A DBDCP Antenna With a Helmet-Conformal AMC for Industrial IoT Applications Featuring LHCP and RHCP in the Low and High Bands, Respectively

A wearable dual-band and dual-circularly polarized (DBDCP) antenna using a dodecagonal truncate pyramid-shaped artificial magnetic conductor (AMC) reflector for gain enhancement is proposed in this article. First, a compact deformed quadruple inverted-F antenna (QIFA) with meander-line-shaped radiation patches has been developed as the radiator. Then, to make this QIFA generate different circular polarization (CP) radiation characteristics in two frequency bands, two feeding networks are adopted for realizing left-hand and right-hand CP properties simultaneously. Finally, a novel AMC reflector is employed to improve antenna performance. The presented DBDCP antenna was fabricated to realize left-hand CP (LHCP) in the frequency band of 3.5-4.0 GHz (13.3%) and right-hand CP (RHCP) in 5.4-5.9 GHz (8.8%). Due to installation of the AMC reflector, the gains of the antenna are enhanced by about 3-5.3 dB in the lower CP band. The achieved peak gains are about 11.9 and 10.5 dBic at 3.5 GHz (LHCP) and 5.8 GHz (RHCP), respectively. Meanwhile, the antenna's specific absorption rate (SAR) has been greatly reduced, which meets well the IEEE wearable device standards. It is found that the proposed DBDCP antenna is a promising candidate for the applications of 5G, industrial scientific medical (ISM), WLAN (5.8-GHz), and WiMAX (3.5-GHz) systems in industrial Internet of Things scenarios.