1. A method of operating a radar receiver system implemented as a processor for determining an angle of arrival of a radar signal received from an emitter at an antenna, the method comprising: given a radiation pattern of the antenna, in an initial iteration, representing an approximation of the pattern as a plurality of windows, each window defined by two boundaries and each of the boundaries having an azimuth angle value and an amplitude value, the approximation further includes an inflexion point being a boundary having an amplitude value higher than the other boundaries; for each of the boundaries, adjusting at least one of a respective azimuth angle value or an amplitude value of a subject boundary; generating a next approximation of the pattern based on the adjustment to the subject boundary; comparing the next approximation to an approximation of the pattern generated in a prior iteration, which includes the initial approximation; comparing a slope associated with a portion of the next approximation represented by each window to a non-zero threshold value; determining whether the next approximation is constantly increasing on one side of the inflexion point and constantly decreasing on the other side of the inflexion point; identifying the next approximation as an optimized monotonic fit based on the comparisons and determination; and calculating the angle of arrival of the radar signal based on the optimized monotonic fit.