In this paper, a novel high selectivity dual-band microwave bandpass filter (BPF) using dual-mode and triple-mode resonator is proposed. First, a dual-band filter comprising two dual-mode single band filters using common input/out lines is designed. Each single BPF is realized using a stepped-impedance resonator (SIR) with a centrally-loaded shunt open stub. The first and second passband can be independently controlled by the two dual-mode resonators, respectively. The proposed filter also offers three transmission zeros (TZs) to improve the selectivity. To further improve the selectivity over high side band of the first passband, a novel triple-mode resonator is designed to replace the dual-mode resonator. The basic structure of triple-mode resonator is microstrip-to-coplanar waveguide (CPW) structure. The microstrip structure provides one odd mode and one even mode resonator frequency and the CPW structure can provide another even mode resonant frequency without increasing circuit size. Both simulated and measured results show that the filters exhibit a good performance, including a small insertion loss, selectivity.
2. Velazquez-Ahumada, M. D. C., "Application of stub loaded folded stepped impedance resonators to dual band ¯lter design," Progress In Electromagnetics Research, Vol. 102, 107-124, 2010.
3. Kuo, J. T. and S. W. Lai, "New dual-band bandpass filter with wide upper rejection band," Progress In Electromagnetics Researc, Vol. 123, 371-384, 2012.
4. Wu, H. W., Y. F. Chen, and Y. F. Chen, "Multi-layered dual-band bandpass filter using stub-loaded stepped-impedance and uniform-impedance resonators," IEEE Microw. Wireless Compon. Lett., Vol. 22, No. 3, 114-116, Mar. 2012.
5. Wang, J., L. Ge, K.Wang, W.Wu, and , "Compact microstrip dual-mode dual-band bandpass filter with wide stopband," Electronics Letters, Vol. 47, No. 4, Feb. 2011.
6. Chen, C. F., T. Y. Huang, and R. B. Wu, "Design of dual-and triple-passband filters using alternately cascaded multiband resonators," IEEE Trans. on Microw. Theory and Tech., Vol. 54, No. 9, 3550-3558, Sep. 2006.
7. Deng, P. H. and J. H. Jheng, "A switched reconfigurable high-isolation dual-band bandpass filter," IEEE Microw. Wireless Compon. Lett., Vol. 21, No. 2, 71-73, Feb. 2012.
8. Xu, J., C. Miao, and W. Wu, "A compact and high isolation dual-mode dual-band bandpass filter with tunable transmission zeros," Journal of Electromagnetic Waves and Applications, Vol. 26, No. 17-18, 2390-2397, Dec. 2012.
9. Wei, F. , L. Chen, and X. W. Shi, "Compact dual-mode dual-band bandpass filter with wide stopband," Journal of Electromagnetic Waves and Applications, Vol. 26, No. 11-12, 1441-1447, Aug. 2012.
10. Deng, H. W., Y. J. Zhao, X. S. Zhang, W. Chen, and J. K. Wang, "Compact and high selectivtity dual-band dual-mode microstrip BPF with single step- impedance resonator," Electronics Letters, Vol. 47, No. 5, Mar. 2011.
11. Youngje, S., "Dual-mode dual-band filter with band notch structures," IEEE Microw. Wireless Compon. Lett., Vol. 20, No. 2, 73-75, Jan. 2010.
12. Sun, S., "A dual-band bandpass filter using a single dual-mode ring resonator," IEEE Microw. Wireless Compon. Lett., Vol. 21, No. 6, 298-300, Jun. 2011.
13. Lee, J. and Y. Lim, "Compact dual-band bandpass filter with good frequency selectivity," Electronics Letters, Vol. 47, No. 25, Dec. 2011.
14. Wu, Y. L., C. Liao, and X. Z. Xiong, "A dual-wideband bandpass filter based on E-shaped microstrip SIR with improved upper stopband performance," Progress In Electromagnetics Research, Vol. 108, 141-153, 2010.
15. Chang, W. S. and C. Y. Chang, "Analytical design of microstrip short-circuit terminated stepped-impedance resonator dual-band filters," IEEE Trans. on Microw. Theory and Tech., Vol. 59, No. 7, 1730-1739, Jul. 2011.
16. Mashhadi, M. and N. Komjani, "Design of novel dual-band bandpass filter with multi-spurious suppression for WLAN application," Journal of Electromagnetic Waves and Applications, Vol. 26, No. 7, 851-862, 2012.
17. Seungku, L. and L. Yongshik, "A planar dual-band filter based on reduced-length parallel coupled lines," IEEE Microw. Wireless Compon. Lett., Vol. 20, No. 1, 16-18, Jan. 2010.