Reconfigurable Coding Design for Transmissive RIS-Aided DOA Estimation by Single Receiving Sensor

Reconfigurable intelligent surfaces (RIS) offer efficient control over the amplitude/phase of reflected/transmitted signals, providing a cost-effective solution for direction of arrival (DOA) estimation. Existing RIS-aided DOA systems suffer from poor sensing matrix orthogonality due to random phase coding, limiting performance when using compressive sensing-based algorithms. To address this issue, we propose a reconfigurable coding design method for transmissive RIS-aided DOA estimation by single receiving sensor. We reformulate the reconfigurable coding design as a Frobenius norm minimization problem, where the Gram matrix of the equivalent sensing matrix is rendered to approximate with an identity matrix. The reconfigurable coding is deterministically designed as the product of a unitary matrix and a partial Hadamard matrix. Simulation results show superior angle estimation accuracy over random coding under the same SNR, reducing the number of measurements by at least 25%.