Glide Symmetry to Prevent the Lowest Stopband of Printed Corrugated Transmission Lines

Abstract

In this letter, we demonstrate that the dispersion properties of printed double-sided parallel-strip lines can be controlled by using glide symmetry. Glide symmetry is introduced in with corrugations in both strips of a double-sided line. We demonstrate that glide symmetry eliminates the stopband between first and second propagating modes and yields to a higher propagation constant, preserving its linearity and the broadband nature of the underlying guiding technology. Thus, the glide-symmetric double-sided line can be designed to possess a high equivalent refractive index in an ultra-wide range of frequencies. These exceptional properties have been numerically and experimentally validated. Finally, we demonstrate the possibilities of this technology with a specific design, a glidesymmetric double-sided parallel-strip line with filtering properties. Potential applications are low-dispersive leaky wave antennas, electromechanical tunable phase shifters and filters.

Modeling of Glide-Symmetric Dielectric Structures

“…Periodic structures with higher symmetry were first studied in the 1960s and 1970s in relation to one-dimensional periodic waveguides [1][2][3]. Recent work on structures with higher symmetries (in both one and two dimensions) has demonstrated various effects and devices, such as ultra-wideband Luneburg lenses [4,5], leaky-wave antennas with low frequency dependency [6], cost-efficient gap waveguide technology [7,8], contactless flanges with low leakage [9], low-dispersive propagation in periodic structure-based transmission lines [10,11], and fully metallic reconfigurable filters and phase shifters [12]. These results were obtained using metallic structures, however, in many applications only dielectric types of materials are allowed.…”

Twist and Glide Symmetries for Helix Antenna Design and Miniaturization

“…Finally we illustrate here the effect of the breakage of the higher symmetry in the structure. The presence of the bandgap when the symmetry is broken is useful for filtering purposes [9]. Although this symmetry breakage can be introduced in different ways, here we only show the effect of one representative case that is depicted in Figure 6a.…”

“…Two commonly used higher symmetries are glide and twist symmetries as illustrated in Figure 1. While the extra spatial operator for glide symmetries is a mirroring with respect to a glide line/surface [9,10], for the twist symmetries the operator is a rotation along a twist axis [10][11][12]. Twist symmetry is a more general concept than glide symmetry.…”

“…In this manner, the leakage at the waveguide joint is avoided. Lastly, a recent work about the application of glide-symmetry in printed double-sided parallel-strip lines demonstrated the potential of glide symmetry to produce low dispersion transmission lines and filter behavior by breaking the symmetry [9]. Twist and glide symmetries were demonstrated to reduce the dispersion of metasurfaces, providing unit cells with a flattened frequency dependence.…”

Propagation characteristics of periodic structures possessing twist and polar glide symmetries

“…Moreover, purely periodic structures (i.e. non-glide) produce a stop-band at selected frequencies between the first and second modes [13,[17][18][19]. This stop-band is closed by applying glide symmetry, permitting the design of wideband flat metasurface lenses [20,21].…”