User interaction with antenna arrays in MIMO-enabled laptops

Operation of wireless personal communications terminals in the near vicinity of the user inherently faces the problem of electromagnetic (EM) coupling between the device and the biological tissues. In this paper the effects of electromagnetic human interaction is studied for a laptop MIMO array, where four integrated antenna elements can operate simultaneously. Two points of view are considered: array performance and EM dosimetry. The first one addresses not only the degradation of antenna array performance but includes also the effect of the human proximity on the array characteristics, namely scattering matrix, total active reflection coefficient (TARC), radiation efficiency and envelope correlation between port signals. The exposure of the human tissues to EM radiation is expressed in terms of specific absorption rate (SAR). All those characteristics are evaluated as a function of the array excitation scheme (including phased array approach and MIMO-like signalling) and compared to simple scenarios where all the power is radiated only by one antenna element.