Analysis of a Sheath Helix in Coaxially Multi-Layered Dielectric Environment

Abstract

The EM power deposition in the biological tissue layers (bone/muscle/fat/skin) of rat's thigh/limb placed within a sheath helix in coaxially multilayered dielectric environment has been analyzed theoretically by both field and equivalent circuit approaches. For this, high frequency slow wave assumption has been made. Employing field analysis approach, dispersion relation is obtained by substituting field expressions (in different layers) into forty proper boundary conditions. To solve for the complex propagation constant, an iterative algorithm has been developed by applying Muller's procedure. The complex axial propagation constant, axial depth, and electromagnetic fields inside every tissue layer within each of the three wire helices of radii equal to 0.50, 0.60, and 0.70 cm and respective pitches 0.165, 0.197, and 0.231 cm, are then determined and patterns of specific absorption rate (SAR) at 2.45, 2.70, and 3.00 GHz are computed and presented. The results of an equivalent circuit analysis has also been reported. It is found that the dispersion relation in the absence of dielectric losses, obtained using this approach is identical with that of field analysis. The numerical values of phase and attenuation constants obtained using the two analysis approaches for each of three helices at 2.45, 2.70, and 3.00 GHz are in agreement with each other.

Indexing terms:

• Sheath helix
• Rat's thigh/limb
• Phase and attenuation constant
• SAR
• Equivalent circuit parameters