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.