A slot antenna includes a substrate having a first side and a second side, a first conductive layer on the first side of the substrate, and a second conductive layer on the second side of the substrate. A first aperture is in the first conductive layer, a second aperture is in the first conductive layer, a first slotline is in the first conductive layer and in communication with the first aperture, and a second slotline is in the first conductive layer and in communication with the second aperture. A third aperture can be in the second conductive layer. A plurality of vias can be in the substrate and surrounding at least a portion of a region including the first aperture, the second aperture, the first slotline, and the second slotline, each of the vias extending through the substrate from the first conductive layer to the second conductive layer.