On the measurement procedures for the assessment of the specific absorption rate (SAR) from MIMO cellular-equipment of fast varying relative phases

This article introduces a measurement methodology for the evaluation of the specific absorption rate (SAR) of MIMO systems (multiple-input and multiple-output) in which the relative phases between the antennas are rapidly changing and in very short durations. This measurement methodology is enabled by SAR systems that uses vector field measurements combined with a vector spectral analysis of the measured radiofrequency signals for SAR assessment. By exploiting the equivalence principle and the uniqueness of the solution of Maxwell’s equation, the proposed approach allows for an accurate SAR assessment of complex MIMO systems in a very short duration (few seconds).