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
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.