A novel bandstop filter with wide-stopband performance is proposed and discussed in this paper. This circuit configuration includes two-section coupled lines and three open-circuit transmission-line stubs. Due to the symmetry of this proposed structure, closed-form equations for scattering parameters are investigated. Transmission zeros and poles location for different circuit parameters are discussed, and the corresponding design curves are given. In order to verify this new filter circuit structure and its corresponding design theory, several typical numerical examples are designed, calculated and illustrated. Furthermore, a practical wideband bandstop filter with -20 dB fractional bandwidth of 94% centered at 3 GHz with sharp rejection characteristics is fabricated to validate the theoretical prediction. The measured frequency response of the filter agrees excellently with the predicted result.
2. Chen, H., Y.-H. Wu, Y.-M. Yang, and Y.-X. Zhang, "A novel and compact bandstop filter with folded microstrip/CPW hybrid structure," Journal of Electromagnetic Waves and Applications, Vol. 24, No. 1, 103-112, 2010.
doi:10.1163/156939310790322163
3. Matthaei, G. L., L. Oung, and E. M. T. Jones, Microwave Filters, Impedance Matching Networks and Coupling Structures, McGraw Hill, New York, 1964.
4. Pozar, D. M., Microwave Engineering, 2nd Ed., Wily, New York, 1998.
5. Wu, Y., Y. Liu, S. Li, and C. Yu, "A simple microstrip bandpass filter with analytical design theory and sharp skirt selectivity," Journal of Electromagnetic Waves and Applications, Vol. 25, No. 8-9, 1253-1263, 2011.
doi:10.1163/156939311795762060
6. Yu, W.-H., J.-C. Mou, X. Li, and X. Lv, "A compact filter with sharp-transition and wideband-rejection using the novel defected ground structure," Journal of Electromagnetic Waves and Applications, Vol. 23, No. 2-3, 329-340, 2009.
doi:10.1163/156939309787604454
7. Wu, Y., Y. Liu, S. Li, and C. Yu, "A new wide-stopband low-pass filter with generalized coupled-line circuit and analytical theory," Progress In Electromagnetics Research, Vol. 116, 553-567, 2011.
8. Gomez-Garcia, R. and J. I. Alonso, "Design of sharp-rejection and low-loss wide-band planar filters using signal-interference techniques," IEEE Microw. Wireless Compon. Lett., Vol. 15, No. 8, 530-532, Aug. 2005.
doi:10.1109/LMWC.2005.852797
9. Sanchez-Soriano, M. A., E. Bronchalo, and G. Torregrosa-Penalva, "Compact UWB bandpass filter based on signal interference techniques," IEEE Microw. Wireless Compon. Lett., Vol. 19, No. 11, 692-694, Nov. 2009.
doi:10.1109/LMWC.2009.2032001
10. Hong, J.-S. and M. J. Lancaster, "Design of highly selective microstrip bandpass filters with a single pair of attenuation poles at finite frequencies," IEEE Trans. on Microw. Theory and Tech., Vol. 48, No. 7, 1098-1107, Jul. 2000.
doi:10.1109/22.848492
11. Lee, H.-M. and C.-M. Tsai, "Improved coupled-microstrip filter impedances," IEEE Trans. on Microw. Theory and Tech., Vol. 53, No. 9, 2812-2818, Sep. 2005.
doi:10.1109/TMTT.2005.854177
12. Velidi, V. K. and A. B. Guntupalli, "Sharp-rejection ultra-wide bandstop filters," IEEE Microw. Wireless Compon. Lett., Vol. 19, No. 8, 503-505, Aug. 2009.
doi:10.1109/LMWC.2009.2024834
13. Schiffman, B. and G. Matthaei, "Exact design of band-stop microwave filters," IEEE Trans. on Microw. Theory and Tech., Vol. 12, No. 1, 6-15, Jan. 1964.
doi:10.1109/TMTT.1964.1125744
14. Horton, M. and R. Menzel, "General theory and design of optimum quarter wave TEM filters," IEEE Trans. on Microw. Theory and Tech., Vol. 13, No. 5, 316-327, May 1965.
doi:10.1109/TMTT.1965.1125996
15. Mandal, M. K. and S. Sanyal, "Compact bandstop filter using signal interference technique," Electron. Lett., 110-111, Jan. 2007.
doi:10.1049/el:20072547
16. Divyabramham, K., M. K. Mandal, and S. Sanyal, "Sharp-rejection wideband bandstop filters," IEEE Microw. Wireless Compon. Lett., Vol. 18, No. 10, 662-664, Oct. 2008.
doi:10.1109/LMWC.2008.2003452
17. Mandal, M. K., K. Divyabramham, and V. K. Velidi, "Compact wideband bandstop filter with five transmission zeros," IEEE Microw. Wireless Compon. Lett., Vol. 22, No. 1, 4-6, Jan. 2012.
doi:10.1109/LMWC.2011.2173928
18. Mandal, M. K., K. Divyabramham, and S. Sanyal, "Compact, wideband bandstop filters with sharp rejection characteristic," IEEE Microw. Wireless Compon. Lett., Vol. 18, No. 10, 665-667, Oct. 2008.
doi:10.1109/LMWC.2008.2003454
19. Cui, D., Y. Liu, Y. Wu, S. Li, and C. Yu, "A compact bandstop filter based on two meandered parallel-coupled lines," Progress In Electromagnetics Research, Vol. 121, 271-279, 2011.
doi:10.2528/PIER11061902
20. Wu, Y. and Y. Liu, "A coupled-line band-stop filter with three-section transmission-line stubs and wide upper pass-band performance," Progress In Electromagnetics Research, Vol. 119, 407-421, 2011.
doi:10.2528/PIER11072003
21. Hsieh, M.-Y. and S.-M. Wang, "Compact and wideband microstrip bandstop filter," IEEE Microw. Wireless Compon. Lett., Vol. 15, No. 7, 472-474, Jul. 2005.
doi:10.1109/LMWC.2005.851572
Submit
