Multiple Stacks of Rotated Metal Strip Gratings for High-Gain Bandwidth Enhancement and Gain Control of Overlying Dipoles—Analysis by Asymptotic Strips Boundary Conditions

As an amenable and efficient alternative to formulaically cumbersome and computationally demanding full-wave modal approaches, the herein analytical method uses the asymptotic strips boundary conditions along with classical vector potentials and coordinate transformations to treat multiple stacks of rotated metal strip gratings with general dielectric layers between them. For all cases, either with conducting terminal planes on just one side, on both, or none at all, solutions to plane-wave illuminated and/or modal dispersion eigenvalue problems are all obtainable. With the additional degrees of parametric freedom afforded by the angles of rotation between gratings, not only may wider ranges of special properties such as artificial surface impedances be achieved at fixed frequencies, they can also be reconfigured by the rotation of the gratings, being a simple, single-sweep-type mechanical motion, as opposed to electronic means entailing complex networks and intricate circuitries. In addition to the presentation of the formulation details and validation results, this article demonstrates the importance of multiple stacks of rotated strip gratings in widening the otherwise compromised bandwidths of artificial magnetic conductor (AMC) surface characteristics subjected to strict reflection-phase criterion for preserving high maximal broadside gains of overlying prostrate dipole antennas as well as attaining full-range gain control. Prototypes are manufactured and measured with a good agreement with theory.