DESIGN OF SPIRAL CIRCULAR COILS IN WET AND DRY TISSUE FOR BIO-IMPLANTED MICRO-SYSTEM APPLICATIONS

Abstract

This paper deals with the design of small-sized bio- implanted spiral circular coils (pancake) with an operating frequency of 13.56MHz. The external and internal coils' geometric dimensions are dout = 56mm, din = 10mm and dout = 11:6mm, din = 5mm, respectively, in which the electrical performance is verifled through the commercial fleld solver High Frequency Structural Simulator (HFSS 13.0), which employs the flnite-element method (FEM) technique. Mathematical models for the proposed coils are developed. The simulation is performed-based on the developmental model in the air and at depths 6mm in a human biological tissue of dry and wet skin. The results demonstrate that the external and internal coils have maximum near-fleld gains of 54.15dB and 53.30dB in air. The maximum gains of the external coil contacted the wet and dry skin are 49.80dB and 48.95dB, respectively. The maximum gains of the internal coil at depths of 6mm in the wet and dry tissue are 41.80dB and 41.40dB, respectively. However, the external coil radiation e-ciencies on wet- and dry-skin are 92% and 90%, respectively, compared with that on air. The internal coil radiation e-ciencies on wet- and dry-skin are 78.4% and 77.6%, respectively, compared with that on air. In this study, the speciflc absorption rate (SAR) and radiated power results of the internal coil are investigated using SEMCAD 16.4 software. The SAR and power loss studies show that the designed implanted coil has a negligible efiect on the wet and dry skin and can be ignored.