On the Gap between the Amplitude and Phase Modulation Layers in a Transmitarray Collimator

Over-the-air (OTA) testing has become more and more popular in the communication device industry, especially for streamline product measurements. Because of its low profile and ease of manufacturing, transmitarray-based compact antenna test range (CATR) systems can be quite appropriate for cost-effective and efficient measurements. The CA TR collimator features two metasurface layers that incorporate phase modulation functions and magnitude modification functions, respectively. The collimator's performance is influenced by the gap length that exists between the two metasurfaces. The theoretical analysis of the gap effect is shown, and an optimization technique is proposed to improve the quiet zone's quality. The final transmitarray-based CATR achieves a high aperture ratio of 60%.