Cross-coupling on microstrip line for substrate integrated waveguide (SIW) quasi-elliptic bandpass filter

This paper proposed a quasi-elliptic bandpass filter on substrate integrated waveguide (SIW) cavity with cross-coupling structure using microstrip line. Etched slots on the SIW cavity are used to produce electric coupling between two adjacent SIW resonators, the cross-coupling is obtained by a microstrip-line with embedded stubs above the SIW cavity. By using cross-coupling and embedded stubs, a SIW filter is constituted with transmission zeros at both sides of the passband. Finally, a third-order SIW quasi-elliptic filter at 3.7GHz is designed and fabricated in a two-layer substrate. The measured results are found in good agreement with the simulated ones.