband non-uniform metasurface antenna is proposed and analyzed using an equivalent circuit model. The nonuniform metasurface consists of an array of rectangular metallic patches separated by varying gaps. The effects of the varying gap widths on the resonant frequencies of the dual-mode non-uniform metasurface antenna are studied using the proposed equivalent circuit model. The resonant frequency of the first TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode decreases with narrowing of either the center or side gaps; the resonant frequency of the antiphase TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> mode is hardly affected by the center gap width but decreases while reducing the side gap width. The miniaturization of the metasurface antenna is therefore achieved by narrowing the side gaps, and the wide bandwidth with good impedance matching is realized by widening the center gap. A proof-of-concept prototype demonstrates a peak gain of 7.2 dBi over a -10 dB reflection coefficient bandwidth of 21.8%, with a miniaturized non-uniform metasurface of 0.46λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.49λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.06λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the center operating wavelength in free space) which achieves 54% size reduction compared with the earlier developed wideband antenna with a uniform metasurface of 0.7λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.7λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.06λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> .