A dual-band bandpass filter with substrate integrated waveguide-to-folded defected ground structure split ring resonator unit

A unit based on substrate integrated waveguide (SIW) cavity with folded defected ground structure (FDGS) split-ring resonator (SRR) etched on is introduced. The coupling between the SIW cavity and FDGS leads to two resonant frequencies and one transmission zero. By adjusting the size and the position of the FDGS SRR, both resonant frequencies and transmission zero can be controlled. The flexibility of the unit is fully used to design a dual-band bandpass filter with compact size by simply cascading two units. The measured S-parameters agree well with the simulated ones.