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.
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