Triple‐mode dual‐band bandpass filter based on cross‐shaped substrate integrated waveguide

Abstract

A novel dual‐band bandpass filter based on substrate integrated waveguide (SIW) which is realised with mode distribution of the special cross‐shaped structure is presented in this Letter. In the cross‐shaped SIW, there are six symmetrically stimulated resonant modes in the first eight higher order resonant modes that are perturbed to achieve dual‐band responses, and each passband contains triple‐mode. By introducing 45° rotated cross via‐holes at the centre position of the structure, the two lower symmetrical resonant modes are closer to the unaffected asymmetrical higher resonant mode in both passbands. Compared with existing multimode multi‐band filters which are achieved by coupling or cascading mechanism, the presented filter design based on single cross‐shaped SIW is simple and easy for implementation. A prototype dual‐band filter operating at 8.23 and 11.48 GHz with 3 dB fractional bandwidths of 7.1 and 12.1% is designed and fabricated. Measured and simulated results are presented to validate the predicted performances of the proposed filter.

High‐selective triple‐mode SIW bandpass filter using higher‐order resonant modes

“…Introduction: Bandpass filters (BPFs) based on triple-mode substrate integrated waveguide (TMSIW) cavities have the merit of compact size, and thus they are studied recently [1][2][3][4][5][6][7][8][9]. The resonant frequency of the fundamental mode in a SIW cavity can be moved to the resonant frequencies of the first degenerate dual modes to produce a filtering passband, but the selectivity below the passband is poor because of no finite-transmission zero (FTZ) [1][2][3][4][5].…”

“…However, the unloaded quality (Q u ) factor of the proposed SIW cavity in [6] is not good enough. Except for the single-band TMSIW filters, TMSIW cavities are also employed to realise dual-and triple-band BPFs [7][8][9]. In [7,8] the first three resonant modes are used to produce three passbands, respectively.…”

“…In [7,8] the first three resonant modes are used to produce three passbands, respectively. In [9], triple-mode dual-band BPF using a cross-shaped SIW structure is proposed. To the best of our knowledge, only a few works of literature have reported SIW filters using higher-order resonant modes [9,10].…”

“…In [9], triple-mode dual-band BPF using a cross-shaped SIW structure is proposed. To the best of our knowledge, only a few works of literature have reported SIW filters using higher-order resonant modes [9,10]. In [9], the designed filter has the disadvantages of large size due to the cross-shaped SIW structure and poor selectivity due to only one FTZ.…”

“…To the best of our knowledge, only a few works of literature have reported SIW filters using higher-order resonant modes [9,10]. In [9], the designed filter has the disadvantages of large size due to the cross-shaped SIW structure and poor selectivity due to only one FTZ. In [10], only dual modes in a SIW cavity are used.…”