Zeroth-Mode Metasurface-Based Miniaturized Antenna With Tri-Band and Tri-Polarization Characteristics for WBAN Applications

This paper investigates a novel miniaturized antenna with tri-band and tri-polarization characteristics for wireless body area network (WBAN) applications. The antenna covers the 2.4–2.485 GHz band, the 3.4–3.6 GHz band, and the 5.725–5.875 GHz band with linear polarization, left-hand circular polarization, and right-hand circular polarization, respectively. In the first band, it produces omnidirectional radiations for establishing device-to-device (DTD) communications on the same human body. In the other two bands, the antenna produces directional radiation for establishing DTD communication between two different bodies. Miniaturization is achieved by investigating the existence of the 0th–mode at 2.45 GHz on a pin-free unit-cell by configuring it with stacked metallic patches. Following that, the miniaturized unit-cell is configured into a metasurface by controlling the dispersion characteristic to support the +1st–mode at 3.5 GHz and the +2nd–mode at 5.8 GHz. Then the metasurface is integrated beneath an unbalanced coplanar waveguide ground (UCPWG)-based monopole patch structure (MPS) to achieve triband and tri-polarization characteristics. The UCPWG enables the feed line as an independent radiator at 2.45 GHz that generates the first-band characteristics and the printed patch at 3.5 GHz that generates the second-band characteristics. Additionally, the MPS contains truncations on the printed patch that controls the third-band characteristics. The antenna is also characterized using a human-phantom model, and the SAR is evaluated to confirm the safe use of the antenna on humans. To validate the simulation results, an antenna prototype is fabricated and measured, which shows excellent matching with each other.