Analysis and Experiments of Compact Folded Substrate-Integrated Waveguide

The novel folded substrate-integrated waveguide (FSIW) is 50% narrower than the substrate-integrated waveguide, but both have similar propagation characteristics. This paper derives the analytical formulas of propagation and cutoff characteristics of the FSIW, as well as the formulas to calculate the width and gap of the central metal septum. Very good agreements (<2% error) are observed among the results of the theoretical formulas, numerical simulations, and hardware experiments over wide frequency and parameter ranges.