This paper introduces an efficient procedure for the evaluation of the true exposure level, quantified by the peak averaged specific absorption rate (SAR), of multiple-input multiple-output (MIMO) communication devices operating transmission diversity. As compared to the traditional conservative evaluation of the SAR, that results from the unpractical testing of all the antenna-array states of the device, the assessment of the true exposure level enables higher margin for minimizing the SAR while maximizing the radiation performance of the device.

This paper introduces a rigorous and fast procedure for accurate assessment of the peak averaged specific absorption rate (SAR), quantifying the user exposure to the electromagnetic field radiation from new-radio communication devices. Focus is lent to the specific class of user equipment that exploit multiple-input multiple-output (MIMO) technology and using exclusive simultaneous excitations of the active antenna-array system, such as expected on 5G devices. In contrast with the required N(N-1)+1 measurements on traditional SAR systems that only take measurements of the amplitude of the electric field, it is demonstrated in this paper that only N+1 number of measurements are required to evaluate the true SAR of a Nantenna MIMO thanks to using a vector near-field based SAR measurement system.

The impact of wireless channel modeling on exposure to electromagnetic radiation is studied. Two methods are developed in order to assess the statistical properties of whole body Specific Absorption Rate for exposure estimation in indoor environment. The body model is exposed to a bundle of waves, named cluster, following the wireless channel modeling approach. The first method is analytical and based on the Uncorrelated Scattering Assumption of the incident waves. The second method is a classical stochastic method. The point is to identify the parameters of Wireless Channel which led to significant SAR's variation.

We report on the development of a method for measuring the permittivity and conductivity of fluids inside a sealed tank (or a pipe) by using an embedded coaxial probe. Permittivity and conductivity in the frequency range 600 MHz to 6 GHz are determined from measurements of a complex reflection coefficient by using a vector network analyser (VNA) that is connected to the embedded probe via a coaxial cable. Substitution methods for calibration of an inaccessible probe are studied in this paper. These require the VNA with attached cable to be calibrated prior to connecting the cable to the embedded coaxial probe. Measurement of permittivity and conductivity of fluids inside sealed tanks and pipes is needed for monitoring industrial processes, such as fermentation. The authors’ requirement, however, was to allow monitoring of a tissue-equivalent liquid that is contained inside a sealed tank. This tank is a component of a commercial system for rapid, multiple-band measurement of the specific absorption rate (SAR) of mobile phone handsets. Monitoring of permittivity and conductivity is needed to ensure compliance with international standards for SAR measurement. The paper also presents data for a new broadband (600 MHz to 6 GHz) tissue-equivalent liquid that is based on an oil-in-water emulsion. It is demonstrated that over an extended period of time, the liquid is stable, and an embedded coaxial probe enables its properties to be monitored with the required accuracy.

Abstract-This paper develops the kriging method to calculate the whole body Specific Absorption Rate (SAR) for any angle of incidence of a plane wave on any body model using a minimum number of Finite Difference Time Domain (FDTD) simulations. Practical application of this method is to study people's exposure. Thanks to kriging method, it will enable to answer to the challenge of studying the exposure in a realistic environment. This approach develops a new tool in order to improve the field of stochastic dosimetry. The kriging method is applied to a girl body model in order to determine the variogram model, then this model is validated on a boy body model. Thanks to only 40 numerical SAR values, kriging method enables to estimate any SAR value with a mean relative error under 3%.