Wearable Wideband Circularly Polarized Array Antenna for Off-Body Applications

Abstract

A wideband circularlypolarized (CP) wearable antenna for 5 GHz (5.15–5.825 GHz) wireless body area network is presented and analyzed. The emphasis of this work is on the additional resonance generated by the mutual coupling of a 2×2 compact patch array. As the proposed antenna is fed by a sequential-phase feeding network, the resonance can be used to achieve unidirectional radiation with improved CP bandwidth. To alleviate the loading effects of the human body, a modified strip feedline, comprising two pairs of arc-shaped slots cut on the bottom ground, is introduced. Moreover, the adoption of textiles as substrate and conductor provides flexibility and conformability, allowing the antenna to be integrated with garments. The prototype with the dimensions of 40 mm × 40 mm × 4 mm (0.73 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.73 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.07 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) was fabricated. The measured results indicate that a wide impedance bandwidth of 43% (4.25–6.63 GHz), a half-power beamwidth of 60°, and a 3 dB AR bandwidth of 34% (4.71–6.67 GHz) are achieved. Furthermore, the antenna performance is proved to be stable under structural deformation and human body loading. Finally, transmission losses and link budgets are evaluated, enabling the antenna to be a robust solution for off-body communications.