Compact Four-Port MIMO Patch Antenna with Hybrid Defected Ground Structure for Wideband and Dual-Band Wireless Applications

Abstract

In this paper, a compact four-port MIMO patch antenna is proposed that supports wideband and dual-band operation, aimed at sub-6 GHz, C-band, and extended upper microwave frequency applications (based on simulation). The antenna was made on a very cheap FR-4 substrate (εr = 4.4, tan δ = 0.02, thickness = 1.6 mm), and it only takes up a 24 × 24 × 1.6 mm³ area. Four identical rectangular patch elements (5.6 × 7.2 mm each) are laid out in a 2×2 matrix. A hybrid slotting method – L-shaped and two circular slots on each patch, along with a defected ground structure (DGS) featuring a plus-shaped slot and three circular slots – renders wide impedance bandwidth and high inter-port isolation. Simulation work was done in ANSYS HFSS, while physical characterization was realized using a Keysight FieldFox N9918A vector network analyzer. A comparison between measured and simulated return loss over the 0.1–14 GHz range reveals a negative frequency shift of about 0.4 GHz, with the main measured resonance at 6.5 GHz (|S11| = –22 dB) and the main simulated resonance at 6.9 GHz (|S11| = –30 dB). At the measured resonance frequency, isolation is better than –28 dB, VSWR = 1.17, and gain = 4.1 dBi. This antenna has stable radiation patterns, low ECC (< 0.01), and high diversity gain, and is therefore a promising candidate for MIMO in 5G and wideband wireless systems.