Abstract: A system for generating an offset signal for a capacitive sensor includes a waveform generator configured to generate a waveform, an R-2R ladder circuit having a constant output resistance that is coupled to an output of the waveform generator and is configured to generate the offset signal based on the waveform, and an adjustable capacitor that is connected between an output of the R-2R ladder circuit and a reference voltage. The capacitive sensor includes one or more sensing electrodes coupled to the waveform generator through a capacitance and is configured to generate a sensed signal by sensing an object. The R-2R ladder circuit and the adjustable capacitor are configured to adjust amplitude and phase of the offset signal such that the amplitude and the phase of the offset signal respectively coincide with an amplitude and a phase of the sensed signal when the sensing electrodes do not sense the object.

Abstract: A system for generating an offset signal for a capacitive sensor includes a waveform generator configured to generate a waveform, an R-2R ladder circuit having a constant output resistance that is coupled to an output of the waveform generator and is configured to generate the offset signal based on the waveform, and an adjustable capacitor that is connected between an output of the R-2R ladder circuit and a reference voltage. The capacitive sensor includes one or more sensing electrodes coupled to the waveform generator through a capacitance and is configured to generate a sensed signal by sensing an object. The R-2R ladder circuit and the adjustable capacitor are configured to adjust amplitude and phase of the offset signal such that the amplitude and the phase of the offset signal respectively coincide with an amplitude and a phase of the sensed signal when the sensing electrodes do not sense the object.

Abstract: A system and method for injecting a signal on a sense electrode in order to increase the security of the touch sensor if signals are capable of being intercepted by a probe, the injected signals being capable of creating a signal on the sense electrode that replicates the signal of an actual finger, creating a signal on a sense electrode that is equal to but opposite of an actual finger in order to cancel out the signal from the actual finger and therefore hide its presence, and create a pseudo random signal on sense electrodes so that it is difficult to correlate measurable signals on sense electrodes to actual finger position.

Abstract: A system and method for injecting a signal on a sense electrode in order to increase the security of the touch sensor if signals are capable of being intercepted by a probe, the injected signals being capable of creating a signal on the sense electrode that replicates the signal of an actual finger, creating a signal on a sense electrode that is equal to but opposite of an actual finger in order to cancel out the signal from the actual finger and therefore hide its presence, and create a pseudo random signal on sense electrodes so that it is difficult to correlate measurable signals on sense electrodes to actual finger position.

Abstract: A system and method for reducing the power required for a capacitive sensing measurement and for simplifying a sample capacitor signal offset while reducing charge injection during synchronous rectification by enabling the touch sensor to begin a measurement cycle at an arbitrary voltage rather than forcing the touch sensor to have a precise known voltage.