Apparatus includes a device housing, a device face, a printed circuit board (PCB), and an antenna array. The device housing has a shape characterized by an axis, a planar housing surface that is perpendicular to the axis, and a housing sidewall that is parallel to the axis. The housing sidewall is positioned along a periphery of a planar housing surface. The device face is positioned at an opposite end of the device housing from the planar housing surface. The PCB is positioned between and parallel to the planar housing surface and the device face. The antenna array has multiple antenna elements at least some of which are electrically coupled to the PCB. The antenna array is configured to concentrate radiation of radio waves laterally through a radiation plane that is parallel to the sidewall of the housing and that is perpendicular to the device face and the planar housing surface.