A high selective inline substrate integrated waveguide (SIW) filter based on novel stepped-impedance non-resonating node (NRN) is presented. The stepped-impedance NRN is realised by inserting a stepped-impedance substrate integrated coaxial line resonator into the volume of a third-order SIW filter. It introduces extra signal transmission path between source and load. Thus, one more transmission zero (TZ) is produced compared with conventional NRN that further improves the selectivity of the filter. Also, the proposed filter achieves a compact circuit size as the stepped-impedance NRN is embedded in the SIW cavity without occupying extra layout. To validate the proposed concept, a prototype filter with two TZs locating at both the lower and upper stop-bands, is designed, fabricated and measured. The measured results are well consistent with the simulation ones.
A quasi-elliptic function bandpass filter (BPF) based on parallel feed topology is presented. The parallel feed topology is realised by splitting the input/output port of the filter into two paths through a T-junction to excite a pair of resonators simultaneously. This configuration contributes to further improving the selectivity of the filter by introducing more transmission zeros (TZs) near the passband. In addition, a defected microstrip structure is utilised to enhance the out-band attenuation and spur suppression. In order to verify the proposed topology, a fourth order BPF with cross-coupling is designed, fabricated and measured. The measured frequency responses agree well with simulated ones. Four TZs can be obtained with two TZs on each side of the passband.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.