Compact Self-Isolated Four-Element MIMO Antenna for WLAN and ISM Bands Application

A compact self-isolated four-element MIMO antenna is introduced for use in ISM systems and WLAN applications in the 2.4 GHz frequency band. The proposed design consists of four printed dipoles so four integrated baluns are responsible for feeding these antennas. By choosing an appropriate arrangement of the elements next to each other and using the feature of self-isolated antennas, great isolation is achieved in the first step. Finally, by utilizing a printed decoupling component in the space between the dipoles, the value of the envelope correlation coefficient (ECC) parameter comes very close to zero for the MIMO antenna. The major part of the isolation in this design is the responsibility of the self-isolated technique, and adding the decoupling element at the last stage of the design is to complete the antenna isolation process. The fabricated prototype of the proposed MIMO antenna operating at 2.25-2.87 GHz frequency band reaches the measured port-to-port isolation of better than 19 dB, ECC of less than 0.0009, the peak gain of 8.6 dBi with total dimensions of $1.11\lambda _{0}\times 1.11 \lambda _{0}\times 0.34\lambda _{0}$ . The numerical and experimental results approve the excellent MIMO performance for 2.4 GHz applications.