1. Ho, M.-J., G. L. Stuber, and M. Austin, "Performance of switched-beam smart antennas, for cellular radio systems," IEEE Trans. Veh. Technol., Vol. 47, No. 1, 10-19, Feb. 1998.
doi:10.1109/25.661027 Google Scholar
2. Butler, J. and R. Lowe, "Beamforming matrix simplifies design of electronically scanned antennas," Electronic Design, Vol. 9, 170-173, 1961. Google Scholar
3. Jackson, R. W., "Considerations in the use of coplanar waveguide for millimeter wave integrated circuits," IEEE Trans. Microwave Theory Tech., Vol. 34, 1450-1456, 1986.
doi:10.1109/TMTT.1986.1133562 Google Scholar
4. Ghione, G. and C. Naldi, "Parameters of coplanar waveguides with lower ground plane," Electron. Lett., Vol. 19, 734-735, 1983.
doi:10.1049/el:19830500 Google Scholar
5. Corona, A. and M. J. Lancaster, "A high-temperature supercon-ducting butler matrix," IEEE Trans. on Applied Superconductivity, Vol. 13, No. 4, Dec. 2003.
doi:10.1109/TASC.2003.820507 Google Scholar
5. He, J., B.-Z. Wang, Q.-Q. He, Y.-X. Xing, and Z.-L. Yin, "Wideband X-band microstrip Butler matrix," Progress In Electromagnetics Research, Vol. 74, 131-140, 2007.
doi:10.2528/PIER07042302 Google Scholar
7. Traii, , M., M. Nedil., A. Gharsallah, and T. A. Denidni, "A novel wideband Butler matrix using multi-layer technolog," Microwave and Optical Technol. Lett., Vol. 51, No. 3, 659-663, 2009.
doi:10.1002/mop.24116 Google Scholar
8. Nedil, M., A. M. Habib, and T. A. Denidni, "Novel ultra-wideband CB-CBW Butler matri," IEEE Antennas and Propagation Society International Symposium, 1-4, 2008.
doi:10.1109/APS.2008.4619181 Google Scholar
9. Traii, M., M. Nedil, A. Gharsallah, and T. A. Denidni, "A new design of compact 4 x 4 Butler matrix for ISM applications," International Journal of Microwave Science and Technology, Vol. 2008, 2008.
doi:10.1155/2008/784526 Google Scholar
10. Denidni, T.-A. and M. Nedil, "Experimental investigation of a new butler matrix using slotline technology for beamforming antenna arrays," Institution of Engineering and Technology (IET) Microwaves, Antennas & Propagation, Vol. 2, No. 7, 641-649, Oct. 2008.
doi:10.1049/iet-map:20060199 Google Scholar
11. Nedil, M., T. A. Denidni, and L. Talbi, "Novel Butler matrix using CPW multilayer technology," IEEE Trans. Microwave Theory Tech., Vol. 54, 499-507, 2006.
doi:10.1109/TMTT.2005.860490 Google Scholar
12. Dall‘Omo, C., T. Monediere, B. Jeko, F. Lamour, I. Wolk,M. Elkael, "Design and realisation of a 4 x 4 microstrip butler matrix without any crossing in millimeter-wave," Microwave and Optical Tech. Lett., Vol. 38, No. 6, Sep. 2003. Google Scholar
13. Bona, M., L. Manholm, J. P. Satarski, and B. Svensson, "Low-loss compact butler matrix for a microstrip antenna," IEEE Trans. on Microwave Theory and Tech., Vol. 50, No. 9, Sep. 2002.
doi:10.1109/TMTT.2002.802318 Google Scholar
14. Djera, T. and K. Wu, "Multilayered substrate integrated waveguide 4x 4 Butler matrix," International Journal of RF and Microwave Computer-aided Engineering, Vol. 22, No. 3, 336-344, May 2012.
doi:10.1002/mmce.20602 Google Scholar
15. Chan, K.-L., F. A. Alhargan, and S. R. Judah, "A quadrature hybrid design using a four-port elliptic patch," IEEE Trans. Microwave Theory Tech., Vol. 45, 307-310, 1997.
doi:10.1109/22.557619 Google Scholar
16., HFSS 12.1 ANSYS, Inc. Canonsburg, Pennsylvania, USA. Google Scholar
17. Tefiku, F., E. Yamashita, J. Funada, "Novel directional couplers using broadside-coupled coplanar waveguides for double-sided printed antennas," IEEE Trans. Microwave Theory Tech., Vol. 44, 275-281, Feb. 1996.
doi:10.1109/22.481577 Google Scholar
18. Chang, C.-P., J.-C. Chiu., H.-Y. Chiu., and Y.-H. Wang, "A 3-dB Quadrature coupler using broadside-coupled coplanar waveguides," IEEE Microwave and Wireless Components Lett., Vol. 18, No. 3, Mar. 2008. Google Scholar
19. Johnosono, S., T. Fujii, and I. Ohta, "Design of broadband CPW branch-line 3 dB couplers," Proceedings of the 36th European Microwave Conf., 36-39, 2006. Google Scholar
20. Wong, Y. S., S. Y. Zheng, and W. S. Chan, "Multifolded bandwidth branch line coupler with ltering characteristic using coupled port feeding," Progress In Electromagnetics Research, Vol. 118, 17-35, 2011.
doi:10.2528/PIER11041401 Google Scholar
21. Li, B., X. Wu, and W. Wu, "A miniaturized branch-line coupler with wideband harmonics suppression," Progress In Electromagnetics Research, Vol. 17, 181-189, 2010. Google Scholar
3. Riaziat, M., R. Majidi-Ahy, and I. J. Feng, "Propagation modes and dispersion characteristics of coplanar waveguides," IEEE Trans. Microwave Theory Tech., Vol. 38, 245-251, 1990.
doi:10.1109/22.45333 Google Scholar
23. Haydl, W. H., "Resonance phenomena and power loss in conductor-backed coplanar structures," IEEE Microwave Guided Wave Lett., Vol. 20, 514-516, 2000.
doi:10.1109/75.895086 Google Scholar
24. Haydl, W. H., "On the use of vias in conductor-backed coplanar circuits," IEEE Trans. Microwave Theory Tech., Vol. 50, 1571-1577, 2002.
doi:10.1109/TMTT.2002.1006419 Google Scholar