Patent ID: 7639183

Claim:
A radar device comprising: a transmitting unit which is configured to radiate a radar pulse into a space via a transmitting antenna; a receiving unit which is configured to receive via a receiving antenna a reflected wave of the radar pulse returned from the space; an analysis processing unit which explores an object existing in the space based on a reception output from the receiving unit; and a control unit which controls at least one of the transmitting unit and the receiving unit based on an output from the analysis processing unit, wherein each of the receiving antenna and the transmitting antenna comprises: a dielectric substrate; a ground conductor which is piled up at one surface side of the dielectric substrate; circularly polarized antenna elements formed onto an opposite side of the dielectric substrate; a plurality of metal posts which are arranged at predetermined intervals into a lattice structure to have cavities, the metal posts surrounding the antenna elements which are arranged in the cavities, respectively, wherein each of the metal posts has one and opposite ends, and penetrates the dielectric substrate along a thickness direction thereof, the one ends of the metal posts being connected to the ground conductor, and the opposite ends of the metal posts being arranged around the antenna elements on the opposite surface of the dielectric substrate; and a conducting rim which is extended along an arrangement of the opposite ends of the metal posts to define the cavities, and which is connected to the opposite ends of the metal posts to short-circuit the metal posts; wherein the circularly polarized antenna elements for the receiving antenna are electrically isolated from the circularly polarized antenna elements for the transmitting antenna, and wherein the circularly polarized antenna elements for the receiving antenna have a first polarization rotation direction, and the circularly polarized antenna elements for the transmitting antenna have a second polarization rotation direction opposite to the first polarization rotation direction.