Nonparametric if and DOA estimation

A nonparametric algorithm for estimation of instantaneous frequency (IF) and direction-of-arrival (DOA) of wideband FM signals, at the uniform linear array (ULA), is considered. The IF estimation of signals received at the sensor array is performed by using positions of the Wigner distribution (WD) maxima. Information of the impinging signal´s IF is embedded in the IF estimates. It is extracted by linear interpolation of the obtained IF estimates. The L/sub 1/ norm is used for interpolation, instead of the standard L/sub 2/ norm, in order to improve performance in a high noise environment. Further improvement is achieved by applying a nonlinear filter, directly to the obtained IF estimates. The DOA is estimated by using a modified beamforming technique.