Analysis of the Susceptibility of Capacitive Touchscreens to External Electric Field Interference

Since the introduction of the iPhone, the touchscreen has become one of the most important human-machine interfaces between users and electronic products. The capacitive touch screen is the most popular touchscreen on the market because of its benefits over a resistive touchscreen. However, since the capacitive touchscreen senses the finger-touch by sensing the capacitance change, it is subjected to the interference of the external electric field, which results in touchscreen malfunction and security issues. This paper will first analyze the working principle of the capacitive touchscreen. The mechanism of false (ghost) touch due to external electric field is explored based on the working principle. The conditions of false touch due to the external electric field will be identified and studied. Experiments are conducted to validate and quantify the analysis above. Different from existing literature, which mostly focuses on demonstrating the results without fully understanding the detail mechanism, this paper focuses on disclosing the fundamentals and identifying critical conditions behind the ghost touch phenomena, which is the major contribution of this paper.