Multi‐layered dual‐mode substrate integrated waveguide bandpass filter with input and output ports located on same substrate layer

Abstract

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.

Compact single‐ and dual‐band bandpass filters with controllable transmission zeros using dual‐layer dual‐mode loop resonators

“…Since all coupling coefficients can be controlled well based on the proposed unbalanced loop filter, as shown in Fig. 3, the fourthorder filter can realise flexible responses in terms of four FTZs, which are similar to the frequency response characteristics based on the multilayer dual-mode SIW filter in [35]. Asymmetric frequency responses and quasi-elliptic linear-phase responses can also be designed based on the proposed unbalanced dual-layer dual-mode loop filter.…”

“…The dual-extended doublet coupling scheme with S-L coupling in Fig. 1b can realise fourth-order single-band filtering function with flexible responses, which has been presented and analysed in our previous work based on dual-mode substrate-integrated waveguide (SIW) structure [35]. Owing to the proposed unbalanced dual-layer dual-mode loop BPF has an S-L coupling, maximum number of FTZs can be realised [36].…”

“…extended coupling paths 1-3 and 2-4. Since the design processes of the proposed unbalanced dualmode loop filter are similar to the dual-mode SIW filter in [35] due to them associated with the same coupling schemes, the design processes are not repeated here.…”

“…The proposed dual-layer dual-mode loop filter can also realise split-type dual-band responses due to the dual-extended doublet coupling scheme and flexible controllable coupling coefficients [35,[38][39][40]. In this part, we focus on the analysis of the dual-band quasi-elliptic responses with controllable centre frequencies and bandwidths.…”

Dual-Mode Microstrip Patch Bandpass Filters With Generalized Frequency Responses

“…Besides, multiple-mode characteristics of patch resonators are studied to design size-reduced dual-band bandpass filters [19], [20]. However, bandwidth and center frequency can hardly be controlled independently The multilayer structure can provide an acceptable approach to realize high-performance bandpass filters, including substrate integrated waveguide filters [21]- [23] and microstrip patch filters [24], [25]. To our best knowledge, there are only a few literatures that report multilayer patch filters [24], [25].…”