-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 mm 3 . 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/kg<2W/kg), when worn on human arm. This value is obtained using the safe limit of 2 W/kg, averaged over 10g of tissue, specified by the International Commission of Non Ionization Radiation Protection (ICNIRP). The SAR is reduced by 83.82 % as compare to the conventional antenna (8.16 W/kg>2W/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.

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The manipulation of polarization state of electromagnetic waves is of great importance in many practical applications. In this paper, the reflection characteristics of a thin and dual-band metasurface are examined in the microwave frequency regime. The metasurface consists of a 22 × 22 element array of periodic unit cells. The geometry of the unit cell consists of three layers, including a 45° inclined dipole shape metal patch on top, which is backed by a 1.6 mm thick FR-4 substrate in the middle, and a fully reflective metallic mirror at the bottom. The proposed surface is exposed to horizontally (x) or vertically (y) polarized plane waves and the co and cross polarization reflection coefficients of the reflected waves are investigated experimentally in the 6–26 GHz frequency range. The metasurface is designed to convert incident waves of known polarization state (horizontal or vertical) to orthogonal polarization state (vertical and horizontal) in two distinct frequency bands, i.e. 7.1–8 GHz and 13.3–25.8 GHz. In these two frequency bands the simulated and experimental results are in good agreement. The polarization conversion ratio (PCR) of the surface is greater than 95% in the targeted frequency bands. A detailed parametric analysis of the metasurface is also discussed in this work and it has been estimated that the surface has the additional ability to convert linearly polarized waves to circularly polarized waves at several distinct frequencies. The proposed metasurface can be utilized in sensor applications, stealth technology, electromagnetic measurements, and antennas design.

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. INDEX TERMS BCC, WBAN, SAR, metamaterial, and wearable/textile/flexible antennas I. INTRODUCTIONRecently, Body Centric Wireless Communication (BCWC) has become one of the most important parts of the fourth generation (4G) mobile communication systems. The fifth generation (5G) is an encouraging technology which will not only fulfil the need of a high data rate for mobile phones and similar devices but also enable incorporation with different high added value services [1]. The IEEE 802.15 standardization group has been established to standardize applications intended for on, off, and in-body communication due to the growing interest in antennas and wave propagation for body centric communication systems [2]. BCWC is a type of communication which is used to connect devices which are worn on or in the body, or between the two people in close proximity. It is further divided into three different categories according to the mean of communication, they are on-body, in-body and off-body communication [3][4][5]. On-body communication describes the wireless communication between the body-mou...

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