Reconfiguration of ultra wideband antenna for multi-band operation in cognitive radio application

Three prototypes of frequency reconfigurable ultra-wideband antennas are presented in this paper. In the first and second prototypes, reconfiguration is achieved using p-i-n diodes connected to multiple stubs of different lengths to the main feed line of the monopole. In the third prototype, the design is simplified by replacing p-i-n diodes with FET switches. The simulated and measured return loss characteristics of the the three antennas are shown in this paper. The compactness, flexibility and the ability to limit the impact of out-of-band interference make the proposed antennas good candidates for future cognitive radio portable devices.