Active feedforward interference cancellation techniques for sensor analog front-end

A processing system configured to couple to a display panel and to a plurality of sensor electrodes configured to establish a sensing region, the processing system comprising:

• a reference circuit configured to couple to a capacitor via a switching mechanism configured to selectively coupled and decouple the capacitor from the reference circuit, wherein the capacitor capacitively couples the reference circuit to a conductive layer in the display panel, wherein a capacitance value of the capacitor corresponds to a value of a background capacitance formed between a first sensor electrode of the plurality of sensor electrodes and the conductive layer, and wherein the reference circuit comprises:
• an interference circuit comprising a feedback capacitor, the interference circuit is configured to determine a measurement of noise generated by the conductive layer;
• and
• a scaling circuit comprising a first resistor and a second resistor, the scaling circuit is coupled to an output of the interference circuit and is configured to scale the measurement of noise at least partially based on a product of a ratio of a resistance of the first resistor to a resistance of the second resistor and a ratio of the capacitance value of the capacitor to a capacitance value of the feedback capacitor to generate a reference voltage;
• and
• an analog front end (AFE) coupled an output of the scaling circuit, wherein the AFE is configured to couple to the first sensor electrode, and wherein the AFE is configured to generate a capacitive measurement corresponding to the first sensor electrode using the reference voltage.