Patent EP0399738A2 successfully refreshed from Google Patents.
EP0399738A2
Expired / Lapsed
EP
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Analogue to digital converter
Assignee: BAE Systems Electronics Ltd
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Filing: 1990-05-18
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Granted: —
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Expires: 2010-05-18
Abstract
Abstract Analogue signals at i/p are converted to digital data at o/p by means of a Sigma-Delta modulator comprising a pair of bandpass filters (H1 (S), H2(S)) consisting of an inductor L and a capacitor C in parallel and a series resistor and a feedback loop including DAC 22. The tendency of such a circuit to instability is reduced or eliminated by making small variations in the phase of the clock 1 controlling the feedback pulses relative to the clock 2 controlling the data output pulses. As an alternative, corrections may be made to the feedback pulses by an additional feedback loop providing pulses for correcting the feedback pulses.
Inventors
- 👤 Andrew Mark Thurston
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 18:08
CPC Classifications
H; H03; H03M; H03M3/00; H03M3/30; H03M3/322; H03M3/324; H03M3/326; H03M3/328; H03M3/3283; H03M3/39; H03M3/402; H03M3/404; H03M3/408; H03M3/412; H03M3/422; H03M3/43; H03M3/436; H03M3/438; H03M3/454
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
113 words
Analogue-to-digital converter comprising bandpass filter means for filtering a signal derived from an analogue input signal, digitising means for producing, at sampling instants, samples at one of a discrete number of values corresponding to a signal derived from the output of the bandpass filter means, a feedback loop feeding a signal derived from the output of the digitising means to the bandpass filter means, the circuit being arranged to produce a minimum in quantisation noise in the passband of the filter means, and in which at least some of the zero crossings of the response of the bandpass filter means to a single fedback pulse are made to coincide with the sampling instants.
Claim 2
Dependent Claim
113 words
Analogue-to-digital converter comprising bandpass filter means for filtering a signal derived from an analogue input signal, digitising means for producing, at sampling instants, samples at one of a discrete number of values corresponding to a signal derived from the output of the bandpass filter means, a feedback loop feeding a signal derived from the output of the digitising means to the bandpass filter means, the circuit being arranged to produce a minimum in quantisation noise in the passband of the filter means, and in which at least some of the zero crossings of the response of the bandpass filter means to a single fedback pulse are made to coincide with the sampling instants.
Claim 3
Dependent Claim
124 words
Analogue-to-digital converter comprising bandpass filter means for filtering a signal derived from an analogue input signal, digitising means for producing, at sampling instants, samples at one of a discrete number of values corresponding to a signal derived from the output of the bandpass filter means, a feedback loop feeding a signal derived from the output of the digitising means to the bandpass filter means, the circuit being arranged to produce a minimum in quantisation noise in the passband of the filter means, in which there is provided means for producing a phase offset between the fedback pulses and the sampling instants of the digitising means to produce a desired response of the bandpass filter means at the sampling instants to a single fedback pulse.
Claim 4
Dependent Claim
124 words
Analogue-to-digital converter comprising bandpass filter means for filtering a signal derived from an analogue input signal, digitising means for producing, at sampling instants, samples at one of a discrete number of values corresponding to a signal derived from the output of the bandpass filter means, a feedback loop feeding a signal derived from the output of the digitising means to the bandpass filter means, the circuit being arranged to produce a minimum in quantisation noise in the passband of the filter means, in which there is provided means for producing a phase offset between the fedback pulses and the sampling instants of the digitising means to produce a desired response of the bandpass filter means at the sampling instants to a single fedback pulse.
Claim 5
Dependent Claim
129 words
Analogue-to-digital converter comprising bandpass filter means for filtering a signal derived from an analogue input signal, digitising means for producing, at sampling instants, samples at one of a discrete number of values corresponding to a signal derived from the output of the bandpass filter means, a feedback loop feeding a signal derived from the output of the digitising means to the bandpass filter means, the circuit being arranged to produce a minimum in quantisation noise in the passband of the filter means, in which there is provided a corrective feedback loop for feeding correction pulses derived from the output of the digitising means to the bandpass filter means in order to produce a desired response of the bandpass filter means at the sampling instants to a single fedback pulse.
Claim 6
Dependent Claim
129 words
Analogue-to-digital converter comprising bandpass filter means for filtering a signal derived from an analogue input signal, digitising means for producing, at sampling instants, samples at one of a discrete number of values corresponding to a signal derived from the output of the bandpass filter means, a feedback loop feeding a signal derived from the output of the digitising means to the bandpass filter means, the circuit being arranged to produce a minimum in quantisation noise in the passband of the filter means, in which there is provided a corrective feedback loop for feeding correction pulses derived from the output of the digitising means to the bandpass filter means in order to produce a desired response of the bandpass filter means at the sampling instants to a single fedback pulse.
Claim 7
Dependent Claim
26 words
Analogue-to-digital converter as claimed in claim 3, in which the correction pulses are delayed by an odd number of sampling periods compared to the feedback pulses.
Claim 8
Dependent Claim
37 words
Analogue-to-digital converter as claimed in any one of claims 1 to 4, in which the feedback pulses are delayed by an even number of sampling periods compared to the samples at the output of the digitising means.
Claim 9
Dependent Claim
24 words
Analogue-to-digital converter as claimed in any one of claims 1 to 5, in which the digitising means produces samples at one of two values.
Claim 10
Dependent Claim
39 words
Analogue-to-digital converter as claimed in claim 6, in which the digitising means is a comparator, the output of which is either a positive signal or a negative signal depending on whether the input is above or below a threshold.
Claim 11
Dependent Claim
20 words
Analogue-to-digital converter as claimed in any one of claims 1 to 7, in which the converter forms a Sigma-Delta modulator.
Claim 12
Dependent Claim
30 words
Analogue-to-digital converter as claimed in any one of claims 1 to 8, in which the bandpass filter means comprise a first stage bandpass filter and a second stage bandpass filter.
Claim 13
Dependent Claim
37 words
Analogue-to-digital converter as claimed in claim 9 as appended to claim 3, in which the corrective loop feeds a signal derived from the output of the digitising means to the input of the second stage bandpass filter.
Claim 14
Dependent Claim
42 words
Analogue-to-digital converter as claimed in any one of claims 1 to 10, in which the bandpass filter means includes an inductor and capacitor in parallel with series resistor, or an inductor and capacitor in series, and together in parallel with a resistor.
Claim 15
Dependent Claim
31 words
Analogue-to-digital converter as claimed in any one of claims 1 to 11, in which the input to the bandpass filter means is a current source and the output is a voltage.
Claim 16
Dependent Claim
35 words
Analogue-to-digital converter as claimed in any one of claims 1 to 12, including an input buffer for converting input analogue signals to a pair of signals, one of which is inverted compared to the other.
Claim 17
Dependent Claim
47 words
Analogue-to-digital converter as claimed in claim 13, in which the feedback loop includes a signal generator for generating a signal corresponding to a signal at the output of the digitising means, and the signal can be combined with either the non-inverting or inverting signal from the buffer.
Claim 18
Dependent Claim
20 words
Analogue-to-digital converter as claimed in any one of claims 1 to 14, in which the feedback loop includes a delay.
References Cited (Backward Citations)
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