US2438910A

US2438910A - Pulse generator

Info

Publication number: US2438910A
Application number: US514999A
Authority: US
Inventors: Donald D Grieg
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC; Federal Telephone and Radio Corp
Priority date: 1943-12-20
Filing date: 1943-12-20
Publication date: 1948-04-06
Anticipated expiration: 1965-04-06
Also published as: BE474797A; ES182177A1

Description

April 6; 1948.'

D. D. GRIEG PULSE GENERATOR Filed Dec. 20, 1943 2 Sheets-Sheet :1

IN VEN TOR. DON/M0 0. G/P/fG ATTORNEY April 6, 1948. D. D. GRI EG PULSE GENERATOR Sheet 2 Filed Dec. 20, 1943 2 Sheets Q0 7 W i 5 on E U P WY m IMMJ a 4 R 6 m M 4 n b d n 4 m w a a 1n 6 M1 W MW w 6 c e a c C E "a Q 6 l 5 L=r| M m o m a l a 6 a W M M 5 a w g 1 aai A J INVENTOR DON/1Z0 0. 6/1 /56 ATTORNEY 17E VERSE? 3 torted pulse shape which is the algebraic sum of the two input voltages. The resulting shape for the mixed voltages of curves at and b is shown in curve 0. Since the leading edge 32 of the sawtooth is inclined, the mixing of the two Voltages cancels out the overlapping portions thereof leaving those portions of the two voltages which are not overlapped by the other voltage. Thus, the leading edge portion of the input pulse occurring ahead of the saw-tooth produces a sharp positive pulse portion 40 while the trailing edge portion of thesaw-tooth which extends beyond the trailing edge 2% of the input pulse produces a negative edger pulse portion 42. By a clipping operation at the zero axis of the energy of curve the edger pulse portion 42 is obtained as indicated by curve d, the vertical leading edge portion 42a corresponding to the vertical trailing edge 26b of the input pulse and the trailing edge 4212 being curved exponentially like the trailing edge 35 of the saw-tooth.

I1 saw-teeth are desired, the clipping level may be lowered from the zero axis as indicated by level 45 whereby saw-teeth 46 (curve e) having substantially linearly sloping trailing edges are obtainable.

In Fig. 3 I show a second embodiment of the invention whereby both positive and negative edger pulses are produced. This circuit includes a. resistance-capacitance circuit to which input pulses 50, curve 1, Fig. 4, are applied. The circuit includes a resistor R connected in series with a condenser C to ground. The output.52 of this circuit is taken ofl at the interconnection between elements R and C. The RC values of this circuit alter the shape of the rectangular input pulse substantially as indicated at 54, curve 9. It will be understood. of course, that the curved edges of the shaped pulse 54 may be varied according to the relative values of the elements R. and C. It will be readily apparent, however, that for the duration of the input pulse 50, the circuit values may be such as to provide a condenser charging rate as indicated by the leading edge 540., and a discharge rate as. indicated by the curved trailing edge 54b.

Theinput pulses are also applied to a phase reverser 6!) whereby they are reversed in polarity as indicated at 6| curve h. The

output connections

52 and 62 of the RC circuit and the phase reverser 60 may be applied to any known mixer' circuit 64 wherein the twopulse energies 54 and BI are added algebraically to produce an output wave 65, curve i having two edger pulse portions. The first edger pulse portion is negative and is defined by a vertical edge 65a which corresponds to the vertical edge Bio of the rectangular pulse GI and a curved trailing edge 65b which corresponds to the curved leading edge 54a. The second edger pulse portion is positive and is defined by a vertical edge 650 which corresponds to the vertical trailing edge Elb of the rectangular pulse GI and a curved trailing edge 65d which corresponds to the curved edge portion 54b.

The mixer 64 may comprise, for example, a known hybrid coil for mixing the two pulse energies, or a known T-pad resistor network may be used. Mixers of this character may be used where elimination of vacuum tubes is important. The transformer and resistor types of mixers, however, have the disadvantage of distorting somewhat the frequency and shape of the pulse waves. Such distortion, however, can be kept small and therefore may be tolerated in many applications of the invention.

Either of the two edger pulse portions BSa-b or 65cd is obtainable by a clipping operation performed bya known clipper 10 having a clipper tube and a phase reverser tube with output connections H and 12 with respect to a ground connection 13, whereby the positive pulse portion B5cd is obtainable on output connection "II and negative pulse. portions 6511-4) are obtained from output connection 12 by the required clipping operation.

It will be observed that the negative pulse portion BEa-b has the vertical leading edge thereof in coincidence with the leading edge of the rectangular inputpulse 50, and that the leading edge 65d of the positive pulse portion is in coincidence with the trailing edge of the input pulse 50. Thus, the positive edger pulse 65cd is actually retarded an amount corresponding to the width of the input pulse with respect to the leading edge of the input pulse. Any retardation desired for an output edger pulse may be'obtained by extending,by means of a multivibrator or other rectangular pulse generating circuit; the input pulse a width equal to the desired retardation effects desired.

It will be understood, also, that either of the output edger pulses may be reversed by applying the same to a phase reverser. or, if desired, the input pulse 50 may be reversed from positive to negative polarity prior to its application to the circuit. This would have the 'elfectof reversing the polarity of the pulses of curves 1' and k.

In Fig. 5 I show a third embodiment which is similar to the embodiment shown in 'Fig.p3--except that the mixer .unit 64a comprises two vacuum tubes 8 I and 82., The RC output connection 52 is applied to the grid of tube 8|. In order to provide a grid leak which will not short-circuit the condenser C, I connect the input connection 5| through a resistor 83 to ground. The output connection 62 of phase reverserfil] is connected to the grid of the tube 82. The plate connections 86 and 81 of the two tubes 81 and 82, respectively, are suppliedwith plate current through load resistor 90. The output connection 92 fOr the mixer unit is connected to the clipper circuit l0.

The two tube feature of the mixer unit, provides separate cathode biasing means em and 82a, whereby each tube can be biased according to the character of input energy. For the pulse energies shown, tube BI is provided withagreater negative bias than tube 82.

In operation, the positive input pulse 55) produces a shaped pulse 5%! similarly as in the. circuit of Fig. 3. Likewise, phase reverser Gilreverses the input pulse 58 as shown at El prior to its application to themixer. The tube 8| reverses the polarity of the shaped pulse 54 as shown at 84. Likewise, the pulse 6| is reversed in polarity by tube 82 as shown at 85; The resulting pulse output across the load resistor is shown at 95. It will be observed that due to the reversing functions of this circuit the positive pulseportion a occurs in time relation with the leading edge portion of the input pulse 50 and the negative pulse portion 95b is timed with thetrailing edge portion of the input pulse 50. This is the reverse to the polarity output of, the circuit of Fig. 3. The clipping operation of clipper-10 in Fig. 5 is the same as described for Fig. 3 whereby pulse portions 95a and 952) are separately obtainable from connection H and 72.

Thetube mixer unit 64a of Fig. 5 is to be preferred over the hybrid coil or T-pad mixer arrangements hereinbefore referred to for mixer 64 in Fig. 3. The tube mixer, for example, is free from any frequency or wave distortion that may be present in the simpler forms of mixer units.

While I have described above the principles of my invention in connection with specific apparatus, and particular modifications thereof, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of my invention and the accompanying claims.

I claim:

1. The method of producing an edger pulse comprising producing from a rectangular input pulse a shaped pulse at least one edge of which is curved, mixing the energy of this shaped pulse with the input pulse energy in opposite polarity to said input pulse to produce a pulse portion one edge of which is substantially vertical according to one of the vertical edge portions of the input pulse, and the other opposite edge is curved according to said curved edge, said vertical edge portion being contiguous to said opposite curved edge.

2. The method defined in claim 1 wherein the produced shaped pulse is of a generally saw-tooth shape having a fiat end portion which approaches in width the width of the input pulse, whereby the mixing operation subtracts from the sawtooth shaped pulse the portion thereof which includes said flat end portion.

3. The method defined in claim 1 wherein the produced shaped pulse is of a shape having curved leading and trailing edges, whereby the mixing of the input pulse therewith operates to produce two pulse portions one pulse portion being defined by the vertical leading edge of the input pulse and said curved leading edge and the other pulse portion being defined by the vertical trailing edge of said input pulse and said curved trailing edge.

4. A system for producing edger pulses from substantially rectangular pulses comprising means for producing in response to a rectangular input pulse a shaped pulse at least one edge of which is curved, mixer means, means to apply energy of said shaped pulse to said mixer means,

and means including a phase reverser to apply energy of said input pulse to said mixer means of opposite polarity to the polarity of said shaped I pulse, whereby they combine algebraically to produce a pulse portion one edge of which is substantially vertical corresponding to one of the edges of said input pulse and the other edge of which is curved according to said one curved edge.

5. The system defined in claim 4 wherein the shaped pulse producing means comprises a condenser, a vacuum tube having an input grid, a plate electrode and a cathode electrode, means to supply the plate electrode with current to charge said condenser, whereby energy of an input pulse causes said tube to conduct and to rapidly discharge said condenser, and said grid 6 having means to bias the tube negatively so that, at the termination of said input pulse, said tube returns to cut-off permitting the condenser to recharge and thereby produce the curved edge for said shaped pulse.

6. The system defined in claim 4 wherein the shaped pulse producing means includes a resistance-capacitance circuit of a time constant such that the leading edge portion of the input pulse is translated into a curved edge for substantially the duration of the input pulse and the trailing edge is extended in a curved exponential shape.

7. The system defined in claim 4 wherein the shaped pulse producing means includes a resistance-capacitance circuit of a time constant such that the leading edge portion of the input pulse is translated into a curved edge for substantially the duration of the input pulse and the trailing edge is extended in a curved exponential shape, and said mixer means includes vacuum tubes, one for each pulse energy input, whereby the shaped pulse energy and the rectangular pulse energy are inverted in polarity before they are mixed, the tube for receiving the shaped pulse energy having a grid leak resistor connected to the input of the resistance-capacitance circuit.

8. A system for producing from substantially rectangular pulses positive and negative edger pulses wherein one edge of each such pulse is substantially vertical and the opposite edge is curved, comprising a resistance-capacitance circuit the time constants of which translates the leading edge of each rectangular input pulse into a curved edge for substantially the duration of the input pulse and translates the vertical trailing edge of the input pulse into a curved exponential edge, a mixer, a phase reverser, means for applying energy of each rectangular input pulse to said phase reverser, means for applying the output of said phase reverser to said mixer, means to apply the curved pulse output of said resistance-capacitance circuit to said mixer, whereby the reversed input pulse energy is combined algebraically with the curved pulse shape in opposite polarity to produce a negative pulse portion the leading edge of which corresponds to the leading edge of said rectangular input pulse and the trailing edge portion of which corresponds to the leading curved edge of said curved pulse, and a positive pulse portion the leading edge of which corresponds to the vertical trailing edge of said rectangular input pulse and the trailing edge of which corresponds to the curved trailing edge of said curved pulse, and clipper means for separating the two pulse portions.

DONALD D. GRIEG.

REFERENCES CITED UNITED STATES PATENTS Name Date Kell July 18, 1939 Number