volume | PIER Journals

Abstract

This paper presents a new design concept of dual bandpass filter. Based on the strong coupling between two resonators, a dual 1-pole band-pass filter is designed and is used as the basic building block. By providing appropriate weak coupling between these building blocks, a higher-order dual bandpass filter can be realized. In addition, these building blocks can be stacked vertically and/or horizontally to construct a compact filter. In this way, by using 3D full wave EM and circuit co-simulation, the simulation time required in the design stage can be reduced. In addition, it also provides a way to post-tune each building block individually and further reduces the time required in prototype post tuning process. For demonstration, an L-band dual 4-pole bandpass filter is designed with passband frequencies of 1.23 GHz~1.255 GHz and 1.55 GHz~1.6 GHz. In order to reduce the size of the filter and obtain a wide stopband bandwidth, a suitable evanescent mode cavity is used to realize the resonant structure. The measurement result shows that the insertion losses of the low passband and high passband are 1.03 dB~2.00 dB and 1.02 dB~1.75 dB, respectively; the return loss of both passbands is better than 15 dB. Furthermore, up to 5 GHz (> 3fo, where fo is at 1.39 GHz), the stopband rejection level is better than 80 dB.

1. Pozar, D. M., Microwave Engineering, John Wiley & Sons, 2009.

2. Cameron, R. J., C. M. Kudsia, and R. R. Mansour, Microwave Filters for Communication Systems: Fundamentals, Design and Applications, 2nd Ed., Wiley, Hoboken, NJ, USA, 2018.
doi:10.1002/9781119292371

3. Tsai, L.-C. and C.-W. Hsue, "Dual-band bandpass filters using equal-length coupled-serial-shunted lines and Z-transform technique," IEEE Transactions on Microwave Theory and Techniques, Vol. 52, No. 4, 1111-1117, 2004.
doi:10.1109/TMTT.2004.825680

4. Sekar, V. and K. Entesari, "A novel compact dual-band half-mode substrate integrated waveguide bandpass filter," IEEE MTT-S International Microwave Symposium Digest. IEEE MTT-S International Microwave Symposium, 1-4, 2011.

5. Wu, Y., "Compact microwave dual-band bandpass filter design,", University of York, 2017.

6. Chen, J. and X. Liu, "Design of an evanescent-mode tunable dual-band filter," 2016 IEEE/MTT-S International Microwave Symposium, MTT, 2016.

7. Kou, X., Z.-Y. Xiao, C.-Y. Huang, H. Li, and J.-J. Chu, "Design of dual-band cavity filter using frequency transformation method," Journal of Electronics & Information Technology, Vol. 34, 1489-1493, 2012.
doi:10.3724/SP.J.1146.2011.01151

8. Chomtong, P. and P. Akkaraekthalin, "A dual-band cavity bandpass filter using interdigital technique," ECTI 2015, 261-264, 2015.

9. Chen, F.-C., J.-M. Qiu, S.-W. Wong, and Q.-X. Chu, "Dual-band coaxial cavity bandpass filter with helical feeding structure and mixed coupling," IEEE Microwave and Wireless Components Letters, Vol. 25, No. 1, 31-33, 2014.
doi:10.1109/LMWC.2014.2369965

10. Naeem, U., A. Perigaud, and S. Bila, "Dual-mode dual-band bandpass cavity filters with widely separated passbands," IEEE Transactions on Microwave Theory and Techniques, Vol. 65, No. 8, 2681-2686, 2017.
doi:10.1109/TMTT.2017.2723880

11. Lee, J., M. S. Uhm, and I.-B. Yom, "A dual-passband filter of canonical structure for satellite applications," IEEE Microwave and Wireless Components Letters, Vol. 14, No. 6, 271-273, 2004.
doi:10.1109/LMWC.2004.828026

12. Stefanovski, S., M. Potrebic, D. Toic, and Z. Stamenkovic, "A novel compact dual-band bandpass waveguide filter," 2015 IEEE 18th International Symposium on Design and Diagnostics of Electronic Circuits & Systems, 51-56, 2015.
doi:10.1109/DDECS.2015.37

13. Stefanovski, S., M. Potrebic, D. Tosic, and Z. Stamenkovic, "“Compact dual-band bandpass waveguide filter with H-plane inserts," Journal of Circuits, Systems and Computers, Vol. 25, No. 3, 1640015, 2016.
doi:10.1142/S0218126616400156

14. Macchiarella, G. and S. Tamiazzo, "Design techniques for dual-passband filters," IEEE Transactions on Microwave Theory and Techniques, Vol. 53, No. 11, 3265-3271, 2005.
doi:10.1109/TMTT.2005.855749

15. Almorqi, S., H. Shaman, J. S. Hong, and O. M. Haraz, "Design of a compact dual-band folded-waveguide bandpass filter using multilayer waveguide resonators," International Journal of RF and Microwave Computer-Aided Engineering, Vol. 25, No. 9, 780-788, 2015.
doi:10.1002/mmce.20916

16. CST Computer Simulation Technology AG, https://www.cst.com/..

17. Jarry, P. and J. Beneat, Advanced Design Techniques and Realizations of Microwave and RF Filters, Wiley Online Library, 2008.
doi:10.1002/9780470294178

18. Craven, G. F. and C. Mok, "The design of evanescent mode waveguide bandpass filters for a prescribed insertion loss characteristic," IEEE Transactions on Microwave Theory and Techniques, Vol. 19, No. 3, 295-308, 1971.
doi:10.1109/TMTT.1971.1127503

Dr. Sek-Meng Sow

Dr. Peng Tan

Dr. Jian Lu