IEC IEEE 62704-1-2017 pdf download.Determining the peak spatial-average specific absorption rate (SAR) in the human body from wireless communications devices, 30 MHz to 6 GHz – Part 3: Specific requirements for using the finite difference time domain (FDTD) method for SAR calculations of mobile phones.
5 Simulation procedure
5.1 General Clause 5 presents the steps that shall be followed to compute SAR from a mobile phone placed against a head or a body phantom. The procedure requires voxel models derived from the CAD data files of the DUT and of either the SAM head phantom or the body phantom.
5.2 General considerations The practical considerations for the application of the FDTD method are provided in Annex C of IEC/IEEE 62704-1 :201 7. Since the standard FDTD method relies on the Cartesian Yee cell, stair casing of curved surfaces is a problem that needs special consideration, particularly for the case of the DUT and the SAM head phantom. To limit stair casing, the positioning of the DUT against the SAM phantom shall be achieved by performing transformations such as translations and rotations on the SAM phantom only. The body phantom should preferably be reconstructed using the built-in drawing features of the numerical simulation tool when available. It can be easily aligned with both the handset and the FDTD axes.
5.3 General mesh settings For the FDTD method, the intrinsic problem of choosing a sufficiently small cell or grid size yet limit the memory requirements can be challenging. The wavelength in the material with the highest relative permittivity generally dictates the required minimum grid step. To mesh the free-space surrounding the phone and the phantom, a cell size corresponding to about λ /30 to λ /1 0 may be sufficient, where λ is the smallest wavelength corresponding to the wave propagation in the material with the highest relative permittivity. Since the relative permittivities of the materials present in a mobile phone are usually low – typically in the range 2 to 1 0 – the tissue equivalent liquid is expected to have the highest relative permittivity. Since this is generally insufficient for modelling the smaller components in a mobile phone, it may be necessary to further decrease the cell size to fully account for fine details such as slots or gaps or small components. The cell size may then be much smaller than the minimum cell size imposed by the highest relative permittivity of the materials present in the computational domain.
5.4 Simulation parameters Practical considerations for the application of the FDTD such as voxel size, stability, absorbing boundaries are described in IEC/IEEE 62704-1 :201 7, Annex C.
5.5 DUT model
5.5.1 General Prior to performing the SAR calculation using the head or the body phantom, the numerical simulation shall first be undertaken considering the DUT alone, i.e. free space configuration. The validity of the numerical model of the DUT shall be verified as described in Clause 7. A DUT model normally contains many different solids, typically more than one hundred, making this model a very complex structure to handle. Given the complexity of recent generation wireless handsets used by consumers and the extensive time required for device modelling, the only practical approach for producing the FDTD mesh is by importing the mechanical CAD file of the DUT, and to automatically generate the FDTD model for the handset. The file with the model shall be exported from the mechanical engineering CAD tool in a format that can be easily imported into the FDTD simulation tool (usually SAT or IGES file format). Prior to the export of the CAD model, all parts shall be assembled and correctly aligned with respect to each other.IEC IEEE 62704-1 pdf download.