Method and apparatus for calibrating azimuth boresight in a radar system
First Claim
1. A method of calibrating a boresight of a radar antenna in a radar system, comprising the steps of:
- a) selecting a calibration target for use in calibrating the antenna boresight;
b) obtaining an initial measurement of the target range and azimuth angle at a first time instance;
c) obtaining a subsequent measurement of the target range and azimuth angle at a second time instance;
d) calculating a boresight offset angle α
using the initial and subsequent target range and azimuth angle measurements; and
e) calibrating the antenna boresight to compensate for the boresight offset angle calculated in step (d).
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Accused Products
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.
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Citations
39 Claims
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1. A method of calibrating a boresight of a radar antenna in a radar system, comprising the steps of:
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a) selecting a calibration target for use in calibrating the antenna boresight; b) obtaining an initial measurement of the target range and azimuth angle at a first time instance; c) obtaining a subsequent measurement of the target range and azimuth angle at a second time instance; d) calculating a boresight offset angle α
using the initial and subsequent target range and azimuth angle measurements; ande) calibrating the antenna boresight to compensate for the boresight offset angle calculated in step (d). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of calibrating a boresight of a radar antenna in a radar system, comprising the steps of:
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a) selecting a calibration target for use in calibrating the antenna boresight; b) obtaining an initial measurement of the selected calibration target'"'"'s range and azimuth angle at a first time instance; c) obtaining subsequent measurements of the selected calibration target'"'"'s range and azimuth angle at successive time instances subsequent to the first time instance; d) calculating a boresight offset angle α
using the initial and subsequent target range and azimuth angle measurements; ande) calibrating the antenna boresight to compensate for the boresight offset angle calculated in step (d). - View Dependent Claims (10, 11)
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12. A method of calibrating a boresight of a radar antenna in a vehicular radar system, wherein the radar system is deployed on a host vehicle, and wherein the host vehicle travels upon a road and has a known heading, comprising the steps of:
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a) selecting a qualified calibration target vehicle that is substantially aligned with the host vehicle'"'"'s heading for use in calibrating the antenna boresight; b) obtaining an initial measurement of the calibration target azimuth angle at a first time instance; c) obtaining a subsequent measurement of the calibration target azimuth angle at a second time instance; d) estimating a boresight offset angle α
based upon the initial and subsequent calibration target azimuth angle measurements; ande) calibrating the antenna boresight to compensate for the boresight offset angle calculated in step (d). - View Dependent Claims (13)
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14. A method of calibrating a boresight of a radar antenna in a vehicular radar system, wherein the radar system is deployed on a host vehicle, and wherein the host vehicle travels upon a road and has a known heading, comprising the steps of:
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a) selecting a qualified calibration target vehicle that is substantially aligned with the host vehicle'"'"'s heading for use in calibrating the antenna boresight; b) obtaining an initial measurement of the calibration target azimuth angle at a first time instance; c) obtaining subsequent measurements of the calibration target azimuth angle at successive time instances subsequent to the first time instance; d) estimating a boresight offset angle α
based upon the initial and subsequent calibration target azimuth angle measurements; ande) calibrating the antenna boresight to compensate for the boresight offset angle estimated in step (d). - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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30. An apparatus for calibrating an antenna boresight in a radar system, comprising:
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a) means for selecting a calibration target for use in calibrating the antenna boresight; b) means, responsive to the selecting means, for obtaining an initial measurement of the target range and azimuth angle at a first time instance; c) means, responsive to the selecting means, for obtaining subsequent measurements of the target range and azimuth angle at successive time instances subsequent to the first time instance; d) means, responsive to the obtaining means, for calculating a boresight offset angle α
using the initial and subsequent target range and azimuth angle measurements; ande) means, for calibrating the antenna boresight to compensate for the calculated boresight offset angle. - View Dependent Claims (31, 32)
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33. An apparatus for calibrating a boresight of a radar antenna for use in a vehicular radar system, wherein the radar system is deployed on a host vehicle, and wherein the host vehicle travels upon a road and has a known heading, comprising:
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a) means for selecting a qualified calibration target that is substantially aligned with the host vehicle'"'"'s heading for use in calibrating the antenna boresight; b) means, responsive to the selecting means, for obtaining an initial measurement of the calibration target azimuth angle at a first time instance; c) means, responsive to the selecting means, for obtaining subsequent measurements of the calibration target azimuth angle at successive time instances subsequent to the first time instance; d) means, responsive to the obtaining means, for estimating a boresight offset angle α
based upon the initial and subsequent calibration target azimuth angle measurements; ande) means, for calibrating the antenna boresight to compensate for the estimated boresight offset angle. - View Dependent Claims (34, 35)
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36. A computer program executable on a general purpose computing device, wherein the program is capable of calibrating a boresight of a radar antenna in a radar system, comprising:
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a) a first set of instructions for selecting a calibration target for use in calibrating the antenna boresight; b) a second set of instructions for obtaining an initial measurement of the calibration target'"'"'s range and azimuth angle at a first time instance; c) a third set of instructions for obtaining subsequent measurements of the calibration target'"'"'s range and azimuth angle at successive time instances subsequent to the first time instance; d) a fourth set of instructions for calculating a boresight offset angle α
using the initial and subsequent target range and azimuth angle measurements; ande) a fifth set of instructions for calibrating the antenna boresight to compensate for the calculated boresight offset angle. - View Dependent Claims (37, 38)
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39. A method of calibrating a boresight of a radar antenna in a vehicular radar system, wherein the radar system is deployed on a host vehicle, and wherein the radar system is capable of obtaining target azimuth angle measurements from targets detected by the radar antenna, and wherein the radar system maintains an azimuth angle 5 histogram, the histogram having a plurality of bins associated and corresponding to a set of discrete target azimuth angles, comprising the steps of:
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a) initializing an azimuth histogram such that each azimuth angle bin is set to zero, except that a bin associated with a zero degree target azimuth angle is set to a pre-determined maximum histogram count; b) receiving target data and obtaining a target azimuth angle measurement; c) qualifying the azimuth angle measurement obtained at step (b); d) if the azimuth angle measurement qualifies, adding a count to the target azimuth angle bin corresponding to the qualified azimuth angle measurement; e) determining whether the histogram contains a pre-determined maximum number of counts; f) returning to step (b) if the histogram does not contain the maximum number of counts, otherwise, determining the antenna boresight offset angle from the azimuth angle bin having the highest number of counts; and g) calibrating the antenna boresight using the boresight offset angle determined in step (f).
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Specification