Compact quad-port MIMO antenna with circular defected ground structure for sub-6 GHz wireless systems

Abstract

A compact quad-port MIMO antenna operating at 5.8 GHz was proposed for WLAN and sub-6 GHz wireless applications. The antenna was implemented on an FR-4 substrate with overall dimensions of 40 × 40 × 1.6 mm3 and employed hook-shaped radiating elements arranged orthogonally to achieve polarization diversity. A defected ground structure (DGS) formed by introducing circular gaps in the ground plane improves isolation and suppresses surface currents. The antenna was designed and analysed using HFSS. The results show a −33 dB return loss, a 3.2 dB peak gain, and a diversity gain of approximately −10 dB, with an envelope correlation coefficient as low as 0.0001. The specific absorption rate is reduced from 1.81 W kg−1–1.31 W kg−1 when DGS is used, remaining well below the FCC safety threshold of 1.6 W kg−1 and improving user safety during handheld operation. The proposed design offers enhanced gain, improved isolation, and low SAR making it a significant step forward for modern 5.8 GHz wireless and portable communication devices.