| 摘要 |
<p>PURPOSE:To remove noise components almost completely by finding a difference signal between two adjacent parallel electrode lines on a tablet. CONSTITUTION:A sine wave generator 1 in a detection pen 5 generates a continuous sine wave voltage and applies an unbalanced signal voltage based upon an outer peripheral conductor 4 to a stylus conductor 3 at the tip part. The continuous sine wave signal generated in the detection pen 5 is sent to respective electrode lines 7 by electrostatic capacitive coupling through an equivalent ground impedance 13 as a signal return path while having levels corresponding to the values of coupling capacitors. Then Xdirectional and Y-directional analog multiplexers 8 and 9 sequentially switch adjacent two electrode lines among the respective electrode lines 7 in paires and apply two unbalanced signals of the two adjacent electrode lines to the '+' terminal and '-' terminal of a differential amplifier 10 at the same time. The differential amplifier 10 amplifies only the difference between the two signal inputs based upon a ground potential as a reference level. Therefore, disturbing mixed components are removed almost completely and only a necessary signal (signal components from detection pen 5) are reinforced and outputted.</p> |
