In phased array system for producing multi-beams, equal power with different phase has to be fed to the antenna system. The necessary phase difference is provided by a digital circulatory or by a transmission line modified as butler matrix. In this paper a 4 x 4 butler matrix using microstrip line is realized for adequate phase difference. Butler matrix consist of a 3 dB coupler, crossovers and phase shifter. 3 dB coupler ensures equal power is fed to the antenna system while crossover maintains signal purity whenever transmission lines overlap. Phase shifter provides necessary phase shift need for beam formation in desired direction. Each of these devices is analyzed separately using ANSYS HFSS and optimized design is fabricated and tested. The optimized designs of individual components is combined together to realize the butler matrix.
Jayakrishnan, V. M., & Menon, S. K. (2016). Realization of Butlermatrix for Beamforming in Phased Array System. In Procedia Computer Science (Vol. 93, pp. 223–229). Elsevier B.V. https://doi.org/10.1016/j.procs.2016.07.204