US5055846A
Expired / Lapsed
US
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Method for tone avoidance in delta-sigma converters
Assignee: Cirrus Logic Inc
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Filing: 1990-12-05
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Granted: 1991-10-08
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Expires: 2010-12-05
Abstract
Abstract The quantization noise in a delta-sigma converter can produce correlated noise when the converter is operating. This correlated noise can produce tones in the frequency band of interest. In a departure from conventional wisdom these tones are substantially eliminated by the degration of the signal-to-noise ratio at the input of the comparator in the delta-sigma converter. In the preferred embodiment this degradation of the signal-to-noise ratio is accomplished by attenuating the input signal to the comparator such that the input signal becomes comparable to the noise generated in the input stage of the comparator.
Inventors
- 👤 David R. Welland
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 00:38
CPC Classifications
H; H03; H03M; H03M3/00; H03M3/30; H03M3/39; H03M3/436; H03M3/438; H03M3/44; H03M3/442; H03M3/412; H03M3/422; H03M3/43; H03M3/446; H03M3/448; H03M3/452
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
64 words
In a delta-sigma converter, the improvement comprising: limiting the maximum signal-to-noise ratio at a node in said delta-sigma converter by, at least in part, attenuating the signal level at said node such that during normal operation the noise level is sufficient to significantly reduce tones in the frequency band of interest which result from the correlation of the quantization noise in said delta-sigma converter.
Claim 2
Dependent Claim
64 words
In a delta-sigma converter, the improvement comprising: limiting the maximum signal-to-noise ratio at a node in said delta-sigma converter by, at least in part, attenuating the signal level at said node such that during normal operation the noise level is sufficient to significantly reduce tones in the frequency band of interest which result from the correlation of the quantization noise in said delta-sigma converter.
Claim 3
Dependent Claim
23 words
The improvement set forth in claim 1 wherein said node is the signal input node to a quantization circuit in said delta-sigma converter.
Claim 4
Dependent Claim
37 words
The improvement set forth in claim 1 wherein the attenuating the signal level at said node is caused, at least in part, by the addition of a capacitive element coupled between said node and a reference potential.
Claim 5
Dependent Claim
17 words
The improvement set forth in claim 1 wherein the maximum signal-to-noise ratio is approximately 40 to 1.
Claim 6
Dependent Claim
58 words
In a delta-sigma converter, the improvement comprising: limiting the maximum signal-to-noise ratio at a node in said delta-sigma converter by injecting noise into said node such that during normal operation the noise level is sufficient to significantly reduce tones in the frequency band of interest which result from the correlation of the quantization noise in said delta-sigma converter.
Claim 7
Dependent Claim
58 words
In a delta-sigma converter, the improvement comprising: limiting the maximum signal-to-noise ratio at a node in said delta-sigma converter by injecting noise into said node such that during normal operation the noise level is sufficient to significantly reduce tones in the frequency band of interest which result from the correlation of the quantization noise in said delta-sigma converter.
Claim 8
Dependent Claim
23 words
The improvement set forth in claim 5 wherein said node is the signal input node to a quantization circuit in said delta-sigma converter.
Claim 9
Dependent Claim
58 words
In a delta-sigma converter having a feedback loop the improvement comprising: limiting the signal-to-noise ratio at a node inside of the feedback loop of said delta-sigma converter by attenuating the signal level at said node such that the signal-to-noise ratio at said node is generally never greater than 100 to 1 during normal operation of said delta-sigma converter.
Claim 10
Dependent Claim
58 words
In a delta-sigma converter having a feedback loop the improvement comprising: limiting the signal-to-noise ratio at a node inside of the feedback loop of said delta-sigma converter by attenuating the signal level at said node such that the signal-to-noise ratio at said node is generally never greater than 100 to 1 during normal operation of said delta-sigma converter.
Claim 11
Dependent Claim
51 words
In a delta-sigma converter having a feedback loop the improvement comprising: limiting the maximum signal-to-noise ratio at a node inside of the feedback loop of said delta-sigma converter by limiting the signal level at said node to be generally never greater than 100 millivolts during normal operation of said delta-sigma converter.
Claim 12
Dependent Claim
51 words
In a delta-sigma converter having a feedback loop the improvement comprising: limiting the maximum signal-to-noise ratio at a node inside of the feedback loop of said delta-sigma converter by limiting the signal level at said node to be generally never greater than 100 millivolts during normal operation of said delta-sigma converter.
Claim 13
Dependent Claim
79 words
A delta-sigma converter comprising: a) a plurality of integrators coupled together to form a series charge transfer path; b) a like plurality of feedforward elements, each forming a charge transfer path between an output of one of said plurality of integrators and a summing node, wherein each of said feedforward elements comprises a capacitor in series with said charge transfer path of said feedforward elements; and c) a shunt capacitor coupled between said summing node and a reference voltage.
Claim 14
Dependent Claim
79 words
A delta-sigma converter comprising: a) a plurality of integrators coupled together to form a series charge transfer path; b) a like plurality of feedforward elements, each forming a charge transfer path between an output of one of said plurality of integrators and a summing node, wherein each of said feedforward elements comprises a capacitor in series with said charge transfer path of said feedforward elements; and c) a shunt capacitor coupled between said summing node and a reference voltage.
Claim 15
Dependent Claim
58 words
In a delta-sigma converter having a feedback loop the improvement comprising: limiting the signal-to-noise ratio at a node inside of the feedback loop of said delta-sigma converter by attenuating the signal level at said node such that the signal-to-noise ratio at said node is generally never greater than 40 to 1 during normal operation of said delta-sigma converter.
Claim 16
Dependent Claim
58 words
In a delta-sigma converter having a feedback loop the improvement comprising: limiting the signal-to-noise ratio at a node inside of the feedback loop of said delta-sigma converter by attenuating the signal level at said node such that the signal-to-noise ratio at said node is generally never greater than 40 to 1 during normal operation of said delta-sigma converter.
Claim 17
Dependent Claim
63 words
In a delta-sigma converter, the improvement comprising: limiting the maximum signal-to-noise ratio at a node in said delta-sigma converter by, at least in part, increasing the noise into said node such that during normal operation the noise level is sufficient to significantly reduce tones in the frequency band of interest which result from the correlation of the quantization noise in said delta-sigma converter.
Claim 18
Dependent Claim
63 words
In a delta-sigma converter, the improvement comprising: limiting the maximum signal-to-noise ratio at a node in said delta-sigma converter by, at least in part, increasing the noise into said node such that during normal operation the noise level is sufficient to significantly reduce tones in the frequency band of interest which result from the correlation of the quantization noise in said delta-sigma converter.
Claim 19
Dependent Claim
22 words
The improvement set forth in claim 11 wherein said delta-sigma converter includes a comparator having an input stage which includes said node.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-10-07 | 1995-04-08 | 1995-10-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-10-07 | 1999-04-08 | 1999-10-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-10-07 | 2003-04-08 | 2003-10-08 | $7700.00 | Window Closed / Lapsed |