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Method and apparatus for using oscillation signals with different phases to detect capacitance values at capacitive sensing nodes of touch panel

  • US 8,890,840 B2
  • Filed: 12/18/2012
  • Issued: 11/18/2014
  • Est. Priority Date: 04/30/2012
  • Status: Active Grant
First Claim
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1. A method for detecting capacitance values of a plurality of capacitive sensing nodes located at intersections of a plurality of drive lines and a sense line on a touch panel, comprising:

  • obtaining a plurality of touch sense signals corresponding to the sense line during a plurality of time slots, respectively;

    demodulating the touch sense signals with a first oscillation signal to generate a plurality of first demodulated signals;

    demodulating the touch sense signals with a second oscillation signal to generate a plurality of second demodulated signals, wherein the second oscillation signal is different from the first oscillation signal; and

    determining the capacitance values according to at least the first demodulated signals and the second demodulated signals;

    wherein each touch sense signal is obtained when the drive lines are simultaneously driven by a plurality of stimulation signals;

    during the time slots, stimulation signals are generated according to a common modulation carrier and a plurality of sign values defined in an encoding matrix; and

    the step of determining the capacitance values according to at least the first demodulated signals and the second demodulated signals comprises;

    performing matrix multiplication according to a decoding matrix and the first demodulated signals, and accordingly generating a plurality of first matrix elements, wherein the decoding matrix is an inverse of the encoding matrix;

    performing matrix multiplication according to the decoding matrix and the second demodulated signals, and accordingly generating a plurality of second matrix elements; and

    determining each capacitance value by calculating a root sum square (RSS) value of each pair of one first matrix element and one second matrix element.

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