Dual-band composite high gain MIMO antenna for 5G NR applications employing shareable small cell radio unit

In this paper, a MIMO antenna is presented consisting of 4 composite elements. Each antenna element consists of a U-shaped conducting structure and a perturbed barrel Dielectric Resonator Antenna (PB-DRA) structure. The former is loaded with a bow-tie patch, and it is parasitically excited through the U-shaped microstrip element. The additional bow-tie structure is designed for the gain enhancement in the 5G NR frequency range 1 (FR1) band and frequency range 2 (FR2). The PB-DRA has a dielectric constant of 8, and it is excited in higher-order mode to achieve resonance in FR2. The composite structure offers dual-band resonance with 3.85 GHz resonant frequency in the FR1 band and 26.65 GHz in the FR2 band, giving a large frequency ratio radiation characteristic. The proposed antenna offers impedance bandwidth of 2.02 GHz in the FR1 band, and 5.3 GHz in the FR2 band. Achieving multi-band resonance with a large frequency ratio is essential for exploiting the true benefit of 5G communication, as it enables operation across widely separated bands and supports multi-operator radio access networks (MORAN). The peak gains observed in the FR1 and FR2 bands are 8.23 dB and 13.14 dB, respectively. The proposed antenna is specifically designed to meet the requirements of the Open RAN compliant shareable 5G small cell radio unit specifications, by offering resonance in n77/n78 and n257/n261 bands, and end-fire radiation characteristics, ensuring sufficient coverage in the indoor and dense urban outdoor environment.