A novel compact dual-wideband bandpass filter (BPF), with two multi-mode resonators (MMRs), a quad-mode one (QMR) and a triple-mode one (TMR), is proposed in this paper. The first passband is generated by a QMR loaded with a short-ended stub and two open-ended stubs, and the second one is realized by a TMR loaded with a square ring and a short-ended stub. Each passband can be tuned separately by controlling the corresponding resonator. The classical even-/odd-mode analysis is applied to characterize the presented MMRs due to their symmetric configurations. In order to validate the design methodology, a dual-wideband BPF prototype centered at 2.34 and 3.46 GHz with fractional bandwidths of 25.6% and 21.4% for WLAN and WiMAX applications is designed, fabricated and measured. Measurements have good agreement with simulations.
2. Zhang, S. and L. Zhu, "Synthesis design of dual-band bandpass filters with λ/4 stepped-impedance resonators," IEEE Trans. Microw. Theory Tech., Vol. 61, No. 5, 1812-1819, May 2013.
3. Li, J., S. S. Huang, and J. Z. Zhao, "Design of a compact and high selectivity tri-band bandpass filter using asymmetric stepped-impedance resonators (SIRs)," Progress In Electromagnetics Research Letters, Vol. 44, 81-86, 2014.
4. Luo, S., L. Zhu, and S. Sun, "A dual-band ring-resonator bandpass filter based on two pairs of degenerate modes," IEEE Trans. Microw. Theory Tech., Vol. 58, No. 12, 3427-3432, 2010.
5. Chen, F.-C. and J. M. Qiu, "Third-order dual-band bandpass filter with controllable bandwidths using short stub-loaded resonators," Progress In Electromagnetics Research Letters, Vol. 32, 101-108, 2012.
6. Li, J., S. S. Huang, H. Wang, and J. Z. Zhao, "Compact dual-band bandpass filter using embedded center-grounded SIR and open-loop resonators," Progress In Electromagnetics Research Letters, Vol. 49, 9-14, 2014.
7. 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.
8. Chin, K.-S. and J.-H. Yeh, "Dual-wideband bandpass filter using short-circuited stepped-impedance resonators," IEEE Microw. Wireless Compon. Lett., Vol. 19, No. 3, 155-157, 2009.
9. Zhou, J.-G., W.-J. Feng, and W.-Q. Che, "Dual-wideband bandpass filter using T-shaped structure based on transversal signal-interaction concepts," Electron. Lett., Vol. 48, No. 24, 1539-1540, 2012.
10. Xu, J. and W. Wu, "Miniaturised dual-wideband bandpass filter using novel dual-band coupled-line sections," Electron. Lett., Vol. 49, No. 18, 1162-1163, 2013.
11. Li, J., S.-S. Huang, and J.-Z. Zhao, "Compact dual-wideband bandpass filter using a novel penta-mode resonator (PMR)," IEEE Microw. Wireless Compon. Lett., Vol. 24, No. 10, 668-670, 2014.