1. Liang, C. S., D. A. Streater, J.-M. Jin, E. Dunn, and T. Rozendal, "A quantitative study of luneberg-lens reflectors," IEEE Antennas Propag. Mag., Vol. 47, No. 2, 30-41, 2005.
doi:10.1109/MAP.2005.1487776 Google Scholar
2. Vinogradov, S. S., P. D. Smith, J. S. Kot, and N. Nikolic, "Radar cross-section studies of spherical lens reflectors," Progress In Electromagnetics Research, Vol. 72, 325-337, 2007.
doi:10.2528/PIER07031206 Google Scholar
3. Nikolic, N., J. S. Kot, and S. Vinogradov, "Scattering by a Luneberg lens partially covered by a metallic cap," Journal of Electromagnetic Waves and Applications, Vol. 21, No. 4, 549-563, 2007.
doi:10.1163/156939307780616856 Google Scholar
4. Schrank, H. and J. Sanford, "A Luneberg-lens update," IEEE Antennas Propag. Mag., Vol. 37, No. 1, 76-79, Feb. 1995.
doi:10.1109/74.370587 Google Scholar
5. Schoenlinner, B., X. Wu, J. P. Ebling, G. V. Eleftheriades, and G. M. Rebeiz, "Wide-scan spherical-lens antennas for automotive radars," IEEE Trans. Microwave Theory Tech., Vol. 50, No. 9, 2166-2175, Sep. 2002.
doi:10.1109/TMTT.2002.802331 Google Scholar
6. Dou, W. B., Z. L. Sun, and X. Q. Tan, "Fields in the focal space of symmetrical hyperbolic focusing lens," Progress In Electromagnetics Research, Vol. 20, 213-226, 1998.
doi:10.2528/PIER98021300 Google Scholar
7. Thakur, J. P., W.-G. Kim, and Y.-H. Kim, "Large aperture low aberration aspheric dielectric lens antenna for W-band quasi- optics," Progress In Electromagnetics Research, Vol. 103, 57-65, 2010.
doi:10.2528/PIER10022404 Google Scholar
8. Sun, F. and S. He, "Can Maxwell's fish eye lens really give perfect imaging?," Progress In Electromagnetics Research, Vol. 108, 307-322, 2010.
doi:10.2528/PIER10091003 Google Scholar
9. Sun, F., X. Ge, and S. He, "Can Maxwell's fish eye lens really give perfect imaging? Part II. The case with passive drains," Progress In Electromagnetics Research, Vol. 110, 313-328, 2010.
doi:10.2528/PIER10110313 Google Scholar
10. Zhong, M., S. Yang, and Z. Nie, "Optimization of a Luneberg lens antenna using the differential evolution algorithm," Proc. IEEE AP-S Int. Symp. Dig., San Diego, CA, Jul. 2008.
11. Stratton, J. A., Electromagnetic Theory, 204-207, McGraw Hill, 1941.
12. Tai, C. T., "The electromagnetic theory of the spherical Luneberg lens," Appl. Sci. Res., Vol. 7, 113-130, Section B, 1958.
13. Sanford, J. R., "Scattering by spherically stratified microwave lens antennas," IEEE Trans. Antennas Propag., Vol. 42, No. 5, 690-698, May 1994.
doi:10.1109/8.299568 Google Scholar
14. Mosallaei, H. and Y. Rahmat-Samii, "Non-uniform Luneburg and two-shell lens antennas: Radiation characteristics and design optimization," IEEE Trans. Antennas Propag., Vol. 49, No. 1, 60-69, Jan. 2001.
doi:10.1109/8.910531 Google Scholar
15. Thornton, J., "Wide-scanning multi-layer hemisphere lens antenna for Ka band," IEE Proc.-Microw. Antennas Propag., Vol. 153, No. 6, 573-578, 2006.
doi:10.1049/ip-map:20050220 Google Scholar
16. Fuchs, B., R. Golubovic, A. K. Skrivervik, and J. R. Mosig, "Spherical lens antenna designs with particle swarm optimization," Microw. Opt. Techn. Lett., Vol. 52, No. 7, 1655-1659, Jul. 2010.
doi:10.1002/mop.25278 Google Scholar
17. Fuchs, B., S. Palud, L. Le Coq, O. Lafond, M. Himdi, and S. Rondineau, "Scattering of spherically and hemispherically stratified Lenses fed by any real source," IEEE Trans. Antennas Propag., Vol. 56, No. 2, 450-460, Feb. 2008.
doi:10.1109/TAP.2007.915458 Google Scholar
18. Peeler, G. D. M. and H. P. Coleman, "Microwave stepped-index Luneberg lenses," IEEE Trans. Antennas Propag., Vol. 6, No. 2, 202-207, 1958.
doi:10.1109/TAP.1958.1144575 Google Scholar
19. Carpenter, Michael, P., et al. Lens of gradient dielectric constant and methods of production, U. S. Patent 6-433-936 B1, 2001.
20. Rondineau, S., M. Himdi, and J. Sorieux, "A sliced spherical Lüneburg lens," IEEE Antennas Wireless Propag. Lett., Vol. 2, 163-166, 2003.
doi:10.1109/LAWP.2003.819045 Google Scholar
21. Ma, H. F., X. Chen, H. S. Xu, X. M. Yang, W. X. Jiang, and T.-J. Cui, "Experiments on high-performance beam-scanning antennas made of gradient-index metamaterials," Appl. Phys. Lett., Vol. 95, 094107, 2009.
doi:10.1063/1.3223608 Google Scholar
22. Ma, H. F., X. Chen, X. M. Yang, W. X. Jiang, and T.-J. Cui, "Design of multibeam scanning antennas with high gains and low sidelobes using gradient-index metamaterials," J. Appl. Phys., Vol. 107, 014902, 2010.
doi:10.1063/1.3275505 Google Scholar
23. Wang, G., Y. Gong, and H. Wang, "On the size of left-handed material lens for near-field target detection by focus scanning," Progress In Electromagnetics Research, Vol. 87, 345-361, 2008.
doi:10.2528/PIER08101902 Google Scholar
24. Andrés-García, B., L. E. García-Muñoz, V. Gonzalez-Posadas, F. J. Herraiz-Martínez, and D. Segovia-Vargas, "Filtering lens structure based on SRRs in the low THz band," Progress In Electromagnetics Research, Vol. 93, 71-90, 2009.
doi:10.2528/PIER09040105 Google Scholar
25. Agastra, E., G. Bellaveglia, L. Lucci, R. Nesti, G. Pelosi, G. Ruggerini, and S. Selleri, "Genetic algorithm optimization of high-efficiency wide-band multimodal square horns for discrete lenses," Progress In Electromagnetics Research, Vol. 83, 335-352, 2008.
doi:10.2528/PIER08061806 Google Scholar
26. Hosseini, S. A. and Z. Atlasbaf, "Optimization of side lobe level and fixing quasi-nulls in both of the sum and difference patterns by using continuous Ant Colony Optimization (ACO) method," Progress In Electromagnetics Research, Vol. 79, 321-337, 2008.
doi:10.2528/PIER07102901 Google Scholar
27. Storn, R. and M. Siemens AG, "On the usage of differential evolution for function optimization," Biennial Conference of the North American, 519-523, 1996. Google Scholar
28. Qing, A., "Electromagnetic inverse scattering of multiple two-dimensional perfectly conducting objects by the differential evolution strategy," IEEE Trans. Antennas Propag., Vol. 51, 1251-1262, 2003.
doi:10.1109/TAP.2003.811492 Google Scholar
29. Yang , S., Y. B. Gan, and A. Qing, "Antenna-array pattern nulling using a differential evolution algorithm," Int. J. RF Microwave Comput. Aided Eng., Vol. 14, No. 1, 57-63, 2004.
doi:10.1002/mmce.10118 Google Scholar
30. Li, J.-Y. and J. L. Guo, "Optimization technique using differential evolution for Yagi-Uda antennas," Journal of Electromagnetic Waves and Applications, Vol. 23, No. 4, 449-461, 2009.
doi:10.1163/156939309787612356 Google Scholar
31. Li, G., S. Yang, M. Huang, and Z. Nie, "Sidelobe suppression in time modulated linear arrays with unequal element spacing," Journal of Electromagnetic Waves and Applications, Vol. 24, No. 5--6, 775-783, 2010.
doi:10.1163/156939310791036368 Google Scholar