The recent advancement in the wireless technology has led to the advent of wearable antennas. These antennas are utilized for Wireless Body Area Networks (WBANs) purposes such as healthcare, military sportive activities and identification systems. Compared to conventional antennas, wearable antennas operate in an environment which is in highly near proximity to the curved human body. Therefore, the wearable /flexible antenna performance parameters, including reflection coefficient, bandwidth, directivity, gain, radiation characteristic, Specific Absorption Rate (SAR), and efficiency are anticipated to be influenced by the coupling and absorption by the human body tissues. In addition, an electromagnetic bandgap structure is introduced in the wearable /flexible antenna designs to enable and give a high degree of isolation from the human body which also decreases the SAR dramatically. This paper reviews the stateof-the-art wearable/flexible antennas integrated with the electromagnetic band-gap structure on flexible materials concentrating on single and dual-band designs. Besides, it also highlights the challenges and considerations for an appropriate wearable/flexible antenna. INDEX TERMS Wearable/flexible antennas, EBG, AMC, metamaterials, metasurface, textile/fabric antennas, WBAN applications, ISM, SAR. I. INTRODUCTION Wearable devices are critical in the ICT field for on-body applications and the deployment of the Internet of Things and Wireless Sensor Networks. They must be low-powered, small, and capable of connecting to a hub or gateway device to access the internet or the cloud. The goal of these devices is to enhance the quality of life by improving the functionality of clothing by combining fabrics and electronics. They are continually showing a vision of the future since they are The associate editor coordinating the review of this manuscript and approving it for publication was Chow-Yen-Desmond Sim. going to be an essential part of daily clothing and serve as an intelligent personal assistant [1]-[3]. With the tremendous growth of wearable devices, academics, engineers, and researchers are concentrating on the investigation of ''Wireless Body Area Networks'' (WBAN) that link different electronic devices on the human body. The WBANs have a variety of applications in our daily lives. In the healthcare arena, they are applied to monitor a patient's serious health condition, such as a glucose monitoring system, capsule endoscopy, and blood pressure. Furthermore, they can be utilized in entertainment, military, business, and rescue operations, as well as incorporated into helmets, raincoats, shoes, jackets in emergency and rescue

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This work provides design and analysis of a beam steering reflectarray antenna, designed at 26 GHz, based on the mechanical rotation of the array. Unit cells based on circular ring elements are designed, and scattering parameter measurements have been carried out for obtaining progressive phase distribution. The unit cell measurements demonstrated a maximum reflection loss of 4 dB with a total phase range of almost 360 • . Symmetricity of the array and the resonant elements has been exposed to steer the main beam by tilting the reflectarray at different angles. A beam steering range of more than ±60 • has been demonstrated by varying the tilt angle from +30 • to −30 • . The designed 20×20 element array provided a maximum gain of 26.47 dB at 0 • which reduced to 19.8 dB at 61.9 • in the elevation plane. On the other hand, the reflectarray antenna demonstrated a maximum bandwidth of 13.1% with a minimum side lobe level of −25.9 dB.