This paper presents a novel design of miniaturized microstrip quadrature coupler at 2.45 GHz. The design topology is based on reduced transmission line branch arms using recursively loaded stubs that contribute to the compact size. The proposed coupler result in a size reduction of 70.4% when compared to a conventional branch line hybrid. The designed coupler provides, at the operating frequency, a 25 dB isolation and exhibits equal power division at the output ports with quadrature phase difference. A fabricated prototype is developed with simulation and measurement in close agreement.
2. Fooks, E. H. and R. A. Zakarevicius, Microwave Engineering Using Microwave Circuits, Prentice Hall, New York, 1990.
3. Ghali, H. and T. A. Moselhy, "Miniaturized fractal rat-race, branch-line, and coupled-line hybrids," IEEE Transactions on Microwave Theory and Techniques, Vol. 52, No. 11, 2513-2520, Nov. 2004.
4. Sun, K. O., S. J. Ho, C. C. Yen, and D. Weide, "A compact branch-line coupler using discontinuous microstrip lines," IEEE Microwave and Wireless Technology Letters, Vol. 15, No. 8, 519-520, 2005.
5. Liao, S. S., P. T. Sun, N. C. Chin, and J. T. Peng, "A novel compact size branch-line coupler," IEEE Microwave and Wireless Technology Letters, Vol. 15, No. 9, 588-590, Sep. 2005.
6. Tang, C. W. and M. G. Chen, "Synthesizing microstrip branch line couplers with predetermined compact size and bandwidth," IEEE Transactions on Microwave Theory and Techniques, Vol. 55, No. 9, 1926-1934, 2007.
7. 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 Transactions on Microwave Theory and Techniques, Vol. 56, No. 12, 2950-2953, 2008.
8. Tseng, C. H. and C. L. Chang, "A rigorous design methodology for compact planar branchline and rat-race couplers with asymmetrical T structures," IEEE Transactions on Microwave Theory and Techniques, Vol. 60, 2085-2092, Jul. 2012.
9. Elhiwaris, M. Y. O., S. K. A. Rahim, U. A. K. Okonkwo, and N. M. Jizat, "Miniaturize size branch line coupler using open stubs with high low impedances," Progress In Electromagnetic Research Letters, Vol. 23, 65-74, Apr. 2011.
10. Sun, L., Y. Z. Yin, X. Lei, and V. Wong, "A novel miniaturized branch line coupler with equivalent transmission Lines," Progress In Electromagnetics Research Letters, Vol. 38, 35-44, 2013.
11. Al-Khateeb, L., "Miniaturized hybrid branch line couplers based on a square split resonator loading technique," Progress In Electromagnetics Research Letters, Vol. 40, 153-162, 2013.
12. , , Users Manual, CST Microwave studio 2010.