CA1215134A - Process for restoring to shape a deformed numerical signal and device for putting the process into effect - Google Patents
Process for restoring to shape a deformed numerical signal and device for putting the process into effectInfo
- Publication number
- CA1215134A CA1215134A CA000453945A CA453945A CA1215134A CA 1215134 A CA1215134 A CA 1215134A CA 000453945 A CA000453945 A CA 000453945A CA 453945 A CA453945 A CA 453945A CA 1215134 A CA1215134 A CA 1215134A
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- Canada
- Prior art keywords
- signal
- amplitude
- intermediate signal
- input
- slope
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K5/00—Manipulating of pulses not covered by one of the other main groups of this subclass
- H03K5/01—Shaping pulses
- H03K5/08—Shaping pulses by limiting; by thresholding; by slicing, i.e. combined limiting and thresholding
- H03K5/082—Shaping pulses by limiting; by thresholding; by slicing, i.e. combined limiting and thresholding with an adaptive threshold
- H03K5/086—Shaping pulses by limiting; by thresholding; by slicing, i.e. combined limiting and thresholding with an adaptive threshold generated by feedback
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/06—Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection
- H04L25/061—Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection providing hard decisions only; arrangements for tracking or suppressing unwanted low frequency components, e.g. removal of dc offset
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- Power Engineering (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Dc Digital Transmission (AREA)
- Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
Abstract
ABSTRACT
The invention relates to a process for restoring to shape a deformed numerical signal and also to a device for putting the process into effect.
The process consists in working out an intermediate analog signal SI for the signal S, noting the times of intersection of the signals SI and S, and working out a binary signal N which passes from one binary state to the other at each of the times of intersection. The binary signal SN is identical with the signal S1, which is itself equal to the signal S before the deformation of such signal S. The working out of the intermediate signal SI depends on its law of evolution and on contraints imposed on its slope and amplitude.
Application to numerical signal receivers.
The invention relates to a process for restoring to shape a deformed numerical signal and also to a device for putting the process into effect.
The process consists in working out an intermediate analog signal SI for the signal S, noting the times of intersection of the signals SI and S, and working out a binary signal N which passes from one binary state to the other at each of the times of intersection. The binary signal SN is identical with the signal S1, which is itself equal to the signal S before the deformation of such signal S. The working out of the intermediate signal SI depends on its law of evolution and on contraints imposed on its slope and amplitude.
Application to numerical signal receivers.
Description
39~
Technical title PROCESS FOR RESTORING To SHAPE A DEFORMED`NUME~XCAL SIGNAL AND
Device FOR PUTTING THE PROCESS INTO EJECT
... ... _ . _ .. _ . , , _ Background of the inYent~on The invention relates to a process for regenerating a deformed numerical signal and to a device for putting the process into effect. The invention can be more particularly applied to numerical transmission in numerical signal receivers.
A numerical transmission consists in an emitter E, a transmission channel C and a receiver R. The emitter E sends impulses to the transmission duct C, which forms a filter deforming the impulses emitted by the emitter E. More particularly, if the transmission channel C comprises transformers, ho transmit low frequencies unsatisfactorily.
Moreover, the cable weakens high frequencies. At the output of the transmission channel C the impulses are therefore deformed. They are elongated and may even straddle one another. In the majority of cases the receiver R cannot therefore detect them in a simple manner.
To carry out reception, an engineer in the art uses in known manner an equalizer for compensating the weakening distortion of the cable and a complementary Nyquist filter to separate the straddling impulses. This method has a number of disadvantages. The equalizer favors high frequencies - i.e., more particularly high frequency stray signals, and complicates the construction ox the associated low- pass filter. On the other hand, this kind of receiver eliminates the signals comprising a low frequency component, because of the difficulty of equalizing such signals. Finally, the use of Nyquist filter makes this receiver a complex device.
Problem of the Invention The object of the invention is precisely to obviate these disadvantages. The invention relates to vex simple way of processing the signal received by the receiver R in order --1-- I,.
~,'~
I
to restore to shape that deformed numerical signal. eye invention also provides a very simple and economic high-performance device for putting the process into effect.
Brief Statement of the Invention More precisely, the invention relates to a process for restoring to shape a deformed numerical signal wherein from the signal S an intermediate analog signal SO is worked out on which two constraints are imposed namely, on the one hand: the difference in absolute value between the amplitude of the analog signal SO and the amplitude of the signal S is maintained at a value at most equal to a first predetermined value OX lower than the peak value of the signal S; on the other hand the slope in absolute value of the intermediate signal SO is maintained at most equal to a second predetermined value UP lower than the slope of the useful transitions of the signal S, the sign of the slope P being equal to that of the result of the comparison between the signal SO and S, on condition that in case of conflict in satisfying the two constraints, the first constraint is satisfied, the result of the comparison between the amplitudes of the signals SO and S supplying a binary signal SUN
forming a restoration to shape of the signal S.
In the process according to the invention the predetermined value X is lower than the peak value of the signal S, preferably being lower than half the peak value of the signal S.
By the useful transition of the signal S we mean a transition representing an item of information - i.e., a real transition of the binary or bipolar signal emitted. The slope PUP must he lower than the slope of the useful transitions.
Louvre, it must not be too low, since it must also be greater than the slope of the stray signals of the signal S.
The invention also relates to a device for putting the process into effect which comprises a means for working out an intermediate signal SO which has a control input receiving at an input the signal S and delivering at an output the intermediate I
signal SIX the means for working out the intermediate signal SO
comprising a first means for limiting the difference between the amplitude of the intermediate signal SO and the amplitude of the signal S to a predetermined value OX, such first means being connected to the input and output of the means for working out the intermediate signal SIX the device also comprising a second means for limiting the slope of the intermediate signal SO connected to the output of the means for working out the intermediate signal SIX such second means receiving at an input a current of constant intensity I and an inversion means whose input is formed by the control input of the means for working out the intermediate signal SO and one of whose outputs delivers a current of intensity I; and the device also comprises a comparison means receiving at its inverting input the signal S
and at its non-inverting input the intermediate signal SO and delivering a binary signal SUN applied on the one hand to the control input of the means for working out the intermediate signal, the binary state of the signal SUN determining the direction of the current of intensity I, and on the other hand to the input of an inventor which delivers the signal SUN
identical with the signal S before deformation.
According to a secondary feature of the device according to the invention the first means is formed by two identical diodes mounted in parallel, the anode of one diode being connected to the cathode of the other diode.
According to another secondary feature, the second means is formed by a capacitor.
Description of Drawings The features and advantages of the invention will be more clearly gathered from the following merely illustrative, non-limitative description, with reference to the accompanying drawings, wherein:
- Fig. 1 is a graph showing different numerical signals, - Fig. 2 is a diagram of the state of the intermediate signal SIX
- jig. 3 is an organigram showing the rules of evolution in time of the intermediate signal SIX
- Fig. is a diagram illustrating a device for putting the process according to the invention into effect t - Fig. 5 is diagram illustrating an embodiment of the device according to the invention.
Description of the Preferred Embodiment Referring to Fig. 1, a numerical signal SO represents a binary signal to be emitted by the emitter E. The signal is actually emitted into a transmission channel C after coding.
The coding can be, for example, bipolar, as shown at So in Fig. Lowry some other coding. The transmission channel C
deforms the emitted signal by not transmitting the low frequencies and weakening the high frequencies. This results more particularly from the widening and possible overlapping of the impulses. The signal received by the numerical receiver R
and corresponding to the signal emitted by the emitter E has therefore the outline of the signal S.
To recover the original signal emitted by emitter E, it is enough to recover the transitions of the emitted signal from the signal S shown in a solid line in the drawing. In the process according to the invention this is done by working out an intermediate signal SO shown in chain-dot lines in Fig. 1.
The rules of obten~ion and evolution of the intermediate signal SO will be given in detail with reference to Figs. 2 and 3.
The intermediate signal SO is so constructed that its amplitude is equal to that of the signal S at each transition of the numerical signal Sly By comparing -the signals SO and S, we can therefore produce the signal SUN whose transitions are identical to those of the signal Sly It will be noted with reference to Fig. 1 that the intermediate signal SO can be described as being governed by four different states of evolution El, En, En and En. In the first state El, the slope of the signal SO is equal to the slope of the signal S, and the amplitude of the signal SO is lower than the amplitude of the signal S; in the second state En, the slope of the signal is still equal to the slope of the signal Lo but the amplitude of the signal SO is greater than the amplitude ox thy signal I; in the thud state En, the slope of the signal SO is constant and decreasing, and in the fourth state En, the slope of the signal SO is constant and increasing.
The two states of the sequence ox ruin out the intermediate signal SO of the process accordln~ to top invention can be expressed by means of these four stout. The first stage is formed by the succession of the states En, thin En, or by the succession of the states El, then En, The state En, or the state En, corresponds to that part of the stage in which the first constraint is reached, and in which therefore the second constraint is ignored, or in which no constraint is reached, the intermediate signal SO freely following the signal S, In this first stage E, the difference between the amplitude of the intermediate signal SO and the amplitude of the signal S is still equal to the first predetermined value OX. I've state En, or the state En, corresponds to that part of the stage in which the second constraint is reached. The second stage is formed by the state En or the state En.
The four states just mentioned and the rules for transition from one state to another will now be described in greater detail with reference to Figs. 2 and 3.
Fig. 2 is a graph showing the states of the signal SO
and the transitions between such states. The transition between a state Hi and a state En, where i and j lie between 1 and 4 is represented by Tip. In cases where i is equal to j, the transition Tip expresses that the intermediate signal SO
remains in the state Hi. Each of these four states characterizes a particular law of evolution of the intermediate signal SIX The transitions Tip between a state Hi and En, where i and j are integers lying between 1 and 4, appear precisely when one or both constraints are reached, or when a particular condition is present/ such as equality between the amplitude of the intermediate signal SO and the amplitude of signal S. The transitions of type Tip express maintenance in the state Hi.
I I
A description will no be inn of the equations ~oyerning the evolution pi the intermediate signal SO in each of the states and the constraints or conscience corresponding to the transitions between sunk states.
In the state El toe intermediate signal SO has at each moment an amplitude equal to that of the snowily S Linus the predetermined value a. This state continues as long as the slope of the signal S is greater Han the opposite of the predetermined value UP. This is expressed by the transition T11. If the slope of the signal S becomes lower than the opposite of the predetermined value UP, there is a transition T13 from the state El to the state En.
In the state En, the intermediate signal SO has a constant slope which is equal in modulus to the predetermined value UP and whose sign is negative. This state can be left for a transition to the state En when the first constraint is reached. It can also be abandoned for the state En, by the transition T34, when the amplitude of the signal S is equal to the amplitude of the intermediate signal SIX
In the state En, the slope o* the intermediate signal SO is equal in absolute value to UP, as in state En, but its sign is positive. As can be seen from Fig. 1, there are two means of leaving this state En. A transition appears when the amplitude of the intermediate signal SO is equal to the amplitude of the signal S. This transition T34 causes a change from state En to state En. Another transition is possible from the state En. It appears when the difference in amplitude between the intermediate signal SO and the signal S
becomes greater than the predetermined value X. We then pass via the transition T42 from state En to state En.
The fourth and last state is the state En. In this state the signal SO has at each moment an amplitude equal to that of the signal S plus the predetermined value X, This state remains as long a the slope of the signal S Remains lower than the second predetermined value APT when this constraint is reached we pass from state En to state En via truncheon T24.
Fix. 3 is an oX~anigx~m describing thy evolution in time of the intermediate signal SO and coxrespondin~ to the graph in jig. 2. The intermediate signal SO worked out by this means is known ho its amplitude at times to, tool, to etc...
The object of thus identify indiyidual!inter~ediate signals SO is merely to make the presentation clearer, It certainly does not limit the invention to working out an individual intermediate signal SIX since a continuous signal can simply be considered to be an individual signal whose sampling frequency is extremely high.
The references 1, 2, 3 and 4 respectively denote the rules of evolution of the intermediate signal SO in the states El En 7 En and En. Let us suppose that at a moment t we are in the state 1. The amplitude of the intermediate signal SO is equal to the amplitude of the signal S at the same moment t minus the predetermined valuel~X. We shall now try to determine the amplitude of the intennediate signal SO at the successive moment to To this end we compare the slope between the times t and to of the signal S with the predetermined value P. If the reduction in signal S between t and to is greater than UP, we pass into the state En. In the opposite case we remain in the state El. The first case corresponds to the transition T13 of Fig. 2 and the second case to the transition Toll.
When we are in state En, the amplitude of the immediate signal SO at any moment is equal to the amplitude of the same signal at the preceding moment minus the predetermined value P. If, when thus reduced by a value P, the amplitude of the intermediate signal SO becomes lower at a given moment than the amplitude of the signal S at the same moment minus the predetermined value OX, we pass back to state El. This corresponds to the transition T31 in Fig. 2. In the opposite case, in dependence on whether or not the amplitude of the intermediate signal SO is equal to the amplitude of the signal S, we pass to the state En (i.e., the transition T34), or we remain in the state En (i.e., the transition T33).
When we are in the state En, the amplitude of the intermediate signal So at given moment it equal to its amplitude at the preceding moment plus thy redetermined value apt If, when increased ho the value UP, the amplitude of the intermediate signal SO become higher than the amplitude at the same moment of the signal S increased the predetermined value OX, we pass into state En (i.e., thy transition T42).
In the opposite cave, in dependence on whether or not the amplitude of the intermediate signal SO become equal to the amplitude of the signal S as a result of an increase by the value P, we pass into state En, (i.e., the transition T43), or we remain in the state En (i.e., the transition T44).
When we are in the state En, the amplitude of the intermediate signal So is equal at a given moment to the amplitude of the signal S at the same moment increased by the predetermined value OX. If, when we are in the state En, the slope of the signal S becomes greater than UP - ire., if the difference in amplitude of the signal S between two successive moments becomes higher than apt we pass into state En (i.e., the transition T24). In the opposite case we remain in the state En (i.e., the transition T22).
The organigram descried in Fig. 3 is used in the device illustrated diagrammatically in Fig. 4. It comprises a first means 10 for limiting the difference in amplitude between the signal S and the intermediate signal SO to a predetermined value X. The first means 10 receives at its input the signal S and is connected on another input to the intermediate signal SIX The device also comprises a second means for limiting the speed of variation in the amplitude of the signal SO to a maximum predetermined value P. The second means 12 receives at one input a current of constant intensity I whose sign is determined by an inverting means 14. The assembly formed by the first means 10, the second means 12, and the inverting means 14, forms a means 15 for working out and delivering the intermediate signal SIX The device also comprises a comparator 16 receiving on an inyexting input the signal S and on a non-inverting input the intermediate signal So. It delivers a binary signal SUN which is identical except for the sign Thea Jo ~f2~ Lo the undeformed signal S. The binary signal SUN is applied on the one hand to an input of the inYertin~ means 14 to determine the sign of the current I delivered by the inverting means 14, and on the other hand to the input of an inventor 17 which restores the signal SUM equal to the signal S Hoff deformation.
Fig. 5 shows an embodiment of the device. The first means 10 is formed by two identical diodes 18 in parallel, the anode of one diode being connected to the cathode of the other diode. The predetermined value a x corresponds to the drop in voltage between the terminals of each diode.
The inverting means 14 is formed by a current generator delivering a constant current I whose sign is determined by the state of the binary signal SUN. The current I, in dependence on its sign, charges or discharges a capacitor 20 of value C which forms the second means 12. The second means 12 enables the slope of the intermediate signal SO to be limited to a predetermined value P which is equal to the relationship C
As can be seen in the case of the signals S and SO in Fig. 1, the times at which the two signals have the same amplitude depends on the maximum slope P of the intermediate signal SIX on the voltage X, on the period T of the emitted signal, and on the amplitude of the signal S. The slope P and the level of S must therefore be selected for satisfactory operation of the device, and more particularly for satisfactory resistance to possible interfering signals present on the line.
Experience shows that a satisfactory result is obtained with the following values:
- the slope P given by _ = Sax - the peak-to-peak value of the signal S measured between two consecutive peaks separated by the period T, lying between I X and I X.
The applicants produced a device such as that shown in Fig. 5 Its characteristics are: X=0.7, C=3 no and Ill ma The comparator used is the type LO 311. This device has been used more particularly by the applicants to restore to shape a binary signal of output 150 K bits~sec emitted in the So form of a bipolar signal of voltage I which has been deformed by a telephone line formed ho a,m,etall~c copper cable of diameter 0.4 em. Between the line and the device described the applicants inverted an amplifier whose gain so independent of frequency up to 150 kHz and which compensate the weakening of the cable towards 80 kHz. The length of cable used is of the order of 4,200 m. o'er shorter cables it is possible to insert between the telephone line and the amplifier a conventional additional line element familiar to an engineer in the art. The same device has also been used for restoring to shape a binary signal, emitted in binaryjand deformed by a line from zero to 1,000 m of telephone cable having a diameter of 0.4 mm, without equalizer or added line element.
Technical title PROCESS FOR RESTORING To SHAPE A DEFORMED`NUME~XCAL SIGNAL AND
Device FOR PUTTING THE PROCESS INTO EJECT
... ... _ . _ .. _ . , , _ Background of the inYent~on The invention relates to a process for regenerating a deformed numerical signal and to a device for putting the process into effect. The invention can be more particularly applied to numerical transmission in numerical signal receivers.
A numerical transmission consists in an emitter E, a transmission channel C and a receiver R. The emitter E sends impulses to the transmission duct C, which forms a filter deforming the impulses emitted by the emitter E. More particularly, if the transmission channel C comprises transformers, ho transmit low frequencies unsatisfactorily.
Moreover, the cable weakens high frequencies. At the output of the transmission channel C the impulses are therefore deformed. They are elongated and may even straddle one another. In the majority of cases the receiver R cannot therefore detect them in a simple manner.
To carry out reception, an engineer in the art uses in known manner an equalizer for compensating the weakening distortion of the cable and a complementary Nyquist filter to separate the straddling impulses. This method has a number of disadvantages. The equalizer favors high frequencies - i.e., more particularly high frequency stray signals, and complicates the construction ox the associated low- pass filter. On the other hand, this kind of receiver eliminates the signals comprising a low frequency component, because of the difficulty of equalizing such signals. Finally, the use of Nyquist filter makes this receiver a complex device.
Problem of the Invention The object of the invention is precisely to obviate these disadvantages. The invention relates to vex simple way of processing the signal received by the receiver R in order --1-- I,.
~,'~
I
to restore to shape that deformed numerical signal. eye invention also provides a very simple and economic high-performance device for putting the process into effect.
Brief Statement of the Invention More precisely, the invention relates to a process for restoring to shape a deformed numerical signal wherein from the signal S an intermediate analog signal SO is worked out on which two constraints are imposed namely, on the one hand: the difference in absolute value between the amplitude of the analog signal SO and the amplitude of the signal S is maintained at a value at most equal to a first predetermined value OX lower than the peak value of the signal S; on the other hand the slope in absolute value of the intermediate signal SO is maintained at most equal to a second predetermined value UP lower than the slope of the useful transitions of the signal S, the sign of the slope P being equal to that of the result of the comparison between the signal SO and S, on condition that in case of conflict in satisfying the two constraints, the first constraint is satisfied, the result of the comparison between the amplitudes of the signals SO and S supplying a binary signal SUN
forming a restoration to shape of the signal S.
In the process according to the invention the predetermined value X is lower than the peak value of the signal S, preferably being lower than half the peak value of the signal S.
By the useful transition of the signal S we mean a transition representing an item of information - i.e., a real transition of the binary or bipolar signal emitted. The slope PUP must he lower than the slope of the useful transitions.
Louvre, it must not be too low, since it must also be greater than the slope of the stray signals of the signal S.
The invention also relates to a device for putting the process into effect which comprises a means for working out an intermediate signal SO which has a control input receiving at an input the signal S and delivering at an output the intermediate I
signal SIX the means for working out the intermediate signal SO
comprising a first means for limiting the difference between the amplitude of the intermediate signal SO and the amplitude of the signal S to a predetermined value OX, such first means being connected to the input and output of the means for working out the intermediate signal SIX the device also comprising a second means for limiting the slope of the intermediate signal SO connected to the output of the means for working out the intermediate signal SIX such second means receiving at an input a current of constant intensity I and an inversion means whose input is formed by the control input of the means for working out the intermediate signal SO and one of whose outputs delivers a current of intensity I; and the device also comprises a comparison means receiving at its inverting input the signal S
and at its non-inverting input the intermediate signal SO and delivering a binary signal SUN applied on the one hand to the control input of the means for working out the intermediate signal, the binary state of the signal SUN determining the direction of the current of intensity I, and on the other hand to the input of an inventor which delivers the signal SUN
identical with the signal S before deformation.
According to a secondary feature of the device according to the invention the first means is formed by two identical diodes mounted in parallel, the anode of one diode being connected to the cathode of the other diode.
According to another secondary feature, the second means is formed by a capacitor.
Description of Drawings The features and advantages of the invention will be more clearly gathered from the following merely illustrative, non-limitative description, with reference to the accompanying drawings, wherein:
- Fig. 1 is a graph showing different numerical signals, - Fig. 2 is a diagram of the state of the intermediate signal SIX
- jig. 3 is an organigram showing the rules of evolution in time of the intermediate signal SIX
- Fig. is a diagram illustrating a device for putting the process according to the invention into effect t - Fig. 5 is diagram illustrating an embodiment of the device according to the invention.
Description of the Preferred Embodiment Referring to Fig. 1, a numerical signal SO represents a binary signal to be emitted by the emitter E. The signal is actually emitted into a transmission channel C after coding.
The coding can be, for example, bipolar, as shown at So in Fig. Lowry some other coding. The transmission channel C
deforms the emitted signal by not transmitting the low frequencies and weakening the high frequencies. This results more particularly from the widening and possible overlapping of the impulses. The signal received by the numerical receiver R
and corresponding to the signal emitted by the emitter E has therefore the outline of the signal S.
To recover the original signal emitted by emitter E, it is enough to recover the transitions of the emitted signal from the signal S shown in a solid line in the drawing. In the process according to the invention this is done by working out an intermediate signal SO shown in chain-dot lines in Fig. 1.
The rules of obten~ion and evolution of the intermediate signal SO will be given in detail with reference to Figs. 2 and 3.
The intermediate signal SO is so constructed that its amplitude is equal to that of the signal S at each transition of the numerical signal Sly By comparing -the signals SO and S, we can therefore produce the signal SUN whose transitions are identical to those of the signal Sly It will be noted with reference to Fig. 1 that the intermediate signal SO can be described as being governed by four different states of evolution El, En, En and En. In the first state El, the slope of the signal SO is equal to the slope of the signal S, and the amplitude of the signal SO is lower than the amplitude of the signal S; in the second state En, the slope of the signal is still equal to the slope of the signal Lo but the amplitude of the signal SO is greater than the amplitude ox thy signal I; in the thud state En, the slope of the signal SO is constant and decreasing, and in the fourth state En, the slope of the signal SO is constant and increasing.
The two states of the sequence ox ruin out the intermediate signal SO of the process accordln~ to top invention can be expressed by means of these four stout. The first stage is formed by the succession of the states En, thin En, or by the succession of the states El, then En, The state En, or the state En, corresponds to that part of the stage in which the first constraint is reached, and in which therefore the second constraint is ignored, or in which no constraint is reached, the intermediate signal SO freely following the signal S, In this first stage E, the difference between the amplitude of the intermediate signal SO and the amplitude of the signal S is still equal to the first predetermined value OX. I've state En, or the state En, corresponds to that part of the stage in which the second constraint is reached. The second stage is formed by the state En or the state En.
The four states just mentioned and the rules for transition from one state to another will now be described in greater detail with reference to Figs. 2 and 3.
Fig. 2 is a graph showing the states of the signal SO
and the transitions between such states. The transition between a state Hi and a state En, where i and j lie between 1 and 4 is represented by Tip. In cases where i is equal to j, the transition Tip expresses that the intermediate signal SO
remains in the state Hi. Each of these four states characterizes a particular law of evolution of the intermediate signal SIX The transitions Tip between a state Hi and En, where i and j are integers lying between 1 and 4, appear precisely when one or both constraints are reached, or when a particular condition is present/ such as equality between the amplitude of the intermediate signal SO and the amplitude of signal S. The transitions of type Tip express maintenance in the state Hi.
I I
A description will no be inn of the equations ~oyerning the evolution pi the intermediate signal SO in each of the states and the constraints or conscience corresponding to the transitions between sunk states.
In the state El toe intermediate signal SO has at each moment an amplitude equal to that of the snowily S Linus the predetermined value a. This state continues as long as the slope of the signal S is greater Han the opposite of the predetermined value UP. This is expressed by the transition T11. If the slope of the signal S becomes lower than the opposite of the predetermined value UP, there is a transition T13 from the state El to the state En.
In the state En, the intermediate signal SO has a constant slope which is equal in modulus to the predetermined value UP and whose sign is negative. This state can be left for a transition to the state En when the first constraint is reached. It can also be abandoned for the state En, by the transition T34, when the amplitude of the signal S is equal to the amplitude of the intermediate signal SIX
In the state En, the slope o* the intermediate signal SO is equal in absolute value to UP, as in state En, but its sign is positive. As can be seen from Fig. 1, there are two means of leaving this state En. A transition appears when the amplitude of the intermediate signal SO is equal to the amplitude of the signal S. This transition T34 causes a change from state En to state En. Another transition is possible from the state En. It appears when the difference in amplitude between the intermediate signal SO and the signal S
becomes greater than the predetermined value X. We then pass via the transition T42 from state En to state En.
The fourth and last state is the state En. In this state the signal SO has at each moment an amplitude equal to that of the signal S plus the predetermined value X, This state remains as long a the slope of the signal S Remains lower than the second predetermined value APT when this constraint is reached we pass from state En to state En via truncheon T24.
Fix. 3 is an oX~anigx~m describing thy evolution in time of the intermediate signal SO and coxrespondin~ to the graph in jig. 2. The intermediate signal SO worked out by this means is known ho its amplitude at times to, tool, to etc...
The object of thus identify indiyidual!inter~ediate signals SO is merely to make the presentation clearer, It certainly does not limit the invention to working out an individual intermediate signal SIX since a continuous signal can simply be considered to be an individual signal whose sampling frequency is extremely high.
The references 1, 2, 3 and 4 respectively denote the rules of evolution of the intermediate signal SO in the states El En 7 En and En. Let us suppose that at a moment t we are in the state 1. The amplitude of the intermediate signal SO is equal to the amplitude of the signal S at the same moment t minus the predetermined valuel~X. We shall now try to determine the amplitude of the intennediate signal SO at the successive moment to To this end we compare the slope between the times t and to of the signal S with the predetermined value P. If the reduction in signal S between t and to is greater than UP, we pass into the state En. In the opposite case we remain in the state El. The first case corresponds to the transition T13 of Fig. 2 and the second case to the transition Toll.
When we are in state En, the amplitude of the immediate signal SO at any moment is equal to the amplitude of the same signal at the preceding moment minus the predetermined value P. If, when thus reduced by a value P, the amplitude of the intermediate signal SO becomes lower at a given moment than the amplitude of the signal S at the same moment minus the predetermined value OX, we pass back to state El. This corresponds to the transition T31 in Fig. 2. In the opposite case, in dependence on whether or not the amplitude of the intermediate signal SO is equal to the amplitude of the signal S, we pass to the state En (i.e., the transition T34), or we remain in the state En (i.e., the transition T33).
When we are in the state En, the amplitude of the intermediate signal So at given moment it equal to its amplitude at the preceding moment plus thy redetermined value apt If, when increased ho the value UP, the amplitude of the intermediate signal SO become higher than the amplitude at the same moment of the signal S increased the predetermined value OX, we pass into state En (i.e., thy transition T42).
In the opposite cave, in dependence on whether or not the amplitude of the intermediate signal SO become equal to the amplitude of the signal S as a result of an increase by the value P, we pass into state En, (i.e., the transition T43), or we remain in the state En (i.e., the transition T44).
When we are in the state En, the amplitude of the intermediate signal So is equal at a given moment to the amplitude of the signal S at the same moment increased by the predetermined value OX. If, when we are in the state En, the slope of the signal S becomes greater than UP - ire., if the difference in amplitude of the signal S between two successive moments becomes higher than apt we pass into state En (i.e., the transition T24). In the opposite case we remain in the state En (i.e., the transition T22).
The organigram descried in Fig. 3 is used in the device illustrated diagrammatically in Fig. 4. It comprises a first means 10 for limiting the difference in amplitude between the signal S and the intermediate signal SO to a predetermined value X. The first means 10 receives at its input the signal S and is connected on another input to the intermediate signal SIX The device also comprises a second means for limiting the speed of variation in the amplitude of the signal SO to a maximum predetermined value P. The second means 12 receives at one input a current of constant intensity I whose sign is determined by an inverting means 14. The assembly formed by the first means 10, the second means 12, and the inverting means 14, forms a means 15 for working out and delivering the intermediate signal SIX The device also comprises a comparator 16 receiving on an inyexting input the signal S and on a non-inverting input the intermediate signal So. It delivers a binary signal SUN which is identical except for the sign Thea Jo ~f2~ Lo the undeformed signal S. The binary signal SUN is applied on the one hand to an input of the inYertin~ means 14 to determine the sign of the current I delivered by the inverting means 14, and on the other hand to the input of an inventor 17 which restores the signal SUM equal to the signal S Hoff deformation.
Fig. 5 shows an embodiment of the device. The first means 10 is formed by two identical diodes 18 in parallel, the anode of one diode being connected to the cathode of the other diode. The predetermined value a x corresponds to the drop in voltage between the terminals of each diode.
The inverting means 14 is formed by a current generator delivering a constant current I whose sign is determined by the state of the binary signal SUN. The current I, in dependence on its sign, charges or discharges a capacitor 20 of value C which forms the second means 12. The second means 12 enables the slope of the intermediate signal SO to be limited to a predetermined value P which is equal to the relationship C
As can be seen in the case of the signals S and SO in Fig. 1, the times at which the two signals have the same amplitude depends on the maximum slope P of the intermediate signal SIX on the voltage X, on the period T of the emitted signal, and on the amplitude of the signal S. The slope P and the level of S must therefore be selected for satisfactory operation of the device, and more particularly for satisfactory resistance to possible interfering signals present on the line.
Experience shows that a satisfactory result is obtained with the following values:
- the slope P given by _ = Sax - the peak-to-peak value of the signal S measured between two consecutive peaks separated by the period T, lying between I X and I X.
The applicants produced a device such as that shown in Fig. 5 Its characteristics are: X=0.7, C=3 no and Ill ma The comparator used is the type LO 311. This device has been used more particularly by the applicants to restore to shape a binary signal of output 150 K bits~sec emitted in the So form of a bipolar signal of voltage I which has been deformed by a telephone line formed ho a,m,etall~c copper cable of diameter 0.4 em. Between the line and the device described the applicants inverted an amplifier whose gain so independent of frequency up to 150 kHz and which compensate the weakening of the cable towards 80 kHz. The length of cable used is of the order of 4,200 m. o'er shorter cables it is possible to insert between the telephone line and the amplifier a conventional additional line element familiar to an engineer in the art. The same device has also been used for restoring to shape a binary signal, emitted in binaryjand deformed by a line from zero to 1,000 m of telephone cable having a diameter of 0.4 mm, without equalizer or added line element.
Claims (5)
1. A process for restoring to shape a de-formed numerical signal S, wherein from the signal S an intermediate analog signal SI is worked out on which two constraints are imposed namely, on the one hand: the difference in absolute value between the amplitude of the analog signal SI and the amplitude of the signal S
is maintained at a value at most equal to a first prede-termined value .DELTA.X lower than the peak value of the signal S; on the other hand the slope in absolute value of the intermediate signal SI is maintained at most equal to a second predetermined value .DELTA.P lower than the slope of the useful transitions of the signal S, the sign of the slope .DELTA.P being equal to that of the result of the comparison between the signals SI and S, on con-dition that in case of conflict in satisfying the two constraints, the first constraint is satisfied, the result of the comparison between the amplitudes of the signals SI and S supplying a binary signal SN forming a restoration to shape of the signal S.
is maintained at a value at most equal to a first prede-termined value .DELTA.X lower than the peak value of the signal S; on the other hand the slope in absolute value of the intermediate signal SI is maintained at most equal to a second predetermined value .DELTA.P lower than the slope of the useful transitions of the signal S, the sign of the slope .DELTA.P being equal to that of the result of the comparison between the signals SI and S, on con-dition that in case of conflict in satisfying the two constraints, the first constraint is satisfied, the result of the comparison between the amplitudes of the signals SI and S supplying a binary signal SN forming a restoration to shape of the signal S.
2. A process according to Claim 1, wherein the predetermined value .DELTA.X is lower than half the peak value of the signal S.
3. A device for putting the process defined in Claim 1 into effect, wherein it comprises a means for working out an intermediate signal SI which has a control input receiving at an input the signal S and delivering at an output the intermediate signal SI, the means for working out the intermediate signal SI com-prising a first means for limiting the difference between the amplitude of the intermediate signal SI and the amplitude of the signal S to a predetermined value .DELTA.X, such first means being connected to the input and output of the means for working out the intermediate signal SI, the device also comprising a second means for limiting the slope of the intermediate signal SI con-nected to the output of the means for working out the intermediate signal SI, such second means receiving at an input a current of constant intensity I and an inversion means whose input is formed by the control input of the means for working out the intermediate signal SI and one of whose outputs delivers a current of intensity ?I; and the device also comprises a comparison means receiving at its inverting input the signal S and at its non-inverting input the intermediate signal SI
and delivering a binary signal SN applied on the one hand to the control input of the means for working out the intermediate signal, the binary state of the signal SN determining the direction of the current of intensity I, and on the other hand to the input of an inverter which delivers the signal SN identical with the signal S
before deformation.
and delivering a binary signal SN applied on the one hand to the control input of the means for working out the intermediate signal, the binary state of the signal SN determining the direction of the current of intensity I, and on the other hand to the input of an inverter which delivers the signal SN identical with the signal S
before deformation.
4. A device according to Claim 3, wherein such first means is formed by two identical diodes mounted in parallel, the anode of one diode being con-nected to the cathode of the other diode.
5. A device according to Claim 3, wherein the second means is formed by a capacitor.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8307806A FR2546006B1 (en) | 1983-05-10 | 1983-05-10 | METHOD FOR FORMATTING A DEFORMED DIGITAL SIGNAL AND DEVICE FOR CARRYING OUT SAID METHOD |
| FR8307806 | 1983-05-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1215134A true CA1215134A (en) | 1986-12-09 |
Family
ID=9288759
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000453945A Expired CA1215134A (en) | 1983-05-10 | 1984-05-09 | Process for restoring to shape a deformed numerical signal and device for putting the process into effect |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0125984B1 (en) |
| JP (1) | JPS59208961A (en) |
| CA (1) | CA1215134A (en) |
| DE (1) | DE3465677D1 (en) |
| FR (1) | FR2546006B1 (en) |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4339727A (en) * | 1978-03-07 | 1982-07-13 | Nippon Electric Co., Ltd. | Waveform converting circuit |
-
1983
- 1983-05-10 FR FR8307806A patent/FR2546006B1/en not_active Expired
-
1984
- 1984-05-04 DE DE8484400913T patent/DE3465677D1/en not_active Expired
- 1984-05-04 EP EP19840400913 patent/EP0125984B1/en not_active Expired
- 1984-05-09 CA CA000453945A patent/CA1215134A/en not_active Expired
- 1984-05-10 JP JP9194684A patent/JPS59208961A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS59208961A (en) | 1984-11-27 |
| EP0125984A1 (en) | 1984-11-21 |
| EP0125984B1 (en) | 1987-08-26 |
| FR2546006B1 (en) | 1989-06-02 |
| DE3465677D1 (en) | 1987-10-01 |
| FR2546006A1 (en) | 1984-11-16 |
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