Compact, dual‐band, and hybrid filter based on combline and substrate integrated waveguide resonators

Abstract

A novel compact hybrid dual‐band bandpass filter based on combline and substrate integrated waveguide (SIW) resonators is proposed. By exploring an SIW‐based hybrid cavity structure, a controllable dual‐band response is achieved. The low‐frequency passband is obtained by the combline, or mushroom resonators and the high‐frequency passband is formed by the TE101 and TE301 modes. Unlike other designs that use the main mode and the high‐order mode of the same resonator, we innovative use the TE301 mode of the rectangular cavity and cleverly divide this rectangular cavity into two small cavities, and use its TE101 mode to form the second passband with the TE301 mode of the large cavity. To improve the selectivity and out‐of‐band suppression, three transmission zeros are configured in this design. In order to verify the proposed design concept, a compact dual‐band filter using this hybrid resonance structure is fabricated and measured. It demonstrates good filtering performance, including a compact size of 0.45 × 1.09 λ0, a low insertion loss of 0.57 and 1.67 dB in the two bands, and a high‐design flexibility.

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

“…In [57], [58], [59], the feeding ports were shared by two channels either made of two independent SIW single-band BPFs to realize a balanced diplexer [57], or one microstrip and one SIW BPFs [58] even two coaxial SIW doublets [59] to implement SIW dual-band BPFs. In [60] and [61], balanced and single-ended SIW dual-band BPFs were demonstrated with one of the passbands dominated by fundamental SIW cavities and the other passband built by coupled CSRRs [60] or combline resonators [61]. This type of mixed-mode techniques can significantly reduce the circuit sizes while adding additional design degrees of freedom to ease the control of the CFs and bandwidths of multiple channels/passbands.…”

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

“…On the other hand, dual-band BPFs are in high demand [14,15]. To form one more operating passband, more resonances are necessary, and thus, a few effective methods have been put forward.…”

Compact and Hybrid Dual-Band Bandpass Filter Using Folded Multimode Resonators and Second-Mode Suppression

“…Although this strategy can yield compact structures, it is generally hard to control the passbands and stopbands originating from the different modes independently. Finally, hybrid structures have been suggested, which merge the advantages of SIW-based cavity filters with other technologies, such as microstrips, slotlines, or coplanar waveguides (CPWs) [18,[49][50][51][52][53][54][55]. These hybrid filter topologies provide greater design flexibility while maintaining a compact size.…”