Miniaturized dual-band MIMO antenna with high gain and isolation for mm-wave applications

This work presents a compact dual-band four-element multiple-input multiple-output (MIMO) antenna designed for millimeter-wave (mm-wave) applications, with particular emphasis on 5G wireless communication systems. The proposed antenna occupies an ultra-compact volume of 15 × 15 × 0.8 mm³ (approximately 0.55λ × 0.55λ × 0.03λ at 28 GHz), making it highly suitable for integration into space-constrained wireless devices. The antenna operates efficiently over two mm-wave bands, 29-31 GHz and 36.5-38.5 GHz, covering key 5G NR-FR2 frequency allocations. By incorporating strategically placed slots and a compact radiating structure, the antenna achieves a peak realized gain of 8.1 dBi and 8.64 dBi in the lower and upper operating bands, respectively, while maintaining strong port isolation exceeding 25 dB. Both simulated and measured results demonstrate good agreement, validating the effectiveness of the proposed design. A comprehensive MIMO performance evaluation confirms excellent diversity characteristics, with a very low envelope correlation coefficient (ECC) of less than 0.001, a high diversity gain (DG) of approximately 9.99 dB, a total active reflection coefficient (TARC) maintained within - 5 to 5 dB, and a low channel capacity loss (CCL) of 0.21 bit/s/Hz across the operating bands. Owing to its compact size, high gain, strong isolation, and robust MIMO performance, the proposed antenna is a promising candidate for next-generation mm-wave 5G and future wireless communication systems.