Wideband Capacitive Sensing Using Sense Signal Modulation

A system for capacitive sensing, comprising:

• at least one sense capacitor;
• a wideband capacitance to digital converter (WCDC) including at least one output node coupled to a bottom terminal of the at least one sense capacitor, and an input node coupled to a top terminal of the sense capacitor, including
• carrier generation circuitry to generate a carrier signal at a carrier frequency;
• reference circuitry to generate a reference signal;
• carrier/drive signal path circuitry to generate a carrier/drive signal for output from the at least one output node to the at least one sense capacitor, including:
• modulation circuitry to modulate the reference signal with the carrier signal at a carrier frequency to generate the carrier/drive signal at the carrier frequency, and
• drive circuitry to drive the carrier/drive signal out through the at least one output node,
• wherein, in response to the carrier/drive signal, the at least one sense capacitor provides an up-modulated sense capacitance signal, corresponding to measured capacitance and up-modulated to the carrier frequency;
• sense signal path circuitry to receive at the input node the up-modulated sense capacitance signal, including:
• amplifier circuitry to generate an amplified up-modulated sense capacitance signal, and
• demodulation circuitry to demodulate the amplified up-modulated sense capacitance signal using the carrier signal, generating a demodulated sense capacitance signal;
• and
• data conversion circuitry to convert the demodulated sense capacitance signal to sensor data corresponding to measured capacitance, the data converter referenced by the reference signal.

A method for capacitive sensing adaptable to a capacitive sensing system that includes at least one sense capacitor, comprising

• generating a carrier signal at a carrier frequency;
• generating a reference signal;
• in a carrier/drive signal path, generating a carrier/drive signal for output to the at least one sense capacitor, including:
• modulating the reference signal with the carrier signal to generate the carrier/drive signal at the carrier frequency, and
• driving the carrier/drive signal out to the at least one sense capacitor to generate at least one up-modulated sense capacitance signal, corresponding to measured capacitance and up-modulated to the carrier frequency;
• and
• in a sense signal path, receiving the sense capacitance signal corresponding to measured capacitance from the at least one sense capacitor, the sense capacitance signal up-modulated to the carrier frequency by the carrier/drive signal, and:
• amplifying the up-modulated sense capacitance signal, and
• demodulating the amplified up-modulated sense capacitance signal using the carrier signal, generating a demodulated sense capacitance signal;
• and
• converting the demodulated sense capacitance signal to sensor data corresponding to the sense capacitance signal from the at least one sense capacitor.