The present invention includes a first connector unit, a second connector unit, and a joining unit. The first connector unit is provided at an end section of a feeder cable formed on a circuit substrate. The second connector unit is provided at an end section of a waveguide cable through which a high-frequency signal is transmitted. The joining unit includes a hollow waveguide interposed between the first connector unit and the second connector unit, the joining unit being capable of detachably joining the first connector unit and the second connector unit.