US2899552A - X e electric pulse generating apparatus - Google Patents

Description

Allg- 11' 1959 v G. P. FRENCH 2,899,552

ELECTRIC PULSE GENERATING APPARATUS Filed Jan. 3, 1955 FIT-ro nNcY 2,899,552 ELECTRIC PULSE GENERATING APPARATUS Gordon Percival French, South Croydon, England, assignor to The General Electric Company Limited, London, England Application January 3, 1955, Serial No. 479,607- Claims priority, application Great Britain January 1,1954

`5 Claims. (Cl. Z50- 27) The present invention relates to electric pulse generating apparatus and in particular is concerned with apparatus for generating a pair of substantially identical pulses in response to an applied trigger pulse, corresponding points on the pair of pulses being separated by a predetermined time interval and the pulses of the pair each having a predetermined duration less than the said interval.

According to the present invention electric pulse generating apparatus for generating a pair of substantially identical pulses in response to an applied trigger pulse having sharp leading and trailing edges, corresponding points on the pair of pulses being separated by a time interval equal to that separating the leading and trailing edges of the trigger pulses of the pair each having a predetermined duration less than the said interval, comprises a pair of resonant circuits each having a natural period equal to twice the predetermined duration of the individual pulses of the pair, means for passing a current pulse through the resonant circuits in response to the trigger pulse, the current pulse having the same duration as the trigger pulse, asymmetrically conducting devices associated with each of the resonant circuits and arranged so that a damped oscillation, consisting substantially of a single half cycle, is excited in each resonant circuit in turn, one in response to the leading edge of the current pulse and one in response to the trailing edge, and an output circuit coupled to both the resonant circuits so that the damped oscillations excited in the two resonant circuits by a trigger pulse produce in the output circuit two pulses respectively which are of the same polarity.

Said means for passing a current impulse through the resonant circuits may comprise a thermionic valve of the kind having an anode, a cathode and at least one intermediate control electrode, one resonant circuit being included in the anode load circuit of the valve and the other resonant circuit being included in the cathode load circuit of the valve, and a path for applying the trigger impulse to the control electrode of the valve.

Preferably the inductances of the two resonant circuits are mounted on a common core, on which is mounted a third coil lying between the inductances on the core, output terminals being connected across the third coil.

Apparatus in accordance with the present invention may be combined with, or form part of, means for deriving the said trigger pulse having sharp leading and trailing edges separated by a predetermined time interval from an input pulse of some other duration and/ or form. In addition apparatus in accordance with the present invention may be combined with, or form part of, means for generating a regularly recurrent train of trigger pulses having sharp leading and trailing edges separated by a predetermined constant time interval, whereby the apparatus generates regularly recurrent pairs of pulses at a recurrence frequency determined by that of the trigger pulse train generating means.

Said means for deriving a trigger pulse, having sharp ice leading and trailing edges separated by a predetermined time interval, from an input pulse ofv some other duration and/or form, may comprise a mono-stable trigger circuit arranged to generate a trigger pulse in response to an input pulse. Where, as aforesaid, the apparatus includes a thermionic valve, the mono-stable trigger circuit may include a pair of thermionic valves, one of which is the said thermionic valve, and is arranged so that a trigger pulse of the required form appears in operation at the control electrode of that valve on the application of an input pulse tothe trigger circuit.

Electric pulse generating apparatus in accordance with the present invention will now be described by way of example with reference to the two iigures of the accontpanying drawing in which Figure l shows the electric circuit of apparatus which is arranged periodically to generate a pair of pulses, each of the same pre-determined duration and having a predetermined time interval between them, in response to an applied trigger pulse having a duration equal to the interval between the pair of pulses to be generated, and

Figure 2 shows the electric circuit of an arrangement which is obtained from Figure l but which includes means to derive the trigger pulses from a train of input pulses.

Referring now to Figure l, the apparatus comprises a triode thermionic valve 1, having a conventional control grid circuit coupling the control grid 2 to a pair of input terminals 3 across which are applied recurrent rectangular trigger pulses. Each of these trigger pulses have a duration equal to the interval required between a pair of pulses to be generated. The trigger pulses may be of either polarity but preferably if the pulses are negativegoing the valve 1 is conducting in the absence of such a pulse and is cut off by the pulses while if the pulses are positive-going the valve is biassed so that the reverse conditions apply.

A parallel resonant circuit 4 is connected between the cathode 5 of the valve 1 and earth, the natural period of the circuit 4 being equal to twice the duration o-f the individual pulses of the pairs to be generated. A germanium crystal rectier 6 is connected in parallel with this resonant circuit 4, its polaritybeing arranged so that the cathode 5 of the valve 1 may not become positive with respect to earth.

The anode circuit of the valve 1 comprises a resistor 7 connected in series with a further parallel resonant circuit 8 between a positive high tension voltage supply line 9 and the anode 10 of the valve 1. This anode resonantcircuit 8 is tuned to the same frequency as the cathode resonant circuit 4, and has a germanium crystal rectiiier 11 connected in parallel with it, the polarity of the rectifier 11 being arranged so that the end of the anode resonant circuit 8 that is connected to the anode 10 may not become positive with respect to the end thereof that is connected to the resistor 7. The inductances 12 and 13 of the anode and cathode resonant circuits 4 and 8 are wound on a common core 14, for example a core of ferrite material. An output winding 15 is also provided on the core 14. The inductances 12 and 13 are, Ain fact, in resonance with their own self-capacities which in the drawing are shown as capacitors 16 and 1'7.

The circuit described above operates as follows. Assuming that a negative rectangular trigger pulse is applied to the control grid 2 of the valve 1, the decrease in current through the valve 1 causes a damped oscillation to be generated in the cathode resonant circuit 4 in response to the leading edge of the pulse, the oscillation consisting only of a single half cycle, since the second half cycle is damped out by the rectier 6 which becomes conductling when the cathode 5 of the valve 1 tends to go positive with respect to earth. Since the natural period of the cathode resonant circuit 4 is equal to twice the duration of the pulses of the required pairs of pulses, this oscillation effectively forms, at the cathode 5 of the valve 1, a single negative-goingpulse of the required duration andl occurring at atime` coinciding with the leading edge. of the applied trigger pulse. l Since the first half cycle of'any oscillation `which might be generated in the anode resonant circuit 8 in response to the leading edge of the trigger pulse would result in the r'ectifier 11 conducting, this oscillation is damped out completely. Due to the mutualv coupling betweenfthe inductance and the output winding 15,.-the damped oscillation in the resonant circuit 4 produces a pulse at the output terminal 18, the polarity of this pulse being determined by the manner in which the winding 15 is connected.

On the occurrence of the trailing edge of the applied trigger pulse, an oscillation consisting of a single halt cycle is generated in the anode resonant circuit 8 in similar manner, whilst no oscillation is generated in `the cathode resonant circuit 4 owing to the damping effect of the rectifier 6. The oscillation excited in the anode resonant circuit 8 will provide a negative impulse at the end of the anode resonant circuit 8 that is connected to the anode 10 of duration equal to that of the pulses of the required pairs, and coinciding in tirne with the trailing edge of that trigger pulse. Again a pulse is produced at the terminal 18 and the inductances 12 and 13 and the winding 15 are connected in such a sense that this pulse is in the same direction as the previously mentioned pulse produced at this terminal. Thus a pair of like pulses are produced at the terminal 18 upon the application of a trigger pulse to the control grid 2 of the valve 1, the two pulses of the pair having a separation equal `to the duration of the trigger pulses and both having a duration equal to half the natural period of the resonant circuits 4- and 8. It will be appreciated that by suitable choice of the duration of the applied trigger pulses and the natural period of the resonant circuits 4 and 8, it is possible to provide pairs of pulses of any required separation and duration.

It will be seen that the trigger impulse may be either positive or negative, since the anode resonant circuit 8 produces an impulse in response to a positive-going voltage change at the control grid 2 of the valve 1, and the cathode resonant circuit 4 produces an impulse in response to a negative-going voltage change at the control grid 2, and it does not much matter in which order these pulses are produced.

The output winding is preferably located on the core 14 between the inductances 12 and 13 so as to reduce the direct mutual coupling between the inductances 12 The output winding 15 is not, however, essential and if this winding is omitted the output lterminal 18 may be connected directly to the anode 10 of the valve 1. With this arrangement it is clear that the pulse produced by the resonant circuit 8 will appear at the terminal 18 while the pulse produced by the resonant circuit 4 also appears at that terminal due to the mutual coupling between the inductances 12 and 13.

lf a source of trigger pulses of the correct duration is not available, the apparatus described above with reference to Figure l may be combined with, or form part of, means for generating trigger pulses of the required shape and duration from pulses of some other shape and/or duration. An arrangement in which the apparatus forms part of such means is shown in Figure 2 of the accompanying drawing and, for ease of reference, corresponding items in the 4two figures carry the same reference numerals.

Referring now to Figure 2, the valve 1 is connected to form part of a mono-stable trigger circuit. In this arrangement, the control grid circuit described above is 4 omitted, and a coupling capacitor 20 is connected between the cont-rol grid 2 of the valve 1 and the anode 21 of a triode thermionic valve 22. ln addition a variable resistance 23 is connectedbetween the control grid 2 and the high tension voltage supply line 9. An anode load resistor 24 is connectedV between the anode 21 of the valve 22 and the high tension voltage supply line 9, its cathode 25 yis earthed, and its control grid 26 is connected to the junction of a pair of resistors 27 and 28 whichl are connected in series between the anode 10 of the valve 1 and a point at a negative potential. In addition a coupling capacitor 29 is connected between the anode 21 of the valve 22 and an input terminal 30. The arrangement is such that normally the valve 1 is conducting and the valve 22 is non-conducting, its control grid 26 being held at a sufficiently negative potential. On application of a short negative-going impulse to the input terminal 3i), the circuit is triggered to the condition in which the valve 1 is non-conducting and the valve 22 is conducting. The circuit remains in this state for a time interval, the duration of which is determined by the magnitude of the variable resistor 23 and the capacitor 20. At the end of this interval it changes rapidly back `to its initial condition. In this way, on application cf a short negative pulse to the input terminal 30, an effectively rectangular negative impulse is applied to the control grid 2 of the valve 1, the rectangular pulse having a duration which is predetermined by the circuit constants.

It will be appreciated that apparatus employing the same principle of operation but incorporating transistors instead of thermionic valves may also be provided.

Apparatus for generating pairs of pulses of predetermined duration and having a predetermined time interval between them has many applications. One important application is in radar systems, where it is required to generate what are known as early and late strobe pulses from a synchronising pulse derived from the transmitter trigger circuits.

I claim:

1. Electric pulse generating apparatus comprising an electric pulse source for supplying a trigger pulse having sharp leading and trailing edges, a pair of parallel resonant circuits both having the same natural period which is short relative to the duration of said trigger pulse, means having an input path to pass a current pulse simultaneously through both said resonant circuits for a period equal to the duration of a pulse applied to said input path, means connecting said pulse source and the input path to supply the trigger pulse to the input path, two asymmetrically conducting devices which are each connected across one of said parallel resonant circuits so that a damped oscillation, consisting substantially of a single half cycle, `is excited in each resonant circuit in turn by the current pulse, one in response to the leading edge of the current pulse, and one in response to the trailing edge, and an output circuit coupled to both the resonant circuits so that the damped oscillations excited therein by the current pulse produce in the output circuit two pulses respectively which are of the same polarity.

2. Electric pulse generating apparatus according to claim l wherein the inductances of the two resonant circuits are mounted on a common core.

3. Electric pulse generating apparatus according to claim 2 wherein a third coil is also mounted on said core S0 as to lie between the inductances of the two resonant circuits, output terminals being connected across the third coil.

4. Electric pulse generating apparatus comprising a thermionic valve of the kind having an anode, a cathode and at least one control electrode, means to supply a trigger pulse having sharp leading and trailing edges to the control eletcrode of the valve, a pair of parallel resonant circuits which both have the same natural period that is short relative to the duration of said trigger pulse and which are connected one in the anode circuit and one in the cathode circuit of said valve, two asymmetrically conducting devices which are each connected across one of said parallel resonant circuits so that a damped oscillation, consisting substantially of a single half cycle, is excited in each of said resonant circuits in turn upon the occurrence of a trigger pulse, one in response to the leading edge of the trigger pulse and one in response to the trailing edge, and an output circuit coupled to both the resonant circuits so that the damped oscillations excited in the two resonant circuits by a trigger pulse produce in the output circuit two pulses respectively which are of the same polarity.

5. Electric pulse generating apparatus `according to claim 4 wherein the said thermionic valve and another thermionic valve `are connected to form a monostable trigger circuit, this trigger circuit constituting the said means to supply a trigger pulse.

References Cited in the tile of this patent UNITED STATES PATENTS Grieg et al Aug. 26, 1947 Hopper June 22, 1948 Grieg July 6, 1948 Chatterjea et al. Nov. 2, 1948 Cleeton Feb. 20, 1951 Lange May 22. 1951 Schlesinger Nov. 6, 1951 Hoeppner et al. Ian. 15, 1957 OTHER REFERENCES Chance et al.: Waveforms, April 1949, page 551,

15 Fig. 15-3.

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