Individually addressable multi-touch sensors using a sweep signal for minimal wiring complexity

Abstract

Although touch sensing has been developed rapidly, it is difficult to design a simple circuit or a system that contains many sensors; the number of wires increases in proportion to the number of sensors. Although efforts have been made to reduce the number of wires, multitouch measurements are still challenging because it is difficult to decouple multitouch signals. Here, we apply frequency-division multiplexing to swept frequency capacitive sensing when developing a sensor system capable of multitouch with minimal wiring complexity. The sensor system can be extended in series and arrays by connecting multiple sensors using only two wires. A signal generated via frequency sweeping is expressed as a unique response in a specific frequency domain using a multiband bandstop filter. Considering such unique touch responses, each capacitive multitouch sensor is individually addressable, thereby allowing touch to be detected regardless of sensor location.