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One of my past research topics (during my Under grad days)was on Calulation of SAR distributions on the human head due to Electromagnetic radiations from wireless devices using 3D FDTD.
Specific Absorbtion Rate (SAR) is the measure of heat generated due to EM radiations. The SAR peak values, evaluated over any 1 gr of tissue and for phones radiating 600 mW of power in free space condition, must be less than the ANSI limit of 1.6 W/kg. The human head model was developed from a collection of Magnetic resonance images. This model incorporated 7 different tissues and their electrical characteristics at 835MHz. Why FDTD? Of the three methods of predicting electromagnetic effects -- experiment, analysis, and computation -- computation is the newest and fastest growing. Of the many approaches to electromagnetic computation, the finite difference time domain (FDTD) technique is applicable to the widest range of problems. - Karl Kunz and Raymond Luebbers The FDTD technique was applied to a rectangular wave guide excited in the TE10 mode (by selecting the appropriate frequency for the source sine wave and the dimensions of the waveguide). The output was compared with the theoretical results and were found to be remarkably similar. Click here to see the wave propagating through the waveguide. Later Mur's ABC was studied and was applied to a problem involving an isotropic radiator in the space domain. It was observed that the wave emanating from the point source in the center of the domain was perfectly being absorbed at the boundaries. As a next step a human head model was generated from MRI data and the generated human head model was to be incorporated inside the domain. Click here to view the generated 3d head model. A simple dipole raditor was modeled and excited inside the domain. The 3d fdtd code was later run with the 10° , 20° and 30° tilted head models. From the induced electric field components and the electrical parameters of the tissues SAR calculations were carried out. The results obtained were as follows
And some more SAR distribution patterns in the x=19 planes for 1cms and 2cms separation between the head model and the source. |
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