Compact MIMO Antenna OTA Measurement System With Utilization of Metasurface for Wavefront Manipulator

A novel application of the metasurface for minimizing the sub-6-GHz MIMO antenna measurement system is proposed. To reduce measurement errors across frequencies and within the measurement system, an active transmit-type metasurface based on the p-i-n diode is adopted, enabling compensation for phase without amplitude variation. Moreover, the unit cell is designed with a size of $20\times 20$ mm ( $0.25\lambda \times 0.25\lambda $ ) to reduce quantization loss. The mean square error (mse) of the E-field is calculated to verify wavefront uniformity. This article introduces a measurement method that can determine quiet-zone generation instead of relying on antenna probe measurements. This method utilizes path loss changes per unit distance. Based on the path loss difference measurement results, the metasurface can form a quiet zone approximately 30% closer to the receiver antenna. Additionally, it is confirmed that the proposed system can minimize measurement error by reconfiguring the metasurface across frequency variations.