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 S-shaped 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.
2. Uchimura, H., T. Takenoshita, and M. Fujii, "Development of a laminated waveguide," IEEE Trans. Microw. Theory Tech., Vol. 46, No. 12, 2438-2443, Dec. 1998.
3. Deslandes, D. and K. Wu, "Integration microstrip and rectangular wave-guide in planar form," IEEE Microw. Wireless Compon. Lett., Vol. 11, No. 2, 68-70, Feb. 2001.
4. Che, W., L. Geng, K. Deng, and Y. L. Chow, "Analysis and experiment of compact folded substrateintegrate waveguide," IEEE Trans. Microw. Theory Tech., Vol. 56, No. 1, 88-93, Jan. 2008.
5. Zhang, Q.-L., B.-Z. Wang, D.-S. Zhao, and K. Wu, "A compact half-mode substrate integrated waveguide bandpass filter with wide out-of-band rejection," IEEE Microw. Wireless Compon. Lett., Vol. 26, No. 7, 501-503, Jul. 2016.
6. Yang, T., P. Chi, R. Xu, and W. Lin, "Folded substrate integrated waveguide based composite right/left handed transmission line and its application to partial H-plane filters," IEEE Trans. Microw. Theory Tech., Vol. 61, No. 2, 789-799, Feb. 2013.
7. Guo, Z., K.-S. Chin, W. Che, and C.-C. Chang, "Cross-coupled bandpass filters using QMSIW cavities and S-shaped slot coupling structures," Journal of Electromagnetic Waves and Applications, Vol. 27, No. 2, 160-167, Jan. 2013.
8. Zhu, F., W. Hong, J. Chen, and K. Wu, "Wide stopband substrate integrated waveguide filter using corner cavities," Electron. Lett., Vol. 49, No. 1, 50-52, Jan. 2013.
9. Lan, S.-W., M.-H. Weng, C.-Y. Huang, and S.-J. Chang, "Design of a compact ultra-wideband bandpass filter with an extremely broad stopband region," IEEE Microw. Wireless Compon. Lett., Vol. 26, No. 6, 392-394, Jun. 2016.
10. Zhang, X. Y., X. Dai, H.-L. Kao, B.-H. Wei, Z. Y. Cai, and Q. Xue, "Compact LTCC bandpass filter with wide stopband using discriminating coupling," IEEE Trans. Compon., Packag. Manuf. Technol., Vol. 4, No. 4, 656-663, Apr. 2014.