Design and evaluation of wearable textile antennas backed by AMC for localization application

Abstract

This research focuses on the development of several new compact antennas suitable for localization application in a wearable format. To ensure that these antennas are able to operate with minimal detuning caused when placed on body, they have been designed with three strategies, first is to ensure its size compactness, secondly, a wide bandwidth and finally, to adapt, wherever possible, a full rear ground plane. However, the implementation of miniaturization techniques typically results in gain degradation, whereas the implementation of the full ground plane limits antenna bandwidth. One efficient method to simultaneously overcome both is the use of multiple miniaturization and broadbanding techniques such as slots and artificial magnetic conductor (AMC) plane. This AMC plane is formed using an array of unit cells based on the square patch to operate in single or multiband modes. To enable size compactness and multiband operation, square-shaped ring slots are integrated onto the square unit cells prior to its combined use with antennas. Three new antenna designs are proposed in this dissertation; a dual-band dual-polarized textile antenna with AMC plane (Antenna 1), a wideband textile microstrip-based antenna (Antenna 2(a)) and wideband textile antenna with ring slotted AMC (Antenna 2(b)). Besides differences in topology, these antennas also operated in different frequency modes (dual-band and wideband), and are being designed on different textile materials. Despite being inherently narrowband, the microstrip-based Antenna 2(a) and Antenna 2(b) are designed to be wideband and compact by combining several broadbanding and miniaturization techniques. Antenna 1 obtained a gain of 1.98 dB with a bandwidth of 7.6% at 1.575 GHz. Meanwhile, at 2.45 GHz it showed 1.94 dB of gain with 5.5 % of bandwidth. It also indicated 9 % of axial ratio for circular polarization at 1.575 GHz. Meanwhile, Antenna 2(a) obtained a realized gain and bandwidth of 3.5 dB and 51 %, respectively. Finally, the combination of AMC plane and this wideband planar antenna enhanced the overall bandwidth and decreased the antenna size. These antennas indicated great potential as effective antennas for application in smart wearable localization in indoor and outdoor environments.