Frequency-reconfigurable wideband antenna with dual-notch response for cognitive radios application

A frequency-reconfigurable wideband antenna with dual-notch response for cognitive radios (CRs) application is presented. By placing stub-loaded resonators beside the feed line, two notched bands are generated. The central frequency of one notched band can be controlled by loading varactors while the other notched band remains constant. The biasing circuits for the varactors consist of Bias T and high-impedance resistors. To validate the proposed concept, an experimental antenna is designed, fabricated and measured. The simulated results including return losses and radiation characteristics as well as some measured results are presented, declaring that the proposed antennas have good impedance matching performance and radiation pattern properties.