A compact microstrip-line dual-band bandpass filter using a short stub-loaded resonator is presented. The resonator is formed by loading one short stub in shunt to a simple uniform impedance line. A key merit of the filter configuration is that the center frequency and bandwidth of the first passband can be conveniently controlled by properly adjusting the lengths of the short stubs and the coupling between the short stubs, whereas those of the second passband are fixed. To illustrate the concept, a third-order dual-band filter is designed, fabricated and measured. Simulated and measured results are found to be in good agreement with each other.
2. Alkanhal, M. A. S., "Dual-band bandpass filters using inverted stepped-impedance resonators," Journal of Electromagnetic Waves and Applications, Vol. 23, No. 8-9, 1211-1220, 2009.
3. Lee, C. H., I. C. Wang, and C. I. G. Hsu, "Dual-band balanced BPF using λ/4 stepped-impedance resonators and folded feed lines," Journal of Electromagnetic Waves and Applications, Vol. 23, No. 17-18, 2441-2449, 2009.
4. Wang, J. P., B.-Z. Wang, Y. X. Wang, and Y.-X. Guo, "Dual-band microstrip stepped-impedance bandpass filter with defected ground structure," Journal of Electromagnetic Waves and Applications, Vol. 22, No. 4, 463-470, 2008.
5. Weng, M.-H., C.-H. Kao, and Y.-C. Chang, "A compact dual-band bandpass filter using cross-coupled asymmetric SIRs for WLANs," Journal of Electromagnetic Waves and Applications, Vol. 24, No. 2-3, 161-168, 2010.
6. Weng, M.-H., S.-K. Liu, H.-W. Wu, and C.-H. Hung, "A dual-band bandpass filter having wide and narrow bands simultaneously using multilayered stepped impedance resonators ," Progress In Electromagnetics Research Letters, Vol. 13, 139-147, 2010.
7. Fan, J.-W. , C.-H. Liang, and X.-W. Dal, "Design of cross-coupled dual-band filter with equal length split-ring resonators," Progress In Electromagnetics Research, Vol. 75, 285-293, 2007.
8. Xue, W., C.-H. Liang, X.-W. Dai, and J.-W. Fan, "Design of miniature planar dual-band filter with 0 feed structures," Progress In Electromagnetics Research, Vol. 77, 493-499, 2007.
9. Wu, G.-L. , W. Mu, X.-W. Dai, and Y.-C. Jiao, "Design of novel dual-band bandpass filter with microstrip meander loop resonator and CSRR DGS," Progress In Electromagnetics Research, Vol. 78, 17-24, 2008.
10. Velazquez-Ahumada, M. D. C. , J. Martel-Villagr, F. Medina, and F. Mesa, "Application of stub loaded folded stepped impedance resonators to dual band filter design," Progress In Electromagnetic Research, Vol. 102, 107-107124, 2010.
11. Zhang, X. Y. , J. X. Chen, and Q. Xue, "Dual-band bandpass filter using stub-loaded resonators," IEEE Microw. Wireless Compon. Lett., Vol. 17, No. 8, 583-585, 2007.
12. Zhang, X. Y. and Q. Xue, "Novel centrally loaded resonators and their applications to bandpass filter," IEEE Trans. Microw. Theory Tech., Vol. 56, No. 4, 913-921, 2008.
13. Zhou, M.-Q. , X.-H. Tang, and F. Xiao, "Compact dual band bandpass filter using novel E-type resonators with controllable bandwidths," IEEE Microw. Wireless Compon. Lett., Vol. 18, No. 12, 779-781, 2008.
14. Chen, F. C. , Q. X. Chu, and Z. H. Tu, "Tri-band bandpass filter using stub loaded resonators," Electron. Lett., Vol. 44, No. 12, 747-749, 2008.
15. Chu, Q. X., F. C. Chen, Z. H. Tu, H. Wang, "A novel crossed resonator and its applications to bandpass filters," IEEE Trans. Microw. Theory Tech., Vol. 57, No. 7, 1753-1759, 2009.
16. Chen, F. C., Q. X. Chu, and Z. H. Tu, "Design of compact dual-band bandpass filter using short stub loaded resonator," Microw. Opt. Technol. Lett., Vol. 51, No. 4, 959-963, 2009.
17. Mondal, P. and M. K. Mandal, "Design of dual-band bandpass filters using stub-loaded open-loop resonators," IEEE Trans. Microw. Theory Tech., Vol. 56, No. 1, 150-155, 2008.
18. Chen, F. C. and J. M. Qiu, "Dual-band bandpass filter with controllable characteristics using stub-loaded resonators," Progress In Electromagnetics Research Letters, Vol. 28, 45-51, 2012.
19. Zhang, X. Y., C. H. Chan, Q. Xue, and B. J. Hu, "Dual-band bandpass filter with controllable bandwidths using two coupling paths," IEEE Microw. Wireless Compon. Lett., Vol. 20, No. 11, 616-618, 2010.
20. Chen, F. C. and Q. X. Chu, "Novel multistub loaded resonator and its application to high-order dual-band filters," IEEE Trans. Microwave Theory Tech., Vol. 58, No. 6, 1551-1556, 2010.