Modeling the Specific Absorption Rate Distribution of a Smartphone

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Brittany Higgins
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1 Application Brief Modeling the Specific Absorption Rate This application models the specific absorption rate (SAR) distribution in a human head, heart and body exposed to an electromagnetic field emitted from a handheld cellular phone operating in GSM (900 MHz and 1,800 MHz) and GPS range in a partially closed environment. In the modeling, SAM Phantom IEEE model and a realistic human head and body are used to investigate both the local and average SAR of 1 g and 10 g tissue. Products ANSYS HFSS, Integral Equation solver (HFSS-IE), ANSYS Optimetrics (optimization features), high-performance computing Keywords SAR, phantom, GSM, GPS Description For a number of years, the general public has been concerned about the possible health effects of exposure to radio frequency (RF) radiation. High levels of RF fields are known to cause a variety of physical effects on the human body. With the dramatic increase in wireless device usage, particularly mobile telephones, R&D teams must ensure that products do not expose users to potentially harmful radiation levels. The known health effects related to the frequencies at which most of these devices operate center around tissue heating. A measure of this heating effect is known as specific absorption rate (SAR), defined as the power absorbed per mass of tissue. Its measure is units of watt per kilogram (W/kg). Usually, SAR is averaged over either the whole body or a small sample volume (typically 1 g or 10 g of tissue). As part of worldwide efforts to regulate consumer health and safety aspects, many authorities require products available in the marketplace to meet SAR limits. Measurement of SAR is, therefore, becoming a fast-growing requirement for companies that make such products. In the United States, the Federal Communications Commission (FCC) has set a SAR limit for the head of 1.6 W/kg, averaged over a volume of 1 gram of tissue. In Europe, the limit is 2 W/kg, averaged over a volume of 10 grams of tissue. SAR values are heavily dependent on the size of the averaging volume. Modeling for such applications is still in development. As a leader and industrial standard setter for electromagnetics solutions, ANSYS offers a 1

2 Figure 1. IEEE SAM phantom model Figure 2. Smartphone model for SAR modeling way to model SAR. ANSYS HFSS (high-frequency structural simulator) software with a unique Integral Solver (HFSS-IE) enables users to solve the complex human body structure in a efficient and robust meshing methodology. Incorporating a high-performance computing (HPC) feature, users can model many iterations of mobile phone placements relative to the human head. This method leads to accurate investigation of SAR distribution with a faster simulation time. Process A smartphone with GSM, GPS and a Bluetooth antenna are built in preparation for modeling the SAR simulation (Figure 1). Human Head Model A SAM phantom IEEE model is created to simulate realistic SAR measurement (Figure 2). The smartphone is placed with a 2 mm gap from the SAM phantom IEEE model, along the skin_guide_brain guideline. All the antennas are powered at W. Figure 3 shows the average SAR radiation plot on the phantom surface averaged over a volume of 1 gram and 10 grams of tissue. The highest Average SAR value for the smart phone model when tested for the use of the phantom model is: GSM GSM GPS Figure 3. SAR over 1 gram (top) and 10 grams (bottom) of tissue for phantom model These readings have meet the SAR limit of 1.6 W/kg for the United States and Canada, averaged over a volume of 1 gram of tissue, for the body or head. They also meet European standards, with the SAR limit of 2 W/kg, averaged over a volume of 10 grams, for the body or head. The next modeling focuses on the realistic human head model. Figure 4 shows a detail human head model with skin, skull and brain together with eye balls and other features. The smartphone is placed with a 2 mm gap from the human head model. Figure 4. Detailed human head model 2

3 Figure 5 shows the average SAR radiation plot on the surface of the human head model for GSM900. It is defined as averaged over a volume of 1 gram and 10 grams of tissue. The SAR radiation 3-D plot of the human skull and brain shows no impact as a result of the phone radiation. Figure 6 shows the average SAR radiation plot on the surface of the human head model for GSM1800. It is as averaged over a volume of 1 gram and 10 grams of tissue. The SAR radiation 3-D plot of the human skull and brain shows no impact as a result of the phone radiation. Figure 5. GSM900 SAR over 1 gram (top) and 10 grams (bottom) of tissue on human head model Figure 7 shows the average SAR radiation plot on the surface of the human head model for GPS. It is defined as averaged over a volume of 1 gram and 10 grams of tissue. The SAR radiation 3-D plot of the human skull and brain shows no impact as a result of the phone radiation. The highest average SAR value for the smartphone model when tested with the human head model is: GSM GSM GPS These readings meet the SAR limit of 1.6 W/kg for the United States and Canada, averaged over a volume of 1 gram of tissue, for the body or head. They also meet European standards, with the SAR limit of 2 W/kg, averaged over a volume of 10 grams, for the body or head. Figure 6. GSM1800 SAR over 1 gram (top) and 10 grams (bottom) of tissue on human head model Figure 7. GPS SAR over 1 gram (top) and 10 grams (bottom) of tissue on human head model 3

4 Human Body Model The next modeling focuses on the realistic full human body model. Figure 8 shows a detailed human body model with heart, lungs and stomach together with intestines and other organs. The smartphone is placed 2 mm away from the wrist of the human body model. Figure x Figure 8. Detailed full human body model Figure 9 shows the average SAR radiation plot on the surface of the human body model for the GSM900. It is defined as averaged over a volume of 1 gram and 10 grams of tissue. The SAR radiation 3-D plot of the detailed human body model with heart, lungs and stomach together with intestines shows no impact as a result of the phone radiation. Figure 10 shows the average SAR radiation plot on the surface of the human body model for GSM1800. It is defined as averaged over a volume of 1 gram and 10 grams of tissue. The SAR radiation 3-D plot of the detailed human body model with heart, lungs and stomach together with intestines shows no impact as a result of the phone radiation. The highest average SAR value for the smartphone model when tested with the human body model is: Figure 9. GSM900 SAR over 1 gram (left) and 10 grams (right) of tissue on human body model GSM GSM GPS These readings meet the SAR limit of 1.6 W/kg for the United States and Canada, averaged over a volume of 1 gram of tissue, for the body or head. They also meet European standards, with the SAR limit of 2 W/kg, averaged over a volume of 10 grams, for the body or head. Figure 10. GSM1800 SAR over 1 gram (left) and 10 grams (right) of tissue on human body model 4

5 Human Heart Model The last model focuses on the realistic full human heart model. Figure 11 shows a detail human body model with heart, lungs, stomach and intestines. The smartphone is placed 2 mm away from the center of the human heart model. Figure 12 shows the average SAR radiation plot on the surface of the human heart model for GSM900, GSM1800 and GSP. It is defined as averaged over a volume of 1 gram of tissue. The SAR radiation 3-D plot of the detailed human heart model shows no impact as a result of the phone radiation. Figure 13 shows the average SAR radiation plot on the surface of the human heart model for GSM900, GSM1800 and GSP. It is defined as averaged over a volume of 10 grams of tissue. The SAR radiation 3-D plot of the detailed human heart model shows no impact as a result of the phone radiation. The highest average SAR value for the smartphone model when tested with the human body model is: Figure 11. Detailed full human heart model GSM GSM GPS These readings meet the SAR limit of 1.6 W/kg for the United States and Canada, averaged over a volume of 1 gram of tissue, for the body or head. They also meet European standards, with the SAR limit of 2 W/kg, averaged over a volume of 10 grams, for the body or head. Figure 12. SAR over 1 gram of tissue on human heart model Figure 13. SAR over 10 grams of tissue on human heart model 5

6 Summary ANSYS provides a way to model SAR distribution in a human head, heart and body exposed to an electromagnetic field emitted from a handheld cellular phone. The solution incorporates the use of the ANSYS HFSS FEM solver, ANSYS Optimetics optimization features and HPC. SAR modeling with the phantom head and detailed human head and body models can be easily solved and analyzed accurately. Compared with physical measurement testing, SAR modeling using ANSYS tools is much more flexible, as users can virtually analyze any of point on the model. Further work can be performed by using the parametrization feature to extract many different placements of the mobile phone at different location on the head and body. Author Desmond Tan haipeng.tan@ansys.com ANSYS, Inc. Southpointe 275 Technology Drive Canonsburg, PA U.S.A ansysinfo@ansys.com Toll Free U.S.A./Canada: Toll Free Mexico: Europe: eu.sales@ansys.com 2012 ANSYS, Inc. All Rights Reserved. 6 ANSYS, Inc. is one of the world s leading engineering simulation software providers. Its technology has enabled customers to predict with accuracy that their product designs will thrive in the real world. The company offers a common platform of fully integrated multiphysics software tools designed to optimize product development processes for a wide range of industries, including aerospace, automotive, civil engineering, consumer products, chemical process, electronics, environmental, healthcare, marine, power, sports and others. Applied to design concept, final-stage testing, validation and trouble-shooting existing designs, software from ANSYS can significantly speed design and development times, reduce costs, and provide insight and understanding into product and process performance. Visit for more information.

Effect of Metallic Materials on SAR

Contemporary Engineering Sciences, Vol. 5, 2012, no. 9, 407-411 Effect of Metallic Materials on SAR Asma Lak Department of Electrical Engineering, Genaveh branch Islamic Azad University, Genaveh, Iran