Inductive Powering / Analog Circuits and Signal Processing (PDF)

Inductive powering has been a reliable and simple method for many years to wirelessly power devices over relatively short distances, from a few centimetres to a few feet. Examples are found in biomedical applications, such as cochlear implants; in RFID, such as smart cards for building access control; and in consumer devices, such as electrical toothbrushes. Device sizes shrunk considerably the past decades, demanding accurate design tools to obtain reliable link operation in demanding environments. With smaller coil sizes, the link efficiency drops dramatically to a point where the commonly used calculation methods become invalid.

Inductive Powering: Basic Theory and Application to Biomedical Systems is a complete reference for the inductive link designer. It bundles the information scattered throughout literature into a set of consistent formulations allowing engineers to grasp the calculus in full clarity. A general formalism is given for a wide array of applications, ranging from strong to very weak coil coupling. Without loosing universal applicability, the book then focuses on weak coupling (k < 1%) where the existing approximate formulae fail, and demonstrates that the design of the coil driver must be included in the optimisation flow. It provides step-by-step instructions that boost the performance of links originally confined to some microwatts, to several milliwatts without increasing the dimensions. The book lists all design equations and topology alternatives to successfully build an inductive power and data link for your specific application. It also contains practical guidelines to expand the external driver with a servomechanism that automatically tunes itself to varying coupling and load conditions.