Noise reduction in digitizer system
First Claim
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1. A method for noise reduction in a digitizer, the digitizer comprising a plurality of detecting elements for detecting an electromagnetic signal at one of a number of predetermined frequencies comprising:
- sampling at least two elements of said plurality of detecting elements substantially simultaneously to obtain an output signal from each of the at least two detecting elements;
defining a noise signal based on the output signal from one element of the at least two elements, wherein one of said at least two elements is selected as a candidate carrier of stylus signal and the other of said at least two elements is selected as a candidate carrier of mere noise; and
reducing noise on the output signal of the other of the at least two elements in accordance with the noise signal,wherein;
said candidate carrier of mere noise is selected,noise reduction is carried out over a group of elements based on said selection being correct,a resulting signal pattern over said group of elements is analyzed, andsaid selection is allowed if said resulting signal pattern is indicative of a correct selection, otherwise a new selection of candidate carrier of mere noise is made.
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Abstract
A method for noise reduction in a digitizer, the digitizer comprising a plurality of detecting elements for detecting an electromagnetic signal at one of a number of predetermined frequencies: the method comprising: sampling at least two of said detecting elements substantially simultaneously to obtain outputs therefrom, and reducing the output on one of said two elements in accordance with the output on the other of said elements.
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Citations
52 Claims
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1. A method for noise reduction in a digitizer, the digitizer comprising a plurality of detecting elements for detecting an electromagnetic signal at one of a number of predetermined frequencies comprising:
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sampling at least two elements of said plurality of detecting elements substantially simultaneously to obtain an output signal from each of the at least two detecting elements; defining a noise signal based on the output signal from one element of the at least two elements, wherein one of said at least two elements is selected as a candidate carrier of stylus signal and the other of said at least two elements is selected as a candidate carrier of mere noise; and reducing noise on the output signal of the other of the at least two elements in accordance with the noise signal, wherein; said candidate carrier of mere noise is selected, noise reduction is carried out over a group of elements based on said selection being correct, a resulting signal pattern over said group of elements is analyzed, and said selection is allowed if said resulting signal pattern is indicative of a correct selection, otherwise a new selection of candidate carrier of mere noise is made. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. Apparatus for noise reduction in a digitizer, the digitizer comprising a plurality of detecting elements for detecting an electromagnetic signal at one predetermined frequency of a plurality of predetermined frequencies, the apparatus comprising:
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a sampler for sampling at least two elements of the plurality of detecting elements substantially simultaneously to obtain output signals from each of the at least two elements, wherein one of the at least two elements is selected as a candidate carrier of a stylus signal and the other of the at least two elements is selected as a candidate carrier of mere noise; and a noise reduction unit for reducing noise on the output signal on one of said at least two detecting elements in accordance with the output signal on the other of said at least two detecting elements wherein; said candidate carrier of mere noise is selected, noise subtraction is carried out over a group of elements based on the said selection being correct, a resulting signal pattern over said group of elements is analyzed, and said selection is allowed if said resulting signal pattern is indicative of a correct selection, otherwise a new selection of candidate carrier of mere noise is made. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36)
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37. Apparatus for noise reduction in a digitizer, the digitizer comprising a plurality of detecting elements for detecting an electromagnetic signal at one predetermined frequency of a plurality of predetermined frequencies, the apparatus comprising:
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a sampler for sampling at least two elements of said plurality of detecting elements substantially simultaneously to obtain output signals from each of the at least two detecting elements, wherein one of the at least two elements is selected as a candidate carrier of a stylus signal and the other of said at least two elements is selected as a candidate carrier of mere noise; a detector for detecting output signals at each of said at least two elements of said predetermined frequency and another arbitrary frequency; and a noise reduction unit for reducing noise on the output signal on one of said at least two elements in accordance with the output signal on the other of said at least two elements, wherein said noise reduction unit is configured to detect output signals of a plurality of arbitrarily selected frequencies to calculate said reduction and calculating an average ratio in accordance with said output signals of a plurality of arbitrarily selected frequencies to calculate said reduction.
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38. A method for noise reduction in a digitizer, the digitizer comprising a plurality of detecting elements for detecting an electromagnetic signal at one of a number of predetermined frequencies comprising:
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sampling at least two elements of said plurality of detecting elements substantially simultaneously to obtain an output signal from each of the at least two elements, wherein one of said at least two elements is selected as a candidate carrier of a stylus signal and the other of said at least two elements is selected as a candidate carrier of mere noise; detecting signal at each of said at least two elements of said one of the number of predetermined frequencies and of another arbitrary frequency; determining a ratio between signals of the arbitrary frequency at said candidate carrier of mere noise and said candidate carrier of the stylus signal; from said ratio and the signal of the one of the number of predetermined frequencies at the candidate carrier of mere noise, determining an amount of noise of the one of the number of predetermined frequencies at said candidate carrier of the stylus signal; reducing a signal of said one of the number of predetermined frequencies at said candidate carrier of a stylus signal by said determined amount of noise; and reducing the output signal on one of the at least two elements in accordance with the output signal from the other of the at least two detecting elements. - View Dependent Claims (39, 40, 41, 42, 43, 44)
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45. Apparatus for noise reduction in a digitizer, the digitizer comprising a plurality of detecting elements for detecting an electromagnetic signal at one predetermined frequency of a plurality of predetermined frequencies, the apparatus comprising:
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a sampler for sampling at least two elements of said plurality of detecting elements substantially simultaneously to obtain output signals from each of the at least two elements, wherein one of said at least two elements is selected as a candidate carrier of stylus signal and the other of said at least two elements is selected as a candidate carrier of mere noise; a detector for detecting output signals at each of said at least two elements of said predetermined frequency and another arbitrary frequency; a ratio finder for determining a ratio between output signals of the arbitrary frequency at said candidate carrier of mere noise and said candidate carrier of stylus signal; and a noise reduction unit for reducing the output signal on one of said at least two detecting elements in accordance with the output signal on the other of said at least two detecting elements, wherein said noise reduction unit is operable with said ratio finder to; from said ratio and the signal of the predetermined frequency at the candidate carrier of mere noise, determining an amount of noise of the predetermined frequency at said candidate carrier of stylus signal, and reduce the output signal of said predetermined frequency at said candidate carrier of a stylus signal by said amount of noise. - View Dependent Claims (46, 47)
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48. A method for determining a noise signal in a digitizer, the digitizer comprising a plurality of detecting elements for detecting an electromagnetic signal at one of a number of predetermined frequencies, the method comprising:
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sampling at least two elements of said plurality of detecting elements substantially simultaneously to obtain output signals from each of the at least two elements; selecting a first of said at least two elements as a candidate carrier of stylus signal and a second of said at least two elements as a candidate carrier of mere noise; detecting signals at each of said at least two elements of said one of the number of predetermined frequencies and of another arbitrary frequency; determining a ratio between output signals of the arbitrary frequency at said candidate carrier of mere noise and said candidate carrier of stylus signal; and estimating an amount of noise at the predetermined frequency on said candidate carrier of stylus signal from said ratio and the signal of the predetermined frequency at the candidate carrier of mere noise; and defining a noise level on the output signal of the candidate carrier of a stylus signal based on the output signal of the candidate carrier of mere noise. - View Dependent Claims (49, 50, 51, 52)
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Specification