Polarization Reconfigurable Planar Inverted-F Antenna for Implantable Telemetry Applications

Xian-Tao Yang,Hang Wong,Jun Xiang

doi:10.1109/access.2019.2941388

Abstract

A polarization reconfigurable implantable planar inverted-F antenna (PIFA), operating at 2.45–GHz ISM band, is introduced for monitoring and biotelemetry purposes. The proposed implantable antenna featuring with the reconfigurability of two polarizations is effective to overcome the polarization mismatch and multi-path reflection in an indoor environment. By using two groups of PIN diodes as radio frequency (RF) switches along <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$x$ </tex-math></inline-formula> -direction and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$y$ </tex-math></inline-formula> -direction respectively, two orthogonal linear polarizations can be switched to avoid communication link failure. The proposed antenna is based on a planar inverted-F antenna structure and the implantable environment of human body to develop. The antenna exhibits a good stability of an impedance bandwidth with the reflection coefficient ≤−10 dB in the environment of a human phantom. The simulated results in simple muscle-layer phantom, multi-layer phantom and 3D realistic human voxel model demonstrates the good robustness of the proposed antenna in the complex implantable environment. An in-vitro test was carried out in body tissue simulant liquid to validate our proposed design. A sleeve balun was fabricated and incorporated into the semirigid coax cable in order to eliminate the unwanted effect of the long cable during the measurement. The experimental results agree with simulation and show an overlapped impedance bandwidth of 9.1% from 2.3 GHz to 2.52 GHz in different reconfigurable states. The radiation performances, evaluation of Specific Absorption Rate (SAR), and link characteristics in different propagation scenarios are also discussed. This proposed antenna technology is suitable for implantable telemetry applications.

Highlights

With the growing concern of human health and the advancement in supporting technology, wireless body area network (WBAN) is drawn much attentions by the industry in the last decade
Other implantable medical devices (IMDs) like intracranial pressure monitoring devices [3], neural recording systems [4], a retinal prosthesis [5] can be applied to such scenario, where the implantable antennas play an important role in the wireless communication link
It aims to solve the issue of polarization mismatching in complex indoor environment and focus on the implantable antenna design

Summary

Introduction

With the growing concern of human health and the advancement in supporting technology, wireless body area network (WBAN) is drawn much attentions by the industry in the last decade. Due to multi-path reflections in the indoor environment between the implantable antenna and the external receiver, polarization mismatch may occur which cannot guarantee a robust communication link for biomedical telemetry.

Results

Conclusion