System and method for capacitive sensing

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.

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.