US2490007A - Frequency controllable magnetron system - Google Patents

Frequency controllable magnetron system Download PDF

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Publication number
US2490007A
US2490007A US734920A US73492047A US2490007A US 2490007 A US2490007 A US 2490007A US 734920 A US734920 A US 734920A US 73492047 A US73492047 A US 73492047A US 2490007 A US2490007 A US 2490007A
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United States
Prior art keywords
frequency
oscillator
magnetron
circuit
modulation
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Expired - Lifetime
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US734920A
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English (en)
Inventor
Jr Philip H Peters
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General Electric Co
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General Electric Co
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Publication date
Priority to FR964843D priority Critical patent/FR964843A/fr
Priority to BE483142D priority patent/BE483142A/xx
Priority to NL138684D priority patent/NL138684B/xx
Application filed by General Electric Co filed Critical General Electric Co
Priority to US734920A priority patent/US2490007A/en
Application granted granted Critical
Publication of US2490007A publication Critical patent/US2490007A/en
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C3/00—Angle modulation
    • H03C3/02—Details
    • H03C3/09—Modifications of modulator for regulating the mean frequency
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B9/00—Generation of oscillations using transit-time effects
    • H03B9/01—Generation of oscillations using transit-time effects using discharge tubes
    • H03B9/10—Generation of oscillations using transit-time effects using discharge tubes using a magnetron
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C3/00—Angle modulation
    • H03C3/30—Angle modulation by means of transit-time tube
    • H03C3/32—Angle modulation by means of transit-time tube the tube being a magnetron
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C7/00—Modulating electromagnetic waves
    • H03C7/02—Modulating electromagnetic waves in transmission lines, waveguides, cavity resonators or radiation fields of antennas

Definitions

  • This invention relates to high frequency systems and more particularly to a novel method and apparatus, especially useful with magnetron type oscillators for the generation of frequency modulated oscillations or for the generation of electromagnetic oscillations of stabilized frequency.
  • the communications and related arts it is customary to transmit intelligence by modulating a high frequency electromagnetic carrier wave capable of being pro- Jected into space with a decipherable signal component which is an accurate and faithful representation of the intelligence to be transmitted.
  • modulation may be accomplished by causing any one of the parameters of the electromagnetic wave (1. e., amplitude, frequency or phase) to vary in continuous correspondence with the desired intelligence while the others are held constant, the resultant variations constituting the mentioned signal component. If, for any of numerous possible reasons, distorting factors are introduced by the apparatus employed, the modulated wave will be correspondingly distorted with the result that the desired high fidelity may not be obtained and consequently the intelligibility of the transmission may be impaired. If the intelligence is speech, music or television signals the degree of impairment may be such as to render the transmission completely useless in'practice.
  • the magnetron type of discharge device is presently the only available type capable of generating at both satisfactorily high power output levels and ultra high frequencies.
  • its usefulness as a source of oscillations in such apparatus as the foregoing has heretofore been limited by certain inherent magnetron characteristics which render it difficult to produce therein distortion free modulation.
  • the reason therefor may be attributed largely to an inherent frequency instability characteristic of most ma netrons. As is known, such instability may manifest itself as sudden random changes of the oscillation frequency throughout a frequency spectrum much wider (e. g. 500 kilocycles) and more discontinuous than that experienced with other types of oscillators.
  • desirable frequency changes attributable to the frequency modulation are unaffected by the corrective action of the first circuit while the undesirable frequency changes attributable to random frequency fluctuations of the magnetron oscillator itself are so affected and their effect thereby eliminated.
  • the aforementioned first circuit may advantageously employ a novel magnetron tube structure (such as that described and broadly claimed in copending application Ser. No. 719,704, filed January 2, 194 7, by Philip H. Peters, Jr., and John P. Blewett and assigned to the same assignee as the present invention) in which two or more magnetron electrode configurations are coupled together in such fashion that one behaves as a conventional oscillator generating high frequency electromagnetic waves while the other behaves as a controllable variable electronic impedance reacting with the oscillator to produce controllable changes in oscillation frequency.
  • a novel magnetron tube structure such as that described and broadly claimed in copending application Ser. No. 719,704, filed January 2, 194 7, by Philip H. Peters, Jr., and John P. Blewett and assigned to the same assignee as the present invention
  • the oscillator includes a plurality of anodes or electrodes 2, 3 and 4 arranged to excite and sustain oscillations in a resonant circuit such as the parallel wire transmission line 5 comprising parallel wires 6 and and which is preferably tunable by suitable means such as the short circuiting conductor 8 adjustablypositionable lon gitudinally of the transmission line by the rod 9.
  • the electrodes 2, 3 and 4 have opposed curved surfaces defining generally cylindrical electron discharge chamber Ill in which a rotating electron space charge of the magnetron type may be developed concentrically with the cathode II.
  • the latter electrodes together with the associated cathode H may be viewed as providing an oscillator section, that is, the section which establishes and sustains oscillations in the resonant circuit comprising transmission line 5.
  • an oscillator section that is, the section which establishes and sustains oscillations in the resonant circuit comprising transmission line 5.
  • a variable reactance section formed about a second generally cylindrical discharge chamber l2 in which a rotating electron space charge of the magnetron type may be arranged to rotate about the second cathode l3.
  • chamber l2 is formed by opposed semlcylindrlcal surfaces of electrodes 2 and 3.
  • the electrode 4 of the oscillator section may be connected directly to the midpoint of the U-shaped portion l4 terminating the one end ofv the transmission line 5.
  • suitable energizing potentials such as those supplied by the direct current sources comprising batteries l5 and I8, are applied between the respective cathodes and anodes oscillations may be generated and sustained in the oscillator, and the frequency thereof may be controlled by controlling voltage between cathode l3 and electrodes 2 and 3 of the reactance section.
  • any suitable load connection to the transmission line 5 may be provided, for example the means indicated schematically as the resistor I! which may be an antenna coupling cable connected across the line at a suitable point.
  • a feed back loop circuit comprising any suitable energy pickup device such as a coaxial line having inner conductor l8 and outer conductor IS, a mixer 20, the limiter-discriminator 2
  • the function of the mixer 20 is to combine a voltage component of frequency component f0 derived inductively from the oscillator I through the coaxial line l8l9 with a voltage component of standard frequency f1 derived from the local oscillator 25 hereinafter to be described.
  • the output of the limiter-discriminator 2i may next be applied to the direct current amplifier 22, if amplification is desirable or necessary and, in turn, the amplified voltage may be applied to the anode-cathode circuit of the reactance section of the magnetron oscillator in such manner as to control the frequency thereof in accordance with the value of delta 1'.
  • the correction voltage derived from the limiter-discriminator and amplifier is connected in series with the principal energizing voltage of the battery l5.
  • the circuit may be adjusted to be balanced at a desired mean frequency of the oscillator by appropriate choice of the circuit parameters.
  • the frequency ⁇ 1 of local oscillator 25 will be so chosen with respect to the desired mean frequency In of oscillator I as to provide a conveniently handled predetermined intermediate frequency delta 1' (for example, delta I equal to 30 megacycles) when the oscillator I is oscillating at the desired mean frequency, and the limiter-discriminator will be so designed that it develops zero output voltage at delta f equal to the predetermined intermediate frequency (30 megacycles).
  • Undesired frequency deviations, random or otherwise, of oscillator I will then vary delta 1 in such manner as to cause the limiter-discriminator to develop a unidirectional output voltage proportional to the deviation and of polarity determined by the direction of the I deviation.
  • the frequency 11 of the local oscillator 25 Assuming the frequency 11 of the local oscillator 25 to be constant, then it will be apparent that any changes in the frequency Io of the magnetron oscillator I which result in a delta f different from the balanced value will give rise to a discriminator output voltage which may be applied to the reactance section between the cathode l3 and the anodes 2 and 3 in such manner as to change the reactance thereof and thereby introduce a reactive component tending to correct or compensate for the frequency fluctuations which caused the unbalance.
  • the oscillator is returned to its desired mean frequency by the change in reactance.
  • Y in principle, so much of the system thus far described is functionally analogous to similar techniques already known in the art of frequency modulated transmitters wherein such techniques are employed for center frequency stabilization i. e. stabilization against undesirable tendencies of the mean oscillator frequency to deviate or drift slightly at relatively low time rates. It differs however, in one important respect, namely in that the circuit in the present case must be designed to accommodate the relatively much larger undesirable frequency changes and relatively much higher time rates of such changes characteristic of the magnetron, both of which represent distortion components having frequencies within the same frequency range as that of -the desired frequency changes due to the modulation signal of the intelligence 1. e. the frequency changes due to random fluctuation are within.
  • the frequency corrective action of the system thus far described can not be made selective as between desired and undesired frequency changes.
  • the undesirable frequency changes represent distortion components having frequencies outside the range of the desired frequency changes due to the modulation signal i. e. the frequency changes due to random fluctua- -.tion or drift are below the audio or video spec- .trum useful for modulation purposes.
  • the frequency corrective action of the prior art techniques can be made selective as between desired and undesired frequency changes.
  • An example of the latter selective action will incidentally be illustrated hereinafter in connection with the circuit for modulating the frequency of local oscillator 28.
  • the modulation function may in accordance with the essence of this invention, be performed outside of the circuit thus far described, for example, by the circuit designated generally as 23 in the case of frequency modulation and by the modulator 24 in the case of amplitude modulation.
  • the circuit 23 includes a local oscillator 25 against which the frequency of the magnetron oscillator i is to be compared by the mixer-limiter-discriminator circuit already described, and suitable control elements for controlling and modulating the frequency of. oscillator 25.
  • the entire circuit 23 may be either a conventional frequency modulation circuit or a conventional constant frequency oscillator of the types well known in the art depending on whether it is desired to frequency or amplitude modulate the magnetron oscillator.
  • the circuit 23 may include a reference oscillator 26, a mixer 21, a local limiter discriminator 28, a time delay circuit 29 and a local oscillator frequency modulator 3i) driven by any source of intelligence signals such as microphone 3. All of these including the local oscillator 25 itself may be of the forms well known in the art.
  • oscillator 26 may be a crystal controlled oscillator of highly constant frequency.
  • Mixer 2! may be similar to mixer 20 and will serve to derive a differential frequency constituting the difference between the center frequency of oscillators 25 and 26.
  • Limiter-discriminator 28 will function to derive from the mixer 21 a unidirectionalvoltage which is solely a measure of the latter differential frequency and which may be used to stabilize the center frequency of oscillator 25.
  • Local oscillator modulator 30 may include a reactance tube circuit which controls the frequency of oscillator 25 in response to the unidirectional voltage output of discriminator 28 and also in response to frequency modulation signals from microphone 3
  • the time delay circuit 29 may be designed in numerous ways so that it functions to attenuate rapid frequency changes while leaving slow frequency changes unaffected. Thereby the small and slow frequency changes below the lowest modulation frequency (e. g. 40 cycles) and due to undesirable drift away from the center frequency are corrected by the mixerlimiter-discriminator 21-28 while those due to desired frequency modulation signals are not so corrected and the circuit becomes selective in the manner heretofore indicated.
  • the mixerlimiter-discriminator -2I will tend always to stabilize the frequency of the magnetron oscillator I at a fixed frequency from that of local oscillator 25, i. e. at a frequency differing from that of oscillator 25 by the intermediate frequency output of mixer 20 (e. g. megacycles) Therefore, if oscillator 25 be frequency modulated, the magnetron oscillator I will likewise be modulated. But because the frequency stabilization feedback circuit 20-2 I-22 for the magnetron has no eitect on the frequency modulation signal, it can be designed to give the necessary wide band control of the magnetron center frequency without interfering with the intelligence.
  • the circuit thus described is useful not only for frequency modulation transmission but also for amplitude modulation. If it be desired to employ the system for amplitude modulation it will suffice that the local oscillator 25 be maintained at a fixed frequency rather than frequency modulated, that is to say it is employed simply as a reference oscillator of highly constant frequency; In that case, the center frequency of the magnetron oscillator I will be caused to be stabilized near the frequency of the local oscillator in the manner discussed. Amplitude modulation may then be eifected by varying the amplitude of the output of the magnetron oscillator l by suitable manipulation of the electrode potentials.
  • a possible means for effecting amplitude modulation as comprising a signal source such as modulator 24 which varies the voltage on the electrodes of the oscillator section comprising the electrodes 2, 3 and 4 and the cathode II in accordance with the desired signal, the modulator 24 being inserted in series with the battery It in the manner 1 indicated.
  • a signal source such as modulator 24 which varies the voltage on the electrodes of the oscillator section comprising the electrodes 2, 3 and 4 and the cathode II in accordance with the desired signal, the modulator 24 being inserted in series with the battery It in the manner 1 indicated.
  • any source of intelligence such as a microphone 32 may be connected to the modulator 24 for the purpose.
  • the feedback circuit will also serve to correct or compensate for frequency changes ordinarily caused by changes in the electrode voltage necessary to the amplitude modulation.
  • attempts to amplitude modulate magnetrons by varying the electrode voltages in this manner have been unsatisfactory for the reason that suchvoltage variations also introduced a certain amount of frequency modul
  • said oscillator comprises a magnetron type discharge device having a resonant circuit and spaced electrodes for sustaining said electromagnetic oscillations therein and said first mentioned means comprises electrode means operatively connected to said spaced electrodes and constituting a variable electronic impedance effective to adjust the resonant frequency of said resonant circuit.
  • a system for generating electromagnetic oscillations and modulating the frequency thereof comprising an oscillator including means effective to adjust the frequency thereof, a source of reference oscillations of precisely controllable frequency, means for maintaining the frequency of said oscillator at a fixed relation with respect to the frequency of said source comprising means for deriving an electrical voltage of differential frequency equal to the difference between the frequency of said oscillator and the frequency of said source, means for deriving a unidirectional voltage proportional to said diflerential frequency and means for applying said unidirectional voltage to said first mentioned means to effect an adjustment of the frequency of said oscillator to maintain said fixed relation, and means for modulating the frequency of said source whereby the frequency of said oscillator is likewise modulated.
  • said oscillator comprises a magnetron type discharge device having a resonant circuit and spaced electrodes for sustaining said electromagnetic oscillations therein and said first mentioned means comprises electrode means operatively connected to said spaced electrodes and constituting a variable electronic impedance effective to adjust the resonant frequency of said resonant circuit.
  • a system for generating electromagnetic oscillations and modulating the frequency thereof in accordance with a predetermined signal comprising an oscillator including means effective to adjust the frequency thereof, a source of reference oscillations of precisely controllable fre quency, means for maintaining the frequency of said oscillator at a fixed relation with respect to the frequency of said source comprising means for deriving an electrical voltage of differential frequency equal to the difference between the frequency of said oscillator and the frequency of said source, means for deriving a unidirectional voltage proportional to said differential frequency and means for applying said unidirectional voltage to said first mentioned means to effect an adjustment of the frequency of said oscillator to maintain said fixed relation, and means for modu- REFERENCES orrEn
  • the following references are of record in thefile of this patent:'

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  • Electromagnetism (AREA)
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US734920A 1947-03-15 1947-03-15 Frequency controllable magnetron system Expired - Lifetime US2490007A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
FR964843D FR964843A (hu) 1947-03-15
BE483142D BE483142A (hu) 1947-03-15
NL138684D NL138684B (hu) 1947-03-15
US734920A US2490007A (en) 1947-03-15 1947-03-15 Frequency controllable magnetron system

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2602156A (en) * 1947-06-28 1952-07-01 Rca Corp Modulated microwave generator
US2620468A (en) * 1949-04-14 1952-12-02 Radio Electr Soc Fr Arrangement for converting frequency-modulated waves
US2620467A (en) * 1950-01-25 1952-12-02 Rca Corp Amplitude modulation of magnetrons
US2644138A (en) * 1949-12-09 1953-06-30 Rca Corp Frequency control system
US2747031A (en) * 1950-05-10 1956-05-22 Gen Electric Magnetron amplifier
US2799828A (en) * 1950-08-11 1957-07-16 Gen Electric Magnetron and systems therefor
US2944112A (en) * 1954-03-15 1960-07-05 Telephony
US2971168A (en) * 1954-12-28 1961-02-07 Rca Corp Modulation system
US3514718A (en) * 1967-08-30 1970-05-26 Cornell Aeronautical Labor Inc Apparatus for linearizing the output frequency variation rate of voltage tunable oscillators or the like

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1040622B (de) * 1954-04-09 1958-10-09 Gen Electric Co Ltd Elektrischer Schwingungsgenerator

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2113225A (en) * 1936-07-25 1938-04-05 Rca Corp Frequency controlled electronic oscillator
US2241976A (en) * 1940-04-25 1941-05-13 Gen Electric High frequency apparatus
US2296962A (en) * 1939-12-22 1942-09-29 Rca Corp Frequency modulation
US2337214A (en) * 1941-04-17 1943-12-21 Rca Corp Ultra short wave apparatus
US2406125A (en) * 1943-12-17 1946-08-20 Hartford Nat Bank & Trust Co Frequency stabilizing system

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2113225A (en) * 1936-07-25 1938-04-05 Rca Corp Frequency controlled electronic oscillator
US2296962A (en) * 1939-12-22 1942-09-29 Rca Corp Frequency modulation
US2241976A (en) * 1940-04-25 1941-05-13 Gen Electric High frequency apparatus
US2337214A (en) * 1941-04-17 1943-12-21 Rca Corp Ultra short wave apparatus
US2406125A (en) * 1943-12-17 1946-08-20 Hartford Nat Bank & Trust Co Frequency stabilizing system

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2602156A (en) * 1947-06-28 1952-07-01 Rca Corp Modulated microwave generator
US2620468A (en) * 1949-04-14 1952-12-02 Radio Electr Soc Fr Arrangement for converting frequency-modulated waves
US2644138A (en) * 1949-12-09 1953-06-30 Rca Corp Frequency control system
US2620467A (en) * 1950-01-25 1952-12-02 Rca Corp Amplitude modulation of magnetrons
US2747031A (en) * 1950-05-10 1956-05-22 Gen Electric Magnetron amplifier
US2799828A (en) * 1950-08-11 1957-07-16 Gen Electric Magnetron and systems therefor
US2944112A (en) * 1954-03-15 1960-07-05 Telephony
US2971168A (en) * 1954-12-28 1961-02-07 Rca Corp Modulation system
US3514718A (en) * 1967-08-30 1970-05-26 Cornell Aeronautical Labor Inc Apparatus for linearizing the output frequency variation rate of voltage tunable oscillators or the like

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Publication number Publication date
FR964843A (hu) 1950-08-25
BE483142A (hu)
NL138684B (hu)

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