In this paper, a compact circularly polarized asymmetric dielectric resonator antenna (DRA) excited by a quarter-wave transformer (QWT) feedline is proposed for ultra-wideband (UWB) applications. The DRA consists of two rectangular ceramic blocks with the same permittivity (ε_DR = 9.8) and an F-shaped metallic strip combined with the partial ground. The proposed antenna is supported first and third-order modes as TE_δ11 and TE_δ13 at 9.1 and 11.28 GHz. The proposed antenna covers ultra-wideband (UWB) range from 6.4 to 12.4 GHz (impedance bandwidth of 63.8 %) with a peak gain of 6.01 dBi at 11.5 GHz. The broad AR bandwidth of the proposed antenna is achieved by the asymmetric structure of DR and the modified ground. The simulated AR bandwidth (≤ 3 dB) of the proposed antenna is 63.8% (6.4 to 12.4 GHz), and the measured AR bandwidth is 2.5% (5.8 to 6.1 GHz) and 43.7% (6.9 to 10.9 GHz). The proposed antenna can be used for C, X band applications.

This paper presents a double negative (DNG) metasurface-based multiple input multiple output (MIMO) antenna with a wideband operation for the sub6-GHz range of 5G communication. The MIMO antenna (called DNG-MIMO antenna) consists of two DNG metasurface antenna elements placed closely on a partialground with a U-shaped slot. The proposed DNG-MIMO antenna has a compact size of 20.5 mm X 40 mm with an operational bandwidth of 1500 MHz (4.9 GHz–6.4 GHz) and a peak gain of 3.49 dB. With a minimal interelement distance (0.18 λ, where λ is operating wavelength), the DNG-MIMO antenna exhibits very highisolation (s12<-25.5 dB) for the entire resonating bandwidth. The proposed DNG-MIMO antenna exhibits good MIMO performance metrics such as envelope correlation coefficient (ECC<0.003), diversity gain (DG = 10 dB), total active reflection coefficient (TARC<-10 dB), and channel capacity loss (CCL<0.3 bits/Hz/Sec). The total efficiency of the DNG-MIMO antenna is more than 80% across the operating bandwidth. Thus, with a miniaturized dimension, good MIMO performance metrics, and wide bandwidth, the proposed metasurface MIMO antenna is ideal for the upcoming 5G communication systems and various IoT applications. For analysing the practical applications of the proposed MIMO antenna, an 8-element DNG-MIMO is connected to an extended ground plane, the results obtained suggest no deterioration in s-parameters, efficiency, ECC and DG is observed.