DE2300762A1 - DECOMMUTATOR - Google Patents

Description

The invention relates to the field of radio communications and in particular a remote control or analog decommutator ^ on a addresses coded message, which consists of a sequence of pulses modulated in their duration, i.e. pulses. (the bits ü or 1 or represent synchronization signals), whose initial point temporally a uniform interval of a period T! ^ and their duration depends on the information! iinnalt (0 or 1 or "Syncnro") of the respective pulse changes. i

The expressions in parentheses above only represent Examples are to make the subject matter of the present application easier to understand. It must therefore be underlined that the invention is in no way limited to the case of a binary representation of each information or to the mixing of Synchronization signals with the information signals, because the Information signals can just as well be transmitted separately, ! even in a not sharp manner. You can check them out at reception.

! 309828/0 * 68 -2-

ORlGlNAL INSPECTED

recover locally starting from the starting times of the pulse trains.

Regardless of how the signals may be designed, the invention is intended further below to "improve compatibility on the basis of a Naciiricht of the type TDCS are described, which also below is explained in more detail.

When realizing a vehicle for use on board a

jzeuges provided decommutator, which is used for the recovery of

Information after the start is designed, there is a great difficulty in that built up from the various digits Groove information is embedded in thermal noise, which can be assumed to be white and Gaussian noise is. In addition, the received power can fluctuate in fairly large gimps, depending on the Distance between the transmitter on earth and the spacecraft and the location of the spacecraft.

In the known Dekommutiervorrichtungen that for processing a message TDCS or analog type have the disadvantage that when the information bits O and 1 have a fairly high error rate. This is in part because they are commonly used with diode stapling systems work, i.e. non-linear elements that follow the distribution law of the noise, which is then no longer a Gaussian law. But this becomes an obstacle for the

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correct operation of the decommutator, because for a A given signal-to-noise ratio at the input results in a significant deterioration in the bit error probability. this corresponds to an increase in the transmission power of the transmitter in large Equal dimensions if a given result is to be achieved. It is clear that when it comes to spacecraft connections, the question the work management of the decommutator on board of is of utmost importance when considering the size of the distances, the changes and the noise conditions under which must be worked.

The object of the invention is to provide an improved decommutator to accomplish.

It has now been found that the fluctuations in distance by large Extensions can be compensated if one is characteristic of the assigned information in addition to the part of the impulse, aucii uses the non-characteristic part to advantage. Therefore the invention provides that the extract of one piece of information corresponding signal by comparing the part of its duration integrated over a part of its duration which characterizes its information Impulse takes place with a ßzugsitz size locally by integrating the impulse over a not for its information; Characteristic part of its duration is retained, the ver j takes place with the help of facilities that help build the

iiezugsspaiinungsschwelIe a signal or bit based on an i «Vert O are used to determine the nature of the latter.

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jSo the comparison carried out finally enables a complete one Relief from changes in the input signal dynamics.

The "0" and "1" values are recorded in the same way the reconstruction of the synchronization signals. This is possible despite the noise. Moreover, it is in this context of particular advantage ^ the vibrations of the support beam demodulate by a coherent rectification of the envelope and not by a diode rectification.

Bs must be clarified in this context that the invention Decommutator can also be used for the intended goal without a coherent rectifier, however, those are The results are then less good. Instead of the coherent rectifier, a diode or analog system could be used, for example. In the Indeed, it has been found that working as close as possible to the maximum theoretical operating conditions can only be achieved by a good Designed combination of a decommutator assembly, in the manner described above, a comparison with a reference value takes place, and can be achieved from a rectifier for coherent rectification of the envelope. The invention is now based on the attached figures are described in more detail, wherein the illustrated embodiments are not intended to restrict the invention. from the figures show:

1 shows a message in the TDCS standard, FIG. 2 shows a basic arrangement of the decommutator, Fig. 3 is a block diagram of the basic elements of the invention

30382S / 04S & ~ ⁵ "

Decommutators,

Fig. 4 diagrams for explaining the operation of the Dekommutators _t Fig. 5 is a general block diagram of the invention

Decommutators and
Fig. 3 Feiilerv / aiirscneinlichtkeitskurve that have been achieved with a decommutator according to the invention.

In Fig. 1, for a better understanding of the underlying principles of the invention Ideas and for the construction of a practical application example a riachriciit of the type considered, the TüCS (= Tone Digital Command Standard) is called and used by NASA and European countries for remote control of their scientific SateMt-en is used. Although this "standard" is well known to those skilled in the art, a "word" is shown in FIG ! to recall the characteristic properties of the standard. The word is (in a Hertzian channel) according to the following ! Rule broadcast that was selected for the present case has been:

- a space E

- a synchronization signal S and

- a number of acnt information bits 10011010

The starting times of the signals or bits and their spacing define the clock frequency f; the successive points in time of the considered starting points in time are shifted in time by a period T − 1 / f. In those parts where only information is

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! is sent, the signals are through a subcarrier frequency F. modulated, which is equal to an integral multiple of the clock frequency If. In the standard under consideration, F = 72 f; from the 1 it can be seen that a bit 1 has a length of 36 oscillations which corresponds to a duration of T / 2; in the same way, e "n bit O has a length of 18 oscillations, which corresponds to T / 4. The synchronization signal has a length of 54 oscillations, which corresponds to a length of 3 T / 4. Because of the big Numbers of vibrations are not all shown in FIG. 1. One recognizes, therefore, that in such a way from in signals modulated with their duration or messages composed of bits,

-if the blank space signals are not taken into account- the first quarter of the period does not contribute anything to the information content; it is not characteristic of the corresponding information (type or size). Starting from the second and / or third quarter only of the period T i, the information in question can be determined.

The case of a spacecraft that is said to have been driven by the hrde receives from remote control signals which signals in TDCS are encoded and modulated on a suitable carrier wave amplitude. For this purpose are on board the spacecraft the following facilities:

- a reception antenna,

- A receiver connected to this antenna, which is intended to effect the first demodulation (in amplitude); da: recipient

309828 / CU58

-7-

outputs a video frequency signal that is divided into the noise of the;

\ Connection, ie in the thermal noise or background! noise or electronic noise of the receiver is embedded, wherein the receiver noise is advantageously on

■ is reduced to a minimum; \

- generates a üekommutator which receives the video signal and dekommutiert it dn signals from the binary type, the dißskt after conversion into a logical unit able to actuate the actuators, such as relays; as has already been said;

i i

related to the present invention essentially; on the iJekommutator and not on the others mentioned here

Facilities. j

The decommutator has the task of the bits O and 1, which according to the! Standard TDCS coded and carried by a subcarrier of a given frequency, converted into a signal sequence of the type NRZ.

Idles that are free from noise and the auxiliary carrier frequency is not have more and are therefore directly suitable for the logical unit.

It should be remembered that with signals of the type viRZ (= flo Return to Zero) the entire period of a bit represents the information carrier. For example, a 1 is represented by a first level (high) and a 0 by a second level (low) and you get the transition every time the bit [changes its state (from 0 to 1 or from 1 to 0) .

jüas additional noise in the message brings a deterioration

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: modification of the signal that "bit error" in the decommutator ! (Transformations of an O into a 1 and vice versa). It it is of course clear that it is extremely useful and important that the decommutator be designed in such a way that this Errors are kept to a minimum and that the error probability curve corresponds as closely as possible to the mathematical-theoretical curve that characterizes the type of coding used.

A sequence TDGS can be written as a function of time as follows:

f (t) - VTF sinU) _Q t. m (t)

In the above equation, P is the power, (»1 the angular frequency of the subcarrier and m (t) a function of time representing a modulation signal of the subcarrier; this modulation signal is partly periodically and partly accidentally.

In order to decode bits 0 and 1 of a sequence TDCS, an arrangement can be used, at least in theory, which is designed according to the scheme shown in FIG. The input signals f (t) are sent to a multiplier M ₁ , the other input of which is sinusoidal clock signals of the form V2 sin Ga t. This brings about a coherent rectification (detection coherente) of the envelopes of the input signals and the bits resulting from this rectification are fed to a "perfect" integrator I-which integrates between T / 4 and T / 2, ie over the one characteristic of the digit 1 Part of the period. The output signals are fed to a subtracter C., to which the reference value PT / 8 is also fed. From the subtracter C ₁ get the

309828/0458 - ^y -

Signals in a bit detector D. The introduction of the expression P.T / 8 serves the purpose in the case of the considered standard to define a "decision" threshold, which sicü as the mean the voltages representing bits 0 and 1 at the end of the integration build up, depending on the received: Power; the introduction of this expression thus ultimately serves to determine the bits.

This decommutation arrangement allows the theoretical maximum possible working behavior of the system, but has the heavy part of the fact that it depends on the performance P of the received, Signal depends. In other words, it works with a dynamic of the perfectly known input signal; but this is the case with the iiier envisaged earth-spacecraft connections not ι the case.

Device according to the invention, as shown in FIG. 3! and which is based solely on the admissible hypothesis that the dynamics of the input signal do not have enough time to encompass one Change in a time of the order of T / 4 (in practice on the order of about two milliseconds), erliiöglicnt overcoming the above-mentioned disadvantage.

In short, the following can be said: while the arrangement according to Fig.

2 works with a fixed threshold, arrangement j works GEiräß Fig. 3 with a controlled and slightly noisy threshold. In the arrangement according to FIG. 3, the multiplier demodulator feeds

309828/0458 ~ ^lü ~

who receives the input signal, simultaneously zi \ re parallel-connected chains; the upper chain consists of an integrator I ₉ ,

ι ^L

j which is integrated from 0 to T / 4, and a memory A ₂ in series ca al itation, which memory still stores the integrated signals during a

Quarter of the period. The lower chain consists of an (integrator L ·, which works from T / 4 to T / 2, and a doubler iVD. The output signals of the memory A ₉ and the doubler VD! Are simultaneously _{fed to the subtracter C 1} (comparator),! Its The output is connected to the bit detector D.

It should never be pointed out again that the ■ Fig. The arrangements shown in 2 and 3 are only theoretical principles ! mata, in which the connections to control the | Integrators have not been shown.

! TO ^x

! To enable a comparison in the comparator, one works

; with subtraction, i.e. the comparator is an adder, the

jthe voltages are supplied with opposite polarity. The mode of operation is to be illustrated with reference to FIG. on the line I is shown in solid lines a bit a, b, c, d of the fourth Ί; at the same time is a bit in dashed lines ; a, b, cjd 'represented by the value 0 (these bits are captured by f-L been). On line II are those that appear after integration Stresses shown. At the beginning of the first quarter! Of the period there is a negative voltage in the upper chain [set by the value -V, which during the following quarter of the

Period is stored in the memory A _{0 without much loss.}

309828/0458 ~ ^U ~

For a bit (1) an integration takes place only during the second quarter of the period in the lower chain. Because of the doubler VD, a voltage of + 2V is obtained; a voltage of 0 is obtained if a bit with the value 0 is present. In the ver ^; The same C. is obtained if it is a bit of the value 1. A voltage of 2V-V = and a voltage of -V +0 = -V if it is a bit of the value 0.

Accordingly, under the influence of the nearby noise, which in practice only has an effect of approximately 3 dB, voltages of gMchem Fourth and - opposite sign - whatever that Value V may be large or less large, i.e. voltages that can easily be evaluated by the bit detector D.

5 shows an assembly diagram of the decommutator according to the invention. It is composed primarily comprises the following '■ Iden modules:

- a phase coupled to the frequency of the subcarrier Loop Bh, called the high loop, and a coherent rectification assembly for rebuilding the envelopes the m (t) forms;

- a low loop B, for rebuilding the bit sequence (la

i cadence de bit) and

- one module EE, which the output signals of the two loops It uses and operates according to the principle shown in FIG. 3 to generate the signals 0, 1 and the synchronization signals to rebuild the TDCS pulse train.

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309828/0458 oricim *. _lw

UHlGiNAL INSPECTE »

If you now consider the high loop, it works like a classic arrangement in which a loop filter F and an oscillator 0 "of the voltage-controlled type are arranged after a multiplier 2, the latter controlling the second input of the multiplier M ₂ (possibly with the interposition of a logic divider following the frequency of the oscillator). This loop B enables the coherent rectification of the envelope of the received signal, ie the reconstruction of the pulse train. The loop is assigned to a multiplier M. and a 5f / 2 phase shifter in order to feed the assembly of the low loop B and the analog part JbE of the decommutator.

The low loop B has a structure comparable to the structure of the high loop B (multiplier M, filter F_ and oscillator O_): the loop is controlled by the periodic part of the signal that is characteristic of the bit sequence is.

man
If he directs his attention to the aim of the invention, one finds discrete lines in the spectrum of the random sequence which characterize the clock frequency of the bits. It is therefore possible to control a phase loop under this composite diode in order to provide the various control signals for the actuation of the integrators I _15, I ₉ and I_ at suitable times.

1 t J

The decommutator assembly identified above with EE again has the two chains already described in connection with FIG. 3; the two chains control a trigger flip-flop circuit Τ., which is a device R ₁ for the logical reconstruction

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j " ¹³ " 2300782

is connected downstream, which emits the signals O and 1. ^:

In order to obtain the synchronization signals S, which have the form a, b, e, f on line I in [of FIG. 4, the upper chain I ₂ - ■ A ~ is used together with a supplementary chain 1, -Vü ', which is structured analogously to the chain I ..- VD. The upper chain and the supplementary chain 'control a comparator C-, the integrator I ₃ integrating from T / 2 to 3T / 4. On the line II in FIG. 4, the change in the potential in the latter chain is shown in phantom;

S;

the generation of the synchronization signals sicii results without difficulty from the comparison with the generation of bits (0) and (1). The ■ synchronization signals (S) are generated with the interposition of a \

Triggerkippcnaltung T ₇ and an execution R ₀ for a logical

I!

Reconstruction generated.

Finally, FIG. 6 shows the error probability curves which are relevant in such a device, which is the focus of interest here. In the figure, the ratio E / N (dB) of the mean energy Έ radiated per bit and the spectral density of the noise N is shown on the abscissa (the noise being assumed to be white noise with a Gaussian distribution). On the ordinate, the fractional probability (b) for a bit error is plotted on a logarithmic scale.

who are independent.

Curve 1 shows the probability of a bit error in a decommutator according to the present invention,

309828/0458.-.- 1

but the control signals for the integrators are unremarkable (the loop B, has an infinitely narrow band); curve 2 is obtained under the same conditions, but with noisy control signals (signaux de commande bruites). These Curve has been plotted by taking the arithmetic mean of the points lying on the same vertical of curves 3 and 4 was calculated. Curves 3 and 4 correspond to the probability for "1" and "0", but taken separately.

^! It is clear that the implementation options described can only be assessed as examples and that it is entirely possible to make changes, in particular to use equivalent techniques.

j without deviating from the basic idea of the invention.

[In fact, many different ways of realization are possible which remain within the scope of the invention. For example, it is clear that practically the same result is obtained if, instead of multiplying by the factor 2 in the lower chain of FIG. 3, a division by 2 is carried out in the upper chain. Or the doubler VD can very well be omitted and this can be included in the integrator I .. if the elements of the integrator are selected in a suitable manner. It is also possible to omit the doubler and to integrate I ₂ from T / 8 to T / 4 in the integrator (for the bits 0 and 1). In general, one is not forced to integrate T-T / 4 and T / 4-T / 2 over the entirety of the corresponding period parts, rather it is sufficient if one integrates over a part-time; but it should be noted here that this is disadvantageous in terms of efficiency.

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Furthermore, you are not forced to double in VU to Deschränken. In general, it is only necessary that the excerpt of the the signal corresponding to the whole l / ert or type of information, -for the purpose indicated above- by comparing the impulse or; a series of rectified vibrations with a reference;

size is done. Thereby the impulse is determined by a value or the type of information of the impulse or the series characterizing} Part of its duration is integrated and the reference value is locally defined by ' Integration of the impulse or the rectified series of oscillations obtained over part of its duration which is not characteristic for the value or type of information is. The ver; the same is done with the help of means whose purpose is based on value

t i

OK the establishment of a reference threshold is what is necessary for a decision: about what kind of bit is necessary.

In the same way you can implement an inventive do commutators without relying on the TDCS standard; restrict. In this case the message is not necessary

! ι

made up of a sequence of pulses transmitted by a subcarrier

I \

are modulated. The message can randomly represent a value of the ^{information comprising at least 1} - at least two values or types; thej-

ν I

These impulses then all include in a period T a non-charac ^ · teristic part of the duration T / n; one of the information values comprises a characteristic part of the duration T / r (without overlap with each other part) and another information value includes a characteristic part of duration 0. Djbei η and r are numbers can be cut. In this case, the inventive gel commutator two fed in parallel

309828/0458

ORIGINAL INSPEGTEi

j Chains, one of which includes an integrator that in each period T during one of the non-characteristic part corresponding duration T / n integrated. This integrator forwards the integrated signal to a storage element, which the integrated Saves the signal until the end of the duration T / r. The other chain has an integrator that runs in each period T during the characteristic part corresponding duration T / r integrated. The chain also has a device for relative elevation of the signal fed in by the latter integrator compared to the signal of the other integrator. These two chains are connected to a comparator in which the above-mentioned comparison is carried out.

-17 ·

309828/0458

Claims (1)

■ Patent attorneys Dr. ing, H. Negendank Dipl Inc. H. H-ic'i-DiplPhys. W.Schmitz ; Dipl. Ing. E. Gru3i · - CIpI. ! ng. VV. Delusional j 8 Munich 2, Mozarfstrasse 25 Telephone 5 38 05 86 Center National d ¹ Etudes Spatiales ■ 129, rue de L'Universite January 5, 1973 Paris, France Legal File M-2478 Claims ί 1.J Remote control or analogue commutator that responds to a coded sequence consisting of a sequence of duration modulated impulses, i.e. impulses at their initial times have an equal time interval from a period T and their duration depends on the information content of the respective pulse changes, characterized in that the extract of the information corresponding logical signal by comparing the one of its information characterizing part of its duration of the integrated pulse with a x-reference variable takes place locally through integration of the impulse about one not charak- for its information; teristic part of its duration is obtained, with "the comparison is carried out with the help of institutions, which the AuFoau der Reference voltage threshold for a signal or bit based on a fourth U is used to determine the type of signal or bit. J2. Decommutator according to claim 1 for decommutating pulse trains, to follow. 309828 / 0468- " ¹⁸ "' which aleatorically represent one of at least two values or types of information, with all pulses in each within a period T comprising a non-characteristic part of the duration T / n, and the one of the information values a characteristic part of the duration T / r without overlap of the preceding part, another information value includes a characteristic part of duration O and η and r can be different numbers, characterized in that two chains fed in parallel are provided, the first of which has an integrator ^ I ₂ ), which is integrated within each period T during the duration T / n corresponding to the non-characteristic part and is connected at the output to a storage element (aJ, which stores the signal up to the duration T / x, and of which the second is an integrator \ lj which integrates within each period T during the duration T / r corresponding to the characteristic part, un d a device (VD) is provided for increasing the _{signal emitted by the last integrator (I 1} ) relative to the output signal of the other integrator and that the outputs of the two chains are connected to a comparator \ Cj which carries out the comparison. 3. Decommutator according to claim 1 or 2, for extracting the O bits and 1 from a message of the TDCS type, characterized in that the duration T / n corresponds to the time interval O-T / 4 within the period T and the duration T / r the time interval T / 4 - T / 2 within the Period T and that the device for the relative over- increase from a doubling ■ switched on in the second chain ler (vd) exists. - I. 4. Decommutator according to claim 2 for extracting the Synchrones at ions! - signals from a message of the type TDCS, characterized by ;, that the duration T / n corresponds to the time interval O - T / 4 within the; ^; ■ I J period T and the duration T / r the time interval T / 2 - 3T / 4 within: ! corresponds to half of the period T and that the device for relative overlapping consists of a switched on in the second chain ^; Doubler (vd) exists. ■ 5. Decommutator according to claims 3 and 4 for extracting the bits O and 1 and the synchronization signals of a message from type j; TDCS, characterized in that three chains fed in parallel; are provided, one of which has an integrator (I ₂ ) integrating in the time interval OT / 4, which works together with each of the other two chains, one of which has an integrator (I ₁ ) integrating in the time interval T / 4 - T / 2 and a doubler (VD) and the other one in time and tervall T / 2 - 3T / 4 integrating integrator (I,) ^{v has} a doubler (VD *), the cooperation of the first chain with the other two chains via comparators ^ C. or C ₂ ) takes place, which generate the information bits or the synchronization signals. 6. Decommutator according to claim 2, characterized in that the ι parallel Integrators of the two chains are controlled by rhythmic impulses ^v , which are restored from a dai clock of the bits 309628/0458 " ² ° constituting phase loop are derived. 7. Decommutator according to Claim 2, characterized in that each Impulse consists of a series of oscillations, and the impulses j before being fed to the integrators by means of a synchron rectifier (M ₁ ) are demodulated. J8. Decommutator according to claim 2, characterized in that each j impulse is made up of a series of oscillations and the impulses from the feed line to the integrators in one asynchronous rectifiers, e.g. of the diode type, can be demodulated. 9. Decommutator according to claim 2, for extracting the bits O and 1 from a message of the TDCS type, characterized in that the duration T / n corresponds to the time interval T / 8 - T / 4 within the period T and the duration T / r the time interval T / 4 - T / 2 within the that
Period T corresponds and the integrators are identical and that the device for the relative exaggeration has been realized in that the integration interval of the first integrator is limited to a duration T / 8. 10. Decommutator according to claim 2, for extracting the synchronization signals from a message of the type TDCS, characterized in that the duration T / n corresponds to the time interval T / 8 -T / 4 within the Period T and the duration T / r within the time interval T / 2 - 3T / 4 corresponds to the period T and that the integrators are identical and that this leads to relative exaggeration is that the integration interval of the first integrator has a length T / 8. 309828 / CUSa