Method and apparatus for calibrating azimuth boresight in a radar system

Abstract

A method and apparatus for calibrating azimuth boresight in a radar system. Antenna boresight misalignment can cause radar systems to inaccurately determine the position of targets relative to a platform vehicle. These errors can be corrected by detecting and accurately measuring a boresight offset angle defined as the angle between the radar antenna boresight and the direction of travel of the host platform vehicle. Several antenna boresight calibration techniques are described. A first technique calculates the boresight offset angle by obtaining target range and azimuth angle measurements at two instants in time. The boresight offset angle is determined by the geometric relationship of the offset angle, target range and azimuth values obtained at two successive time instants. A refined approach obtains target range and azimuth values at several successive time instants, calculating interim boresight offset angles at each time instant. The boresight offset angle is computed by averaging the interim boresight offset angles. In second and third calibration techniques, the boresight offset angle is estimated from the azimuth of qualified calibration targets that are substantially aligned with the host vehicle's heading. Several restrictions are imposed upon the potential calibration targets to suppress the erroneous qualification of adjacent vehicle traffic. In accordance with one embodiment of the present invention, the calibration techniques are implemented by software instructions executed by a microprocessor within the radar system. Once the boresight offset angle is detected and calculated, it can be used to calibrate the antenna boresight using either a mathematical or physical calibration approach.