This paper adapted the neural network for the estimating of the direction of arrival (DOA). It uses
an unsupervised adaptive neural network with APEX algorithm to extract the principal components
that in turn, are used by Capon method to estimate the DOA, where by the PCA neural network we
take signal subspace only and use it in Capon (i.e. we will ignore the noise subspace, and take the
signal subspace only)