A novel compact bandpass filter (BPF) with wide upper-stopband has been proposed in this paper. The structure is based on spiral-shaped resonators. Cross coupling is used to generate two transmission zeros at the lower and upper stopbands. Therefore, the out-of-band performance is improved. In addition, two spur-lines are adopted in the feed lines to reject the spurious response. The central frequency f0 of this filter is at 2.45 GHz with a minimum insertion loss of less than 1 dB and a 3 dB bandwidth of 12.5%. Four transmission zeros are located at 2 GHz, 3 GHz, 5.5 GHz, and 8 GHz. The attenuation is greater than 20dB in a wide upper stopband up to 9.8 GHz.
"Compact Bandpass Filter with Wide Upper-Stopband Based on Spiral-Shaped Resonators and Spur-Lines," Progress In Electromagnetics Research Letters,
Vol. 29, 87-95, 2012. doi:10.2528/PIERL11120203
1. Song, K. and Q. Xue, "Inductance-loaded Y-shaped resonators and their applications to filters," IEEE Trans. Microw. Theory Tech., Vol. 58, No. 4, 978-984, 2010. doi:10.1109/TMTT.2010.2042509
2. Pistono, E., M. Robert, and L. Duvillaret, "Compact fixed and tune-all bandpass filters based on coupled slow-wave resonators," IEEE Trans. Microw. Theory Tech., Vol. 54, No. 6, 2790-2799, 2006. doi:10.1109/TMTT.2006.874894
3. Song, K. and Q. Xue, "Novel broadband bandpass filters using Y-shaped dual-mode microstrip resonators," IEEE Microw. Wireless Compon. Lett., Vol. 19, No. 9, 548-550, 2009. doi:10.1109/LMWC.2009.2027058
4. Hong, J.-S. and M. J. Lancaster, "Theory and experiment of novel microwave slow-wave open-loop resonator filters," IEEE Trans. Microw. Theory Tech., Vol. 45, No. 12, 2358-2365, 1997. doi:10.1109/22.643844
5. Song, K. and Q. Xue, "Asymmetric dual-line coupling structure for multiple-notch implementation in UWB bandpass filters," Electron. Lett., Vol. 46, No. 20, 1388-1390, 2010. doi:10.1049/el.2010.1505
6. Hsu, C. L. and J. T. Kuo, "A two-stage SIR bandpass filter with an ultra-wide upper rejection band," IEEE Microw. Wireless Compon. Lett., Vol. 7, No. 1, 34-36, 2007. doi:10.1109/LMWC.2006.887248
7. Chen, Y. M., S. F. Chang, C. C. Chang, and T. J. Hung, "Design of stepped-impedance combline bandpass filter with symmetric insertion-loss response and wide stopband range," IEEE Trans. Microw. Theory Tech., Vol. 55, No. 10, 2191-2198, 2007. doi:10.1109/TMTT.2007.906482
8. Deng, P.-H. and P.-T. Chiu, "New bandpass filter using half-wavelength and branch-line resonators," Progress In Electromagnetics Research C, Vol. 16, 241-249, 2010. doi:10.2528/PIERC10092306
9. Dai, G. and M. Xia, "Novel miniaturized bandpass filter using spiral-shaped resonators and window feed structures," Progress In Electromagnetics Research, Vol. 100, 235-243, 2010. doi:10.2528/PIER09120401
10. Song, K. and Q. Xue, "Compact ultra-wideband (UWB) bandpass filters with multiple notched bands," IEEE Microw. Wireless Compon. Lett., Vol. 20, No. 8, 447-449, 2010. doi:10.1109/LMWC.2010.2050303
11. Wang, R. , L.-S. Wu, and X.-L. Zhou, "Compact folded substrate integrated waveguide cavities and bandpass filter," Progress In Electromagnetics Research, Vol. 84, 135-147, 2008. doi:10.2528/PIER08071501
12. Li, , L., , H. Liu, and B. Teng, "Novel microstrip lowpass filter using stepped impedance resonator and spurline resonator," Microwave and Optical Technology Letters, Vol. 51, No. 1, 196-197, 2009. doi:10.1002/mop.23993
13. Chu, Q.-X. and H. Wang, "A compact open loop filter with mixed electric and magnetic coupling," IEEE Trans. Microw. Theory Tech., Vol. 56, No. 2, 431-439, 2008. doi:10.1109/TMTT.2007.914642
14. Wu, H.-W. , S.-K. Liu, M.-H. Weng, and C.-H. Hung, "Compact microstrip bandpass filter with multispurious suppression," Progress In Electromagnetics Research, Vol. 107, 21-30, 2010. doi:10.2528/PIER10061601
15. Song , K. and Y. Fan, "Compact ultra-wideband bandpass filter using dual-line coupling structure," IEEE Microw. Wireless Compon. Lett., Vol. 19, No. 1, 30-32, 2009. doi:10.1109/LMWC.2008.2008565
16. Yang, R.-Y. , H. Kuan, C.-Y. Hung, and C.-S. Ye, "Design of dual-band bandpass filters using a dual feeding structure and embedded uniform impedance resonators," Progress In Electromagnetics Research, Vol. 105, 93-102, 2010. doi:10.2528/PIER10042504
17. W , L.-S. , J.-F. Mao, W. Shen, and W.-Y. Yin, "An extended doublet bandpass filter implemented with microstrip resonator and substrate integrated waveguide cavity," Proceedings of Asia-pacific Microwave Conference 2010 WE4B-2, 2010.
18. Peng, L. , C.-L. Ruan, and C.-Y. Ding, "Miniature filter based on metamaterials with transmission zeros and wider upper-stopband performance," 3rd IEEE International Symposium Microwave, Antenna, Propagation and EMC Technologies for Wireless Communications, 2009.
19. Hong, , J. S. and M. J. Lancaster, "Microstrip Filters for RF/Microwave Applications," Chapter 8, 235-271, Wiley, New York, 2001.