# US 2023/0056655 A1 · Radar System Calibration with Bistatic Sidelobe Compensation

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- Number: US 2023/0056655 A1
- Document ID: US20230056655A1
- Status: Published application
- Kind: A1
- Application number: 17/407,071
- Filed: 2021-08-19
- Published: 2023-02-23
- Earliest claimed: 2021-08-19
- Assignees: Aptiv Technologies AG
- Applicants: Aptiv Technologies Limited
- Inventors: Armin Talai; Rafal Michal Burza; Sashi Praveen Kalli
- Web page: https://patentgrep.com/patent/US20230056655A1

## CPC

- G01S 7/40: Means for monitoring or calibrating
- G01S 13/931: of land vehicles
- B60W 50/00: Details of control systems for road vehicle drive control not related to the control of a particular sub-unit {, e.g. process diagnostic or vehicle driver interfaces}
- G01S 7/403: {in azimuth, i.e. in the horizontal plane}
- G01S 7/4034: {in elevation, i.e. in the vertical plane}
- G01S 7/4086: {in a calibrating environment, e.g. anechoic chamber}
- B60W 2050/0063: {Manual parameter input, manual setting means, manual initialising or calibrating means}
- G01S 2013/93271: {in the front of the vehicles}
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- B60W: CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT

## Abstract

This document describes techniques for enabling radar system calibration with bistatic sidelobe compensation. Radar signals reflect off of a flat plate that changes orientation (e.g., elevation and/or azimuth angle) and position relative to a mounting position of a specific radar sensor being calibrated. For each radar sensor, measurements may be obtained across a range of translational positions of the flat plate. Highly accurate calibration errors are determined for each radar sensor this way. By calibrating radar systems repositioning the target during the data collection in this way, the prominence of any bistatic sidelobes appearing in measurements may be reduced or prevented, which may enable less-complex and more-accurate calibration of each unique radar system installation. An indication of each calibration error may be output for use in individually adjusting the mounting position of each specific radar sensor within a radar system.

## Claims

### Claim 1

A method, comprising:
causing, by one or more processors of a calibration system, a flat plate target to be at a first position in a test environment, the first position being relative to a mounting position of a particular radar sensor of a radar system that is arranged in the test environment to be calibrated, and including a respective elevation angle and a respective translational position relative the mounting position of the particular radar sensor;
collecting, by the processors and from the particular radar sensor, first data indicative of first radar signals that reflect off of the flat plate target at the first position;
determining, by the processors, based on the first data, a first calibration error for the particular radar sensor at the first position;
causing, by the one or more processors, the flat plate target to be at one or more additional positions relative the mounting position of the particular radar sensor, each of the additional positions including a respective elevation angle and a respective translational position relative the mounting position of the particular radar sensor;
collecting, by the processors and from the particular radar sensor, additional data associated with each of the additional positions, the additional data being indicative of additional radar signals that reflect off of the flat plate target at each of the additional positions;
determining, by the processors, based on the additional data associated with each of the additional positions, an additional calibration error for each of the additional positions;
determining, by the processors, based on the first calibration error for the first position and each additional calibration error for each of the additional positions, a combined calibration error for that particular sensor given the mounting position of the particular radar sensor within the radar system; and
outputting, by the processors, an indication of the combined calibration error for use in compensating the radar system for the combined calibration error of the particular radar sensor to calibrate the radar system.

### Claim 2 (depends on 1)

The method of claim 1, further comprising:
determining, based on the first calibration error for the first position and each additional calibration error for each of the additional positions, a standard deviation calibration error for the particular radar sensor across the first position and the additional positions;
determining, based on the first calibration error, each of the additional calibration errors, and the standard deviation calibration error, an outlier calibration error set for the particular sensor and a remaining, inlier calibration error set for the particular radar sensor; and
determining, based on the inlier calibration error set, a more accurate combined calibration error for the particular radar sensor than another combined calibration error for the particular radar sensor that is based on the outlier calibration set,
wherein outputting an indication of the combined calibration error includes outputting an indication of the more accurate combined calibration error.

### Claim 3 (depends on 2)

The method of claim 2, wherein determining the inlier calibration error set comprises:
determining, based on the standard deviation calibration error, a tolerance value;
determining whether a portion of each of the first calibration error and each additional calibration error are within a range of the combined calibration error plus or minus the tolerance value; and
grouping, into the inlier calibration error set, the portion of each of the first calibration error and each additional calibration error determined to be within the range.

### Claim 4 (depends on 1)

The method of claim 1, wherein outputting the indication of the combined calibration error comprises outputting the combined calibration error for use in compensating the radar system to reduce effects from bistatic sidelobes.

### Claim 5 (depends on 1)

The method of claim 1, wherein the particular radar sensor is a corner radar sensor.

### Claim 6 (depends on 1)

The method of claim 1, wherein outputting an indication of the combined calibration error enables an adjustment to the mounting position of the particular radar sensor to be at an azimuth angle accuracy and elevation angle accuracy of less than 1 degree.

### Claim 7 (depends on 1)

The method of claim 1, wherein outputting an indication of the combined calibration error includes providing the combined calibration error to a processor of the radar system that is configured to compensate for the combined calibration error for that particular sensor within the radar system.

### Claim 8 (depends on 1)

The method of claim 1, wherein the flat plate target has a planar surface including a width dimension and a length dimension, and the flat plate target comprises a multiple-point target.

### Claim 9 (depends on 8)

The method of claim 8, wherein:
the planar surface of the flat plat target is mapped using a grid of the length dimension and the width dimension; and
the respective translational position of each of the first position and the additional positions corresponds to a different point on the grid along a centerline of the length dimension.

### Claim 10 (depends on 1)

The method of claim 1, wherein the radar system is arranged in the test environment for close-range calibration.

### Claim 11 (depends on 10)

The method of claim 10, wherein the mounting position of the particular radar sensor is less than 2 meters from the flat plate target.

### Claim 12 (depends on 1)

The method of claim 1, wherein the particular radar sensor comprises a low-resolution and further comprises an asymmetric gain pattern.

### Claim 13 (depends on 1)

The method of claim 1, wherein the radar system is configured to operate in a vehicle.

### Claim 14 (depends on 13)

The method of claim 13, wherein the radar system is installed in the vehicle when arranged in the test environment.

### Claim 15 (depends on 1)

The method of claim 1, wherein the respective elevation angle and the respective translational position of each of the first position and the additional positions are unique among the first position and the additional positions.

### Claim 16 (depends on 15)

The method of claim 15, wherein:
the first position includes the respective elevation angle, the respective translational position, and a respective azimuth angle relative to the mounting position of the particular radar sensor;
each of the additional positions includes the respective elevation angle, the respective translational position, and a respective azimuth angle relative to the mounting position of the particular radar sensor; and
the respective azimuth angle of each of the first position and the additional positions is different than the respective azimuth angle of each other of the first position and the additional positions.

### Claim 17 (depends on 1)

The method of claim 1, further comprising:
determining, for each radar sensor of the radar system, a respective combined calibration error for that radar sensor; and
outputting an indication of the respective combined calibration error for each of the radar sensors to be used in adjusting the mounting position of each of the radar sensors to calibrate the radar system.

### Claim 18

A calibration system, comprising at least one processor configured to:
cause a flat plate target to be at a first position in a test environment, the first position being relative to a mounting position of a particular radar sensor of a radar system that is arranged in the test environment to be calibrated, and including a respective elevation angle and a respective translational position relative to the mounting position of the particular radar sensor;
collect, from the particular radar sensor, first data indicative of first radar signals that reflect off of the flat plate target at the first position;
determine, based on the first data, a first calibration error for the particular radar sensor at the first position;
cause the flat plate target to be at one or more additional positions relative to the mounting position of the particular radar sensor, each of the additional positions including a respective elevation angle and a respective translational position relative the mounting position of the particular radar sensor;
collect, from the particular radar sensor, additional data associated with each of the additional positions, the additional data being indicative of additional radar signals that reflect off of the flat plate target at each of the additional positions;
determine, based on the additional data associated with each of the additional positions, an additional calibration error for each of the additional positions;
determine, based on the first calibration error for the first position and each additional calibration error for each of the additional positions, a combined calibration error for that particular sensor given the mounting position of the particular radar sensor within the radar system; and
output an indication of the combined calibration error for use in compensating the radar system for the combined calibration error of the particular radar sensor to calibrate the radar system.

### Claim 19 (depends on 18)

The system of claim 18, further configured to:
determine, based on the first calibration error for the first position and each additional calibration error for each of the additional positions, a standard deviation calibration error for the particular radar sensor across the first position and the additional positions;
determine, based on the first calibration error, each of the additional calibration errors, and the standard deviation calibration error, an outlier calibration error set for the particular sensor and a remaining, inlier calibration error set for the particular radar sensor; and
determine, based on the inlier calibration error set, a more accurate combined calibration error for the particular radar sensor than a combined calibration error for the particular radar sensor that is based on the outlier calibration set,
wherein outputting an indication of the combined calibration error includes outputting an indication of the more accurate combined calibration error.

### Claim 20 (depends on 19)

The system of claim 19, wherein determining the inlier calibration error set comprises:
determining, based on the standard deviation calibration error, a tolerance value;
determining whether a portion of each of the first calibration error and the additional calibration errors are within a range of the combined calibration error plus or minus the tolerance value; and
grouping, into the inlier calibration error set, the portion of each of the first calibration error and the additional calibration errors determined to be within the range.