Modeling and implementation of perforated SIW filters

A novel class of substrate integrated waveguide (SIW) filters is presented in this paper. The filters are based on the perforation of the dielectric substrate, which generates the local modification of the effective dielectric permittivity and, consequently, of the characteristic impedance of the waveguide. In particular, perforations are used to obtain a waveguide section below cutoff in the filter band. The waveguide sections below cutoff are exploited to realize the impedance inverters, which in turn connect resonators obtained by half-wave (not perforated) SIW sections. The impedance inverter has been investigated and a filter has been designed and fabricated to demonstrate the feasibility of the proposed method.