Reconfigurable ultra-wide-band patch antenna: Cognitive radio

This paper presents the fundamental principles of cognitive radio RF-system. A cognitive radio system searches and identifies unoccupied part of the spectrum to achieve the optimal mode of communication by assigning the primary and/or secondary users to the appropriate channels. Two scenarios can be adapted to operate a cognitive radio device: the underlay and interweave mode of operation. Reconfigurable antennas are used to search for unoccupied spectrum and allocate the secondary users to proper bands. This motivates the design of a new compact reconfigurable ultra-wide-band (UWB) patch antenna with a total size of 23 × 25 × 4 mm enabling communication over different UWB frequencies.