This paper presents two size-miniaturized quarter mode (QM) and eighth mode (EM) substrate integrated waveguide (SIW) bandpass filters (BPFs), which are embedded with a novel frequency-dependent coupling (FDC) structure. The proposed FDC is implemented as a composition of balanced folding lines and inductive iris. One additional transmission zero (TZ) introduced by FDC between two cavities leads to higher frequency selectivity and better out-of-band rejection. Higher order modes suppression appears by combining the loaded paired open stubs on feeder lines with FDC technique, achieving a wide stopband. Meanwhile, the circuit dimension is further reduced by symmetrically cutting SIW. To validate the novel approach, the frequency-dependent coupling matrix (CM) is implemented to determine characteristics of the proposed structure in theory, QM- and EM-SIW BPFs loaded with FDC have been designed, fabricated and measured. Experimental results illustrate the characteristics of miniaturization and good performance. All results are in good agreement.
2. Li, P., H. Chu, and R.-S. Chen, "Design of compact bandpass filters using quarter-mode and eighth-mode SIW cavities," IEEE Trans. Compon. Packaging Manuf. Technol., Vol. 7, No. 6, 956-963, Jun. 2017.
doi:10.1109/TCPMT.2017.2677958
3. Li, L., Z. Wu, K. Yang, X. Lai, and Z. Lei, "A novel miniature single-layer eighth-mode SIW filter with improved out-of-band rejection," IEEE Microw. Wireless Compon. Lett., Vol. 28, No. 5, 407-409, May 2018.
doi:10.1109/LMWC.2018.2813883
4. Szydlowski, L., A. Jedrzejewski, and M. Mrozowski, "A trisection filter design with negative slope of frequency-dependent cross coupling implemented in substrate integrated waveguide (SIW)," IEEE Microw. Wireless Compon. Lett., Vol. 23, No. v, 456-458, Sep. 2013.
doi:10.1109/LMWC.2013.2272611
5. Szydlowski, L., N. Leszczynska, and M. Mrozowski, "A linear phase filter in quadruplet topology with frequency-dependent couplings," IEEE Microw. Wireless Compon. Lett., Vol. 24, No. 1, 32-34, Jan. 2014.
doi:10.1109/LMWC.2013.2288178
6. Jedrzejewski, A., L. Szydlowski, and M. Mrozowski, "Miniaturized bandpass substrate integrated waveguide filter with frequency dependent coupling realized using a symmetric GCPW discontinuity," Microw. Opt. Technol. Lett., Vol. 57, No. 8, 1818-1821, Aug. 2015.
doi:10.1002/mop.29203
7. Li, X., C. You, H. Yu, and Z. He, "Substrate integrated folded waveguide controllable mixed electric and magnetic coupling structure and its application to millimetre-wave pseudo-elliptic filters," Int. J. RF Microw. Comput. Aided Eng., Vol. 27, e21074, 2017.
doi:10.1002/mmce.21074
8. Liu, Q., D. Zhou, D. Zhang, and D. Lv, "A novel frequency-dependent coupling with flexibly controllable slope and its applications on substrate-integrated waveguide filters," IEEE Microw. Wireless Compon. Lett., Vol. 28, No. 11, 993-995, Nov. 2018.
doi:10.1109/LMWC.2018.2872325
9. Cameron, R. J., "Advanced coupling matrix synthesis techniques for microwave filters," IEEE Trans. Microw. Theory Tech., Vol. 51, No. 1, 1-10, Jan. 2003.
doi:10.1109/TMTT.2002.806937
10. He, Y., G. Macchiarella, G. Wang, W. Wu, L. Sun, L. Wang, and R. Zhang, "A direct matrix synthesis for in-line filters with transmission zeros generated by frequency-variant couplings," IEEE Trans. Microw. Theory Tech., Vol. 66, No. 4, 1-10, Apr. 2018.
doi:10.1109/TMTT.2018.2791940
11. Li, G., "Coupling matrix optimization synthesis for filters with constant and frequency-variant couplings," Progress In Electromagnetics Research Letters, Vol. 82, 73-80, Mar. 2019.
doi:10.2528/PIERL19011103
12. Leszczynska, N., L. Szydlowski, and M. Mrozowski, "A novel synthesis technique for microwave bandpass filters with frequency-dependent couplings," Progress In Electromagnetics Research, Vol. 135, 35-50, 2013.
doi:10.2528/PIER13011007
13. Su, Z. L., B. W. Xu, S. Y. Zheng, H. W. Liu, and Y. L. Long, "High-isolation and wide-stopband SIW diplexer using mixed electric and magnetic coupling," IEEE Trans. Circuits Syst. II Express Briefs, Vol. 67, No. 1, 32-36, Jan. 2019.
doi:10.1109/TCSII.2019.2903388
14. Cheng, F., X. T. Li, P. Lu, and K. Huang, "SIW filter with broadband stopband by suppressing the coupling of higher-order resonant modes," Electron. Lett., Vol. 55, No. 25, 1345-1347, Dec. 2019.
doi:10.1049/el.2019.2322
15. Hong, J. S., Microstrip Filters for RF/Microwave Applications, A John Wiley & Sons.
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