Band-Stop Filter Based on Glide-Symmetric Substrate-Integrated Coaxial Lines for Band-Gap Control and Bandwidth Customization

Band-stop filters play an important role in wireless communications by blocking signals within specified frequency bands and allowing useful frequencies to pass through. As a special type of higher symmetry, glide symmetry achieves the reconfiguration of band gaps by manipulating the dispersion relationships of periodic structures, which is of great value for filter designs. However, existing band-stop filters based on glide symmetry are mainly realized with three-dimensional transmission lines, and only one band gap is reconfigured. Here, we explore glide symmetry in planar substrate-integrated coaxial lines (SICL) to reconfigure multiple band gaps and, in the meantime, customize their bandwidths and locations. For practical applications, three types of SICL band-stop filters with different glide symmetries are designed, fabricated, and measured. By changing the geometry of the glide-symmetric inner conductor, two distinct stopbands can be reconfigured and their bandwidths can be customized. The measurement results agree well with the numerical results, demonstrating high controllability and good filtering performance. The proposed glide-symmetric SICL provides a facile method to implement controllable band-stop filters and may facilitate more planar implementations with glide symmetry for dispersion manipulations.