Abstract
This work studies the propagation characteristics of a rectangular waveguide with aligned/misaligned double-sided dielectric-filled metallic corrugations. Two modes are found to propagate in the proposed double-sided configuration below the hollow-waveguide cutoff frequency: a quasi-resonant mode and a backward mode. This is in contrast to the single-sided configuration, which only allows for backward propagation. Moreover, the double-sided configuration can be of interest for waveguide miniaturization on account of the broader band of its backward mode. The width of the stopband between the quasi-resonant and backward modes can be controlled by the misalignment of the top and bottom corrugations, being null for the glide-symmetric case. The previous study is complemented with numerical results showing the impact of the height of the corrugations, as well as the filling dielectric permittivity, on the bandwidth and location of the appearing negative-effective-permeability band. The multi-modal transmission-matrix method has also been employed to estimate the rejection level and material losses in the structure and to determine which port modes are associated with the quasi-resonant and backward modes. Finally, it is shown that glide symmetry can advantageously be used to reduce the dispersion and broadens the operating band of the modes.
Highlights
Rectangular metallic waveguides are among the first employed microwave transmission systems [1]
In [6,7,8,9], it was demonstrated that a hollow waveguide with dielectric-filled periodic corrugations on the bottom wall allows the propagation of backward modes
No significant difference was found in these computations since no coupling between the chosen port modes is appreciated. For both the mirror and glide-symmetric waveguides, when the input/output waveguide port mode is the TE10, the application of the Multi-Modal Transmission-Matrix Method (MMTMM) gives us the dispersion diagrams of the first two modes that propagate below the hollow-waveguide cutoff frequency, with the third mode being analogous to TE10 of the hollow waveguide
Summary
Rectangular metallic waveguides are among the first employed microwave transmission systems [1]. It has been found that glide symmetry reduces the dispersion of the first propagating mode in metasurfaces, as well as increases its equivalent refractive index [14] These properties are useful in the design of lenses, such as the Luneburg [15] and Maxwell fish-eye lens [16], and low-dispersive leaky-wave antennas [17]. In order to fundamentally understand the operation of the double-sided corrugated waveguides, we make use of the Multi-Modal Transmission-Matrix Method (MMTMM) [24] This method has been used to characterize the propagation properties of periodic structures [25,26], including glide symmetry [27]. With this method, we can evaluate the port modes that contribute to each propagating mode, and we can simulate any arbitrary configuration of corrugations
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