Conformal Time-Modulated Metasurface With Customized Optical Transparency for Direction of Arrival Estimation

Direction of arrival (DoA) estimation is critical for applications such as radar tracking and wireless communication; however, traditional methods are often constrained by high hardware costs and substantial computational demands. This study introduces a novel flexible and optically transparent time-varying phase-modulated metasurface that not only enables cost-effective DoA estimation but also offers conformability and optical-transparency, making it suitable for complex surfaces. Through simulations and experimental validation, the proposed metasurface demonstrates real-time and flexible control of the reflection phase of electromagnetic (EM) waves under both normal and oblique incidences. This capability generates discrete harmonic frequency components with varying frequency shifts and amplitudes. Furthermore, we propose an innovative method that leverages the unique amplitude characteristics of harmonic components as “EM fingerprint.” By constructing a predefined fingerprint library and utilizing correlation analysis, this method enables efficient and precise DoA estimation. Experimental results reveal that this method achieves subdegree accuracy, strong robustness to noise, and significantly reduced computational complexity compared to traditional multiple signal classification (MUSIC) algorithm. This approach addresses key challenges in scalability and adaptability, with potential applications in wearable devices, unmanned aerial vehicles (UAVs), and optical camouflage systems.