# IEEE IEC 62704-4-2020 pdf download

IEEE IEC 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.

For FEM, a large number of different implementations exist. This document is not restricted to any particular formulations or implementations of FEM. Numerical errors depend on the particular implementation (basis functions, etc.). To the best knowledge of the working group that developed this document, there is no comprehensive methodology to quantify these errors, and the numerical solutions for generic examples converge against their physical solutions when the step sizes of the computational meshes approach zero. The verification of an FEM code according to this document is carried out by demonstrating the convergence of the numerical solution to the physically correct one for a number of relevant benchmarks, where an exact analytical solution of the physical problem is available.

For the more complex benchmarks, code verification for both FDTD and FEM relies on typical generic configurations used in SAR measurements. Exact numerical or analytical solutions are generally not available for such configurations. Reference solutions have been obtained, e.g. with alternative methods, interlaboratory comparisons, or validation against experimental results. Providing that the parameters (dielectrics, exact dimensions, etc.) of a model to be simulated are known with sufficient accuracy, the deviations of the simulation results from reference results generally depend on details of the meshed representation of the model geometry in the computational domain. The meshing parameters are usually under the control of the code or its operator. Hence, a comparison of the results of complex geometries would rather show differences between individual simulations and not between the numerical methods as such.

8.1.2 Code performance verification

The code performance verification described in 8.2 and 8.3 provides methods to determine whether the FEM has been implemented correctly and works accurately within the constraints of its finite numerical accuracy. It further determines the quality of the open boundary conditions and specific parts of the post processing algorithms. All numerical results are compared to the analytical solutions of the respective physical problems. Subclause 8.4 specifies the test of the implementation of the psSAR averaging algorithm according to 6.2.

The results for the code verification shall be assessed as a function of the applied degrees of freedom (D0F).

NOTE 1 The number of D0F, i.e. the total number of unknowns, depends on the number of elements and the number of unknowns associated with each element (see clause 5).

NOTE 2 In general, the number of D0F can be chosen individually for each benchmark to reach the required accuracy. The benchmarks do not specify the number of D0F to apply, but may give guidance on how to choose or modify it.

8.1.3 Canonical benchmarks

The canonical benchmarks described in 8.5 assess the accuracy of a code and its applicability considering the interaction of its different modules, such as mesh generation, computational kernel, representation of sources, data extraction algorithms of the post processor, etc.

8.2 Code performance verification

8.2.1 Propagation In a rectangular waveguide

The assessment of the propagation characteristics of a code provides the means to verify the basic implementation of the FEM, such as accuracy and convergence for free space and for dielectric interfaces. Rectangular waveguides are characterized in terms of wave number and reflection coefficient for the different configurations. Convergence to the physically correct value within a specified tolerance shall be demonstrated for an increasing number (at least three) of DoF. Minimum or maximum values are not specified for the number of DoF.

a) Specification of the waveguide — The rectangular waveguide model is specified with perfectly conducting walls (Figure 1). Its widths in the x- and y-directions are 120 mm and 60 mm, respectively. All directions and dimensions correspond to the coordinate system as shown in Figure 1. The excitation is placed perpendicular to the orientation of the waveguide. The distance from the source to the fields to be recorded shall be 60 mm. The length of the waveguide should be chosen such that reactive fields that can be caused by the truncation of the computational domain do not reach the region where the fields are recorded.