Abstract: A device and method for detecting actual touch points in a multi-touch input device. Embodiments include a measurement sharing device configured to combine a measurement of an electrical characteristic on a first axis with a measurement of an electrical characteristic on a second axis. The combined measurement is compared with electrical characteristics measured separately on each axis to determine which intersections correspond to actual touch points.

Abstract: A device and method for detecting actual touch points in a multi-touch input device. Embodiments include a measurement sharing device configured to combine a measurement of an electrical characteristic on a first axis with a measurement of an electrical characteristic on a second axis. The combined measurement is compared with electrical characteristics measured separately on each axis to determine which intersections correspond to actual touch points.

Abstract: The present invention is a method for demodulating a PSK modulated signal wherein the PSK system incorporates a transmitter generating a PSK modulated signal and wherein the transmitter is crystal based. A crystal based receiver receives the PSK modulated signal and the delta phase between the recovered PSK signal and a receiver generated reference signal is measured; the measurement is repeated with a predetermined phase shift. Voltage values are derived representing the results of each of the measurements and are applied to an analog-to-digital converter to derive digital values representing the two phases measured, and a corresponding delta phase. The digital values are applied to a look up table to derive a phase correction for the reference signal, and several methods are described to perform various types of PSK demodulation.

Abstract: The present invention is a method for demodulating a PSK modulated signal wherein the PSK system incorporates a transmitter generating a PSK modulated signal and wherein the transmitter is crystal based. A crystal based receiver receives the PSK modulated signal and the delta phase between the recovered PSK signal and a receiver generated reference signal is measured; the measurement is repeated with a predetermined phase shift. Voltage values are derived representing the results of each of the measurements and are applied to an analog-to-digital converter to derive digital values representing the two phases measured, and a corresponding delta phase. The digital values are applied to a look up table to derive a phase correction for the reference signal, and several methods are described to perform various types of PSK demodulation.

Abstract: A digitizing system includes a tablet and a cordless pointing device including a plurality of data grid conductors in the tablet and a plurality of clock grid conductors in the tablet, all receiving a magnetic field signal transmitted by the pointing device. A data channel circuit includes a differential amplifier and demodulating and filtering circuitry coupled to an output of the differential amplifier, having a clock input. An A/D converter has an input coupled to an output of the demodulating and filtering circuitry. Multiplexing circuitry selectively couples various grid conductor signals to the data channel circuit. A clock recovery circuit responsive to the clock grid conductors includes a phase-locked-loop circuit that generates a recovered clock signal which is synchronous with the magnetic field signal and is used as a reference for demodulating the phase and amplitude of signals multiplexed from the data grid conductors to the data channel circuit.

Abstract: A digitizing system includes a differential noise reduction technique wherein spaced parallel grid conductors in a tablet are differentially sensed in order to cancel out locally induced noise signals. Grid conductors also are sensed in a single ended fashion to initially locate a grid conductor conducting a larger induced carrier signal amplitude than any other grid conductor and produce amplitude data that is used to eliminate ambiguities arising from differential sensing of pairs of spaced grid conductors.

Abstract: A cordless pen emits a directional electric field from the tip of a conductive pen cartridge. The pen tip is capacitively coupled to embedded major X and major Y conductors in a digitizer tablet, which are scanned to determine which three X conductors and which three Y conductors have the greatest resulting signal levels. A microprocessor calculates the precise pen location from the three largest X signals and the three largest Y signals. A resistive path to ground is provided for each X and Y conductor. A plurality of minor conductors are disposed between each pair of X and Y conductors. A resistive divider circuit linearly distributes the voltage across the pair of conductors among the minor conductors therebetween, and improves the capacitively coupled signal levels and also "localizes" noise signals. The frequency of the pen signal is modulated by several pen switches.