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Multi-phase scanning

  • US 9,285,902 B1
  • Filed: 12/29/2010
  • Issued: 03/15/2016
  • Est. Priority Date: 08/25/2010
  • Status: Active Grant
First Claim
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1. A method, comprising:

  • during each scanning stage, of a plurality of scanning stages, applying a same drive signal to each of a plurality of transmitter electrodes of a touch panel simultaneously for at least a period of time;

    changing phase relations of the same drive signal, applied to each of the plurality of transmitter electrodes, according to the plurality of scanning stages, wherein changing the phase relations comprises;

    applying the same drive signal having a first phase to a first one of the plurality of transmitter electrodes during a first scanning stage of the plurality of scanning stages, wherein the same drive signal has the first phase as an in-phase drive signal;

    during the first scanning stage, applying the same drive signal having a second phase to a second one of the plurality of transmitter electrodes, wherein the same drive signal has the second phase as an opposite phase drive signal;

    selecting a pseudorandom sequence having a number of one and negative one values, wherein a number of values in the pseudorandom sequence is equal to a number of the plurality of transmitter electrodes, wherein the one values correspond to the in-phase drive signal and the negative one values correspond to the opposite phase drive signal;

    applying either the in-phase drive signal or opposite phase drive signal to the plurality of transmitter electrodes according to the pseudorandom sequence;

    rotating the pseudorandom sequence; and

    applying either the in-phase drive signal or opposite phase drive signal to the plurality of transmitter electrodes according to the rotated pseudorandom sequence;

    for each scanning stage, receiving sense signals from a plurality of receiver electrodes, wherein each sense signal represents capacitances of intersections of the plurality of transmitter electrodes and a respective one of the plurality of receiver electrodes; and

    using the phase relations of the same drive signal and the plurality of sense signals to detect a presence of an object on the touch panel.

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