A communication device including circuitry configured to receive a signal transmitted to the communication device via a communication channel. Fluidizing gas is delivered to a plenum below the riser. For example, the planar shape of the power semiconductor element is formed into a rectangle, and a gap having a sectorial planar shape is formed between the power semiconductor elements adjacent to each other. The inner surface of the contact part of the supporting member also has a convex shape in a longitudinal plane orientated radially with respect to the central axis of the corresponding cell before irradiation. The plug portion has a cylindrical hole, into which a transmission sleeve is inserted.