Synaptics (uk) Limited

Scientific Generics Limited

David T Ely

Andrew Nicholas Dames

Peter David Cauwood

Gareth John McCaughan

Steven Roland Brace

Ian P Collins

Edward G Colby

Andrew R Howe

An X-Y digitizer system is described for embedding within a host device, such as a tablet PC, a mobile telephone, a personal digital assistant or the like. The digitizer is configurable so that it can detect and track the position of different types of position indicator. The digitizer that is described also includes novel digitizer windings and novel excitation circuitry for energizing the windings.

Digitizer system

A calibration system is provided for use in generating calibration data for calibrating an X-Y digitiser. The calibration system uses an alignment head having an array of magnetic field generators which are for alignment with the X-Y digitiser. Each of the magnetic field generators is individually drivable so that calibration data can be obtained for different positions on the X-Y digitiser corresponding to the positions of the magnetic field generators in the array. The resulting calibration data is then used to generate a correction map which is stored in the X-Y digitiser

Magnetic calibration array

Processing circuitry is provided for processing signals received from, for example, sense coils forming part of a position encoder used to encode the relative positions of two relatively movable members. The position encoder is such that each of the plurality of signals from the sense coils varies sinusoidally with the relative position of the members but out of phase with respect to each other. The processing circuitry comprises mixers for multiplying each of the received signals with one of a corresponding plurality of periodic time varying signals, each having the same predetermined period and a different predetermined phase, and an adder for adding the signals from the mixers. The phase of the mixing signals are chosen so that the output signals from the adder contains a single periodic component having the predetermined period whose phase varies with the relative position of the two members. Preferably, a reference channel is provided in order to allow for compensation of common phase errors in both channels. The period time varying signals multiplied with each of the signals from the position encoder preferably comprise a two or three level square wave signal having a number of transitions designed to reduce the low order harmonic content of the mixing signals.

Signal processing apparatus and method

Processing circuitry is provided for processing signals received from, for example, sense coils forming part of a position encoder used to encode the relative positions of two relatively moveable members. The position encoder is such that each of the plurality of signals from the sense coils varies sinusoidally with the relative position of the members but out of phase with respect to each other. The processing circuitry comprises mixers for multiplying each of the received signals with one of a corresponding plurality of periodic time varying signals, each having the same predetermined period and a different predetermined phase, and an adder for adding the signals from the mixers. The phase of the mixing signals are chosen so that the output signals from the adder contains a single periodic component having the predetermined period whose phase varies with the relative position of the two members. Preferably, a reference channel is provided in order to allow for compensation of common phase errors in both channels. The period time varying signals multiplied with each of the signals from the position encoder preferably comprise a two or three level square wave signal having a number of transitions designed to reduce the low order harmonic content of the mixing signals.

A low cost x-y digitising system is provided for use in consumer electronic devices, such as portable digital assistants, mobile telephones, web browsers and the like. The digitiser includes a resonant stylus, an excitation winding for energising the resonant stylus and a set of sensor windings for sensing the signal generated by the stylus, from which the x-y position of the stylus is determined.

Growing community of inventors

Harston, United Kingdom

David T Ely