Cochlear implant employing frequency-division multiplexing and frequency modulation

A cochlear prosthesis composed of a transmitter part which is to be carried exterior to the user's body and a receiver part which is to be implanted in the user, the transmitter and receiver parts being coupled by a radio link provided by implanted receiver coils and external transmitter coils free of any percutaneous connections. In the transmitter part, sound signals are obtained in plurality of channels, and these channels are frequency multiplexed into a composite signal with the aid of a plurality of surface acoustic wave filters, each having a respective passband. In the implanted receiver, the received composite signal is frequency demultiplexed by means of a similar plurality of surface acoustic wave filters each having a respective passband. A further signal is transmitted from the transmitter part to the receiver part via the radio link in order to supply operating power for the circuits in the receiver part, where the further signal is rectified to produce d.c. operating voltages.