Pattern-Reconfigurable Unidirectional Dipole Antenna Array Fed by SIW Coupler for Millimeter Wave Application

A directional two-element mm-wave dipole antenna array with reconfigurable patterns is presented in this paper. An substrate integrated waveguide (SIW) 90 degrees 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 lambda(0)/4 (4 is the wavelength of the free space) between them. When the two inputs of the 90 degrees 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 S-11 and S-22 are below -10 dB from 45.5 to 49.5 GHz, and the measured gain is all great than 5 dBi within this band.