Flexible CPW-Fed antenna for ultra-wideband wearable application

Abstract

This paper introduces a compact, slotted coplanar waveguide (CPW)-fed antenna that exhibits a wide bandwidth (fractional bandwidth >50%) within the ultra-wideband (UWB) range, and is also flexible. The antenna design features hexagonal rings that are cut and slotted on a polydimethylsiloxane (PDMS) substrate to achieve these characteristics. The slotted hexagonal ring radiator is fed by a tapered CPW, positioned centrally on a trapezium-shaped ground plane. The antenna operates effectively over a frequency range of 1.68 to 9.03 GHz, achieving a total impedance bandwidth of 7.35 GHz (S11<−10 dB for 1.68−9.03GHz, VSWR <2). The peak gain across the band is 6.71 dBi. Through various design iterations, the peak gain is observed to be 6.71 dBi at 6.5 GHz and 4.07 dBi at 2.4 GHz. Additionally, the antenna maintains an axial ratio (AR)<3 dB from 1.75 to 1.83 GHz, and a specific absorption rate (SAR) of 1.33 W/kg for 1 g of tissue. The overall dimensions of the antenna are 95×80 mm2.