A
system providing an inductive power and
data link between an external
transmitter and miniature internal
receiver is presented. The
system is suited to applications where the
receiver must be of a small size and the
system must consume very little power, such as an implanted biomedical device. The system is also compatible with systems where bi-directional communications are required. The novel
transmitter and
receiver form an improved forward
data telemetry system. The
transmitter consists of a Class-E converter with its optimum
operating frequency being synchronously, instantaneously and efficiently altered in accordance with the data to be transmitted, thereby producing an FSK modulated
magnetic field of substantially constant amplitude. The constant amplitude output allows for the continuous, data-independent transfer of power to the miniature receiver and its associated
electronics. The present invention also represents an improvement over the high efficiency Class-E
converters previously patented by the inventors. The receiver consists of a coil and an integrated rectifying system to recover operating power from the incident
magnetic field, as well as an FSK demodulator whose operation is based on the multiphase comparison of charging times of integrated capacitors. The described FSK demodulator approach removes deleterious effects resulting from low-frequency changes in the transmitter frequency, and eliminates
time distortion artifacts generated by circuit imbalances and asymmetries in the power
recovery process. The combination of the transmitter and receiver improvements yields a reliable data
transfer system unaffected by circuit imbalances and incidental variations in the amplitude and frequency of the
magnetic field.