Method and device for determining an angle of a target object
A method is provided for estimating an angle of an object with respect to a vehicle. A transformation of reflected radar signals is calculated, wherein the result of the transformation depends on a range with respect to the vehicle. A long beam vector is generated for respective range bins provided by the transformation by rearranging the result of the transformation such that the respective long beam vector comprises elements of the transformation from radar all receiver elements for each range bin. A reference vector is calculated for each range bin based on a signal model which depends on the motion of the target object relative to the vehicle and which is parameterized regarding the angle of the target object. The long beam vector and the reference vector are correlated, and the angle of the target object is determined based on the correlation result.
1. A method comprising:
estimating an angle of a target object with respect to a host vehicle by:
sending, with at least one radar transmit element of a plurality of antenna transmit elements of a radar system of the host vehicle, a radar signal towards the target object;
receiving, with at least one antenna receiver element of a plurality of receive elements of the radar system, radar signals reflected by the target object;
calculating, via a processing unit of the host vehicle, a transformation of the reflected radar signals including a result of the transformation that depends on a range with respect to the host vehicle;
generating, via the processing unit and for each of a set of range bins provided by the transformation, a long beam vector by rearranging the result of the transformation including rearranging beam vector elements for chirps of the reflected radar signals such that the long beam vector comprises elements of the transformation from all receiver elements, wherein each entry of the long beam vector corresponds to one of the range bins in the set of range bins;
calculating, via the processing unit and for each range bin in the set of range bins, a reference vector based on a signal model that depends on a motion of the target object relative to the radar system and that is parameterized regarding the angle of the target object, wherein each of the reference vectors is calculated based on i) a range rate or velocity of the target object relative to the radar system, and ii) a respectively selected angle in a predefined range of angles; and
determining a correlation result by correlating, via the processing unit, the long beam vector and the reference vectors for the predefined range of angles; and
outputting, via the processing unit, the angle of the target object determined based on the correlation result for controlling the host vehicle.
2. The method according to claim 1 , wherein the transformation of the reflected radar signals includes a Fourier transform.
3. The method according to claim 1 , wherein determining the correlation result comprises calculating an inner product of the long beam vector and each of the reference vectors.
4. The method according to claim 1 , wherein determining the angle of the target object comprises finding at least one maximum of the correlation result.
5. The method according to claim 1 , wherein:
a region of interest is defined for the range of angles; and
the correlation result is determined for the region of interest only.
6. The method according to claim 1 , further comprising applying an additional angle finding procedure to the correlation result to determine the angle of the target object.
7. The method according to claim 6 , wherein the additional angle finding procedure is based on an iterative adaptive approach.
8. The method according to claim 1 , wherein the motion of the target object relative to the radar system is measured by an additional detection unit installed in the host vehicle.
9. The method according to claim 1 , further comprising deriving, from former measurements performed via the radar system, information regarding the motion of the target object relative to the radar system.
10. The method of claim 1 , wherein each of the reference vectors has a same number of entries as the long beam vector.
11. The method of claim 1 , wherein the predefined range of angles is −90° to +90°.
12. The method of claim 11 , wherein:
the long beam vector and the reference vectors are correlated for a plurality of values of the angle θ; and
the angle θ is varied in steps of one degree over the predefined range of angles of −90° to +90°.
13. A system comprising a processing unit configured to:
estimate an angle of a target object with respect to a host vehicle by
sending, with at least one radar transmit element of a plurality of antenna transmit elements of a radar system of the host vehicle, a radar signal towards the target object
receiving, with at least one antenna receiver element of a plurality of receive elements of the radar system, radar signals reflected by the target object,
calculating a transformation of the reflected radar signals including a result of the transformation that depends on a range with respect to the host vehicle,
generating, for a set of range bins provided by the transformation, a long beam vector by rearranging the result of the transformation including rearranging beam vector elements for chirps of the reflected radar signals such that the long beam vector comprises elements of the transformation from all receiver elements, wherein each entry of the long beam vector corresponds to one of the range bins in the set of range bins,
calculating, for each range bin in the set of range bins, a reference vector based on a signal model that depends on a motion of the target object relative to the radar system and that is parameterized regarding the angle of the target object, wherein each of the reference vectors is calculated based on i) a range rate or velocity of the target object relative to the radar system, and ii) a respectively selected one of a predefined range of angles, and
determining a correlation result by correlating the long beam vector and the reference vector for the predefined range of angles; and
output the angle of the target object determined based on the correlation result for controlling the host vehicle.
14. The system according to claim 13 , wherein the transformation of the reflected radar signals includes a Fourier transform.
15. The system according to claim 13 , wherein the processing unit is configured to determine the correlation result by calculating an inner product of the long beam vector and each of the reference vectors.
16. The system according to claim 13 , wherein the processing unit is configured to determine the angle of the target object by finding at least one maximum of the correlation result.
17. The system according to claim 13 , wherein:
a region of interest is defined for the range of angles; and
the correlation result is determined for the region of interest only.
18. The system according to claim 13 , wherein the processing unit is further configured to apply an additional angle finding procedure to the correlation result to determine the angle of the target object.
19. The system according to claim 18 , wherein the additional angle finding procedure is applied using an iterative adaptive approach.
20. The system according to claim 13 , wherein the motion of the target object relative to the radar system is measured by an additional detection unit installed in the host vehicle.
21. The system according to claim 13 , wherein the processing unit is further configured to derive, from former measurements performed via the radar system, information regarding the motion of the target object relative to the radar system.
22. The system according to claim 13 , further comprising at least one of:
the radar system of the host vehicle; or
the host vehicle.
23. A non-transitory computer readable medium comprising instructions that, when executed, cause a processing unit to:
estimate, using a radar system of a host vehicle, an angle of a target object with respect to the host vehicle by:
sending, with at least one radar transmit element of a plurality of antenna transmit elements of the radar system of the host vehicle, a radar signal towards the target object;
receiving, with at least one antenna receiver element of a plurality of receive elements of the radar system, radar signals reflected by the target object;
calculating a transformation of the reflected radar signals including a result of the transformation that depends on a range with respect to the host vehicle;
generating, for each range bin in a set of range bins provided by the transformation, a long beam vector by rearranging the result of the transformation including rearranging beam vector elements for chirps of the reflected radar signals such that the long beam vector comprises elements of the transformation from all receiver elements, wherein each entry in the long beam vector corresponds to one of the range bins in the set of range bins;
calculating, for each range bin in the set of range bins, a reference vector based on a signal model that depends on a motion of the target object relative to the radar system and that is parameterized regarding the angle of the target object, wherein each of the reference vectors is calculated based on i) a range rate or velocity of the target object relative to the radar system, and ii) a respectively selected one of a predefined range of angles; and
determining a correlation result by correlating the long beam vector and the reference vector for the predefined range of angles; and
output the angle of the target object determined based on the correlation result for controlling the host vehicle.