In this paper, a high performance diplexer is designed and fabricated for Global Positioning System (GPS) and wireless local area network (WLAN) applications simultaneously. The diplexer mainly comprises two dual-mode ring bandpass filters (BPFs), operated at 1.575 GHz and 2.4 GHz, respectively. By using the stepped-impedance resonator (SIR) in the BPFs, the size reduction and wide stopband from 2.8 GHz to 6 GHz are obtained. Moreover, several transmission zeros are located at the passband edges, thus improving the passband selectivity. Due to impedance matching between two BPFs, a high isolation greater than 40 dB between two channels is obtained. The diplexer is investigated numerically and experimentally. The simulated and measured results have a good agreement with the proposed design concept.
2. Strassner, B. and K. Chang, "Wide-band low-loss high-isolation microstrip periodic-stub diplexer for multiple-frequency applications," IEEE Trans. Microw. Theory Tech., Vol. 49, 1818-1820, 2001.
3. 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 Trans. Microw. Theory Tech., Vol. 54, 1945-1952, 2006.
4. Han, S., X.-L.Wang, Y. Fan, Z. Yang, and Z. He, "The generalized Chebyshev substrate integrated waveguide diplexer," Progress In Electromagnetics Research, Vol. 73, 29-38, 2007.
5. Deng, P. H., C. H. Wang, and C. H. Chen, "Compact microstrip diplexers based on a dual-passband filter," Proceedings of Asia-Pacific Microwave Conference, 2006.
6. Weng, M. H., C. Y. Hung, and Y. K. Su, "A hairpin line diplexer for direct sequence ultra-wideband wireless communications," IEEE Microw. Wireless Compon. Lett., Vol. 17, 519-521, 2007.
7. Gao, S. S., X. S. Yang, J. P. Wang, S. Q. Xiao, and B. Z. Wang, "Compact ultra-wideband (UWB) bandpass filter using modified stepped impedance resonator," Journal of Electromagnetic Waves and Applications, Vol. 22, No. 4, 541-548, 2008.
8. Chin, K.-S. and D.-J. Chen, "Novel microstrip bandpass filters using direct-coupled triangular stepped-impedance resonators for spurious suppression," Progress In Electromagnetics Research Letters, Vol. 12, 11-20, 2009.
9. He, Z. R., X. Q. Lin, and Y. Fan, "Improved stepped-impedance resonator (SIR) bandpass filter in Ka-band," Journal of Electromagnetic Waves and Applications, Vol. 23, No. 8-9, 1181-1190, 2009.
10. Zhao, L.-P., X. Zhai, B. Wu, T. Su, W. Xue, and C.-H. Liang, "Novel design of dual-mode bandpass filter using rectangle structure," Progress In Electromagnetics Research B, Vol. 3, 131-141, 2008.
11. Dai, X.-W., C.-H. Liang, G. Li, and Z.-X. Chen, "Novel dual-mode dual-band bandpass filter using microstrip meander-loop resonators," Journal of Electromagnetic Waves and Applications, Vol. 22, No. 4, 573-580, 2008.
12. Esfeh, B. K., A. Ismail, R. S. A. Raja Abdullah, H. Adamand, and A. R. H. Alhawari, "Compact narrowband bandpass filter using dual-mode octagonal meandered loop resonator for wimax application," Progress In Electromagnetics Research B, Vol. 16, 277-290, 2009.
13. Kuo, J. T. and C. Y. Tsai, "Periodic stepped-impedance ring resonator (PSIRR) bandpass filter with a miniaturized area and desirable upper stopband characteristics," IEEE Trans. Microw. Theory Tech., Vol. 54, 1107-1112, 2006.
14. Choi, W. W. and K. W. Tam, "A microstrip SIR dual-mode bandpass filter with simultaneous size reduction and spurious responses suppression," IEEE MTT-S International Microwave Workshop Series on Art of Miniaturizing RF and Microwave Passive Components, Chengdu, China, 2008.
15., "IE3D Simulator,", Zeland Software, Inc., 1997.
16. Thomson, N. and J. S. Hong, "Compact ultra-wideband microstrip/coplanar waveguide bandpass filter," IEEE Microw. Wireless Compon. Lett., Vol. 17, 184-186, 2007.