US3796868A
Expired / Lapsed
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Variable threshold digital correlator
Assignee: International Telecommunications Satellite Organization
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Filing: 1972-08-11
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Granted: 1974-03-12
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Expires: 1992-08-11
Abstract
Abstract A digital code word correlator for detecting a unique code word in a serially received data stream. The correlator includes a digital adder tree producing a binary number representing the number of matches between the bits of the received word and the bits of a stored replica of the expected unique word. The binary number is supplied to true and complement variable threshold digital comparators which generate detection signals in response to predetermined numbers of matches.
Inventors
- 👤 P Kaul
- 👤 W Gaunt
- 👤 H Ford
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 14:24
CPC Classifications
G; G06; G06F; G06F17/00; G06F17/10; G06F17/15
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
115 words
A digital code word correlator comprising: bit by bit comparison means for comparing a first digital word with a second digital word on a bit by bit basis and providing a number of output signals equal to the number of matches between said first and second digital words, a digital adder tree responsive to said number of output signals for generating a binary number representing the number of matches between the bits of the first digital word and the corresponding bits of the second digital word, and a variable threshold digital comparator means responsive to said binary number for producing a detection signal indicating the state of correspondence between the first and second digital words.
Claim 2
Dependent Claim
115 words
A digital code word correlator comprising: bit by bit comparison means for comparing a first digital word with a second digital word on a bit by bit basis and providing a number of output signals equal to the number of matches between said first and second digital words, a digital adder tree responsive to said number of output signals for generating a binary number representing the number of matches between the bits of the first digital word and the corresponding bits of the second digital word, and a variable threshold digital comparator means responsive to said binary number for producing a detection signal indicating the state of correspondence between the first and second digital words.
Claim 3
Dependent Claim
64 words
The digital code word correlator of claim 1 wherein said bit by bit comparison means comprises a shift register for storing said first digital word, each stage of said shift register having a true and complement output, and a plurality of switch means one coupled to each register stage selectively connecting either the true or complement output of each stage to said adder tree.
Claim 4
Dependent Claim
68 words
The digital code word correlator of claim 1 wherein said adder tree comprises a plurality of rows of digital adders arranged so that each row consolidates the output bits from the preceeding row, the first row being coupled to said comparing means whereby the bits from the last row represent a binary number indicating the number of matches between corresponding bits of the first and second digital words.
Claim 5
Dependent Claim
33 words
The digital code word correlator of claim 3 wherein each adder of said adder tree in the first three rows of adders is comprised of an exclusive OR circuit and an AND circuit.
Claim 6
Dependent Claim
28 words
The digital code word correlator of claim 4 wherein said adder tree further includes latch means for equalizing the delay experienced by bits flowing through the adder tree.
Claim 7
Dependent Claim
61 words
The digital code word correlator of claim 5 wherein said variable threshold digital comparator produces a detection signal indicating effective correspondence between said first and second digital words, further including another variable threshold digital comparator responsive to said binary number for producing a detection signal indicating that said first digital code word is the complement of said second digital code word.
Claim 8
Dependent Claim
124 words
A digital code word correlator comprising: means for receiving a data stream, means for storing an n-bit word forming a portion of said data stream, means for comparing the stored n-bit word with a unique word on a bit by bit basis, the result of said comparison being represented by comparison bits, a multilevel digital adder tree responsive to said comparison bits for producing a binary number representing the number of matches between the bits of said stored word and the corresponding bits of the unique word, and a variable threshold digital comparator having a preset threshold level and being responsive to said binary number for producing a detection signal when the binary number is equal to or greater than the preset threshold level.
Claim 9
Dependent Claim
124 words
A digital code word correlator comprising: means for receiving a data stream, means for storing an n-bit word forming a portion of said data stream, means for comparing the stored n-bit word with a unique word on a bit by bit basis, the result of said comparison being represented by comparison bits, a multilevel digital adder tree responsive to said comparison bits for producing a binary number representing the number of matches between the bits of said stored word and the corresponding bits of the unique word, and a variable threshold digital comparator having a preset threshold level and being responsive to said binary number for producing a detection signal when the binary number is equal to or greater than the preset threshold level.
Claim 10
Dependent Claim
44 words
The digital code word correlator of claim 7 further including another variable threshold digital comparator having a preset threshold level and being responsive to said binary number for producing another detection signal when the binary number is equal to less than its threshold level.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-03-11 | 1977-09-10 | 1978-03-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-03-11 | 1981-09-10 | 1982-03-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-03-11 | 1985-09-10 | 1986-03-12 | $7700.00 | Window Closed / Lapsed |