Switched-band Vivaldi antenna with hexagonal slots for cognitive radio applications

Frequency reconfiguration is a requirement in most of the communication related activities involving multiband communication. A novel frequency reconfigurable Vivaldi antenna that can be used for cognitive radio is explored. In a Cognitive Radio system, the antenna should be capable of sensing the entire bandwidth and should be able to select a specific frequency. In this work, spectrum sensing is carried out by a Vivaldi antenna which is operating for a bandwidth of 2.5-12 GHz. The frequency reconfiguration is achieved by inserting switchable hexagonal slots into the ground plane of the structure. Different frequencies from 2.5-12 GHz can be selected by using PIN diodes. Three pairs of hexagonal slots are introduced in the ground plane and if each pair is connected they will radiate corresponding frequency. The designed antenna can select frequencies 2.6 GHz, 6.6 GHz and 10.6 GHz from the entire bandwidth. The advantage this technique is that a single terminal can operate in different modes. This technique also reduces the interference at the reciever. Simulation of the antenna is done by using Ansoft HFSS 15.