"JOURNAL OF RADIO ELECTRONICS" (Zhurnal Radioelektroniki ISSN 1684-1719, N 10, 2017

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The Method of reducing the size of a microstrip branch-line coupler


D. A. Letavin

Federal State Autonomous Educational Institution of Higher Professional Education «Ural Federal University named after the first President of Russia B.N.Yeltsin», Mira 32, Yekaterinburg 620002, Russia


The paper is received on July 27, 2017


Abstract. At present passive microstrip devices have found wide application in the modern radio engineering. Directional couplers can be used in communication, antennas, radio measurements. Also they can be implemented in the power splitters, modulators, adders, shifters. Standard design branch-line coupler consists of four quarter-wave sections of transmission line. It should be noted that the dimensions of the device depend on the frequency. The higher it is, the greater the area of the device. Therefore it is necessary to use different approaches to reduce the size of such devices, maintaining their original characteristics in a wide band of frequencies. In order to eliminate the spurious bandwidth, to reduce the size and efficiency of production, structures which function as quarter-wave segments are used. Such structures are much shorter in length, and they can be made by standard techniques: the etching of printed circuit boards. Microstrip capacitances, which are the part of the proposed structures, are placed inside the free space of the device. To account for the influence of adjacent conductive lines to each other and other factors we use the AWR DE 13. The compact design has an area of 554 mm2, which is 78% less than conventional construction. The simulation results were made as prototype of a compact clutch. Measurement of parameters was carried out using a vector network analyzer Rohde & Schwarz ZVA 24 and calibration kit K52. As a result we obtained compact design, easy to manufacture, which may find various applications in microwave technology. Further reduction of the area of the coupler is possible by optimizing the structures and their location. However, the  increasing of the degree of miniaturization leads to the decrease in bandwidth.

Key words: microstrip line, miniaturization, branch-line coupler.


1.     Kimberley W. Eccleston, and Sebastian H.M. Ong, “Compact Planar Microstripline Branch-Line and Rat-Race Couplers,” IEEE Trans. Microw. Theory Tech., 2003, Vol. 51, No. 10, pp. 2119-2125.

2.     Kai-Yu Tsai, Hao-Shun Yang, Jau-Horng Chen, and Yi-Jan Emery Chen, “A miniaturized 2 dB Branch-Line Hybrid Coupler With Harmonics Suppression,” IEEE Microw. Wireless Compon.Lett., 2011, Vol. 21, No. 10, pp. 537-539.

3.     C. W. Tang and M.-G.Chen, "Synthesizing microstrip branch-line coupler with predetermined compact size and bandwidth," IEEE Trans. Microw. Theory Tech., 2007, Vol. 55, No. 9, pp. 1926-1934.

4.     Chao-Wei Wang, Tzyh-Ghuang Ma and Chang-Fa Yang, “A new planar artificial transmission line and its applications to a miniaturized butler matrix,” IEEE Trans. Microw. Theory Tech., 2007, Vol. 55, No. 12, pp. 2792-2801.

5.     Kimberley W. Eccleston and Sebastian H. M., “Compact planar microstripline branch-line and rat-race couplers,” IEEE Trans. Microw. Theory Tech., 2003, Vol. 51, No. 10, pp. 2119-2125.

6.     S.-S. Liao and J.-T. Peng, "Compact planar microstrip branch-line couplers using the quasi-lumped elements approach with nonsymmetrical and symmetrical T-shaped structure," IEEE Trans. Microw. TheoryTech., 2006, Vol. 54, No. 9, pp. 3508-3514.

7.     N. N. Shchetinin, V. A. Melnik, "Compact microstrip 3 dB quadrature directional coupler". Vestnik Voronezhskogo Instituta FSIN ROSSII - Proceedings of Voronezh institute of FSIN RF. 2014, No. 4, pp. 26-28. (in Russian).

8.     N. N. Shchetinin, A. V. Ostankov, E. I. Vorobjeva, "Mathematical model for the microstrip directional coupler on a quasi-lumped element," Vestnik Voronrzhskogo Gosudarstvennogo Tekhnicheskogo Universiteta. - Proceedings of  Voronezh State Technical University. 2014, Vol. 10, No. 3-1, pp. 66-70 (in Russian).

9.     Chao-Hsiung Tseng and Chih-Lin Chang, “A rigorous design methodology for compact planar branch-line and rat-race couplers with asymmetrical T-structure,” IEEE Trans. Microw. Theory Tech., 2012, Vol. 60, No. 7, pp. 2085-2092.

10.  K. W. Eccleston and S. H. M. Ong, "Compact planar microstripline branch-line and rat-race coupler," IEEE Trans. Microw. Theory Tech., 2003, Vol. 51, No. 10, pp. 2119-2125.

11.  Wei-Shin Chang and Chi-Yang Chang, “A high slow-wave factor microstrip structure with simple design formulas and its application to microwave circuit design,” IEEE Trans. Microw. Theory Tech., 2002, Vol. 60, No. 11, pp. 3376-3383.

12.   Hani Ghali and Tarek A. Moselhy “Miniaturized fractal rat-race, branch-line, and coupled-line hybrids,” IEEE Trans. Microw. Theory Tech., 2004, Vol. 52, No. 11, pp. 2513-2520.


For citation:

D. A. Letavin. The method of reducing the size of a microstrip branch-line coupler. Zhurnal Radioelektroniki - Journal of Radio Electronics, 2017, No. 10. Available at http://jre.cplire.ru/jre/oct17/1/text.pdf. (In Russian)