US2416114A

US2416114A - Pulse amplifier

Info

Publication number: US2416114A
Application number: US547872A
Authority: US
Inventors: Richard B Nelson
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1944-08-03
Filing date: 1944-08-03
Publication date: 1947-02-18
Anticipated expiration: 1964-02-18

Description

Feb. 18, 1947.' R. B. NELSON PULSE AMPLIFIER Filed Aug. 3, 1944 UTILIZATION DEV/CE UTIL/ZAT/OA/ DEVICE PULSE... sauna:

Inventor: Richard BNeIson,

His Attorn ey.

Patented Feb. 18, 1947 PULSE AMPLIFIER Richard B. Nelson, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application August 3, 1944, Serial No. 547,872

8 Claims.

This invention relates to devices for amplifying electn'cal pulses and particularly to electronic pulse amplifiers of the type adapted to draw current only durin the amplification of the pulses.

In apparatus such as radio locating and range finding devices which employ electrical pulses of short duration, it is desirable that the amplifiers used be provided with electron discharge devices or tubes which are conducting only durin the amplification f the pulses so that minimum power is required and longer life of the tubes is possible. In order to render the electron discharge devices conducting only during the amplification of the pulses, the several devices are biased beyond cutoff so that only a pulse in the positive sense will render the devices conducting. Obviously it is necessary to invert the pulses between any two stages in order to provide a positive pulse to render conducting the electron discharge device of the second stage. This inversion of the pulses has been accomplished, for example, by the use of pulse transformers between the stages. However, these transformers have not been entirely satisfactory because of some resulting distortion of the wave form of the pulses. Accordingly, it is an object of this invention to provide a pulse amplifier including an improved arrangement for minimizing the power consumption of the amplifier while maintaining the desired pulse wave form.

It is another object of this invention to provide a pulse amplifier or" the type which employs normally nonconducting electron discharge devices and includes an improved arrangement for facilitating amplification of pulses without distortion and. with a predetermined time delay.

The novel features which are believed to be characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing in which Fig. 1 represents one embodiment of the invention; Fig. 2 illustrates graphically the manner of operation of the amplifier of Fig. l; and Fig. 3 represents another ernbodi ment of the invention.

Referring now to Fig. l, the pulse amplifier illustrated comprises electron discharge devices l and 2 connected to provide two stages of ampli fication between a suitable source of pulses 3 and a utilization device 4. The device I is provided with a cathode 5, an anode 6 and a control electrode 1. The pulses generated by the apparatus 3 are impressed on the control electrode 7 across a suitable resistor 8. A suitable negative bias voltage is provided for the electrode 7 to render the device i normally non-conducting and, in the embodiment shown, a battery 9 has been illustrated for providing the bias. The generating apparatus It is arranged to impress the pulses on the control electrode 1 in a positive sense so that the device l is rendered conducting for the duration of each pulse. The anode 6 is connected through a resistor it to a suitable source of anode potential indicated as a battery I 1.

When a positive pulse as indicated at l2 in 2 is impressed on the control electrode 1 with sunicient intensity, it overcomes the bias of the device l to render the device conducting and produces a negative pulse across the resistor it! as indicated at i3 in the middle curve of Fig. 2. The anode 5 of the device i is coupled through a capacitor hi and a resistor to the control electrode of the device 2 indicated at to. The device 2 is provided with a cathode ll and an anode i8, and the utilization device is connected in the anode tmcathode circuit of the device 2 in any suitable manner. The device 2 is biased to be normally nonconducting by a battery :9 connected between the cathode i? and control electrode it to maintain a negative bias on the control electrode, this being the bias indicated in the middle curve of Fig. 2. When the negative pulse i3 is impressed on the control electrode IE, it has no eifect on the device 2, which K remains nonconducting. In order to provide a positive pulse of the same wave form and duration as the pulse 52 and to impress this pulse on the control electrode 56, an artificial transmission line 29 is connected with its input terminals across the resistor l5 and with its terminals at the other end short circuited. When the pulse I3 is impressed on the transmission line across the resistor is, it travels down the line to the short-circuited end where it is reflected in the inverted sense and returns to appear across resistor is as a positive pulse as indicated at 25 in Fig. 2. The pulse 26 is of sufiicient intensity to overcome the bias of the device 2 and render the device conducting so that a negative pulse appears at the output of the device 2 as indicated at 22 in Fig. 2. The pulses 2i and 22 are delayed a predetermined interval of time de pending upon the time constant of the transmission line 28, the length of time between the beginning of the pulse l3 and the beginning of the pulse 2! being equal to twice the time constant of the line. The resistor it is selected to have a value equal to the characteristic impedance of the transmission line 2c in order to prevent any further reflections of the pulse after it has returned to the resistor it from the far end of the line. The wave form of the pulse produced at the output of the device 2 is the same as that or the pulse impressed on the control electrode 7 of the device is. The time constant of the transmission line is selected to be of any suitable value greater than the duration of the pulse and dependent upon the delay desired in the particular apparatus with which the amplifier is being employed. It will readily be understood by those skilled in the art that such a time delay may be desirable, for example, in ap paratus employing cathode ray signal portraying tubes in order to insure the initiation of the cathode ray sweep before the occurrence of the signal pulse which it is desired to observe. It is also obvious that any type of artificial transmission line may be employed which is capable of producing the desired time delay.

The embodiment of the invention illustrated in Fig. 3 is similar to that illustrated in Fig. 2 and corresponding parts have been designated by the same numerals. The modification of Fig. 3 diffrom that of Fig. 2 in that a four terminal symmetric transmission line is employed as indicated at 23. A transmission line of this type comprises two conductors each of which is a symmetric part of the circuit, the two conductors having equal series impedance. The two terminals at the input end of the transmission line 23 are connected across th resistor it, the upper terminal being connected to the anode ii and the lower terminal to a suitable point of fixed. reference potential, such as ground, through a bypass condenser 2d. At the other or output end of the transmission line 23 the conductor which is connected to the anode 5 at its input end is connected to ground, while the conductor which is grounded at the input end is coupled to the control electrode it of the device 2 through a condenser 25 and the resistor E5. The time constant of the transmission line 23 is selected to be equal to the total delay time required between the pulse at the input of the device I and the pulse at the output of the device 2. The operation of the embodiment of Fig. 3 is the same as that of the embodiment of Fig. 1 and the curves of Fig. 2 may considered as representing the operation of the circuit of Fig. 3. When the negative pulse 13 is impressed across the resistor it in Fig. 3, it appears simultaneously at the output end of the transmission line so that it is impressed on the control electrode It but has no eifect upon the device 2. The pulse is is followed after a delay determined by the time constant of the transmission line 23 by the inverted pulse 2! in the positive sense which renders the device 2 con ducting so that the amplified pulse 22 appears at the output of the device 2. The delayed pulse 2! is inverted because of the reversed connections of the terminals at the output of the transmission line, the voltage appearing between ground and the control electrode it in the opposite sense from that in which it was impressed across t-e resistor iii. The appearance of the negative pulse it simultaneously across resistor it and at the control electrode it occurs because the ground connection provides in effect a,third conductor for the transmission line.

In the foregoing it is readily apparentthat there has been provided a simple and efiective amplifier for reproducing a signal pulse in the same wave form with a predetermined time delay while maintaining the electron discharge devices of the amplifier normally nonconducting.

While particular embodiments of the invention have been illustrated and described, other applications will readily be apparent to those skilled in the and it is intended by the appended claims to cover all modifications which fall within the spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

A pulse amplifier comprising means for generating a signal pulse in a negative sense, means for amplifying a signal pulse which is impressed thereon in a positive sense, and means including a transmission line connected to said generating means and to said amplifying means for impressing the generated pulse both simultaneously in the samesense and after a predetermined time interval in the opposite sense on said amplifying means whereby said amplifying means amplifies and reproduces said negative signal pulse a predetermined time interval after the generation thereof.

2. A pulse amplifier comprising first and second electron discharge devices each having a cathode and an anode and a control electrode, means for impressing on the control electrode of said first device a signal pulse to be amplified whereby said pulse appears simultaneously in an inverted sense at the anode of said first device, and means including a transmission line connected to the anode of said first device and to the control electrode of said second device for impressing the amplified pulse both simultaneously in the same sense and after a predetermined delay in the opposite sense on the control electrode of said second device.

3. A pulse amplifier comprising first and second electron discharge devices each having a cathode and an anode and a control electrode, means for impressing on the control electrode of said first device a signal pulse to be amplified, means including a transmission line having a predetermined time delay for coupling the anode of said first device and the control electrode of said second device whereby said pulse is amplified by said first device and appears in an inverted sense on the control electrode of said second device simultaneously and is followed at the end of a period determined by the time delay of said transmission line by a second pulse on the control electrode of said second device and in the same sense as the original pulse.

4. A pulse amplifier comprising first and second electron discharge devices each having a cathode and an anode and a control electrode and each biased to be normally nonconducting, means for impressing on the control electrode of said first device and in a positive sense a signal pulse to be amplified whereby said pulse appears simultaneously in an inverted sense at the anode of said first device, and means including a transmission line connected to the anode of said first device and to the control electrode of said second device for impressing the amplified pulse both simultaneously in the same sense and after a predetermined delay in the opposite sense on the control electrode of said second device whereby said second device is rendered conducting to amplify and reproduce said pulse at the anode of said second device a predetermined time after the impressing of said pulse on the control electrode of said first device.

5. A pulse amplifier comprising first and second electron discharge devices each having a cathode and an anode and a control electrode and each biased to be normally nonconducting, means for impressing on the control electrode of said first device and in a positive sense a signal pulse to be amplified, a resistor connected between the anode and cathode of said first device whereby said pulse is amplified and appears in an inverted sense across said resistor, a transmission line having terminals at one end connected across said resistor for producing a delayed pulse in the opposite sense from the pulse across said resistor, said resistor having an impedance equal to the characteristic impedance of said line, and means for impressing said delayed pulse on the control electrode of said second device whereby said original signal pulse is amplified and appears in an inverted sense at the anode of said second device a predetermined interval after it is impressed on the control electrode of said first device.

6. A pulse amplifier comprising first and second electron discharge devices each having a cathode and an anode and a control electrode and each biased to be normally nonconducting, means for impressing on the control electrode of said first device and in a positive sense a signal pulse to be amplified, means for coupling the anode of said first device and the control electrode of said second device, a resistor connected between the anode and the cathode of said first device, and a transmission line having terminals at one end connected across said resistor and having its terminals at the other end short circuited whereby the pulse appearing at the anode of said first device is inverted and impressed after a predetermined time upon the control electrode of said second device to render said second device conducting and to reproduce said pulse with substantially the same wave form at the anode of said second device.

7. A pulse amplifier comprising first and second electron discharge devices each having a cathode and an anode and a control electrode, means for impressing on the control electrode of said first device a signal pulse to be amplified, means including a two-conductor symmetric transmission line arranged to couple the anode of said first device and the control electrode of said second device for impressing the amplified pulse on the control electrode of said second device in an inverted sense and after a predetermined time delay, one of the conductors of said transmission line being connected at the input end of said line to the anode of said first device and at the output end to a point of fixed reference potential, the other conductor of said transmission line being connected at the input end to a point at said fixed reference potential and at the output end to the control electrode of said second device, and a resistor having an impedance equal to the characteristic impedance of said transmission line connected between said two conductors at one of said ends of said line.

8. A pulse amplifier comprising first and second electron discharge devices each having a cathode and an anode and a control electrode and each biased to be normally nonconducting, means for impressing on the control electrode of said first device and in a positive sense a signal pulse to be amplified, a resistor connected between the anode and the cathode of said first device and having its end remote from said anode connected to a point of fixed reference potential, means including a two-conductor symmetric transmission line having its input terminals connected across said resistor and its output terminals connected between the control electrode and cathode of said second device for impressing the amplified pulse delayed and in an inverted sense on the control electrode of said second device, one of the conductors of said line having its input end connected to a point at said fixed reference potential and the other conductor having its output end connected to a point at said fixed reference potential, said resistor having an impedance between said input terminals equal to the characteristic impedance of said line,

RICHARD B. NELSON.