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An efficient discontinuous Galerkin time-domain (DGTD) method with an implementation of generalized periodic boundary conditions (PBCs) is proposed to analyze the electromagnetic scattering from arbitrary skewed periodic structures. The transformed field variable approach and the discontinuous Galerkin technique with nonconformal mesh are presented to implement the generalized PBCs for arbitrary skewed periodic structures under both normally and obliquely incident illuminations. The arbitrary high-order time-stepping scheme, which retains the DGTD feature of high-order accuracy and breaks the Butcher barrier, is extended to a transformed version of Maxwell’s equations introduced by the generalized PBCs implementation. The proposed method enables an efficient modeling of arbitrary skewed arrays with a fixed unit-cell mesh. Numerical examples for skewed periodic structures, such as an infinite gold film, 1-D and 2-D staggered dipole frequency-selective surfaces (FSSs), mechanically reconfigurable FSSs, and skewed nanohole arrays, are presented to demonstrate the accuracy and applicability of the proposed method. [ABSTRACT FROM AUTHOR]

A method is presented that allows for the efficient design of capacitively loaded finite-size electromagnetic bandgap (EBG) structures, which can target a wide range of design objectives. The design flexibility is achieved by adding arbitrary nonuniform capacitive loading to an underlying periodic EBG structure. This system can be interpreted as having an effective aperiodic structure, which allows more design flexibility in terms of bandgap engineering. To choose the proper capacitances, a powerful global optimization technique known as the covariance matrix adaptation evolutionary strategy is employed that is aided by a fast port-reduction strategy. This approach avoids the need to carry out multiple computationally expensive full-wave simulations during the course of the optimization process by requiring only a single full-wave simulation be performed prior to initiating the optimization. To demonstrate the utility of this method, the capacitive loading of a mushroom-type EBG structure in a parallel-plate waveguide is optimized to reduce transmission from 2.4 to 7 GHz. This design was fabricated and the measured response was found to be in good agreement with the simulations. Using the same initial full-wave simulation, another structure was designed to improve isolation at the 2.4-, 3.6-, and 5-GHz WLAN bands to below -\22 dB. An additional set of structures are also designed using capacitively loaded mushroom-type EBG surfaces without placing them inside of a parallel-plate waveguide. [ABSTRACT FROM AUTHOR]