US3754233A
Expired / Lapsed
US
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Digital-to-analog conversion apparatus and method
Assignee: Westinghouse Electric Corp
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Filing: 1971-11-19
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Granted: 1973-08-21
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Expires: 1991-11-19
Abstract
Abstract An indirect digital-to-analog conversion apparatus and method which combines the advantages of pulse rate modulation with pulse width or pulse duration modulation. Pulse duration modulation is used on the least significant bits; while pulse rate modulation is used on the more significant bits up to the most significant bit. In this manner, the advantages of both systems are combined resulting in a system in which conversion time is minimized while the ripple content in the analog output is also minimized.
Inventors
- 👤 J Sutherland
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 06:38
CPC Classifications
H; H03; H03M; H03M1/00; H03M1/001
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
142 words
In apparatus for converting electrical signals representing binary digits of a number to an analog electrical signal having a magnitude proportional to the numerical equivalent of said number, the combination of pulse rate modulation digital-toanalog conversion means for converting those bits extending from the most significant bit to an intermediate bit into a first train of pulses whose cumulative widths represent the numerical equivalent of the converted bits, pulse duration modulation digital-to-analog conversion means for converting the remaining bits including the least significant bit into a unitary pulse whose width is representative of the numerical equivalent of said remaining bits, means for injecting said unitary pulse into said train of pulses, and means for extracting the average component from said train of pulses including said injected pulse to derive an analog signal proportional in magnitude to the numerical equivalent of said number.
Claim 2
Dependent Claim
142 words
In apparatus for converting electrical signals representing binary digits of a number to an analog electrical signal having a magnitude proportional to the numerical equivalent of said number, the combination of pulse rate modulation digital-toanalog conversion means for converting those bits extending from the most significant bit to an intermediate bit into a first train of pulses whose cumulative widths represent the numerical equivalent of the converted bits, pulse duration modulation digital-to-analog conversion means for converting the remaining bits including the least significant bit into a unitary pulse whose width is representative of the numerical equivalent of said remaining bits, means for injecting said unitary pulse into said train of pulses, and means for extracting the average component from said train of pulses including said injected pulse to derive an analog signal proportional in magnitude to the numerical equivalent of said number.
Claim 3
Dependent Claim
14 words
The combination as in claim 1 wherein said number is a pure binary number.
Claim 4
Dependent Claim
99 words
The apparatus of claim 1 wherein said pulse train digital-to-analog conversion means includes a pulse rate multiplier driven by clock pulses and having a sampling period corresponding to the time required to feed to the rate multiplier a number of pulses corresponding to the numerical equivalent of the most significant bit fed into the rate multiplier, and wherein said pulse duration digital-to-analog conversion means includes a comparator for comparing ON and OFF digital signals representing bits with the output of a counter, the clock pulses applied to said rate multiplier being generated once during each cycle of said counter.
Claim 5
Dependent Claim
40 words
The apparatus of claim 1 wherein the width of the pulse injected by said pulse duration modulation means is no greater than the width of the pulse produced by the least significant bit fed to said pulse rate modulation means.
Claim 6
Dependent Claim
126 words
The apparatus of claim 1 wherein said means for injecting said unitary pulse into said train of pulses includes a circuit which changes from a first state to a second state in response to the absence of pulses at the output of said pulse rate modulation means and changes from its second to its first state in response to the presence of pulses at the output of said pulse rate modulation means, and including means for causing said circuit to assume its first state at the termination of a sampling period of said pulse rate modulation means and thereafter change to its second state following a time delay which varies as a function of the numerical equivalent of bits applied to said pulse duration modulation means.
Claim 7
Dependent Claim
40 words
The apparatus of claim 5 wherein said last-named means includes a clock pulse generator, a counter driven by said clock pulse generator, and a comparator for comparing the count of said counter with the bits subjected to pulse duration modulation.
Claim 8
Dependent Claim
38 words
The apparatus of claim 6 wherein said comparator acts to cause said circuit to change to its second state when the count of said counter matches or exceeds the numerical equivalent of bits subjected to pulse duration modulation.
Claim 9
Dependent Claim
20 words
The apparatus of claim 1 including a precision switch to which said train of pulses is applied before being averaged.
Claim 10
Independent Claim
126 words
The method of converting electrical signals representing binary digits of a number to an analog electrical signal having a magnitude proportional to the numerical equivalent of said binary number comprising the steps of converting those bits extending from the most significant bit to an intermediate bit into a first train of pulses whose cumulative widths represent the numerical equivalent of the converted bits, converting the remaining bits including the least significant bit into a unitary pulse whose width is representative of the numerical equivalent of said remaining bits, injecting said unitary pulse into said train of pulses, and extracting the average component from said train of pulses including said injected pulse to derive an analog Signal proportional in magnitude to the numerical equivalent of said number.
Claim 11
Independent Claim
126 words
The method of converting electrical signals representing binary digits of a number to an analog electrical signal having a magnitude proportional to the numerical equivalent of said binary number comprising the steps of converting those bits extending from the most significant bit to an intermediate bit into a first train of pulses whose cumulative widths represent the numerical equivalent of the converted bits, converting the remaining bits including the least significant bit into a unitary pulse whose width is representative of the numerical equivalent of said remaining bits, injecting said unitary pulse into said train of pulses, and extracting the average component from said train of pulses including said injected pulse to derive an analog Signal proportional in magnitude to the numerical equivalent of said number.
Claim 12
Dependent Claim
14 words
The combination as in claim 9 wherein said number is a pure binary number.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-08-20 | 1977-02-19 | 1977-08-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-08-20 | 1981-02-19 | 1981-08-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-08-20 | 1985-02-19 | 1985-08-21 | $7700.00 | Window Closed / Lapsed |