LAUSR

This Letter proposes a miniaturised filter that makes use of quarter-mode substrate-integrated waveguide (QMSIW) combining with a comb-line architecture for the first time. The comb-line QMSIW filter uses a periodic structure of distributed capacitance thereby reducing the size of the conventional QMSIW filter. To enhance out-of-band rejection, an S-shaped slot is introduced to realise negative coupling. Using the above principles, the size of this filter is reduced by nearly half (compared with conventional QMSIW filters) while having high out-of-band rejection. Finally, this planar, miniaturised filter is designed and fabricated. The measured results match well with simulated results.