The design of filter antennas with reconfigurable band stops is proposed. They are meant for employment in ultrawideband cognitive radio (UWB-CR) systems, where unlicensed users communicate using adaptive pulses that have nulls in the bands used by licensed users. Neural networks or circuits implementing the Parks-McClellan algorithm can generate such pulses. With filter antennas, reconfigurable bandstop filters are first designed, to induce adaptive nulls in UWB pulses, and are then integrated in the feed line of a UWB antenna. The advantages of this combination are discussed. The filters are based on split-ring resonators (SRRs) and complementary split-ring resonators (CSRRs). The relationship between the SRR and CSRR parameters and the stop band is also studied.
2. Chen, K.-C. and R. Prasad, Cognitive Radio Networks, John Wiley & Sons, West Sussex, United Kingdom, 2009.
3. Arslan, H. and M. Sahin, "UWB-based cognitive radio networks," Cognitive Wireless Communication Networks, Springer, USA, 2007.
4. Zhang, H., X. Zhou, and T. Chen, "Ultra-wideband cognitive radio for dynamic spectrum accessing networks," Cognitive Radio Networks, CRC Press, Boca Raton, Florida, 2009.
5. Parks, T. and J. McClellan, "Chebyshev approximation for nonrecursive digital filters with linear phase," IEEE Transactions on Circuit Theory, Vol. 19, No. 2, 189-194, Mar. 1972.
6. McClellan, J. and T. Parks, "A personal history of the Parks-McClellan algorithm," IEEE Signal Processing Magazine, Vol. 22, No. 2, 82-86, Mar. 2005.
7. Shi, X., Adaptive UWB pulse design method for multiple narrowband interference suppression, The 2010 IEEE International Conference on Intelligent Computing and Intelligent Systems (ICIS 2010), 545-548, Missouri, USA, 2010.
8. Hopfield, J. J., "Neural networks and physical systems with emergent collective computational abilities," Proceedings of the National Academy of Sciences, Vol. 79, 2554-2558, Washington DC, USA, 1982.
9. Powell, J. D., "Radial basis function approximations to polynomials," Numerical Analysis 1987, 223-241, Dundee, UK, 1987.
10. Bin, L., Z. Zheng, and Z. Weixia, A novel spectrum adaptive UWB pulse: Application in cognitive radio, The 2009 IEEE Vehicular Technology Conference, 1-5, Anchorage, AK, USA, 2009.
11. Kanj, H. and M. Popovic, "Microwave-range broadband Dark Eyes antenna: Detailed analysis and design," IEEE Antennas and Wireless Propagation Letters, Vol. 4, 262-265, 2005.
12. Pendry, J. B., A. J. Holden, D. J. Robbins, and W. J. Stewart, "Magnetism from conductors and enhanced nonlinear phenomena," IEEE Trans. Microw. Theory Tech., Vol. 47, No. 11, 2075-2084, 1999.
13. Falcone, F., T. Lopetegi, M. A. G. Laso, J. D. Baena, J. Bonache, M. Beruete, R. Marques, F. Martn, and M. Sorolla, "Babinet principle applied to the design of metasurfaces and metamaterials," Physical Review Letters, Vol. 93, No. 19, 197401-1-197401-4, Nov. 2004.
14. Ansoft HFSS, Pittsburg, PA 15219, USA.
15. Agilent ADS, Santa Clara, CA 95051, USA.
16. Li, C.-M. and L.-H. Ye, "Improved dual band-notched UWB slot antenna with controllable notched bandwidths," Progress In Electromagnetics Research, Vol. 115, 477-493, 2011.
17. Liao, X.-J., H.-C. Yang, N. Han, and Y. Li, "Aperture UWB antenna with triple band-notched characteristics," Electronics Letters, Vol. 47, No. 2, 77-79, Jan. 2011.
18. Al-Husseini, M., A. Ramadan, A. El-Hajj, K. Y. Kabalan, Y. Tawk, and C. G. Christodoulou, "Design based on complementary split-ring resonators of an antenna with controllable band notches for UWB cognitive radio applications," The 2011 IEEE International Symposium on Antennas and Propagation (APS/URSI 2011), 1120-1122, Spokane, WA, USA, Jul. 3-8, 2011.
19. Gardner, P., P. S. Hall, M. R. Hamid, and F. Ghanem, Reconfigurable antennas for cognitive radio, The 2011 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications (APWC 2011), 1225-1228, Torino, Italy, Sept. 12-16, 2011.
20. Al-Husseini, M., A. Ramadan, M. E. Zamudio, C. G. Christodoulou, A. El-Hajj, and K. Y. Kabalan, "A UWB antenna combined with a reconf-gurable bandpass filter for cognitive radio applications," The 2011 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications (APWC 2011), 902-904, Torino, Italy, Sept. 12-16, 2011.