Frequency reconfigurable microstrip antenna for cognitive radio applications

This paper presents a selective frequency reconfigurable antenna, suitable for cognitive radio applications. Reconfigurability is achieved by inserting PIN diode switches in DMS(defected microstrip structure) `T' slot filter. The proposed antenna is capable of switching between a wide operating band of 3.0 GHz - 10 GHz and six different narrow band operating from 5 GHz to 10 GHz. UWB case is used for sensing the entire band and then adjusting its bandwidth to select the suitable sub-band and pre-filter out the other ones to communicate with wireless devices without interference with others. The proposed antenna patch is a combination of two semi-circular patches. For each case reflection coefficient is calculated, it maintains less than -10 dB throughout the operating frequency. Radiation Patterns for each case also reveal a very low distortion as required. Gain is more than 70% in each case.