Design and Simulation of X-Band Microstrip Butler Matrix for Feeding the Narrow Beam-Width Phase Array Antenna

Flight systems, have extensive applications in various scientific, industrial, and commercial fields. One component utilized in flight systems' structure is radar. In various applications of these systems, it is required to track specific targets and directions in a narrow angular region. This feature is achievable by utilizing the narrow beam-width antennas. Array antennas, besides providing the demanded gain, can fulfill such requirement. Also, the beam-width should be tunable in an acceptable range of different directions. Such a tunability can be realized using the phased array antennas. The capability of change in main lobe direction of these antennas is provided using the active phase shifting components as feeders of the phased arrays, such as PIN diodes and ferrite devices. However, using the passive Butler matrix components is considered as simpler and cheaper tool to realize the approach. Utilizing the Butler matrix with more input-output ports, leads to narrower beam-width radiation pattern. In this paper, a simple design of 32×32 Butler matrix for X-band frequency spectra is proposed, and the simulation results of its performance are presented. The simulations are carried out via Comsol software which is based on finite element method. Finally, after applying the appropriate waves to two specific input ports and connecting the Butler matrix structure to the microstrip array, the beam-width of 3.5 degrees is achieved. The achievement to narrow beam width radiation realized by a microstrip antenna array fed with a 32×32 Butler matrix and only based on a single layer board, is the main purpose of the research.