A topology for a 3-dB broadband and small-size ring coupler is proposed. It consists of fullydistributed Composite Right-/Left-Handed phase shifters and a Lange coupler. For the fabricated coupler, the frequency bandwidth is one octave, centered on 1.5 GHz, while the footprint area is 25% compared to the conventional ring coupler topology. The experimental results are in good agreement with the expected ones, obtained by electromagnetic simulation.
2. Huo, J.-T. and C.-H. Tsai, "Generalized synthesis of rat race ring coupler and its application to circuit miniaturization," Progress In Electromagnetics Research, Vol. 108, 51-64, 2010.
3. Kim, D. I. and G. S. Yang, "Design of new hybrid-ring directional coupler using \l\8 or \l\6 sections," IEEE Trans. on Microwave Theory and Techniques, Vol. 39, No. 10, 1179-1784, 1991.
4. Coupez, J. P., A. Peden, and C. Person, "Analysis and design of ultra miniature hybrid ring directional coupler," Proc. 22nd European Microwave Conf., Vol. 1, 443-447, 1992.
5. Chuang, M. L., "Miniaturized ring coupler of arbitrary reduced size," IEEE Microwave and Wireless Components Letters, Vol. 15, No. 2, 16-18, 2005.
6. Simion, S., "Small-size ring coupler design method based on fully distributed composite right/left handed approach," Electronics Letters, Vol. 48, No. 23, 1481-1483, 2012.
7. Kim, D. I. and Y. Naito, "Broad-band design of improved hybrid-ring 3-dB directional couplers," IEEE Trans. on Microwave Theory and Techniques, Vol. 30, No. 11, 2040-2046, 1982.
8. Ho, C. H., L. Fan, and K. Chang, "Broadband uniplanar hybrid ring coupler," Electronics Letters, Vol. 29, No. 1, 44-45, 1993.
9. Murgulescu, M. H., M. Moisan, P. Legaud, E. Penard, and I. Zaquine, "New wideband, 0:67\l gcircumference 180 hybrid ring coupler ," Electronics Letters, Vol. 30, No. 4, 299-300, 1994.
10. Wang, T. and K. Wu, "Size-reduction and band-broadening design technique of uniplanar hybrid ring coupler using phase inverter for M(H)MIC's," IEEE Trans. on Microwave Theory and Techniques, Vol. 47, No. 2, 198-206, 1999.
11. March, S., "A wideband stripline hybrid ring," IEEE Trans. on Microwave Theory and Techniques, Vol. 61, No. 6, 361, 1968.
12. Ahn, H. R. and B. Kim, "Small wideband coupled-line ring hybrids with no restriction on coupling power," IEEE Trans. on Microwave Theory and Techniques, Vol. 57, No. 7, 1806-1817, 2009.
13. Simion, S., "Design method of miniaturized ring coupler using phase shifters consisting of fully-distributed composite right/left-handed structures," Progress In Electromagnetics Research B, Vol. 50, 61-76, 2013.
14. Chi, P. L., "Miniaturized ring coupler with arbitrary power divisions based on the composite right/left-handed transmission lines," IEEE Microwave and Wireless Components Letters, Vol. 22, No. 4, 170-172, 2012.
15. Okabe, H., C. Caloz, and T. Itoh, "A compact enhanced-bandwidth hybrid ring using an artificial lumped-element left-handed transmission-line section," IEEE Trans. on Microwave Theory and Techniques, Vol. 52, No. 3, 798-804, 2004.