volume | PIER Journals

Abstract

A planar bandpass filter is proposed in this paper. Its stopband is realized by using the concept of bandstop filter. A key merit of the filter configuration is that the position of the transmission zeros can be conveniently controlled whereas the bandwidth is fixed. The bandpass filter is realized using open circuited uniform impedance resonator and stepped impedance resonators. With five reflection zeros generated in the passband, ten controllable transmission zeros are introduced to sharpen the passband skirts. Skirt selectivity can be freely controlled by tuning the impedance ratio of the stepped impedance resonators. Without coupling gaps between resonators, the structure of the filter is simple and easy to fabricate. To illustrate the concept, a bandpass filter with ten transmission zeros is designed, fabricated and measured. Simulated and measured results are found to be in good agreement with each other, with insertion loss in the passbands less than 1 dB.

1. Deng, P.-H., C.-H. Wang, and C.-H. Chen, "Novel broadside-coupled bandpass filters using both microstrip and coplanar-waveguide resonators," IEEE Trans. Microw. Theory Tech., Vol. 54, No. 10, 3746-3750, Oct. 2006.
doi:10.1109/TMTT.2006.881619

2. Liang, C.-H. and C.-Y. Chang, "Compact wideband bandpass filters using stepped-impedance resonators and interdigital coupling structures," IEEE Microw. Wireless Compon. Lett., Vol. 19, No. 9, 551-553, Sep. 2009.
doi:10.1109/LMWC.2009.2027060

3. Shaman, H. and J.-S. Hong, "A novel ultra-wideband (UWB) bandpass filter (BPF) with pairs of transmission zeros," IEEE Microw. Wireless Compon. Lett., Vol. 17, No. 2, 121-123, Feb. 2007.
doi:10.1109/LMWC.2006.890335

4. Wang, H. and Q.-X. Chu, "A narrow-band hairpin-comb two-pole filter with source-load coupling," IEEE Microw. Wireless Compon. Lett., Vol. 20, No. 7, 372-374, Jul. 2010.
doi:10.1109/LMWC.2010.2049426

5. Chiang, C.-P. and K.-W. Tam, "Compact quasi-elliptic microstrip bandpass filter using terminated anti-parallel coupled-line," IET Proc. Microw. Antenna Propag., Vol. 3, 1206-1210, 2009.
doi:10.1049/iet-map.2008.0285

6. Li, J.-Y., C.-H. Chi, and C.-Y. Chang, "Synthesis and design of generalized Chebyshev wideband hybrid ring based bandpass filters with a controllable transmission zero pair," IEEE Trans. Microw. Theory Tech., Vol. 58, No. 12, 3720-3731, Dec. 2010.

7. Li, L. and Z.-F. Li, "Side-coupled shorted microstrip line for compact quasi-elliptic wideband bandpass filter design," IEEE Microw. Wireless Compon. Lett., Vol. 20, No. 6, 322-324, Jun. 2010.
doi:10.1109/LMWC.2010.2047516

8. Shaman, H. and J.-S. Hong, "Input and output cross-coupled wideband bandpass filter," IEEE Trans. Microw. Theory Tech., Vol. 55, No. 12, 2562-2568, Dec. 2007.
doi:10.1109/TMTT.2007.910066

9. Hsieh, L.-H. and K. Chang, "Compact, low insertion-loss, sharp-rejection, and wideband microstrip bandpass filters," IEEE Trans. Microw. Theory Tech., Vol. 51, No. 4, 1241-1246, Apr. 2003.
doi:10.1109/TMTT.2003.809643

10. Gómez-García, R. and J. I. Alonso, "Design of sharp-rejection and low-loss wideband 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

11. Tu, W.-H., "Broadband microstrip bandpass filters using triple-mode resonator," IET Proc. Microw. Antenna Propag., Vol. 4, 1275-1282, 2010.
doi:10.1049/iet-map.2009.0106

12. Chen, F. C., J. M. Qiu, Z. H. Chen, and Q. X. Chu, "Low insertion loss wideband bandpass filter with six transmission zeros," Electron. Lett., Vol. 49, No. 7, 477-479, Mar. 2013.
doi:10.1049/el.2013.0655

13. Mandal, M. K., P. Mondal, and S. Sanyal, "Low insertion loss, wideband bandpass filters with sharp rejection characteristics," IET Proc. Microw. Antenna Propag., Vol. 4, 99-105, 2010.
doi:10.1049/iet-map.2008.0161

14. Velidi, V. K., A. B. Guntupalli, and S. Sanyal, "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

15. Malherbe, J. A. G., "Wideband bandstop filter with sub-harmonic stubs," Electron. Lett., Vol. 47, No. 10, 604-605, May 2011.
doi:10.1049/el.2011.0604

16. Malherbe, J. A. G., "Pseudo-elliptic bandstop filter with 1 : 2 : 3 harmonic ratio stubs," Electron. Lett., Vol. 49, No. 2, 130-132, Jan. 2013.
doi:10.1049/el.2012.3695

17. Pozar, D. M., Microwave Engineering, 2nd Ed., Wiley, 1998.

Dr. Yun Wang

Dr. Fu-Chang Chen

Prof. Qing-Xin Chu