US2888649A

US2888649A - Traveling wave tube system

Info

Publication number: US2888649A
Application number: US562472A
Authority: US
Inventors: Edward C Dench; Rue Albert D La
Original assignee: Raytheon Manufacturing Co
Current assignee: Raytheon Co
Priority date: 1956-01-31
Filing date: 1956-01-31
Publication date: 1959-05-26
Anticipated expiration: 1976-05-26

Description

United States Patent 2,888,649 Patented May 26,1959

TRAVELING WAVE TUBE SYSTEM Edward C. Dench, Needham, and Albert D. La Rue, Lexington, Mass., assignors to Raytheon Manufacturing Company, Waltham, Mass., a corporation of Delaware Application January 31, 1956, Serial No. 562,472

12 Claims. (Cl. 332-17) This invention relates to a system for increasing the power obtainable with traveling wave oscillators and, more particularly, to a system employing two or more tunable traveling Wave oscillators whose frequency of operation is reasonably close together, wherein a signal generated by each oscillator other than the one connected to the output load is injected as an input signal into another'one' of said oscillators.

Traveling'wave oscillators are known which include a periodic slow wave propagating structure which has the properties of an electrical filter, that is, waves can be propagated over the pass band of the structure. Such tubes make use of the interaction between an electron beam moving along paths adjacent the periodic structure and the electromagnetic field of the wave guided by said periodic structure.

The electromagnetic field along such a structure may be considered to consist of an infinite number of superimposed traveling waves or space harmonics each having phase velocities V given by where A is the pitch or length of one network section, is the phase shift per section, and n is the number of the space harmonic, for example, n=0, :1, :2, etc. The phase velocity of the space harmonics may be either positive or negative, depending upon the value of n. When V has a positive value, the phase velocity is in the same direction as the energy or group velocity and the corresponding phase harmonics may be referred to as forward waves. On the other hand, when V is negative, the phase velocity is in a direction opposite to the energy or group velocity and the corresponding waves then are referred to as negative space harmonics or backward waves.

If, for example, an electron beam flows in the direction of one of these backward waves at a velocity substantially equal to the phase velocity of the backward wave, interaction will take place between the beam and the traveling wave and a progressive modulation of the electron beam is obtained such that energy will be transferred from the electron beam to the electromagnetic field and the energy given to the backward wave will be transferred along the periodic structure toward the electron beam source. When the electron beam current is in excess of a critical current where oscillations can begin and when the electron beam velocity is substantially equal to the velocity of the one of the space barmonies, such as a backward wave, oscillations will be generated within the tube; these oscillations will propagate along the periodic structure and may be extracted at one end of the periodic structure.

In a first type of backward wave oscillator, the electron beam is accelerated by an electric field associated with the electron gun and, in some instances, in an axial magnetic field for focusing the electron beam. In a second type of a backward wave oscillator the beam moves through a magnetic field which is arranged transversely to an electric field which may be produced by a voltage supplied between the periodic delay structure and either the electron source or an auxiliary negative electrode. In the first type of oscillator, the electron beam velocity is dependent upon the magnitude of the voltage which causes acceleration of the electrons; in the second type, the average forward electron beam velocity is directly a function of the aforesaid voltage and is directly determined by the ratio of the electric and mag netic field strengths.

Such oscillators may be tuned over a wide range of frequencies by varying the electron beam velocity through adjustment of said voltage, as well as by adjustment of the transverse magnetic field strength in those oscillators employing a transverse magnetic field.

In accordance with the invention, two traveling wave, oscillators whose free running frequencies are relatively close together may be connected in tandem, that is, with the output from the first or driver tube connected as an input signal to the second or driven tube at the end of the driven tube remote from its output end. In this manner, it has been found in practice that the power output derived from the driven tube may be greater than the combined power output of both tubes operating independently. In other words, the efiiciency of the driven or locked oscillator may be increased over the efiiciency of the same oscillator when operating alone. The oscillators can be made voltage tunable over a relatively wide range and the tuning means of the oscillators may be ganged or otherwise arranged so that the frequency of oscillation of the driven oscillator can be locked to that of the incoming signal derived from the driver oscillator over the entire tuning range.

The invention is not limited, however, to a system consisting of two oscillators. Any number of oscillators of comparable frequency, depending upon the power and requirements of the system, can be cascaded to form a chain of injection-locked units; each oscillator will then operate, in effect, as a locking or driver oscillator for the next oscillator in the chain. The frequency of the last oscillator of the chain which is connected to a utilization circuit is locked substantially to that of the first oscillator in the chain. It has been found in practice that the power output obtained from the last stage of the chain may be greater than the sum of the power outputs of all the oscillators in the chain. For example, if three oscillators are connected in tandem in the manner described, the power output, in some instances, is greater than three times the power output of each tube operating independently.

The systems according to the invention may be either amplitude or frequency modulated by application of an amplitude modulating signal or a frequency modulating signal to one or more of the oscillators. Amplitude modulation of a limited range may also be achieved con currently with frequency modulation by applying a frequency modulating signal to less than all of the oscillators.

The systems according to the invention are quite reliable since, if one or more of the tubes in the chain should fail, owing for example to a defective electron gun, energy will continue to propagate along the delay structure of the faulty tube or tubes, so long as at least one of the tubes is operating satisfactorily. Even if the driver oscillator in a two-tube system should fail, it would act as a termination for the other tube, and energy, albeit at reduced power, may be derived from the output end of the driven tube.

Reflections within the system may be minimized by means of electrical attenuation inserted either externally of the tube or within the tubes themselves.

This invention further contemplates the use of a high frequency generator other than a backward wave traveling wave oscillator for supplying the initial locking signal. In systems which are required to operate over a range of frequencies, however, it is necessary to insure that the frequency of the locking signal tracks with that of the traveling wave oscillator or oscillators in the system.

Other objects and features of this invention will be understood more clearly and fully from the following detailed description of the invention with reference to the accompanying drawings wherein:

Fig. l is a central cross-sectional view, partly in elevation, of an embodiment of a traveling wave oscillator tube which may be utilized in the system according to the invention;

Fig. 2 is a detail view of a portion of the anode assembly of the traveling wave oscillator tube of Fig. 1;

Fig. 3 is a section view taken along the line 3-3 of Fig. 1;

Fig. 4 is a fragmentary view of a portion of the electron gun mounting assembly attached to an elongated electrode of the traveling wave oscillator tube of Fig. 1;

Fig. 5 is a schematic diagram of a first embodiment of an injection-locked traveling wave oscillator system according to the invention;

Fig. 6 is a schematic diagram of a modification of the system shown in Fig. 5;

Fig. 7 is a diagrammatic view of a further embodiment of the system according to the invention in which more than two oscillator tubes are employed;

Fig. 8 is a diagrammatic view of a further modifica tion of the system accordin to the invention illustrating the use of oscillator tubes having no transverse magnetic field; and

Fig. 9 are curves illustrating certain principles of operation of the invention.

Referring now to Figs. 1 to 4, a traveling wave tube oscillator is shown which comprises an anode assembly 21 which includes a periodic slow wave energy propagating structure or anode delay line 22, an elongated electrode 30, sometimes referred to as a sole, maintained negative with respect to anode delay line 22, a lead-in assembly 40, an output coupling means 50, an electron gun mounting assembly 60 further including at least a cathode 61 and heater 62, an input coupling means 76, and a transverse magnetic field-producing means 8@81, a portion of which is indicated in Fig. l.

The anode assembly comprises a circular interdigital delay line including a plurality of interdigital fingers or

members

24 and 24 which extend from oppositely disposed

annular members

25 and 25, respectively.

Members

25 and 25 are secured by screws 26 (see Fig. 2) to the shoulder portion of a cylindricai electrically conductive ring 27. The remainder of the anode assembly includes a pair of oppositely located

cover plates

28 and 29 hermetically sealed to ring 27.

The sole 3% consists essentially of a cylindrical block of material, such as copper, having a flange portion 37. A centrally located aperture 31 is provided in the sole to permit connection of lead-in assembly 46 and to allow for passage of external circuit-connecting leads in a manner to be shown subsequently.

Lead-in assembly 44) includes an electrically conductive cylindrical sleeve 42 which is inserted in an aperture in cover plate 28 and is securely attached thereto. A section of cylindrical glass tubing 43 interconnects metal sleeve 42 and a second metal sleeve 44. The other end of sleeve 44 is provided with a glass seal 45 for sealing tube 24) after evacuation.

Sleeves

42 and 44 preferably are constructed of a material having an expansion coefiicient closely approximating that of tubing 43. The

assembly 40 is arranged perpendicularly to cover plate 28 of tube 20 and further includes an elongated electrically conductive tubular supporting cylinder 46 which serves as the main support for sole 30. One end of cylinder 46 is afiixed to the periphery of aperture 31 in sole 3%. The other end of cylinder 46 contains an outwardly flared portion 47 which is connected to the inner surface of sleeve 44. The necessary leads for the electron gun are fed through supporting cylinder 46 and are insulatedly supported therefrom by one or more glass beads 4-9.

The interdigital anode delay line 22 is arranged concentric with sole 30 and is separated from the circumferential wall 33 of the sole to form an interaction space through which the electron beam generated by the electron gun passes. Anode delay line 22 may be terminated at one end by attenuation which may be in the form of an energy-dissipative material, such as iron, applied to the fingers.

The coaxial output coupling means 50 is sealed in an opening of wall 27 of the anode and is impedance matched to the anode delay line 22. The inner conductor 52 of coaxial output coupling means 50 is connected to a finger at or adjacent the end of the periodic anode delay line 22 adjacent the electron gun.

Traveling wave tube 20 may be provided with a collector electrode 23, shown in Figs. 2 and 3, for intercepting electrons after one traversal of the arcuate inter action space. This collector electrode may take the form of a projection from the back wall 27 of the anode delay line 22. In some instances, however, the collector electrode may be omitted and the electron stream made reentrant. Furthermore, the sole 30 may be either primarily or secondarily electron-emissive.

The electron gun assembly for the tube of Fig. 1 includes cathode 61, heater 62, and auxiliary electrode 65, as shown in detail in Fig. 4. The cathode 61 is shown, by way of example, as a rectangular body provided with a circular bore 63 in which the heater 62 is inserted. Cathode body 61 has at least the surface facing the interaction space 35 coated with an electronemissive material, such as a compound of barium. Cathode 61 is positioned within a recess or slot 32 in the wall 33 of sole 30. Electrical connection to the cathode is made by way of a rigid, electrically conductive stake 66 which may be made of molybdenum and spot welded to one end of the cathode body. The cathode lead 48 is connected to stake 66. One end of heater 62 is connected to the inner wall of the cathode body while the other end of the heater is attached to a stake 67; stake 67 is insulatedly mounted by means of a bushing 64 on the top face of sole 30, as shown clearly in Fig. 4. The heater lead 19, shown in Fig. 1, is attached to stake 67.

The cathode 61 is supported by means of a flange 68 which may be secured, as by brazing, to the cathode body at one end, as shown in Fig. 4, and attached, as by insulating screws (not shown) to a portion of the sole at the bottom of slot 32. Cathode 61 is insulated from sole 36 by means of an electrically insulated spacer 15. The auxiliary electrode which, in effect, is an accelerating anode serving to aid in the production of the desired electron beam trajectory, is supported from sole by means of insulating screws 16 which pass through flange portion 65 of auxiliary electrode 65 and into flange portion 37 of sole 30. An electrically insulating spacer 17 provides for electrical isolation of the auxiliary electrode 65 and sole 3%. Electrical connection is made to auxiliary electrode 65 by means of a stake 69 aflixed to one end of the auxiliary electrode and electrically in sulated from the sole by virtue of its passage through an aperture 18 in the sole. Lead 41 is attached to stake 69.

A suitable electric field between anode and sole may be obtained by means of a voltage applied therebetween. The sole may be negatively biased with respect to the cathode by means of a source 107 of voltage connected between cathode leads 48 and tubular sleeve 46 by way of sleeve 44. The cathode may, in some instances, be at the same potential as the sole. Similarly, anode delay line 22 may be maintained at a positive potential relative to both sole and cathode by means of a source 105 of voltage connected between metal sleeve 42 connected in turn to the anode delay line and cathode lead 48. The auxiliary electrode 65 may be maintained at a positive potential relative to the cathode by means of a source 109 of voltage connected between leads 41 and 48.

A uniform magnetic field transverse to the direction of propagation of the electron beam is provided either by a permanent magnet or an electromagnet having

cylindrical pole pieces

80 and 81 radially positioned on or adjacent the tube. Pole piece 80 is apertured to receive the leadin assembly 40 and pole piece 81 is apertured to maintain symmetry of the magnetic field. The flux lines should be concentrated in the interaction space 35 between sole 30 and cylindrical anode delay line 22. By proper adjustment of the magnitude and polarity of the magnetic and electric fields, the electron beam may be made to follow a circular path about interaction space 35 under the combined influence of these transversely disposed fields.

The radio frequency energy generated in the interaction space 35 traveling along anode delay line 22 sets up a high frequency electromagnetic field which may be analyzed as a series of space harmonics, some of which travel in one direction (clockwise) along the anode structure, and others of which travel counterclockwise, and all of which travel with different phase velocity. If the electron beam is synchronized with the proper space harmonic, interaction of the beam and this space harmonic will result in the production of oscillations within the tube. The energy travels toward the electron gun and is extracted at the gun end of anode delay line 22 by way of the coaxial output line 50.

Traveling wave tube 20 further includes an input coupling assembly 70 comprising inner conductor 71 and an outer conductor 72 coaxially arranged with respect to one another. The inner conductor 71 is connected to one of the fingers at or adjacent the end of the anode delay line 22 electrically remote from the electron gun, while the outer conductor 72 may be attached to the cylindrical wall 27 of anode assembly 21.

The input coupling means 70, as well as output coupling means 50, need not be coaxial; for example, the energy may be coupled to or from the anode delay line 22 by means of a wave guide.

Referring now to Fig. 5, two backward wave oscillators, such as described in Figs. 1 to 4, are represented by the

reference numerals

20a and 20b. These oscillators are indicated schematically in Fig. 5 as linear, for reasons of simplicity. The systems of the invention are not restricted to any particular configuration of oscillator 2, however, and oscillators of the linear type may be used in accordance with this invention. Each oscillator tube includes a periodic slow wave propagating network for anode delay line 22 shown, by way of example, only as an interdigital line having a plurality of interdigital fingers, or elements, such as

elements

24 and 24 of the device shown in Figs. 1 to 4, each of which is connected together for direct current. The delay line 22 need not be of the interdigital type, however, but may be any suitable periodic delay structure such as a helix, discloaded Wave guide, or the like. Each tube includes an elongated electrode or sole 30, which is maintained negative with respect to delay line 22 by means of the unidirectional source of voltage 105 and the unidirectional source of voltage 107 connected between the anode delay line 22 and sole 30. An electric field thereby is produced between anode delay line 22 and sole 30.

Each tube further includes an electron gun comprising a cathode 61 and an auxiliary electrode (accelerating anode) 65 for directing a beam of electrons 100 substantially parallel to the anode delay line 22 under the influence of the electric field and a magnetic field transverse thereto. The electron beam may impinge on a collector electrode 23 which may be maintained at the same potential as the anode delay line 22 or at some potential positive relative to the cathode. In some instances, the collector 23 may be omitted and the electron beam allowed to impinge upon the delay line 22; since the region remote from the electron gun is normally an attenuating region, the impingement of the electron beam upon the anode delay line usually is of no consequence.

Tuning of each oscillator may be accomplished by varying the voltage between delay line 22 and sole 30; in practice, this voltage variation may be achieved by connecting a potentiometer 104 across voltage source 105 in a manner such as indicated in Fig. 6. Tuning of each oscillator also may be accomplished by varying the magnetic field strength, either by varying the position of the magnet pole pieces, in the case of a permanent magnet, or by varying the electric current, in the case of an electromagnet having a coil surrounding the core. Variation of both electric field and the magnetic field simultaneously, of course, is possible.

In the diagram of Fig. 5, the oscillators are of a transverse magnetic field type in which the electron beam is under the combined influence of an electric field and a magnetic field transverse to the electric field; the electron beam is mutually perpendicular to the direction of both fields. This magnetic field is indicated by the letter B and the direction of the field is indicated by a cross within a circle. In tubes of this type, the electron beam velocity is proportional to the ratio of the anode delay line-to-sole voltage and the magnetic field strength (flux density). This invention, however, is applicable equally to an oscillator in which an accelerated electron beam travels in the interaction space adjacent the anode delay line and in which as a magnetic field, if used at all, is an axial field which serves only to focus the electron beam. In an oscillator of this type, shown schematically, for example, in Fig. 8, the electron beam velocity is proportional to the square root of the voltage through which the electrons have been accelerated.

Energy is removed from the end of the periodic anode delay structure 22 adjacent the cathode 61 by means of an output coupling device 50 such as already described in Figs. 1 to 4. Amplitude modulation of each oscillator may be accomplished by means of an amplitude modulating signal from a source 112 applied to the circuit containing auxiliary electrode 65 across terminals 113; terminals 113 are connected, respectively, to one end of the bias supply 109 and cathode 61.

In order to achieve proper locking of the oscillators, itis essential that the frequency of operation of each tube, running by itself, be near that of the other tube or tubes, for example, within about 5%. In order to insure that the nominal free running frequencies of operation of the various oscillators do not differ appreciably, it may be necessary to compensate for individual differences in construction and in electrode voltages of the oscillators by means of a bias voltage source 107 connected between cathode 61 and sole 30. The bias can be adjusted on each oscillator until the operating frequencies are substantially equal. If the devices have substantially identical characteristics, the bias sources may, of course, be omitted. It has been found that, in many instances, the space charge conditions for a tube being driven and the same tube running freely are slightly dilferent. This may be another reason for utilizing separate bias power supplies for the various tubes.

The driven oscillator tube 20b must be provided with an input coupling device 70 which is coupled to the periodic anode delay structure 22 adjacent the end remote from its cathode. The output coupling device may be similar in construction to that of the input coupling device 50 and may be coupled to the anode delay structure 22 in the same manner. Attenuation may be introduced at the end of tube 20b remote from the output end, in order to reduce reflections from the driven oscillator 2% back through the system into the driver oscillator 20a, and also to take care of reflections which may arise at the interconnection between the tubes. Furthermore, the use of attenuation eliminates frequency discontinuities in the oscillator during tuning. This attenuation may take form or" a thin coating of lossy material such as graphite applied to the end of the delay line 22, as by spraying a solution of graphite mixed with a suitable binder, or by coating the delay line with iron by electroplating techniques. The attenuation is indicated in Fig. 5 and in succeeding figures of the drawing by cross-hatching or oblique lines drawn through the anode delay line 22.

Energy generated by the driving oscillator 28a is re moved therefrom by means of output coupling device 58 and is applied to the input coupling device '70 of the driven oscillator Ebb by way of a transmission line 111 which may be, for example, a coaxial line. The driver oscillator tube 20a, like the driven oscillator 20b, may be provided with a coupling device 70 coupled to the end of the anode delay line 22 remote from its cathode. This attenuation may take the form of a thin coating of external lossy termination 115 which is of such impedance as to reduce substantially reflections within the tube Zita. External attenuation may also be introduced in the line 111 interconnecting the two oscillators. As shown in Fig. 6, internal attenuation may be introduced in the driver tube 20a rather than external attenuation. The advantage accruing from the use of external attenuation is standardization of tubes, whereas the advantage of internal attenuation is that somewhat better impedance matching may be achieved with internal attenuation than with external attenuation. It should be noted, however, that the invention does not necessarily contemplate the use of attenuation; in some instances, the reflected energy may be of insuflicient magnitude to prove troublesome.

The advantages of injection-locked backward-wave oscillator operation is clearly shown in the curves of Fig. 9, in which the relationship between relative power and relative frequency is indicated. The power obtained by the use of a single oscillator operating independently is indicated by the lower curve 152, while the power obtained when two oscillators are cooperating in the manner described in Fig. 6 is indicated by the uppermost curve 150. It will be noted in this case that the power obtained by the use of two oscillators utilizing the injection locking principle according to the invention is more than double the power obtained by using a single oscillator only.

In Fig. 6, a modification of the system of Fig. 5 is shown wherein a common power supply 105 is used for both tubes, and wherein means are provided for frequency modulating the system. Voltage tuning of the oscillators 28a and 26/) may be accomplished simultaneously by varying the position of the arm of potentiometer 104 connected across battery 105. Frequency modulation is accomplished by a modulating signal from a modulating source 118; the modulation signal may be inserted in one of three positions, that is, between terminals 120, between terminals 122, or between terminals 124. Jumpers 121 are provided across the unused terminals. 1f the modulation signal from source 118 is inserted across terminals 120, that is, in the circuit be tween anode 22 and sole 30 of both driver tube 20a and driven tube 2%, as shown in Fig. 6, frequency modulation may be eflected with substantially no amplitude modulation, since the frequency of both oscillators is being varied simultaneously and the oscillators are in step, frequency-wise. If the modulation signal is inserted between terminals 122, that is, in the circuit between the anode and sole of the driver tube 20a, the driven tube 201) will follow over the locking range,

that is, over a narrow range of frequency, for example, about 5 to 10 percent removed from the nominal freerunning frequency of each oscillator; the power output, however, is changed in such a case. Finally, if a moduiation signal is introduced between terminal 124, that is, in the circuit between anode and sole of the driven tube 2%, the output frequency of the system is substantially equal to the frequency of the driver tube within the locking range; in this case, also, the power output will vary with the signal applied to terminals 124.

Since the application of a modulation signal between terminals 122 or between terminals 124- produces some amplitude modulation, an alternative method to that of provided. However, the percentage amplitude modula tion which may be achieved by applying a modulation signal between the sole and anode delay line is less than that attainable by applying an amplitude modulation signal to the electron gun, in the manner shown in Fig. 5. Although the attenuation is shown in Fig. 6 as being inserted in the delay line of the driver tube 20a, it is possible to insert the attenuation externally, as shown in Fig. 5.

In Fig. 7, a system is illustrated which incorporates more than two oscillators, that is, wherein several injection-locking units may be cascaded. If several oscillators are thus cascaded, the power output obtained from the last oscillator in the chain and available for utilization is greater than the sum of the power outputs of all of the oscillators when each oscillator is acting independently. The output from each oscillator is applied to the input of the next oscillator so that each oscillator, save the one to which the output load is coupled, acts as a driver for the one following. For reasons already mentioned, internal attenuation may be provided at the input end of the delay line, that is, at the end remote from the output end, in the case of the initial driver tube. As previously explained, attenuation inserted in the delay line of the initial driver tube Zita may be either internal or external. When several tubes are utilized, the energy reflected, in the absence of attenuation, may well be considerable and may be greater than the power-handling capability of one or more of the tubes, particularly the initial driver tube 20a.

As in the system of Fig. 6, a common power supply may be used in the system of Fig. 7 in the circuit between the sole 3d and the anode delay line 22 of all of the tubes. Furthermore, a common cathode-to-sole power supply 107 and a common auxiliary electrode-tocathode power supply 109 may be used for all tubes. It is possible, of course, to use a separate power supply for each tube.

As previously mentioned, this invention is not limited to oscillator tubes using a transverse magnetic field. In Fig. 8, a system is illustrated which utilizes a backward oscillator without a transverse magnetic field. Such tubes may include a slow wave propagating network in the form of a helix 22 through which an electron beam is directed by means of an electron gun including a cathode 61, a control grid 130, and an auxiliary anode 132, and, some cases, a beam focusing means comprising an axially arranged coil 135 for producing a longitudinal magnetic field. The electron beam impinges on a collec tor electrode 23 after traversing the length of helix 22. The collector is maintained positive with respect to the cathode 61 by means of a unidirectional high voltage source, such as a battery 1615. In some cases, a separate collector circuit may be omitted. The voltage source can be connected directly to the anode delay line or helix 22. The auxiliary anode 132 is maintained at some fixed positive voltage relative to the cathode by means of an electron voltage source 147 whose negative terminal is connected to the cathode. Amplitude modulation is achieved by varying the negative control grid voltage applied between the control grid and the cathode 61;

this may be accomplised by a potentiometer 138 shunting voltage source 140. As the arm of potentiometer 138 1s moved upward, the control grid voltage, relative to the cathode, becomes more negative, and the power output of the oscillator tube can be decreased; as the potentiometer arm is moved downward, of course, tube power is increased. Tuning with each oscillator is accomplished by varying the voltage between the helix (or collector) and the cathode. This voltage may be varied by adjustment of the arm of potentiometer 145 shunting the high voltage source 105.

Although the oscillator shown in Fig. 8 includes a helix, it is possible to employ an interdigital line such as shown in Figs. to 7.

This invention is not limited to the particular details of construction, materials and processes described, as any equivalents will suggest themselves to those skilled in the art. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

1. In combination, a traveling wave oscillator including an electron source, means for directing a beam of electrons from said source along an extended path, a pcriodic slow wave energy propagating structure positioned adjacent said path in which there is induced by the electron beam an electromagnetic wave traveling in a direction opposite that of the electrons to generate oscillatory energy of a predetermined frequency, an output means coupled adjacent the end of said structure nearer said electron source for removing energy propagating along said structure, an input coupling device coupled to said structure adjacent the end thereof remote from said electron source, and means for supplying an external signal of substantially said predetermined frequency to said input coupling device.

2. In combination, a first traveling Wave oscillator, a second traveling wave oscillator, each including an electron source, means for directing a beam of electrons from said source along an extended path, a periodic slow wave propagating structure positioned adjacent said path in which there is induced by the electron beam an electromagnetic wave traveling in a direction opposite that of the electrons to generate oscillatory energy, and an output means coupled adjacent the end of each of said structures nearer said electron source for removing energy propagating along the corresponding periodic structure, an input coupling device coupled to the structure of said second oscillator adjacent the end thereof remote from the corresponding electron source, and means for interconnecting the output means of said first oscillator to the input coupling device of said second oscillator, said second oscillator being locked in frequency to that of said first oscillator in response to energy received from said first oscillator by way of said interconnecting means.

3. In combination, a first traveling wave oscillator, a second traveling wave oscillator, each including an electron source, means for directing a beam of electrons from said source along an extended path, a periodic slow wave propagating structure positioned adjacent said path in which there is induced by the electron beam an electromagnetic wave traveling in a direction opposite that of the electrons to generate oscillatory energy, means for providing an electric field in the region of said structure, an output means coupled adjacent the end of each of said structures nearer said electron source for removing energy propagating along the corresponding periodic structure, means for varying the frequency of said oscillators simultaneously over a predetermined frequency range in response to variations in said electric field, said oscillators operating individually at substantially the same frequency, an input coupling device coupled to the structure of said second oscillator adjacent the end thereof remote from the corresponding electron source, means for interconnecting the output means of said first oscillator to the input coupling device of said second oscillator, said second oscillator being locked in frequency to that ofsaid first oscillator over said frequency range in response to energy received from said first oscillator by way'of said interconnecting means.

4. In combination, a multiplicity of traveling wave oscillators, each including an electron source, means for directing a beam of electrons from said source along an extended path, a periodic slow wave propagating structure positioned adjacent said path in which there is induced by the electron beam an electromagnetic wave traveling in a direction opposite that of the electrons to generate oscillatory energy, and an output means coupled adjacent the end of said structure nearer said electron source for removing energy propagating along said structure, said oscillators being adapted to operate individually at substantially the same frequency, said oscillators other than the first oscillator including an input coupling device coupled to a corresponding one of said structures adjacent the end thereof remote from its electron source, and means for interconnecting the output means of each of said oscillators other than the last oscillator to the input coupling device of the immediately succeeding oscillator, each of said oscillators other than said first oscillator being locked in frequency to that of the immediately preceding oscillator in response to energy received from the immediately preceding oscillator by way of said interconnecting means.

5. In combination, a multiplicity of traveling wave oscillators, each including an electron source, means for directing a beam of electrons from said source at a given average velocity along an extended path, a periodic slow wave propagating structure positioned adjacent said path in which there is induced by the electron beam an electromagnetic wave traveling in a direction opposite that of the electrons to generate oscillatory energy, and an output means coupled adjacent the end of each of said structures nearer said electron source for removing energy propagating along said structure, means for varying the frequency of said oscillators simultaneously over a predetermined frequency range in response to variations in said average velocity, said oscillators operating individually at substantially the same frequency, said oscillators other than the first oscillator including an input coupling device coupled to a corresponding one of said structures adjacent the end thereof remote from its electron source, and means for interconnecting the output means of each of said oscillators other than the last oscillator to the input coupling device of the immediately succeeding oscillator, each of said oscillators other than said first oscillator being locked in frequency to that of the immediately preceding oscillator in response to energy received from the immediately preceding oscillator by way of said interconnecting means.

6. In combination, a multiplicity of traveling wave oscillators, each including an electron source, means for directing a beam of electrons from said source along an extended path, a periodic slow wave propagating structure positioned adjacent said path in which there is induced by the electron beam an electromagnetic wave traveling in a direction opposite that of the electrons to generate oscillatory energy, and an output means coupled adjacent the end of each of said structures nearer said electron source for removing energy propagating along said structure, means including a single source of voltage connected between each of said electron sources and a corresponding one of said structures for providing an electric field therebetween, means for producing a magnetic field in each oscillator transverse to said electric electron source, and means for interconnecting the output means of each of said oscillators other than the last oscillator to the input coupling device of the immediately succeeding oscillator, each of said oscillators other than said first oscillator being locked in frequency to that of the immediately preceding oscillator in response to energy received from the immediately preceding oscillator by Way of said interconnecting means.

7. In combination, a multiplicity of traveling Wave oscillators, each including an electron source, an auxiliary element located adjacent said electron source, means for directing a beam of electrons from said source along an extended path, a periodic slow Wave propagating structure positioned adjacent said path in which there is induced by the electron beam an electromagnetic wave traveling in a direction opposite that of the electrons to generate oscillatory energy, and an output means coupled adjacent the end of each of said structures nearer said electron source for removing energy propagating along said structure, means including a common source of voltage applied to a corresponding one of said structures for providing an electric field therebetween, means for producing a magnetic field in each oscillator transverse to said electric field, means for varying the frequency of said oscillators simultaneously over a predetermined frequency range in response to variations in at least one of said fields, said oscillators operating independently at substantially the same frequency, said oscillators other than the first oscillator including an input coupling device coupled to a corresponding one of said structures adjacent the end thereof remote from its electron source, means for interconnecting the output means of each of said oscillators other than the last oscillator to the input coupling device of the immediately succeeding oscillator, said oscillator other than said first oscillator being locked in frequency to that of the immediately preceding oscillator in response to energy received from the immediately preceding oscillator by Way of said interconnecting means, and means for applying an amplitude modulating voltage to said auxiliary element to control the amplitude of the energy extracted from the last of said oscillators.

8. In combination, a multiplicity of traveling Wave oscillators, each including an electron source, an auxiliary element located adjacent said electron source, means for directing a beam of electrons from said source along an extended path, a periodic slow wave propagating structure positioned adjacent said path in which there is induced by the electron beam an electromagnetic Wave traveling in a direction opposite that of the electrons to generate oscillatory energy, and an output means coupled adjacent the end of each of said structures nearer said electron source for removing energy propoagating along said structure, means including a common source of voltage applied to a corresponding one of said structures for providing ar electric field therebetween, means for producing a rnrgnetic field in each oscillator transverse to said electric field, means for varying the frequency of said oscillators simultaneously over a predetermined frequency range in response to variations in at least one of said fields, said oscillators operating independently at substantially the same frequency, said oscillators other than the first oscillator including an input coupling device coupled to a corresponding one of said structures adjacent the end thereof remote from its electron source, means for interconnecting the output means of each of said oscillators other than the last oscillator to the input coupling device of the immediately succeeding oscillator, said oscillator other than said first oscillator being locked in frequency to that of the immediately preceding oscillator in response to energy received from the immediately preceding oscillator by Way of said interconnecting means, means for applying an amplitude modulating voltage to said auxiliary element to control the amplitude of the energy extracted from the last of said oscillators, and

means for applying a frequency modulating signal to said structure of at least one of said oscillators.

9. In combination, a multiplicity of traveling Wave oscillators, each including an electron source, means for directing a beam of electrons from said source along an extended path, a periodic sloW wave propagating structure positioned adjacent said path in which there is induced by the electron beam an electromagnetic Wave to generate oscillatory energy, and an output means coupled to each of said structures for removing energy propagating along said structure, said oscillators being adapted to operate individually at substantially the same frequency, said oscillators other than the first oscillator including an input coupling device coupled to a corresponding one of said structures, means for interconnecting the output means of each of said oscillators other than the last oscillator to the input coupling device of the immediately succeeding oscillator, each of said oscillators other than said first oscillator being locked in frequency to that of the immediately preceding oscillator in response to energy received from the immediately preceding oscillator by way of said interconnecting means.

10. In combination, a first voltage tunable traveling wave oscillator having an output terminal, a second voltage tunable traveling wave oscillator having an input terminal and an output terminal, said oscillators being adapted to operate individually at substantially the same frequency, and means for interconnecting the output terminal of said first oscillator and the input terminal of said second oscillator.

11. In combination, a multiplicity of voltage tunable traveling Wave oscillators, each including an electron source, means for directing a beam of electrons from said source at a given average velocity along an extended path, a periodic slow wave propagating structure positioned adjacent said path in which there is induced by the electron beam an electromagnetic wave, an output means coupled to said structure, and an input coupling device coupled to said structure, means for interconnecting the output means of each of said oscillators other than the last oscillator to the input coupling device of the immediately succeeding oscillator, and means for deriving an output for utilization from the output means of the last of said oscillators.

12. In combination, a multiplicity of voltage tunable traveling Wave oscillators, each including an electron source, means for directing a beam of electrons from said source at a given average velocity along an extended path, a periodic slow Wave propagating structure positioned adjacent said path in which there is induced by the electron beam an electromagnetic wave, an output means coupled to said structure, and an input coupling device coupled to said structure, means for interconnecting the output means of each of said oscillators other than the last oscillator to the input coupling device of the immediately succeeding oscillator, means for deriving an output for utilization from the output means of the last of said oscillators, and means for tuning all of said oscillators concurrently.

References Cited in the file of this patent UNITED STATES PATENTS 2,611,832 Lapostolle Sept. 23, 1952 2,616,990 Knol et al Nov. 4, 1952 2,653,270 Kompfner Sept. 22, 1953 2,702,370 Lerbs Feb. 15, 1955 2,723,376 Labin Nov. 8, 1955 2,726,332 Arditi et al. Dec. 6, 1955 2,733,305 Diemer Jan. 31, 1956 2,748,268 Whinnery May 29, 1956 2,760,161 Cutler Aug. 21, 1956 OTHER REFERENCES Traveling Wave Tubes, by Hutter et al., Radio Electronic Engineering, April 1954, page 23.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,888,649 May 26, 1959 Edward C. Dench et a1.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, line '73, for "leads" read lead column 6, line 34, after "which" strike out "as" column "7', line 23, strike out "attenuation may take the form of a thin coating of" and insert instead coupling device may then be connected to an column 8, line 14, after "of" insert -vapplying an amplitude modulation signal between auxiliary electrode 65 and cathode 61 of the electron gun is line 61,- after "and," insert in Signed and sealed this 20th day of' October 1959.

(SEAL) Attest:

KARL H. AXLINE Commissioner of Patents