Accuracy Comparisons of Channel Emulation Methods for Two-dimensional Uniform and Three-dimensional Sectored Multi-probe Anechoic Chamber

─ Multiple-input-multiple-output (MIMO) overthe-air (OTA) testing has been seen as a promising solution for evaluation of the radio performance of MIMO devices. In this work, we compare the accuracy of two channel emulation methods, i.e., the prefaded signal synthesis (PFS) and the plane wave synthesis (PWS), in two-dimensional (2D) uniform and 3D sectored multi-probe anechoic chamber (MPAC), respectively. The PWS method is proven to be more accurate than the PFS for 2D uniform MPAC system. However, for 3D sectored MPAC system, the PFS method emerged to be better than the PWS method. To explain these seemingly contradicting findings, both the required number of active probes and the leakage of power spectrum are considered in this paper. It is found that the PWS method has higher emulation accuracy than the PFS method when the number of active probes becomes sufficiently large, whereas the PFS is more robust to the undersampling due to the limited number of active probes in practical 3D sectored MPAC system. Moreover, when the number of active probes is particularly small (less than the number of clusters in the probe panel), the emulation accuracy of the PWS method outperform its counterpart. Index Terms ─Multi-probe anechoic chamber (MPAC), over-the-air (OTA), pre-faded signal synthesis (PFS), plane wave synthesis (PWS).