Low-noise, high-resolution ratiometric capacitive baseliner

A system comprising:

• a plurality of sensing channels that are coupled with sensing electrodes of a sensing device, wherein a first sensing channel of the plurality of sensing channels comprises an attenuator having a first input coupled with at least one of the sensing electrodes and a second input to receive an excitation sinusoidal signal used to excite the sensing electrodes;
• a global baseliner circuit comprising a signal generator to generate a first density-modulated bit stream and a square wave having a frequency matching that of the excitation sinusoidal signal, the global baseliner circuit to use the square wave to modulate the excitation sinusoidal signal provided at an output of the global baseliner circuit;
• and
• a channel baseliner circuit operatively coupled with the global baseliner circuit and the at least one of the sensing electrodes, the channel baseliner circuit comprising:
• a sigma-delta modulator to receive, as input, a channel baseliner amplitude value associated with the first sensing channel and to generate a second density-modulated bit stream;
• a first switched capacitor coupled between the output of the global baseliner circuit and the first input of the attenuator, the first switched capacitor having a first pair of switches controlled by a first pair of gated clock signals generated by the first density-modulated bit stream;
• and
• a second switched capacitor coupled in parallel with the first switched capacitor, the second switched capacitor having a second pair of switches controlled by a second pair of gated clock signals generated by the second density-modulated bit stream.

A method comprising:

• operating a sensing device comprising a plurality of sensing channels, which includes a first sensing channel comprising an attenuator having a first input coupled with at least one of a plurality of sensing electrodes and a second input to receive an excitation sinusoidal signal, a global baseliner circuit comprising a signal generator, and a channel baseliner circuit comprising a first switched capacitor coupled between an output of the global baseliner and the first input of the attenuator, wherein operating the sensing device comprises:
• generating, using a sigma-delta modulator of the signal generator, a first density-modulated bit stream and a square wave having a frequency matching that of the excitation sinusoidal signal;
• generating, based on the square wave, a modulated excitation sinusoidal signal provided at the output of the global baseliner circuit;
• generating, based on the first density-modulated bit stream, a first pair of gated clock signals that are non-overlapping in phase;
• and
• controlling, using the first pair of gated clock signals, a first pair of switches of the first switched capacitor.