Research on Accurate OTA Testing for Large-Form-Factor 5G IoT Devices in Medium-Sized Anechoic Chamber

Abstract

This letter focuses on whether accurate over-the-air (OTA) performance of large-form-factor (LFF) Internet-of-Things (IoT) devices (especially for vehicles) can be obtained from medium-sized anechoic chambers (ACs). For LFF IoT devices under test (DUTs), antenna locations are usually deviated significantly from the center of the OTA testing system due to mechanical positioner or chamber constraints in medium-sized ACs, which will lead to distortion for assessed OTA performance. This work evaluates the effect of offsetting the antenna under test integrated in LFF IoT DUTs from the center of the quiet zone on OTA integrated-type quantities. A new figure of merit <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R_OFF</i> has been defined to characterize the off-center extent, while the influence of which on OTA performance as well as associated simulations is presented based on statistical analysis. It can be found that the performance deviation is determined by <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R_OFF</i> rather than absolute off-center distance. The relationship between <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R_OFF</i> and performance deviation can be derived by using the least-squares fitting method. Additionally, it is acquired that for off-center scenario, performance deviation cannot be eliminated by increasing measurement grid density, yet can be reduced significantly by introducing off-center correction.