A new design consideration is explored for a hair-pin resonator. A grounding via at the mid-point of the resonator acts as a perturbation to split the resonant frequencies. The via also suppresses even harmonics of the fundamental. The principle operation of the hair-pin resonator with a via is analyzed and verified by measurement. It is shown that such a hair-pin resonator can be made more compact using stepped impedance line. A compact 4-pole bandpass filter using the modified compact hair-pin resonator with a via is demonstrated. Simulation and measured results showed good agreement.
2. Sheta Miniature microstrip stepped impedance resonator bandpass filters and diplexers for mobile communications, A. F., J. P. Coupez, G. Tanne, S. Toutain, and J. P. Blot, IEEE MTT-S Int. Microwave Symp. Dig., 607-610, 1996.
3. Schwab, W. and W. Menzel, "Compact bandpass filters with improved stop-band characteristics using planar multilayer structures," IEEE MTT-S Int. Microwave Symp. Dig., 1207-1210, 1992.
4. Hong, J.-S. and M. J. Lancaster, "Compact microwave elliptic function filter using novel microstrip meander open-loop resonators," Electronics Lett., Vol. 32, No. 6, 563-564, Mar. 1996.
5. Curtis, J. A. and S. J. Fiedziuszko, "Miniature dual mode microstrip filters," IEEE MTT-S Int. Microwave Symp. Dig., 443-446, 1991.
6. Hejazi, Z. M., P. S. Excell, and Z. Jiang, "Compact dual mode filters for HTS satellite communication systems," IEEE Microw. Guided Wave Lett., Vol. 8, No. 8, 275-277, Aug. 1996.
7. Hong , J.-S. and M. J. Lancaster, "Microstrip bandpass filter using degenerate modes of a novel meander loop resonator," IEEE Microw. Guided Wave Lett., Vol. 5, No. 11, 371-372, Nov. 1995.
8. Hong, J.-S., H. Shaman, and Y.-H. Chun, "Dual-mode microstrip open-loop resonators and filters," IEEE Trans. on Microw. Theory and Tech., Vol. 55, No. 8, 1764-1770, Aug. 2007.
9. Paul, D. K., P. Gardner, and K. P. Tan, "Suppression of even modes in microstrip ring resonators," Electronics Lett., Vol. 30, No. 21, 1772-1774, Oct. 1994.
10. Marti, J. and A. Griol, "Harmonic suppressed microstrip multistage coupled ring bandpass filters," Electronics Lett., Vol. 34, No. 22, 2140-2142, Oct. 1998.
11. Carroll, J. M. and K. Chang, "Microstrip mode suppression ring resonator," Electronics Lett., Vol. 30, No. 22, 1861-1862, Oct. 1994.
12. Karacaoglu, U., D. Sanchez-Hernandez, I. Robertson, and M. Guglielmi, "Harmonic suppression in microstrip dual mode ring-resonator filters," IEEE MTT-S Int. Microwave Symp. Dig., 1635-1638, 1996.
13. Allen, C. A., K. M. K. H. Leong, T. Itoh, and , "Dual-mode composite-right/left-handed transmission line ring resonator," Electronics Lett., Vol. 42, No. 2, 96-97, Jan. 2006.
14. Su, , H. T. and M. K. Haldar, "Redesign of a dual-mode ring resonator using composite-right/left-handed line," 2007 Asia-Pacific Microwave Conference Proceedings, 1-4, Bangkok,Dec. 2007.
15. Su, H. T., K. K. Fong, M. K. Haldar, and M. L. D. Wong, "New 4-pole dual-mode resonator filter using composite-right/left-handed," 2008 Asia-Pacific Microwave Conference.
16. Chang, K. and L.-H. Hsieh, Microwave Ring Circuits and Related Structures, Wiley, New York, 2004.
17. Hong, J.-S. and M. J. Lancaster, Microstrip Filters for RF/Microwave Applications, Wiley, New York, 2001.
18. SONNET 12.52, Sonnet Software Inc., , Pittsburgh, PA, 2009.
19. Hoefer, W. J. R. and A. Chattopadhyay, "Evaluation of the equivalent circuit parameters of microstrip discontinuities through perturbation of a resonant ring," IEEE Trans. on Microw. Theory and Tech., Vol. 23, No. 12, 1067-1071, Dec. 1975.