Wearable Antennas: A Review of Materials, Structures, and Innovative Features for Autonomous Communication and Sensing

Abstract

Wearable antennas have gained much attention in recent years due to their attractive features and possibilities in enabling lightweight, flexible, low cost, and portable wireless communication and sensing. Such antennas need to be conformal when used on different parts of the human body, thus need to be implemented using flexible materials and designed in a low profile structure. Ultimately, these antennas need to be capable of operating with minimum degradation in proximity to the human body. Such requirements render the design of wearable antennas challenging, especially when considering aspects such as their size compactness, effects of structural deformation and coupling to the body, and fabrication complexity and accuracy. Despite slight variations in severity according to applications, most of these issues exist in the context of body-worn implementation. This review aims to present different challenges and issues in designing wearable antennas, their material selection, and fabrication techniques. More importantly, recent innovative methods in back radiations reduction techniques, circular polarization (CP) generation methods, dual polarization techniques, and providing additional robustness against environmental effects are first presented. This is followed by a discussion of innovative features and their respective methods in alleviating these issues recently proposed by the scientific community researching in this field. INDEX TERMSWearable devices, Internet of Things (IoT), wearable antennas, flexible, reconfigurable antennas, energy harvesting for wearable devices, specific absorption rate (SAR).

Flexible Antennas: A Review

“…Moreover, the specific absorption rate (SAR) limit has to be considered while designing a wearable/flexible antenna. The SAR limit is regulated for wearable devices, including antennas, which quantifies the amount of EM radiation a human body can safely withstand without any health hazards and is defined as the power absorbed per unit mass of tissue [ 232 ].…”

A Review of Flexible Wearable Antenna Sensors: Design, Fabrication Methods, and Applications

“…Wearable textile antenna sensors are becoming more and more essential in on-body applications in the last decade [ 23 ], due to their ability to detect microstructure deformations and human motions and to monitor and supervise the human health [ 24 , 25 ]. Compared with conventional antenna sensors, textile antenna sensors are able to be integrated on the outfits and they offer key features such as comfort, light weight, and washability.…”

Recent Advances of Wearable Antennas in Materials, Fabrication Methods, Designs, and Their Applications: State-of-the-Art

“…Many review papers like [ 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , 102 , 103 , 104 , 105 , 106 , 107 , 108 , 109 , 110 , 111 , 112 , 113 , 114 , 115 ] discussed wearable antennas thoroughly. There are many new high-performance con...…”