Implementation of a Miniaturized Planar 4-Port Microstrip Butler Matrix for Broadband Applications

Document Type : Research Paper


1 Department of Electrical Engineering, Urmia University

2 Department of Electrical Engineering, Miandoab Branch, Islamic Azad University, Miandoab, Iran

3 Department of Electrical and Computer Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran


In this paper, a miniaturized and broadband 4 × 4 Butler matrix is presented. All components of the presented matrix are designed in a way that, have the broadband impedance bandwidth and compact electrical size as much as possible. Traditional previous Butler matrix composed of phase shifters, while in the presented feeding network dummy crossover role this act, which results to enhance the phase difference bandwidth. The compactness of the optimized and proposed coupler is related to inserting the S-shaped arms instead of ordinary parts. The modified dummy crossover is used to overcome the mismatch phase difference among phase shifter and crossover. Design procedure of miniaturized broadband components such as 3-branch-line coupler, crossover, phase shifter and final design are presented step by step. The results of the simulation and measurement of the desired Butler matrix makes it suitable for the applications of planar multi-beam antennas. The extracted results determine that the bandwidth of the presented network is from 4.5 ~ 6 GHz, that is a good candidate for WLAN applications. The whole size of network is 71.5 × 38.3 mm2.


1- Chen, H. Wu, and W. Wu, “Design and implementation of a compact planar 4 × 4 microstrip Butler matrix for wideband application,” Progress in Electromagnetics Research C, vol. 24, pp. 43-55, 2011.
2- Zheng, W. Chan, S. Leung, and Q. Xue, “Broadband Butler matrix with at coupling,” Electronics Letters, vol. 43, no. 10, pp. 576-577, May 2007.
3- A. Babale, S. K. Abdul Rahim, O. A. Barro, M. Himdi, and M. Khalily, “Single layered 4 × 4 Butler matrix without phase-shifters and crossovers,” IEEE Access, vol. 6, pp. 77289-77298, 2018.
4- Djerafi, N. J. G. Fonseca, and K. Wu, “Design and implementation of a planar 4 × 4 Butler matrix in SIW technology for wide band high power applications,” Progress In Electromagnetics Research B, vol. 35, pp. 29-51, 2011.
5- Lian, Y. Ban, C. Xiao, and Z. Yu, “Compact substrate-integrated 4 × 8 Butler matrix with sidelobe suppression for millimeter-wave multibeam application,” IEEE Antennas and Wireless Propagation Letters, vol. 17, no. 5, pp. 928-932, May 2018.
6- Bartlett and J. Bornemann, “Cross-configuration substrate integrated waveguide beam-forming network for 1D and 2D beam patterns,” IEEE Access, vol. 7, pp. 151827-151835, 2019.
7- Lee, M. K. Khattak, and S. Kahng, “Wideband 5G beamforming printed array clutched by LTE-A 4 × 4-multiple-inputmultiple-output antennas with high isolation,” IET Microwaves, Antennas Propagation, vol. 12, no. 8, pp. 1407-1413, June 2018.
8- Trinh-Van, J.M. Lee, Y. Yang, and K. C.  Hwang, “A Sidelobe-Reduced, Four-Beam Array Antenna Fed by a Modified 4x4 Butler Matrix for 5G Applications,” IEEE Trans. Antenna Propag., vol. 67, no. 7, pp. 4528-4536, July 2019.
9- Ding and A. Kishk, “Wideband Hybrid Coupler with Electrically Switchable Phase-Difference Performance,” IEEE Microwave and Wireless Components Letters, vol. 27, no. 11, pp. 992-994, Nov. 2017.
10- K. Barik, K. V. Phani Kumar, and S. S. Karthikeyan, “A Compact Wideband Harmonic Suppressed 10 dB Branch Line Coupler Using Cascaded Symmetric PI Sections”. Microwave and Optical Technology Letters, vol. 58, no. 7, pp. 1610-1613, April 2016.
11- P. Chen, Z. Qamar, S. Y. Zheng, Y. Long, and D. Ho, “Design of a compact wideband Butler matrix using vertically installed planar structure,” IEEE Transactions on Components, Packaging and Manufacturing Technology, vol. 8, pp. 1420–1430, Aug 2018.
12- Kim, J. Lee, and J. Choi, “Analysis and Design of Miniaturized Multisection Crossover with Open Stubs”. Microwave and Optical Technology Letters, vol. 57, no. 11, pp. 2673-2677, Aug. 2015.
13- Maleki, J. Nourinia, Y. Zehforooh, and V. Rafii, “A compact planar 90° branch line coupler using s-shaped structure loading for wideband application,” Applied Computational Electromagnetics Society Journal”, vol. 28, no. 7, pp. 597–601, July 2013.
14- F. Moulder, W. Khalil, and J. L. Volakis, “60-GHz two-dimensionally scanning array employing wideband planar switched beam network,” IEEE Antennas and Wireless Propagation Letters, vol. 9, pp. 818-821, Aug. 2010.