A Tri-Band MIMO Antenna for WLAN/WiMAX Application

A tri-band multiple-input-multiple-output (MIMO) antenna that covers all frequency bands required for WLAN and WiMAX applications is presented. Three resonant bands are achieved by a folded monopole with a compact size of 11.5 × 15. 6m m 2 . The MIMO system consists of two symmetrically placed monopoles. A stepped slot ended with an ellipse on the ground plane is etched to reduce the mutual coupling between the two monopoles. The overall dimension of this MIMO system is 50 × 50 mm 2 . The prototype of the antenna is fabricated and measured. Measured results show that the antenna's impedance bandwidth is 450 (18%), 350 (10%), 1200 (21.8%) MHz at the three resonant frequency points (2.5 GHz, 3.5 GHz, 5.5 GHz) with mutual coupling between the antenna elements less than �18 dB in whole frequency band, making this antenna a good candidate for portable application.