Harmonic Frequency Enhanced Direction of Arrival Estimation Using Non-Uniform Linear Arrays

This article introduces an innovative method to improve the accuracy of estimating the Direction of Arrival (DOA) by utilizing non-uniform linear arrays (NULAs) operating at harmonic frequencies. Common DOA techniques face challenges in maintaining sufficient degrees of freedom (DOFs) while minimizing the number of sensors. Our approach takes advantage of the extended array aperture of NULAs and the diverse frequencies involved in harmonics to address these challenges. We explore various NULA structures, such as nested arrays, coprime arrays, and coprime arrays with compressed inter-element spacing (CACIS), each with unique characteristics and requirements for enhancing DOFs at the third and fifth harmonics. Simulation results demonstrate a substantial increase in DOFs, emphasizing the effectiveness and adaptability of our method in improving DOA estimation across different NULA configurations. This research contributes not only to theoretical advancements in antenna array processing but also offers practical insights, showcasing the potential of our method to significantly enhance DOA estimation accuracy in complex signal environments.