1. Field of the Invention
The present invention relates to a radar system which calculates an error of an azimuth angle of a radar device that uses reflection of propagation waves such as radio waves, sound waves, or light waves, to correct the azimuth angle.
2. Description of the Related Art
In recent years, development have been made on a radar device which is mounted on a movable body such as a vehicle, and has such a structure that a reflecting point of an obstacle or the like running in a traveling direction is detected to implement functions of speed control and collision prevention. In such the radar device, for the purpose of the speed control and collision prevention, it is required to obtain an azimuth angle, in addition to a distance with respect to the reflecting point and a relative speed between the own vehicle and the obstacle (or between reflecting points ?), to select an object traveling in the same traffic lane as the own vehicle. Various radar systems have been proposed to obtain the azimuth angle.
In the conventional radar device, the reflected waves are received by two or more antennas, and determination of the angles of the reflected waves are performed by using the receiving intensity of the reflected waves and transmission angles of the respective antennas (for example, refer to JP 09-43344 A).
In another conventional radar device, narrow beams are scanned in a horizontal direction to determine an angle of a reflecting point based on the receiving intensity of the reflected wave between two beams and the transmission angles of the respective beams (for example, refer to JP 2001-201566 A). To obtain the transmission angles of the respective scanning beams, an angle sensor may be used, for example.
In still another conventional radar device, an amount of axis deviation with respect to the traveling direction of the movable body on which a radar is mounted, is estimated and corrected to thereby correct the angle error caused by the axis deviation (for example, refer to JP 2002-228749 A).
In such the radar systems described above, the mechanical and electrical precision of the devices causes an azimuth angle error. In the conventional radar device, differences in the electric properties of the respective antennas cause a receiving intensity error, and as a result, an error occurs in the determination result of the azimuth angle of the reflecting point. In the another conventional radar device, since the error of the angle sensor causes an error in the transmission angle of the respective beams, an error occurs in the determination result of the azimuth angle of the reflecting point. In the still another conventional radar device, the amount of axis deviation with respect to the traveling direction of the movable body, which mounts the radar thereon, is estimated. However, since the azimuth angle error is not considered, the error may be caused in the amount of axis deviation when there is the azimuth angle error.
Manufacturing variations may be adjusted at the time of the manufacturing, but the adjustment may lead to an increase in cost, and deterioration with time may cause a mechanical or electrical error. Further, there is a problem of an increase in cost to minimize the error caused by the deterioration with time.