volume | PIER Journals

Abstract

A filter with good impedance matching for both in-band and a wide range of out-of-band is reported in this paper. Thus, the proposed filter offers low reflection for a wide range of frequencies, and it can be called as quasi-reflectionless filter. Also, the proposed filter improves the passband flatness significantly. The quasi-reflectionless filter consists of n-pole conventional U-shaped bandpass filters with absorptive stubs (ABSs) placed at the input and output ports. Each part in the whole filter is individually investigated. The U-shaped resonator is studied first, and then the ABSs are analyzed mathematically and simulated to optimize the attenuation rejection. Several parameters that have an influence on the overall performance are investigated. Different n-pole filters are simulated to simply enhance the out-of-band rejection without affecting the passband response. The filter response is furthermore improved by introducing two transmission zeros using the cross-coupling between the two ABSs. To validate the proposed idea, the 3-pole U-shaped quasi-reflectionless BPF is fabricated on an FR4 substrate at the operating frequency of 3.5 GHz. The filter has measured responses very close to the simulated ones.

1. Pozar, D. M., Microwave Engineering, 2nd Ed., Wiley, New York, NY, USA, 2012.

2. Morgan, M. A., Re ectionless Filters, Artech House, Norwood, MA, USA, 2017.

3. Morgan, M. A. and T. A. Boyd, "Theoretical and experimental study of a new class of reflectionless filter," IEEE Trans. Microw. Theory Techn., Vol. 59, No. 5, 1214-1221, May 2011.
doi:10.1109/TMTT.2011.2113189

4. Morgan, M. A., W. M. Groves, and T. A. Boyd, "Reflectionless filter topologies supporting arbitrary low-pass ladder prototypes," IEEE Trans. Circuits Syst. I, Reg. Papers, Vol. 66, No. 2, 594-604, Feb. 2019.
doi:10.1109/TCSI.2018.2872424

5. Hong, J.-S., Advances in Planar Filters Design, SciTech Publishing, London, U.K., 2019.
doi:10.1049/SBEW535E

6. Lee, J., B. Lee, S. Nam, and J. Lee, "Rigorous design method for symmetric reflectionless filters with arbitrary prescribed transmission response," IEEE Trans. Microw. Theory Techn., Vol. 68, No. 6, 2300-2307, Jun. 2020.
doi:10.1109/TMTT.2020.2976967

7. Morgan, M. A. and T. A. Boyd, "Relfectionless filter structures," IEEE Trans. Microw. Theory Techn., Vol. 63, No. 4, 1263-1271, Apr. 2015.
doi:10.1109/TMTT.2015.2403841

8. Luo, C., et al. "Quasi-re ectionless microstrip bandpass filters using bandstop filter for out-of-band improvement," IEEE Trans. Circuits Syst. II, Exp. Briefs, Vol. 67, No. 10, 1849-1853, Oct. 2020.
doi:10.1109/TCSII.2019.2946915

9. Gόmez-García, R., J.-M. Muñoz-Ferreras, and D. Psychogiou, "Highorder input-reflectionless bandpass/bandstop filters and multiplexers," IEEE Trans. Microw. Theory Techn., Vol. 67, No. 9, 3683-3695, Sep. 2019.
doi:10.1109/TMTT.2019.2924975

10. Khalaj-Amirhosseini, M. and M. Taskhiri, "Twofold reflectionless filters of inverse-chebyshev response with arbitrary attenuation," IEEE Trans. Microw. Theory Techn., Vol. 65, No. 11, 4616-4620, Nov. 2017.
doi:10.1109/TMTT.2017.2716940

11. Gomez-García, R., J. Muno-erreras, and D. Psychogiou, "Split-type input-reflectionless multiband filters," IEEE Microw. Compon. Lett., Vol. 28, No. 11, 981-983, Nov. 2018.
doi:10.1109/LMWC.2018.2868091

12. Gomez-García, R., J. Munoz-Ferreras, and D. Psychogiou, "Symmetrical quasi-absorptive RF bandpass filters," IEEE Trans. Microw. Theory Techn., Vol. 67, No. 4, 1472-1482, Apr. 2019.
doi:10.1109/TMTT.2019.2895531

13. Guyette, A. C., I. C. Hunter, R. D. Pollard, and D. R. Jachowski, "Perfectly matched bandstop filters using lossy resonators," IEEE MTT-S Int. Microw. Symp. Dig., Vol. 4, Jun. 2005.

14. Shao, J.-Y. and Y.-S. Lin, "Narrowband coupled-line bandstop filter with absorptive stopband," IEEE Trans. Microw. Theory Techn., Vol. 63, No. 10, 3469-3478, Oct. 2015.
doi:10.1109/TMTT.2015.2460752

15. Lee, T.-H., B. Kim, K. Lee, W. J. Chappell, and J. Lee, "Frequency-tunable low-Q lumped-element resonator bandstop filter with high attenuation," IEEE Trans. Microw. Theory Techn., Vol. 64, No. 11, 3549-3556, Nov. 201.
doi:10.1109/TMTT.2016.2604318

16. Hickle, M. D. and D. Peroulis, "Theory and design of frequency-tunable absorptive bandstop filters," IEEE Trans. Circuits Syst. I, Reg. Papers, Vol. 65, No. 6, 1862-1874, Jun. 2018.
doi:10.1109/TCSI.2017.2766206

17. Chien, S.-H. and Y.-S. Lin, "Novel wideband absorptive bandstop filters with good selectivity," IEEE Access, Vol. 5, 18847-18861, 2017.
doi:10.1109/ACCESS.2017.2752903

18. Kong, M., Y. Wu, Z. Zhuang, Y. Liu, and A. A. Kishk, "Compact wideband reflective/absorptive bandstop filter with multitransmission zeros," IEEE Trans. Microw. Theory Techn., Vol. 67, No. 2, 482-493, Feb. 2019.
doi:10.1109/TMTT.2018.2886847

19. Jeong, S., T. Lee, and J. Lee, "Absorptive filter prototype and distributed-element absorptive bandpass filter," Proc. IEEE MTTS Int. Conf. Numer. Electromagn. Multiphys. Model. Optim. (NEMO), 1-4, Aug. 2018.

20. Wu, X., Y. Li, and X. Liu, "High-order dual-port quasi-absorptive microstrip coupled-line bandpass filters," IEEE Trans. Microw. Theory Techn., Vol. 68, No. 4, 1462-1475, Apr. 2020.
doi:10.1109/TMTT.2019.2955692

21. Wu, X., Y. Li, and X. Liu, "Quasi-reflectionless microstrip bandpass filters with improved passband flatness and out-of-band rejection," IEEE Access, Vol. 8, 160500-160514, 2020.
doi:10.1109/ACCESS.2020.3021314

22. Cohn, S. and F. Coale, "Directional channel-separation filters," Proc. IRE, Vol. 44, No. 8, 1018-1024, Aug. 1956.
doi:10.1109/JRPROC.1956.275043

23. Cheng, Y., W. Hong, and K. Wu, "Half mode substrate integrated waveguide (HMSIW) directional filter," IEEE Microw. Wireless Compon. Lett., Vol. 17, No. 7, 504-506, Jul. 2007.
doi:10.1109/LMWC.2007.899309

24. Kim, J. P., "Improved design of single-section and cascaded planar directional filters," IEEE Trans. Microw. Theory Techn., Vol. 59, No. 9, 2206-2213, Sep. 2011.
doi:10.1109/TMTT.2011.2160871

25. Grebennikov, A., RF and Microwave Transmitter Design, 231-243, John Wiley and Sons, Inc., 2011.
doi:10.1002/9780470929308

26. Hong, J.-S. and M. J. Lancaster, Microstrip Filters for RF/Microwave Applications, John Wiley & Sons, New York, 2001.
doi:10.1002/0471221619

Dr. Bahaa Hamzah Alkhuwaildi

Dr. Nasr Alkhafaji