An Integrated Dual MIMO Antenna System With Dual-Function GND-Plane Frequency-Agile Antenna

In this letter, an integrated multiple-input-multiple-output (MIMO) antenna system is presented. The proposed design consists of a two-element printed inverted F-shape (IFA) MIMO antenna integrated with a two-element frequency-agile annular slot-based MIMO antenna system. The IFA operates at the WLAN band, while the annular slots act as an isolation enhancement structure between the two IFA elements. Furthermore, the annular slots are tuned over the bands from 1.73 to 2.28 GHz with a minimum bandwidth of 60 MHz. The slots are made reconfigurable using varactor diodes. The integrated MIMO antenna system is designed on commercially available FR-4 substrate with dimensions 50 x 110 x 1.56 mm(3). All the antenna elements are of small size, low profile, and planar in structure and hence can easily be accommodated in wireless devices for second-generation cognitive radio applications.