  Cognitive radio is rapidly shaping the future of wireless communications.
Research on antenna design is very critical for the implementation of cognitive
radio. A special antenna is required in cognitive radio for sensing and
communicating. For the purpose of spectrum sensing, an Ultrawideband (UWB)
antenna is being considered as a potential candidate by many experts. This
paper provides a detailed discussion of the existing UWB spectrum sensing
antenna designs for cognitive radio system. Simulation results for a promising
cognitive radio antenna which provides a reconfigurable function in the range
of 5-6 GHz have also been presented and shown to match closely with the
measured results.
