Evaluation of reflections in a MIMO OTA test setup

With the commercialization of MIMO devices, accurate over-the-air testing has become a major research area in mobile communications. Several test methods are investigated in the related work. This paper discusses the anechoic chamber method and specifically deals with reflections between probes on the multi-probe ring. It is shown that reflections are at least 25 dB below the direct path. The paper also raises the difficulties to accurately measure the level of reflections in a real setup, due to instabilities.