Beamforming broadside antenna array for 60-GHz technology

In this paper, a 60-GHz switch-beam broadside antenna array fed by a Butler matrix is introduced. In order to achieve high gain and a wide covering range by switching the main beam at broadside directions, four patch antennas are placed to form a 2×2 planar array. By applying four sets of phase differences to each element, the main beam of the planar array will switch to four directions respectively at broadside and overall form a wider beamwidth. Note that a Butler matrix, which is typical designed for one-dimensional (1-D) beam-switching, can be applied in the broadside array after properly arranging the element spacing and feed order. Using MATLAB, the covering percentage (CP) in the designated broadside region can be easily quantified and then optimized. From the results, this broadside array can nearly provide over 8-dBi gain in the region of θ from 0° to 30°, where θ is from the conventional spherical coordinates (r, θ, ϕ). The proposed array is designed on a 4-layered PCB which is easily integrated in packaging.