An optically-switched frequency reconfigurable antenna for cognitive radio applications

In this paper, an optically-switched frequency-reconfigurable antenna for cognitive radio applications has been proposed. The antenna design is comprised of two units, namely the UWB unit, that senses the spectrum from 2.5-8 GHz, and the reconfigurable unit that switches between 3.9 GHz and 6.2 GHz resonant frequencies. The dark and active states of the reconfigurable unit are controlled using IREDs (880 nm). A match between measured and simulated transmission of an optically switched transmission line was used to estimate the conductivity of a medium resistive (8 Ω-cm) Si switch for active and dark states. However, the conductivity estimated for the active state (70 S/m) and dark state (5 S/m) of the medium resistive Si was not sufficient to yield best performance of the reconfigurable antenna. Hence feasible estimates of conductivity for both the active (168 S/m) and dark state (4.25 × 10-4 S/m) of high resistive Si were substituted into the reconfigurable antenna design in CST Studio Suite to enhance the performance.