Low Profile High Gain Multiband Flexible MIMO Leaky Wave Antenna for Wearable 5G Applications

A wearable textile antenna, designed to be multiband, low-profile, high-gain, and with a low specific absorption rate (SAR), utilizes circular polarization (CP). The antenna is built on two substrates: fleece (ε<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</inf> = 1.04, h = 0.5 mm) and Rogers RO4535 (ε<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</inf> = 3.66, h = 0.125 mm). Its structure includes a staircase-shaped patch fed through curved lines to improve bandwidth (BW) and reduce size. Additionally, a semiring is incorporated to steer the waves, and two elliptical Split Ring Resonators (ESRR) are placed on the first layer to enhance BW and isolation further. On the reverse side of the first layer, 24 ESRR arrays and a full ground plane on the second layer optimize directive gain, improve radiation efficiency, and lower the SAR value. This antenna operates across various 5G and sub-6GHz communication bands, including 3.75-4.1 GHz, 19-21 GHz, 23.8-30 GHz, and 5.2-6.9 GHz. It achieves a maximum directive gain of 8.76 dBi, maintains acceptable SAR values for both standards, and measures 16 × 14 mm² in total size. The antenna demonstrates strong agreement between simulation and measurement results, offering high diversity for multiinput-multi-output (MIMO) communication systems.