Abstract: An antenna loop structure applicable to a digitizer tablet is capable of reducing effect of electromagnetic interference (EMI) by aggregating a plurality of antenna loops, wherein each antenna loop further comprises a plurality of -shaped segmental antennas, and each pair of immediate neighboring segmental antennas is phase-inverted to each other for counteracting against external EMI.

Abstract: A digitizer tablet comprises a plurality of physical antenna loops distributed along the X- and Y-directions of two-dimensional Cartesian coordinates (X, Y) on the digitizer tablet, wherein each physical antenna loop comprises a plurality of logical sections. For the logical sections of each of the physical antenna loops distributed in the same direction, the adjacent logical sections of the logical sections belong to different physical antenna loops.

Abstract: A digitizer tablet apparatus uses edge areas on the surface of the apparatus as macro cell areas. The location of a pointing device in the apparatus is determined from a plurality of detected magnetic voltages. Threshold values are used to determine if the pointing device is in an edge area. A macro cell in an edge area may be a relative precise macro cell or a coarse macro cell. When a pointing device is in an edge area, the detected voltages may not provide enough data for determining the exact location of the pointing device. If only the exact location in X direction or Y direction can not be determined, the macro cell selected by the pointing device is a relative precise macro cell. If the exact location in both X direction and Y direction can not be determined, the macro cell is a coarse macro cell.

Abstract: An apparatus for automatically changing the operation of a dual-mode digitizer tablet system. The system comprises a cordless pen device generating an electromagnetic wave of a variable frequency and a cordless mouse device generating an electromagnetic wave of a different frequency. The cordless pen device operates in an absolute mode and the cordless mouse device operates in a relative movement mode. The apparatus comprises a detection loop sensing circuit for detecting electromagnetic waves and a signal processing circuit for extracting the signal of either the pen device or the mouse device. The extracted signal is rectified and digitized for determining the position of the cordless pointing device by a micro-controller. A frequency counter determines the frequency of the detected signal. By detecting and determining the frequency of the electromagnetic wave received in the tablet system, the operation mode is adjusted automatically.