On the accuracy of synthesised wave-fields in MIMO-OTA set-ups

The relatively small number of antennas available in MIMO-OTA setups makes aliasing inevitable in the classical Huygens-Fresnel approach to wave field synthesis. Although very successful in acoustics, the achievable areas/volumes with good wave field quality shrink rapidly under aliasing conditions. Much larger “sweet spots” can be achieved in MIMO-OTA setups by the use of alternative techniques like field matching through propagation matrix inversion. Nevertheless, as the generic OTA antenna arrangement is 2D, the generated field are close to elliptical, so, wave front curvature outside the plane of the antennas is inevitable, as is some amplitude decay with distance.