Tunable slot-loaded patch antenna for cognitive radio

This paper presents a reconfigurable microstrip patch antenna for cognitive radio applications. The antenna is fed by a coplanar waveguide via capacitive coupling slot. The antenna allows easy tuning of the resonant frequency by employing two switches and two capacitors inserted in the coupling slot. The resonant frequency of the antenna can be adjusted by activating the switches and/or varying the capacitors. The achievable tuning bandwidth is 1.7:1 and it extends from 1.39 GHz to 2.36 GHz. The structure has a compact and simple biasing circuit. The proposed antenna was verified through both electromagnetic simulation and measurement which indicate that it presents very good impedance matching, stable radiation patterns and good gain within the tuning bandwidth.