A study on design of spatial fading emulator based on Clarke´s model

In this paper, we describe a design method of a spatial fading emulator based on Clarke´s model which is one of OTA (Over-The-Air) measurement systems for creating an artificial propagation environment for evaluation of multi-antenna handsets. The emulator is composed of scatterers located at equal angle intervals on a circle around the handset. For evaluating multi-antenna systems such as MIMO, OTA systems should generate multi-path propagation environment where spatial correlation is correctly realized. Spatial fading emulator based on Clarke´s model with limited number of scatterers can generate the propagation environment inside a quiet zone where spatial correlation is correctly realized around the center of emulator. In this paper, we show that the size of quiet zone is derived by the Bessel function with the order of the number of scatterers. Furthermore, we show the variation of the size of quiet zone against the offset angle of test antennas. Finally, an equation for obtaining the required number of scatterers that satisfies required size of quiet zone is presented.