DE1537027A1 - Data transmission system - Google Patents

Description

PATENT ADVOCATE λ J)

DIPL-ING. ERICH SCHUBERT -I OO / U * / T _Mon .. _m n _{) 3} 2 * »

Telegram addr .: Patichub, Siegen Postal check accounts: KölnlM »31, Ei« .n203ö Bank accounts: Deutsche Bank AG.,

Abi .. · Patent attorney Dipl.-Ing. SCHUBERT, S * Siegen, Eiterner Strasse 227 branches Siegen u. Oberhäuten (RhId.)

• ottfad) 32S.

'67 117 Fl / Schm / Ifs

U]

U] IiCiEHICAL lüDLdixtlUö LIMITED, 33 'Groavenor Place, London, 3.W.1., K η _: I a π

For this application, the priority is derived from the British patent application Mr. 57 481/66 of December 22nd , 1966 öeans ^ ruent,

Data transmission system

The invention relates to data transmission systems and in particular to eir.e such a system that is related to x * Dt ": en transmission via normal telephone lines, i.e. over switched lines of the Pernmeldetznetzes of the British Postoffice (B.P.0 »), which tone dialing tones / in-band signaling tones / able to transmit.

BAD ORWINAL

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• At the moment, the highest data transfer rates are _ «.; geoCnv. ^: L; .ai ^ - iceitsn üoer ordinary JeIci'onleitun _; .e ,, oCO. ^ ίπ, ο · ο- · 1 200 3aua with good conduct., e: i. ü'bortra ^ uiu ejguicüwi. up to 2 400 3su: i were reached when private (ge ::.: lines of higher quality al .; gewönniicna (: .. r; .. '.. it "Jelefonleitur.gen used v / uraen, -md aie Erx "inu : .i ..: iaraui ¹ aligned, a data transmission system to. · .. 3ic: ie an equivalent Geschv.'ir-di-.Keit of I; £ .tfc: nUber ^ ji ^r c_ung over ordinary x'elo_ 'onleitungen can reach.

Bevcr on dä3 v / esen aer according to the ürJindui. proposed JJA-reniibertragungcanlage nänsr received v / ira, eracneint it saciidienlich, aie various factors z ^ oeleuciiten which i..re Konstru.rtion ürden or iesciia-ienneit cesinflussen or impair v /, especially aie ilinscnränkungen caused by the limited rrequenzspeictruc i / aferle ^ t will:., which occurs in ordinary Zelefonleitunken.

? i- ·. 1 of the ieichnune, _is: t the ivrequenzspektrun an ordinary Telexonleitung. I / ti ^ Jrequer.z pe.-xruri j.ii _o t between 30.0 hertz and 3 400 Hz, but each data transfer in the higher frequencies of the "spectrum, ie from about 2430 Hertz s up to the higher frequency end of the opeictrums, would be subject to excessive distortion or shifting or distortion. In addition, the ϊοην / ahl requirements of the British Post Office / BPO in-band signaling requirements / allow frequencies between 2 130 Hertz and 2 430 Hertz and frequencies between 450 Hertz and 890 Hertz only

909851/0869

κ. / ei usable tapes left for data transmission, one tape, aas o-.ne \ reite / of 150 Lyklen \ .z \ :. Periods auf.vci ^ t, between: 30C and 45 ("Herta, UVi with or on aeia other z-ana, dt.s has a free υ of about 1 2GL cycles, zviscnen o ⁽ j0 Hertz. ·

■ nd 2 130 -i ^; rti :. The lower and sciual jjand is as lower

riückturaial / low-speed isburn cnaiinel / usable for κ, se aa * .. only the band of 120G ^ y cycles ireite in the x-iite of the ^ frequency spectrum for the transmission of weeding available o-zv /. is useful. 2Additional ^ .ici- to ooi en "i ecchraniciCii_ ^ n k. Mien aucii" uhterbruchunren or older FreiUv? Nzauscc. ', Lt: £ ·:: step that last a few milliseconds, and it kicks, a real, but ctarke Au ^ brüene of mpuisive noises or, ..auochen / ii ^ pulaive noise / on. Auiseraex ;. disfigured, f ^ lls the Leitun / irr / eraysteaie in sicxi sciilieiit, a slight a'requensverlf- ,. 3TUn ₁ . vcn transmitted bzv /. transmitted di ^ nals.

Jeae Daterübertra .. unrsanluve inuis kitiyl s. Show, uu die Datonaifcit-time. ^ Eberi'ate / - :; ata digit ti.;. Irie rate / ^ uf aer

iiiF-tiou for Ji>; € :: lv. ^r GCiC i.:t nor2: .c.lerv, '~ i3e in .-. en itrertra ^ enen deeds einresc ..: .. r; 3Gen lurch seiche I-Iethc-sn;.' ie 2 ... » ;?. ijlicc synchronize ie / i _: its, c.ie av.'isci.en den i: -fcrL. £ 'tiondat -.- ndirits receiLci?! -. ^"ula23t7 / ei;, EFÜ ^ t ^ ver e ::, uie Z.-j ^Jc::;... jitfrecL; .öi ::: _ c ::: '/ ri - rc; ii; iiTe data cer , \ -; sZ.c ~ ^ Jcaieren for ^ snü ^ ence

bad ογ? ι ^. λι *> 9 0 9851/086 9 - ^Ηί

May require continuity of the timer information, oaer äurcj; Use before. Pilot tone signals.

A transmission line with a given amplitude / frequency unit, distortion or shift, has a much smaller effect on each of η channels of a bandwidth B / n than it would on a channel of a bandwidth B. It is therefore desirable to use as many channels as later on for data transmission without making the system too complicated and too expensive. The fooaulationsrete of each channel would have to be reduced by a factor, which would correspond to the number of channels; this can, however, be achieved by transmitting that number of data digits simultaneously. As the number of modulation levels in each channel is increased, more digits of data can be transmitted simultaneously and the overall bandwidth is reduced. In turn, this would increase the required oil-signal-to-noise ratio on the line. Therefore a compromise must be made between:; he resulting heduction in the Effects of distortion, etc. Distortion and the increased complexity and noise sensitivity.

Under consideration of the previously explained - '' aktorer- scnafft die ürinaun :. ' a data transmission system, in v / elc / ier - on the end of the system - data digits

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aur transferuii .; in 3erienformati.cn / serial formation / appear and successive numbers / numbers / eier oJate ^ ui in successive groups of legs after / in turn / registered o:.: w. followed by parallel Dai'teilui ^ the digits of each group u: ia the coding of the digits of each group as a whole, as presented in parallel, into a code that translates into a code with respect to each of a number of groups having skanälen entiKreciiende code signals indicating the one of a number of ion rjiögl ^ u ..: be xituaen in v; elchen these code signals in their eiiteprucencieri i-ai.i using üeitentandübertra..un- _t .. üt9rxr.i-. . _c ; on weraen, and in veloner Hittel on aer En: pfan ^ sseite of the plant before /. = see sina for demo el uli er en cq £ deiteublinder, u .. lie Oo-'leji ^ n.-. le with corresponding amplitude ruciisubilie :. b.:·. '. 'wieierhorsiistteile, and smocks are provided for the decoaiereii aar codesi ^; - e, among other things, the original ^ original) data aigits are restored.

Yorsugweise v. '

sideband transniisaion / for the transmission of code signals is used, i.e. a transmission in which a deitenoana a double sideband modulation envelope / as a unity to a ... to £ .rei: zerider. r.sst is transmitted along the other sideband, so that the transmission the! carrier frequency eii-schlieat. So-; it iiar.n e

5AD 909851/0869.

Data transmission system according to the invention has two vestigial sideband channels use one to transmit the lower sideband next to the carrier frequency of the channel and the another to transmit the upper sideband adjacent to the carrier frequency of the channel.

It can be arranged so that the difference between the two carrier frequencies of the two channels can contain information for effecting synchronization of the receiving side with the transmitting side of the system. Since amplitude / frequency and delay / frequency distortion are likely to be a minimum in the middle of the channel, it is preferred to locate the accurately spaced carrier frequencies close together in this area, thereby reducing the distortion or shifting of the synchronizing information between the transmitting side and the receiving side is reduced to a minimum compared to conventional methods in which additional pilot tones are used which are located at the band edges where excessive distortion occurs. For example, the system can use two residual sideband channels which have corresponding carrier frequencies that are 100 Hertz apart. Palis then the code signals are configured for transmission in each of the two channels so that they ^each: comprise of three possible amplitude levels, a total of 3x3 = 9 different combinations may be transmitted from ^T Godesignalen in the two channels. This enables the

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-Y-

created the ability to group data digits in dinar form third or to be coded in groups of three, namely by adding eight of the combinations of the code signals to the eight possible Assigns combinations of three binary digits. This makes one of the code signal combinations is superfluous: if one of the three amplitude levels of the code signals is zero, then the superfluous dzw. excess code signal combination the combination that is / made up / from a code signal of flullamplitude in each of the two channels.

So that the invention is expressed even more clearly will now be used to reproduce it, for example Reference drawing, namely shows

Fig. 1, as already mentioned above, the frequency spectrum of an ordinary telephone line,

Fig. 2 shows an exemplary frequency arrangement for a Data transmission system / data transmission system / according to the invention while

3 shows a block diagram of an exemplary embodiment of a data transmission system reproduces according to the invention.

Fig. 2 of the drawing shows an exemplary frequency arrangement for a data transmission system according to the invention, in which code signal combinations three amplitude levels in each of two channels, for a transmission speed. '

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speed of 2,400 baud reduces the grouping of data digits in Dreier / into three's / for the transmission, which facilitates this coding, the modulation rate for which each channel has to take care of or which each channel has to deliver, to only 800 elements / sec. The bandwidth of each channel is therefore 4-00 Hertz. If you accordingly, for example, practical filter network. works used to transmit at 0.8 times the Nyquist signaling rate / Nyquist signaling -rate / with single sideband modulation over a frequency ratio of 10: 1, the transmitted energy in each channel extends over a band of 550 Hertz, as shown in FIG. That transmitted signal is therefore contained within a total frequency load of 1100 Hertz, which has the effect of severe distortion / distortion / at the edges of the channel bands. Carrier frequencies of HOO Hertz and 1500 Hertz are used for the two channels used. These provide a total band between 900 Hertz and 2000 Hertz, which is the in-band signaling frequencies or tone selection frequencies / excludes in-band signaling frequencies /. A carrier frequency of 1600 Hertz for one of the channels was avoided because this frequency is a harmonic of the modulating frequency and could cause interference at the receiving end or on the receiving end of the system. The remaining sidebands ignale / vestigial sideband signals / are expediently through quadrature modulation using identical Phase shift networks for "both channels in both the transmitting end and the receiving end are generated. Carrier signals Carrier signals in phase quadrature or phase-shifted by 90 ° can be generated digitally.

909851/0869

A sideband rejection on the order of 35 db. was considered appropriate; so became phase difference networks fourth order is used, this having better suppression p "ls 35 db. between about 50 Hertz and 550 Hertz of the associated Carrier frequency yield away.

Timing signals / timing signals / must be on both the Sending side as well as on the receiving side of the system in a sol- φ ought to be produced in such a way that they are in the same fixed phase relationship to the difference between the two carrier frequencies.

A block diagram of an exemplary embodiment of a The data transmission system according to the invention is shown in FIG. 3, which will now be discussed in greater detail. Suppose that this system has the special coding and frequency arrangement. statements discussed above.

The transmitting end or the tail end of the system points a coder / encoder / 1, the input data / input data / are transmitted for transmission, whereby the input data in the form of binary digits are provided, which are fed continuously or one after the other / serially / into the coder, namely with a Speed of 2,400 bits per second. In the coder a 3 ^ bit shift register / 3-bit shift register / is arranged to the

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to group received "binary digits in successive groups of three or * groups of three. The shift register expediently has three cascade-connected / bistable stages and is controlled in its mode of operation by Vtechseliiipulse or shift pulses / shift pulses /, .... which are transmitted to him via a wire 2 from a timing generator or timer / timing generator / 3. ie 2,400 pps / pps / are fed in, delayed by a fraction / fraction / relative to the bits, so that they are not coincident with transitions / in the bits or with bit timing pulses or bit pointer pulses which the shift pulses occur concurrently or simultaneously , as it is supplied by the states of the bistable stages thereof, by means of a binary to trinary conversion logic circuit / by a binary to trinary conversion logic circuit / sampled / sampled /, which expediently has a plurality of / coincidence gates that are connected, to receive the shift register output and which are connected to each other in order to control the states of four other bistable circuits or circuits depending on this output, which are all driven together by clock or time pulses / driven in common /, which are applied to it by the timer 3 fro via a wire 4 and a P _u lswiederholungsrate 800 Pps include, ie, a rate which is one third of the rate

909851/0869

determines with which the ^ iming bits are fed after the coder. In this way, the binary digits are successively grouped into parallel groups of three, and the groups of three 3in digits are presented for coding following the emergence of successive clock pulses. The coding used for each group of three binary digits consists, as already explained above, of zv / ei Oodesignals, each having one of three possible amplitude levels. In order to effect this coding, each of the four wiser bistable stages can control an individual gate, M through which a positive or a negative G-sharp voltage, depending on the control applied to the gate by means of the bistable stage in question exercised, can be directed. An adding circuit / addine circuit / for each of the two transmission channels is set up in such a way that it is driven either by such a positive or negative current voltage or by a ^TT ullsp-innunfr, but not by positive and negative DC voltage en -remeinam, so that. the output from the coder consists of two codesi <? n'-len P and Q, with \ average Snannun ^ en / mean voltages / of ^ uIl. If the mean voltage of each code signal is made somewhat different than zero / something other than zero /, a proportional carrier frequency expression appears in the modulator output of each of the two modulation arrangements, according to which the code signals are applied accordingly, which is explained below. Carrier components in the transmitted signal are generated by adding a direct current bias voltage to the code signal voltage, which corresponds to the signal voltage gena, u or is somewhat greater than ^c ls.

909851/0869

The two code signals P and Q generated by the encoder are corrected by means of a corresponding delay-corrected low-pass filter 18 and 19, which serve to keep their frequency spectra within 500 Hertz to keep to appropriate hodulation arrangements 5 and 6 created. Active RC filters / active HC filters / would be for this low-pass filter is suitable. Each of the two Iodulation arrangements 5 and 6 is expediently a quadrature modulation arrangement which has 90 ° phase difference network means to which the relevant Code signal is applied jointly / in common /, two modulators, which are fed accordingly, two 90 out of phase Versions of the relevant code signal as indicated by the 90 ° phase difference network and a combining (adding or subtracting) circuit to which double sideband outputs of the two modulators for additive or subtractive combination, depending on which, can be applied jointly to a to generate a lower sideband with respect to the channel Q and an upper sideband with respect to the channel P (see FIG. 2). Carrier signals of frequencies f 1 and f 2 tffr the two channels are through the

c c.,

Timers 3 are generated, preferably by digital techniques or methods, and are correspondingly according to the two hodulation arrangements Rides over veins 7 and 8. Within each blodulation arrangement two versions of the relevant carrier signal that are phase-shifted by 90 ° are applied to the two modulators, such as required for quadrature modulation.

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. It should be noted that the GDe ictistrornomponents of the two code signals Γ and Q from coder 1 as far as the both modulation arrangements 5 and 6 are kept / preserved / must, moreover, these two modulation arrangements must be duplicated are balanced / double balanced /, because the low-pass filter outputs, i.e. the code signals as passed by these filters move into the frequency band of an ordinary telephone line extend over which, it is assumed, transmission takes place target.

The timer 3 can be set so that a 90 ° phase-shifted versions of the two carrier signals as PhasengleicHeits- and quadrature square wave in-phase and quadrature square waves / on the carrier frequencies f 2 / and f 1, corresponding to 1 400 Hz and 1 500 hertz · In addition, the timer 3 »wit echon mentioned above, generates two pulse trains or chains, namely one of 800 P« ps, in order to carry out the serial to parallel conversion / the binary digits to control by means of the coder, and another of 2 400 Pp8. to drive the shift register in the coder and create or deliver bit timing information / output · The pulse train of 800 Ppβ. must be in a fixed phase relationship with four times the difference "between the frequencies of the two carrier aales"

. These outputs, which are required by timer 3, could with the help of mixers / and by means of matching

6AD 909851/0869

matched circles and filters achieved; become, abor this' before- ^; 'Driving can be risky if nose requirements or queries are strong / stringent /. Therefore, a dir it al · © method for generating these outputs is viewed as a better solution: the transmission disk of the solutions also includes a master oscillator / 9 »which provides a constant frequency signal generated, which is suitable for driving digital counters or counting devices / digital counters / in the timer 3, which the pulse trains and Ί! generate rager signals that are required.

The single sideband outputs TOn of the two modulator arrangements 5 and 6 are applied via an adder 10 for transmission via a line 11 which connects the transmission side of the system with the reception side. On the receiving side of the system, the received transmission is applied jointly to two constant volume amplifiers 12 and 13 which feed respective demodulation arrangements H and 15, each of which has a pair of modulators and 90 ° phase difference network means as required for quadrature demodulation. The two modulators in the demodulation Hf which is part of the P-channel are accordingly by 90 ° phase shifted "versions of the! Präger signal of the frequency f _Q \ driven, and the two modulators in the demodulation arrangement 15, which is part of the Q-channel, are correspondingly driven by 90 ° phase-shifted versions of the carrier events de * Frequena f _ö 2 local oscillators 16 and t7 are provided for generating these two carrier signals, which are in frequency and in phase with

909851/0809

Controlled by means of synchrodyne / synchrodyne / arrangements which are the direct current levels at the outputs of the demodulators in each of the two demodulation arrangements as a display or «indication of the relative phase of the incoming carrier signal and ' of the corresponding demodulating carrier signal. utilize. This synchrodyne method was preferred to the more direct one Extraction or replacement / extracting / of the incoming carrier signals with or through fixed tuned circuits / fixed tuned circuits / chosen because all the phase shifts caused by the matched or voting groups were introduced in which demodulated outputs occur or would appear.

The bit and code signal timing pulses of 2,400 P.p.s. respectively. 800 p.p.s. are regenerated by means of a timing regenerator 20, which for this purpose another phase-locked oscillator aufwei.it, which runs at the digital rate, i.e. 2,400 Hertz, and its frequency first by three and then by another eight is divided to provide a signal of 100 Hertz. One of the locally generated carrier signals is locally generated by the other Carrier signals modulated to provide a frequency of 100 Hertz, which corresponds to the difference between the carrier frequencies. These two 100 Hertz signals are modulated together, to provide a DC signal proportional to their phase difference, and this DC current is used to set the frequency of the 2,400 Hertz oscillator. Pulse trains from 2,400 p.p.s «and 800 p.p.s are thereby achieved.

909851/0869

The re-formed or restored code signal outputs from the two demodulation arrangements H and 15 are forth considerably disturbed or distorted by band limitation, delay / frequency distortion, amplitude / frequency distortion, Noise /, carrier residue / carrier leak /, etc. Therefore, they are not suitable for decoding as they are / as they stand /.

The reconstructed or reconstructed code signals are transmitted via wires 22 and 23 to height decision circuits / level decision circuits / created in the decoder. Any altitude decision circuit contains two trigger circuits, for example Schmitt triggers, and the combination of their rises, indicates which of the three possible heights is at any point in time the signal is located. The outputs of all four Schmitt triggers are sampled using the 800 P.p.s. code signal timer pulses, which from the timer regenerator / timing regenerator / 20 connected via wire 24- and the scanned outputs a decoding logic matrix / decoding logic matrix / created. The matrix has three output terminals that be connected accordingly with three consecutive or successive bistables of a shift register * The appearance of a Pulse at any one of the matrix outputs in the aforementioned Sampling time selects / presets / the corresponding bistable, and to; the three bistables are preselected for each sampling time, um, 'the three digits represented by the received signal elements be included. The register is at the digitrate

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tented / clocked / by the bit timer pulses that are applied to the decoder 21 from the timer regenerator 20 via wire 25, so that between the scanning of consecutive signal elements the binary data / binary data / through a fourth bistable in the shift register successively / 'iarially / is read out or read. The output of the fourth bistable is a stream or beam of serial binary data at 2-400 bits / sec, corresponding to the input data fed in on the transmission side of the system .

It can be clearly seen that a data transmission system according to the invention can be used as a simple method of automatic equalization / equalization / is suitable for heavily disturbed lines, which could be introduced into the plant without any difficulty, if desired. The equalization means would be used to Line to be equalized immediately as soon as the connection between the system and the line is established, whereby the data / data / for the transmission are maintained until satisfactory conditions are achieved while the equalized condition is in that state is "locked" / "latched" for the duration of a transmission.

Another possibility with a system according to the Invention ordered that switching means could also be built into it to reduce the speed of transmission, about 1,200 baud with very low-profile lines, while others Sahaltmittel could be introduced to increase the speed to increase the transmission for good lines considerably, for example, the data transfer rate could be up to 4,800 baud on a private (rented) line.

909851/0869

A data transmission system according to the invention can be built using digital circuits which are so arranged are that they fulfill generally known logical functions. The analog parts / analogue parts / of the system, as for example the modulation and demodulation arrangements could be made using a thin film integrated circuitry.

The invention also relates to modifications of the enclosed Claim 1 outlined embodiment and relates above all to all of the invention features, which in detail - or in combination - in the entire description and drawing - are disclosed.

Claims

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Claims (6)

DIPL-ING. BRICH SCHUBERT _ίΛ w * », f O valley gram addr .: Patuhub, Swe «t ^ Poittdwckkonhtnt K6ln 104931, Ε »· η20362 Bank accounts: Dcutsdw Bank AG., Abi. = Patent attorney Dipl.-Ina. SCHUBEITT, 59 Sieo «n, Eiierner Slrao · 227 branches Si« o «i and Ob» r »ioui» n (RhId.) P.O. Box 325 67 117 71 / Nb December 20, 1967 Claims Data transmission system, characterized in that at the transferring end of the system it has means which are based on dot digits for address the transmission in series or 'series formation occur, for the registration of successive numbers of these data digits in successive groups one after the other, means, the digits to present each of the groups in parallel, means for encoding the digits of each group as a whole, as presented in parallel, in a code therein relating to each of a plurality of transmission channels the system has corresponding code signals which have one of a number of possible amplitudes, and means for transmitting these code signals in their respective 'channels by means of sideband transmission and that the system also has a receiving end of the system means for demodulating the sidebands in order to restore the code signals with a corresponding amplitude, and means for decoding the code signals to restore the original data digits. 2. Data transmission system according to claim 1, characterized in that that for. the transmission of the code signals remaining sideband transmission * '■ / · is used. .-'..- ■ eA COPY 909851/086 ^ - r ^ r ^ -vi. _-- ■ 3. Data transmission device according to claim?., Characterized in that two Restseitenb-ndkanäle, one for transmitting the lower sideband next to the carrier frequency of the Konais and the other for transmitting the upper sideband next to the carrier frequency of the channel are used. 4 · Data transmission system according to claim "f, characterized in that that the oodesign-ile for transmission in each of the two channels so arranged, let them be any of three possible amplitude levels -show. • 5. Datenllbertragungsanlage according to claim 4-, characterized in that data digits in ^ inärform thereby in groups of three or in groups of three are coded so that eight of the different possible combinations of the two code signals are eight possible Combinations of three "^ inardigits can be allocated. 6. Data transmission system according to claim 2 to 5 »characterized in that that means on the Brapfang3seite the difference respond between the two carrier frequencies of the two channels to a timing signal in accordance with said difference su produce, to the district of oynehronisötion of the receiving side : r.it the '' e ^ deseite of the occasion. 909851/0869 Blank page