Patent ID: 6810351
Filing Date: 2004-10-26
Classification: G06F

Abstract:
A position detector comprising:a position indicator comprising a resonant circuit which includes at least a coil and a capacitor; a plurality of loop coils which are parallel to position detecting directions; and a tablet for detecting coordinate values of a position indicated by the position indicator on the basis of the levels of reception signals generated at the loop coils when electromagnetic waves at a predetermined frequency are transmitted/received relative to the position indicator; wherein the tablet comprises: transmission/reception control means for consecutively performing transmission/reception of electromagnetic waves relative to the position indicator at least twice while the same loop coil is being selected; phase difference control means for controlling a phase difference of the signals in each of transmission/reception when transmission/reception of electromagnetic waves is consecutively performed at least twice; a synchronous detector circuit for detecting synchronization by using a signal obtained by controlling the phase of the reception signal generated at the loop coil as a detection clock; and signal level processing means for computing the average or the sum of the levels of at least two reception signals which are detected by the synchronous detection and which are based on transmission/reception of electromagnetic waves which is performed at least twice.