US2667580A

US2667580A - Magnetron with valence electrode

Info

Publication number: US2667580A
Application number: US122391A
Authority: US
Inventors: Charles V Litton
Original assignee: Individual
Current assignee: Individual
Priority date: 1949-10-20
Filing date: 1949-10-20
Publication date: 1954-01-26
Anticipated expiration: 1971-01-26
Also published as: GB676842A

Description

Jan. 26, 1954 c v L|TTON 2,667,580

MAGNETRON WITH VALENCE ELECTRODE I Filed Oct. 20, 1949 2 Sheets-Sheet' l To ANTENNA INVE NTOR CHARL E5 M L/7'7'0N ATTORNEY Jamzfi, 1954 c. v. LITTON MAGNETRON WITH VALENCE ELECTRODE 2 Sheets-Sheet 2 Filed Oct. 20, 1949 w mft wzwti INVENTOR CHARLES V. L/TTON ATTORNEY Patented Jan. 26, 1954 UNITED STATES PATENT OFFICE MAGNETRON WITH VALENCE ELECTRODE Charles V. Litton, Redwood City, Calif. Application October 20, 1949, Serial No. 122,391 8 Claims. (01. 250-36) The present invention relates to a generator of ultra high frequency waves of high power and particularly to a generator of the magnetron type.

To obtain a larger amount of power at high frequencies the magnetron generator has been most useful. The magnetron is made large to increase the power output. It is sometimes difficult to design magnetrons with the desired power handling capacity for operation at high frequencies because the higher the frequency the smaller the magnetron must be. Therefore it has been proposed to connect a plurality of magnetrons in parallel. In such an arrangement there are many modes of operation obtainable and therefore the device is unstable.

If one considers a magnetron with twelve vanes defining the resonant cavities, there are at least five simple modes of operation in which undesired oscillations tend to build up an infinite number of modes being possible since the resonators have distributed constants. If several such magnetrons are coupled to a common output, there would not only be the modes of the individual tubes but also the modes available by combination of one tube with the others. In the case where ten tubes with twelve vanes are stacked, there would be at least 50 possible modes which would strongly disturb oscillation in the desired mode at the desired frequency.

It is therefore the object of this invention to provide an arrangement of oscillators preferably magnetrons intercoupled in such a way that the number of possible modes at which the scillators will operate is substantially decreased.

More specifically it is an object of this invention to provide an arrangement of magnetrons which will oscillate at only a single mode.

These objects are obtained by interconnecting said oscillators or magnetrons by coupling units which have a length a multiple of a half wave length such that no energy is exchanged between the oscillator circuits or resonators of the magnetrons when they are oscillating at the same frequency. Then if one drifts from the desired frequency, energy will be exchanged and the result will be that the several interconnected oscillators or magnetrons will tend to pull each other into oscillation at the same frequency.

The above mentioned objects and features of this invention will be better understood by reference to the following detailed description of a preferred embodiment given in connection with the accompanying drawings of which Figures 1, 2 and 3 show diagrammatic sketches of coupling arrangement used in explaining my invention;

Figure 4 shows a diagrammatic sketch of six magnetrons coupled together according to my invention; Figure 5 shows in cross-section two magnetrons coupled together and with output coupling means in accordance with an embodiment of my invention; Figure 6 shows a diagrammatic sketch of three magnetrons stabilized according to my invention; and Figure '7 shows a diagrammatic sketch of two magnetrons stabilized by double bonding therebetween in accordance with my invention.

In Figure 1 there is shown two cavity resonators I and 2 of two separate but similar magnetrons. These resonators are connected together by a transmission line which is a wave length or an integral multiple of a wave-length long at the frequency in. If these magnetrons are operating in the same mode and at the same frequency and if there is no phase inversion in the coupling, there will be no net exchange of energy between the two resonators when they are exactly in phase.

The figure shows arrows representing current flow at an instant of time to. There will actually be no current flow through the coupling wave path since the cavity resonators are oscillating in phase and are in eifect coupled in parallel. The high frequency voltages across both ends of the wave path are of the same magnitude and. phase. Any current which the energy from the resonator I would tend to transmit to resonator 2 will be balanced by the current which the energy from resonator 2 would otherwise transmit through the coupling wave path.

In Figure 2 the two resonators I and 2 of the two separate but similar magnetrons are shown directly connected together. The transmission line a wave length long as shown in Figure 1 acts just as the closely coupled arrangement shown in Figure 2. When the two resonators I and 2 in either of these figures are oscillating at the same frequency and in phase and in the same mode no net exchange of energy will occur between them.

In Figure 3 the two resonators I and 2 of the two separate but similar magnetrons are shown coupled by a transmission line a half wave length long with no phase inversion in the coupling. In such a case there is no net exchange of energy when the currents in the two resonators of the two separate magnetrons are out of ]phase. As is obvious, the transmission line must 3 long where 7\ is the operating wave length and n is an integer. This is also true of the case where the coupled resonators are oscillating in phase and there is phase inversion in the coupling.

If for any reason one of the magnetrons drifts or otherwise changes in frequency, the interconnected system of any of Figures 1, 2 or 3 will no longer be balanced. The equilibrium thereof will be disturbed and an energy exchange will occur which will exert a stabilizing force on one or the other or both of the cavity resonators until equilibrium is restored. The action is quite like that occurring amongst the se arate resonators of the multi-cavity magnetron itself. The latter is a closely coupled system of parallel res= onant elements which lock; into synchronisrn at a single frequency. Similarly the closely coupled interconnected system of magnetrons, two of which are shown in Figures 1, 2 or 3, is synchronizedto'gether and may hunt but does so systemwise as a whole. Such hunting would normally. evidence itself as a sudden change from one operating frequency to another.

In Figure 4 there is shown diagrammatically an arrangement of six 'rnagnetrons interconnected in accordance with my invention. Each of the 'magnetrons g'through 8 is provided with a'cathode 9 and six vanes In. These vanes define six cavity resonators. A corresponding cavity resonator in each magnetron is coupled together by a transmission path ll to a similar cavity resonator of an adjacent magnetron. Thus magnetron 3 is coupled to magnetron 4 and magnetron 4 is coupled to magnetron 5 and so forth; magnetron 8 being coupled between magnetrons i and 3, thus forming a closed loop. The coupling between magnetrons 8 and 3 is not necessary. Each of the interconnecting trans mission paths H is shown adjustable in length. As'pointed out in connection with the Figures 1, 2 and 3 the length of the interconnecting lines order that the magnetrons may be in synohronism or equilibrium at the operating frequency is either an odd or an even multiple of a half wave length long at this frequency depending upon the relative phasingof the oscil lations inv the coupled cavity resonators and the sense of the coupling. When the coupling line H; betweenmagnetron's 3 and 4 is of the proper length so; that there will be no not exchange of energy at the desired frequency it, these two resonators will oscillate at the frequency f and if the magnetrons tend to drift or otherwise change in frequency the coupling line II will function to pull them back intoequilibrium. This will be true of all of the magnetrons 3 through 8 In addition magnetrons 3 and 8 are connected together by a transmission path H. Thus if any magnetron in the loop tends to drift or change in frequency all of the others will function to pull it back to the operating fred ejr' cy, 7 V K Separate output connections i2 are shown from each magnetron. Obviously these may be coupled to separate loads, such as to separate a e nasg i ana ienna ar a or h y may be all'coupled in parallel to a single load, thus pro-- viding a large amount of power at the ultrahigh frequency at which the magnetrons are oscillating.

It will be apparent thatan arrangement of magnetrons as shown in Figure 4 will tend to oscillate at those frequencies for which the intercomiecting transmission paths are an odd or even multiple of a half -wave length long depending upon the phasing of the interconnected cavity resonators. Thus a harmonic series of frequencies may be obtained. To eliminate these harmonically related frequencies, the lengths of the interconnecting wave paths may be made different integral multiples of a half wave length of the desired frequency so as to provide additional asymmetry to undesired modes. In the schematic illustration in Figure 4 interconnecting path ll between magntrons 3 and 4 may be made m. long with no phase inversion in the coupling and the path ll between resonators 4 and 5 may be made long with phase reversal in the coupling to resonat'or 5. Then the even harmonics will be eliminated as the path which is necessarily a half wave length long at the operating frequency will not permit them.

A wave transmission path H" is also shown coupled between two of the paths H which form the ring of interconnected magnetrons This path is also adjusted so that there'will be no net exchange of energy between the magnetrons when they are all oscillating in the desired mode. It provides improveaperrormanee of the maj netron and reduces the h'unting as does the path between the resonators 8 and 3 as pointed out above.

Wave guides may be usedto interconnect the magnetrons but it has been found that transmission lines are better since they may be tuned with greater stability than wave guides. Guide wave length changes relatively rapidly with frequency and wave guides are therefore relatively more unstable. On the other hand, wave guides are more efficient means for coupling to a had than transmission lines. The preferred arrangeinent is shown in Figure 5.

In Figure 5-, two magnetrons i3 and 25 are shown in cross section. These magnet-fans rep resent any two of the magnetrons 3-, E, 5; 1-, and 8 shown in Figure 4. Each of these "magnetrons is provided with six vanes From one cavity resonator i6 ofni'a'gnet'ron l3 there is provided an output coupling arrangement I! which matches the impedance of the'cavity' re'sonator'as seen at gap I 8 to the impedance *ofa coaxiaI line I9; The-coaxial 1-1116 I83 202s coupled by a similar matching section M to a cavity resonater 22 of the magnetron M and the line I9, 20 together with the matching sections l1 and 21 is adjusted'to be an even or odd multiple of a half wave length long depending on whether or not the interconnected resonators are oscillating in phase or out of phase and depending on the sense of the coupling. intermediate the ends of the transmission line I9 213 "isp-rovide'dapair of

telescoping lines

23, 24 closely fitting over the conductors "of, the transmission line i9; 28!. The transmission line is formed. from two separate parts which may be separatedand thus the telefscoping sections 23 and fit-serve to adjust'the length of the. coupling; transmissionline. From? anothercavity resonator *of magnetron 1'8:

there is provided amatching section zesimuar tomatching sections H and- 2in This is shown separated by one, resonator from resonator l6 and as alternate resonatorsof a magnetron 'os'c'ila late in phase, resonator 25 will oscillate in phase; with resonator i6. A similar output matching section 21* ifs-provided; from a resonator 2'8f'in ma netron lx4sgwhichfresonator will also oscillate:

in phase with oscillations in resonator 22. In such an arrangement the coaxial line I9, together with the matching sections I1 and 2| are adjusted to be a multiple of a wave length long at the desired operating frequency. From a cavity resonator 29 which is chosen so that it will also oscillate in phase with cavity resonators 6 and there is provided an output impedance matching section which matches the impedance of the cavity resonator as seen at gap 3| to the impedance of a wave guide 32 which is shown coupled to matching section 30. A similar arrangement 33, 34 is shown for the magnetron It is apparent that each interconnecting line need not be limited to the coupling and stabilizing of only two magnetrons. For example three magnetrons may be stabilized by an arrangement as shown in Figure 6.

Resonators 35 and 36 of magnetrons 31 and 38 are connected together by a wave transmission path 39. The resonators are presumed to be oscillating in phase. The connection of path 39 to resonator 35 is reversed with respect to the connection to resonator 36 and so the length of the path 39 is an odd multiple of a half wave length of the operating frequency. Thus magnetrons 31 and 33 are stabilized.

Magnetron 40 is also stabilized by means of a. transmission path 4| connected from one of its resonators 42 to transmission path 39. Resonator 42 is taken to be a'resonator of magnetron 40 that is oscillating in phase with resonators 35 and 36. The connection of path 4| to resonator 42 is in the same sense as the connection of path 39 to resonator 35. Therefore the total path between these two resonators should be an even multiple of a half wave length. If the connection of path 4| to path 39 is made at a point an odd multiple of a half wave length from resonator 35, then the length of path 4| should also be an odd multiple of a half wave length. Then the total length of wave transmission path from resonator 42 to resonator 36 is an odd number of half wave lengths and since these resonators are oscillating in phase and since the connection to one resonator is reversed in sense with respect to the connection to the other, this is the correct length for stabilization.

It is also evident that more than one path may be connected between any pair of magnetrons in order to couple them closely and insure stabilization.

In Figure 7 there is shown two wave transmission paths 43 and 44 each of which couples together a pair of cavity resonators of each magnetron 45 and 46. These paths are shown coupled between resonators of each magnetron which are oscillating in phase and they are shown with 180 phase inversion in the coupling. Therefore they are made an odd multiple of a half wave length long at the desired frequency. In particular path 43 is shown long and path 44 is long. This double bonding may be applied to any number and arrangement of interconnected magnetrons.

While I have described my invention in connection with a magnetron oscillator it will be apparent that the invention is not limited or-restricted to this type of oscillator. Furthermore while I have shown coaxial lines interconnecting the cavity resonators of the magnetrons and while I have shown a wave guide formed by a metal wall, it will be apparent that the interconnections used might also be two wire transmission lines or dielectric wave guides.

It will be understood therefore that the embodiments shown and described herein, are to be regarded as illustrative of the invention only and not as restricting the appended claims.

I claim:

1. An arrangement for the production of ultra high frequency energy of high power with means for stabilizing the frequency of oscillations comprising a plurality of oscillators each having a plurality of resonators and output coupling-units from more than two of said resonators, one of said coupling units of each of said oscillators being an output load coupling unit, an ultra high frequency transmission path connecting each of the remaining coupling units of each of said oscillators to a remaining coupling unit of another oscillator, said transmission paths and said coupling units being matched to said resonators and having a length a multiple of a half wave length such that no energy is exchanged between the resonators when they are oscillating at the same frequency.

2. An arrangement according to claim 1 in which said transmission paths connecting said oscillators comprise paths a multiple of a wave length long connecting resonators of said oscillators which are to oscillate in phase and paths an odd multiple of a half wave length long connecting resonators that are to oscillate out of phase.

3. An arrangement according to claim 1 in which said transmission paths comprise coaxial lines and said output load coupling units comprise wave guides.

4. In an arrangement for the production of ultra high frequency energy of high power comprising a plurality of magnetrons each having a plurality of cavity resonators, a means for stabilizing the frequency of said magnetrons comprising at least two output coupling units from two resonators of each magnetron, and two transmission paths each an integral multiple of a half wave length long and interconnecting two resonators of one magnetron with two resonators of another magnetron.

5. An arrangement for the production of ultra high frequency energy of high power with means for stabilizing the frequency of oscillation comprising a plurality of magnetrons each having a plurality of resonators, an output coupling unit including a resonator-towave-guide matching section coupled to one resonator of each said magnetron, a wave guide connected to each of said above-mentioned coupling units, a pair of output coupling units including a resonator-to-coaxial-line matching section coupled to two additional cavity resonators of each of said magnetrons, a transmission path connecting each of said resonator-to-coaxial-line matching sections of one of said magnetrons to one of said sections of another of said magnetrons, said transmission paths including coaxial lines matched to said matching sections and having a length a multiple of a half wave length such that no energy i exchanged between said resonators when they are oscillating at the same frequency. 1

, e351; arrangement for the; production of ultra high frequency energy of high power witn means for stabilizing the ir queney 0f oscillation comprising a plurality of oscillators eaen havinga plurality of tuned circuits and qouplingruints from more than two of said tuned circuits; one of said'cou'plmg un'itsof each of said oscillators being an output coupling unit, an ultra high fre quency transmigsion path conneetin each of the remainin coupling units of each of said pscma tors to a remaining coupling unit Of another 6S= cillator, said transmission paths and said coupling units being matched. to said tuned circuits and having a length a m'uitiple of a half wave length such that no energy is exchanged between said tuned circuits when they are osciliating at the same frequency.

'7. An arrangement according to claim 5 in which said transmission line's connect said mag= netrons in a closed system.

a. An arrangement eeeeramg to claim 5 in which saidtransmi'ssion lin'e are connected eaen between one of said resofiator-to-coexm-nne matchir'ig sections and 'a common junction point of all or said transmission paths. v

CHARLES v. LIT'ION.

References Cited in the me of this patiit UNITED STATES PATENTS Number Name Date 2,110,448 Linder 1- 1 Mar, 8, 1938 2,173,911 Matthieu Sept. 26, 1939 2,472,200 Everhart June 7, 1949 2,473,828" Sp'ncer June 21, 1949 2 ,474,938 Gorn July 5, 1949 2,481,151 Powers Sept; 6, 1949 2,658,148 Evan's NOV; 3, 1953