Position sensor
AssigneeSynaptics (UK) Limited
InventorsDavid Thomas Eliot Ely, Gareth John McCaughan, Geoffrey Foote
Life of this patent
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Abstract
A low cost x-y digitising system is described 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. A novel stylus design is described together with novel digitiser windings and novel excitation and processing circuitry.
Claims38
A frequency determining system comprising:
- a signal generator operable, when energised by an alternating excitation signal, to generate an alternating response signal of predetermined but unknown frequency and whose amplitude varies in dependence upon the difference in frequency between the excitation signal and the response signal;
- an energising circuit operable to generate first and second excitation signals at first and second different excitation frequencies for energising said signal generator;
- a receiver operable to receive a first response signal generated by said signal generator when energised by said first excitation signal and a second response signal generated by said signal generator when energised by said second excitation signal;
- a processing circuit operable to process each of the first and second response signals received by said receiver to generate first and second amplitude measures indicative of the amplitudes of the corresponding response signals;
- and
- a determining circuit operable to determine a frequency measure indicative of the frequency of the alternating response signals generated by said signal generator using said first and second amplitude measures.
A positioning system comprising first and second relatively moveable members,
- the first member comprising a signal generator operable, when energised by an alternating excitation signal, to generate an alternating response signal of predetermined but unknown frequency and whose amplitude varies in dependence upon the difference in frequency between the excitation signal and the response signal;
- and
- the second member comprising:
- an energising circuit operable to generate first and second excitation signals at first and second different excitation frequencies for energising said signal generator;
- a receiver operable to receive a first response signal generated by said signal generator when energised by said first excitation signal and a second response signal generated by said signal generator when energised by said second excitation signal;
- a processing circuit operable to process each of the first and second response signals received by said receiver to generate first and second amplitude measures indicative of the amplitudes of the corresponding response signals;
- a determining circuit operable to determine a frequency measure indicative of the frequency of the alternating response signals generated by said signal generator using said first and second amplitude measures;
- and
- a positioning circuit operable to process at least one of the first and second response signals to determine the relative position between the first and second members.
Dependencies are inferred from the claim text.