CST2013: SAR Calculation

Post Processing: 2D/3D Field Post Processing SAR Calculation

Use this dialog to calculate whole-body averaged and local Specific Absorption Rates (SAR) based on results of a power-loss density monitor.

Label

The name of the SAR results in the navigation tree. Switch off the automatic labeling to manually define different labels for different settings made in the SAR special settings dialog box.

Powerloss density frame

Monitor: Select here the power-loss density monitor to be used for the SAR calculation

Frequency: Shows the frequency of the selected monitor:

Averaging mass / Point SAR frame

For the local SAR calculation, specify the mass in gram over which the SAR should be averaged or choose Point SAR. Typical values are 1 g or 10 g. Use the "custom" option to define any other value.

Calculate

Calculates local and whole-body averaged SAR. The local SAR is added to the 2D/3D Results in the navigation tree. The whole body averaged SAR and other values will be written to the SAR results file and can be accessed via the View results... button.

Specials...

Opens the SAR special settings dialog box.

View results...

Opens the SAR result file for the selected power loss density monitor and averaging mass or the manually set label respectively. This result file can also be viewed by clicking Edit->Info while the SAR field result is selected in the navigation tree. For detailed explanation of the result data, see the SAR Calculation Overview.

Close

Leaves the dialog.

Help

Shows this help text.

SAR Special Settings Dialog Box

Reference Power

The default stimulation power is 1W peak power. Set a user defined power to rescale the results to any RMS power. You may also define accepted power as reference to set directly the power flowing into the structure. Reflection losses at the feeding point thus do not affect the SAR calculation. (The accepted power is equal to the radiated power of an antenna without ohmic losses.). System power values are used if the SAR result has been generated by a circuit simulation.

The proper scaling to a user defined accepted power requires the balance of the excitation. Choose use AR filter results if available to use improved balance values from an AR filter calculation. See the AR-Filter Overview for details.

Averaging method

There are several methods to define an averaging volume which contains the desired averaging mass. The IEEE C95.3 method uses a cube which is grown around the specific point P until it contains the required mass. The cubes are always aligned to the xyz coordinate system. However, if one face of the cube is completely in air, the volume is regarded as invalid and the SAR is taken from the point with the maximum SAR whichs averaging volume contains the point P.

A modification of this method which is called CST C95.3 takes for invalid averaging volumes not the maximum but the closest valid SAR.

IEEE/IEC 62704-1 is an averaging method according to the current dual logo standard draft IEEE/IEC 62704-1 "Draft Recommended Practice for Determining the Peak Spatial-Average Specific Absorption Rate (SAR) in the Human Body from Wireless Communications Devices, 30 MHz - 6 GHz: General Requirements for using the Finite Difference Time Domain (FDTD) Method for SAR Calculations" (Formerly known as IEEE P1528.1). Compared to the IEEE C95.3 method it uses an additional criterion that limits the air volume in valid averaging cubes to 10%.

The CST Legacy method does not take into account the face in air condition but just grows the cube further until the required mass is reached. (Equivalent to CST MWS 2006 and previous versions)

The Constant volume method uses for all points an averaging volume of the same size, defined by averaging mass multiplied with the ratio of total volume to total mass.

Subvolume

You can define a subvolume to be additionally evaluated in the SAR result file by "Use subvolume for statistics" or to save SAR calculation time if you calculate SAR in subvolume only. In the latter case, the SAR field plot will only show nonzero values in the subvolume and there will be no statistics for the total volume in the SAR result file.

To define the XYZmin and XYZmax points you may also use picks before opening the dialog (i.e., two diagonal picked points).