US3760277A
Expired / Lapsed
US
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Coding and decoding system with multi-level format
Assignee: Racal Data Communications Inc
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Filing: 1971-05-17
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Granted: 1973-09-18
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Expires: 1991-05-17
Abstract
Abstract The present invention is directed to a method and apparatus for coding and decoding data so that it may be transmitted from point to point in either a baseband system or in a carrier system. The method and apparatus involves forming a multi-bit group of binary signals (bits) and transmitting such signals with at least one bit and a fractional part of another bit of the group in an encoding period. In a preferred embodiment of my invention a pair of adjacent encoding periods are employed to fully identify all of the bits of a multi-bit group. My format requires less bandwidth than prior art binary formats. Furthermore, my format, when employed with a three level system, also requires less bandwidth than any known prior art three level system. The invention also includes an inherent error detection capability. Such inherent error detection is utilized at the receiver to automatically emit a decoded signal which has a high probability of being the correct signal that was transmitted. In addition, the invention readily provides a signal of a unique characteristic from which a decoding clock can be simply and easily derived.
Inventors
- 👤 S Whang
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 17:54
CPC Classifications
H; H04; H04L; H04L25/00; H04L25/38; H04L25/40; H04L25/49; H04L25/4917; H04L25/4919
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
174 words
A data transmission system having a carrier signal to be transmitted over a communication link, said system comprising: means at a transmitter for grouping, into a multi-bit word, input binary data having a data rate defined by a given number of input bit periods per second with one data bit represented in each input bit period; means responsive to said grouping means for generating a discrete signal level during at least a pair of modulation periods per multi-bit word for representing the identity of the multi-bit word, said signal generating means characterized by emitting a signal having a data bit-to-baud ratio of a mixed number and by emitting said discrete signal levels in a continuous sequence that represents a plurality of adjacent ones of said multi-bit data words; means for modulating said carrier signal with said signal from said generating means; and means at a receiver for deriving a clock signal from said signal modulated carrier, which clock signal is synchronized in time with the baud rate of said generating means at said transmitter.
Claim 2
Dependent Claim
174 words
A data transmission system having a carrier signal to be transmitted over a communication link, said system comprising: means at a transmitter for grouping, into a multi-bit word, input binary data having a data rate defined by a given number of input bit periods per second with one data bit represented in each input bit period; means responsive to said grouping means for generating a discrete signal level during at least a pair of modulation periods per multi-bit word for representing the identity of the multi-bit word, said signal generating means characterized by emitting a signal having a data bit-to-baud ratio of a mixed number and by emitting said discrete signal levels in a continuous sequence that represents a plurality of adjacent ones of said multi-bit data words; means for modulating said carrier signal with said signal from said generating means; and means at a receiver for deriving a clock signal from said signal modulated carrier, which clock signal is synchronized in time with the baud rate of said generating means at said transmitter.
Claim 3
Dependent Claim
23 words
A system in accordance with claim 1 wherein each multi-bit word comprises three binary bits and said mixed number bit-to-baud ratio is 1.5.
Claim 4
Dependent Claim
120 words
A system in accordance with claim 2 wherein the bits of binary values are identified by occupying one of two possible signal levels during sequentially-appearing input bit periods, and said generating means comprises an encoder employing a trinary format which comprises three signal levels and a modulation period equal to 1 1/2 bit periods; said system comprising: means modulating said carrier with a discrete signal level during a first modulation period of a pair of adjacent modulation periods for partially identifying the bits for a multi-bit word to be represented in that modulation period; and means modulating a given signal level during the second modulation period of said pair for completing the identity of the bits of said multi-bit word.
Claim 5
Dependent Claim
60 words
A system in accordance with claim 3 and wherein said generating means comprises: means for selecting a given amplitude level from levels of 0, +Y, or -Y, where Y is a predetermined voltage for said discrete signal level in said first and second modulation periods of said pair; and means for amplitude modulating said carrier with said selected amplitude levels.
Claim 6
Dependent Claim
64 words
A system in accordance with claim 3 and wherein said generating means comprises: means for selecting a given phase angle from three different substantially equally separated phase angle amounts for said discrete signal levels in said first and second modulation periods of said pair; and means for differentially phase modulating said carrier with said selected phase angle amounts in said pair of modulation periods.
Claim 7
Dependent Claim
45 words
A system in accordance with claim 4 wherein a word comprised of three binary bits represents eight possibilities and means in said encoder for assigning each possibility one matrix position from the nine possible matrix positions for identifying the signal levels in a Trit Pair.
Claim 8
Dependent Claim
138 words
A system in accordance with claim 6 wherein the one unused data-representing possibility of the matrix is assigned by Said possibility assigning means to have signal values for adjacent Trit Pairs such that a random string of binary data yields a trinary format signal having signal energy distribution including a frequency of 1/2 T where T is the modulation period for a Trit, and said system comprising a demodulator adapted for connection to said communication link said demodulator comprising: means for receiving said trinary format modulated carrier signal including at least one Trit Pair: means connected to said clock signal deriving means and responsive thereto for sampling the signal levels of said Trit Pair; and means associated with said sampling means for emitting the multi-bit binary bit word identified by the signal levels sampled from said Trit Pair.
Claim 9
Dependent Claim
93 words
A system in accordance with claim 7 wherein said input binary data has a bit rate of about 7,200 bits per second and said transmitter further comprises: timing means for assigning a baud rate for said trinary format of about 4,800, and said signal level modulated carrier has a bandwidth of 1/2 T where T is the modulation period; means for adding a pilot tone to said signal level modulated carrier; and means for applying the pilot tone and the signal level modulated carrier as a vestigial sideband carrier to a communication link.
Claim 10
Dependent Claim
26 words
A system in accordance with claim 8 including at said receiver: means for removing said pilot tone from the vestigial sideband carrier received over said link.
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) | 1976-09-17 | 1977-03-19 | 1977-09-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-09-17 | 1981-03-19 | 1981-09-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-09-17 | 1985-03-19 | 1985-09-18 | $7700.00 | Window Closed / Lapsed |