A three-resolution UWB frequency reconfigurable Antipodal Vivaldi antenna for Cognitive Radios

In this paper, a frequency reconfigurable Antipodal Vivaldi antenna capable of covering a wide frequency band (2.2 to 11 GHz) with three different resolutions is presented. By incorporating four low Q resonators only, the proposed antenna is able to cover the whole band of interest in one (UWB mode), three (3-sub mode) or seven (7-sub mode) sub-bands, giving a multi-resolution UWB antenna. The Ultra Wideband mode is obtained by using the antipodal Vivaldi with all resonators deactivated. The 3-sub mode is obtained by activating one resonator at a time while the 7-sub mode involves two resonators at a time. The switching between the different bands of a mode is achieved by selecting the proper resonators and controlling their length. The proposed antenna provides frequency agility that allows working in any part of the considered band with a choice of three different bandwidths, which is believed to be highly suitable for Cognitive Radio applications. To present the work, simulated and measured results are given and discussed.