Method and apparatus for determination of direction of arrival angle

A method for evaluating an objective function, the method, performed by a processor coupled to an antenna array comprising a plurality of antenna elements, the method comprising:

• receiving, via the antenna array, 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;
• determining 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;
• evaluating 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;
• performing a first evaluation of a branch metric function based on a second candidate number of targets, K+1, comprising one more target 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:
• evaluating 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:
• evaluating 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
• generating a final set of direction-of-arrival angles that comprises the direction-of-arrival angles that resulted from the evaluation of the objective function.