System and method for capacitive sensing

1. A method of driving and sensing for a capacitive sensing device, comprising:

transmitting a stimulation signal to a driving channel of the capacitive sensing device, wherein the stimulation signal includes a plurality of sub-stimulation signals, each of the sub-stimulation signals is characterized by an amplitude and a frequency, and the frequencies of the sub-stimulation signals are orthogonal, wherein the transmitting of the stimulation signal includes combining the sub-stimulation signals into a first signal that has a lower frequency than the stimulation signal and converting the first signal to the stimulation signal;

receiving a charge signal from a sensing channel of the capacitive sensing device, wherein the charge signal is generated from the stimulation signal through a capacitance between the driving channel and the sensing channel;

detecting, from the charge signal, a plurality of sub-charge signal amplitudes at the frequencies of the sub-stimulation signals; and

reporting a value about the capacitance from the sub-charge signal amplitudes.

2. The method of claim 1 , wherein the reporting of the value about the capacitance includes:

checking the sub-charge signal amplitudes for corruption; and

upon a condition in which a corrupted sub-charge signal amplitude is found, giving it less weight than the ones of the sub-charge signal amplitudes that are not corrupted.

3. The method of claim 2 , wherein the checking of the sub-charge signal amplitudes for corruption is based on correlation among the amplitudes of the sub-stimulation signals.

4. The method of claim 1 , wherein the amplitudes of the sub-stimulation signals are the same.

5. The method of claim 1 , wherein the amplitudes of the sub-stimulation signals form a subset of a random sequence.

6. The method of claim 1 , wherein the amplitudes of the sub-stimulation signals form a subset of an error-correcting code.

7. The method of claim 6 , wherein the error-correcting code is a Hadamard code.

8. The method of claim 1 , wherein the amplitudes of the sub-stimulation signals form a subset of a Zadoff-Chu sequence.

9. The method of claim 1 , wherein the detecting of the plurality of sub-charge signal amplitudes is performed at the same frequencies and phases as the sub-stimulation signals.

10. The method of claim 1 , wherein the detecting of the plurality of sub-charge signal amplitudes is performed at the same frequencies as the sub-stimulation signals but with different phases.

11. A method of driving and sensing for a capacitive sensing device, comprising:

generating a plurality of stimulation signals, wherein each of the stimulation signals includes a plurality of sub-stimulation signals, each of the sub-stimulation signals is characterized by an amplitude and a frequency, and the frequencies of all the sub-stimulation signals are orthogonal, wherein the generating of the stimulation signals includes, for each of the stimulation signals, combining the respective sub-stimulation signals into a first signal that has a lower frequency than the stimulation signal and up-converting the first signal to the stimulation signal;

transmitting the stimulation signals to a plurality of driving channels of the capacitive sensing device, wherein each one of the stimulation signals corresponds to each one of the driving channels;

receiving a charge signal from a sensing channel of the capacitive sensing device, wherein the charge signal is generated from the stimulation signals through capacitances between the driving channels and the sensing channel;

detecting, from the charge signal, a plurality of sub-charge signal amplitudes at the frequencies of the sub-stimulation signals; and

reporting values about the capacitances from the sub-charge signal amplitudes.

12. The method of claim 11 , wherein the stimulation signals each have the same number of sub-stimulation signals.

13. The method of claim 11 , wherein at least two of the stimulation signals have different numbers of sub-stimulation signals.

14. The method of claim 11 , wherein the amplitudes of the sub-stimulation signals are the same.

15. The method of claim 11 , wherein the amplitudes of the sub-stimulation signals form a subset of: a random sequence, an error-correcting code, or a Zadoff-Chu sequence.

16. The method of claim 11 , wherein the reporting of the values about the capacitances includes:

checking the sub-charge signal amplitudes for corruption; and

upon a condition in which a corrupted sub-charge signal amplitude is found, giving it less weight than the ones of the sub-charge signal amplitudes that are not corrupted.

17. A system of driving and sensing for a capacitive sensing device, comprising:

a driving module, adapted to transmit a stimulation signal to a driving channel of the capacitive sensing device, wherein the stimulation signal includes a plurality of sub-stimulation signals, each of the sub-stimulation signals is characterized by an amplitude and a frequency, the frequencies of the sub-stimulation signals are orthogonal, and the sub-stimulation signals are transmitted to the driving channel simultaneously; and

a receiving module, adapted to perform:

receiving a charge signal from a sensing channel of the capacitive sensing device wherein the charge signal is generated from the stimulation signal through a capacitance between the driving channel and the sensing channel;

detecting, from the charge signal, a plurality of sub-charge signal amplitudes at the frequencies of the sub-stimulation signals; and

reporting a value about the capacitance from the sub-charge signal amplitudes, wherein the driving module includes:

a code generator, adapted to generate a plurality of codes;

a modulator, adapted to modulate a plurality of orthogonal frequencies with the plurality of codes so as to generate the sub-stimulation signals;

a mixer, adapted to combine the sub-stimulation signals into a first signal that has a lower frequency than the stimulation signal; and

an up-converter, adapted to convert the first signal to the stimulation signal.

18. The system of claim 17 , wherein the receiving module includes:

a down-converter, adapted to convert the charge signal to a second signal that has a lower frequency than the charge signal;

a de-modulator, adapted to detect the plurality of sub-charge signal amplitudes from the second signal; and

a decision unit, adapted to calculate the value about the capacitance from the sub-charge signal amplitudes.

19. The system of claim 18 , wherein:

the de-modulator includes a plurality of match filter decoders at the orthogonal frequencies.