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A directional two-element mm-wave dipole antenna array with reconfigurable patterns is presented in this paper. An substrate integrated waveguide (SIW) 90° coupler is used to realize reconfigurable patterns of the antenna array. The two dipole elements are parallel in space, and there is a distance of λ₀/4 (λ₀ is the wavelength of the free space) between them. When the two inputs of the 90° coupler are excited, respectively, two completely opposite radiation patterns are able to be achieved. In order to further enhance the directivity of the proposed antenna, two groups of novel zero-index metamaterials and three metallic strips are introduced. As a consequence, a 0.7-1.2 dBi gain enhancement and reduced back lobe are obtained within the working frequencies. The measured amplitudes of S₁₁ and S₂₂ are below -10 dB from 45.5 to 49.5 GHz, and the measured gain is all great than 5 dBi within this band.