A sixth‐order SIW bandpass filter based on combining single‐ and dual‐mode cavities with high selectivity at Ka‐band

Abstract

In this paper, a novel substrate integrated waveguide quasi‐elliptic bandpass filter is proposed by combining single‐ and dual‐mode cavities. Two single‐mode cavities with TE101 mode are directly coupled to the dual‐mode resonance cavity which employs a pair of disturbing metallic via‐holes to make the resonant points of TE101 and TE102 mode in one passband. Based on the conventional box‐like topology, two additional single cavities are used to achieve wider bandwidth and simplify the design difficulty. In addition to two transmission zeros (TZs) realized by the cross‐coupling technology, nonreasoning node will generate an additional TZ at a higher frequency to improve the upper stopband performance. Finally, a sixth‐order filter, having the passband frequency of 24.25–27.5 GHz for 5G application, with three TZs, is simulated, fabricated and measured to demonstrate and verify the proposed structure. The test results show the insertion loss is 1.7 and 3 dB bandwidth is 3.37 GHz. The three TZs improve out of band rejection of the filter.

Design of Cross-Coupled Bandpass Filters with Flexible Coupling via Half-Mode Substrate-Integrated Waveguide

“…Besides, in [2], although the SIWs are constructed in the same layer, an embedded short-ended strip line is adopted, and thus, the two-layer printed circuit board (PCB) process is also needed. To obtain negative coupling with the traditional single-layer PCB technique, a lot of coupling structures are put forward, such as coplanar lines [3], [4], interdigital slot-line (ISL) [5], shorted coplanar waveguide (CPW) [6], coupled stepped-impedance grounded CPWs (SIGCPWs) [7], H-shaped slot [8] or ring gap [9,10] with shorted posts, a balanced microstrip line with a pair of plated through-holes [11,12], and interdigital-like capacitive coupling structure [13]. However, these coupling structures are functioned together with the postwall iris which will complicate the coupling structure.…”

Two‐dimensional multichannel bandpass filter bank with improved fractional bandwidth and selectivity

“…As a result, many BPFs are rapidly becoming a requirement in many radio frequency devices, as they aid in consolidating more hardware into single or fewer units 1 . For example, a multichannel BPF with multiple input and output signals of the same operating frequency and bandwidth has been realized using a method based on “cubic tri‐mode dielectric‐loaded cavities.” 2 Furthermore, because of its tolerance to high power, lower insertion loss, and compatibility, substrate‐integrated waveguide (SIW) technology has been used in several recent designs of microwave and millimeter‐wave devices 3–9 . To meet the demands and technological standards, much attention has been focused on designing many filtering channels using the SIW.…”

“…2 Furthermore, because of its tolerance to high power, lower insertion loss, and compatibility, substrateintegrated waveguide (SIW) technology has been used in several recent designs of microwave and millimeter-wave devices. [3][4][5][6][7][8][9] To meet the demands and technological standards, much attention has been focused on designing many filtering channels using the SIW. To investigate the benefits of multichannel BPF, a five-channel filtering crossover was reported, 10 which exploited the tendencies of specified "frequency flexibility" for two separate frequency bands and "quadruple mode in a single cavity."…”