Patent ID: 8278572

Claim:
An electromagnetic induction handwriting system, comprising; a stylus; a handwriting device; an x-y loop antenna array arranged inside of said handwriting device; a switch circuit; a coordinate computation circuit; an analog/digital (A/D) converter; a microprocessor; and a computer; wherein said microprocessor instructs specific antennas of said x-y loop antenna array by switching said switch circuit to detect electromagnetic wave radiated from said stylus, the detection voltages are stored and compared with one another to obtain a first voltage, a second voltage, and a third voltage the coordinate computation circuit employs an arithmetic equation to compute a coordinate of the stylus, the computed coordinate is transmitted to analog/digital (A/D) converter to convert to digital values, and said microprocessor processes the digital coordinate values then transmitting it to said computer; and wherein the arithmetic equation is derived from the first voltage, the second voltage, and the third voltage, in which the first voltage equals the maximum detection voltage, the second voltage and the third voltage are obtained from two antennas, and both of the two antennas are arranged at the same side of the antenna that induces the maximum detection voltage.