Robust detection of number of sources using the transformed rotational matrix

We present an accurate, robust, and computationally efficient number-of-source detection method, which utilizes the variance of transformed rotational submatrix (VTRS) as the criterion, Unlike the traditional methods that use the eigenvalues, the VTRS detector determines the number of sources by exploiting the eigenvectors of two subarrays. This method applies to arbitrary subarray geometries. In addition, no subjective threshold or extra parameter Is required. In conjunction with spatial smoothing, this method can also detect coherent signals. One novelty of the VTRS method is that not only can it detect the number of sources, it can also indicate the quality of measured data and determine the optimum smoothing array size for parameter estimation, because of the low computational complexity, the VTRS number detector is suitable for adaptive or real-time applications.