Multifunctional Antenna with Wideband and Narrowband Spectrum Sensing for Cognitive Radio Application

A multifunctional antenna (MFA) has been designed using a circular arc-shaped antenna (CA-SA) with a multifunctional filter (MFF) for cognitive radio applications. To achieve wideband spectrum sensing, a CA-SA has been used, whereas a MFF is integrated in the feedline for narrowband spectrum sensing. The proposed antenna system includes the wideband spectrum as a sensing window, and the frequency-tunable narrowband filter offers a communication window. The wideband antenna unit can provide an impedance bandwidth of 105.55% (1.7–5.5) GHz. Whereas, operating in the second mode, it can offer frequency tunability in the narrowband, which provides an impedance bandwidth of 25.64% (3.4–4.4) GHz. With the highest observed realized gain of 2.8 dB and a radiation efficiency of $\gt80$%, respectively, both modes exhibit good broadside radiation properties for the cognitive radio response.