Experimental investigation of flexible eight-port asymmetric fed MIMO antenna with narrow-super-widebandn-s characteristics for future applications including internet of things

Abstract

In this work, an eight-port MIMOn-s antenna with dual-band operation is presented. The proposed work involves several wireless applications with FR1 and FR2 millimeter-wave bands. Also, a need for conformal antenna with capability of reduced SAR can cater the need for applications in flexible electronics. The antenna includes an oval-shaped radiating patch with a circular slot printed on Rogers RT Duroid TM5880 substrate on one plane and rectangular defected-ground-structure on the other side with a dimension of 70.71 × 70.71 mm2. The radiating patch and ground are asymmetric-fed producing measured bandwidth of Band 1 = 3.59–3.85GHz useful for WiMAX application and Band 2 = 8.40–70.0GHz for application in Industry-Scientific-Medical (ISM)-24.0 GHz, Ultra-wideband (UWB)-24.0GHz and millimeter-wave 5G-FR2 bands (n257-n263). The property of the substrate thickness = 0.254mm is utilized for bending angles of 15°, 30°, and 45° ensuring no change in -10.0dB impedance bandwidth making it suitable for flexible-electronics applications. The SARn-s is evaluated with antenna placed on tissue (skin, fat, muscle) model at SAR/frequency and found to be ≤ 1.60 W/Kg at key frequency values in the operating bandwidth of interest corresponding to 0.0331 W/Kg at 3.50GHz, 0.0435 W/Kg at 10.0GHz, 0.0131 W/Kg at 15.0GHz, 0.0209 W/Kg at 24.0GHZ, 0.0171 W/Kg at 26.0GHz, 0.0116 W/Kg at 28.0GHz, 0.00334 W/Kg at 38.0GHz, 0.00336 W/Kg at 39.0GHz, 0.00296 W/Kg at 41.0GHz, 0.00149 W/Kg at 47.0GHz and 0.0851 W/Kg at 60.0GHz. The diversity performance is also evaluated with measured ECCn-s < 0.02, DGn-s > 9.9998dB, TARCn-s < -8.0dB, and CCLn-s < 0.10b/s/Hz. The measured peak-gain varied between 2.965dBi-16.258dBi with maximum peak-gain of 16.13dBi at 60.0GHz including 2-D radiation patterns at WiMAX and other bands. The multi-band flexible-ability and acceptable SARn-s suggest the proposed well suited for WiMAX and future 5G applications in FR2 bands.