Analysis and Optimization of Spiral Circular Inductive Coupling Link for Bio-Implanted Applications on Air and within Human Tissue

Abstract

The use of wireless communication using inductive links to transfer data and power to implantable microsystems to stimulate and monitor nerves and muscles is increasing. This paper deals with the development of the theoretical analysis and optimization of an inductive link based on coupling and on spiral circular coil geometry. The coil dimensions offer 22 mm of mutual distance in air. However, at 6 mm of distance, the coils offer a power transmission efficiency of 80% in the optimum case and 73% in the worst case via low input impedance, whereas, transmission efficiency is 45% and 32%, respectively, via high input impedance. The simulations were performed in air and with two types of simulated human biological tissues such as dry and wet-skin using a depth of 6 mm. The performance results expound that the combined magnitude of the electric field components surrounding the external coil is approximately 98% of that in air, and for an internal coil, it is approximately 50%, respectively. It can be seen that the gain surrounding coils is almost constant and confirms the omnidirectional pattern associated with such loop antennas which reduces the effect of non-alignment between the two coils. The results also show that the specific absorption rate (SAR) and power loss within the tissue are lower than that of the standard level. Thus, the tissue will not be damaged anymore.

An Efficiency Enhancement Technique for a Wireless Power Transmission System Based on a Multiple Coil Switching Technique

“…In general WPT techniques are classified into three types [1] based on the transmission techniques: (1) the electromagnetic (EM) radiation technique, which transmits microwave energy over long distances and is used for space satellite applications [1]; (2) the inductive coupling technique, which allows the transfer of energy over very short distances and is used in wireless charging applications, such as laptops, mobile phones and biomedical implants [1][2][3][4][5]. For energy harvesting applications, the work presented in [6] depicted long-range energy transfer based on inductive coupling for a distance of 6 m, but the power received was confined to 10.9 mW for a 246-W DC power input.…”

Dynamic Wireless Charging for Roadway-Powered Electric Vehicles: A Comprehensive Analysis and Design

“…C p and C s are the compensated capacitances of the primary and secondary units, respectively. In the secondary unit, the current I s can also be calculated as [16]:…”

“…Then, ω is the operating angular frequency, R L the equivalent resistance of the load, and M the mutual inductance between the track and pickup coil as given by [16]:…”

Design and Simulation of an Integrated Wireless Capacitive Sensors Array for Measuring Ventricular Pressure

“…The electric characteristics of the dual-layer planar coil can be determined by using well known models [56,57,58], where the electrical inductance for a circular multi-layer coil can be calculated as:$\mathrm{normalL}\cong {\mathrm{L}}_1{+\mathrm{normalL}}_2\pm 2\mathrm{normalM}$ where M = k(L 1 ∙L 2 ) 1/2 is the mutual inductance between the two levels of the planar coil [28], k = (R 2 out.T ∙R 2 out.R )/(R 2 out.T ∙R 2 out.R ) 1/2 (R 2 out.T + X 2 ) 3/2 is the coupling factor between the two coils, whereas L 1 and L 2 are the self-inductances for the lower and upper loops, which are determined from the following Equation [49,50,57,59]:${\mathrm{L}}_1{=\mathrm{normalL}}_2\cong \frac{{\mathsf{\mu }}_0{\mathrm{n}}^2{\mathrm{d}}_{\mathrm{avg}}{\mathrm{C}}_1}{2}\left[\ln \left(\frac{{\mathrm{C}}_2}{\mathrm{F}}\right){+\mathrm{normalC}}_3{\mathrm{normalF}+\mathrm{normalC}}_4{\mathrm{F}}^2\right]$ where n = (Rout − Rin)(w + s) is the number of turns of the inductor, davg = (Dout + Din)/2 is the averaged diameter of the windings, F = (Dout − Din)/Dout + Din) is the fill factor of the windings and C1–C4 are constant coefficients determined by the winding geometry [57]. …”