Theoretical studies of the SAR in biological models have been of increasing interest in recent years. The analyses started with simple geometrical models, such as homogeneous planar and spherical models. More complicated numerical methods have now been used, and calculations are available for inhomogeneous realistic models of man.
In general the SAR depends on body shape, frequency, polarization, E and H vector fields, presence of ground plane and reflectors, and dielectric composition. The shape of the model basically dictates the appropriate expansion functions to be used in an analytical solution. Frequency, on the other hand, determines the method of solution. Other factors, such as excitation and layering, can be included by extending the appropriate technique.
In Table 5.5 we summarize the theoretical techniques used to calculate the SAR in models of man and animals. The table is divided into three basic divisions according to how complex the model's shape is. The one-dimensional models are the simplest and are particularly useful at higher frequencies where the body curvature can be neglected. Such models, however, cannot predict body resonance that occurs in three-dimensional models. The two dimensional models are basically single or multilayered cylindrical geometries suitable to simulate limbs. The three-dimensional case includes models of idealized shapes, such as spheres, spheroids, and ellipsoids, as well as more realistic block models of man.

Table 5.5
Comparison of Theoretical Methods Used In Literature to Calculate The Power Absorption by Biological Models

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Last modified: June 14, 1997
October 1986, USAF School of Aerospace Medicine, Aerospace Medical Division (AFSC), Brooks Air Force Base, TX 78235-5301