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This paper presents a triple-band open-ring high-gain high-efficiency antenna for 2.45/3.0/3.45 GHz wearable applications. The proposed antenna operates at 2.45 GHz for Industrial, Specific, and Medical (ISM) applications, 3.0 GHz for military applications, and 3.45 GHz for Worldwide Interoperability for Microwave Access (WiMAX) applications. The proposed triple-band antenna has excellent features for off-body communication, which has directional radiation pattern, high gain, high efficiency, low-specific absorption rate (SAR), and comfortability for wearers. In order to attain these features, the antenna structure consists of two substrates, a rigid substrate and a textile substrate. Two open-ring radiators and a 1 by 2 power divider feeding network are printed on a low-loss rigid substrate. In addition, a square conductive textile is adhered on the backside of the textile substrate. The open-ring radiator generates triple-band at 2.45, 3.0, and 3.45 GHz, in which the inner open-ring excites two resonant modes at high frequencies of 3.0 and 3.45 GHz. The outer open-ring excites a single resonant mode at a low frequency of 2.45 GHz. The outer annular ring is shorted to the ground plane by a shorting pin to miniaturize the antenna size and additionally maintain antenna stability. The conductive textile works as a full-ground plane or protective shield to reduce the electromagnetic waves toward the human body. Therefore, the SARs are significantly minimized. The compatibility of the proposed antenna for off-body communication is verified by measuring the antenna performance in free-space and on phantom/human bodies. The simulated and measured results show very good agreement. |
