DE1053568B - Circuit arrangement for converting almost rectangular pulses into trapezoidal or triangular pulses - Google Patents

Description

GERMAN

The invention relates to a circuit arrangement for converting almost square-wave pulses into trapezoidal or triangular pulses of symmetrical shape and high slope.

In impulse communication technology there is often the task of generating bell-shaped pulses, as they use a small bandwidth for long-distance transmission. This pulse shape becomes usually derived from square-wave pulses that are fed to a bell filter. The effort at filters is less when the square-wave pulses are initially in the first approximation of bell pulses Turn trapezoidal pulses formed. These should have the highest possible edge steepness and a symmetrical one Have shape.

A special case of the trapezoidal pulses are the triangular pulses, which are derived in a similar way will. With this pulse shape too, symmetry and a high edge steepness are often sought. ..

Furthermore, trapezoidal pulses can also be used to broaden given square-wave pulses, when the base of the trapezoidal pulses obtained is wider than that of the given square-wave pulses. For this the amplitudes of the trapezoidal pulses are limited and only those parts that are close to the time base supplied for further use.

Known devices for achieving pulse shapes with a high edge steepness contain a tube, whose grid is biased so that a quiescent current flows. A square pulse is applied to the grid of this tube negative polarity, whereby the tube is blocked. This gives one infinite large resistance, so that a capacitor arranged in parallel is charged via a series resistor will. The time constant of the capacitor is large compared to the pulse duration. The charge of the capacitor therefore only takes place in a relatively linear sub-area of the expons > tial charging curve of the capacitor. When the trailing edge of the input pulse hits the tube grid reached, the tube becomes conductive again and the capacitor discharges quickly. the The rectangular input voltage was thus converted into a sawtooth voltage effective at the capacitor with an almost linearly rising void flank and vertical falling trailing edge converted.

Devices of this type have the disadvantage that they require electron tubes with a plurality of control electrodes. In addition, they can only be used to achieve triangular pulses with different slopes of the leading and trailing ranks , whereby the slope of the vertically running trailing edge cannot be changed.

These disadvantages will apply to the generation of trapezoidal circuitry for conversion

almost rectangular pulses
in trapezoidal or triangular shaped pulses

Applicant:

Telefunken G. mb H.,
Berlin NW 87, Sickingenstr. 71

Helmut Oberbeck, Ulm / Danube,
has been named as the inventor

ader triangular pulses avoided by according to the invention the square-wave pulses are fed to a directional guide that blocks the pulses, wherein the directional conductor a capacitor is connected in grater and this series arrangement is preferably one small resistor is connected in parallel, and that the capacitor a second, from one Directional conductor and a capacitor is connected in parallel in such a way that electrodes of the same name of the two directional conductors are connected are, and that at this connection point a voltage is supplied and a voltage opposite polarity and smaller absolute value with the counter electrode of the directional conductor of the second series arrangement is connected, these voltages having higher values than the voltage amplitudes of the supplied impulses.

In Fig. 1 an embodiment of the circuit arrangement according to the invention for positive input pulses is shown. The circuit arrangement can, however, also be used for negative input pulses if the two diodes marked 3 and 4 have reversed polarity and the signs of the two bias potentials + Fj and -V _{2 are also} interchanged. The given square-wave pulses are fed to the circuit arrangement shown via input terminals 1 and 2. The corresponding trapezoidal pulses are picked up at the output terminals 10 and 11. As long as no pulse reaches the input of the switching arrangement, the voltage source with the potential - ³ TV _{1 flows} through the large resistor 8, the diode 3 and the small one Resistor 7 a current. Likewise flows through the large resistor 9, the diodes 4 and 3 and the resistor 7

809 787/383

Current that is supported by the negative potential - V ₂ (of the other voltage source. However, this is only possible if either the absolute value of the potential + V _{1 is} greater than the absolute value of the potential - V ₂ or if the potentials are the same (V ₁ = ¹ V ₂ ) the resistances are smaller than the resistor 9-. Under these conditions the current flowing through the diode 3 in the positive direction is greater than the current flowing through the diode 3 in the negative direction Diode 3 remain blocked, which would result in the charging of the capacitors 5 and 6. Under the given conditions, however, such charging cannot occur, since the resistor 7 may only be small and consequently there is no significant charging potential at the points 12 and 13 of the circuit can form.

If the positive square pulse 14 shown in Fig. 2a reaches the input terminals 1 and 2 of the circuit, the flow of current through diode 3 is immediately stopped from the beginning of the arrival of the leading edge of the pulse, since the cathode of this diode is on ( assumes a positive potential corresponding to the pulse amplitude, while at the first moment the anode is still approximately at zero potential. The consequence of this is that the two capacitors 5 and 6 are charged, and both endeavor to maintain the positive potential + V _{1 of} that voltage source, which is connected to the circuit via the smaller resistor 8. The negative bias voltage source - V ₂ has only a subordinate influence on the charging of the two capacitors 5 and 6, since this has a much higher series resistor 9. In Fig. 2b the voltage rise over time at the capacitor 5 is shown by the line 15. The Sp arrangement of the capacitor 6 connected to the capacitor 5 through the diode 4, as shown in Fig. 2c. However, the capacitors are not charged up to the full bias potential + V ₁ , rather the voltage rise stops as soon as the voltage has assumed the potential + U _{1 of} the given right pulse 14. From this moment on, the same potential prevails on the cathode and anode side of the diode 3, so that the diode 3 is opened again from this moment on and a further increase in potential of the points marked 12 and 13 is prevented. The potential of the two capacitors therefore remains unchanged until the arrival of the trailing edge of the pulse 14: which is expressed in Fig. 2t> and 2c by the horizontal part of the curve. Since, as can be seen, only the lowermost part of the charging curve 15 is used when the two capacitors 5 and 6 are charged, the leading edge of the pulses accordingly also runs almost linearly. The higher the charging potential V ₁ and the larger the resistance 8, the better the linearity.

When the trailing edge of the pulse 14 arrives, the potential of the diode 3 on the cathode side suddenly drops to zero potential, which causes a momentary discharge of the capacitor 5 through the diode 3 and the resistor? has the consequence. This is shown in Fig. 2b by the steep trailing edge 17 of the pulse. A corresponding discharge of the capacitor 6 cannot occur because its upper occupancy is at positive potential due to the previous charging process and the diode 4 is polarized in such a way that it prevents a discharge in the same way. Therefore, the discharge of the capacitor 6 goes through the resistor 9 and 'the Vorspanrjungsquelle to the negative potential -V ₂ vonstatten which .is uphold the capacitor 6 to the negative potential - V ₂ to reload. In Fig. 2 c, in which the time profile of the voltage on the capacitor 6 is shown, the discharge curve of the capacitor 6 is shown

ίο represented by line 18. Also from this curve wind, similar to curve 15 during the charging process (Fig. 2 b), only the lower one is approximately linear running part exploited, so that the trailing edge of the trapezoidal pulses assumes a linear course.

iS If the zero potential is now reached during the discharge, the diode 4 is suddenly opened again, as a result of which the initial state that prevailed before the impulse 14 was received is restored. So again a quiescent current flows from the bias voltage source with the potential - V ₂ via the resistor 9, the diodes 4 and 3 and the small resistor 7. The current path via the resistor 8, the diode 3 and the resistor 7 is the same for the other Bias source with the potential + V ₁ opened again.

Instead of the two high resistances 8 and 9, in conjunction with a voltage source of high potential each, other linearization means can also be used. For example, instead of the two resistors 8 and 9, pentodes can also be used in a manner known per se, whereby a linear voltage curve can also be achieved when the capacitors 5 and 6 are charged and discharged.

As can be seen from the explanations, the inclination of the pulse edges of the trapezoidal pulse can through Dimensioning of the charging and discharging time constants can be changed within any limits. Should the derived Impulse, as shown for example in Fig. 2c, must have a symmetrical shape turn to the fact that the time constant for the charging of the capacitor 5 is the discharge time constant of the capacitor 6 is the same. Since, however, as described above, the resistor 9 is chosen to be significantly higher must turn than the resistor 8, it is therefore necessary that 'the capacitor 6 is correspondingly smaller than the capacitor 5. For example, the resistor 9 is ten times greater than the resistor 8, the capacitor 6 must ten times

So be chosen smaller than the resistor 5, so that approximately the product C ₃ · R ₈ = C ₆ - R ₉ .

As already mentioned in the introduction, the Circuit arrangement can also be used to derive triangular pulses. As can be seen from Fig. 3, the time constant for charging the capacitor must be used for this purpose 5 turn selected so that the charging process at the earliest when the trailing edge of the Pulse 14 has ended. In this case, the discharge process of the capacitor begins at that moment 6 initiated, where the charging process of the capacitor 5 is ended, so that the capacitor 6 resulting impulse does not receive a horizontally running dome.

The i? C element of the discharge can of course be chosen as desired. If this, as shown in Fig. 3, equal to the 2? C member of the charge, so get we get an isosceles triangular momentum, the base of which is twice as large as the base of the given Square pulse 14. If the time constant of the

Claims (5)

If the charge is selected to be smaller than that of the charge, then the circuit arrangement according to the invention can be used to produce saw teeth with more or less steep trailing edges. P A T E N T A N S i> R C CHE: 1. Schaltunigsanordnung for converting almost rectangular pulses into trapezoidal or triangular pulses of symmetrical shape and high edge steepness, characterized in that the rectangular pulses are fed to a directional conductor (3) which blocks the pulses, the directional conductor (3) having a capacitor (5 ) is connected in series and a preferably small resistor (7) is connected in parallel to this series arrangement, and a second series arrangement consisting of a directional conductor (4) and a capacitor (6) is connected in parallel to the capacitor (5), that electrodes of the same name of the two directional conductors are connected, and that at this connection point a voltage (F ₁ ) is supplied and a voltage (F ₂ ) of opposite polarity and with a smaller absolute value is connected to the counter electrode of the directional conductor (4) of the second row arrangement, with these voltages have higher values than the voltage amplitudes of the supplied pulses ulse. 2. Arrangement according to claim 1, characterized in that the voltages (F ₁ , F ₂ ) are supplied with opposite polarity via resistors (8,9). 3. Arrangement according to claims 1 and 2, characterized in that instead of the resistors (8, 9) via which the voltages (F ₁ , F ₂ ) of opposite polarity are supplied, pentodes are arranged. 4. Arrangement according to claims 1 to 3, characterized in that the charge of the capacitor (5) the first series arrangement takes place with the same time constant as the discharge of the capacitor (6) of the second series arrangement. 5. Arrangement according to claims 1 to 4, daao characterized in that the time constants · for the charge and discharge of the capacitors (5, 6) are variable. Considered publications:
Book "Waveforms", Mc Graw Hill Book Comp., 1949, p. 9, Fig. 1.1 (c), p. 40., Fig. 3.1;
U.S. Patent No. 2,597,322. 1 sheet of drawings