Accurate Direction–of–Arrival Estimation Method Based on Space–Time Modulated Metasurface

Abstract

A metasurface(MTS)-based direction of arrival (DoA) estimation method is presented. The method exploits the properties of space-time modulated reflective metasurfaces to estimate in real-time the impinging angle of an illuminating monochromatic plane wave. The approach makes use of the amplitude unbalance of the received fields at broadside at the frequencies of the two first-order harmonics generated by the interaction between the incident plane wave and the modulated metasurface. Here, we first describe analytically how to generate the desired higher order harmonics in the reflected spectrum and how to realize the breaking of the spatial symmetry of each order harmonic scattering pattern. Then, the 1-D omnidirectional incident angle can be analytically computed using +1stand −1st-order harmonics. The approach is also extended to 2-D DoA estimation by using two orthogonally arranged 1-D DoA modulation arrays. The accuracy of 1-D DoA estimation is verified through full-wave numerical simulations. Compared to conventional DoA estimation methods, the proposed approach simplifies the computation and hardware complexity, ensuring at the same time estimation accuracy. The proposed method may have potential applications in wireless communications, target recognition, and identification.

Artificial Neural Network for Direction‐of‐Arrival Estimation and Secure Wireless Communications Via Space‐Time‐Coding Digital Metasurfaces

“…For example, programmable metasurfaces were utilized as physical sampling devices to estimate the signal direction from the characteristics of the scattered waves by switching a large amount of metasurface-pattern matrices. [52][53][54] Another approach based on the timemodulated arrays [55] or space-time-modulated metasurfaces [56,57] calculates the direction of signal from both amplitudes and phases of the harmonics. Therefore, these methods still have stringent requirements on equipment and environment in their applications [54][55][56][57] or require excessive data storing and processing, [52,53] leading to the limited accuracy and applicability.…”

“…[52][53][54] Another approach based on the timemodulated arrays [55] or space-time-modulated metasurfaces [56,57] calculates the direction of signal from both amplitudes and phases of the harmonics. Therefore, these methods still have stringent requirements on equipment and environment in their applications [54][55][56][57] or require excessive data storing and processing, [52,53] leading to the limited accuracy and applicability.…”

Sensing and Reconfigurable Reflection of Electromagnetic Waves From a Metasurface With Sparse Sensing Elements

“…In addition, separating individual channels from the join-estimation model is a tedious task. To circumvent this issue, recent works have proposed using an external receiver that detects signal impinging on a time-space coded metasurface [30], [31]. While this method allows for simultaneous sensing and reflection, it requires the use of an additional receiver away from the RIS.…”

Diverse Frequency Time-Modulation for Passive False Target Spoofing: Design and Experiment

“…The time-varying response has been realized through integrating many kinds of dynamic controllable devices on the metasurface unit-cell, such as pin diode [18], varactor [19], MEMS [20], graphene [21], liquid crystal [22], enabling the dynamic control of their scattering response using an electrical modulating signal at a fixed modulating frequency. Its temporal periodic profile defines the type of modulation scheme applied to the metasurface, that can generate in reflection single-side-band (SSB) spectrums [13], [17], i.e., a controlled frequency shift of the illuminating signal, double-side-band (DSB) spectrums [26] and even spread spectrums [16].…”

“…Recently, such spectrum manipulating capabilities have been exploited for several applications [17], [23]- [26]. For jamming application, space-time modulated metasurfaces have been proposed for achieving Doppler effect control and radar deception [27]- [29] by linearly varying the modulation frequency of the surface reactance of the metasurface, i.e., varying the phase of the reflection coefficient exhibited by metasurface.…”