A compact microstrip-line dual-band bandpass filter with controllable characteristics is presented using a stub-loaded resonator. The resonator is formed by loading one open circuit terminated stub in shunt to a simple uniform impedance line. The passband frequencies of the dual-band filter can be conveniently controlled by tuning the lengths of stub-loaded resonators. The bandwidth of the first passband can be controlled by tuning the parameters of center stub-loaded resonator, and the bandwidth of the second passband is determined by the coupling between the sideward stub-loaded resonators. To illustrate the concept, a second-order dual-band filter is designed, fabricated and measured. Simulated and measured results are found in good agreement with each other.
2. Zhang, X. Y., J. X. Chen, and Q. Xue, "Dual-band bandpass filter using stub-loaded resonators," IEEE Microw. Wireless Compon. Lett., Vol. 17, 583-585, 2007.
3. 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, 150-155, 2008.
4. 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, 779-781, 2008.
5. Chu, Q. X., F. C. Chen, Z. H. Tu, and H. Wang, "A novel crossed resonator and its applications to bandpass filters," IEEE Trans. Microw. Theory Tech., Vol. 57, 1753-1759, 2009.
6. 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, 1551-1556, 2010.
7. 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, 616-618, 2010.
8. Lee, J. R., J. H. Cho, and S. W. Yun, "New compact bandpass filter using microstrip λ/4 resonators with open stub inverter," IEEE Microwave Guided Wave Lett., Vol. 10, 526-527, 2000.
9. 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.
10. 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.
11. 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.
12. 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.
13. 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.
14. 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.
15. 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.
16. Wu, G.-L., W. Mu, X.-W. Dai, and Y.-C. Jiao, "Design of novel dual-band bandpass filter with microstrip meanderloop resonator and CSRR DGS," Progress In Electromagnetics Research, Vol. 78, 17-24, 2008.
17. Chen, F. C., Q. X. Chu, and Z. H. Tu, "Tri-band bandpass filter using stub loaded resonators," Electron. Lett., Vol. 44, 747-749, 2008.
18. 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, 107-124, 2010.
19. Amari, S., U. Rosenberg, and J. Bornemann, "Adaptive synthesis and design of resonator filters with source/load-multi-resonator coupling," IEEE Trans. Microw. Theory Tech., Vol. 50, 1969-1978, 2002.
20. Thomas, J. B., "Cross-coupling in coaxial cavity filters --- A tutorial overview," IEEE Trans. Microw. Theory Tech., Vol. 51, 1368-1376, 2003.