Isolation Enhancement of Closely Spaced MIMO System Using Inverted Fork Shaped Decoupling Structure

A two element closely spaced microstrip MIMO antenna with improved isolation characteristics is proposed. An inverted fork-shaped decoupling (IFSD) structure is placed between two closely spaced radiating elements, having. edge-to-edge spacing. Further, a rectangular slot is designed on each radiating element to fill the null in the antenna broadside radiation pattern. The isolation ($S_{\mathbf{21}} and S_{\mathbf{12}}$) of more than 20 dB at 5.5 GHz is achieved using the proposed technique. Antenna elements provide a very good impedance matching ($S_{\mathbf{11}} \lt-15$ dB) at 5.5 GHz. Implementation of IFSD structure and slot provide enhanced isolation of 65.39% compared to MIMO system without proposed technique. The proposed MIMO antenna structure having effective dimensions of. $0.86 \lambda_{0} \times 0.64 \lambda_{0}$.is simple to design and low in cost. The total-active-reflection- coefficient (TARC) and envelope-correlation-coefficient (ECC) of the antenna are below 0.3 and 0.005 respectively. The proposed structure is fabricated and measured.