TRANSITION DEVICE

A transition device includes a first metal layer, a signaling metal line, an excitation metal piece, a first dielectric layer, a plurality of conductive via elements, a reflector, and a waveguide. The first metal layer has a notch. The notch extends to the interior of the first metal layer, forming a first slot region. The signaling metal line is disposed in the notch. The excitation metal piece is disposed in the first slot region and is coupled to the signaling metal line. The first dielectric layer has a pair of first openings. The first dielectric layer includes a bridging portion disposed between the first openings. The bridging portion is configured to carry the excitation metal piece. The conductive via elements penetrate the first dielectric layer and are coupled to the first metal layer. The conductive via elements at least partially surround the first slot region.