Design and development of a FSS backed high gain UWB MIMO planar antenna for FR-II NR bands

• The presented antenna operates in a wideband from 23.57 GHz to 39.35 GHz with a fractional bandwidth of 50 % and an impedance bandwidth of 15.78 GHz.. • The antenna radiation efficiency is >92 % through the entire working band. • The antenna provides a high maximum gain of 13 dBi. • The mutual coupling between the antenna ports is very low. • This antenna effectively covers key millimetre-wave frequency bands, making it ideal for high-speed 5 G millimetre wave applications. This manuscript presents a highly compact UWB quad-port multi-input multi-output (MIMO) radiator with physical dimensions of 1.73 λ l × 1.73 λ l × 0.04 λ l ( λ l – wavelength corresponding to the lower cutoff frequency of 23.57 GHz) for the FR-II NR band. The proposed radiator consists of two rectangular patches, a split feed and a defected ground structure (DGS). The DGS features a partial ground with the two square cuts at the bottom behind the feed positions and a stub on the bottom plane. The proposed MIMO radiator operates at 23.57 GHz to 39.35 GHz, achieving a fractional bandwidth of 50 % and an impedance bandwidth of 15.78 GHz. The radiator is fabricated on an RT/duroid 5880 substrate with a dielectric constant of 2.2, demonstrating a radiation efficiency of over 92 % across the entire operating band. In order to enhance gain, a frequency-selective surface (FSS) is incorporated beneath the MIMO antenna, resulting in improvements of gain from 7.78dBi to 13dBi. The diversity performance parameters are evaluated and the exhibited values are suitable for 5 G applications. A prototype is fabricated and measured, demonstrating that the simulated and measured results are in close agreement.