Polarization reconfigurable ultrawideband antenna for cognitive radio applications

A novel compact ultrawideband microstrip monopole antenna with reconfigurable polarization capability is presented. The antenna can be switched from linear polarization to right‐hand circular polarization (RHCP) or left‐hand circular polarization (LHCP). The measured 3‐dB axial ratio fractional bandwidth for the RHCP or the LHCP after reconfiguration is 59.5% from 5.9 to 10.9 GHz. The interest of the proposed antenna in cognitive radio systems is twofold. First, it can be used to add polarization sensing to the conventional frequency sensing. Second, there are the gains of using it to add polarization diversity in communication between cognitive devices.