A High Isolation Frequency Reconfigurable MIMO Antenna for WiFi/WiMax Applications

This paper presents a high isolation frequency reconfigurable MIMO antenna for WLAN/WiMAX applications. The proposed MIMOantenna consists of two frequency reconfigurable antenna elements, each utilizing three PIN diodes for switching between different frequency configurations. The MIMO antenna can operate in four states, with the resonant frequencies of 2.5, 3.3, 5, and 5.6 GHz. An EBG (Electromagnetic Band Gap) structure is integrated between two antenna elements to reduce their mutual coupling. The MIMO antenna obtains an isolation value below -15 dB and good impedance matching in four operating bands. Meanwhile, the MIMO antenna size is reduced by 30 % compared to without isolation structure. The total MIMO antenna size is $40 \times 64 \times 1.6 \mathrm{~mm}$. The antenna is designed on an FR4 substrate and simulated by CST software.