Direction-of-Arrival Estimation Method Based on Asynchronous Control Reconfigurable Intelligent Surface

In this paper, a direction of arrival (DOA) estimation method for reconfigurable intelligent surface (RIS) with asynchronous control is proposed. By designing the starting time of state switching of different electromagnetic units of RIS, the states of different RIS units are interleaved within a symbol period. So as to improve the dimension of the received signal without changing the state switching rate of electromagnetic units. Then we propose an electromagnetic unit design algorithm with minimum orthogonal weight to improve the estimation accuracy of DOA according to the law of asynchronous control. The simulation results show that the surface has lower root mean squared error (RMSE) and can estimate more signal sources than the traditional synchronous control method.