US2589807A

US2589807A - Electrical integration circuit

Info

Publication number: US2589807A
Application number: US574374A
Authority: US
Inventors: William A Higinbotham
Original assignee: US SEC WAR
Current assignee: United States, WAR, Secretary of; US SEC WAR
Priority date: 1945-01-24
Filing date: 1945-01-24
Publication date: 1952-03-18
Anticipated expiration: 1969-03-18

Description

March 1952 w. A. HIGINBOTHAM 2,589,807

ELECTRICAL INTEGRATION CIRCUIT Filed Jan. 24, 1945 GATE GENERA TOR VAR/A BLE E DELAY C/RCUI r uv ur WA v5 GENE/7A TOR TIMER INVENTOR.

W/L L /AM A. H/G/NBOTHA M Patented Mar. 18, 1952 r rice ELECTRICAL INTEGRATION CIRCUIT William A. Higinbctham, Santa Fe, N. Men, as-

signor, by mesne assignments, to the United States of America as represented by the Secretary of War Application January 24, 1945,:SerialNo; 574,374

Claims. 1

'Thisiinvention relates to an electrical apparatus and'mcre particularly to a'wave modifying circuit adaptedtoperform'integration operations. Morespecifically, the circuit is adapted to develop :an outputwave form representing an integration of an input wave form.

One object of the invention is to provide such a circuit whereby the output wave form represents an integration of a waveform which is a selected function of "an independent variable.

Another object is to provide such a circuit whereby :a desired output voltage may be developed.

A further object contemplates the production of suchoutput wave forms between predetermined limits of :an independent variable.

The'apparatus herein has'many applications and, as an example, it may be used in cathode ray tube deflection voltage circuits of radio object detecting and ranging systems.

The apparatus here disclosed operates to generatea recurring output wave in which each'wave' -form represents an integration of an input wave form. Thus, the amplitude of an out ut wave form atany instant represents'an evaluation at that-instant of'the inte ration of the input wave form-from a lower limit wh ch may bepredetermined-as will'appear hereinafter. The amplitudes of thewave-forms are functions of an independent variahlewhich is represented by a time axis, the initiation of each input wave form corresponding to zero value of the independent variable.

Atypical use of this integrating circuit may be to generate, asshown in'the communication s stem describedin the patent-to Luis W. Alvarez, Patent *No. 2,480,208, -fi'ed June 27, 1944, and issued August 30, 1949, recurring output wave forms each having a voltage which is proportional to the algebraic expression 1 -71 In'this expression, 1 (range) is the independent variable, andh (height) is a constant whose value may be varied as desired. The expression r -h is itself proportional to an integration, from a lower limit 71.. of a voltage which varies linearly with r. As-r is represented by time, the voltage of the input wave form used herein varies linearly with time and may be produced by a saw-tooth generator.

In the drawing:

Fig. 1 is a diagram, partly in block representation, of a circuit which will perform integrations upon an input wave form;

Figs. 2 and 3 are dia rams showing wave forms present in various parts of the circuit; and

Fig. 4 is a diagram of a typica output voltage wave form produced by the circuit from a selected input wave form.

Referring now to Fig. l, the present integrating circuit includes several components which are well .known :to the :art and are therefore representedinblockiorm. Such components will-not be dealt with in detail except insofar as is necessary to describe the present invention. Reference :numeral :5 designates a timer which produces-recurring triggervoltage pulses 6 of relatively short duration, for example,-2 or 3 microseconds. These trigger pulses are applied ,toian input wave generator I :to time or trigger the production of voltage waves having a predetermined form. Suchan input-Waveformmay as mentioned above, have a voltage which varies linearly with timeasshown at 8.

The :wave forms shown on-the diagram in Fig.1 are drawn in their relative positions along 13a common time base. For examplewave form8 is shown astinitiated at the instant of occurrence of a trigger ,6. The repetition rate of the trigger pulses 6 and the'time duration'of the input waves 8, if desired, may be such as to space the input waves along the time axis by a time duration equal to or, greater thanthe duration of an input wave.

A lead [0 from input wa-ve generator l-applies the 'voltage'wave form 8 to a control grid llof a vacuum tube H2. The control grid H is connected through a resistance l3 to a ground point of the circuit. The tube I2 may be-of pentode type as shown, having ascreen grid 14130 which is applied apositive voltage of constant value. A suppressor grid l5 and a cathode l6-are connected together and througha biasing resistance I! to ground. Plate N3 of the tube ['2 is connected to one terminal of arelativey large capacitance 19 at a junction 2G,-the other terminal of the-capacitance being connected to a junction 25. A positive voltage of constant value is applied, as shown, to the'junction 25 from a source having a low impedance to ground for alternating voltage components. I

During circuit operation, a recurring unidirectional current is produced in the plate IB-capacitance I9 circuit due to the recurring input voltage applied to the control grid ll, and to the periodic discharge of the capacitance I9, as will be presently described.

As will appear hereinafter, the pate potential at the junction .23 undergoes variations which, however, are small compared to the constant voltage applied to the junction 25. The tube l2 is of the constant current.type whose characteristic is that. despite'such variations of plate potential, the plate current is substantially dependent only upon the voltage applied to the control grid I l. The operating conditions of the tube 12 are such as tosecure a linear relation between its plate current and control grid votage, the variation of plate voltage having negligible efiect on this relationship overthe range of operation. Thus, th e varying currentproduced in the .delay circuit 55.

.the voltage wave 8 applied to the control grid H causes a corresponding electron current wave to flow in the cathode-plate circuit of tube I2. As will appear hereinafter, a selected time-portion of this current flows through the integrating capacitance 19 in the direction of junction 20 to junction '25, resulting in an integration voltage wave at the terminal with respect to terminal 20. Junction 25 is effectively at ground potential so far as varying voltages are concerned, so that a voltage wave 30, which is an inversion of the desired integration Wave form, is present at terminal 20.

' The voltage wave appearing at the junction 20 is communicated to a control grid 3| of an amplifier vacuum tube 32 through a couplingv capacitance 33; The control grid 3| is connected through a resistor 34 to ground. Vacuum tube 32 may be of triode type as shown, having a plate 35 which is connected to a junction 36 and thence through resistance 31 to the positive potential at the junction 25. Cathode 38 of the vacuum tube 32 is connected through a biasing resistance 39 to ground. The operation of the vacuum tube .32 is linear, and the varying potential developed at the junction 36 is an inverted replica of the voltage wave 30 applied to the grid 3|. Junction 36 may be connected, as shown, to an output terminal 40 through a coupling capacitance M.

A voltage wave 42 at the terminal 40 is thus the desired integration of the input voltage wave form applied to the control grid 1 I of the tube 12. As mentioned previously, the capacitance I9 is periodically discharged and maintained in a ,short-circuited condition for a predetermined time interval in order that recurring waves of voltage may be formed at the junction 20. Additionally, by causing the capacitance to become unshorted at a selected time after initiation of each input wave form, the output voltage wave willrepresent an integration of the input wave from a lower limit represented by that selected time. This is accomplished in the following manner.

The trigger pulses 6, in addition to being applied to generator i, are also applied to a variable Here a selected time delay, representing, for example, the quantity h previously mentioned, is imposed on the trigger pulses 6 resulting in time-displaced trigger pulses 5!. The time interval between the original and delayed trigger pulses may be varied as desired by a control 52, which adjusts circuit constants within the said variable delay circuit to produce the predetermined time delay. The said control 52 may be adjustable manually, or automatically, in response to some condition. As shown in the previously mentioned copending application. for example, such apparatus may be mounted in an aircraft, and a height-responsive device may, by suitable linkage, position the control 52. V

' The delayed trigger pulses 5! are applied to a gate generator 53 to time or trigger the cycles of a rectangular wave 54, said rectangular wave therefore having the same frequency as the input voltage 8. The relatively negative and positive portions of rectangular wave 54 may have equal time durations (or they may have unequal time durations), and these portions will hereinafter be termed negative and positive gates, respectively. The gate generator is so designed that the leading edge of a negative gate is produced by, and is thus in time-phase with, a delayed trigger pulse 5|.

A lead 55 from the gate generator 53 applies the rectangular wave 54 to a control grid 56 of a vacuum tube 51. Tube 51 may be of triode type as shown, having a plate 58 and a cathode 59 connected to the

junctions

25 and 20, respectively, of the capacitance IS. The potential of the control grid 56 with respect to'the cathode 59 determines Whether or not the tube 51 forms a short circuit across the integrating capacitance I9, and the tube 51 is therefore referred to as a switch tube.

Thus a positive gate of wave 54 causes the tube to conduct and effectively short circuit capacitance I9. A negative gate portion of the rectangular wave causes removal of the efiective short circuit across the integrating capacitance, and

the plate current of the tube [2 will at such time become a charging current for the integrating capacitance.

This condition is shown in greater detail in Figs. 2 and 3, in which a rectangular wave applied to switch tube 51, and a charging current of capacitance l9, respectively, are drawn to the same time scale indicated by the horizontal axes designated t. The vertical axes of Figs. 2 and 3 represent voltage and charging current, respectively, so designated by reference characters '1; and i.

Referring again to tube [2, there is at all times during the time of an input wave 8 a continuous path for current flow through said tube, the'plate circuit being completed either through switch tube 57 during the time of a positive gate, or through capacitance l9 during the time that switch tube 51 is open-circuited by a negative gate. The dotted line of Fig. 3 represents that time-portion of plate current of tube l2 which is bypassed around capacitance l9 by switch tube 51 during the delay time interval corresponding, in the example given, to the quantity h. The occurrence of the leading edge of a negative gate (positioned along the time axis by variable delay circuit 50) thus determines the lower limit of the integration operation performed by the present circuit.

The resultant voltage developed, in this instance. across capacitance I9 is shown in Fig. 4, in which the axis designated V is a voltage axis. The wave form shown is proportional to an in tegration of the input wave form from the preselected lower limit it and is thus proportional. as stated above, to the desired expression r 'h This is also the wave form of the output voltage appearing at the terminal 441 as explained heretofore.

While there has been illustrated and described herein, but rather it is to be taken as defined it is apparent that variations and modifications may be made by those skilled in the art. It is to be understood that the scope of the invention is not to be limited to the precise details disclosed herein one embodiment of the present invention. by the following claims.

I claim:

1. A voltage generator including a source ofrecurring input voltage waves, each input voltage wave representing a function of an independent variable, a vacuum tube having at least a cathode, control grid and anode, an output circuit for said vacuum tube, said output circuit including a capacitance and normally closed switch means connected in parallel therewith, said source being connected to said control grid whereby input voltage waves are applied to said control grid, said vacuum tube being adapted to provide a recurring current wave in said output circuit, said current corresponding in form to said input voltage wave, a timing means, said timing means connected to said source and adapted to initiate each input wave, a variable delay circuit connected between said timing means and said switch means, said variable delay circuit cooperating with said timing means to open-circuit said switch means at a predetermined time after initiation of each input voltage wave, whereby a recurring output voltage wave is developed across said capacitance, said output voltage wave representing a definite integration of said function, the lower limit of integration correspondin to said predetermined time after initiation of each input voltage wave.

2.,A voltage generator including a source of recurring input voltage waves, each input voltage wave representing a function of an independent variable, a vacuum tube having at least a cathode, control grid and anode, an output circuit for said vacuum tube, said output circuit including a capacitance and normally closed switch means connected iniparallel therewith, said source being connectedto said control grid whereby input voltage waves are applied to said control grid, said vacuum tube being adapted to provide a recurring current wave in said output circuit, said current wave correspondin in form to said input voltage wave, and means "for opening said switch means after a predetermined time interval to permit a recurring output voltage wave to be periodically developed across said capacitance, said output voltage wave representing a definite integration of said function, the lower limit of integration corresponding to said predetermined time interval.

3. In an electronic integrating circuit of the character described having applied thereto a recurring input voltage wave, a vacuum tube having at least a cathode, control grid and anode, an output circuit for said vacuum tube, said output circuit includin a capacitance and switch means connected in parallel therewith, said control grid having applied thereto said input voltage wave, said vacuum tube being adapted to provide a recurring output current wave in said output circuit, said current wave corresponding in form to said input voltage wave, means for causing said switch means to short said capacitance until a predetermined time after initiation of each input voltage wave and to be unshorted during the remaining time of each input voltage wave, whereby a recurring output voltage wave is developed across said capacitance, said output voltage wave representing an integration of said input voltage wave from a lower limit corresponding to said predetermined time after initiation of each input voltage wave.

4. A voltage generator including a source of recurring input voltage waves, each input voltage wave representing a function of an independent variable, a first vacuum tube having at least a cathode, control grid and anode, an output circuit for said vacuum tube, said output circuit including a capacitance and normally closed switch means connected in parallel therewith, said switch means comprising a second vacuum tube having at least a cathode, a control grid and an anode, the said capacitance bein connected between said cathode and said anode, said source being connected to the control grid of said first vacuum tube whereby input voltage waves are applied to said control grid, said first vacum tube being adapted to provide a recurring current wave in said output circuit, said current wave corresponding in form to said input voltage wave, a timing means, said timing means being connected to said source and adapted to initiate each input wave, a gate generator having its output connected to the control grid of said switch means and a variable delay circuit connected between said gate generator and said timing means, said variable delay circuit cooperating with said timing means and said gate generator to open-circuit said switch means at a predetermined time after initiation of each input voltage wave, whereby a recurring output voltage wave is developed across said capacitance, said output voltage wave representing a definite integration of said function, the lower limit of integration corresponding to said predetermined time after initiation of each input voltage wave, and a vacuum tube amplifier having at least a cathode, a control grid and an anode, the said capacitance being connected in the grid-anode circuit of said amplifier, whereby the said output voltage wave may be amplified.

5. In an electronic integrating circuit of the character described having applied thereto a recurring input voltage wave, a vacuum tube having at least a cathode, control grid and anode, an output circuit for said vacuum tube, said output circuit including a reactance and switch means connected in parallel therewith, said control grid having applied thereto said input voltage wave, said vacuum tube being adapted to provide a recurring current wave in said output circuit, said output current wave corresponding in form to said input voltage wave, means for causing said switch means to short said reactance until a predetermined time after initiation of each input voltage wave and to be unshorted during the remaining time of each input voltage wave, whereby a recurring output voltage wave is developed across said reactance, said output voltage wave representing an integration of said input voltage wave from a lower limit corresponding to said predetermined time after initiation of each input voltage wave.

WILLIAM A. HIGINBOTHAM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,188,970 Wilson Feb. 6, 1940 2,212,967 White Aug. 27, 1940 2,241,619 Sherman May 13, 1941 2,282,340 Pieplow 1- May 12, 1942 2,300,189 Wolff Oct. 27, 1942 2,414,486 Rieke Jan. 21, 1947 2,489,312 Pacini 1 Nov. 29, 1949