Electronic device for recognizing asynchronous digital pen and recognizing method thereof

An electronic device comprising a digital pen, the electronic device comprising:

• at least three reception sensors installed in the electronic device at positions that are separated from one another, the at least three reception sensors configured to receive a waveform generated by a waveform generator of the digital pen;
• and
• a processor configured to determine an input coordinate of the digital pen using a difference of velocities and reception times of the waveform received by each of the at least three reception sensors,
• wherein the processor is configured to determine the input coordinate of the digital pen by calculating a 2-Dimensional (2D) input coordinate of the digital pen using a difference between transfer times of at least two cases of waveforms received by the at least three reception sensors, and
• wherein the input coordinate of the digital pen is calculated using non-linear simultaneous equations comprising:
• 1) d1−d2=[(x−x1)2+(y−y1)2]1/2−[(x−x2)2+(y−y2)2]1/2=Δt12Vs
• 2) d1−d3=[(x−x1)2+(y−y1)2]1/2−[(x−x3)2+(y−y3)2]1/2=Δt13Vs
• where d1, d2, d3 are respective distances from three reception sensors to a currently input position of the digital pen, (x1, y1) is a coordinate of a first reception sensor, (x2, y2) is a coordinate of a second reception sensor, and (x3, y3) is a coordinate of a third reception sensor, Vs is a velocity of an ultrasonic wave set in advance and used for a calculation equation in the electronic device, x and y is a 2D input coordinate of the digital pen to detect, Δt12 is a difference between waveform transfer times received by the first reception sensor and the reception second sensor, and Δt13 is a difference between waveform transfer times received by the first reception sensor and the third reception sensor.