volume | PIER Journals

Abstract

In this paper, a highly efficient microstrip diplexer with low insertion loss, high selectivity, and high isolation is introduced. The proposed diplexer employed two compact size coupled squared open-loop resonator (SOLR) based band pass filters (BPFs). Firstly, a matching network is utilized to ensure that the two BPFs and the antenna load are properly matched. This is accomplished by connecting the two BPFs and the antenna with a conventional T-junction that acts as a combining circuit, resulting in good isolation between the up-link and down-link BPFs. As a second step, a defected ground structure (DGS) is used to improve the overall filter response in terms of insertion loss and isolation without affecting the diplexer selectivity. Based on this structure, the proposed diplexer has two resonance frequencies of 2.5 GHz and 2.8 GHz. The structure provides good insertion losses of about 1.6 and 1.3 dB for the two channels, respectively with fractional bandwidth of 2.8% at 2.5 GHz and 3.2% at 2.8 GHz. The measured isolation levels are 70 dB and 50 dB for 2.5 GHz and 2.8 GHz, respectively. The proposed diplexer is useful for several wireless communication applications such as WiMAX. The good agreements between simulated and measured results verified the practical validation of the proposed diplexer.

1. Tang, H. J., W. Hong, J.-X. Chen, G. Q. Luo, and K. Wu, "Development of millimeter-wave planar diplexers based on complementary characters of dual-mode substrate integrated waveguide filters with circular and elliptic cavities," IEEE Transactions on Microwave Theory and Techniques, Vol. 55, 776-782, 2007.
doi:10.1109/TMTT.2007.893655

2. Konpang, J., "A compact diplexer using square open loop with stepped impedance resonators," 2009 IEEE Radio and Wireless Symposium, 91-94, 2009.
doi:10.1109/RWS.2009.4957292

3. Duan, Q., K. Song, F. Chen, and Y. Fan, "Compact wide-stopband diplexer using dual mode resonators," Electronics Letters, Vol. 51, 1085-1087, 2015.
doi:10.1049/el.2015.0745

4. Yang, T., P.-L. Chi, and T. Itoh, "High isolation and compact diplexer using the hybrid resonators," IEEE Microwave and Wireless Components Letters, Vol. 20, 551-553, 2010.
doi:10.1109/LMWC.2010.2052793

5. Bui, D., T. Vuong, B. Allard, J. Verdier, and P. Benech, "Compact low-loss microstrip diplexer for RF energy harvesting," Electronics Letters, Vol. 53, 552-554, 2017.
doi:10.1049/el.2017.0022

6. Guan, X., F. Yang, H. Liu, and L. Zhu, "Compact and high-isolation diplexer using dual-mode stub-loaded resonators," IEEE Microwave and Wireless Components Letters, Vol. 24, 385-387, 2014.
doi:10.1109/LMWC.2014.2313591

7. Xu, K. D., M. Li, Y. Liu, Y. Yang, and Q. H. Liu, "Design of triplexer using E-stub-loaded composite right-/left-handed resonators and quasi-lumped impedance matching network," IEEE Access, Vol. 6, 18814-18821, 2018.
doi:10.1109/ACCESS.2018.2819641

8. Li, M., K. D. Xu, J. Ai, and Y. Liu, "Compact diplexer using short stub-loaded composite right/left-handed resonators," Microwave and Optical Technology Letters, Vol. 59, 1470-1474, 2017.
doi:10.1002/mop.30565

9. Hong, J.-S. and M. J. Lancaster, "Couplings of microstrip square open-loop resonators for cross-coupled planar microwave filters," IEEE Transactions on Microwave Theory and Techniques, Vol. 44, 2099-2109, 1996.
doi:10.1109/22.543968

10. Cheng, F., C. Gu, B. Zhang, Y. Yang, and K. Huang, "High isolation substrate integrated waveguide diplexer with exible transmission zeros," IEEE Microwave and Wireless Components Letters, Vol. 30, 1029-1032, 2020.
doi:10.1109/LMWC.2020.3025698

11. Mahmoud, N., A. Barakat, M. Nasr, and R. K. Pokharel, "Performance enhancement of 60 GHz CMOS band pass filter employing oxide height virtual increase," Progress In Electromagnetics Research, Vol. 77, 125-134, 2019.
doi:10.2528/PIERM18101608

12. Hussein, A. H., H. H. Abdullah, M. A. Attia, and A. M. Abada, "S-band compact microstrip full-duplex tx/rx patch antenna with high isolation," IEEE Antennas and Wireless Propagation Letters, Vol. 18, 2090-2094, 2019.
doi:10.1109/LAWP.2019.2937769

13. Sharma, R. Y., T. Chakravarty, S. Bhooshan, and A. B. Bhattacharyya, "Design of a novel 3 dB microstrip backward wave coupler using defected ground structure," Progress In Electromagnetics Research, Vol. 65, 261-273, 2006.
doi:10.2528/PIER06100502

14. Pandit, S., A. Mohan, P. Ray, and B. Rana, "Compact four-element MIMO antenna using DGS for WLAN Applications," 2018 International Symposium on Antennas and Propagation (ISAP), 1-2, 2018.

15. Lee, H., C.-T. M. Wu, and T. Itoh, "Study and analysis of contiguous channel triplexer based on combining method of two filtering circuits using CRLH and RH isolation circuits," International Journal of Microwave and Wireless Technologies, Vol. 6, 287-295, 2014.
doi:10.1017/S1759078714000178

16. Hong, J.-S. G. and M. J. Lancaster, Microstrip Filters for RF/Microwave Applications, Vol. 167, John Wiley & Sons, 2004.

17. Yao, H.-W., A. E. Abdelmonem, J.-F. Liang, X.-P. Liang, K. A. Zaki, and A. Martin, "Wide-band waveguide and ridge waveguide T-junctions for diplexer applications," IEEE Transactions on Microwave Theory and Techniques, Vol. 41, 2166-2173, 1993.
doi:10.1109/22.260702

18. Khandelwal, M. K., B. K. Kanaujia, and S. Kumar, "Defected ground structure: Fundamentals, analysis, and applications in modern wireless trends," International Journal of Antennas and Propagation, Vol. 2017, 2017.
doi:10.1155/2017/2018527

19. Li, Q., Y. Zhang, and C. T. M. Wu, "Compact and high-isolation microstrip diplexer using distributed coupling feeding line," Microwave and Optical Technology Letters, Vol. 60, 192-196, 2018.
doi:10.1002/mop.30938

20. Xiao, J.-K., M. Zhu, Y. Li, L. Tian, and J.-G. Ma, "High selective microstrip bandpass filter and diplexer with mixed electromagnetic coupling," IEEE Microwave and Wireless Components Letters, Vol. 25, 781-783, 2015.
doi:10.1109/LMWC.2015.2495194

21. Tizyi, H., F. Riouch, A. Tribak, A. Najid, and A. Mediavilla, "Microstrip diplexer design based on two square open loop bandpass filters for RFID applications," International Journal of Microwave and Wireless Technologies, Vol. 10, 412, 2018.
doi:10.1017/S1759078718000314

22. Zhang, P., M.-H. Weng, and R.-Y. Yang, "A compact wideband diplexer using stub-loaded square ring resonators," Electromagnetics, Vol. 41, 167-184, 2021.
doi:10.1080/02726343.2021.1903204

23. Hassan, A. Y., M. F. Hagag, A. A. Abdel Aziz, and M. A. Abdalla, "A compact diplexer using coupled π-CRLH zeroth resonators," IETE Journal of Research, 1-8, 2021.
doi:10.1080/03772063.2021.1909505

Dr. Asmaa E. Ammar

Dr. Nessim Mahmoud

Dr. Mohmoud Ahmed Attia Ali

Professor Amr Hussein Hussein Abdullah