Compact cross‐coupled filters based on isosceles right triangular and equilateral triangular SIW cavities

Abstract

Two kinds of classical triangular metric resonant cavities including the isosceles right triangular and equilateral triangular metric cavities are investigated carefully. A comprehensive and rigorous derivation process of these two resonant cavities is proposed. Based on this, the mode function and the transverse field components for the modes in the triangular substrate‐integrated waveguide (SIW) cavities can be provided. Then the resonant frequency of both kinds of triangular SIW cavities can be calculated. Combined it with the coupling matrix, a fourth‐degree filter implemented of isosceles right triangular SIW cavities and a sixth‐degree filter formed by equilateral triangular SIW cavities are designed, fabricated and measured in detail. The measured results are in line with the simulated ones. The frequency responses of both filters show a pair of transmission zeroes at each side of the pass band due to the cross‐coupling structure. It also verifies the validity of the derivation in this study. Compared with the rectangular and circular resonant ones, the construct of the triangular cavity has the advantage of much more compact. Besides, the proposed filters based on the triangular cavity also have their own advantages of low cost, good selectivity and easy integration with other planar circuits.

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

“…Different from etching CRSS or designing multilayer structures in Refs. [17,18] to realize and control FTZs. In our design, the first FTZ is produced by the coupling scheme with source‐load (S‐L) coupling, which is realised by the non‐resonant modes (i.e.…”

“…In Ref. [17], a fourth‐degree and a sixth‐degree BPFs based on isosceles right‐angled triangular (IRT) and ET SIW cavities are implemented, respectively, according to the calculation formula of the resonant frequency. However, only the fundamental mode of these cavities has been analysed and utilised to design single‐band BPFs.…”

Compact bandpass filter based on single isosceles right triangular substrate integrated waveguide cavity and modified complementary compact microstrip resonant cell

“…The field distribution of triangular SIW cavity is shown in Fig. 2, and the resonant frequency 0 in this mode can be calculated using the following relation [25], which is IEICE Electronics Express, Vol.VV, No.NN, 1-5 different from the rectangular SIW cavity.…”

Compact dual‐layer substrate‐integrated waveguide bandpass filters with controllable transmission zeros

“…The IRTSIW cavity is analysed in detail in Ref. [31]. Two IRTSIW cavities are designed in the upper substrate, and the length of the cavity is denoted by L 1 .…”