Wearable antennas are the vital components for Body Centric Communication (BCC). These antennas have recently gained the attention of researchers and have received a great deal of popularity due to their attractive characteristics and opportunities. They are fundamental in the Wireless Body Area Networks (WBANs) for health care, military, sports, and identification purposes. Compared to traditional antennas, these antennas work in close proximity to the human body, so their performance in terms of return loss, gain, directivity, bandwidth, radiation pattern, efficiency, and Specific Absorption Rate (SAR) is influenced by the coupling and absorption of the human body tissues. Additionally, in the design of these antennas, size, power consumption, and speed can also play a paramount role. In most cases, these antennas are integrated into the clothes, or in some cases, they may be fixed over the skin of the users. When these characteristics are considered, the design of wearable antennas becomes challenging, particularly when textile materials are examined, high conductivity materials are used during the manufacturing process, and various deformation scenarios have an impact on the design’s performance. To enhance the overall performance of the wearable antennas and to reduce the backward radiation towards the human body, metamaterial surfaces are introduced that provide a high degree of isolation from the human body and significantly reduce the SAR. This paper discusses the state-of-the-art wearable/textile/flexible antennas integrated with metamaterial structures composed of wearable/flexible substrate materials, with a focus on single and dual band antenna designs. The paper also reviews the critical design issues, various fabrication techniques, and other factors that need to be considered in the design of wearable/textile/flexible antennas. All the designs presented in this work are of the recent developments in wearable technology.

This paper presents a design of multiple input multiple output (MIMO) antenna array for 5G millimeter-wave (mm-wave) communication systems. The proposed MIMO configuration consists of a two antenna arrays combination. Each antenna array consists of four elements which are arranged in an even manner, while two arrays are then assembled with a 90-degree shift with respect to each other. The substrate used is a 0.254 mm thick Rogers RT5880 with a dielectric constant of 2.2 and loss tangent of 0.0009, correspondingly. The proposed MIMO antenna array covers the 37 GHz frequency band, dedicated for 5G millimeter-wave communication applications. The proposed antenna element yields a gain of 6.84 dB, which is enhanced up to 12.8 dB by adopting a four elements array configuration. The proposed MIMO antenna array performance metrics, such as envelope correlation coefficient (ECC) and diversity gain (DG), are observed, which are found to be under the standard threshold. More than 85% of the radiation efficiency of the proposed MIMO antenna array is observed to be within the desired operating frequency band. All the proposed designs are simulated in computer simulation technology (CST) software. Furthermore, the measurements are carried out for the proposed MIMO antenna array, where a good agreement with simulated results is observed. Thus, the proposed design can be a potential candidate for 5G millimeter-wave communication systems.

In this study, a biotelemetry device for scalp implantation is proposed with an ultra-miniaturized and simple-structured implantable antenna that exhibits dual-band characteristics in the industrial, scientific, and medical bands (915 MHz and 2.45 GHz). The proposed system incorporates two batteries and microelectronic components in a total volume of 434.72 mm3. The recommended antenna has a reduced volume of 9.8 mm3 (7 mm × 7 mm × 0.2 mm), which is the smallest antenna presented so far. In homogeneous and heterogeneous environments, the designed antenna system has peak gain values of -28.04 and -28.94 dBi, respectively, at 915 MHz, and -23.01 and -23.06 dBi, respectively, at 2.45 GHz. For validation, the prototype of the antenna and corresponding system are immersed in a 3D head phantom (saline solution), and the measured results are found in close agreement with the simulation results. Additionally, the data communication range is analyzed through a link budget calculation at several data rates and an input power of -16 dBm. The radiation of the antenna system in the two principal planes (E and H) are similar to being omni-directional and directed away from the anatomical human body model as mandatory for the telemetry applications. Hence, the proposed antenna system can be employed in scalp implantation, especially for intracranial pressure monitoring.

This is an Open-Access article published by The Korean Institute of Electrical Engineers distributed under the terms of the Creative Commons Attribution Non-Commercial 3.0 Unported License (CC BY-NC). Full details of this licence are available at: http://creativecommons.org/\ud licenses/by-nc/3.0/This paper presents design and specific absorption rate analysis of a 2.4 GHz wearable patch antenna on a conventional and electromagnetic bandgap (EBG) ground planes, under normal and bent conditions. Wearable materials are used in the design of the antenna and EBG surfaces. A woven fabric (Zelt) is used as a conductive material and a 3 mm thicker Wash Cotton is used as a substrate. The dielectric constant and tangent loss of the substrate are 1.51 and 0.02 respectively. The volume of the proposed antenna is 113×96.4×3 mm3. The metamaterial surface is used as a high impedance surface which shields the body from the hazards of electromagnetic radiations to reduce the Specific Absorption Rate (SAR). For on-body analysis a three layer model (containing skin, fats and muscles) of human arm is used. Antenna employing the EBG ground plane gives safe value of SAR (i.e. 1.77W/kg2W/kg). The efficiency of the EBG based antenna is improved from 52 to 74%, relative to the conventional counterpart. The proposed antenna can be used in wearable electronics and smart clothing

Design and analysis of a dual-band polarization converting metasurface is presented in this paper. The proposed converter, which consists of two square split ring resonators (SRRs), exhibits peak resonances at frequencies of 5.6, 7.3, 8.8, 15.1, 15.9 GHz. The surface behaves as a polarization converter for linearly polarized incident waves in two frequency ranges, i.e., 5.49.0 GHz with a polarization conversion ratio (PCR) 93%, and 14.616.1 GHz with a PCR 99%). The size and thickness of the unit cell are, respectively, 0.126o and 0.057o, where o is the largest wavelength (corresponding to the lower frequency). The mechanism of polarization conversion is studied by examining the surface currents for all the resonance frequencies. Both simulated and experimental results reveals that the polarization converter can be utilized in C-, X- and Ku-band applications.