1. Lo, Y. T. and S. W. Lee, Antenna Handbook --- Theory, Application, and Design, Van Nostrand Reinhold, 1988.
2. Sato, K. and H. Ujiie, "A plate Luneberg lens with the permittivity distribution controlled by hole density," Electronics and Communications in Japan (Part I: Communications), Vol. 85, No. 9, 1-12, 2002.
doi:10.1002/ecja.1120
3. Bor, J., O. Lafond, H. Merlet, P. Le Bars, M. Himdi, and , "Foam based Luneburg lens antenna at 60 GHz," Progress In Electromagnetics Research Letters, Vol. 44, 1-7, 2014.
doi:10.2528/PIERL13092405
4. Fuchs, B., L. Le Coq, O. Lafond, S. Rondineau, and M. Himdi, "Design optimization of multishell Luneburg lenses," IEEE Trans. Antennas Propag., Vol. 55, No. 2, 283-289, 2007.
doi:10.1109/TAP.2006.889849
5. Rudolph, S. M., C. Pfeiffer, and A. Grbic, "Design and free-space measurements of broadband, low-loss negative-permeability and negative-index media," IEEE Trans. Antennas Propag., Vol. 59, No. 8, 2989-2997, 2011.
doi:10.1109/TAP.2011.2158948
6. Iyer, A. K. and G. V. Eleftheriades, "A multilayer negative-refractive-index transmission-line (NRI-TL) metamaterial free-space lens at X-band," IEEE Trans. Antennas Propag., Vol. 55, No. 10, 2989-2997, 2007.
doi:10.1109/TAP.2007.905924
7. Quevedo-Teruel, O., W. Tang, R. C. Mitchell-Thomas, A. Dyke, H. Dyke, L. Zhang, S. Haq, and Y. Hao, "Transformation optics for antennas: Why limit the bandwidth with metamaterials?," Sci. Rep., Vol. 3, 1903, 2013.
8. Alitalo, P., O. Luukkonen, J. Vehmas, and S. A. Tretyakov, "Impedance-matched microwave lens," IEEE Antennas Wireless Propag. Lett., Vol. 7, 187-191, 2008.
doi:10.1109/LAWP.2008.920906
9. Alitalo, P., F. Bongard, J. Mosig, and S. Tretyakov, "Transmission-line lens antenna with embedded source," Proc. 3rd European Conference on Antennas and Propagation (EuCAP 2009), 625-629, Berlin, Germany, Mar. 23-27, 2009.
10. Eleftheriades, G. V. and K. G. Balmain, Negative-refraction Metamaterials: Fundamental Principles and Applications, Wiley, 2005.
doi:10.1002/0471744751
11. Caloz, C. and T. Itoh, Electromagnetic Metamaterials: Transmission Line Theory and Microwave Applications, Wiley, 2006.
12. Alitalo, P., O. Luukkonen, L. Jylha, J. Venermo, and S. A. Tretyakov, "Transmission-line networks cloaking objects from electromagnetic fields," IEEE Trans. Antennas Propag., Vol. 56, No. 2, 416-424, 2008.
doi:10.1109/TAP.2007.915469
13. Pfeiffer, C. and A. Grbic, "A printed, broadband Luneburg lens antenna," IEEE Trans. Antennas Propag., Vol. 58, No. 9, 3055-3059, 2010.
doi:10.1109/TAP.2010.2052582
14. Pacheco-Pena, V., V. Torres, M. Navarro-Cia, M. Beruete, M. Sorolla, and N. Engheta, "ε-near-zero graded index structure as a bi-concave metallic lens using stacked rectangular near cut-off waveguides," 7th European Conference on Antennas and Propagation (EuCAP), 2535-2537, Gothenburg, Sweden, Apr. 8-12, 2013.
15. Vehmas, J., P. Alitalo, and S. A. Tretyakov, "Experimental demonstration of antenna blockage reduction with a transmission-line cloak," IET Microwaves Antennas & Propagation, Vol. 6, No. 7, 830-834, 2012.
doi:10.1049/iet-map.2011.0509
16. Vehmas, J., P. Alitalo, and S. Tretyakov, "Low-reflection inhomogeneous microwave lens based on loaded transmission lines," 7th European Conference on Antennas and Propagation (EuCAP), 1585-1589, Gothenburg, Sweden, Apr. 8-12, 2013.
17. Alitalo, P., S. Ranvier, J. Vehmas, and S. Tretyakov, "A microwave transmission-line network guiding electromagnetic fields through a dense array of metallic objects," Metamaterials, Vol. 2, No. 4, 206-212, 2008.
doi:10.1016/j.metmat.2008.09.001
18. Pozar, D. M., Microwave Engineering, 3rd Edition, Wiley, USA, 2005.
19. Poularikas, A. D., Handbook of Formulas and Tables for Signal Processing, CRC Press LLC, 1999.