Maximum likelihood DOA estimation for constant-modulus signal

An investigation into the direction finding problem in the case of a constant-modulus signal is presented. A simple expression for the maximum likelihood estimator (MLE) is derived in the single source case. The MLE corresponds to an L₁-type beamformer as opposed to the L₂-beamformer that results in a deterministic but not necessarily constant-modulus signal. Numerical examples show that the proposed estimator has a performance very close to the Cramer-Rao bound for a wide range of scenarios