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The objective of this article is to describe a compact 4-port MIMO planar antenna with a high axial ratio bandwidth (ARBW) that is suitable for usage in 5G applications that operate at frequencies lower than 6 GHz. The optimized dimension of the proposed antenna element is 37 × 30 × 0.8 mm3 and FR-4 substrate has been used as a dielectric material with relative permittivity of 4.4, and a height of 1.6 mm. The proposed antenna has an impedance bandwidth (− 10 dB) in the range of 3.3–4.3 GHz (Simulated)/3.4–4.7 GHz (measured), with a 3-dB ARBW of 3.0–4.4 GHz (simulated)/3.0–4.0 GHz (measured) respectively. The configuration that has been suggested for a MIMO antenna consists of a single entity that has a radiating element in the shape of a T and a ground plane in the shape of a C, both of which are co-planar. The findings of the simulation are then validated by the measurement results which are carried out by using the VNA55071C Vector network analyzer. The suggested module has the potential to serve as a MIMO antenna for impending fifth-generation wireless applications as it achieves an isolation level of better than 15 dB, has an envelope correlation coefficient (ECC) of less than 0.005, and has a diversity gain (dB) > 9.95 dB. [ABSTRACT FROM AUTHOR]

In this communication, a planar dual port multiple input multiple output antenna of size 1.2λ0 × 0.6λ0 × 0.008λ0 with LHCP/RHCP features is reported for the fifth-generation new radio n77/n78 sub-6 GHz wireless applications band. The single unit of the proposed design consists of a modified L-shape rectangular radiator with Z-shape slot loaded DGS. The defected ground structure is optimized through machine learning algorithms to achieve the maximum ARBW (output) by Right Shifting (RS) and left shifting (LS) the DGS and obtaining input features. The performance metric for ANN with ADAM optimizer was found to be optimal with MSE and R2 of 0.99 and 0.82, respectively. ANNs can leverage gradient information to guide the optimization process. This enables faster convergence towards optimal solutions compared to popular GAs and PSO, which are often gradient-free optimization methods. The MIMO configuration is achieved by creating a mirror image of the single unit about the x-axis. The salient features of the proposed design are (a) Impedance bandwidth (IBW) of 3.0–4.2 GHz covering the n77/n78 band, (b) 3-dB axial ratio bandwidth (ARBW) of the 2.6–3.9 GHz (c) Port-1 is generating RHCP while Port-2 is generating LHCP, results in polarization diversity. Different diversity performance parameters (ECC < 0.005, DG ~ 9.99 dB, and MEG < 3 dB) are in the optimum range confirming the proposed configuration as a suitable design for a MIMO radiator. [ABSTRACT FROM AUTHOR]

In this communication, a graphene-based radiator is designed and analyzed at THz frequency. A tilted dumbbell-shaped aperture is loaded on a graphene patch for creating degenerated orthogonal mode with 90° phase shift, which in turn produces circularly polarized (CP) waves. Graphene patch is placed over SiO2 substrate. Slot loading in graphene patch shifts the frequency band due to a reduction in effective permittivity. Another important feature of the proposed antenna is to provide a tunable feature in the frequency response and axial ratio by changing the chemical potential. The proposed antenna operates from 5.85 to 6.05 THz. 3-dB axial ratio is obtained from 5.85 to 5.95 THz. Good value of gain, as well as left-handed circular polarization characteristics, makes the proposed THz antenna in sensing applications. [ABSTRACT FROM AUTHOR]