All-Textile Enhanced-Bandwidth Polarization-Conversion Antenna Using a Nonuniform Metasurface

An all-textile broadband circularly polarized (CP) antenna assisted by a nonuniform metasurface (MS) is proposed for 5.8 GHz wireless body area networks. The proposed antenna is comprised of a driven radiator of slot antenna and a broadband CP converter of nonuniform MS with 3 × 3 unit-cells. The slot antenna with a hexagonal shape was initially designed for narrow band and linear polarization. A nonuniform MS with a central-notched hexagonal shape is placed on top of the slot antenna, which produces the broadband CP; the MS unit-cell is designed first to convert the incident wave to an orthogonal direction over a broad band and, second, to excite the resonant modes adjacent to the slot antenna mode, resulting in a broad band. Third, because of the proposed nonuniform MS configuration, the smaller unit-cell excites the resonant mode at higher frequency compared to the larger unit-cell at the center, enhancing operating bandwidth compared to the uniform MS. The proposed antenna is measured in free-space and on phantom-head environments to qualify the antenna for wearable applications. The specific absorption rate is also evaluated for safety usage and satisfies US and EU standards.