This paper presents a planar, compact 8-element frequency-reconfigurable multiple-input-multiple-output (MIMO) antenna system. The proposed design can be utilized as a communication antenna for cognitive radio (CR) front-end applications. The proposed antenna design contains 8 elements on a single substrate board. Frequency reconfigurablility is achieved using varactor diode in the middle of each antenna element by varying the capacitive reactance of the slot. The proposed antenna system provides very wide frequency tunable characteristics from 1.6 to 2.48 GHz. The proposed design covers several well-known frequency bands like LTE, GSM-1800, PCS-1900, WLAN along with several others. Moreover, rectangular defected ground slots are used between vertically placed antenna elements to enhance the isolation. The complete antenna system is realized on single FR-4 substrate of dimensions 120×60×1.56 mm3. The performance of proposed design is demonstrated by presenting both the simulated and measured results with close agreement achieved between the two which validates the proposed design.
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