This Letter proposes a novel balanced triple-mode substrate integrated waveguide (SIW) bandpass filter for the first time. The new triplemode resonator is realised by a square-shaped SIW cavity with a capacitive loading patch. The resonance of higher-order mode TE 301 can be controlled and shifted to that of modes TE 102 and TE 201. High-performance common mode suppression, controllable bandwidth, compact size and quasi-elliptic differential mode response can be achieved. For demonstration, a balanced triple-mode SIW filter is designed, fabricated and measured.
This study reports a multi‐layered dual‐mode substrate integrated waveguide (SIW) bandpass filter (BPF), in which the input and output ports are located on the same substrate layer (i.e. the upper one). The dual‐mode SIW cavity in the lower substrate layer is coupled to the upper dual‐mode SIW cavity by two crossed slots, which can independently control the inter‐couplings. The proposed filter can be modelled by a dual‐extended doublet coupling scheme with considering bypass couplings between source and load. Based on the proposed structure, single‐ and dual‐band filtering responses with four controllable finite‐transmission zeros (FTZs) are realised and analysed. For the demonstration, a single‐band filter and a dual‐band filter were fabricated and measured. The measured results agree well with simulated ones.
Here, three fourth‐order bandpass filters (BPFs) in modified box‐section schemes using substrate integrated waveguide (SIW) are proposed and researched. The proposed filters are based on a conventional box‐section structure with considering bypass/constant/frequency‐dependent coupling (FDC) in the diagonal cross‐coupling path to construct new filtering responses. Based on the different type of the cross‐coupling path, the frequency response of each proposed structure is analysed and presented, which indicates that the proposed filters have flexible response in terms of finite transmission zeros (FTZs). The proposed filters can realise generalised Chebyshev responses with one/two/three FTZs at arbitrary positions. Moreover, one FTZ may be produced by using bypass coupling and direct inductive coupling window to improve lower stopband performance, which is verified by a coupling matrix. For the demonstration, three quasi‐elliptic response filters were designed, fabricated, and measured. Good agreement is achieved between simulated and measured results.
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