Stopband improvement of substrate integrated waveguide filters using slotted ground structures

In this paper, an slotted ground structure (SGS) in substrate integrated waveguide (SIW) topologies is investigated. A cascade connection of these structures is used to improve the stopband performance of SIW filters. First, the second longitudinal resonant modes of an SIW filter are suppressed and shifted down by inserting radiating slots at the proper positions of cavities. Then four cells of SGS are adopted at the ground plane of the both input and output feed lines of the filter to reject the undesired passbands and efficiently improve the spurious responses. Analysis of the results verifies the effectiveness of the proposed configuration.