Ferrite-loaded substrate integrated waveguide frequency-agile bandpass filter

In this paper, a new ferrite-loaded substrate integrated waveguide (SIW) frequency tunable bandpass filter is presented. Two ferrite slabs are loaded in the sidewall of a substrate integrated waveguide. When a DC magnetic bias is applied to the ferrite slabs, the equivalent width of the ferrite-loaded SIW is changed, which contributes to the tuning ability. Then, an inductive post bandpass filter is designed based on this theory. Its operating frequency can be adjusted from 12.5 GHz to 13.4 GHz. Within this frequency range, an insertion loss of less than 1.6 dB and a return loss of better than 15 dB are achieved.