A Complex Adaptive Phase Estimation (PE) filter, as presented in some concepts of the present disclosure, is an adaptive filter that accurately estimates the phase difference between signals. For example, the PE filter can estimate the phase difference between a complex primary signal and a complex incident signal, iteratively adapting the phase of a complex exponential by minimizing the mean squared error of a complex error signal. The PE filter can demonstrate accurate phase estimation and rapid convergence, with low computational complexity and storage requirements. In addition, the PE filter construction can be simplified to support absolute phase estimation of a single complex signal. Efficient complex normalization approximation can be developed to support practical PE filter implementation in computationally restrictive environments, including systems with real-time response constraints, and systems without efficient native or functional support for division or square root operations.