Coupling topology of substrate integrated waveguide filter using unequal length slots with non-resonating nodes

摘要

A novel coupling topology of substrate integrated waveguide filter with unequal-length slots is proposed. This filter consists of two resonators and a pair of unequal-length slots, which can be considered as two-stage bypass coupling resonators. There exist two resonant modes (TE101 and TE102) in each resonator. TE101 mode is coupled by the long slot, and TE102 mode is coupled by the short slot, which can achieve two resonant modes couplings between adjacent cavities. This structure uses TE102 mode to design the centre frequency of the passband and regards TE101 mode as spurious response. As a result, this filter leads to three transmission zeros (TZs), two TZs locate above the passband and one TZ is below the passband. The filter is fabricated and measured, the measured results agree well with simulated ones.