LOW-POWER CORDLESS MAGNETIC FIELD DIGITIZER BY DIFFERENTIAL GRID DETECTION AND SYNCHRONOUS POSITION DEMODULATION

摘要

PURPOSE: To realize a position digitization with high accuracy and reliability in a pointing device and to provide a digitizer provided with high resistance against noise. ;CONSTITUTION: Magnetic field signals sent by the pointing device 32 are received by the plural data grid conductors 11a and plural clock grid conductors 11B of a tablet 11. A multiplexer 34 selectively connects grid conductor signals with a data channel circuit. A phase locked loop circuit 24 generates reproducing clock signals used as a reference for demodulating the phase and amplitude of signals from the data grid conductors 11A synchronized with the magnetic field signals. The accurate decision of the tip part of a pointer is achieved simultaneously with the accurate decoding of a pointer command indicated by the frequency shifting of the magnetic field signals. Thus, the position digitization with the high accuracy and reliability is realized and a digitizer with high resistance against noise is attained.;COPYRIGHT: (C)1994,JPO