Capacitively loaded resonator for compact substrate integrated waveguide filters

This paper presents a novel topology for the design of compact coupled resonator filters based on SIW technology. A capacitive post has been inserted at the center of the SIW cavity resonator. The presence of this conducting post enables an important reduction of the f₀ of the resonator with small absolute increases of the substrate height. A compact X-band 3-pole 2% fractional bandwidth Chebyshev filter has been designed and fabricated in a standard PCB process. The filter performance is similar to a conventional SIW design but the size is significantly reduced.