| 摘要 |
<p>PURPOSE:To obtain a superior S/N ratio and shorten the time of signal processing by software, and to make a cable relatively long by using a rectangular wave as a carrier for pulses and also using a tuning filter for an amplification part. CONSTITUTION:An X-side carrier switch 13 and a Y-side carrier switch 14 are applied with pulses like A from an oscillator 15 and electrode lines of a tablet 11 are applied with a signal having a waveform like B sequentially by means of the electrode line switching signal of a tablet controller 24. The signal having the waveform like B becomes a detection signal which is close to a sine wave like C at the detection electrode of a stylus pen 18 after electrostatic capacity coupling by removing an external noise by the RC integration circuit of the tablet electrode lines and the capacity of the capacity coupling. When the stylus pen 18 is made to abut on the tablet 11, a signal amplified by an intermediate frequency filter 19 and an amplifier 20 has a waveform like D and then has a waveform corresponding to position information like E through the synchronous detection of a detector 21, and then an amplifier 22 performs differential amplification.</p> |
