ANTENNA DEVICE

In a conventional antenna device, transmission radio waves transmitted from a transmitting antenna traveling directly to a receiving antenna are blocked by a shield wall disposed between the receiving antenna and the transmitting antenna. However, some of the transmission radio waves are diffracted at the edge of the shield wall and enter the receiving antenna as diffracted waves, affecting the reception of the reception radio waves. In view of this, the shield wall and a polarized wave converter unit are disposed between the transmitting antenna unit and the receiving antenna unit. As a result, vertically polarized wave components of the diffracted waves are converted by the polarized wave converter unit to circularly polarized wave components that are less affecting the reception of the reception radio waves in the receiving antenna, and the diffracted waves are prevented from affecting the receiving operation of the receiving antenna.