Poonam Tiwari, Jayant Kumar Rai, Ajay Kumar Dwivedi, Vishant Gahlaut, Pinku Ranjan, Rakesh Chowdhury, Ashish Pandey
This paper introduces a high-performance quad-port Multiple-Input Multiple-Output (MIMO) antenna array for wideband 5G New Radio (NR) (n258, n257, n260, and n261) applications in the millimeter-wave (mmWave) spectrum. The target antenna structure employs a 1 × 2 element array design with microstrip line feeding and includes diamond-shaped slots along with defected ground geometry (DGG) to increase bandwidth, gain, and isolation independent of complicated decoupling components. Fabricated on low-loss Rogers RT/Duroid 5880 substrate (εr = 2.2, tanδ = 0.0009), the antenna has an ultrawide operation bandwidth of 24 GHz to 40 GHz with a 50% fractional bandwidth. The measured results show a peak gain of 18.2 dBi and outstanding inter-element isolation of over 44 dB, confirming the potential for interference-free MIMO operation of the antenna. The design also exhibits better diversity performance with an ECC of < 0.0005, diversity gain (DG) of 9.99 dB, and a CCL of < 0.3 bps/Hz, affirming its use in high-capacity, low-latency 5G mmWave systems. In addition, the compact form factor of the antenna (35 × 35 × 0.254 mm 3 ), structural simplicity, and strong performance make it extremely suitable for integration within next-generation IoT platforms, indoor/outdoor wireless systems, and flexible mmWave-enabled communication devices. The present work aims to overcome challenging problems in the realization of wideband operation, high gain, and excellent isolation in compact MIMO configurations and presents a scalable and fabrication-friendly solution for future wireless networks.