A selective frequency reconfigurable microstrip patch antenna using PIN diodes for cognitive radio applications

The main objective of this work is to design selective frequency reconfigurable antenna. The reconfigurable antenna is one of important aspect in cognitive radio systems along with sensing antennas. The frequency reconfigurable antenna is designed using microstrip patch antenna having reconfigurable filter. Overall dimension of antenna is 26 mm × 28 mm. Reconfigurable filter consist of PIN diodes as switches. In total four PIN diodes are used at two different places. One above the substrate and other three are incorporated with horizontal slot created in ground plane. By varying the slot length and electrical length of patch using different switching condition, different resonant frequencies achieved without changing the size of the antenna. FR4 epoxy substrate is used having relative permittivity of 4.4+0.088i and 1.6mm thickness. Here, in this proposed antenna twelve reconfigurable frequencies are attained using eight switching condition. The frequency bands of the antenna are varied from 2.76 GHz to 8 GHz. The antenna operates in both single band mode as well as multi band mode by changing the state of the PIN diode. For each case reflection coefficient should maintain less than -10 dB throughout the operating frequency. Antenna analysis is done using software HFSS.