Normalizing capacitive sensing measurements to reduce effects of low ground mass and noise

    公开(公告)号:US10540035B2

    公开(公告)日:2020-01-21

    申请号:US15199428

    申请日:2016-06-30

    Abstract: An input device can be capacitive coupled to earth ground and noise sources which can interfere with the ability of the input device to detect an input object. To mitigate the effects from these capacitive couplings, the input device drives a modulated capacitive sensing signal onto a plurality of sensor electrodes in parallel. The sensor electrodes are coupled to respective analog front ends (AFEs) which generate an output signal for each of the sensor electrodes. The input device combines the output signals for the sensor electrodes to generate a normalization value. For example, the output signals may be digital values which are summed by the input device to generate the normalization value. The input device then divides each of the output signals by the normalization value to result in a normalized signal corresponding to each of the sensor electrodes.

    Sensing frame averaging for cancelling display noise in simultaneous display and touch sensing

    公开(公告)号:US09645670B2

    公开(公告)日:2017-05-09

    申请号:US14871473

    申请日:2015-09-30

    CPC classification number: G06F3/0416 G06F3/044 G06F2203/04108

    Abstract: Techniques for removing display-based corrupting components from a capacitive sensing signal when display and capacitive sensing is performed at or nearly at the same time. A routing carrying display related signals (e.g., a source signal for sub-pixel updating) may induce a corrupting current into a routing for carrying capacitive sensing signals. This corrupting current would reduce the ability to determine presence of an input object via the sensing signal. Therefore, the corrupting signal is effectively removed by averaging sensing signals from two consecutive frames together. Because displays perform frame inversion, in which the voltage polarity provided to a sub-pixel for updates is reversed each frame, the corrupting current reverses in polarity each frame. Therefore, adding two subsequent frames together cancels out the corrupting signal.

    Modulating a reference voltage to preform capacitive sensing

    公开(公告)号:US10191597B2

    公开(公告)日:2019-01-29

    申请号:US14788646

    申请日:2015-06-30

    Abstract: This disclosure generally provides an input device modulates a reference voltage used to provide power to a plurality of power supplies and acquires, while modulating the reference voltage, first resulting signals from a plurality of sensor electrodes simultaneously at a central receiver. In input device also acquires second resulting signals from the sensor electrodes at a plurality of local receivers and mitigates an effect a grounding condition has on the second resulting signal using the first resulting signals.

    Differential force and touch sensing

    公开(公告)号:US10073560B2

    公开(公告)日:2018-09-11

    申请号:US15582272

    申请日:2017-04-28

    Abstract: An input device is configured to detect force being applied to an input region of the device by an input object, in addition to the position of the input object using touch sensing methods. Aspects include driving a force sensing electrode of the input device using an anti-guarding voltage alternating with a ground or guard voltage, while driving the touch sensing electrodes with a reference voltage, to obtain touch measurements, force measurements, interference measurements, double the force signal, and/o double the touch signal for differential touch and force detection. Aspects also include driving sensor electrodes using orthogonal signals and performing in-phase and quadrature demodulation of the received signal for simultaneous and independent touch and force measurements.

    Touch noise canceling for dot-inversion driving scheme

    公开(公告)号:US09891774B2

    公开(公告)日:2018-02-13

    申请号:US14986099

    申请日:2015-12-31

    CPC classification number: G06F3/044 G06F3/041 G06F3/0412 G06F3/0418 G09G3/20

    Abstract: Techniques for removing display-based corrupting components from a capacitive sensing signal are provided. A routing carrying display related signals (e.g., a source signal for sub-pixel updating) may induce corrupting current into a routing for carrying capacitive sensing signals. This corrupting current may reduce the ability to determine presence of an input object via the sensing signal. Therefore, the corrupting signal is effectively removed by driving the display elements with a dot inversion technique and by performing capacitive sensing for a sensor electrode during a time in which an even number of display rows are driven for display updates. Dot inversion causes the corrupting current to alternate polarity. Thus, driving sensor electrodes in a period of time in which an even number of rows is driven means that an equal number of positive and negative polarity corrupting currents are induced into the sensing signal.

    Input device having anti-static layer bypass

    公开(公告)号:US09715312B2

    公开(公告)日:2017-07-25

    申请号:US14859771

    申请日:2015-09-21

    Abstract: An input device having an anti-static layer coupled to a grounding element such as a cellphone bottom chassis via a current hindering circuit having a resistive circuit element. Without the current hindering circuit having a resistive circuit element, a large amount of the current from an input object would flow through the connection to the grounding element and would not flow to a receiver channel for processing. This decreases the signal strength within the receiver channel, making sensing more difficult to perform. However, with the current hindering circuit having a resistive circuit element, current is hindered from flowing to ground and thus flows to the receiver channel, thereby increasing the signal strength. The current hindering circuit having a resistive circuit element may be a resistor or a Zener diode that is directed to prevent current flow from the anti-static layer to the grounding element until a significant voltage has built up across the Zener diode.

    Active canceling of display noise in simultaneous display and touch sensing using an impulse response

    公开(公告)号:US10061437B2

    公开(公告)日:2018-08-28

    申请号:US14871448

    申请日:2015-09-30

    CPC classification number: G06F3/0418 G06F3/0412 G06F3/044

    Abstract: Techniques for removing display-based corrupting components from a capacitive sensing signal when display and capacitive sensing is performed at or nearly at the same time. A routing carrying display related signals (e.g., a source signal for sub-pixel updating) may induce a corrupting current into a routing for carrying capacitive sensing signals. This corrupting current would reduce the ability to determine presence of an input object via the sensing signal. Therefore, the corrupting signal is effectively removed from a signal received from a sensor electrode when driven for sensing. The corrupting component may be removed either in analog or digitally. In analog, the corrupting component is removed via a tunable capacitance. Digitally, a corrupting component is calculated as an impulse response convolved with the source driver voltage. This corrupting component is then subtracted from a digital value output by the sensing circuitry to obtain a “clean” value.

    Method and apparatus for improving capacitive sensing detection

    公开(公告)号:US10025428B2

    公开(公告)日:2018-07-17

    申请号:US14946746

    申请日:2015-11-19

    Abstract: Embodiments of the disclosure provided herein provide a device and method of using the device that is able to improve the detection of user input provided to an input device while one or more sources of noise are present during the detection process. One or more of the embodiments disclosed herein may include a scanning process and a signal processing technique that is able to more reliably detect the presence and position of an input object by reducing the effect of noise on a resulting signal that is generated during a capacitive sensing process. In some configurations, the scanning and signal processing techniques disclosed herein can be improved by increasing a capacitive sensing device's ability to detect the presence of an input object by improving the signal-to-noise ratio of the data collected during a capacitive sensing process.

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