A 3-dB branch-line hybrid coupler with wide stopband responses is presented in this letter. An equivalent K-inverter with bandpass function is used instead of one quarter-wavelength transmission line, which will realize size reduction and wide stopband characteristic of the coupler. Prototype of a branch-line hybrid coupler, which divides the power equally with 90° phase difference between the output ports, is also fabricated and tested. Both the simulation and measurement results show that such a hybrid coupler exhibits an 83.2% size reduction and has transmission suppression of -20 dB or less within five-fold bandwidth.
"A Miniaturized Filtering 3-dB
Branch-Line Hybrid Coupler with Wide Suppression Band," Progress In Electromagnetics Research Letters,
Vol. 73, 83-89, 2018. doi:10.2528/PIERL17111406
1. Jung, S. C., R. Negra, and F. M. Ghannouchi, "A design methodology for miniaturized 3-dB branch-line hybrid couplers using distributed capacitors printed in the inner area," IEEE Trans. Microw. Theory Techn., Vol. 56, No. 12, 2950-2953, 2008. doi:10.1109/TMTT.2008.2007323
2. Tsai, K. Y., H. S. Yang, and J. H. Chen, "A miniaturized 3-dB branch-line hybrid coupler with harmonics suppression," IEEE Microw. Wirel. Compon. Lett., Vol. 21, No. 10, 537-539, 2011. doi:10.1109/LMWC.2011.2164901
3. Li, B., X. Wu, and W. Wu, "A miniaturized branch-line coupler with wideband harmonics suppression," Progress In Electromagnetics Research Letters, Vol. 17, 181-189, 2010. doi:10.2528/PIERL10082602
4. Tseng, C. H. and C. L. Chang, "A rigorous design methodology for compact planar branch-line and rat-race couplers with asymmetrical T-structures," IEEE Trans. Microw. Theory Techn., Vol. 60, No. 7, 2085-2092, 2012. doi:10.1109/TMTT.2012.2195019
5. Johan, J. and J. W. Odendaal, "Design of compact planar rat-race and branch-line hybrid couplers sing polar curves," Microw. Opt. Technol. Lett., Vol. 57, No. 11, 2637-2640, 2015. doi:10.1002/mop.29397
6. Wang, Y., K. Ma, and S. Mou, "A compact branch-line coupler using substrate integrated suspended line technology," IEEE Microw. Wirel. Compon. Lett., Vol. 26, No. 2, 95-97, 2017. doi:10.1109/LMWC.2016.2517158
7. Uchida, H., N. Yoneda, Y. Konishi, and S. Makino, "Bandpass directional couplers with electromagnetically-coupled resonators," 2006 IEEE MTT-S International Microwave Symposium Digest, 1563-1566, 2006.
8. Wong, Y. S., S. Y. Zheng, and W. S. Chan, "A wideband coupler with wide suppression band using coupled-stub," Proceedings of the Asia-Paci¯c Microwave Conference, 1058-1061, 2011.
9. Wang, C., Y. Li, and N. Y. Kim, "A compact 3-dB 90± directional coupler in integrated passive devices manufacturing process for LTE applications," 2014 3rd Asia-Paci¯c Conference, Antennas and Propagation (APCAP), 1291-1292, 2014.
10. Lin, T. W., C. H. Lin, K. C. Huang, and J. T. Kuo, "Compact branch-line coupler ¯lter with transmission zeros," 2015 Asia-Paci¯c Microwave Conference (APMC), 1-3, 2015.
11. Wang, K. X., X. Y. Zhang, S. Y. Zheng, and Q. Xue, "Compact ¯ltering rat-race hybrid with wide stopband," IEEE Trans. Microw. Theory Techn., Vol. 63, No. 8, 2550-2560, 2015. doi:10.1109/TMTT.2015.2444841
12. Pozar, D. M., Microwave Engineering, Vol. 3rd, John Wiley and Sons Inc., 2014.
13. Kim, J. and J.-G. Yook, "A miniaturized 3-dB 90± hybrid coupler using coupled-line section with spurious rejection," IEEE Microw. Wirel. Compon. Lett., Vol. 24, No. 11, 766-768, 2014. doi:10.1109/LMWC.2014.2359157
14. Kumar, K. V. P. and S. S. Karthikeyan, "Miniaturized quadrature hybrid coupler using modi¯ed T-shaped transmission line for wide-range harmonic suppression," IET Microwaves, Antennas Propag., Vol. 10, No. 14, 1522-1527, 2016. doi:10.1049/iet-map.2016.0301