Patent ID: 8564553

Claim:
An apparatus for touch input, comprising: a capacitive touchpad module actively driving a plurality of traces with a charging/discharging signal, the capacitive touchpad module including a detection circuit connected to the plurality of traces for detecting the charging/discharging signal conducted by the plurality of traces and sensing a touch input responsive to a capacitive coupling to the capacitive touchpad module changing an amplitude of the charging/discharging signal input to the detection circuit from at least two orthogonal traces of the plurality of traces, the detection circuit generating an excitation signal to have a fixed relationship with respect to a phase and a frequency of the charging/discharging signal; and an electronic stylus coupled to the detection circuit for receiving the excitation signal therefrom, the electronic stylus including a longitudinally extended housing, a conductive tip disposed at one end of the housing and an insulator disposed between the conductive tip and the housing to provide electrical isolation therebetween, the excitation signal being output from the conductive tip, the excitation signal being capacitively coupled to the least two orthogonal traces of the plurality of traces of the capacitive touchpad module near a touch point when the tip of the electronic stylus touches the capacitive touchpad module, the capacitive coupling of the excitation signal to the at least two orthogonal traces altering the amplitude of the charging/discharging signal to thereby simulate the touch input by a user's finger.