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US3707680A
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Digital differential pulse code modulation system
Assignee: Comsat Corp
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Filing: 1970-05-20
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Granted: 1972-12-26
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Expires: 1990-05-20
Abstract
Abstract Apparatus and method are disclosed for a differential pulse code modulated system. The system transmits the difference between a given sample of the input signal and an estimated value of the given sample which is determined from previous estimated samples. The differential signal is fed back to an all digital loop to provide an estimated sample without undue delay.
Inventors
- 👤 O Gene Gabbard
- 👤 Pradman Kaul
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 23:36
CPC Classifications
H; H04; H04N; H04N19/00; H04N19/50; H04N19/593; H03; H03M; H03M7/00; H03M7/30; H03M7/3002; H03M7/3044; H03M7/3046
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
97 words
A method of converting successive identifying digital code words, wherein each digital code word is n-bit length and wherein said identifying digital code words represent an analog signal, into second digital code words representative of said analog signal, comprising the steps of: a. storing a reference digital code word; b. digitally comparing an identifying digital code word with said reference digital code word and generating an output digital code word representative of the difference between said identifying aNd reference digital code words; and c. altering said reference digital code word with said generated difference digital code word.
Claim 2
Independent Claim
97 words
A method of converting successive identifying digital code words, wherein each digital code word is n-bit length and wherein said identifying digital code words represent an analog signal, into second digital code words representative of said analog signal, comprising the steps of: a. storing a reference digital code word; b. digitally comparing an identifying digital code word with said reference digital code word and generating an output digital code word representative of the difference between said identifying aNd reference digital code words; and c. altering said reference digital code word with said generated difference digital code word.
Claim 3
Dependent Claim
33 words
The method of claim 1 wherein the step of comparing and generating comprises subtracting said reference digital code word from said identifying digital code word to obtain an n-bit difference digital code word.
Claim 4
Dependent Claim
115 words
The method of claim 2 further comprising the steps of: a. generating a first digital code word of n-x bit length representing a pre determined magnitude if the difference obtained by said subtraction is positive and greater than said predetermined magnitude; b. generating a second digital code word of n-x bit length representing said predetermined magnitude if the difference obtained by said subtraction is negative and greater than said predetermined magnitude; and c. generating a third digital code word of n-14 x bit length representing the actual difference if the difference is a magnitude less than said predetermined magnitude, wherein x the number of most significant bits truncated from the n-bit difference digital code word.
Claim 5
Dependent Claim
35 words
The method of claim 3 wherein the step of altering comprises digitally adding said difference digital code word to said reference digital code word and storing the result as a new reference digital code word.
Claim 6
Dependent Claim
107 words
In a differential pulse code modulation transmission system wherein a digital code word representing a difference between a present analog sample and a previous analog sample is transmitted, the method of reconstructing the present analog sample, at a receiver, comprising the steps of: a. storing a reference digital code word representative of said previous analog sample; b. digitally combining said stored reference digital code word with said difference digital code word to provide a new reference digital code word; c. storing said new reference digital code word; and d. converting said new reference digital code word into an analog signal whereby said present analog signal is reconstructed.
Claim 7
Dependent Claim
107 words
In a differential pulse code modulation transmission system wherein a digital code word representing a difference between a present analog sample and a previous analog sample is transmitted, the method of reconstructing the present analog sample, at a receiver, comprising the steps of: a. storing a reference digital code word representative of said previous analog sample; b. digitally combining said stored reference digital code word with said difference digital code word to provide a new reference digital code word; c. storing said new reference digital code word; and d. converting said new reference digital code word into an analog signal whereby said present analog signal is reconstructed.
Claim 8
Dependent Claim
26 words
The method of claim 5 wherein the step of combining comprises digitally adding adding said stored reference digital code word to said difference digital code word.
Claim 9
Dependent Claim
160 words
In a differential pulse code modulation transmission system wherein a difference digital code word of n-bit length representing the difference between a present analog sample and a previous analog sample is generated and wherein a difference digital code word of n-x bit length is transmitted, wherein x the number of most significant bits truncated from said n-bit difference digital code word, the method of reconstructing the present analog sample, at a receiver, comprising the steps of: a. storing a reference digital code word representing said previous analog sample; b. reconverting said difference digital code word of n-x bit length to the difference digital code word of n-bit length; c. digitally adding said stored reference digital code word with said reconverted difference digital code word to provide a new reference digital code word; d. storing said new reference digital code word; and e. converting said new reference digital code word into an analog signal, whereby said present analog signal is reconstructed.
Claim 10
Dependent Claim
160 words
In a differential pulse code modulation transmission system wherein a difference digital code word of n-bit length representing the difference between a present analog sample and a previous analog sample is generated and wherein a difference digital code word of n-x bit length is transmitted, wherein x the number of most significant bits truncated from said n-bit difference digital code word, the method of reconstructing the present analog sample, at a receiver, comprising the steps of: a. storing a reference digital code word representing said previous analog sample; b. reconverting said difference digital code word of n-x bit length to the difference digital code word of n-bit length; c. digitally adding said stored reference digital code word with said reconverted difference digital code word to provide a new reference digital code word; d. storing said new reference digital code word; and e. converting said new reference digital code word into an analog signal, whereby said present analog signal is reconstructed.
Claim 11
Dependent Claim
104 words
Apparatus for converting successive identifying digital code words, wherein each digital code word is n-bit length and wherein said identifying digital code words represent an analog signal, into second digital code words representative of said analog signal, comprising: a. storage means for storing reference digital code word; b. means, responsive to said identifying digital code word and said stored reference digital code word, for generating a difference digital code word representative of the difference between said identifying digital code word and said stored reference digital code word; and c. means for varying said stored rEference digital code word with said difference digital code word.
Claim 12
Dependent Claim
104 words
Apparatus for converting successive identifying digital code words, wherein each digital code word is n-bit length and wherein said identifying digital code words represent an analog signal, into second digital code words representative of said analog signal, comprising: a. storage means for storing reference digital code word; b. means, responsive to said identifying digital code word and said stored reference digital code word, for generating a difference digital code word representative of the difference between said identifying digital code word and said stored reference digital code word; and c. means for varying said stored rEference digital code word with said difference digital code word.
Claim 13
Dependent Claim
36 words
The apparatus of claim 8 wherein said difference digital code word generating means comprises means for subtracting said stored reference digital code word from said identifying digital code word to obtain an n-bit digital code word.
Claim 14
Dependent Claim
120 words
The apparatus of claim 9 further comprising: a. means for generating a first digital code word of n-x bit length representing a predetermined magnitude if the difference obtained by said subtraction is positive and greater than said predetermined magnitude; b. means for generating a second digital code word of n-x bit length representing said predetermined magnitude if the difference obtained by said subtraction is negative and greater than the predetermined magnitude; and c. means for generating a third digital code word of n-x bit length representing the actual difference if the difference obtained by said subtraction is a magnitude less than the predetermined magnitude, wherein x the number of most significant bits truncated from the n-bit difference digital code word.
Claim 15
Dependent Claim
37 words
The apparatus of claim 10 wherein said means for varying comprises means for digitally adding said difference digital code word to said reference digital code word and storing the result as a new reference digital code word.
Claim 16
Dependent Claim
110 words
In a differential pulse code modulation transmission system wherein a digital code word representing a difference between a present analog sample and a previous analog sample is transmitted, apparatus, at a receiver, for reconstructing the present analog sample, comprising: a. means for storing a reference digital code word representing said previous analog sample; b. means for digitally combining said stored reference digital code word with said difference digital code word to provide a new reference digital code word; c. means for storing said new reference digital code word; and d. means for converting said new reference digital code word into an analog signal, whereby said present analog signal is reconstructed.
Claim 17
Dependent Claim
110 words
In a differential pulse code modulation transmission system wherein a digital code word representing a difference between a present analog sample and a previous analog sample is transmitted, apparatus, at a receiver, for reconstructing the present analog sample, comprising: a. means for storing a reference digital code word representing said previous analog sample; b. means for digitally combining said stored reference digital code word with said difference digital code word to provide a new reference digital code word; c. means for storing said new reference digital code word; and d. means for converting said new reference digital code word into an analog signal, whereby said present analog signal is reconstructed.
Claim 18
Dependent Claim
25 words
The apparatus of claim 12 wherein the means for combining comprises digitally adding said stored reference digital code word to said difference digital code word.
Claim 19
Dependent Claim
171 words
In a differential pulse code modulation transmission system wherein a difference digital code word of n-bit length representing the difference between a present analog sample and a previous analog sample is generated and wherein a difference digital code word of n-x bit length is transmitted, wherein x the number of most significant bits truncated from said n-bit difference digital code word, apparatus, at a receiver, for reconstructing the present analog sample, comprising: a. means for storing a reference digital code word; b. means for reconverting said difference digital code word of n-x bit length to the difference digital code word of n-bit length; c. means for digitally adding said stored reference digital code word with said reconverted difference digital code word to provide a new reference digital code word; into an analog signal, whereby said present analog signal ; d. means for storing said new reference digital code word; and e. means for converting said new reference digital code word into an analog signal, whereby said present analog signal is reconstructed.
Claim 20
Dependent Claim
171 words
In a differential pulse code modulation transmission system wherein a difference digital code word of n-bit length representing the difference between a present analog sample and a previous analog sample is generated and wherein a difference digital code word of n-x bit length is transmitted, wherein x the number of most significant bits truncated from said n-bit difference digital code word, apparatus, at a receiver, for reconstructing the present analog sample, comprising: a. means for storing a reference digital code word; b. means for reconverting said difference digital code word of n-x bit length to the difference digital code word of n-bit length; c. means for digitally adding said stored reference digital code word with said reconverted difference digital code word to provide a new reference digital code word; into an analog signal, whereby said present analog signal ; d. means for storing said new reference digital code word; and e. means for converting said new reference digital code word into an analog signal, whereby said present analog signal is reconstructed.
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) | 1975-12-26 | 1976-06-26 | 1976-12-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-12-26 | 1980-06-26 | 1980-12-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-12-26 | 1984-06-26 | 1984-12-26 | $7700.00 | Window Closed / Lapsed |