Flexible and Wearable Dual-Band Differential Extraoral Antenna for eTDS Applications

Abstract

Wearable assistive devices are essential for performance monitoring and inferring the tongue gestures of disabled individuals in medical rehabilitation. In this paper, a flexible and wearable differential extraoral antenna is proposed with dual resonances (915 MHz and 2.4 GHz) in the Industrial, Scientific, and Medical (ISM) band for extraoral tongue drive system (eTDS) applications. The size of the fabricated prototype of the extraoral differential antenna is (0.135 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\bm{\lambda }}}_{\bm{g}} \, \times\, $</tex-math></inline-formula> 0.065 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\bm{\lambda }}}_{\bm{g}} \, \times \, $</tex-math></inline-formula> 0.002 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\bm{\lambda }}}_{\bm{g}}$</tex-math></inline-formula> ). The performance of the differential extraoral antenna is analysed using a realistic human head model. Further, the extraoral antenna is fabricated and experimentally validated its performance in the close vicinity of the artificial head model. The measured impedance bandwidth (≤ −10 dB) and peak gain values are 90 MHz and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ -$</tex-math></inline-formula> 20.00 dBi, respectively, at 0.915 GHz; and 180 MHz and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ -\!$</tex-math></inline-formula> 12.87 dBi, respectively, at 2.4 GHz. The specific absorption rate (SAR) parameter values have also been analyzed for both the resonating frequencies over 1 g and 10 g of mass tissue through simulations. Further, the link budget was theoretically calculated based on these acceptable SAR values. The proposed antenna could communicate effectively by eliminating balun's additional impedance mismatch loss due to direct interfacing. Thus, the proposed extraoral differential antenna can establish an effective communication link for data and power transfer in the eTDS technology-based applications.