Direction‐of‐Arrival Estimation Method for Space‐Time Coding Metasurfaces Based on Harmonic‐Domain Complex Correlation

ABSTRACT

Space‐Time Coding Digital Metasurfaces (STCDM) generate multiple harmonic components under electromagnetic illumination, offering additional degrees of freedom for wave sensing. Based on space‐time coding metasurfaces, this paper proposes a harmonic‐domain direction‐of‐arrival (DOA) estimation method based on complex correlation. By jointly utilizing the amplitude and phase of modulation harmonics, a harmonic fingerprint vector is constructed for each incident direction, and a precomputed angle database is established over the entire angular space. DOA estimation is achieved by maximizing the complex correlation between the observed harmonic vector and database entries. Unlike conventional subspace‐based methods, the proposed approach avoids covariance matrix estimation and eigenvalue decomposition, enabling accurate DOA estimation under single‐snapshot conditions. The unified complex‐vector framework enhances angular resolution and noise robustness compared to methods using only amplitude or phase information. Simulation results demonstrate that high estimation accuracy is maintained even at low SNR, achieving an RMSE of 0.11° at −10 dB. This method provides a simple and effective solution for harmonic‐domain DOA estimation in STCDM systems.