Impact of number of probe antennas for MIMO OTA spatial channel emulator

OTA (Over-The-Air) performance of MIMO (Multiple-Input Multiple-Output) enabled mobile terminals employing multi-antennas can be evaluated using the spatial channel emulator which reproduces the multi-path environment around the mobile terminal in an anechoic chamber. Antenna properties of an antenna correlation in addition to the received power for the multi-antenna mounted on a mobile terminal should be adequately evaluated in the spatial channel emulator. In this paper, we investigate based on the calculation and measurement the impact of the number of probe antennas for a spatial channel emulator considering the radiation characteristics of antennas under test with a mutual coupling effect taking an antenna correlation that has a substantial impact on MIMO performance as the criterion employing the power angular spectrum of uniform and cluster model. We clarify that probe antennas should be appropriately aligned in terms of the numbers depending on an intended angular spread of arriving waves and an element spacing of antennas under test. We also present the results of the MIMO OTA testing based on three types of channel models as practical applications of the spatial channel emulator employing the practical antenna configuration mounted on the mobile phones as antennas under test.