Octagonal Shaped Annular Ring Pattern Reconfigurable Antenna Designs for Cognitive Radio Application

An Octagonal shaped Annular Ring pattern reconfigurable antenna is proposed for cognitive radio applications which gives Omni-directional and directional pattern at 1.3 GHz. The antenna has the frequency switching capability at 1.5 GHz, 3.2 GHz, 4.8 GHz and 6.8 GHz with the use of a single PIN diode. Further, the antenna is modified by inserting a slotted square shape in an octagonal ring. With the use of two diodes, the proposed antenna shows the pattern diversity at 3.2 GHz and 4.6 GHz with the gain of 6.23 dBi. Also, the antenna shows the frequency switching for 1.5 GHz, 3.1 GHz, 4 GHz, 4.3 GHz, 4.8 GHz and 6.8 GHz with the different states of the PIN diode. The proposed antennas can be used for RFID, S and C band applications.