EP0162714A2
Expired / Lapsed
EP
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Coding baseband signals
Assignee: National Research Development Corp UK
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Filing: 1985-05-22
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Granted: —
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Expires: 2005-05-22
Abstract
Abstract It is known that the tolerance to noise of data transmission systems carrying digital signals can be improved bv coding the signals before transmission. The present invention provides a further improvement by using a correlative-level code and non- linearly transforming the coded signals to reduce the range of possible values. Correlative-level coding may be carried out using a linear feedforward transversal filter 16 and an adder 17, and a modulo-m network 20 (where m need not be an integer) may be used for non-linear transformation. Additionally a subtractor 14 and a modulo-4 network 15 may be provided for precoding, while the range of signals by the use of subtractor 18 and a multiplier 19. By employing orthogonal signals detection may be simplified.
Inventors
- 👤 Adrian Percy Clark
- 👤 Shu Fun Alexis Ip
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-28 16:53
CPC Classifications
H; H04; H04L; H04L25/00; H04L25/38; H04L25/40; H04L25/49; H04L25/497; H04L25/4975; H04L25/02; H04L25/03; H04L25/03006; H04L25/03343
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
64 words
Apparatus for coding digital signals comprising means for effectively coding digital signals using a correlative-level code characterised by means for effectively non-linearly transforming the coded signals to reduce the range of possible values of the coded signals, the apparatus being such that in the presence of noise, signals generated can be detected with an improved signal to noise ratio in comparison with uncoded signals.
Claim 2
Dependent Claim
64 words
Apparatus for coding digital signals comprising means for effectively coding digital signals using a correlative-level code characterised by means for effectively non-linearly transforming the coded signals to reduce the range of possible values of the coded signals, the apparatus being such that in the presence of noise, signals generated can be detected with an improved signal to noise ratio in comparison with uncoded signals.
Claim 3
Dependent Claim
19 words
Apparatus according to Claim 1 characterised in that the means for correlative-level coding comprises a linear feedforward transversal filter.
Claim 4
Dependent Claim
104 words
Apparatus according to Claim 1 or 2 characterised in that the means for non-linearly transforming the coded signals is arranged to carry out a modulo operation in which output signals q i have the following relationship with the correlative-level signals p i q i = (p i + m/2)mod-m - m/2, where the function (p i + m/2)mod-m = p i + m/2 + nm, m is a constant, and n is a positive or negative integer such that 0 ≤ (pi+ m/2)mod-m < m, the range -m/2 to m/2 being arranged to be smaller than the range of possible values p i .
Claim 5
Dependent Claim
58 words
Apparatus according to any preceding claim characterised in that the mean of the possible values of the correlative-level coded signals is subtracted from the correlative-level coded signals and the result is multiplied by a constant before application to the non-linearly transforming means, the constant being chosen to provide a predetermined power level at the output of the apparatus.
Claim 6
Dependent Claim
39 words
Apparatus according to any preceding claim characterised by the inclusion of means for precoding digital signals applied at the input to the apparatus, the precoding being such that on detection an improved signal to noise ratio can be achieved.
Claim 7
Dependent Claim
41 words
Apparatus according to Claim 5 characterised in that the precoding comprises subtracting the output of the correlative-level coding means from the input signals thereto using modulo arithmetic such that the range of signal values after precoding is smaller than before precoding.
Claim 8
Dependent Claim
22 words
Apparatus according to any preceding claim characterised in that the correlative-level coding means is arranged to provide substantially orthogonally coded output signals.
Claim 9
Dependent Claim
37 words
Apparatus according to any preceding claim characterised in that the means for correlative-level coding and the means for non-linear transformation are formed by an electrical store holding a look-up table containing coded outputs corresponding to uncoded inputs.
Claim 10
Dependent Claim
46 words
Apparatus according to Claim 8 insofar as dependent on Claim 4 characterised in that the process carried out by the look-up table includes subtraction of the said mean and multiplication by a constant chosen to provide a predetermined power level at the output of the apparatus.
Claim 11
Dependent Claim
28 words
Apparatus according to Claim 8 or 9 insofar as dependent on Claim 5 or 6 characterised in that the process carried out by the look-up table includes precoding.
Claim 12
Independent Claim
57 words
A method for coding digital signals comprising coding the signals using a correlative-level code, characterised by non-linearly transforming the coded signals to reduce the range of possible values thereof, the method being such that in the presence of noise the signals generated can be detected with an improved signal to noise ratio in comparison with uncoded signals.
Claim 13
Independent Claim
57 words
A method for coding digital signals comprising coding the signals using a correlative-level code, characterised by non-linearly transforming the coded signals to reduce the range of possible values thereof, the method being such that in the presence of noise the signals generated can be detected with an improved signal to noise ratio in comparison with uncoded signals.
Claim 14
Dependent Claim
17 words
A method according to Claim 11 characterised in that coding using a correlative-level code generates orthogonal signals.
References Cited (Backward Citations)
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