CAPACITIVE-BASED TOUCH APPARATUS AND METHOD THEREFOR, WITH REDUCED INTERFERENCE

摘要

A touch-sensitive device that includes a touch surface circuit that facilitates a change in a coupling capacitance in response to a capacitance-altering touches occurring at the touch surface. The device includes a sense circuit that provides a signal, in response thereto, having transient portions for characterizing positive-going transitions towards an upper signal level and negative-going transitions towards a lower signal level. An amplification circuit is then used for amplifying and processing the signals, in response to the time-varying input parameters. The amplification circuit adjusts the gain for the transient portions relative to gain for portions of the response signals between the transient portions, and thereby suppresses RF interference, such as in the form of signal odd and/or even harmonics, to provide a noise filtered output for determining positions of capacitance-altering touches on the touch surface.

主权项

1. A touch-sensitive apparatus, comprising:
a touch surface circuit including a touch surface and a plurality of electrodes, each of the plurality of electrodes being configured and arranged to be associated with a coupling capacitance that changes in response to a capacitance-altering touch at the touch surface; a sense circuit configured to generate response signals for the plurality of electrodes; each of the response signals having an amplitude responsive to the coupling capacitance at the touch surface and including a differentiated signal representation with transient portions characterizing positive-going transitions towards an upper signal level and negative-going transitions towards a lower signal level; and an amplification circuit configured and arranged to provide time-varying parameters for characterizing the transient portions, the amplification circuit including a variable-gain amplifier configured and arranged for processing the differentiated signal representation of the response signals to provide variable gain thereto, in response to the time-varying parameters, the gain being adjusted for the transient portions relative to gain for portions of the response signals between the transient portions, and therein suppressing harmonics in the response signals for providing a noise filtered output that characterizes the associated coupling capacitance for determining positions of touches on the touch surface.