Design of a compact four-port mmWave MIMO antenna with resonator-based band rejection

Abstract

This paper introduces a compact ultra-wideband MIMO antenna featuring an integrated notch-band response. Wideband operation is achieved through the combined use of meandered feed lines, a modified Y-shaped radiating element, and a defected ground structure. The antenna occupies a compact volume of 12 x 8 x 1.6 mm^³ and operates over the 30–42.5 GHz frequency range, while notch band from 35 to 38.5 GHz is effectively suppressed using a split-ring resonator positioned parallel to the feed line. Implemented on an RT/Duroid 5880 substrate, the antenna delivers a peak realized gain of 6.51 dB and maintains radiation efficiency above 88%. High inter-element isolation exceeding 22 dB is obtained through a dedicated decoupling structure. Moreover, the proposed MIMO system demonstrates strong diversity performance, with envelope correlation coefficient below 0.02, diversity gain greater than 9.97 dB. These characteristics confirm the suitability of the proposed antenna for compact 5G, satellite, and millimeter-wave communication platforms.