A graded material structure is optimized for broadband radome application by using hybrid method in this paper. In the optimization, dynamic range ratio (DRR) of real permittivity and loss of material are taken into considerations. By using an analytical function, the optimization problem with the DRR constraint is converted to an unconstrained problem. The proposed hybrid method is a combination of trust region method (TRM) and genetic algorithm (GA). Firstly (TRM) is applied to optimize the dielectric constant distribution. Then the result of TRM is used as initial value of GA. GA is employed to improve the global property of the results provided by TRM. Because TRM has the advantage of fast searching speed and GA has the advantage of global property, the hybrid method has the feature of fast convergence speed. And the jitter property of GA permittivity distribution is moderated. The effectiveness of the hybrid is validated through the designs of two broadband radome walls. The minimum power transmission efficiency is 81.9% ranging from 1 GHz to 18 GHz for normal incidence.
2. Meng, H. F. and W.-B. Dou, "A hybrid method for the analysis of radome-enclosed horn antenna," Progress In Electromagnetics Research, Vol. 90, 219-233, 2009.
3. Vegni, L. and A. Toscano, "Full-wave analysis of planar stratified with inhomogeneous layers," IEEE Trans. Antennas Propag., Vol. 48, No. 4, 631-633, 2000.
4. Nair, R. U., M. Suprava, and R. M. Jha, "Graded dielectric inhomogeneous streamlined radome for airborne applications," Electronics Lett., Vol. 51, No. 11, 862-863, 2015.
5. Nair, R. U. and R. M. Jha, "Electromagnetic design and performance analysis of airborne radomes: Trends and perspectives," IEEE Antennas and Propag. Magazine, Vol. 56, No. 4, 276-298, 2014.
6. Philippe, A. E., "Reflection and transmission of radio waves at a dielectric slab with variable permittivity," IEEE Trans. Antennas Propag., Vol. 21, No. 2, 234-236, 1973.
7. Nair, R. U., S. Shashidhara, and R. M. Jha, "Novel inhomogeneous planar layer radome design for airborne applications," IEEE Antennas Wirel. Propag. Lett., Vol. 11, 854-856, 2012.
8. Bilotti, F., A. Toscano, and L. Vegni, "Very fast design formulas for microwave nonhomogeneous media filters," Microw. Opt. Tech. Lett., Vol. 22, No. 3, 218-221, 1999.
9. Toscano, A., L. Vegni, and F. Bilotti, "A new efficient method of analysis for inhomogeneous media shields and filters," IEEE Trans. Electromagn. Compat., Vol. 43, No. 3, 394-399, 2001.
10. Chen, F., Q. Shen, and L. Zhang, "Electromagnetic optimal design and preparation of broadband ceramic radome material with graded porous structure," Progress In Electromagnetics Research, Vol. 105, 445-461, 2010.
11. Zhou, L., Y. Pei, R. Zhang, and D. Fang, "Optimal design for high-temperature broadband radome wall with symmetrical graded porous structure," Progress In Electromagnetics Research, Vol. 127, 1-14, 2012.
12. Venkatarayalu, N. V., T. Ray, and Y. B. Gan, "Multi-layer dielectric filter design using a multiobjective evolutionary algorithm," IEEE Trans. Antennas Propag., Vol. 53, No. 11, 3625-3632, 2005.
13. Amirhosseini, M. K., "Wideband flat radomes using inhomogeneous planar layers," International Journal of Antennas and Propagation, Vol. 2008, 1-6, 2008.
14. Higham, D. J., "Trust region algorithms and time step selection," SIAM Journal of Numerical Analysis, Vol. 37, No. 1, 194-210, 1999.
15. Goldberg, D. E., Genetic Algorithms in Search, Optimization & Machine Learning, Addison-Wesley, Netherlands, 1989.
16. Deb, K., A. Pratap, S. Agarwal, and T. Meyarivan, "A fast and elitist multiobjective genetic algorithm: NSGA-II," IEEE Trans. on Evolutionary Computation, Vol. 6, No. 2, 182-197, 2002.
17. Kong, J. A., Electromagnetic Wave Theory, John Wiley & Sons Inc., New York, 1986.
18. Khalaj-Amirhosseini, M., "Analysis of lossy inhomogeneous planar layers using finite difference method," Progress In Electromagnetics Research, Vol. 59, 187-198, 2006.
19. Zarifi, D., M. Soleimani, and A. Abdolali, "State transition matrix of inhomogeneous planar layers," IET Microw., Antennas & Propag., Vol. 9, No. 4, 301-306, 2015.
20. Kuester, E. F. and C. L. Holloway, "A low-frequency model for wedge or pyramid absorber arrays-I: Theory," IEEE Trans. Electromagn. Compat., Vol. 36, No. 4, 300-306, 1994.
21. Garnett, J. C. M., "Colors in metal glasses and metal films," Trans. Roy. Soc., Vol. 53, 385-420, 1904.
22. Karkkainen, K. K. A. H., Sihvola, and K. I. Nikoskinen, "Effective permittivity of mixtures: Numerical validation by the FDTD method," IEEE Trans. on Geoscience and Remote Sensing, Vol. 38, 1303-1308, 2000.
23. Jebbor, N. and B. Seddik, "Effective permittivity of periodic campsite material: Numerical modeling by the finite element method," Journal of Electrostatics, Vol. 70, 393-399, 2012.