Method and apparatus for determination of direction of arrival angle

Patent metadata

Field	Value
Publication number	US-12578450-B2
Application number	US-202318469949-A
Country	US
Kind code	B2
Filing date	Sep 19, 2023
Priority date	Sep 27, 2022
Publication date	Mar 17, 2026
Grant date	Mar 17, 2026

Abstract

An apparatus configured to:
receive an input dataset indicative of radar signals, reflected from targets, received at an antenna; determine an objective function for evaluation over a plurality of points of a search space representing possible direction-of-arrival angles; evaluate the objective function for a first candidate number of targets; perform a first evaluation of a branch metric function based on a second candidate number of targets, wherein the branch metric function is indicative of a change in the objective function; and if the branch metric function is greater than a predetermined threshold, then evaluate the objective function for the second candidate number of targets; if the branch metric function is less than the predetermined threshold, then evaluate the objective function for the first candidate number of targets, wherein the evaluation is based on at least one of the first candidate number of targets having a different, second candidate direction-of-arrival angle.

First claim

The invention claimed is:

1 . An apparatus comprising a processor configured to:
receive, via an antenna array comprising a plurality of antenna elements, an input dataset indicative of an amplitude and phase of radar signals received at the plurality of antenna elements, wherein the radar signals have reflected from an unknown number of targets; determine an objective function, based on the input dataset, for evaluation over a plurality of points of a search space, the points of the search space representing possible direction-of-arrival angles of said radar signals from the plurality of targets and wherein evaluation of the objective function is indicative of the correspondence between the possible direction-of-arrival angles of said plurality of targets and the input dataset; evaluate the objective function for a first candidate number of targets K, wherein each target of the first candidate number of targets has a respective first candidate direction-of-arrival angle, each corresponding to a point in the search space; perform a first evaluation of a branch metric function based on a second candidate number of targets, K+1, comprising one more targets than the first candidate number of targets, wherein the branch metric function is indicative of a change in the objective function between an evaluation of the objective function based on the first candidate number of targets having the first candidate direction-of-arrival angles and an evaluation of the objective function based on the second candidate number of targets, and comprises a function of the respective first candidate direction-of-arrival angles of the first candidate number of targets; and if the branch metric function is greater than a predetermined threshold λ, then the processor is configured to:
evaluate the objective function for the second candidate number of targets K+1, wherein the evaluation is based on the first candidate number of targets, K, of the second candidate number of targets, K+1, having the respective first candidate direction-of-arrival angles and the remaining target of the second candidate number of targets, K+1, the remaining target comprising an additional-target having an additional-target-first-candidate direction-of-arrival angle;
if the branch metric function is less than the predetermined threshold λ, then the processor is configured to:
evaluate the objective function for the first candidate number of targets K, wherein the evaluation is based on at least one of the first candidate number of targets K having a different, second candidate direction-of-arrival angle; and
generate, at the processor, a final set of direction-of-arrival angles that comprises the direction-of-arrival angles that resulted from the evaluation of the objective function.

2 . The apparatus of claim 1 , wherein predetermined threshold λ is based on the candidate number of targets.

3 . The apparatus of claim 1 , wherein the objective function is formulated such that the evaluation of the objective function for the first candidate number of targets K comprises a function of two or more sub-functions, and
wherein the branch metric function comprises a function of at least one of the two or more sub-functions and an additional-target beamsteering vector, the additional-target beamsteering vector representing the expected response at the plurality of antenna elements of the additional-target at the additional-target-first-candidate direction-of-arrival angle.

4 . The apparatus of claim 1 , wherein the processor is configured to, if the branch metric function is less than the predetermined threshold λ, not evaluate the objective function for the second candidate number of targets K+1, wherein the evaluation is based on the first candidate number of targets, K, of the second candidate number of targets, K+1, having the respective first candidate direction-of-arrival angles and the remaining target of the second candidate number of targets, K+1, the remaining target comprising the additional-target having the additional-target-first-candidate direction-of-arrival angle and any other direction-of-arrival angle in the search space.

5 . The apparatus of claim 1 , wherein the branch metric function is also a function of the additional-target-first-candidate direction-of-arrival angle, comprising the angle of said one more target than the first candidate number of targets,
wherein the additional-target-first-candidate direction-of-arrival angle comprises any angle in the search space.

6 . The apparatus of claim 1 , wherein when the branch metric function is less than the predetermined threshold λ and the processor has evaluated the objective function for the first candidate number of targets K, wherein the evaluation is based on at least one of the first candidate number of targets K having a different, second candidate direction-of-arrival angle; and
the processor is configured to:
re-evaluate the branch metric function based on the second candidate number of targets, K+1, comprising one more target than the first candidate number of targets, wherein the branch metric function is a function of the candidate direction-of-arrival angles of the targets of the evaluated objective function comprising those that changed to said different, second candidate direction-of-arrival angle and those that remained as the first candidate direction-of-arrival angles.

7 . The apparatus of claim 1 , wherein the processor is configured to, as part of said evaluation of the objective function for the first candidate number of targets K and the first evaluation of the branch metric function:
determine a beamsteering matrix, A, of beamsteering vectors wherein each beamsteering vector represents a respective one of the first candidate number of targets K and wherein each beamsteering vector comprises a function that represents the expected response at the plurality of antenna elements from radar signals of unit amplitude reflected from a respective one of the targets at a respective one of the first candidate direction-of-arrival angles; determine a sub-function B wherein B=(A H A) −1 determine a sub-function y , wherein y =A H x and x represents the input dataset and wherein y represents a correlation of the input dataset with the beamsteering vectors of the beamsteering matrix; define the additional-target having the additional-target-first-candidate direction-of-arrival angle as a beamsteering vector, a K+1 ; calculate c wherein c=B A H a K+1 ; calculate d, wherein

d
=

1

a
_

K
+
1

H

⁢

a
_

K
+
1

-

a
_

K
+
1

H

Assignees

• Nxp Bv

Inventors

• Koppelaar Arie Geert Cornelis
• Bekooij Marco Jan Gerrit

Classifications

• G01S13/006

  Theoretical aspects (G01S7/418, G01S13/9094, G01S13/958 take precedence) · CPC title

• G01S7/352

  Receivers · CPC title

• G01S3/48

  the waves arriving at the antennas being continuous or intermittent and the phase difference of signals derived therefrom being measured · CPC title

• G01S3/06

  Means for increasing effective directivity, e.g. by combining signals having differently oriented directivity characteristics or by sharpening the envelope waveform of the signal derived from a rotating or oscillating beam antenna (comparing amplitude of signals having differently oriented directivity characteristics to determine direction G01S3/16, G01S3/28) · CPC title

• G01S13/4454

  phase comparisons monopulse, i.e. comparing the echo signals received by an interferometric antenna arrangement · CPC title