A novel wideband bandpass filter on a triple-mode slotline ring resonator is proposed in this letter. By attaching two stubs with different lengths and/or widths to the symmetric plane of a slotline ring resonator, the frequencies of first three resonant modes can be rearranged towards quasi-equal separation. By feeding this slotline resonator using the microstrip feed lines at positions with an angle of 90° to the symmetrical plane, these three resonant modes can be simultaneously raised up, aiming to form up a wide passband. Meanwhile, a wide upper-stopband can be realized by setting the lengths of two stubs unequally. After the principle of an initial wideband filter is described, a prototype of compact filter with internally-loaded stubs is designed with fractional bandwidth of 66% at center frequency of 3.0 GHz. Measured results well validate the predicted ones.
"A Novel Wideband Bandpass Filter Using Triple-Mode Slotline Ring Resonator," Progress In Electromagnetics Research Letters,
Vol. 40, 163-170, 2013. doi:10.2528/PIERL13040104
1. Chang, K., Microwave Ring Circuits and Antennas, Wiley, New York, 1996.
2. Wolff, I., "Microstripbandpass filter using degenerate modes of a microstrip ring resonator," Electron. Lett., Vol. 8, No. 12, 302-303, 1972. doi:10.1049/el:19720223
3. Matsuo, M., H. Yabukiand, and M. Makimoto, "Dual-mode stepped-impedance ring resonator for bandpass filter applications," IEEE Trans. on Microw. Theory and Tech., Vol. 49, No. 7, 1235-1240, 2001. doi:10.1109/22.932241
4. Gorur, A., "Description of coupling between degenerate modes of a dual-mode microstrip loop resonator using a novel perturbation arrangement and its dual-mode bandpass filter applications," IEEE Trans. on Microw. Theory and Tech., Vol. 52, No. 2, 671-677, 2004. doi:10.1109/TMTT.2003.822033
5. Chen, Z.-X., X.-W. Dai, and C.-H. Liang, "Novel dual-mode dual-band bandpass filter using double square-loop structure," Progress In Electromagnetics Research, Vol. 77, 409-416, 2007. doi:10.2528/PIER07082803
6. 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, 1995. doi:10.1109/75.473539
7. Luo, S., L. Zhu, and S. Sun, "A dual-band ring-resonator bandpass filter based on two pairs of degenerate modes," IEEE Trans. on Microw. Theory and Tech., Vol. 58, No. 12, 3427-3432, 2010.
8. Hsieh, L. H. and K. Chang, "Compact, low insertion-loss, sharp-rejection, and wide-band microstrip bandpass filters," IEEE Trans. on Microw. Theory and Tech., Vol. 51, No. 4, 1241-1246, 2003. doi:10.1109/TMTT.2003.809643
9. Ishida, H. and K. Araki, "Design and analysis of UWB bandpass filter with ring filter," IEEE MTT-S Int. Dig., Vol. 3, 1307-1310, 2004.
10. Luo, S. and L. Zhu, "A dual-mode dual-band bandpass filter using a single slot ring resonator," Progress In Electromagnetics Research Letter, Vol. 23, 173-180, 2011.
11. Sun, S. and L. Zhu, "Wideband microstrip ring resonator bandpass filters undermultiple resonances," IEEE Trans. on Microw. Theory and Tech., Vol. 55, No. 10, 2176-2182, 2007. doi:10.1109/TMTT.2007.906510