ABSTRACT
This chapter focuses on the development of various new compact wearable antennas suitable for communications, Internet of things (IOT), medical systems and localization applications. To ensure that these antennas are able to operate with minimal detuning caused by the human body, they have been designed based on three principles: the antennas are, first of all, compact; second, they need to have a wide bandwidth; and finally, wherever possible, a full rear ground plane or metamaterial-based backing has been included. However, implementation of miniaturization techniques typically results in gain degradation, whereas the implementation of the full ground plane typically limits antenna bandwidth. One efficient method to simultaneously overcome both limitations is the use of multiple miniaturization and broadbanding techniques, such as slots and metamaterial-based backing planes. Metamaterial-based backing planes, such as the artificial magnetic conductor (AMC) plane, are formed by using an array of unit cells, for example, based on a square patch, to operate in single or multiband modal regime. To enable size compactness and multiband operation, slots can be integrated onto the conventional square unit cell prior to its combined use with the antenna. Several new antenna designs will be explored in this chapter: dual- or multiband dual-polarized textile antennas with AMC plane, wideband textile microstrip-based antennas and miniaturized wideband textile antennas with multiband metamaterial-based backing. Besides differences in topology, these antennas also operate with different frequency characteristics (dual-band or wideband) when designed on different textile materials. Despite being inherently narrowband, microstrip-based antennas can be designed to be wideband and compact by combining several broadbanding and miniaturization techniques. The complexity of designing such a structure and the performance level are first explained. This is then followed by the various types of antennas integrated with AMC planes, and their levels of enhancements in terms of the overall bandwidth and antenna size compactness. Performance evaluations of these antennas in proximity to the human body also indicated compliant levels of Specific Absorption Rate. All discussed antennas can be potentially used in indoor and outdoor environments for IOT and medical applications.
