DE2339806C3 - Messaging system - Google Patents

Description

md or frequency divider are provided by means of de ico «ii carrier frequencies, the bit image frequency Can be derived from digital signals.

With the message transmission system according to the [ikuptpatent] it is therefore possible to use a carrier-equilibrium connection to transmit analog and digital signals in parallel. It comes to a mutual Influence that affects the analog signal in particular and increases the Cross-talk noise caused by crosstalk of the digital Signal expresses. There is therefore a demand for the lowest possible level for the digital signal.

Since the main energy of a random bit sequence of the digital signal lies in the lower frequency range, A level reduction is required especially for this frequency range. This stands for the increasing frequency Cable attenuation against, so that for the shift of the digital to be transmitted Signal after higher Irequenzen a compromise has to be found.

According to a particularly favorable embodiment of the main patent, there is therefore an implementation of the digital signal on the sending side by half the bit rate and on the receiving side a corresponding one Repositioning. When implementing on the sending side, a number of considerations must be made note. If the implementation is more appropriate in a single step through modulation with the help of a carrier Frequency made, then the modulated output signal appears partially in the same Frequency range like the digital signal to be modulated at the input, so that the two signals are separated is not possible and therefore both signals appear on the output side.

It is therefore usually a double conversion, i.e. the successive modulation with two carriers of different frequencies made. By modulating with the first relative High-frequency carriers are created with a sufficient frequency spacing from the original band two high-frequency sidebands, one of which is filtered out with the help of a bandpass filter. Through modulation this screened out sideband with a frequency-wise neighboring carrier is slightly higher Frequency, along with other modulation products, results in a relatively low-frequency signal band in the desired frequency range. It can be seen that the double implementation described requires considerable effort.

The invention is therefore based on the task of reducing the effort involved in converting the digital signal to decrease. When solving the problem, 2U must also take into account that the modulated digital signal should be directly regenerable on the transmission path and that, for example, a pseudo-ternary coded Signal after modulation should be available again in pseudo-ternary coded form. This is done taking into account the energy distribution in pseudo-ternary coded signals, through which the transmission of digital Signals in pseudo-ternary coded form is particularly advantageous.

The object is achieved according to the invention in that a rectangular pulse train with half as a carrier Bit rate is derived from the bit rate of the digital signal and the zero crossings of the pulses of the digital signal and the carrier are shifted by an ° op <n> n each other. In advantageous Way, the conversion of the digital signal into the desired frequency range is carried out by a single Modulation with a single carrier using the digital character of the signal to be converted.

A particularly favorable variant of the invention results from the fact that the modulator to be modulated in the modulator digital signal and that in the form of a sequence of square-wave pulses with positive or negative

ίο Amplitude present carriers so linked be that if the digital signal is lost, no output variable is independent of the carrier amplitude is given that if the carrier is no longer available, regardless of the amplitude of the digital Si

If there is no output variable, that is when the amplitude of the digital signal is positive and the amplitude is positive Amplitude of the carrier a positive amplitude value is given as an output variable that with a negative one Amplitude of the digital signal and positive amplitude

»Ο tude of the carrier a negative amplitude value than Output variable is given that with a positive amplitude of the digital signal and a negative amplitude of the carrier has a negative amplitude value than Output variable is emitted and that with a negative amplitude of the digital signal and a negative amplitude of the carrier a positive amplitude value is emitted as an output signal.

The message system according to the invention can be set up in a particularly simple and clear manner.

provided that the signal quantities are voltage quantities acts and thereby the known digital circuit arrangements can be used.

A particularly simple and easy to implement

digital system consists of a modulator, which is built like a digital double push-pull modulator and a first pair of input terminals for the digital signal, a second pair of input terminals for the carrier, four NAND gates, two AND gates, an output transformer and two signal outputs contains and in which the first input of the first gate with the first input for the digital Signal is connected, the second input of the first gate is connected to the first input for the carrier is, in which the first input of the second gate with the second input for the digital signal is connected and the second input of the second gate is connected to the second input for the carrier is, in which the first input of the third gate with the second input for the carrier and the second input of the third gate is connected to the first input for the digital signal in which the first input of the fourth gate with the first input for the carrier and the second input for the fourth gate is connected to the second input of the digital signal, in which the output of the first NAND gate is connected to the first input of the first AND gate. at which the exit of the second NAND gate is connected to the second input of the eiiten AND gate in which the Output of the third NAND gate is connected to the first input of the second AND gate, at which the output of the fourth NAND gate is connected to the second input of the second AND gate where the outputs of the first and the second

th AND gate each connected to one terminal of the primary winding of the output transformer are, in which the outputs for the output signal each with a connection for the secondary winding

tics output transformers are connected iitni at the Connections for the power supply are provided.

With reference to the embodiments shown in the drawing the invention is to be explained in more detail below. It shows

Fig. 1 is a schematic representation of a message transmission system according to the main patent.

2 shows the voltage curves of the to be modulated digital input signal, the carrier and the modulated output signal.

Fig. 3 shows the spectral distribution for the pseudo-ternary coded signal of a random sequence before and after Modulation,

4 shows the schematic representation of a digital double push-pull modulator according to the invention and

Fig. S shows the circuit of a digital double push-pull modulator according to the invention.

Fig. 1 shows a terminal I, intermediate stations II and III and another terminal IV of the communication system according to the main patent the end point! to the terminal IV are necessary.

The terminal I contains a source 1, a modulator 5, a source for the transmission of digital signals Frequency filter 7 and a frequency divider and / or frequency multiplier 12. For the transmission of carrier frequency The terminal I contains a source 15 for analog signals

The intermediate point II contains a demodulator 9, a regenerator 2, a modulator 6, a frequency filter 8 and a frequency divider and / or frequency multiplier 13 for the transmission of digital signals. The intermediate point II contains an amplifier 16 for the transmission of carrier-frequency analog signals.

The intermediate point III contains an amplifier 17 for the carrier-frequency transmission of analog signals and a line amplifier 3 for the carrier-frequency transmission of digital signals in each case on a two-wire line.

If the amplifier or regenerator distances for the transmission of the converted digital signal are smaller than the required amplifier distances for the transmission of the carrier-frequency analog signal, then the intermediate point II or III instead of the amplifier 16 or 17 contain frequency filters to avoid crosstalk between the two-wire lines Feedback from the output to the input of the digital cable run.

The terminal IV contains a demodulator 10, a regenerator 4 and a frequency divider and -Multiplier 14 for receiving the digital signals. The terminal IV also contains a receiver 18 for carrier-frequency analog signals.

The terminal I is connected via the intermediate sections II and IH with the terminal parts IV by multi-pair transmission pairs 11 Implementation will be postponed in terms of their frequency. The carrier frequency or carrier frequencies required for this are derived from the bit rate / digital signals by means of the frequency multiplier and / or frequency divider 12. The output signals of the modulator 5 are fed via the frequency filter 7 and a two-wire line of the cable 11 in the intermediate point II to the demodulator 9 at the same time as the carrier frequencies derived from the frequency of the digital signal via the frequency multiplier and frequency divider 13. The recovered digital signal is regenerated in the regenerator 2 and then modulated in the modulator 6 onto the carrier obtained by the frequency multiplier and frequency divider 13. The output signal of the modulator 6 is fed to the intermediate point III via the frequency filter 8 and a two-wire line of the transmission cable 11.After amplification in the line amplifier 3, the signal arrives at the terminal IV via a two-wire line of the cable 11 at the same time as the frequency multiplier and frequency divider 14 The carrier frequencies obtained from the bit sequence of the digital signal to the demodulator 10 and via this to the regenerator 4, from which it can be taken. The following statements relate mainly to a further development of the modulation method and to correspondingly designed modulators which can be used in the described communication system as modulators 5, 6 in the terminal I and the intermediate point II .

FIG. 2 shows the phase relationships between the digital input signal to be modulated £ 1. the carrier El and the modulated digital output signal P shown. It can be seen that the digital input signal E1 to be modulated and the modulated output signal P can assume the amplitude values + 1.0, -1 and are present in pseudo-ternary coded form, while the carrier E1 is a square pulse train, the amplitude of which has the values +1 and can assume -1.

3 consists of two parts, the first part shows the spectral distribution of a pseudo-ternary coded digital input signal and the second part shows the spectral distribution of the output signal which is also pseudo-ternary and converted into the higher frequency position. In both cases, the solid line shows the voltage level, that is, the energy distribution of a random sequence as a function of the normalized frequency; In addition, a number of periodic sequences are marked, of which the sequence labeled χ is particularly noteworthy, which indicates the signal during the pause in speech. The comparison shows that the range of maximum levels and thus maximum! Energy was shifted to higher frequencies by the modulation, so that the maximum crosstalk range was also shifted to higher frequencies. This is especially true for the additional periodic sequences shown, which occur with such! Considerations are often neglected, although su are often particularly disturbing due to their high level.

FIG. 4 shows the schematic diagram of a digital double-balanced modulator according to the He invention with a first pair of input terminals 21 22 for the ESTC input El, a zweitei terminal pair 23, 24 for the second Eingangsgröß El and two signal outputs 25, 26 for the Off

input variable P. If one carries such a circuit according to the method according to the invention as input variable £ 1 the voltage of a signal encoded in a pseudo-ternary code with full-bit-wide square pulses and at the same time as input variable E2 a square-wave clock signal voltage with the clock ratio 1: 2 and half the bit rate of the pseudo-ternary Signal, the output variable P obtained is the voltage of a signal which is also pseudo-ternary coded. If, according to the method according to the invention, the zero crossings of the pulses of the input signal El to be modulated and the carrier £ 2 are shifted from one another by half a bit width, then each zero crossing of the rectangular pulse train of the carrier £ 2 lies in the middle between two zero crossings of El. The level of the pseudo-ternary coded and modulated output signal P at frequency 0, that is to say with direct current, is thus the same as that of the input signal to be modulated, i.e. also equal to 0.

Fig. 5 shows the embodiment of a digital double push-pull modulator according to the invention, the from 4 NAND gates, 2 AND gates, 4 input terminals 21, 22, 23, 24, one output transformer and interconnections exist. With a digital double push-pull modulator constructed in this way it is useful to first split the incoming pseudo-ternary coded input signal E1 into two unipolar Split pulse trains El 'and El ", where £ 1' contains only the positive and El "only the negative pulses of the input signal. The pulse sequence El 'becomes then the input terminal 21 and the pulse train El "is fed to the input terminal 22.

From the square-wave clock signal of the input ^ 5 output variable E2, an inverted square-wave clock signal is derived, the input terminal 23 the original square-wave clock signal and the input terminal 24 the inverted square-wave Clock signal are supplied. The signals are sent to the inputs from the two pairs of input terminals of the 4 NAND gates, namely the signals of the first input terminal 21 each to one Input 71, 92 of the first and the third NAND gate 27, 29; the signals of the second input terminal 22 each to an input 81,102 of the second and the fourth NAND gate 29, 30; the signals from the third input terminal 23 to the other input 72, 101 of the first and fourth NAND gates 27, 30 and the signals of the fourth input terminal 24 to the other input 82, 91 of the second and third NAND gates 28, 29. Corresponding to the known Function of the NAND gates, the supplied signals are linked to one another and are available available in linked form at the outputs of the respective NAND gates. Then be the signals from the output of the first NAND gate 27 to one input 111 of the first AND gate 81, the signals of the second NAND gate 28 to the second input 112 of the first AND gate, the signals of the third NAND gate 29 to the first input 121 of a second AND gate and the signals of the fourth NAND gate is fed to the second input 122 of the second AND gate. Accordingly the well-known link in the AND gates creates new output signals from the output of the two AND gates are each fed to one terminal of the primary winding of an output transformer 33 will. The secondary winding of the output transformer is connected to one of the two signal outputs 25, 26, from which the output signal can be taken off in symmetrical form can. The output transformer can be replaced in the usual way by known push-pull circuits. In the present case, the power supply to the digital logic gates is via one here Center tap, not shown, of the primary winding of the output transformer.

To further reduce the low-frequency components of the modulated output signal in particular, the output terminals of the digital double push-pull demodulator according to the invention can be connected to a bandpass filter with a pass band between the normalized frequencies Ω = 0.5 and Ω = 1.5. The modulated digital output signal is thus obtained in analog form, which is fed to the other parts of the communication system in accordance with the main patent.

For this purpose 3 sheets of drawings 709 622/232

Claims (4)

Patent claims: 1. Message transmission system with two terminals, which may be triggered by amplifiers and / or intermediate pieces containing regenerators, interrupted multi-pair symmetrical or coaxial cables are connected are, of whose two-wire lines at least one of the carrier-frequency transmission of analog signals and at least one is for the transmission of digital signals, and each Source for digital, especially pulse code modulated Signals in the transmitting part of the terminal and each regenerator in the intermediate points a modulator is connected downstream, in which the digital signals through carrier-frequency conversion into a Frequency position above the carrier frequency band tier analog signals are shifted that each A known frequency filter ao is connected downstream of the modulator. that in the receiving part everyone Terminal and each intermediate point with a regenerator, a demodulator is provided for reverse conversion is and dali in the end points and the intermediate kitchens with regenerators frequency multipliers and or frequency dividers are provided, by means of which the carrier frequencies from the Bit rate of the digital signals can be derived according to claim 3 of the patent 2318800, characterized in that the carrier is a square pulse train with half the bit rate from the bit rate of the digital signal is derived and the zero crossings of the pulses of the digital signal and the carrier are shifted by 90 ° against each other 2. Message transmission system according to claim 1, characterized in that in the Modulator the digital signal to be modulated and in the form of a sequence of square-wave pulses carriers with positive or negative amplitude are linked to one another in such a way that that when the digital signal disappears, no output variable is independent of the carrier amplitude is given that when the carrier disappears regardless of the amplitude of the digital signal No output variable is given that with a positive amplitude of the digital signal and more positive Amplitude of the carrier a positive amplitude value is given as an output variable that if the amplitude of the digital signal is negative and the amplitude of the carrier is positive, a negative one Amplitude value is given as an output variable that with a positive amplitude of the digital signal and negative amplitude of the carrier a negative cr Amplitude value is given as an output variable and that with a negative amplitude of the digital signal and negative amplitude of the carrier a positive amplitude value as the output signal is delivered. 3. Message transmission system according to claim 2, characterized in that it is at the signal quantities are voltage quantities. 4. modulator for the communication system according to claim 3, characterized in that that a digital dual push-pull modulator is provided which has a first pair of input terminals (21, 22) for the digital signal, a second pair of input terminals (23, 24) for the carrier, four NAND gates (27, 28, 29, 30), two AND gates (31, 32), one output transformer (33) and contains two signal outputs (25, 26) and at dom the first input (71) of the first gate (27) tired first input for the digital signal, 21) is connected, the second input (72) of the first Gate (27) is connected to the first input (23) for the carrier, in which the first input (81) of the second gate (28) is connected to the second input (22) for the digital signal and the second input (82) of the second gate (28) is connected to the second input (24) for the carrier, in which the first input (91) of the di itten gate (29) with the second input (24) for the carrier to 'the second input (92) of the third gate (29) is connected to the first input (21) for the digital signal. where the first input (101) of the fourth gate (30) with the first input (23) for the carrier and the second input (102) of the fourth gate (30) with the second input (22) of the digital signal is connected, in which the output of the first NAND gate (27) to the first input (Hl) of the first AND gate (31) is connected, with 'learn the output of the second NAND gate (28) is connected to the second input (112) of the first AND gate (31), in which the Output of the third NAND gate (29) to the first input (121) of the second AND gate (32) is connected, in which the output of the fourth gate (30) with the second input (122) of the second AND gate (32) is connected, in which the outputs of the first and the second AND gate (31, 32) each with a connection of the primary winding of the output transformer (33) are connected, in which the outputs (25 26) for the output signal each with a Connection for the secondary winding of the output transformer (33) are connected and at the connections for the power supply are provided. The main patent relates to a communication system with two terminals, which may be through interrupted by amplifiers and / or regenerators containing intermediate points multi-pair symmetrical or coaxial cables are connected, of the two-wire lines at least one of the carrier-frequency transmission of analog signals and at least one of the transmission of digital signals is used, and with each source for digital, in particular pulse code modulated signals A modulator is connected downstream of each regenerator in the intermediate points in the transmitting part of the terminal is, in which the digital signals through carrier-frequency conversion in a frequency position above the carrier frequency band the analog signals are shifted so that each modulator is followed by a frequency filter known per se, that in the receiving part a demodulator is provided for reverse conversion at each terminal and each intermediate point with a regenerator is and that in the terminals and the intermediate points with regenerators frequency multipliers