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Band-Reconfigurable Monopole Antenna for Cognitive Radio Applications

ABSTRACT A single-port compact planar integrated ultra-wideband (UWB)/frequency-reconfigurable narrowband monopole antenna is proposed. Reconfigurability is achieved by inserting a varactor-diode tuned bandpass filter into the feed line of the UWB antenna. The antenna operation is changed from wideband to narrowband by activating PIN diode switches in the structure. Good tunability obtained within a wide sensing band of 2.2–6 GHz is significant for cognitive radio applications.