US3904917A - High-efficiency broadband klystron amplifier of reduced length - Google Patents

High-efficiency broadband klystron amplifier of reduced length Download PDF

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Publication number
US3904917A
US3904917A US469758A US46975874A US3904917A US 3904917 A US3904917 A US 3904917A US 469758 A US469758 A US 469758A US 46975874 A US46975874 A US 46975874A US 3904917 A US3904917 A US 3904917A
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United States
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cavity
klystron
gap
electron beam
drift tube
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US469758A
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English (en)
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Isao Ueda
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NEC Corp
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Nippon Electric Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J25/00—Transit-time tubes, e.g. klystrons, travelling-wave tubes, magnetrons
    • H01J25/02—Tubes with electron stream modulated in velocity or density in a modulator zone and thereafter giving up energy in an inducing zone, the zones being associated with one or more resonators
    • H01J25/10—Klystrons, i.e. tubes having two or more resonators, without reflection of the electron stream, and in which the stream is modulated mainly by velocity in the zone of the input resonator

Definitions

  • KLYSTRON AMPLIFIER OF REDUCED Attorney, Agent, or FirmOstrolenk, Faber, Gerb & LENGTH Soffen [75] Inventor: Isao Ueda, Tokyo, Japan [57] ABSTRACT [73] Asslgnee: Nlppon Electric Company Llmlted A multi-cavity klystron is provided which utilizes a Tokyo, Japan front stage wide band exclting cavlty group consisting [22] Filed: May 14, 1974 of one or more cavities and including at least one cavity coupled to an external reactance circuit. Means are [2]] Appl' 469758 provided for applying a voltage to accelerate the electron beam at least across the last drift tube interaction [52] US. Cl.
  • a rear 315/552 stage bunching cavity group comprised of one or more [51] Int. Cl. H01J 25/10 cavities is tuned to a frequency of few percent greater [58] Field of Search 315/534, 5.35, 5.39, 5.43, than the center frequency operating band and an out- 315/5.44, 5.46, 5.51, 5.52 put cavity is provided to ultimately receive and pass the electron beam, said output cavity being tuned sub- [56] References Cited stantially to the center frequency of the operating UNITED STATES PATENTS band. By selecting a perviance measured across the 2,610,306 9/1952 Touraton et a1.
  • klystrons for use in amplification of television video signals have been required to have a broad bandwidth for amplification of the order of 68 MHz at 1 dB points in the frequency band for UHF television broadcasting (for instance, 470 MHz-89O MHz), and since this bandwidth exceeds 1% of a reference frequency, in such type of klystrons normally resonant frequencies of four to five cavities were staggered, and simultaneously therewith a perviance was selected at 1.5 to 3 X 10' pervs so that Q, of the re spective cavities upon operation, when a beam current is passed therethrough, may be lowered to a minimum by the loading of the electron beam.
  • the wavelength is longer than that in the GHz band, so that the construction in the cavity section of the klystron which is correlated to the wavelength is fairly large in size. Accordingly, a large perviance was also required for the purpose of avoiding an excessive tube length. On the other hand, however, a large perviance was accompanied with a shortcoming that an efficiency of conversion from an electron beam to a microwave circuit at the output cavity gap was lowered.
  • FIG. 1 is a schematic structural view showing one preferred embodiment of the present invention.
  • FIG. 2 is a schematic partial structural view showing another preferred embodiment of the present invention. 1
  • reference numeral 2 designates a cathode
  • numeral 3 designates an accelerating electrode
  • numeral l designates a choke structure for insulating an input drift tube from a first cavity with respect to a DC.
  • numeral 7 designates an external reactance circuit
  • numeral 9 designates an input cavity in a front stage wide band exciting cavity group
  • numeral 13 designates a second cavity in the same front stage cavity group
  • numeral 17 designates a third cavity in a rear stage bunching cavity group
  • numeral 20 designates an output cavity
  • numeral 11 designates a drift tube interaction gap in the first cavity
  • numeral 14' designates a choke structure for insulating a first drift tube from the second cavity with respect to a DC.
  • numeral l5 designates a drift tube interaction gap in the second cavity
  • symbol E designates an accelerating voltage source for applying a voltage across the first cavity drift tube interaction gap
  • symbol E designates an accelerating voltage source for applying a voltage across the second cavity drift tube interaction gap.
  • a perviance with respect to a cathode 2 and an accelerating electrode 3 is selected to lie in the range from 1.5 to 3 X 10 perv. and preferably to be a value of 2 X 10 perv.
  • An input drift tube 4 whose downstream end forms a first interaction gap 11 jointly with the adjacent end of a first drift tube 12, is provided with a choke structure portion 10 which insulates the drift tube 4 from an input cavity 9 with respect to a DC.
  • the choke structure portion 10 a known choke structure in a microwave circuit is available, in which an insulator such as, for example, ceramics is interposed between the metallic members to hold them firmly and mechanically relative to one another, and which is as long as one fourth wavelength at the operating frequency of said klystron, and therefore it will not be described here in more detail.
  • an insulator such as, for example, ceramics
  • An exciting signal applied from an external signal generator 5 is transmitted to the input cavity 9 having a loop 8, through a capacitor or an electro-static coupler 6 for intercepting a DC. component and a broad exciting circuit 7, to give a broad band velocity modulation to an electron beam 26 in the first drift tube interaction gap 11.
  • the first drift tube 12 which defines the upper boundary of the first interaction gap 11, is insulated from a second cavity 13 with respect to a DC. component but short-circuited thereto with respect to a microwave frequency at a choke structure portion 14 as is the case with the input drift tube 4, although it is directly connected to the input cavity9, and thereby as a whole said drift tube 12 is constructed to serve as a part of both the cavity resonators 9 and 13.
  • the second cavity 13 is directly connected, in a conventional manner, to a second drift tube 16, a third cavity 17, a third drift tube 19, an output cavity 20 and an output drift tube 24, to form the remaining part of the klystron tube.
  • the output cavity 20 is coupled to load 22 such as an antenna via, for instance, a loop 21.
  • This output cavity 20 and the like are grounded similarly to the conventional structures.
  • a collector 25 is normally grounded through an ammeter or the like, but it may be applied with a potential lower than the earth potential by means of a voltage source E in order to improve operating efl'iciency.
  • the accelerating electrode voltage is 6.85 KV with respect to the cathode 2, and said voltage is applied by means ofa voltage source E
  • the input drift tube 4 is either shortcircuited to the accelerating electrode 3 upon manufacture or separately formed for the purpose of current measurement, but even in the latter case they are externally short-circuited so as to be at the same potential.
  • the difference voltage of 5.65 k ⁇ / between the voltage of 12.5 kV and the voltage of 6.85 kV is divided into two voltages represented by voltage sources E and E, which are connected as shown in FIG. 1.
  • the electron beam is additionally accelerated by the voltage E across the first interaction gap 11, and further it is still additionally accelerated by the voltage E, across the second interaction gap 15.
  • the voltage of the voltage source E is selected to lie in the range from 0.5 to 3 KV and preferably at 1 kV in order to mitigate the requirement for withstand voltage at the choke portion 10 singly, to improve the focusing of the electron beam by progressively accelerating the same towards the collector as will be described later, and also to prevent feedback caused by backwardly travelling electrons.
  • the equivalent perviance of the electron beam is varied from 2 X l" perv. to 1.62 X perv. across the first interaction gap, and if the voltage E across the second interaction gap is selected at 4.65 KV, then the equivalent perviance is varied from 1.62 X 10 perv. to 0.8 X 10 perv. across the second interaction gap.
  • a coupling coefficient between an electron beam and a cavity circuit across a drift tube interaction gap can be calculated by normalizing the structural dimensions with reference to a DC. velocity of the beam and an operating frequency.
  • a density modulation developing within an electron beam travelling through a drift tube is determined by means of a reduced plasma wavelength Aq, which is obtained by multiplying a plasma Wavelength that is in turn determined from beam voltage and current and a beam radius, by a configuration reduction factor that is determined from a drift tube diameter, a beam diameter, an operating frequency, etc.
  • the beam loading across the first interaction gap is about 2.5 times as high as the beam loading across the third and fourth interaction gaps, which implies that the electron beam loading can be made larger than the case where the initial equivalent perviance of the electron beam is selected at 0.8 X 10' perv., and that the Q-value of the input cavity can be lowered accordingly. 7
  • the second drift tube length is selected at L 0.1 M12 17 cm and the third drift tube length is selected at L 0.09 M13 13 cm.
  • the perviance of the electron beam in the third drift tube region is 2 X 10 perv.
  • the drift tube length takes an extremely short value of L 0.09 At 6.3 cm, resulting in disadvantages-that there remains no space between the adjacent cavities for accommodating a cooling structure (i.e., radiating pins 26 FIG. 1) and that the drift tube interaction gap must be positioned very close to the cavity wall and thereby the impedance is necessarily lowered.
  • a wide band excitation is applied to the electron beam under the state having a large perviance, that is, having a low Q, value to assure a sufficient gain in a mechanically short distance, while in the second and subsequent cavities which largely affect the efficieney, by reducing the equivalent perviance the velocity dispersion of the electron beam is suppressed, the restriction'for the distance between the adjacent cavities is mitigated and the efficieney is fully enhanced. Since the resonant points of the second and third cavities are shifted to a higher frequency outside of the operating frequency band in order to enhance operating efficieney, these cavities would not degrade the wide band characteristics at the preceding stage.
  • the distance from the first interaction gap to the fourth interaction gap takes a value of 0.2 M11 0.115 M12 0.09 M13 47 mm in contrast to the corresponding distance in the prior art of 0.405 M13 59 cm, so that a high gain may be easily assured with a tube body that is shorter than the prior art tubes by more than 10 cm, and yet a wide band characteristic and an efficieney of 60% or higher can be assured similarly to the prior art tubes.
  • the electron beam is focused by an electrostatic lens effect, and so the magnetic focusing becomes easier.
  • the backwardly travelling electrons which have been accelerated by the inverse voltage E and thus travel backwardly, from the collector region, feed back energy to the input cavity while repeating interaction with the microwave circuit in the drift tube interaction gap in an opposite sequence to the principal beam, resulting in various unstable phenomena.
  • the voltage at the accelerating electrode that is opposed to the cathode, which hasa high operating temperature is of a low voltage value'because the perviance is selected at a relatively high value, and accordingly, there is an advantage that the occurrence of sparking accidents are extremely reduced.
  • the choke portion IOof the input cavity 9 and the choke portion 14 of the second cavity 13 must have withstand voltages of, for instance, 1 kV or higher and 4.65 kV or higher, respectively.
  • a multi-cavity klystron involves only a few problems relating to safety due to the presence of high voltage because it is generally used as enclosed in a magnetic focusing device, it is desirable to connect the first and second cavities to a structure having a potential that is close to the earth potential as shown in FIG.
  • the structure of insulating with respect to a DC. but short-circuiting with respect to microwave frequencies can be relatively easily practices because the associated cavities are cavities supporting a low power level of microwave energy.
  • drift tube portions are formed into a choke structure in the embodiment illustrated in FIG. 1, the invention is not limited thereto, but various alternative modes of the preferred embodiment can be adapted such that the choke structure may be formed in the upper and lower cavity wall portions.
  • connection of the voltage source circuit in FIG. 1 is illustrative, and the invention is not limited thereto. Since the accelerating electrode current and the drift tube currents are small relative to the principal beam current, the voltage source connection can be made in such manner that a bleeder resistance is connected across a single voltage source of a voltage equal to E E E and the necessary potentials are applied from the tap points of said bleeder resistance to the drift tubes and the like. I
  • the lowering of the collector potential by means of the voltage source E has been illustrated to show the associated feature of the klystron according to the present invention, and any known techniques for lowering the collector potential may be practiced without deteriorating the effect and advantage of the present invention.
  • the present invention could be embodied not only in an internal cavity type but also in an external cavity type.
  • FIG. 2 shows another embodiment of the present invention, in which the perviance is set at a relatively high value, whereby a low voltage E is applied to an input drift tube 30 formed integrally with an accelerating electrode and is further applied to a first drift tube 38 via a lead wire 40 insulated by an insulator 39, said drift tubes 30 and 38 being insulated with respect to a DC. component from cavities 31 and 43, respectively, of an internal cavity type of klystron but short-circuited to parts 34 and 41, respectively, through a choke portion with respect to microwave frequencies.
  • a signal is applied to the input cavity 31 from a signal generator 37 via an auxiliary cavity 36 and an input loop 35, and thereby a wide-band velocity modulation is imposed upon the electron beam 26 across the first interaction gap 33 under a state of heavy beam loading.
  • the second cavity 43 is further coupled to a matched load 47 via a loop 45 through a wide-band circuit 46 so that the impedance as viewed from the second interaction gap may have a wide-band and low-Q characteristic Accordingly, a wide-band velocity modulation is imposed upon the electron beam also across the second interaction gap. and simultaneously therewith an acceleration corresponding to a DC. voltage E is achieved there-across.
  • the electron beam becomes a beam having a low perviance so that bunching having a high conversion efficiency may be achieved.
  • variable frequency O means 32 and 44 the exciting input circuits 36 and 37, and the second cavity loading circuits 46 and 47 from the cavity walls, and so this construction is safe and easy to practice.
  • the values of the perviance at the electron gun section. the equivalent perviance of the electron beam in the front stage cavity section where a wideband velocity modulation is achieved with a low level of signal, and the equivalent perviance of the same in the rear stage cavity section where highly efficient bunching with a high level of signal and extraction of an output power. are merely illustrative, and the scope of the present invention should not be limited thereto.
  • a multi-cavity klystron having spaced apart electron beam generating means and beam collection means. said klystron having apparatus positioned between said beam generating and collection means comprising:
  • a front stage wide band exciting cavity group comprising a plurality of axially aligned spaced apart drift tubes for passing the electron beam therethrough and a plurality of cavities, each of said cavities spanning selected pairs of said axially aligned drift tubes;
  • At least one of said cavities having an external reactance circuit coupled thereto for enhancing wide band response of the klystron;
  • a rear stage bunching cavity group comprising at least one cavity spanning a selected pair of said drift tubes and being tuned to a frequency one to a few percent higher than the center frequency of the operating band;
  • choke means positioned between that one of the drift tubes forming the aforementioned interaction gap for accelerating the electron beam which is positioned closest to said beam generating means and the cavity associated therewith for isolating the drift tube closest to the beam generating means from said associated cavity to decouple D.C. components from the aforesaid drift tube.
  • a multi-cavity klystron comprising a cathode for developing an electron beam
  • an external reactance circuit coupled to said first cavity for broadening the operating bandwidth
  • second and third spaced drift tubes being axially arranged to receive and pass said electron beam therethrough;
  • said second and third drift tubes being spaced from said first drift tube and from each other to form second and third interaction gaps:
  • a fourth drift tube being axially arranged to pass said electron beam therethrough and to form with said third drift tube a fourth interaction gap
  • the klystron of claim 2 further comprising a cooling structure
  • the perviance of said third gap being reduced by an amount sufficient to increase the distance between said third and output cavities to facilitate the placement of said cooling structure therebetween.
  • the klystron of claim 2 further comprising a collector axially arranged to intercept the electron beam as it passes beyond the fourth drift tube;
  • the klystron of claim 2 further comprising means for coupling a DC. accelerating voltage across said first gap.
  • the klystron of claim 8 further comprising means for coupling a DC. accelerating voltage across said second gap.
  • the klystron of claim 9 further comprising a collector axially arranged to intercept the electron beam as it passes beyond the fourth drift tube:
  • the klystron of claim 2 further comprising a matched load coupled to said second cavity so that the impedance as viewed from the second gap is wide-band and has a low-Q characteristic.

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US469758A 1973-05-24 1974-05-14 High-efficiency broadband klystron amplifier of reduced length Expired - Lifetime US3904917A (en)

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JP48058446A JPS5010552A (nl) 1973-05-24 1973-05-24

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JP (1) JPS5010552A (nl)
DE (1) DE2424679A1 (nl)
FR (1) FR2231098B1 (nl)
GB (1) GB1425678A (nl)
NL (1) NL7406947A (nl)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3974417A (en) * 1974-12-06 1976-08-10 Nippon Electric Company, Ltd. Four-cavity velocity modulation tube
US4168451A (en) * 1977-07-01 1979-09-18 Nippon Electric Co., Ltd. Multi-cavity klystron amplifiers
US4567452A (en) * 1984-03-20 1986-01-28 The United States Of America As Represented By The United States Department Of Energy Broad-band beam buncher
WO2000030145A1 (en) * 1998-11-16 2000-05-25 Litton Systems, Inc. Low-power wide-bandwidth klystron
WO2011050193A1 (en) * 2009-10-21 2011-04-28 Omega-P, Inc. Low-voltage, multi-beam klystron
US8559894B2 (en) * 2011-09-01 2013-10-15 Baron Services, Inc. Klystron transmitter
CN107240539A (zh) * 2017-06-15 2017-10-10 湖北汉光科技股份有限公司 一种65mw大功率速调管
CN110753988A (zh) * 2017-06-13 2020-02-04 佳能电子管器件株式会社 速调管

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6056486A (ja) * 1983-09-09 1985-04-02 Hitachi Seiko Ltd 消耗性電極を用いたア−ク溶接方法

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2610306A (en) * 1947-06-14 1952-09-09 Int Standard Electric Corp Velocity modulation tube
US2702349A (en) * 1951-02-15 1955-02-15 Gen Electric High-frequency electric discharge device and circuits associated therewith
US2934672A (en) * 1957-06-12 1960-04-26 Itt Velocity modulation electron discharge device
US3456207A (en) * 1966-10-10 1969-07-15 Varian Associates Integral cavity multicavity linear beam amplifier having means for applying a d.c. voltage across the interaction gaps
US3725721A (en) * 1971-05-17 1973-04-03 Varian Associates Apparatus for loading cavity resonators of tunable velocity modulation tubes
US3775635A (en) * 1971-09-16 1973-11-27 Thomson Csf Power amplifier klystrons operating in wide frequency bands
US3811065A (en) * 1968-10-15 1974-05-14 Varian Associates Velocity modulation microwave tube employing a harmonic prebuncher for improved efficiency

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2610306A (en) * 1947-06-14 1952-09-09 Int Standard Electric Corp Velocity modulation tube
US2702349A (en) * 1951-02-15 1955-02-15 Gen Electric High-frequency electric discharge device and circuits associated therewith
US2934672A (en) * 1957-06-12 1960-04-26 Itt Velocity modulation electron discharge device
US2960658A (en) * 1957-06-12 1960-11-15 English Electric Valve Co Ltd Microwave amplifiers
US3456207A (en) * 1966-10-10 1969-07-15 Varian Associates Integral cavity multicavity linear beam amplifier having means for applying a d.c. voltage across the interaction gaps
US3811065A (en) * 1968-10-15 1974-05-14 Varian Associates Velocity modulation microwave tube employing a harmonic prebuncher for improved efficiency
US3725721A (en) * 1971-05-17 1973-04-03 Varian Associates Apparatus for loading cavity resonators of tunable velocity modulation tubes
US3775635A (en) * 1971-09-16 1973-11-27 Thomson Csf Power amplifier klystrons operating in wide frequency bands

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3974417A (en) * 1974-12-06 1976-08-10 Nippon Electric Company, Ltd. Four-cavity velocity modulation tube
US4168451A (en) * 1977-07-01 1979-09-18 Nippon Electric Co., Ltd. Multi-cavity klystron amplifiers
US4567452A (en) * 1984-03-20 1986-01-28 The United States Of America As Represented By The United States Department Of Energy Broad-band beam buncher
WO2000030145A1 (en) * 1998-11-16 2000-05-25 Litton Systems, Inc. Low-power wide-bandwidth klystron
US6326730B1 (en) 1998-11-16 2001-12-04 Litton Systems, Inc, Low-power wide-bandwidth klystron
WO2011050193A1 (en) * 2009-10-21 2011-04-28 Omega-P, Inc. Low-voltage, multi-beam klystron
US8559894B2 (en) * 2011-09-01 2013-10-15 Baron Services, Inc. Klystron transmitter
CN110753988A (zh) * 2017-06-13 2020-02-04 佳能电子管器件株式会社 速调管
EP3640967A4 (en) * 2017-06-13 2021-06-23 Canon Electron Tubes & Devices Co., Ltd. KLYSTRON
CN107240539A (zh) * 2017-06-15 2017-10-10 湖北汉光科技股份有限公司 一种65mw大功率速调管
CN107240539B (zh) * 2017-06-15 2023-05-16 湖北汉光科技股份有限公司 一种65mw大功率速调管

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Publication number Publication date
GB1425678A (en) 1976-02-18
JPS5010552A (nl) 1975-02-03
DE2424679A1 (de) 1974-12-05
FR2231098B1 (nl) 1978-10-27
FR2231098A1 (nl) 1974-12-20
NL7406947A (nl) 1974-11-26

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