US3694581A
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Digital slope threshold data compressor
Assignee: National Aeronautics and Space Administration
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Filing: 1971-05-13
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Granted: 1972-09-26
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Expires: 1991-05-13
Abstract
Abstract Apparatus is disclosed for data compression by a decreasing slope threshold test using digital techniques in which the data stream through an input register is examined and only those samples of the raw data are selected for transmission which have a first difference (slope) that exceeds an exponentially decaying threshold function relative to a bias. If a sample is transmitted, it becomes the new bias and a generator of the threshold function is reset. For threshold comparison, the bias is first subtracted from each first difference to produce a second difference for direct comparison of its absolute value with the absolute value of the threshold function, thereby allowing the function generator to run from a constant reference to generate a single sided exponentially decaying function.
Inventors
- 👤 Tage O Anderson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 14:59
CPC Classifications
H; H03; H03H; H03H17/00; H03H17/02; H03H17/06; H03H17/0621; H03H17/0635; H03H17/065; H03H17/0664
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
331 words
Apparatus for compression of a data stream of periodic samples of a variable signal in digital form to be transmitted through a telemetering system buffer comprising: means for generating a train of pulses synchronized with said data stream, one pulse for each sample of data; first and second storage means responsive to said train of pulses for receiving said data stream in cascade whereby said first storage means holds a given sample fn while said second storage means holds a preceding sample fn 1, where the subscript n is a notation indicating the sample is the nth one in a series; first subtracting means connected to said first and second storage means for subtracting said sample fn 1 in said second storage means from said sample fn in said first storage means to thereby produce in digital form a first difference; third storage means for receiving and storing a bias value in digital form; second subtracting means connected to said first subtracting means and said third storage means for subtracting said bias value from said first difference to thereby produce in digital form a second difference; fourth and fifth storage means responsive to said train of pulses for receiving each successive first and second difference in digital form, respectively; means for producing a predetermined decaying function in digital form; means for continually comparing values of said function with successive second difference values in said fifth storage means, and for producing a control signal when a second difference value exceeds a contemporaneous value of said function; sixth storage means responsive to said train of pulses for translating successive samples of said data stream to said system buffer from said second storage means; and transfer control means responsive to said control signal and said train of pulses for causing a contemporaneous sample in said sixth storage means to be entered into said system buffer, and for causing a contemporaneous first difference to be entered into said third storage means as a bias value.
Claim 2
Dependent Claim
331 words
Apparatus for compression of a data stream of periodic samples of a variable signal in digital form to be transmitted through a telemetering system buffer comprising: means for generating a train of pulses synchronized with said data stream, one pulse for each sample of data; first and second storage means responsive to said train of pulses for receiving said data stream in cascade whereby said first storage means holds a given sample fn while said second storage means holds a preceding sample fn 1, where the subscript n is a notation indicating the sample is the nth one in a series; first subtracting means connected to said first and second storage means for subtracting said sample fn 1 in said second storage means from said sample fn in said first storage means to thereby produce in digital form a first difference; third storage means for receiving and storing a bias value in digital form; second subtracting means connected to said first subtracting means and said third storage means for subtracting said bias value from said first difference to thereby produce in digital form a second difference; fourth and fifth storage means responsive to said train of pulses for receiving each successive first and second difference in digital form, respectively; means for producing a predetermined decaying function in digital form; means for continually comparing values of said function with successive second difference values in said fifth storage means, and for producing a control signal when a second difference value exceeds a contemporaneous value of said function; sixth storage means responsive to said train of pulses for translating successive samples of said data stream to said system buffer from said second storage means; and transfer control means responsive to said control signal and said train of pulses for causing a contemporaneous sample in said sixth storage means to be entered into said system buffer, and for causing a contemporaneous first difference to be entered into said third storage means as a bias value.
Claim 3
Dependent Claim
104 words
Apparatus as defined by claim 1 including: timing means for providing an index number in digital form representing lapsed time following a sample selected for entry into said system buffer; and means responsive to said transfer control means for entering the content of said counting means into said system buffer while simultaneously causing said contemporaneous sample in said sixth storage means to be entered into said system buffer and resetting said timing means, thereby providing to said system buffer a number associateD with a sample entered into said system buffer, said number indicating lapsed time from a preceding sample entered into said system buffer.
Claim 4
Dependent Claim
290 words
Apparatus for compression of data to be transmitted through a system buffer using a decreasing-slope threshold test comprising: means for converting a continuously varying input signal into a data stream of periodic samples in digital form; first, second and output registers connected in cascade to receive said data stream in digital form, whereby said first register holds a given sample fn while said second register holds a preceding sample fn 1, where the subscript n is a notation indicating the sample is the nth one in a series, and said output register holds said sample fn 1 during a succeeding sample period; first subtracting means connected to said first and second registers for subtracting said sample fn 1 in said second register from said sample fn in said first register to thereby produce in digital form a first difference; a third register for holding a bias value in digital form; second subtracting means connected to said first subtracting means and said third register for subtracting said bias value from said first difference to thereby produce in digital form a second difference; a fourth register for holding each successive first difference produced in digital form by said first subtracting means; a fifth register for holding each successive second difference produced in digital form by said second subtracting means; means for producing a unipolar function having successive periodic values in digital form decaying from a predetermined starting value; means for comparing each successive second difference with the current value of said function, and for producing a control signal when a second difference exceeds a contemporaneous value of said function; and means responsive to said control signal for causing a contemporaneous sample in said output register to be transferred into said system buffer.
Claim 5
Dependent Claim
290 words
Apparatus for compression of data to be transmitted through a system buffer using a decreasing-slope threshold test comprising: means for converting a continuously varying input signal into a data stream of periodic samples in digital form; first, second and output registers connected in cascade to receive said data stream in digital form, whereby said first register holds a given sample fn while said second register holds a preceding sample fn 1, where the subscript n is a notation indicating the sample is the nth one in a series, and said output register holds said sample fn 1 during a succeeding sample period; first subtracting means connected to said first and second registers for subtracting said sample fn 1 in said second register from said sample fn in said first register to thereby produce in digital form a first difference; a third register for holding a bias value in digital form; second subtracting means connected to said first subtracting means and said third register for subtracting said bias value from said first difference to thereby produce in digital form a second difference; a fourth register for holding each successive first difference produced in digital form by said first subtracting means; a fifth register for holding each successive second difference produced in digital form by said second subtracting means; means for producing a unipolar function having successive periodic values in digital form decaying from a predetermined starting value; means for comparing each successive second difference with the current value of said function, and for producing a control signal when a second difference exceeds a contemporaneous value of said function; and means responsive to said control signal for causing a contemporaneous sample in said output register to be transferred into said system buffer.
Claim 6
Dependent Claim
103 words
Apparatus as defined by claim 1 including: a source of clock pulses; means for counting said clock pulses to provide an index number in digital form representing lapsed time between successive samples selected for transfer into said system buffer in response to said control signal; and means responsive to said control signal for entering the content of said counting means into said system buffer while simultaneously resetting said counting means to zero, thereby providing to said system buffer a number associated with a sample entered into said system buffer, said number indicating lapsed time from a preceding sample entered into said system buffer.
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) | 1975-09-26 | 1976-03-27 | 1976-09-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-09-26 | 1980-03-27 | 1980-09-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-09-26 | 1984-03-27 | 1984-09-26 | $7700.00 | Window Closed / Lapsed |