Microstrip reconfigurable antenna for cognitive radio systems

A compact and low profile microstrip antenna is proposed as a framework to design a frequency-reconfigurable radiating device with four distinct and almost independent resonant frequencies with other single or multiple available resonances that can be usefully exploited by the cognitive radio system. The instant frequency reconfiguration is obtained by using pin diodes as RF switches whereas the biasing network comprises four high-impedance microstrip lines and a bias-tee.