A Selective Frequency-Reconfigurable Antenna for Cognitive Radio Applications

This letter presents a selective frequency-reconfigurable antenna, suitable for cognitive radio applications. The proposed antenna is capable of switching between a wide operating band of 2.63-3.7 GHz and four different subbands, which allows using it for sensing the entire band and then adjusting its bandwidth to select the suitable sub-band and prefilter out the other ones. The antenna is composed of a radiating element in the form of an inverted U fed by a microstrip line on its upper side. In order to achieve a selective frequency reconfiguration, four horizontal slots with integrated p-i-n diode switches are incorporated in the ground plane to act as reconfigurable filter. Some of the switches are used to alter the antenna bandwidth, while the others are employed to shift the operating band by varying the electrical length of the middle slots. To present the work, both simulated and measured results are presented, and a good agreement is achieved.