Learning Forum

[Nooshin Valizade Shahmirzadi]

Hello Support,

I have an antenna and I want to calculate peak spatially-averaged SAR over 1gr of tissue to check this value with the recommended value in safety code documents. I am not using the phantom provided by HFSS. I simply defined and put my lossy mediums in direct contact with my antenna. I have 4 layers, absorber-skin-heterogenous medium (category D)-skin defined in my simulation. I extracted the tangent loss, permittivity and mass density of these mediums based on the literature. The absorber is 10 mm, the skin is 2mm and the heterogenous medium is 52 mm. I want to calculate peak spatially-averaged SAR over 1gr of tissue in the skin and heterogeneous medium.  How should I do it in HFSS?

Does the average SAR on my desired volume (ex. skin layer) correspond to peak spatially-averaged SAR over 1gr of tissue?

or should I define SAR certification? If I have to use SAR certification which option do I have to select in SAR setting: gridless or IEC/IEEE 62704-4? when I chose IEC/IEEE 62704-4 I got this warning and insensible plot:
  [warning] IEC/IEEE 62704-4 peak spatial-average SAR computation did not converge, with a relative error of -0.300127435578155. 

I tried this request for the heterogenous medium (Category D), same thing happened.

I will be grateful if you help me with this calculation and my concerns and questions asked above.

kind regards,

Nooshin

[dushyant.marathe]

Hi Nooshlin,

Thanks for posting your query. HFSS reports the peak spatially averaged SAR depending upon the average SAR method chosen in below SAR settings dialog.

The mass of tissue 1 gram or 10 gram you can specify in SAR settings dialog. SAR calculation involes E field, tissues electric conductivity and mass/material desnity. Please define them appropriately. You can use IEC/IEEE 62704 certifications.

Note that SAR calculation is time consuming and defining a object list where you wish to compute will be helpful.

To calculate certification SAR on a specific object (rather than the whole model) you can use a Field calculator.

The HFSS help PDF descibes the steps in details, please refer it. Also there are two sections in HFSS help PDF titled "Modifying SAR Settings," and 

"Calculating the SAR" that should clarify most of your doubts.

Regarding error I may not be able to comment without investigating and checking the model, if you have a access to Ansys Technical Support please raise a service ticket and Ansys support engineer should help you with it. Thanks,

 

[Nooshin Valizade Shahmirzadi]

Thank you for your reply. I have a couple of questions which arise from your reply. Is peak spatial averaged SAR over 1gr or 10 gr of tissue the value that I have to compare with the value recorded in the safety code or I have to consider the certification SAR through field calculator? I reviewed the HFSS PDF file on SAR calculation however I didn't quite understand which calculation method is the one that I have to use for my comparison.

Moreover, I couldn't still solve my warning issue in certification SAR calculation. I am using (“Academic Research” bundle) through CMC microsystems, so how can I contact your technical support to provide them with my simulation file?

Kind regards,

Nooshin