Design, Parametric Investigation, and Performance Enhancement of a Novel Metamaterial–Inspired AMC‐Backed UWB Antenna for Wearable and IoT Application

ABSTRACT

Internet‐of‐Things (IoT) and wearable devices require compact, wideband, and efficient antennas that can be used in close proximity to the human body. Traditional ultra‐wideband (UWB) antennas are seriously affected by performance degradation in the vicinity of human tissues because of detuning, low gain, and high specific absorption rate (SAR). In order to address these drawbacks, this paper introduces a miniaturized UWB antenna with a metamaterial‐inspired multi‐resonant artificial magnetic conductor (AMC). The antenna is fabricated on an FR4 substrate and optimized through careful parametric analysis in order to attain broadband operation between 3.2 and 9.7 GHz. A novel UWB antenna and AMC unit cell is modeled as an equivalent LC circuit that offers an in‐phase reflection at three resonant frequencies. The UWB antenna, with the support of the AMC, shows a high gain boost of about 3 dB, increasing from 1.9 to 4.7 dB at 5 GHz and 1.5 to 3.5 dB at 8 GHz. At 5 GHz, the standalone antenna is 73.5% radiation efficient, and at 8 GHz, the radiation efficiency is 76.0%. With the addition of the AMC, the efficiency decreases to 65.3% and 75.0% respectively, because of the extra dielectric losses in the AMC substrate, although the realized gain increases by about 3 dB because of increased forward directivity. Multilayer human phantom SAR assessment shows a significant decrease compared with that of standalone antennas, with 1.57 W/kg at 5 GHz and 0.163 W/kg at 8 GHz measured, which meets both FCC and ICNIRP safety limits. The proposed design has been thoroughly compared against the AMC‐based wearable antennas recently reported, which allows the conclusion that the given solution reaches a higher gain‐to‐size ratio and safety level, making it one of the most promising solutions to be implemented in the next‐generation wearable and IoT applications.