volume | PIER Journals

Abstract

In this paper, a compact and high isolation microstrip diplexer is designed for broadband and wireless local area network (WLAN) application, simultaneously. The bandpass filter (BPF) for broadband channel is formed by three-coupled-line structure and two short stubs with different size loaded in 50 feed lines, and the BPF for WLAN channel consists of two coupling quarter-wavelength resonators (QWR) and one open stub loaded in short parallel-coupling feed structure. Multiple transmission zeros can be generated due to their intrinsic characteristics, so the broadband BPF with sharp skirt and wide upper-stopband performance and the WLAN BPF with sharp roll-off and lower-stopband characteristic can be realized. The tapped stub not only can generate transmission zeros to deepen the stopband, but also can connect other BPF as an its part without deterioration of in-band performance. Hence, a compact microstrip diplexer combines of two BPFs without the extra junction matching network. The mutual loading effect approximately equivalent to a coupled short QWR can also generate new transmission zero at the passband edge to improve the isolation. A microstrip diplexer with the 3 dB fractional bandwidth (FBW) of 80% for broadband channel and 5% for WLAN channel is designed and fabricated. Good agreement between the simulated and measured results is observed.

1. Pozar, D. M., Microwave Engineering, Wiley, New York, 1998.
doi:10.1109/13.53636

2. Matthaei, G. and E. G. Cristal, "Multiplexer channel-separating units using interdigital and parallel-coupled filters," IEEE Transactions on Microwave Theory and Techniques, Vol. 13, 328-334, 1965.
doi:10.1109/TMTT.1965.1125997 Google Scholar

3. Wenzel, R. J., "Printed-circuit complementary filters for narrow bandwidth multiplexers ," IEEE Transactions on Microwave Theory and Techniques, Vol. 16, 147-157, 1968.
doi:10.1109/TMTT.1968.1126635 Google Scholar

4. Wang, R., J. Xu, M. Y. Wang, and Y. L. Dong, "Synthesis of microstrip resonator diplexers using linear frequency transformation and optimization," Progress In Electromagnetics Research, Vol. 124, 441-455, 2012.
doi:10.2528/PIER12011108 Google Scholar

5. Yang, T., P. L. Chi, and T. Itoh, "High isolation and compact diplexer using the hybrid resonators," IEEE Microstrip and Wireless Components Letters, Vol. 20, No. 10, 551-553, 2010.
doi:10.1109/LMWC.2010.2052793 Google Scholar

6. Huang, C. Y., M. H. Weng, C. S. Ye, and Y. X. Xu, "A high band isolation and wide stopband diplexer using dual-mode stepped-impedance resonators," Progress In Electromagnetics Research, Vol. 100, 299-308, 2010.
doi:10.2528/PIER09112701 Google Scholar

7. Yang, R. Y., C. M. Hsiung, C. Y. Hung, and C. C. Lin, "Design of a high band isolation diplexer for GPS and WLAN system using modified stepped-impedance resonators," Progress In Electromagnetics Research, Vol. 107, 101-114, 2010.
doi:10.2528/PIER10060913 Google Scholar

8. Shi, J., J. X. Chen, and Z. H. Bao, "Diplexers based on microstrip line resonators with loaded elements," Progress In Electromagnetics Research, Vol. 115, 423-439, 2011. Google Scholar

9. Zeng, H. Y., G. M. Wang, D. Z. Wei, and Y. W. Wang, "Planar diplexer using composite right-/left-handed transmission line under balanced condition," Electronics Letters, Vol. 48, No. 2, 104-106, 2012.
doi:10.1049/el.2011.2763 Google Scholar

10. Lin, Y.-L., S.-W. Lan, R.-Y. Yang, and C.-Y. Hung, "Design of a high band-isolation diplexer based on asymmetric stepped-impedance resonators with side-coupling structure," Journal of Electromagnetic Waves and Applications, Vol. 27, No. 1, 1-11, 2012. Google Scholar

11. Chen, C.-Y. and C.-C. Lin, "The design and fabrication of a highly compact microstrip dual-band bandpass filter," Progress In Electromagnetics Research, Vol. 112, 299-307, 2011. Google Scholar

12. Rezaee, P., M. Tayarani, and R. Knöchel, "Active learning method for the determination of coupling factor and external Q in microstrip filter design," Progress In Electromagnetics Research, Vol. 120, 459-479, 2011. Google Scholar

13. Chen, C. F., T. Y. Huang, C. P. Chou, and R. B. Wu, "Microstrip diplexers design with common resonator sections for compact size, but high isolation," IEEE Transactions on Microwave Theory and Techniques, Vol. 54, No. 5, 1945-1952, 2006.
doi:10.1109/TMTT.2006.873613 Google Scholar

14. Yang, T. P., L. Chi, and T. Itoh, "Compact quarter-wave resonator and its applications to miniaturized diplexer and triplexer," IEEE Transactions on Microwave Theory and Techniques, Vol. 59, No. 2, 260-269, 2011.
doi:10.1109/TMTT.2010.2095029 Google Scholar

15. Chuang, M. L. and M. T. Wu, "Microstrip diplexer design using common T-shaped resonator," IEEE Microwave and Wireless Components Letters, Vol. 21, No. 11, 583-585, 2011.
doi:10.1109/LMWC.2011.2168949 Google Scholar

16. Chen, C.-F., "Miniaturized and high isolation microstrip diplexers based on the tri-mode stubloaded stepped-impedance resonators," Journal of Electromagnetic Waves and Applications, Vol. 26, No. 14-15, 2001-2011, 2012.
doi:10.1080/09205071.2012.724155 Google Scholar

17. Garcia-Lamperez, A., M. Salazar-Palma, and T. K. Sarkar, "Analytical synthesis of microwave multiport networks," IEEE MTT-S Int. Microwave Symp. Digest, 455-458, 2004. Google Scholar

18. Skaik, T. F., M. J. Lancaster, and F. Huang, "Synthesis of multiple output coupled resonator circuits using coupling matrix optimisation," IET Microwaves, Antennas and Propagation, Vol. 5, No. 9, 1081-1088, 2011.
doi:10.1049/iet-map.2010.0447 Google Scholar

19. Skaik, T. F. and M. J. Lancaster, "Coupled resonator diplexer without external junctions," Journal of Electromagnetic Analysis and Applications, Vol. 3, No. 6, 238-241, 2011.
doi:10.4236/jemaa.2011.36038 Google Scholar

20. An, J., G. M. Wang, C. X. Zhang, and P. Zhang, "Diplexer using composite right-/left-handed transmission line," Electronics Letters, Vol. 44, No. 11, 685-687, 2008.
doi:10.1049/el:20083730 Google Scholar

21. Dong, Y. D. and T. Itoh, "Substrate integrated waveguide loaded by complementary split-ring resonators for miniaturized diplexer design," IEEE Microwave and Wireless Components Letters, Vol. 21, No. 1, 10-12, 2011.
doi:10.1109/LMWC.2010.2091263 Google Scholar

22. Quan, X. L., R.-L. Li, J. Y. Wang, and Y. H. Cui, "Development of a broadband horizontally polarized omnidirectional planar antenna and its array for base stations," Progress In Electromagnetics Research, Vol. 128, 441-456, 2012. Google Scholar

23. Islam, M. T., R. Azim, and A. T. Mobashsher, "Triple band-notched planar UWB antenna using parasitic strips," Progress In Electromagnetics Research, Vol. 129, 161-179, 2012. Google Scholar

24. Russo, I., L. Boccia, G. Amendola, and H. Schumacher, "Compact hybrid coaxial architecture for 3-10 GHz UWB quasi-optical power combiners," Progress In Electromagnetics Research, Vol. 122, 77-92, 2012.
doi:10.2528/PIER11101704 Google Scholar

25. Azim, R. and M. T. Islam, "Compact planar UWB antenna with band notch characteristics for WLAN and DSRC," Progress In Electromagnetics Research, Vol. 133, 391-406, 2013. Google Scholar

26. Ye, C. S., Y. K. Su, M. H. Weng, and C. Y. Hung, "A microstrip ring-like diplexer for bluetooth and UWB application," Microwave and Optical Technology Letters, Vol. 51, No. 6, 1518-1520, 2009.
doi:10.1002/mop.24358 Google Scholar

27. Weng, M. H., C. Y. Hung, and Y. K. Su, "A hairpin line diplexer for direct sequence ultra-wideband wireless communications," IEEE Microwave and Wireless Components Letters, Vol. 17, No. 7, 519-521, 2007.
doi:10.1109/LMWC.2007.899315 Google Scholar

28. Ma, D., Z. Y. Xiao, L. Xiang, X. Wu, C. Huang, and X. Kou, "Compact dual-band bandpass filter using folded SIR with two stubs for WLAN," Progress In Electromagnetics Research, Vol. 117, 357-364, 2011. Google Scholar

29. Panda, J. R. and R. S. Kshetrimayum, "A printed 2.4 GHz/5.8 GHz dual-band monopole antenna with a protruding stub in the ground plane for WLAN and RFID applications," Progress In Electromagnetics Research, Vol. 117, 425-434, 2011. Google Scholar

30. Nguyen, C. and K. Chang, "On the analysis and design of spurline band-stop filters," IEEE Transactions on Microwave Theory and Techniques, Vol. 33, No. 12, 1416-1421, 1985.
doi:10.1109/TMTT.1985.1133233 Google Scholar

31. Song, K. and Q. Xue, "Novel broadband bandpass filters using Y-shaped dual-mode microstrip resonators," IEEE Microwave and Wireless Components Letters, Vol. 19, No. 9, 548-550, 2009.
doi:10.1109/LMWC.2009.2027058 Google Scholar

32. Deng, H. W., Y. J. Zhao, X. S. Zhang, W. Chen, and L. Qiang, "Compact and high selectivity broadband bandpass filter with dual-mode folded-T-type resonator," Microwave and Optical Technology Letters, Vol. 53, No. 8, 1697-1700, 2011.
doi:10.1002/mop.26108 Google Scholar

33. Dai, G. L., Y. X. Guo, and M. Y. Xia, "Design of compact bandpass filter with improved selectivity using source-load coupling," Electronics Letters, Vol. 46, No. 7, 505-506, 2010.
doi:10.1049/el.2010.2841 Google Scholar

Dr. Hong-Wei Deng

Dr. Yong-Jiu Zhao

Dr. Yong Fu

Dr. Ji Ding

Dr. Xiao-Jun Zhou