EP0274841A2
Expired / Lapsed
EP
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Processing quadrature signals
Assignee: Renishaw PLC
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Filing: 1987-11-26
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Granted: —
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Expires: 2007-11-26
Abstract
Abstract Quadrature input signals (26,28) from an opto-electronic or magnetic readhead (20) which is movable relative to a periodically marked scale (22), are respectively multiplied by quadrature reference signals from a reference oscillator (32) in multipliers (52,54). The resulting signals are added together in a mixer (56) to give a signal (S) which is at a frequency which is the reference frequency shifted by the frequency of the input signals. This signal (S) is then compared with the reference signal. The reference signals are generated from a high frequency clock (30) which is subsequently used to compare the period of the reference signal with that of the signal (S), giving outputs which interpolate the position of the readhead (20) within the pitch of the marks on the scale (22).
Inventors
- 👤 Colin Keith Howley
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 16:10
CPC Classifications
G; G01; G01D; G01D5/00; G01D5/12; G01D5/244; G01D5/248; G01P; G01P13/00; G01P13/02; G01P13/04; G01P13/045
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
119 words
A device for processing input signals which are in quadrature, comprising: a reference oscillator (32) for generating at least one first, reference signal having a reference frequency, and frequency shift means (52,54,56) for generating, from the quadrature input signals and the reference signal(s), a second signal (S) which has a frequency being that of the reference signal, frequency shifted by the frequency of the input signals, characterised by means (60-100) for comparing the length of a period related to the period of the second signal with the length of a reference period related to the period of the reference frequency, and producing an output as a result of the comparison which relates to a parameter of the input signals.
Claim 2
Independent Claim
119 words
A device for processing input signals which are in quadrature, comprising: a reference oscillator (32) for generating at least one first, reference signal having a reference frequency, and frequency shift means (52,54,56) for generating, from the quadrature input signals and the reference signal(s), a second signal (S) which has a frequency being that of the reference signal, frequency shifted by the frequency of the input signals, characterised by means (60-100) for comparing the length of a period related to the period of the second signal with the length of a reference period related to the period of the reference frequency, and producing an output as a result of the comparison which relates to a parameter of the input signals.
Claim 3
Dependent Claim
64 words
A device according to claim 1, including a signal generator (30) which generates a third signal (CK) at a higher frequency than the reference frequency but synchronised with the reference frequency so that there are a predetermined number of periods of the third signal in one period of the reference frequency, the third signal being used by the comparing means to perform said comparison.
Claim 4
Dependent Claim
20 words
A device according to claim 2 in which the reference oscillator (32) generates the reference signal(s) from the third signal.
Claim 5
Dependent Claim
59 words
A device according to claim 2 or claim 3 in which the comparing means includes means (60-72;60,76-92) for determining the number of periods of the third signal (CK) by which the period of the second signal (S) differs from the period of the reference frequency, and for producing a said output in dependence on the result of the determination.
Claim 6
Dependent Claim
26 words
A device according to claim 4 in which the determining means includes a counter (66;76,78) for counting said predetermined number of periods of the third signal.
Claim 7
Dependent Claim
63 words
A device according to claim 5, in which the counter (66) counts said predetermined number of periods in a continuous cycle, and the determining means includes means (62,64) for latching the output value of the counter at a predetermined point in each of two successive cycles of the second signal, and means (72) for subtracting one said latched output value from the other.
Claim 8
Dependent Claim
64 words
A device according to claim 5 in which the counter (76,78) commences counting said predetermined number of periods at a predetermined point in one cycle of the second signal, and in which the determining means determines the number of periods of the third signal occurring between the end of the count and a corresponding predetermined point in the next cycle of the second signal.
Claim 9
Independent Claim
42 words
A device according to any one of claims 4 to 7, in which the said output is used to address a memory (112) containing a map of errors in the said output, and a corrected output signal is derived from the memory.
Claim 10
Independent Claim
41 words
A device according to any one of the preceding claims, in which the input signals are derived from a readhead (20) movable over a periodically marked scale (22), and the said output provides position interpolation within the pitch of the scale.
Claim 11
Independent Claim
24 words
A device according to any one of the preceding claims which produces a said output which relates to the frequency of the input signals.
References Cited (Backward Citations)
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