Multifunctional Antennas for Cognitive Radio Applications

Evolution, design concept and practical realization of multifunctional antennas (MFA) are systematically reported in this paper. MFAs, traditionally evolved as an intelligent solution to mitigate lower spectrum-utilization using the opportunistic spectrum allocation-policy, are key component for modern wireless applications, such as multi-standard radios, cognitive radios (CR) of software defined radio (SDR) environment. Traditional realizations of MFAs use multiple radiating elements on a common substrate which enhances design constrains in terms of mitigating/reducing parasitic coupling and spurious impacts of the rotary arrangements required for actuating various radiating elements. In this paper, recent research contribution of designing MFAs employing a single UWB radiating element is reported. Improvised feed design with combinatorial loading of SRRs and PIN diodes on a printed monopole antenna, along with controlling their position in the feed region, results into multifunctional operation. Design strategy, techniques, and theoretical ideas for realizing MFAs along with simulated and experimental results are presented in this paper.