In this paper, a novel compact wideband bandpass filter (BPF) is proposed using quadruple-mode resonator formed by attaching a short-circuited stub at the center plane and two identical impedance-stepped open stubs to high impedance microstrip line. The resonator can generate two even-modes fm1, fm3 and two odd-modes fm2, fm4 in the desired band. The even-mode resonant frequencies can be flexibly controlled by the short-circuited stub, whereas the odd-mode ones are fixed. When the open stubs are attached to the center plane nearby, they can be mainly applied to adjust fm3, fm4 into desired passband as the high odd-mode and even-mode resonant frequencies are vulnerable to their electronic lengths. Two transmission zeros near the lower and upper cut-off frequencies are separately created by the short-circuited stub and interdigital feeding lines, leading to a high rejection skirt. A wideband BPF with the fractional bandwidth 64% is simulated, fabricated and measured. The measured results agree well with the EM simulations.
2. 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.
3. Tan, B. T., J. J. Yu, S. T. Chew, M.-S. Leong, and B.-L. Ooi, "A miniaturized dual-mode ring bandpass filter with a new perturbation," IEEE Microwave and Wireless Components Lett., Vol. 53, No. 1, 343-345, Jan. 2005.
4. Huang, X. D. and C. H. Cheng, "A novel coplanar-waveguide bandpass filter using a dual-mode square-ring resonator," IEEE Microwave and Wireless Components Lett., Vol. 16, No. 1, 13-15, Jan. 2006.
5. Kang, W., W. Hong, and J. Y. Zhou, "Performance improvement and size reduction of microstrip dual-mode bandpass filter," Electronics Letter, Vol. 44, No. 6, 421-422, Mar. 2008.
6. Hong, J.-S., H. Shaman, and Y.-H. Chun, "Dual-mode microstrip open-loop resonators and filters," IEEE Transactions on Microwave Theory and Techniques, Vol. 55, No. 8, 1764-1770, Aug. 2007.
7. Zhou, M., X. Tang, and F. Xiao, "Miniature microstrip bandpass filter using resonator-embedded dual-mode resonator based on source-load coupling," IEEE Microwave and Wireless Components Lett., Vol. 20, No. 3, 139-141, Mar. 2010.
8. Shen, W., X.-W. Sun, and W.-Y. Yin, "A novel microstrip filter using three-mode stepped impedance resonator (TSIR)," IEEE Microw. Wireless Compon. Lett., Vol. 19, No. 12, 774-776, Dec. 2009.
9. Lei, R. and L. Zhu, "Compact UWB bandpass filter using stub-loaded multiple-mode resonator," IEEE Microw. Wireless Compon. Lett., Vol. 17, No. 1, 40-42, Nov. 2007.
10. Wong, S. W. and L. Zhu, "EBG-embedded multiple-mode resonator for UWB bandpass filter with improved upper-stopband performance," IEEE Microw. Wireless Compon. Lett., Vol. 17, No. 6, 421-423, Jun. 2007.
11. Han, L., K. Wu, and X. P. Chen, "Compact ultra-wideband bandpass filter using stub-loaded resonator," Electronics Letter, Vol. 45, No. 10, 504-506, May 2009.
12. Wong, S. W. and L. Zhu, "Quadruple-mode UWB bandpass filter with improved out-of-band rejection," IEEE Microw. Wireless Compon. Lett., Vol. 19, No. 3, 152-154, Mar. 2009.
13. Ma, K., K. C. B. Liang, R. M. Jayasuriya, and K. S. Yeo, "A wideband and high rejection multimode bandpass filter using stub perturbation," IEEE Microw. Wireless Compon. Lett., Vol. 19, No. 1, 24-26, Jan. 2009.