Planar Elliptical Inductor Design for Wireless Implantable Medical Devices

Area of Science:

• Biomedical Engineering
• Electrical Engineering
• Materials Science

Background:

• Wireless implantable medical devices (WIMDs) are advancing disease understanding and patient care through remote data collection.
• Inductive coupling is a key communication method for battery-free WIMDs, relying on magnetically coupled inductors.
• Standard inductor shapes (circular, square, hexagonal, octagonal) are common, but elliptical shapes may suit narrow implantable locations.

Purpose of the Study:

• To develop a numerical model for elliptical planar inductors.
• To enable calculation of inductance and parasitic components for WIMD design.
• To provide an accurate analytical method for optimizing elliptical inductor parameters.

Main Methods:

• Utilized an area transformation technique to derive elliptical inductor formulas from circular ones.
• Developed a numerical model incorporating current sheet expression and area transformation.
• Fabricated and measured over 75 elliptical planar inductors for experimental validation.

Main Results:

• The proposed model accurately estimates elliptical planar inductor inductance and parasitic components.
• Experimental validation showed a mean error of <5% and a standard deviation of <3.18% between measured and modeled parameters.
• The model is validated for various inductor designs (turns, trace width/separation, diameters).

Conclusions:

• The developed numerical model offers an accurate and efficient method for designing elliptical planar inductors for WIMDs.
• Elliptical inductors are suitable for WIMDs requiring communication in confined anatomical regions.
• This technology can enhance wireless implants for monitoring physiological signals from narrow sites.