Enhanced Quad-Port MIMO Antenna Isolation With Metamaterial Superstrate

Abstract

This letter demonstrates a wideband four-element multiple-input–multiple-output (MIMO) antenna employing a loaded metamaterial superstrate. The proposed MIMO antenna configuration has four slotted rectangular microstrip antennas arranged on a compact square substrate to attain excellent impedance matching over a wide bandwidth of 41% (3.33–5.04 GHz). The suggested four-element MIMO antenna has a compact whole area of 50 × 50 × 1.6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (0.65 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.65 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.002 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ), where <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the wavelength of free space at 4 GHz. The suggested design with a novel 3 × 3 metamaterial superstrate structure reduces mutual coupling of no less than –23 dB among all ports. The metamaterial superstrate is positioned above MIMO elements at 15 mm (0.2 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) for the purposes of isolation and gain enhancement. Satisfactory parameter values are also determined for the competitive MIMO performance, such as envelope correlation coefficient, diversity gain, channel capacity loss, and total active reflection coefficient. The anticipated design has been fabricated and measured. The comparison of simulation outcomes with the experimental findings is satisfactory.