Metamaterial-Based Four-Port Polarized MIMO Antenna for SWIPT Applications

This paper presents a low-profile, single-layer wideband metamaterial-inspired linear polarized multiple-input multiple-output antenna array with an integrated rectifier for simultaneous wireless information and power transfer applications. The antenna consists of eight elements fabricated on Rogers 4350 substrate with a defected ground structure, where four ports are dedicated to wireless information transfer and four ports are directly connected to a rectifier for wireless power transfer. The rectifier employs four SMS7630 diodes and is directly matched to the antenna with input impedances of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$34-\mathrm{j}57\Omega$</tex> and rectifier impedance of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$34+\mathrm{j}57\Omega$</tex>, delivering 0.9 V output voltage with 75% efficiency into a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1000 \Omega$</tex> load. The total array occupies <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.599 \times 0.33\lambda$</tex>, operating over 3.2-4.3 GHz, with a peak gain of 5.5 dBi and isolation below -20 dB between all ports. Metamaterial-inspired elements enhance impedance and bandwidth, providing stable polarization. MIMO performance is evaluated via envelope correlation coefficient, diversity gain, and mean effective gain, confirming suitability for SWIPT-enabled sensors, IoT devices, and other low-power wireless systems.