Method and apparatus for determination of direction of arrival angle

A method for determining direction-of-arrival angles for radar signals, the method comprising:

• receiving an input dataset indicative of amplitudes and phases of radar signals received at a plurality of antenna elements, wherein the radar signals have reflected from a plurality 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 the objective function is indicative of a correspondence between the possible direction-of-arrival angles of said plurality of targets and the input dataset;
• determining a beam forming spectrum, the beam forming spectrum comprising a correlation of the input dataset with a set of beamsteering vectors, wherein the set of beamsteering vectors include one beamsteering vector for each point of the search space wherein a beamsteering vector comprises a function of direction-of-arrival angle that represents an expected response at the plurality of antenna elements of a target with unit amplitude;
• performing a first determination process for evaluation of the objective function comprising:
• identifying two or more peaks in the beam forming spectrum based on a predetermined threshold level, whether the two or more peaks comprise peaks that exceed the predetermined threshold level, determining two or more candidate direction-of-arrival angles that correspond to the identified two or more peaks, and wherein the number of candidate direction-of-arrival angles correspond to the number of identified peaks;
• defining a first-reduced search space based on the two or more candidate direction-of-arrival angles;
• performing a second determination process for evaluation of the objective function comprising:
• determining a peak direction-of-arrival angle comprising the direction-of-arrival angle that corresponds to a peak in the beam forming spectrum that has the greatest magnitude;
• wherein the method comprises evaluating the objective function to determine a final set of estimated direction-of-arrival angles for the plurality of targets comprising the direction-of-arrival angles which one of maximize or minimize the objective function, wherein the objective function is evaluated over the first reduced search space and wherein said evaluating of the objective function is performed with the direction-of-arrival angle of one of the plurality of targets set to the peak direction-of-arrival angle and the direction-of-arrival angle of the other of the plurality of targets is iteratively set to the direction-of-arrival angles that correspond to the points of the search space.