A Fast Simulation Methodology for Touch Sensor Panels: Formulation and Experimental Validation

Abstract

This paper presents a novel approach for fast and efficient touch sensor panel modeling, combining electroquasistatic simulation with SPICE type circuit simulation and also presents a method of experimental validation. Touch sensor panel properties are governed by the mutual and self-capacitances of their traces, some of which are affected by touch. It will be shown that all relevant capacitances can be captured by electroquasistatic simulation of a small panel section and extrapolated for a larger size panel. Utilizing these capacitances, equivalent circuits for arbitrary size touch sensor panels, with and without touch, are extracted for simulation in any measurement or operational environment. As an application, derivation of an aggregate capacitance between two panel traces is performed utilizing the equivalent circuits. This parameter is readily measurable, providing a method of validation for simulation results. Its rate of change also provides a measure of the touch response of the panel. Simulation results for the rate of change of the aggregate capacitance are presented and compared to measurement.