Individually Addressable Multitouch 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 numbers of wires increase in proportion to the number of sensors. Although efforts have been made to reduce the number of wires, multi-touch measurements are still challenging because it is difficult to decouple multi-touch signals. Here, we apply FDM (Frequency Division Multiplexing) to SFCS (Swept Frequency Capacitive Sensing) when developing a sensor system capable of multi-touch 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 multi-band band-stop filter. Considering such unique touch responses, each capacitive multi-touch sensor is individually addressable, thereby allowing touch to be detected regardless of sensor location.