Passband broadening of sub-wavelength resonator-based glide-symmetric SIW filters
Here, we discuss the virtues of glide symmetry for designing low-frequency band-pass periodic filters insubstrate integrated waveguide (SIW) technology based on complementary split-ring resonators (CSRRs).Conventional (non-glide) versions of these filters have a narrow passband, due to the fact that this band isbelow the cutoff frequency of the background waveguide. When glide symmetry is added to the filterconfiguration, the low-frequency passband is significantly widened, as well as the first stopband. The dis-persion properties of both conventional and glide-symmetric periodically loaded waveguides are ana-lyzed and compared with commercial software and an equivalent circuit model. Finally, twoprototypes of the proposed glide-symmetric structure have been designed and built, illustrating thepotential of this technique to widen the passband and reduce insertion losses of conventional sub-wavelength CSRR-loaded SIW filters.