Maximum likelihood separation of phase modulated signals

In this paper we present a Newton scoring algorithm for the maximum likelihood separation and direction of arrival estimation of constant modulus signals, using a calibrated array. The main technical step is the inversion of the Fisher information matrix, and an analytic formula for the update step in the Newton method. We present the algorithm based on the derived update and discuss potential initializations. We also present the computational complexity of the update. Finally we present simulation results comparing the method to the ESPRIT and the CM-DOA.