A high-isolation compact two-part MIMO antenna for next-generation mmWave super UWB communication

This paper presents a compact ultra-super-wideband Tapered Polygonal Shaped Monopole Antenna (TPSMA) and its systematic extension to a high-isolation two-element MIMO configuration for Ku-/K-/Ka-band satellite communication, fixed wireless access (FWA), and advanced 5G mmWave applications, including the 28-GHz band corresponding to 3GPP NR bands n256 and n257. The single-element antenna is progressively evolved from a conventional elliptical monopole through radiator reshaping and ground-plane optimization, achieving wide impedance bandwidth without employing slots, vias, multilayer substrates, or external matching networks. The optimized TPSMA occupies a compact footprint of 11 × 12 × 0.787 mm 3 and exhibits stable radiation characteristics with high efficiency over the operating band. The antenna is further extended to a two-element MIMO configuration using planar and orthogonal orientations with individual and shared ground-plane structures, maintaining a compact overall size of 23 × 11 × 0.787 mm 3 . High isolation is achieved through optimized inter-element spacing, intra-element gap control, and orthogonal element placement, eliminating the need for additional decoupling structures. A comprehensive comparison between planar and orthogonal arrangements, as well as individual and common ground configurations, is presented. The proposed MIMO antenna achieves an ultra-super-wide impedance bandwidth of 12.15–36.10 GHz (|S 11 |< − 10 dB) with a minimum reflection coefficient of − 36.89 dB, isolation exceeding 22.55 dB, stable radiation patterns, and excellent diversity performance. The key novelty of this work lies in realizing ultra-wideband, compact, and high-isolation MIMO performance exclusively through radiator geometry and ground-plane engineering, making the proposed antenna a strong candidate for next-generation wideband wireless and satellite communication systems.