Design of a Frequency Reconfigurable Notched-Band Ultra-Wideband Antenna for Cognitive Radio Applications

This paper proposes a frequency reconfigurable notched-band UWB antenna design, which is capable of wide band rejection. We begin with a conventional reconfigurable modified-square monopole printed antenna and insert a U-shaped slot to create the rejection band. Next, we add two identical SMV1249 varactor diodes with variable capacitances in the created slots to tune the rejected band. We modify the capacitances, which, in turn, controls rejected band by controlling the reverse bias voltage applied across the varactor diodes. The proposed structure has been simulated, optimized, fabricated and experimentally tested. Good agreement has been achieved between the simulation and measurement results. Experimental results show that when the bias voltage is varied from 0 to 7 V, the antenna can be reconfigured to achieve various rejection frequency bands, and to maintain good impedance match as well as stable radiation patterns over the explored frequency band ranging from 1 to 6 GHz.