A compact slow-wave substrate integrated waveguide cavity filter

This paper describes a miniaturized substrate integrated waveguide (SIW) filter by considering slow-wave substrate integrated waveguides. Compared to conventional SIW, the proposed topology includes internal blind metalized via-holes connected to the bottom metalized layer. These via-holes tend to confine the electric field in the upper part, while the magnetic field remains present in the whole substrate. Thus, a slow-wave effect is obtained by the physical separation of electric and magnetic fields. Using this novel topology, a 5^th-order cavity filter centered at 11 GHz exhibiting a bandwidth of 900 MHz was designed, realized and measured. The filter surface area is more than three times smaller compared to classical SIW approaches. Measurements are in good agreement with simulations, validating the potential of the SW-SIW topology for RF and millimeter wave applications.