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In this paper, a triple-band dual-sense circularly polarized (CP) hybrid dielectric resonator antenna is proposed. A modified hexagonal dielectric resonator (DR) is top-loaded with a square microstrip ring (SMR). A vertical-tapered-strip connected to a 50-Ω microstrip line is used to excite the proposed antenna. It is found that the lower and central CP bands correspond to left-handed circular polarization and are produced by the TM11 and TE111 modes of the SMR and modified hexagonal DR, respectively. The upper CP band is formed by the combination of the quasi-TM21 mode of the SMR and quasi-TE111 mode of the DR that exhibits right-handed circular polarization. The measurement results of the fabricated prototype show triple-band response for |S11|< −10 dB with impedance bandwidths (IBWs) of 17.4% (1.75–2.03 GHz), 28.13% (2.23–2.96 GHz), and 2.97% (3.65–3.76 GHz) in the lower, central, and upper bands, respectively. The measured 3 dB axial ratio bandwidths lying within −10 dB IBWs are 3.69% (1.86–1.93 GHz), 5.46% (2.67–2.82 GHz), and 2.15% (3.68–3.76 GHz) along with the peak gains of 5 dBic, 5.28 dBic, and 2.36 dBic in the lower, central, and upper bands, respectively.

In this paper, a new dual-band circularly polarized (CP) dielectric resonator antenna for WLAN and WiMAX applications is proposed. The dielectric resonator has an asymmetric Y-shaped geometry. By properly selecting the length of the arms, the pairs of fundamental (TE 111 ) and second-order (TE 211 ) are excited separately at the design frequencies to radiate the CP wave. The measurement shows that the fabricated antenna exhibits a wide impedance bandwidth for |S 11 | < −10 dB of 62.07% (2.2–4.18 GHz). The far-field measurements in the broadside direction demonstrated a dual-band CP response with 3 dB ARBWs of 4.92%(2.38–2.5 GHz) at the lower and 12.64% (3.26–3.70 GHz) at the upper band. The measured CP bands cover the entire frequency range of WLAN (2.401–2.495 GHz) and WiMAX (3.4–3.69 GHz) at the lower and upper bands, respectively.

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...