US2541092A - Radio frequency pulse transmission - Google Patents

Description

Feb. 13, 1951 M, E 2,541,092

RADIO FREQUENCY PULSE TRANSMISSION Filed Aug. 6, 1938 l: W :ilE2 E 117: ;3

H1 I: I 1 F W r INVENTOR Babe/"t M Page ATTORNEY Patented Feb. 13, 1951 UNITED STATES PATENT OFFICE RADIO FREQUENCY PULSE TRANSMISSION Robert M. Page, Washington, D. 0.

Application August 6, 1938, Serial No. 223,503 20 Claims. (01. 250-17) (Granted under the act of March 3, 1883, as

This invention relates to a vacuum tube means for generating oscillations, and more particularly to a generator capable of producing oscillations in pulses of very short duration and high amplitude.

Among the several objects of this invention are:

To provide an oscillation generator capable of producing oscillations, for a very short interval, at a level much in excess of the rated output of the vacuum tube in the generator;

To provide an oscillation enerator that Will automatically and periodically produce pulses of oscillations, the duration of such pulses being very short in comparison to the interval between pulses;

To provide an oscillation generator of the type set forth that may be controlled to generate oscillations aperiodically.

In the drawing:

Fig. 1 depicts an embodiment of my invention wherein the potential applied to the anode is automatically controlled by a high resistance in series with the anode supply and a capacitance in parallel with the said resistance and the sourceof supply;

Fig. 2 illustrates another form of my invention;

Fig. 3 shows my invention with the capacitance above mentioned in shunt with the resistance only;

Fig. 4 illustrates graphically the operation of my novel generator;

Figs. 5 and 6 depict alternative connections for the parallel connected high resistance and capacitance. I I

I While the usefulness of the present invention is not limited to any one field, it is particularly useful as a transmitter of short waves for detecting, by reflected echoes, the presence of objectssuch as aircraft or ships, the determination of range, the operation of altitude and ground speed indicators, etc. .The distinguishing feature of the present invention is its capacity to generate and radiate radio frequency signals of extremely short duration and high amplitude. Signal pulses of less than one microsecond have thus been produced at power levels exceeding the tube ratings by a factor of 100 or more, without apparent damage to the tube after many hours of operation.

Fig. 1 depicts one embodiment of my invention that is, in some respects, conventional in that ;.;it 'is a self excited; tuned grid oscillator hair'ifi'g'th'e tunable-network tonnected to grid amended April 30, 1928'; 370 0. G. 757) 8 of tube 9 and coupled to the inductance Ill connected to anode ll of tube 9. By way of example of one use, the oscillatory networks are inductively coupled to a radiating half-wave doublet antenna l2, and a resistor I3 is connected between network I and cathode i l of tube 9 to function as an input impedance when a control or synchronizing voltage is impressed through leads l5 and It, the capacitance l1 serv ing as a bypass for radio frequencies.

A high resistance I8 is connected in series between source I 9 of anode supply and anode H and a capacitance 20 is connected from the anode supply lead to cathode M, the cathode being connected to the positive terminal of source 2| of the grid bias, and to the negative terminal of source l9 by lead 22. The bias on grid 8 is such as to prevent operation of the tube until the potential of anode I l reaches or exceeds a predetermined value. It is evident that capacitance 20 will be charged by source I9 through high resistance I8, that the potential of capacitance 20 will thus increase up to the voltage across the source l9 and that the potential applied to anode H will be the same as that of capacitance 2|] and hence will increase at the same rate as does the potential of capacitance 20. When the potential on anode H is sufficient to overcome the bias on grid 8 oscillations will be initiated. As soon as the tube 9 begins to pass current the capacitance 20 will discharge through the tube and will thus undergo a decrease in potential. Source I9 is unable to maintain the oscillations through resistance l8 and hence the operation of the tube will stop when the po- -tential of capacitance 20 has dropped to some definite value. However, the energy stored in capacitance 20 is suflicient to maintain the output of tube 9 at a level a hundred or more times greater than the rated output of the tube and this without damage to the tube owing to the very short duration of the oscillatory condition in comparison to the time required for the potential of capacitance 20 again to build up to such value that oscillations will be initiated.

It is evident that the duration of the pulses, or oscillatory condition, will be governed by the capacity of capacitance 20 and that the time between pulses will depend upon the product of the capacity of capacitance 20 multiplied by the value of resistance l8. It is also evident that there will be no radiation whatsoever from this novel generator between pulses.

It maybe desirable that the generation of 05- cillatioris lhould be controlled in some manner or should be synchronized with the operation of some other apparatus. This may be effected by giving the bias on grid 8 such value that the maximum potential applied to anode l i will be insulin cient to cause the tube to operate and if then a voltage be applied through leads l5 and E6 the bias on gnid *8 may @be changed so that the voltage on anode :1 l will be sufficient ito :cause the tube to pass current and a pulse of oscillations will be generated as above described. The voltage applied through leads l5 and may be either periodic or aperiodic under the conditions just discussed. It will be obvious to those skilled in this art that instead of applying the control voltage to the grid circuit it may seq-.ually well She applied instead to increase the voltage of anode II to such value that the bias on grid 8 will be overcome and the generator thereby caused to operate. Such a circuit is shown in Figure 2 where the control voltagemay be delivered to the anode voltage increasing means 25.

In the -.cir.cu-it-of Fig. 1.3 intermittent high amplitude .pulses are generated through the connection ofcondenser .20 in parallel with resistance 46. On initial operation .iollowi-ng connection of power .source 49, a very .=high amplitude impulse is generated, the anode current being delivered to condenser 28 which thereby is charged negatively to lower the anode voltage :and terminate the inipulse. The initial-conditions of charge are gradually restored through the flow of current from condenser .20 through ,resistor E8 to reestablish the minimum operative zanode potential for conduction. The :ouiescent period is controlled by the time .constantcf condenser .20 and resistor t8.

Fig-.4 shows the nature of the operation :of my invention in terms of variation of anode poten tial with time, the anode potentials being represented by ordinates and the time by .abscissas. Starting -:out with the potential of anode ii, that is the potential'of capacitance 2E1, at .zero the anode potential follows .the rising :course indicated by the cunve .23 .until it reaches the .value V1 .at which oscillations being and then .in time t, represented by line 24, the potential drops to the value Y-z-at which-oscillationscease. potential immediately begins to .build up and in the time I it again reaches the value V1 and @the .oscillatory condition .aga-in ensues, etc. Nothing .is

torbeinterned as to the relative yalues of Y1 and V2 or of -t and T, from the scale used in Fig. 4, this .fig-ure :being punely illustrative in its nature. In practice, T has been 60.01 more times 25. Thus, while .in an absolute sense thechamging period T may be \veryshort, the charging takes place slowly. relatively to the disc-hangs dining ,period .t. .Con uersely, the discharge is rapid relative to the charge. It is evident that the .value .of resistor 18 must besufiiciently great toquench oscillations when the potential has dropped to the value $12.

The circuit of Fig.3 .operates similarly, the cycle beginning with time t, condenser .26 charging negatively along line 24 during oscillation, and discharging through resistor it gradually to increase the anode potentialidu-ring time T.

The cincuit shown .in Rig. .5, in common with Fig. l, is provided with condenser to receiving current from the tube during the pulse and operating in conjunction with a tube electrode to control its potential to terminate the operating period. In Fig. :5 condenser 25 vis interposed between the cathode M and thenegative side of the power supply 19. It accumulates achar-ge space current flow to raise cathode it to a positiye yoltage which is eifeeii ees a negative grid bias to block oscillation. The charge is drained off gradually in the blocked period through resister 58 until the tube again becomes conductive, and in this respect the circuit resembles that of Fig. 3.

In the circuit of Fig. 6- the grid space current duringroperation isapplied to condenserz 0,, which, asshow-n in the grid-cathode-ccircuitand operates to shift the grid potential for blocking the oscillator at the end of the pulse, and maintaining the quiescent period during discharge through parallel resistor 138.

The high value of resistance i8 employed in Figs. 5 and 6 to effect periodic pulse generation has been tound ltoqiermit emission of pulse shorter by aiactor of ten than any other known method. It is 'further apparent that by employing space current through the tube itself to control the operating period, high power levels may be obtained without damage in a simple, self-protecting cincuit.

The greatly increased instantaneous output of the tube is due to the fact that the potentials oi sources t9 and 2.9 aseigreateit, by factors thatmay be as much as six or eight, than the corresponding ratedbperati-ng potentialso-f the tube.

This operation at excess voltage has the advantage of increasing yaouum tube emciency somewhat at all frequencies. It has the .added advantage of reducingelectron flight time, thus very materially increasing .efiiciency at .frequencies approaching the upper frequency limit of the tube .used. Where frequency limit is due toeleotron flight time, this method .of operation actually .raises the upper frequency limit of oscillation. For example, a certain type tube was tested in which at normal matings the efficiency fell off to .zero at 335 megacycles. In the of this invention, at three times normal volta e, efiicieney of 15 percent was ObtainedatBBOmegacycles.

The invention herein described and claimed maybe used and/or manufactured by .or for the Government of the United States of vAmericator governmental purposes without the payment of any royalties thereon or therefor.

I.claim:

1. A method of operating an oscillation generator that includes a vacuum tube comprising the steps, executed inrepeating cycles, of storing up electric energy with continuously rising voltage. while .holding said generator quiescentrsaid voltage being operatively applied to said tube, until said voltage reaches such value that oscillations begin, discharging said stored .up energy through said generator to maintain oscillations the voltage drops to such value that oscillations cease, .and radiating as asignal pulse said stored energy thus oscillating, the time of storage of said energy being many times .as long as theduration of oscillations and the output during oscillation being many times the rated capacity of said vacuum tube.

.2. .A method of operating in repeating cycles an oscillation generator that includes a vacuumovercome said bias and initiate oscillations, (11$:-

charging said stored up energy th Said gen! in the applied voltage drops to a value such that oscillations cease, and radiating: as a signal pulse said stored energy thus oscillating, the time of storage of said energy being many times as long as the duration of oscillations and the output during oscillation being many times the rated capacity of said tube.

' 3. An oscillation generator, comprising a vacuum tube having a cathode, a grid and an anode, oscillatory circuits operatively associating said grid and said anode, means to bias said grid to prevent operation of said tube until the potential on said anode reaches a predetermined minimum value, a source of potential difierence between said cathode and said anode, a high resistance in seriesbetween said source and said anode, a capacitance of a value adequate to store a quantity of energy at said minimum potential sufiicient, when radiated as a pulse, to produce a substantially powerful signal, said capacitance bein connected in parallel with said source and said resistance, whereby said capacitance is slowly charged through said resistance until said'minimum value of potential on said anode is reached and the energy stored in said capacitance then maintains output from said tube many times the rated output thereof until said stored energy is substantially reduced and means for coupling the oscillatory circuit to an antenna.

4. An oscillation generator, comprising a vacuum tube having a cathode, a grid and an anode, oscillatory circuits operatively associating said grid and said anode, means to bias said grid to prevent operation of said tube until the potential on said anode reaches a predetermined minimum va ue, a source of potential diiference between said cathode and said anode, a high resistance in seri s between said source and said anode, and a capacitance of a value adequate to store a quantity of energy at said minimum potential suilicient, when radiated as a pulse, to produce a substantiallypowerful signal, said capacitance being connected in parallel with said source and said resistance, whereby said capacitance is slowly charged through said resistance until a value of potential approaching but less than said minimum va ue is reached, means to apply additional potential to increase the total applied potential to a value at least eoual to said minimum, whereby said tube is caused to pass current and the said stored energy is discharged through said tube and maintains output from said tube many times the rated output thereof until said stored ener is substantially exhausted.

5. The method of radiating recurrent radio frequency pulses-employing a charge storage device and an oscil ation generator comprising the steps of operating the oscillation generator at a powerv level far in excess of the generator continuous service capacity and simultaneously rapidly interchanging charge between the oscillation generator and the charge storage device, radiating the generated oscillations, employing. the resulting shift in potential on the charge storage device to terminate the operation of the oscillation generator, slowly restoring the initial charge on the charge stora e device, and producing another cycle of operation. 1

6. The method of radiating recurrent radio frequency pulses employing an electron discharge device'having a plurality of elements and a charge storage device connected between a pair of said elements, comprising the steps of generating oscillations at a power level farin excess of the generator continuous service capapity and rapid- 1y shifting the charge on said storage device, radiating the oscillations, employing the resulting shift in potential on the storage device to terminate conduction in the electron discharge device, and slowly restoring the initial charge on the charge storage device to initiate another cycle of operation.

7. The method of radiating recurrent radio frequency pulses employing a vacuum tube oscillation generator having charge storage means connected between the cathode and anode thereof comprising the steps of generating oscillations while rapidly decreasing the cathode anode potential by feeding cathode anode current into the charge storage device, radiating the oscillations, employing the resulting cathode anode potential drop to cause termination of oscillations, and gradually restoring the initial charge on the charge storage device to raise the cathode anode potential to institute a succeeding cycle of operation; a

8. The method of radiating recurrent radio frequency pulses employing a vacuum tube oscillation generator comprising the steps of applying a voltage to the generator far in excess of its continuous service capacity to cause operation thereof, radiating the resulting oscillations, simultaneously feeding tube current to charge storage means to rapidly block the generator, and slowly restoring the initial charge on the charge storage means for initiation of a succeeding cycle of operation.

9. The method of radiating recurrent radio frequency pulses employing a charge storage device and an oscillation generator comprising the steps of slowly accumulating a charge in the charge storage device, rapidly discharging the charge through the oscillation generator at an input power level far in excess of its continuous service capacity, radiating the oscillations, and terminating oscillation for initiation of another cycle.

10. The method of radiating recurrent radio frequency pulses employing a charge storage device and an oscillation generator comprising the steps of slowly accumulating a charge in the charge storage device, rapidly discharging the charge through the oscillation generator at an input power level far in excess of its continuous,

service capacity, radiatin the oscillations, and employing the resulting change in potential on the charge storage device to terminate operation of the generator for initiation of another cycle.

11; The method of radiating recurrent radio frequency pulses employing storage means for electrical energy and an oscillation generator comprising the steps of slowly accumulating energy in the storage means, rapidly discharging the energy through the'oscillation generator at a rate far in excess of its continuous service capacity, radiating the oscillations, and terminating oscillations for initiation of another cycle.

12. The method of radiating recurrent radio frequency impulses employing storage means for electrical energy and an oscillation generator, comprisin .the steps of slowly accumulating energy in the storage means, rapidly discharging the energy through the oscillation generator at a rate far in excess of its continuous service capacity, radiating the oscillations, and employing the resulting change in potential on the storage means to terminate operation of the gen erator for initiation of another cycle. 1

1 13. A radio frequency pulse'transmitter com:

prising a vacuum tube having cathode, anode;

7 and control eleotrodeai circuit means intercom nectingssaid'rlectrodes toeffectoscillation, :means for coupling the circuit means to .a. mediato means 'for applying :an operating .voltage to the tube far in excess of the :izuheis continuous :service capacity, :and means responsive to oscillations of the tube :to rapidly bias an electrode thereof :to cut ofi the tube.

ilii. .A radio lirequency .pulse transmitter acornpr'isin an oscillation -gen.eraitor, and operating means therefore operative to teed power thereto at :an input :level .iar in excess of the {continuous serrice icapacity of the generator including blocking means operative responsively to the power delivered to the generator to hold the generator quiescent after .an operating period for an interval effective to restrict the average input power to it-he generators continuous service capacity.

15. .A :radio irequency pulse transmitter comprising .an oscillation generator having means controlling operation thereof,'power supply means operative to energize the generator at an input level far in :excess of the generatoris continuous service capacity, :means operative on the control means responsive to operation of the generator to terminate operation thereof after a Short periodpi operation, :and time delay control aneans operative to initiate operation of the generator after a quiescent interval many times as long as the operating period to restrict the average input power to the generators continuous service capacity.

16. A radio frequency pulse transmitter icomprising'a vacuum'tube having a plurality of electrodes, circuit means interconnecting the electrodes to efiect oscillation, means for coupling the circuit means to a radiator, power supply means operative to feed power thereto at an input level far in excess of the continuous service capacity of the tube, charge storage means connecting the power supply to the tube to energize the same for pulse generation during charge of the condenser, and resistor means connected across the charge storage means to gradually discharge the same after generation of the pulse.

17. A radio "frequency pulse transmitter comprising a vacuum tube having a plurality of electrodes, circuit means interconnecting the electrodes to effect oscillation, means for coupling the circuit means to a radiator, power supply means operative to feed power thereto at an input level far in excess of the continuous service capacity of the tube, charge storage means connected to an electrode operative to collect current received thereby and developed a potential thereon responsively to oscillation to terminate oscillation, and resistor means connected to the charge storage means to gradually restore the initial charge conditions of the charge :storage means.

'18. A radio frequency pulse transmitter comprising a vacuum tube having at least anode and cathode electrodes, circuit means connecting the electrodes to effect oscillation under the application-of voltage, a radio frequency loa-d circuit for coupling the circuit means to a radiator, power supply means furnishing an operating voltage operative to drive "the tube at a power level far exceeding its continuous service capacity, charge storage means connected between the specified electrodes and operative on discharge through the tube at power supply voltage to generate a powerful radio frequency pulse, and impedance means connecting the power supply to the charge storage means operatin in minutes the =sam'e at.

a ilimited rate to power supply potential when the tube is non-conductive and having an rim.-

pedance value sufiicient to substantially block, current new from @the power supply means to the tube during discharge of the charge storage means, whereby the pulse is generated from energy stored in the charge storage means.

1-9. A radio frequency pulse (transmitter :comprising awacuum tube having at least .anode and cathode electrodes, circuit means connecting the electrodes to effect :oscillation under :the application of voltage, a radio frequency load circuit for coupling -.the circuit:means ,to la :radiatorgpower supply means furnishing :an opera-ting volilage operative to drive the tube at :a power level FfM' exceeding its continuous service capacity, means.

connecting one terminal of the power supply rto one of the :speci'fied electrodes, charge storage means connected zhetween the other terminal of the power supply to the other :speci'fied electrode whereby :power is discharged through the rtllb into the charge storage means tocharge the same and simultaneously generate a powerful output P11186511} the load circuit, said :pulsebeing-termimated with charging of the charge storage means,- and conductive impedance means connected across-the charge storage means'becoming operative after termination of pulse generation to discharge the charge storage means vpreliminaryito the generation of the succeeding pulse.

'20. ,A radio frequency pulse transmitter comprising .a vacuum tube having at least anode and cathode electrodes, circuit means connecting the electrodes to efiect oscillation *under the application of voltage, ara'dio frequency-load-circuit for coupling the circuit :means to a radiator, power supply means furnishing an operating voltage operative to drive the tube at a power level ,tar exceeding its continuous :servi-ce capacity, means connecting one terminal of :the power :supl ly i one of the specified electrodes, impedance means connecting the other terminal of the power supply to the other specified tube electrode, charge storage means connected "to said other tube elec-- trode and to one terminal of the power :supply,

whereby charge is interchanged between the tube and the charge storage means during oscillation to shift the said other electrode potential and terminate oscillation after a pulse generating period and the potential change on -the charge storage means .is slowly restored through the impedance means to restore operating potential .for reinitiating oscillation.

ROBERT :M. PAGE.

REFERENCES :CI'IEEJ) The following references are of record in the file of this patent:

,GreatBritain "g. Feb. 2123, .1935

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