Abstract
The dispersion characteristics of a glide-symmetric holey periodic surface are investigated, with special emphasis on a detailed study of its stopbands. The unit cell is modeled as a multiport network associated with multiple modes at each of the lattice boundaries. Enforcing the periodic conditions, the real and imaginary parts of the wavenumbers of the Floquet modes are calculated through an eigenproblem posed in terms of the generalized multimodal transfer matrix, which is computed from the scattering parameters obtained with a full-wave simulator. This procedure allows us to take into account the higher order modal couplings between adjacent unit cells that are crucial for accurate dispersion analysis. The resulting simulation-assisted approach provides both a convenient computational tool and a very fruitful physical insight that reveals the existence of complex modes, the convergence of opposite-parity modes, and the anisotropy in both passband and stopband. This approach enables a precise calculation of the attenuation constant, which is not possible with conventional techniques as the eigenmode solvers of commercial software. Based on this approach, an extensive parametric study is carried out, rigorously establishing a set of critical criteria for the use of such a periodic surface as an electromagnetic bandgap structure in gap waveguide technology. Moreover, the analysis of the directional properties of the structure is applied to further suppress the leakage.
Highlights
A GLIDE-SYMMETRIC holey periodic surface is constructed in a narrow air gap formed by a parallel-plate waveguide (PPW), where the holes in its upper and Manuscript received April 30, 2020; revised July 4, 2020 and August 6, 2020; accepted August 25, 2020
A multimodal transfer matrix approach is employed in the Bloch analysis of the dispersion diagrams of a glide-symmetric holey metasurface
Glide symmetries were demonstrated to be able to reduce the dispersion of conventional periodic structures [1] and widen the bandwidth of electromagnetic bandgap (EBG) [12]
Summary
A GLIDE-SYMMETRIC holey periodic surface is constructed in a narrow air gap formed by a parallel-plate waveguide (PPW), where the holes in its upper and Manuscript received April 30, 2020; revised July 4, 2020 and August 6, 2020; accepted August 25, 2020. Color versions of one or more of the figures in this article are available online at https://ieeexplore.ieee.org. Glide-symmetric holey EBG presents a stopband whose bandwidth is substantially broader than its nonglide counterpart This fact has been widely validated by both a theoretical analysis using a mode-matching technique [10], [11] and experimentally [12], [13]. As explained in [15], the complex interactions between two surfaces bring difficulties to the equivalent homogenization process that is required by the transverse-resonance method widely used in conventional metasurfaces [16], [17] For this reason, the mode-matching technique is employed in [10], [11], and [18] for the Bloch analysis of both glide-symmetric corrugations and holey metasurfaces.
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