Single-Layer Quadruple-Frequency Dual-Mode Circularly Polarized All-Textile Wearable Antenna

Abstract

This paper presents a multifunctional wearable antenna that operates in multiple frequency bands, including 2.4, 4.5, 5.8, and 6.4 GHz. The proposed antenna structure is designed for both industrial scientific medical (ISM) and wireless body area network (BAN) frequency bands. The antenna employs metamaterial (MTM) unit cells to enable modes with different radiation patterns, implementing monopole-like (null at broadside) and patch-like patterns for on- and off-body communications. The maximum gain achieved is 7.6 dB at 4.5 GHz, and the antenna also provides circular polarization in the off-body frequency (5.8 GHz) with a minimum 1.13 dB axial ratio (AR). The structure is fed by a microstrip feedline for user convenience, and a full-ground plane is included to protect the human body from backward radiation. To validate the advantages of the proposed design, the antenna was fabricated, and its parameters were measured. The results showed good agreement between simulation and measurement. The effect of antenna bending was also investigated, and the results indicated that the antenna operates acceptably for bending radii up to 60 mm. Additionally, the specific absorption rate (SAR) was investigated, and low values below the standard rates were confirmed.