DE1089427B - DC controlled AC modulators - Google Patents

Description

GERMAN

The invention relates to a modulator circuit for the conversion of binary direct current signals into alternating current emergency signals, especially for alternating current telegraphy with amplitude modulation or frequency modulation.

Modulators are used very frequently in modern telegraphy transmission technology. they are for example an essential part of many relay replacement circuits. So has to go to the electronic Replica of a polarized telegraph relay the requirement to be made that input and output circuit are galvanically separated from each other. For this purpose the incoming DC characters are used converted into alternating current symbols with the help of modulator circuits in the input circuit, which are then inductively, i.e. galvanically isolated, transferred to the output circuit and rectified again will.

In the case of alternating current telegraphy transmission, it is known that either a keying of the amplitude takes place a frequency (single tone system, amplitude modulation) or keying between a frequency and another frequency (double tone system, frequency modulation). This will also be done in large Scope of modulator circuits used.

The mode of operation of a conventional, known modulator will be explained with reference to FIG.

At the input £ 2 is the carrier frequency which, depending on the polarity of the control characters fed to the control input E 1, should either appear at the output ^ or not. Let us first assume that the potential at the control input terminal al is positive compared to that at the terminal bl . In this case, the two modulator rectifiers oil and £> 2 are permeable, and the carrier frequency at input E 2 is transmitted to output A.

However, if the input terminal b 1 positive with respect to the input terminal al, the modulator rectifier Dl and D 2 are locked. The carrier frequency at input El can therefore not be transmitted and does not appear at output A.

This simple modulator circuit shown in Fig. 1 does not meet all the requirements that be put to a high quality modulator circuit by modern telegraphy transmission technology. These requirements are essentially the following:

1. If there are no control characters in the control area lock the modulator securely.

2. The control output should be based on the carrier frequency are not influenced.

3. The carrier frequency generator should be evenly loaded with separating and character current output.

DC controlled AC modulatars

Applicant:
Siemens & Halske Aktiengesellschaft,

Berlin and Munich,
Munich 2, Wittelsbacherplatz 2

Dr. phil. Wolfgang Seefeldner

and Dipl.-Phys. Hans Neuss, Munich,

have been named as inventors

4. The modulator should manage with the lowest possible power of the control characters.

The modulator circuit shown in FIG. 1 does not satisfy any of these four requirements Measures met.

Another known modulator circuit is shown in FIG. In contrast to the modulator circuit according to FIG. 1, a resistor (R2) and four rectifiers (Z> 4, D 5, D6, D7) have been added. The mode of action is as follows:

It is initially assumed again that the input terminal al is positive with respect to the input terminal bl . A voltage drop occurs across the resistor R1. The carrier frequency voltage fed to the input terminal E2 reaches the resistor R 2 via the rectifiers D 4 and D 7 , at which a small voltage drop in the opposite direction is generated with respect to R 1. The resulting sum voltage makes the two modulator rectifiers D 1 and D2 permeable, and the carrier frequency voltage present at input E2 reaches output ^. If the input terminal b 1 is positive compared to the input terminal al, the voltages at the resistors Rl and R2 have the same direction, and the modulator rectifiers Di and j9: 2 are blocked, even if the control characters are missing, i.e. no input voltage at the terminals al and bl occurs. In this case, the resistor R2 is supplied with energy from the generator present at the input E2 via the rectifiers Z) '4 to D 7.

The modulator circuit shown in FIG. 2 thus fulfills two of the four conditions set out above. It has a blocking effect if control characters are missing,

009 608/229

the carrier frequency generator is evenly loaded with separating and symbol current output, if the resistance R2 and the load resistance at the output terminals are the same size with a transmission ratio of 1 of the transformers. In addition, the modulator rectifiers Dl and Z> 2 are safely blocked in the idle state. Their disadvantage, however, is the greater power required by the control characters to overcome the voltage drop across R2.

Other modulator circuits are known, but not all of them either four requirements met.

In the DC-controlled AC modulator circuit according to the invention with two alternately Voltage-carrying first pairs of terminals as outputs for amplitude modulation or frequency modulation (for AC telegraph systems) or as inputs for various carrier frequencies Double-tone modulation and a second pair of terminals as the input of a carrier frequency for amplitude modulation or frequency modulation or as the output of two alternating carrier frequencies with double-tone modulation, these requirements are met by the fact that in the control circuit individual modulator branches controllable resistors, preferably the same or different transistors Conductivity type, preferably in emitter connection in series and / or in parallel connection can be used, depending on the polarity of the DC symbols fed to the control input are alternately open or locked and so alternately a connection between one of the first Establish pairs of terminals and the second pair of terminals.

In an advantageous embodiment, two transistors of the same conductivity type are located in the middle branches of the individual modulation branches, whose emitter-base lines are in opposite directions in series in the direct current circuit, being parallel to the Emitter-base paths of these transistors each have a non-directional or directional resistor connected. The directional resistor is connected in opposite directions in parallel to the emitter-base path. In a further advantageous embodiment there are two identical transistors in the middle branches of the individual modulation branches Conductivity type whose emitter-base paths are parallel in opposite directions in the direct current circuit. Advantageous there are two transistors of the same conductivity type in emitter circuit in each of the modulator branches, whose emitter-collector lines are connected in series in opposite directions and their emitter-base lines are parallel in opposite directions in the direct current circuit, with a current-determining line in each base lead Resistance is turned on.

In another advantageous embodiment, the modulator branches also have each two transistors of the same conductivity type in emitter circuit, their emitter-collector paths but are connected in parallel in opposite directions and their Bases are each connected to the control input via a current-determining resistor.

If, with the arrangements according to the invention, single tone signals are to be generated at only one of the first terminal pairs with an even load on the carrier frequency generator, it is advantageous to terminate the other first terminal pair with a resistance corresponding to the load resistance of the first terminal pair. In this case, the output transformer, which is assigned to the other first pair of terminals and terminated with a resistor, can be replaced by transformed resistors corresponding to the load resistance of the first pair of terminals.
If double-tone telegraphic characters are to be generated with the arrangements according to the invention, generators of different frequencies are advantageously connected to the previous outputs. The double-tone telegraphic characters are then removed differently

ίο previous carrier frequency input. Should also be in this If an even load on the frequency generators is to be ensured, a advantageous embodiment in the pauses for each frequency generator an additional modulator branch effective with a resistance corresponding to the load resistance.

Details of the invention are explained with reference to the drawings.

Fig. 3 shows an advantageous embodiment

according to the invention. At the entrance Bl fiscal marks be such. B. double-current direct current signals are supplied. Let us first assume that the input terminal a1 is positive with respect to the input terminal & 1. A current then flows from the terminal al via the resistors R 3 and Ri and the emitter-base path of the transistor Γ 2 to the terminal bl . By means of the resistor R 3, a specific input resistance and thus control direct current can be set essentially via the low-resistance emitter-base path of the transistor T2 compared to the resistor R 5. For reasons of symmetry, the resistance can also be divided between the two input lines. Resistor 3 also decouples the controlling direct current source from the pulsating direct current in the modulator branches. The voltage drop across the resistor R 4 causes a voltage across the base-emitter junction of the transistor T 1, with the result that it is blocked.

The transistor T2, on the other hand, becomes conductive. The carrier frequency generated by the generator G 1 present at the input E2 , which is coupled in via the transformer UTl , causes a current to flow through the diode Z> 9 during one half-cycle of the carrier frequency voltage, while the other half-cycle causes a current to flow through the diode D 11, so that both half-waves flow through the emitter-collector path of the transistor T2 in the same direction. The carrier frequency voltage arrives at the output A 2 via the transformer UT 3.

It is now assumed that the input terminal b 1 is positive with respect to the input terminal a1. In this case, a current flows from the terminal bl via the resistor R5, the emitter-base path of the transistor Tl and the resistor R 3 to the terminal al . Due to the voltage drop across the resistor R S, the transistor T 2 is now blocked, while the transistor Tl becomes conductive. The carrier frequency voltage now reaches the output A 1 via the open transistor T1 and the diodes D 8 or D 10 and the transformer UT 2.

The carrier frequency voltage is thus switched through either to the output A1 or the output A2 .

When using the shown modulator circuit for single tone telegraphy, with the separating and Character stream status or character and trenh current status on the line due to its presence or the absence of a frequency

only a single-phase AC symbol is required. The lower half of the modulator circuit according to FIG. 3 can therefore advantageously be terminated with a resistor R 8 which, if it corresponds to the load resistance connected to the terminals A 1, loads the generator Gl evenly even during the pauses between the keys. The transmitter UT 3 may be omitted, if one replaces the overlapped at the secondary side of this transformer load resistor R 8 by two equivalent transformed resistors R 6 and R 7 in place of the primary side of the transformer UT 3 of FIG. 4. In the modulator circuit according to FIG. 4, the two control resistors R 4 and R 5 for the transistors Γ1 and Γ2 are also replaced by the diodes D12 and D13 . The use of diodes instead of resistors has the advantage that interference voltage peaks at the control input £ 1 are limited to the forward voltage of the diodes. In addition, these diodes have the advantage that the control power is lower than in the arrangement with resistors according to FIG. 3. Otherwise, the mode of operation of the circuit arrangement according to FIG. 4 corresponds to that of the circuit arrangement according to FIG. 3.

Fig. 5 shows a further embodiment according to the invention. In contrast to the exemplary embodiment according to FIGS. 3 and 4, the base-emitter paths of the two input transistors T1 and T 2 are parallel in opposite directions. In addition, the transformer UTl is equipped with two separate push-pull windings. The control signals of alternating polarity at the input El each open one transistor, while the other transistor is blocked with the voltage drop across the base-emitter path of the conductive transistor. By dividing the secondary winding of the transformer UT 1 take over the emitter-base junctions of the transistors, the functions of the diodes · D 12 and D13 of Fig. 4. The transfer of the applied to the input E2 carrier frequency alternately to the Ausganged 1 and A2 is accomplished in the same way as in the embodiments according to FIGS. 3 and 4. Also with the modulator circuit according to FIG. 5, if only a single-current alternating current symbol is required, a load resistor at output A 2 or instead of the primary side of the transformer to be omitted UT 3 two equivalent transformed resistors are provided in order to ensure an even load on the generator Gl .

The modulator circuits shown in FIGS. 3 to 5 can advantageously also be used for double-tone telegraphy. In this case, as shown in FIG. 6, a carrier frequency generator G 2 is connected to the previous output A 1 and a carrier frequency generator G 3 is connected to the previous output ^ 2, which supply the two frequencies to be transmitted alternately. The transistors T1 and T 2 are controlled as previously described. Then the transistors Tl and T2 alternately, the frequencies supplied by the generators G 2 and G 3 appear at the previous carrier input B2 depending on the control.

When in Fig. 6 circuit arrangement shown is a uniform loading of the two generation ^δ 5 generators G 2 and G 3 are not given.

In Fig. 7 a 'modulator circuit is shown, in which the two generators G 2 and G3 evenly are burdened. The mode of operation of this modulator circuit is as follows:

The control characters are in turn fed to the input El. If the input terminal α-1 is positive with respect to the input terminal bl , a current flows from the input terminal al via the resistor R 3 and the emitter-base paths of the transistors T3 and T2 to the input terminal & 1. As a result, the transistors T 3 and T 2 are controlled to be conductive, while the transistors Π and Γ 4 are blocked by the voltage drop on the transparent emitter-base paths of the transistors T3 and T2. The frequency supplied by the generator G 3 is thus via the transformer UT 3, the permeable transistor Γ2 and the diodes D9 and Z> 11 and the transformer UT1 to the output E2. transfer. A current flow via the load resistor R 9 and the diodes D 12 or D14: is enabled via the permeable transistor Γ 3, so that the generator G 2 is also loaded.

Let us now consider the case that the input terminal b 1 is positive with respect to the input terminal a1. In this case, a current flow is formed, starting from the terminal b 1, over the emitter-base paths of the transistors φ4 and Tl , whereby these are opened. At the same time, the transistors T 2 and T 3 are blocked due to the voltage drop across the emitter-base paths of the transistors T4 and Tl. In this case, the frequency of the generator G 2 appears at the output £ 2, while the generator G 3 works on the load resistor R 10.

As in the previous examples, the size of the load resistances i? 9 and RIO is chosen so that the generators G 2 and G 3 with separating and character current output! are evenly loaded.

In the modulator circuits of FIGS. 3 to 7, in which the transistors are located in the central branches, the pulsating direct currents of both half-waves of the carrier frequencies flow through them in the same direction. In the modulator circuits shown in FIGS. 8 and 9, the transistors of a modulator branch are each traversed by the pulsating direct currents of only one half-wave of the carrier frequency. The transistors of a modulator branch replace the diodes for the pulsating direct current flow derived from the carrier frequency. For reasons of symmetry and a simple modulation, it is advantageous to connect at least one electrode of the transistors to one another directly or via current-determining resistors. In FIG. 8, for example, the emitters of the transistors Tl and Tl or T3 and Γ 4 are connected directly and the respective bases are connected to one another via current-determined resistors. The emitters of the transistors Tl and T2 and the common base terminal of the transistors 7 * 3 and 4 are connected Γ al via the resistor R3 to the terminal. The terminal b 1 leads to the corresponding other connections of the transistors T3 and Γ4.

If the terminal a1 (Fig. 8) is positive compared to the terminal b 1, then the resistor i? 3, the emitter-base paths of the transistors Tl and T 2 and a current flow through the resistors R 11 and i? 12 to the terminal b 1. As a result, the transistors Tl and T * 2 are conductive, so that pulsating direct currents can develop over their emitter-collector paths, whereby the half-waves of the carrier frequency, which are supplied via the transformer UTl from the carrier frequency generator G1 connected to the input E 2, alternately across the

sistors Tl or TZ and the associated primary windings of the transformer UTl flow. The carrier frequency can be taken from output A1.

Due to the voltage occurring at the emitter-base paths of the transistors T1 and TZ and the resistors R 11 and RlZ , the transistors T3 and T 4 are blocked, so that the carrier frequency of the generator Gl does not appear at the output A2.

On the other hand, if terminal b 1 is positive with respect to terminal a1, transistors T 3 and Γ4 are conductive and transistors Tl and T 2 are blocked. The carrier frequency can now be taken from output ^ 2, while it does not appear at output A 1.

It is of course possible, within the mesh of a modulator branch, to switch the transistors to any location outside the central branch, as shown in FIG. 9, for example. If the input terminal el is positive with respect to the terminal bl , a current flows through the resistors R 3, i? 4 and R 5. The voltage drop occurring across the resistor R 5 causes two partial currents via the emitter-base paths of the transistors T 3 and Γ 4 and the current-determining resistors R 13 and 14. As a result, the transistors T3 and T 4 become conductive, so that half-wave currents of the carrier frequency Gl supplied via the transformer UT-1 can flow over their emitter-collector paths. The carrier frequency can be taken from output A2. The voltage drop across the resistor R 4 blocks the transistors T1 and T2 and thus the upper modulator branch.

If the terminal b 1 is positive compared to the terminal a1 , the transistors T1 and T2 are controlled to be permeable and the transistors T 3 and T 4 are blocked in an analogous manner. In this case, the carrier frequency can be taken from output A1.

In Fig. 10, a further embodiment is shown according to the invention, in which the dated pulsating direct current of the carrier frequency through flowing diodes according to FIGS. 1 to 7 through transistors are replaced. The emitter-collector paths of the transistors of a Mcdulatorzweig are the same Conductivity type connected in parallel in opposite directions. For easy control are the bases of these transistors connected to each other via current-determining resistors.

Is the input terminal al positive with respect to terminal & 1, a current flows through the resistors i? 3, i? 4 and R 5. The 5 voltage occurring at the resistor R allows two partial streams over the Se ^u kundärwicklungen of the transformer UTL, the primary winding of Transformer UTS, via the emitter-base paths of the transistors T 3 and Γ 4 and via the associated current-determining resistors R 13 and R 14 to terminal & 1. The transistors T 3 and T 4 become conductive, so that pulsating direct currents can develop over their emitter-collector path. The half-waves of the carrier frequency of the generator G supplied via the transformer UT1 can thus flow alternately, depending on the polarity, via the transistors T 3 and T 4 and the primary windings of the transformer UTZ. The carrier frequency can be taken from output A 2. The voltage appearing at the resistor R 4 blocks the transistors T1 and T2 so that the carrier frequency does not occur at the output A1.

If the terminal 1 and positive with respect to the terminal al, the transistors T3 and TA are disabled and the transistors Tl and TZ conductive. The carrier frequency can now be taken from output A 1, while it does not appear at output A 2.

Of course, it is also possible here to switch on the transistors at any point within the mesh of a modulator branch. An advantageous embodiment of this is shown in FIG. 11. The necessary division of the secondary windings of the transformer UT1 for the individual modulator branches results in the advantage that, as shown in FIG

ίο Fig. 6 the on the emitter-base lines and the associated current-determining resistors, the voltage drop of the transistor pair of a modulator branch can be used to block the pair of transistors of the other pair of modulators. the The mode of operation of the circuit according to FIG. 11 is analogous to that according to FIG. 10.

As already described for FIG. 6, the circuits according to FIGS. 8 to 11 can also be used for double-tone telegraphy if two generators of different frequencies are connected to the previous outputs A1 and A2. The double-tone telegraph characters then appear at the previous EZ entrance. When using the shown modulator circuits for single tone telegraphy, as in

As described in Fig. 3, the generators are evenly loaded here in the pauses if the output A 2 is terminated with resistors which correspond to the consumer resistance terminating the output A 1. As already described for FIG. 4, suitably dimensioned, transformed resistors can be switched on for this instead of the primary windings of the transformer UT 3.

The circuits of FIGS. 8 to 11 can also be used for double-tone telegraphy, wherein they also, as indicated for FIG. 7, by further modulator branches with load resistors can be added so that the generators are evenly loaded during the pauses.

In the exemplary embodiments described, pnp transistors were used in each case. Of course it is possible, without departing from the scope of the invention, these transistors entirely or to be partially replaced by npn transistors. The resulting changes with regard to the switching on of these transistors in the circuits described are known and therefore need not to be explained in more detail. The transistors can also be in base or collector circuit operate.

Claims (9)

Patent claims: 1. DC controlled AC modulator circuit with two alternating voltage-carrying first pairs of terminals as outputs with amplitude modulation or frequency modulation or as inputs for different carrier frequencies with double-tone modulation and a second pair of terminals as the input of a carrier frequency in the case of amplitude modulation or frequency modulation, more or less than the output of two alternating occurring carrier frequencies with double-tone modulation, characterized in that Controllable resistors, preferably transistors, in the control circuit of the individual modulator branches of the same or complementary conductivity type, preferably in an emitter circuit in Series and / or parallel connection can be used, depending on the polarity of the control input (El) are alternately opened or blocked and thus alternately establish a connection between one of the first pairs of terminals (A 1, A 2) and the second pair of terminals (E 2) . 2. Circuit arrangement according to claim 1, characterized in that two transistors of the same conductivity type are located in the central branches of the individual modulation branches (T1 and T2 in FIGS. 2 and 3), the emitter-base paths of which are in opposite directions in series in the direct current control circuit and parallel to them Emitter-base lines a non-directional (i? 4, R5) or directional resistor (D12, D 13) is connected in parallel in opposite directions. 3. Circuit arrangement according to claim 1, characterized in that two transistors of the same conductivity type (T1, T2 in Fig. 5) are in the middle branches of these modulation branches, the emitter-base paths of which are parallel in opposite directions in the direct current control circuit. 4. Circuit arrangement according to claim 1, characterized in that two transistors of the same conductivity type in emitter circuit (Γ1 to T 4 in Fig. 8) are in the modulation branches, the emitter-collector paths are connected in opposite directions in series and their emitter-base Lines in the DC control circuit are parallel in the same direction, with a current-determining resistor (RU to i? 14) being switched on in each base lead. 5. A circuit arrangement according to claim 1, characterized in that two transistors of the same conductivity type are located in emitter circuit in each of the modulator branches (T1 to Γ 4 in Fig. 10), the emitter-collector paths of which are connected in parallel in opposite directions and their bases each via a current-determining one Resistance (RIl to R14t) are connected together with the control input. 6. Circuit arrangement according to claim 1 to 5 for generating single tone characters at only one output (A 1) with uniform loading of the carrier frequency generator, characterized in that the other output (A2) with a resistance (R ) corresponding to the working resistance of one output (Al) 8 in Fig. 3) is completed. 7. Circuit arrangement according to claim 6, characterized in that the primary windings of the transformer (UT3 ) assigned to the other output (A 2) are offset by the load resistance of the one output corresponding resistors (R6, R7 in FIG. 4). 8. Circuit arrangement according to claim 1 to 5 for generating double-tone telegraph characters, characterized in that generators of different frequencies (G 2, GZ in Fig. 6) are connected to the previous outputs (A1, A2) and the double-tone characters are removed from the previous carrier frequency input (£ 2) takes place. 9. Circuit arrangement according to claim 8 for uniform loading of the two frequency generators, characterized in that an additional modulator branch with a resistor (R9, RIO in Fig. 7) corresponding to the load resistance is effective in the pauses for each generator. For this purpose 2 sheets of drawings © I 009 608/229 9.