IEC/IEEE 62704-4:2020 pdf download – Determining the peak spatial-average specific absorption rate (SAR) in the human body from wireless communication devices, 30 MHz to 6 GHz – Part 4: General requirements for using the finite element method for SAR calculations.
7.2.2 Mesh convergence The mesh convergence has a major impact on the accuracy of the results; therefore, psSAR results produced with a specific initial mesh M need to be compared with psSAR results produced with a denser mesh M′. Either of the following two strategies shall be applied depending on whether the FEM code used for the psSAR evaluation employs adaptive mesh refinement or not. a) If the applied FEM code does not employ adaptive mesh refinement, the number of elements per wavelength used for the initial mesh M shall be increased by at least 50 % considering the respective wavelengths in the dielectrics. b) If the applied FEM code uses adaptive mesh refinement, additional adaptive passes shall be performed until the total number of elements has increased by at least 20 % for second or third lowest order and 50 % for lowest order. In both cases, the electric field vector components shall be recorded in the region where the psSAR maximum is expected (psSAR region). It shall be ensured that both the minimum and the maximum edge lengths in the psSAR region and the region around the antenna of the denser mesh M′ are not greater than 50 % of the respective edge lengths of M. The location of the electric field maximum in the psSAR region of mesh M′ shall not deviate by more than the minimum mesh edge length from the location of the electric field maximum within the psSAR region of mesh M. The maximum psSAR deviation shall be reported as an uncertainty with rectangular probability distribution. The coordinates of the psSAR region and antenna region shall be reported. 7.2.3 Open boundary conditions The impact of open boundary conditions shall be determined by moving the boundaries outward by one quarter-wavelength for several test cases, e.g. at the locations of the maximum electric field energy and magnetic field energy at the boundary. The maximum deviation of the target quantity (e.g. maximum deviation of psSAR) from all investigated cases with shifted open boundary conditions shall be reported.