A defected ground structure for isolation enhancement in a printed MIMO antenna system

In this work, a novel defected ground structure (DGS) based isolation technique is proposed for printed antennas. The DGS is capable of improving the isolation of a dual band antenna especially for the low bands (800MHz). A 4-shaped MIMO antenna system is used to test the performance of the isolation structure. The proposed method relies on a modified dumbbell shaped DGS to improve the isolation for high band (2440-2980). The primary rectangles of the dumbbell are loaded with a spiral to cover the low band (803-823MHz). The minimum isolation for the low band and high band was approximately 17dB and 9dB respectively. A minimum isolation improvement of 14dB and 4dB was observed for the low band and high band respectively compared to the original MIMO antenna system under test without such a structure.