Abstract-This paper presents two novel bandpass filters using sixteenth mode substrate integrated waveguide (SMSIW) and thirty-second mode SIW (TMSIW) cavities, respectively. The overall size of SMSIW and TMSIW cavities can be reduced by a factor of 15/16 and 31/32 in comparison to the filters designed in the conventional SIW resonator, while keeping almost the same resonant frequency. Based on SMSIW cavity, a first-order filter with the center frequency of 2.45 GHz and a transmission zero (TZ) located at the upper-stopband is proposed. The second-order TMSIW cavity filter exhibits one TZ at the lower-stopband and two TZs at the upper-stopband, and it has a better performance of the passband than the former with the same size and center frequency. It also has a wider upper-stopband with suppression of an unwanted harmonic at 7.6 GHz. Two intersecting rectangular slots are etched between the two cavities with a smaller angle between them of 30 degrees. The whole size of the filter is 24.2 mm × 29.1 mm × 0.508 mm. The filters are fabricated in SIW technology, and the frequency response shows good agreement between simulated and measured results.
Abstract-This paper presents a C-band wide stopband bandpass filter (BPF) using quarter mode substrate integrated waveguide (QMSIW) cavities. The BPF is simply constructed by combining Sshaped slot and L-shaped slot loaded quarter-mode substrate integrated waveguide. A special negative coupling scheme with symmetrical S-shaped slots on the top and bottom metal planes connected by metallic vias is developed. The proposed structure provides more design flexibility in arranging the pitch of vias owing to the extended slot length. The filter has fractional bandwidth of 25% at center frequency of 5.5 GHz with return loss better than 24 dB and insertion loss less than 1.1 dB. Moreover, its first spurious response occurs at 22.5 GHz (about four times the central frequency), exhibiting an extremely wide stopband performance. An experimental SIW filter was fabricated, and good agreement was achieved between the simulated and measured results.
This paper presents two novel substrate integrated waveguide (SIW) diplexers with transmission zeros placed below and above the passband. Diplexer I is based on two bandpass filters (BPFs) using eighth mode SIW (EMSIW) cavities with Rx and Tx frequencies at 3.68 GHz and 6.09 GHz. The second one is operated at 2.37 GHz and 6.04 GHz using EMSIW and thirty-second SIW (TMSIW) cavity. The diplexers are all combined through a T-junction by carefully choosing the length and width of two branches to allow each filter to match the antenna, while maintaining an open circuit at the middle band of the other. The proposed diplexers possess compact size, because of the EMSIW and TMSIW cavity. The diplexers are fabricated in SIW technology. The minimum insertion losses including SMA connectors are measured to be 1.39/1.61 dB and 0.38/0.85 dB. Meanwhile, the diplexers exhibit 37 dB and 42 dB isolations between the channels, respectively. Good agreement is achieved between simulated and measured results.
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