In this paper a miniaturized branch-line coupler is proposed. The topology of the circuit is designed using novel design of T-model approach with open stubs with high-low impedances, which provides necessary bandwidth for WLAN band at 2.45GHz. The miniaturized branch-line coupler is designed and fabricated with a low-cost FR4 substrate as a platform in producing significantly reduction by more than 64.21% compared to the conventional coupler on inexpensive board. Furthermore, the coupler can equally divide the input signal with 90° phase of difference while maintaining the initial power from the source.
1. Maas, S. A., Microwave Mixers, Artech House, Norwood, MA, 1986.
2. Riblet, G. P., "A directional coupler with very flat coupling," IEEE Trans. Microw. Theory Tech., Vol. 26, No. 2, 70-74, Feb. 1978. doi:10.1109/TMTT.1978.1129315
3. Banba, S., T. Hasegawa, and H. Ogawa, "Multilayer MMIC branch-line hybrid using thin dielectric layers," IEEE Microw. Guided Wave Lett., Vol. 1, No. 11, 346-347, Nov. 1991. doi:10.1109/75.93907
4. Muraguchi, M., T. Yukitake, and Y. Naito, "Optimum design of 3-dB branch-line couplers using microstrip lines," IEEE Trans. Microw. Theory Tech., Vol. 31, No. 8, 674-678, Aug. 1983. doi:10.1109/TMTT.1983.1131568
5. Lin, C. T., C. L. Liao, and C. H. Chen, "Finite-ground coplanar-waveguide branch-line couplers," IEEE Trans. Microw. Wireless Compon. Lett., Vol. 11, No. 3, 127-129, Mar. 2001. doi:10.1109/7260.915626
6. Weng, L. H., Y. C. Guo, X. W. Shi, and X. Q. Chen, "An overview on defected ground structures," Progress In Electromagnetics Research B, Vol. 7, 173-189, 2008. doi:10.2528/PIERB08031401
7. Caulton, M., B. Hershenov, S. P. Knight, and R. E. Debrecht, "Status of lumped elements in microwave integrated circuit-present and future," IEEE Trans. Microw. Theory Tech., Vol. 9, No. 7, 588-599, Jul. 1971.
8. Chiang, Y. C. and C. Y. Chen, "Design of a wide-band lumped-element 3-dB quadrature coupler," IEEE Trans. Microw. Theory Tech., Vol. 49, No. 3, 476-479, Mar. 2001. doi:10.1109/22.910551
9. Hirota, T., A. Minakaw, and M. Muraguchi, "Reduced-size branch-line and rat-race hybrids for uniplanar MMIC's," IEEE Trans. Microw. Theory Tech., Vol. 38, No. 3, 270-275, Mar. 1990. doi:10.1109/22.45344
10. Singh, R. B. and T. M.Weller, "Miniaturized 20 GHz CPW quadrature coupler using capacitive loading," Microw. Opt. Technol. Lett., Vol. 30, No. 1, 3-5, Jul. 2001. doi:10.1002/mop.1203
11. Tung, W. S., H. H. Wu, and Y. C. Chiang, "Design of microwave wideband quadrature hybrid using planar transformer coupling method," IEEE Trans. Microw. Theory Tech., Vol. 51, No. 7, 1852-1856, Jul. 2003. doi:10.1109/TMTT.2003.814311
12. Scardelletti, M. C., G. E. Ponchak, and T. M. Weller, "Miniaturized Wilkinson power dividers utilizing capacitive loading," IEEE Microw. Wireless Compon. Lett., Vol. 12, No. 1, 6-8, Jan. 2002. doi:10.1109/7260.975717
13. Wang, C. W., T. G. Ma, and C. F. Yang, "A new planar artificial transmission line and its applications to a miniaturized butler matrix," IEEE Trans. Microw. Theory Tech., Vol. 55, No. 12, 2792-2801, 2007. doi:10.1109/TMTT.2007.909474
14. Shum, K. M., Q. Xue, and C. H. Chan, "A novel microstrip ring hybrid incorporating a PBG cell," IEEE Microw. and Wirel Compon. Lett., Vol. 11, No. 6, 258-260, 2001. doi:10.1109/7260.928931
15. Settaluri, R. K., G. Sundberg, A. Weisshaar, and V. K. Tripathi, "Compact folded line rat-race hybrid couplers," IEEE Trans. Microw. Theory Tech., Vol. 10, No. 2, 61-63, Feb. 2000..
16. Chen, W. L. and G. M. Wang, "Design of novel miniaturizedfractal-shaped branch-line couplers," Asia-Pasic Microwave Conf., APMC 2007, 13, Dec. 11-14, 2007.
17. Sun, K. O., S. J. Ho, C. C. Yen, and D. Weide, "A compact branch-line coupler using discontinuous microstrip lines," IEEE Microw. and Wirel. Compon. Lett., Vol. 15, No. 8, 519-520, 2005. doi:10.1109/LMWC.2005.852789
18. Tang, C. W., M. G. Chen, and J. W. Wu, "Realization of ultra-compact planar microstrip branch-line couplers with high-impedance open stubs," IEEE/MTT-S Intern. Symp. Microw., 995-998, Jun. 3-8, 2007.