Patent ID: 8035561

Claim:
A communication apparatus mounted on a vehicle and communicating with other apparatuses remote from the communication apparatus, comprising: a switch for switching between a vertical polarized antenna and a horizontal polarized antenna, wherein the vertical polarized antenna transmits and receives an electric wave, which has a polarization surface perpendicular to a ground surface, and the horizontal polarized antenna transmits and receives the electric wave, which has another polarization surface in parallel to the ground surface; a communication device for transmitting and receiving the electric wave via one of the vertical polarized antenna and the horizontal polarized antenna, which is selected by the switch; a monitor for monitoring a relative distance between the communication apparatus and the other apparatuses; and a controller for controlling the switch in such a manner that the switch selects the vertical polarized antenna when the relative distance is equal to or larger than a distance threshold, and the switch selects the horizontal polarized antenna when the relative distance is smaller than the distance threshold, wherein the distance threshold is larger than a distance between the communication apparatus and a dip point.