Two new microstrip tri-mode modified ring resonators (Resonator A and Resonator B) are presented and discussed through mode analysis method. The characteristic difference between these two resonators is that the center frequency of the tri-mode Resonator B is still the same as that of traditional dual-mode ring resonator, while the center frequency of Resonator A will be shifted up compared with that of traditional ring resonator. Based on these two novel resonators, two bandpass filter examples are designed, fabricated and measured. The simulations and measurements are in good agreement which validate the design ideas.
2. Mao, R. J. and X. H. Tang, "Novel dual-mode bandpass filters using hexagonal loop resonators," IEEE Trans. Microw. Theory Tech., Vol. 54, No. 9, 3526-3533, 2006.
doi:10.1109/TMTT.2006.881025
3. Xu, K. D., Y. H. Zhang, C. L. Zhuge, and Y. Fan, "Miniaturized dual-band bandpass filter using short stub-loaded dual-mode resonators," Journal of Electromagnetic Waves and Applications, Vol. 25, No. 16, 2264-2273, 2011.
doi:10.1163/156939311798147060
4. Tu, W.-H., "Compact double-mode cross-coupled microstrip bandpass filter with tunable transmission zeros," IET Microw. Antennas Propag., Vol. 2, No. 4, 373-377, 2008.
doi:10.1049/iet-map:20070203
5. Xu, K. D., Y. H. Zhang, Y. Fan, W. T. Joines, and Q. H. Liu, "Novel circular dual-mode filter with both capacitive and inductive source-load coupling for multiple transmission zeros," Journal of Electromagnetic Waves and Applications, Vol. 26, No. 13, 1675-1684, 2012.
doi:10.1080/09205071.2012.708966
6. Sun, S., "A dual-band bandpass filter using a single dual-mode ring resonator," IEEE Microw. Wirel. Compon. Lett., Vol. 21, No. 6, 298-300, 2011.
doi:10.1109/LMWC.2011.2132119
7. Xu, K. D., Y. H. Zhang, W. T. Joines, Q. H. Liu, and Y. Fan, "Tri-band bandpass filter using short stub-loaded dual-mode resonators," Microw. J., Vol. 56, No. 9, 122-130, 2013.
8. Xu, K. D., Y. H. Zhang, Y. Fan, W. T. Joines, and Q. H. Liu, "Microstrip dual-mode bandpass filter design using pie-section truncated semi-circle and quarter-circle resonators," IET Microw. Antennas Propag., Vol. 9, No. 3, 224-229, 2015.
doi:10.1049/iet-map.2014.0170
9. Wolff, I., "Microstrip bandpass filter using degenerate modes of a microstrip ring resonator," Electron. Lett., Vol. 8, 302-303, 1972.
doi:10.1049/el:19720223
10. Tu, W. H., "Microstrip bandpass filters using cross-shaped triple-mode resonator," IET Microw. Antennas Propag., Vol. 4, No. 9, 1421-1426, 2010.
doi:10.1049/iet-map.2009.0364
11. Chen, F. C., Q. X. Chu, Z. H. Li, and X. H. Wu, "Compact dual-band bandpass filter with controllable bandwidths using stub-loaded multiple-mode resonator," IET Microw. Antennas Propag., Vol. 6, No. 10, 1172-1178, 2012.
doi:10.1049/iet-map.2011.0523
12. Lee, K. C., H. T. Su, and M. K. Haldar, "Compact quadruple-mode resonator for wideband bandpass filter design," IET Microw. Antennas Propag., Vol. 8, No. 2, 67-72, 2014.
doi:10.1049/iet-map.2013.0021
13. Serrano, A. L. C. and F. S. Correra, "A triple-mode bandpass filter using a modified circular patch resonator," Microw. Opt. Technol. Lett., Vol. 51, No. 1, 178-182, 2009.
doi:10.1002/mop.23950
14. Mo, S.-G., Z.-Y. Yu, and L. Zhang, "Design of triple-mode bandpass filter using improved hexagonal loop resonator," Progress In Electromagnetics Research, Vol. 96, 117-125, 2009.
doi:10.2528/PIER09080304
15. Wei, C. L., B. F. Jia, and Z. J. Zhu, "Design of triple-mode microstrip filter with source-load coupling," Microw. Opt. Technol. Lett., Vol. 53, No. 10, 2403-2406, 2011.
doi:10.1002/mop.26278
16. Zhang, L., Z. Y. Yu, and S. G. Mo, "Design of compact triple-mode bandpass filter using double center stubs-loaded resonator," Microw. Opt. Technol. Lett., Vol. 52, No. 9, 2109-2111, 2010.
doi:10.1002/mop.25364
17. Chen, C. F., "Design of a compact microstrip quint-band filter based on the tri-mode stub-loaded stepped-impedance resonators," IEEE Microw. Wirel. Compon. Lett., Vol. 22, No. 7, 357-359, 2012.
doi:10.1109/LMWC.2012.2202894
18. Chang, K. and L. H. Hsieh, Microstrip Ring Circuits and Related Structures,, Wiley, New York, USA, 2004.
doi:10.1002/0471721298
19. Xu, K. D., Y. H. Zhang, Y. Fan, J. L. W. Li, W. T. Joines, and Q. H. Liu, "Planar dual- and tri-band bandpass filters using single improved ring resonator and simple feed scheme," Microw. Opt. Technol. Lett., Vol. 56, No. 3, 574-577, 2014.
doi:10.1002/mop.28159
20., Ansoft High Frequency Structural Simulator (HFSS), 12th Ed., Ansoft Corp., Framingham, MA, USA, 2006.