A Compact Quarter-Mode (QM) and Eighth-Mode (EM) Substrate Integrated Waveguide (SIW) Filter

This paper proposes a quarter-mode (QM) and eighth-mode (EM) substrate integrated waveguide (SIW) filter based on silicon substrate. Firstly, using the theory of slotting on one side of the SIW resonator, a quarter-mode and an eighth-mode resonator can be obtained, which can greatly reduce the device size. Secondly, the input and output feeders are located at the position where the electric field is the strongest, which adopts the electrical coupling of the filter. The electromagnetic hybrid coupling between the two resonators makes the filter add a transmission zero (TZ) out of band, which enhances the selectivity of the filter. Under the above theory, the filter is composed of two resonators with the center frequency 10.7 GHz, the bandwidth is 3.8 GHz, the insertion loss is -0.7 dB, the in-band return loss is less than -15 dB, and the whole size is 5.65 mm×5.9 mm, which is very compact.