Abstract: Systems and methods are disclosed for reducing susceptibility of touch screens to RF interference, thereby reducing susceptibility to touch position errors due to RF interference. In touch screen systems having touch sensors that lack a rear shield, the rear shield drive of the controller electronics can be capacitively connected individually to the touch signal drives, thereby placing a capacitive load on the touch signal drives that simulates the capacitive load that would otherwise be provided by a rear shield. This capacitive load compensates for the RF interference, which would otherwise tend to erroneously offset touch position determinations toward the center of the touch screen.

Abstract: The present invention provides systems and methods for detecting stray capacitance in capacitive touch sensors. The existence of stray capacitance can lead to errors in touch detection and touch position determination. Such errors can be avoided or corrected when the stray capacitance is detected. Detecting stray capacitance includes analyzing signals for features characteristic of stray capacitance noise events. Such features can include spatial features such as the location of a test touch position determined from signals caused by stray capacitance, as well as temporal features such as the rate of change of the detected signals.

Abstract: Touch location determination is enhanced by correcting for errors that arise due to touch panel movement. A touch sensitive device includes a capacitive touch sensor configured to generate signals indicative of a location of a capacitively coupled touch on a touch surface. An error correction sensor generates a signal associated with movement of the capacitive touch sensor. Touch location is determined using the touch location signals and the error signal.