Capacitive sensing active electromagnetic emission cancellation
AssigneeSynaptics Incorporated
InventorRobert J. Bolender
Life of this patent
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Abstract
An input device is disclosed that provides reduced electromagnetic emissions while detecting the presence of an input object. In one embodiment, a first set of sensor electrodes is driven with a first modulated signal while a second set of sensor electrodes is driven with a second set of modulated signals that is based on an inverted first modulated signal. The first set of sensor electrodes may determine a capacitance value while the second set of sensor electrodes may reduce electromagnetic emissions associated with the first set of sensor electrodes.
Claims19
A method of capacitive sensing using an array of sensor electrodes, comprising:
- driving, during a first time period, a first set of the sensor electrodes with a first modulated signal;
- generating a second modulated signal based at least in part on an inversion of the first modulated signal;
- driving, during the first time period, a second set of the sensor electrodes with the second modulated signal to reduce electromagnetic emissions associated with the first set of the sensor electrodes;
- driving, during a second time period, at least the second set of the sensor electrodes with the first modulated signal;
- driving, during the second time period, at least a first subset of the sensor electrodes in the first set with the second modulated signal;
- and
- determining, during the first time period, a first capacitance value associated with the first set of the sensor electrodes.
An input device comprising:
- an array of sensor electrodes comprising:
- a first set of sensor electrodes;
- and
- a second set of sensor electrodes;
- and
- a processing system configured to:
- drive, during a first time period, the first set of the sensor electrodes with a first modulated signal;
- generate a second modulated signal based at least in part on an inversion of the first modulated signal;
- drive, during the first time period, the second set of the sensor electrodes with the second modulated signal to reduce electromagnetic emissions associated with the first set of the sensor electrodes;
- drive, during a second time period, at least the second set of the sensor electrodes with the first modulated signal;
- drive, during the second time period, at least a first subset of the sensor electrodes in the first set with the second modulated signal;
- and
- determine, during the first time period, a first capacitance value associated with the first set of the sensor electrodes.
A processing system comprising:
- means for driving, during a first time period, a first set of sensor electrodes with a first modulated signal;
- means for generating a second modulated signal based at least in part on an inversion of the first modulated signal;
- means for driving, during the first time period, a second set of sensor electrodes with the second modulated signal to reduce electromagnetic emissions associated with the first set of the sensor electrodes;
- means for driving, during a second time period, at least the second set of the sensor electrodes with the first modulated signal;
- means for driving, during the second time period, at least a first subset of the sensor electrodes in the first set with the second modulated signal;
- and
- means for determining, during the first time period, a first capacitance value associated with the first set of the sensor electrodes.
Dependencies are inferred from the claim text.