As such, in the disclosure, a slit is formed in a side plate. The slit has an opening in the upper end surface of the side plate. The opening has a width which is smaller than a thickness of the side plate and enables to correspond to a thickness t of the substrate and a length which enables to correspond to a length a of one side of the substrate. An RF antenna module is housed in the slit formed in the side plate of the housing to be accommodated in the housing by inserting the one side of the substrate through the opening of the slit, which is formed in the upper end surface of the side plate, and inserting the substrate into the slit by an amount equal to or larger than a length of another side of the substrate.