In this letter, a compact microstrip bandpass filter (BPF) with four transmission zeros (TZs) is designed by using a short-stub centered loaded folded dual-mode resonator and an I/O mutual coupled open-stub loaded feedline structure. The coupling structure can realize source-load (S-L) coupling with quadratic function coupling coefficient, which can generate three TZs in the upper-stopband to improve the selectivity. Owing to the intrinsic characteristics of the dual-mode resonator, one extra TZ can be created near the lower passband edge. Finally, a compact BPF with fractional bandwidth (FBW) of 3.5% located at 2.4 GHz for WLAN application has been designed and fabricated. Good agreement between simulation and measurement verifies the validity of the design.
2. Deng, H. W., Y. J. Zhao, X. S. Zhang, W. Chen, and J. K. Wang, "Compact and high selectivity dual-band dual-mode microstrip BPF with single stepped-impedance resonator," Electron. Lett., Vol. 47, No. 5, 326-327, 2011.
doi:10.1049/el.2011.0054
3. Zhou, M. Q., X. H. Tang, and F. Xiao, "Miniature microstrip bandpass filter using resonator-embedded dual-mode resonator based on source-load coupling," IEEE Microw. Wireless Compon. Lett., Vol. 20, No. 3, 139-141, 2010.
doi:10.1109/LMWC.2010.2040210
4. Wei, C. L., B.-F. Jia, Z.-J. Zhu, and M.-C. Tang, "Design of different selectivity dual-Mode filters with E-shaped resonator," Progress In Electromagnetics Research, Vol. 116, 517-532, 2011.
doi:10.2528/PIER11040808
5. Gao, S., S.-Q. Xiao, and J.-L. Li, "Miniaturized microstrip dual-mode filter with three transmission zeros," Progress In Electromagnetics Research Letters, Vol. 31, 199-207, 2012.
doi:10.2528/PIERL12033002
6. Feng, W., X. Gao, and W. Che, "Bandpass filters with improved selectivity based on dual-mode ring resonators," Progress In Electromagnetics Research Letters, Vol. 56, 1-7, 2015.
doi:10.2528/PIERL15072609
7. Xu, Z., Y. Shi, C. Xu, and P. Wang, "A novel dual mode substrate integrated waveguide filter with mixed source-load coupling (MSLC)," Progress In Electromagnetics Research, Vol. 136, 595-606, 2013.
doi:10.2528/PIER12121505
8. Zhang, X.-S., Y.-J. Zhao, H.-W. Deng, L. Zhang, and W. Chen, "High selectivity dual-mode bandpass filter with source-loaded coupling," Progress In Electromagnetics Research Letters, Vol. 18, 187-194, 2010.
doi:10.2528/PIERL10092001
9. Tamiazzo, S. and G. Macchiarella, "Synthesis of cross-coupled prototype filters including resonant and non-resonant nodes," IEEE Trans. Microw. Theory Tech., Vol. 63, No. 10, 3408-3415, 2015.
doi:10.1109/TMTT.2015.2457421
10. Leszczynska, N., L. Szydlowski, and M. Mrozowski, "A novel synthesis technique for microwave bandpass filters with frequency-dependent couplings," Progress In Electromagnetics Research, Vol. 137, 35-50, 2013.
doi:10.2528/PIER13011007
11. Hsu, C.-L. and J.-T. Kuo, "Microstrip realization of trisection synthesis with frequency-dependent admittance inverter," Progress In Electromagnetics Research, Vol. 113, 195-210, 2011.
doi:10.2528/PIER11011301
12. Szydlowski, L., A. Lamecki, and M. Mrozowski, "Coupled-resonator waveguide filter in quadruplet topology with frequency-dependent coupling --- a design based on coupling matrix," IEEE Microw. Wireless Compon. Lett., Vol. 22, 553-555, 2012.
doi:10.1109/LMWC.2012.2225604
13. Tamiazzo, S. and G. Macchiarella, "Synthesis of cross-coupled filters with frequency-dependent couplings," IEEE Trans. Microw. Theory Tech., Vol. 65, 775-782, 2017.
doi:10.1109/TMTT.2016.2633258
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