Zeroth-Order Mode and Anisotropic Behavior-Based Via-Free Metasurface-Inspired Miniaturized Dual-Band Dual-Polarized Wearable Antenna With High Data Rate and Wider Coverage

Abstract

This article proposes a novel miniaturized dual-band dual-polarized antenna of size $5\times 5\times 0.75~{\text {mm}}^{3}$ with a high data rate and wider coverage for wireless body area network (WBAN) applications. In the lower band, it produces omnidirectional radiation with $y$ -polarization for establishing on-body communication, and in the higher band, it produces directional radiation with right-hand circular polarizations (RHCPs) for establishing off-body communications. To achieve the behavior, an anisotropic-structure-based double-layer unit cell (ADLUC) is investigated by controlling the dispersion characteristic and reflection phase characteristics (RPCs). The dispersion characteristic indicates a 0th-mode of existence at 27 GHz and +1st-mode of existence at 40 GHz, whereas the RPCs indicate a $y$ -polarized reflection phase at 27 GHz and a constant phase difference of −180° between the $y$ -polarized and $x$ -polarized reflection phases through a wide range of frequency of 36–44 GHz. When these behavior-based ADLUCs are integrated into a metasurface and excited using RHCP waves coming from an unbalanced coplanar waveguide ground (UCPWG)-fed straight radiating array, a resonance of 25.82–31 and 34.2–42.82 GHz with an axial ratio (AR) bandwidth of 8 GHz is achieved. The straight radiators in the array configurations are arranged in an up-and-down configuration that contributes to dual-beam characteristics. The antenna’s performances are also characterized by a human body model showing low specific absorption rates (SARs) of 0.9 W/kg at 28 GHz and 0.03 W/kg at 39 GHz. A fabricated prototype is carried out that shows excellent matching with simulation results.