Signal processing for cochlear implants

1. A method for cochlear implant signal processing, comprising:

processing a differential analog audio signal using amplitude modulation and pulse-width modulation;

driving a transmission coil on an external unit of the cochlear implant with the pulse-width and amplitude modulated signal; and

driving a reception coil on an internal unit of the cochlear implant with an output of the transmission coil.

2. The method of claim 1 , wherein the method includes driving a tuned circuit including the transmission coil with the pulse-width and amplitude modulated signal such that the transmission coil resonates at a frequency approximately equal to a frequency of the first signal.

3. The method of claim 1 , wherein the method includes driving an electrode with the reception coil according to the output of the transmission coil.

4. The method of claim 3 , wherein driving the electrode includes outputting an analog amplitude modulated signal from the reception coil to the electrode.

5. The method of claim 1 , wherein the method includes feeding the pulse-width and amplitude modulated signal back to set a direct current level for modulating the differential analog audio signal.

6. The method of claim 1 , wherein the method includes receiving the differential analog audio signal from a microphone on the external unit of the cochlear implant.

7. The method of claim 1 , wherein processing the differential analog audio signal using amplitude modulation and pulse-width modulation includes processing the differential analog audio signal to generate a reduced-carrier amplitude modulated signal, wherein the reduced-carrier amplitude modulated signal has a carrier level reduced below a carrier level associated with an amplitude modulator for the differential analog audio signal.

8. The method of claim 7 , wherein the method includes delivering the reduced-carrier amplitude modulated signal directly to a cochlea associated with the cochlear implant.

9. An external signal processing unit of a cochlear implant, comprising:

a microphone;

a processor coupled to the microphone including an amplitude modulation circuit and a pulse-width modulation circuit, wherein the processor is configured to process a differential analog audio signal; and

a tuned circuit coupled to the amplitude modulation circuit and to the pulse-width modulation circuit, wherein the tuned circuit is configured to transmit a signal corresponding to a pulse-width and amplitude modulated signal.

10. The external unit of claim 9 , wherein the amplitude modulation circuit includes:

an oscillator configured to generate a carrier signal; and

an analog switch having inputs including:

the differential analog audio signal; and

the carrier signal;

wherein the analog switch is configured to:

modulate the carrier signal with the differential analog audio signal; and

output the modulated signal to the pulse-width modulation circuit.

11. The external unit of claim 10 , wherein the pulse-width modulation circuit includes a comparator with inputs including:

an output of a sawtooth wave generator; and

the output from the amplitude modulation circuit.

12. The external unit of claim 11 , wherein an output of the pulse-width modulation circuit is fed back to mix with the differential analog audio signal input to the analog switch.

13. The external unit of claim 9 , wherein the pulse-width modulation circuit includes at least two comparators, each with an input from a complimentary signal of the differential analog audio signal and an input from a sawtooth generator.

14. The external unit of claim 13 , wherein the amplitude modulation circuit comprises a digital multiplexer with inputs from the at least two comparators and an output to the tuned circuit.

15. The external unit of claim 9 , wherein the tuned circuit is tuned to a frequency approximately equal to a frequency of a carrier signal associated with the amplitude modulation circuit; and

wherein the tuned circuit includes a capacitor, a transmission coil, and a resistor coupled in series.

16. The external unit of claim 9 , wherein the external unit includes at least one battery configured to provide power to the amplitude modulation circuit and the pulse-width modulation circuit.