Highly Compact Wideband High-Gain Four-Element MIMO Antenna for 5G New Radio IoT

Wideband millimeter-wave (mm-wave) coverage is essential for the high-speed, low-latency communication required in next-generation 5G New radio (NR) Internet of Things (IoT) systems. This study develops a T-shaped four-element, highly compact wideband multiple-input multiple-output (MIMO) antenna covering the mm-wave n260 (37-40 GHz) and n259 (42-43.5 GHz) bands for 5G NR IoT applications. The antenna is designed on a 0.76 mm-thick Rogers RO4350B substrate with overall dimensions of 28x 28 mm2 ( 3.3x 3.3 lambda 2 ). For design simplicity, a T-shaped patch backed by a full-ground plane is devised to serve as the radiator of a single-element antenna with the dimensions of (Ls x Ws) mm2, optimized through a systematic three-step design process for improved performance. Moreover, the design has evolved into a 4x4 orthogonal MIMO configuration, achieving improved gain, polarization diversity, and higher data rates, with each element exhibiting wideband characteristics across 11.5 GHz (36.5-48 GHz) with high gains of 9.8 dBi and 6.6 dBi at n260 and n259 5G mm-wave bands, respectively. Additionally, arc-shaped complementary split-ring resonators (CSRR) are integrated into the ground plane to significantly enhance the gain while effectively reducing mutual coupling, remarkably achieving a maximum gain of 9.8 dBi. Furthermore, the MIMO antenna exhibits an envelope correlation coefficient of less than 0.10 between any two MIMO elements encountering the required condition of <0.5, ensuring good diversity gain of 9.99 dB, minimum isolation of 18 dB, and total efficiency of 86% at mm-wave n260 band and 89% at mm-wave n259 band. The measured and simulated results are in good agreement, confirming its viability for future 5G mm-wave IoT devices.