Single‐ and triple‐band bandpass filters using novel perturbed isosceles right‐angled triangular SIW cavities

Abstract

Herein, a rigorous derivation of an isosceles right‐angled triangular (IRT) metallic cavity is analysed. Then, the transverse field components in the IRT substrate‐integrated waveguide (SIW) cavity are derived, and the expression of the resonant frequencies can also be obtained. Then, a novel perturbed IRT SIW cavity is proposed, which is based on the characteristics of resonant modes in IRT SIW cavity and the capacitive‐loading technique. Three prototypes were designed to verify the validity of the derivation and analysis in this study. First, a dual‐mode single passband filter was implemented using the perturbed modes TE102 and TE202. Next, two tri‐mode triple‐band bandpass filters (BPFs) using the perturbed modes TE101, TE102 and TE202 are proposed, synthesised, verified and measured for demonstration, including a second‐order direct‐coupled one which operates at 8.02, 11.44 and 12.52 GHz, and a fourth‐order direct‐coupled one which operates at 7.7, 11.0 and 12.1 GHZ. The measured curves agree well with the simulated ones. Very compact circuit sizes and excellent filtering performances have been achieved for the three prototypes.

A compact tri‐band filter based on a dual‐capacitively loaded triple‐mode substrate integrated waveguide resonator

“…Table 1 compares the performance of the proposed filter with other tri‐band filters. The proposed tri‐band filter achieves much size reduction than Zhang and colleagues 1 , 4–8 2 and Iqbal et al 3 achieve better miniaturization than our work.…”

“…The proposed tri-band filter achieves much size reduction than Zhang and colleagues. 1,[4][5][6][7][8] Filters in Zhang et al 2 and Iqbal et al 3 achieve better miniaturization than our work. However, the filters in Zhang et al 2 and Iqbal et al 3 are not suitable for millimeter wave implementations and 3D-integrated systems, for the lacking of EM-shield capability and use of lumped capacitors.…”

“…Etching slots, loading inductive posts, and loading capacitive structure are three main methods to realize the mode control of MMRs. [1][2][3][4][5][6][7][8] In Zhang et al, 1,2 tri-band filters are designed based on complementary split ring resonators loaded SIW cavity. However, the slots etching on the surface of SIW may cause significant radiation loss and thus the circuit is suitable only for lower microwave frequencies.…”

“…Multimode resonators (MMRs) have gained a considerable amount of research interest owing to their compact size in designing multiband SIW filters. Etching slots, loading inductive posts, and loading capacitive structure are three main methods to realize the mode control of MMRs 1–8 . In Zhang et al, 1 , 2 tri‐band filters are designed based on complementary split ring resonators loaded SIW cavity.…”

Substrate Integrated Waveguide Multiband Bandpass Filters and Multiplexers: Current Status and Future Outlook

“…10(b). To successfully implement this kind of advanced filtering devices, the first three modes were fully exploited and utilized based on various triple-mode coupled cavities, such as perturbed SIW square [80] or circular [81] cavities, slots-loaded quartermode SIW circular cavities [82], fan-shaped SIW cavities [83], patches-loaded SIW evanescent-mode cavities [84], isosceles right-angled SIW triangular cavities [85], and so forth. Nevertheless, it is generally a tough task to freely control the multimode frequencies and couplings in practice, leading to inflexible CFs and bandwidths of the multiple channels/passbands.…”