US2477317A - Electron discharge device - Google Patents

Description

July 26, 1949. P, L, SPEN ER 2,477,317

ELECTRON DISCHARGE DEVICE Filed March 21, 1945 2 Sheets-Sheef l July 26, 1949. A P. SPENCER ELECTRON DISCHARGE DEVICE Filed March 21, 1945 I I I 1 11 a iiiRiis Patented July 26, 1949 UNITED STATES PATENT OFFICES ELECTRON DISCHARGE DEVIGE Percy L. Spencer, West Newton, Mass asslgnor to Raytheon Manufacturing Company,.Newton,

Mass a corporation of Delaware Application March 21, 1945, Serial No. 583,922

tune the tube so as to vary the frequency ofthe oscillations generated; by the tube. It is also desirable thatpthe tuningarrangement have substantially in inertia so that the frequency generated by the tube may be modulated at a very high rate. In this way the tube may be frequency-modulated in accordance with a desire signal variation. 7 1

One of the objects of this invention is to DI'Q- vide a novel and eflicient means for varying the frequency oscillations generated by the tube.

Another object of this invention is to devise such a means which is substantially inertialess.

The foregoing and other objects of the invention will be best understood from the following description of exemplifications thereof, reference being had to the accompanying drawings where vention, said sectionbeing taken along line l--.-l of Fig. 2; 1 1

' Fig. 2 is a transverse cross section taken alonglineZ-J of Fig. 1;

Fig. 3 is a fragmentary'view partly broken away wise formed of conducting material. The hollow cylindrical block I has formedupon its interior surface a central annular projectionl to which is soldered a plurality of suitably spacedradially disposed plates or arms 5. The arms 5, block l and end caps 2 and 3 constitute the anode structure. The interior ends of the arms 5 form anode faces for receiving electrons emitted from a cathode Gcentrally disposed within the anodestructure.

'Ihe cathode 6 is preferably of the indirectly heated oxide-coated, thermionic, type provided with anouter electrically conducting sleeve! within which is contained a heater coilinot 9 Claims. (01. ze -27.5,

Fig. 1 is a transverse section through a magnetron constructed in accordance with my in-;

shown), the .end conductors 9 and ill of which project from-opposite ends of the cathode 6. one. of the said conductors, the conductor ill. for: example, may be connected to. said outer ,con-

ductive sleeve! whereas the other conductor 9. is

insulated from said sleeve. Light conductive shields ll and 12 are preferably mounted at, the

outer ends Of. the cathode, sleeve 1 so. as to Dre-r vent electron beams. from being projected out-r wardly toward the end caps! and 3 f The cathode 6 is supported by apair of lead-in, conductors l3 and. I l connected respectively to the conductors 9 and Ill. The lead-in conductors l3 and ll. are sealed through glass seals l5 and. I B mounted respectively in the outer ends of conducting pipes 7 l1, and I8 which, in turn, are hermetically sealedthrough the wall of block I.

When a, tube as described above is placed be-. tween suitable, ma netic poles l9 and,.2ll,,,the cathode heater is. energized, and a suitable volt-- age is, impressed between the cathode and the. anode structure, oscillations will be generated, Each pair of alternate anode arms 5-together. with the portion of the block I therebetween con-L stitute a cavity resonator. Each cavity resonator.

contains a certain amount of capacitance be tween the arms 5 and also a certain amount of inductance. This capacity and inductance primarily d te mi the res nant eq e y of h cavity resonator and thus the frequency ofwthe oscillatio s generated. These oscillations may be led out of said device by a coupling loop 2| ex:- tending into one of the cavity resonators. One,

end of the coupling loop is connected to the inner,

end of the conducting pipe 22 which is hermeti cally sealed through the wall, of the block L. The other end of said coupling loop is connected to a, conductor 23 which extendsjthrough said pipe 22 and emerges through a glass seal 24 car ried Jay the outer end of said pipe 22. The conductor 23 together with an external cylinder pipe (not shown) connected to the pipe 22form a po axial conductor transmission line through which the oscillations may be led to a suitable utilization:

device.

In order to reinforce, the main frequency at which the device is intendedto oscillate and to suppress spurious oscillations, each alternate; anode arm 5 is connected at one end thereof by' a conducting strap 25'.

intervening alternate anode arms are connected by a similar strap 26'. This insures that thevolt' By the term strap" I intend to include an elongated conductor of any" cross-sectional shape, here shown as rectangular. At the same end of the anode structure, the

ages at the alternate anode arms are maintained in phase with each other. In order to avoid spurious oscillations due to voltage differences arising because of the length of the anode arms along the axis of the tube, those anode arms which are interconnected by the strap are similarly interconnected by a strap ZI at the lower ends of said arms, while those anode arms which are interconnected by the strap 26 are similarly interconnected by a strap 28. It will be noted that a capacity exists between the straps 25 and 26 and likewise between the-lstraps fl and 28. These capacities constitute apart of the capacity of each of thefresonant cav' iesas.'

described above. g Also sealed through the wall of the block I substantially equal to .one wave length will re- ,flect a relatively low-resistive impedance into the adjacent one end thereof is. aiconducting pipe 23 withinewliich is mounted a central conductor. v 38 so as to form a concentric transmission line therewith; The inner end of the conductor may be connected. to a conductor '3! -'of reduced diametenwhich, in turn, is connelct'ed'to one of the straps, for example, the strap'2 5f It will be noted that the s'trap 25' will have impressed thereon "the voltage conditions at the end of one; set of alternate anodefarins. fThef-"pipe 29.,v on the other hand, will have impressed upon it the voltage conditions of the anode blockj'l which will be substantially the voltage conditions existing at the back'of each cavity resonator. In this way, the oscillatin'g' voltage which is generatedv by the ube will be impressed on the'concentric transmission line 29-30. 'At theouter end of the conductor 30, there is mounted a hollow conductingcsleeve '32'preferably of nickel;

This sleeve is externally coated with therirnioi iic emiss'lvegoxides 33 whereby the sleeve 32 is enabled to function asathermionic cathode. Within thejsleeve' 32 is supported aheatingfilament 3,5 the outer ends 35 of which extend through a 7 an inductive impedance into the cavity resona- 7 tors of the magnetron. so

glass stem 36 sealed in the outer end of the pipe 29 .Thus, when the conductors 35 are connected to a suitable source of energy such .as a battery 31, the filament 34 raises the temperature, of, the sleeve 32 to, apoint at which the coating 33 emits electrons.

When oscillations are generated by the mag-Q netron, the oscillatory voltage will bepropagated through the concentric transmission line 23 7- 31].v When this voltage is of the =proper phas e .to' make the pipe 29. positive with respect to the conductor 30 at thesleeve 32 electrons will now fromthe sleeve 32 through the intervening space to the. pipe 29. This electronicv flow will tend.

to cause this portion, ofthe concentric transmission line to act as a low impedance termination and therefore the concentric transmission lin e..29 30 will act as a stub ,line terminated by a'low impedance end. I

.In order to introduce tuning variations I surround the sleeve 32 with a grid 38.. This. grid preferably consists of a winding of finewire supported on a conducting standard 39-.- The outer end of this standard is likewise sealed through; the stem 36 so as to providean external electrical connection to the grid, The .grid 38. In Fig. Zthe grid 38 is shown as having a variable pitchwinding, the pitch ;of the winding increasing asthe distancefrom the blockzl increases; Thus is of theso-called variable mu type.

as the grid 38 is made more negative with respect tothe sleeve 32, electronic flow will first be out 01f at the end closest to block I. of the grid becomes more negative, emission; W ll If the voltage jl ifconeentric transmission line terminated by a low impedance end and having a length v cavity resonators of the magnetron. Thus, if

the voltage on the grid 38 is set so that cut-off of the electronic flow occurs at the center of the coating 33, the concentric transmission line 29-30- will appear substantially as such a re-' sistive impedance. If however the voltage on the-grid 38- is made less negative, cut-off will occur closer to the block I and the effective length ofthestubline will be shortened. This will pro-- duce the result that the stub line will reflect On the other hand, if the voltage on the grid 38 is mademore negative, cut-off will occur further awayfrom the block I and the stub line will reflect a capacitative reactance into the cavity resonators. Thus merelyby varying the potential on the grid 38, varying amounts of either inductive or capacitative impedance maybe reflected into the cavity resonators. This will change the natural frequency at which these cavityresonatorstend to oscil-' late and thus the desired tuning of the magnetron will occur.

Any desired arrangement for introducing the necessary voltage variations on the grid 38 may be-utilized. This is shown diagrammatically in. Fig. 2 as-a batteryv Bl having a potentiometer 4.0

connected across it. The positive end of the battery isconnected to the pipe 29' while an adjustable tap 4| is'connected through a, currentlimiting resistance 62 to the grid standard '39;

By adjusting the tap 4|, the voltage on the grid .38 may be varied so as toproduce tuning. Of

course it is to be understood that the voltage vari ation on the grid may be produced by any desired means such, as, for example, a signal variation of any desired frequency. For example, frequency stabilization: may: be secured by making the voltage variation on the grid 38 responsive;

to the deviations of the frequency of theoscillations generated by the magnetron from a desired frequency. The grid 38 may take any one ofa. variety of forms as long as it shifts the cut-ofl value along the grid in response to voltage variations therein. For example, an alternative formof. grid .is shown in Fig. 4. In this arrangement, the gridturns are substantially uniform in pitch but gradually increase in diameter from one end to the other. Various other equivalent constructions whereby a grid having variable cut-off along its length maybe devised. 3

Instead of utilizing a single themnioniccathodealong which the electronic discharge cut-off may be varied, an alternative arrangement such as shown in Fig. 3 may be utilized; In this arrangement the same reference numerals are used where parts are identical with those shown in h mb9. m nt.o .12is 1. and Fiesta aerial:

43 and similarly carries a. short-coated section 46 of emissive oxides. The sleeves 42 and 45 may be heated by heating filaments 41 and 48, respectively, connected in series and mounted within said sleeves 42 and 45. The outer ends 49 and 500i the. heating filaments 41 and are sealed through the stem 35. A substantially unitormly wound grid surrounds the cathode sleeve 42 and a, similar grid 52 surrounds the cathode 45. These grids are mounted respectively on grid standards 53 and 54 which are likewise sealed through the stem 36.

1 In thislatter arrangement, if grid 5| is biased so as. to. permit electronic flow between the emitting section 43 and the pipe 29, the concentric line will be terminated substantially at the emitting section 43. If however, the grid 5| is biased to cut off the electronic flow and the grid 53 is biased. so as to permit electronic flow from the emitting section 46, the concentric line will be terminated substantially at said emitting section 45. A variation in the length of the termination of such a stub line through substantially a quarter .wave length will produce substantially a maximum of variation in the reactive impedance re flected by the stub line into the cavity resonators of the magnetron. Thus ifthe distance b between the emitting sections 43 and 46 is made substantiallyequal to a quarter wave length, substantially maximum tuning may be effected by shifting the emission from one cathode to the other. .Instead of having an abrupt shift of the terminus of the concentric line from one cathode to the other, such transfer is preferably made gradually and in this way tuningmay be accomplished, over the entire range afforded by the two. limits of theefiective termination of the concentric line. This is illustrated diagrammatically in Fig. 3 by the provision of two batteries B3 and 64, respectively having their positive terminals connected together and having two resistances 55 and 56 connected respectively across batteries 63 and 64, respectively. An adjustable tap 51 on the resistance 55 is connected to the grid standard 53 while an adjustable tap 58 on the resistance 56 is connected to the grid standard 54. The two taps 51 and 58 may be moved simultaneously by a common actuating member 59. This arrangement provides a potentiometer in which one grid is made progressively more negative while the other grid is made progressively less negative. In the extreme position of actuation of member 59, one of the grids will permit a full conduction while the other grid will cut off conduction. The other limit of ad- .lustment of the member 59 will reverse the conditions at the grids. Intermediate positions of adjustment will represent intermediate conditions of tuning. Here, likewise, it is to be understood that the variations in voltage on the grids 5| and 52 may be accomplished automatically in response to any desired variation.

Of course it is to be understood that this invention is not limited to the particular details as described above inasmuch as many equivalents will suggest themselves to those skilled in the art.

-What' is claimed is:

1.: An electrqmdischarge device comprising; a. cavity resonator, -means, adjacent thereto for exe citing said resonator to produce oscillationstherein, a. concentric transmission line coupled to said cavity resonator, said line comprising a hollow outer conductor enclosing a central cone ductor, an electron emissive section on said central conductor at a predetermined position removed from thepoint at which said line'is coupled to said resonator and means adjacent said emissive section for cutting ofi the electron flowfrom: said emissive section to said outer conductor at'variable points along the'length of said emissive section whereby the effective impedance of said line i as reflected into said cavity resonator is: varied;

2. An electron-discharge device comprising a cavity resonator, means adjacent thereto for exciting said resonator to produce oscillationstherein, a concentric transmission line coupled to said cavity resonator, said line comprising a hollow outer conductor enclosing a central. conductor, an electron emissive section on. said central conductor at a predetermined position removed from. the point atwhich said line is coupled. to said resonator and a control electrode adjacent said emissive section.

3. An electron-discharge device comprising a cavity resonator, means adjacent thereto for ex.- citing said .resonator to produce oscillations therein, a concentric transmission'line coupled to said cavity resonator, said line comprising a hollow outer conductor enclosing a central conductor, an-electron emissive section of substantial length onsaid centralconductor at a predetermined position removed ,from the point at which said line is coupled to said resonator and a control electrode adjacent said emissive section, said control electrode having a cut-off character istic which 'variesfrom one end of said emissive section to'the other end thereof, whereby the effective length of 'said emissive section capable of passing electrons to said outer conductor may be varied to vary the efiective impedance of said line as reflected into said cavity resonator.

4. An electron-discharge device comprising a cavity resonator, means adjacent thereto for exciting said resonator to produce oscillations therein, a concentric transmission line coupled to said cavity resonator, said line comprising a hollow outer conductor enclosing a central conductor, an electron emissive section of substantial length on said central conductor at a predetermined position removed from the point at which said line is coupled to said resonator, the length of said emissive section being approximately a quarter of the wave length of the average oscillations generated in said cavity resonator and a control electrode adjacent said emissive section, said control electrode having a cut-off characteristic which varies from one end of said emissive section to the other end thereof, whereby the effective length of said emissive section capable of passing electrons to said outer conductor may be varied to vary the effective impedance of said line as reflected into said cavity resonator.

5. An electron-discharge device comprising a cavity resonator, means adjacent thereto for exciting said resonator to produce oscillations therein, a concentric transmission line coupled to said cavity resonator, said line comprising a hollow outer conductor enclosing a central conductor, a pair of electron emissive sections on said central conductor spaced from each other conductor whereby the efiective impedance of said'line as reflected into is varied.

6. An electron-discharge device comprising a cavity resonator, means adjacent thereto for exciting said resonator to produce oscillations therein, a concentric transmission line coupled to'said cavity resonator, said line comprising a said cavity resonator hollow outer conductor enclosing a central con- I ductor, a pair of electron emissive sections on said central conductor spaced from each other and from the point at which said line is coupled to said cavity resonator and means adjacent said emissive sections for regulating the electron flow from each of said emissive sections to said outer conductor in opposite directions whereby the effective impedance of said line as reflected into said cavity resonatoris varied.

7. An electron discharge device comprising a cavity resonator, means adjacent thereto for exciting said resonator to produce oscillations therein, a concentric transmission line coupled to said cavity resonator, said line comprising a hollow outer conductor enclosing a central conductor, apair of electron emissive sections onsaid central conductor spaced from each other and from the point at which said line is coupled to said cavity resonator and a control electrode adjacent each of said emissive sections for regulating the electron flow from each of said emissive sections to said outer conductor whereby the efiective impedance of said line as reflected into said cavity resonator is varied.

8. A magnetron comprising a hollow conducting member, a cathode centrally located therein, a plurality of spaced radial arms extending inwardly from said hollow member and terminating adjacent said cathode, alternate anode'arms being connected together by. a conducting strap adjacent one end of said arms, a concentric transmission line comprising a hollow outer conductor enclosing a central conductor, said central con ductor being connected to said strap, said outer conductor being connected to said hollow conducting member, an electron emissive section on said central conductorat a predetermined position removed from the point at which said central conductor is connected to said strap and means adjacent said emissive section for regulating the electron flow from said emissive section, to said outer conductor.

9. .A magnetron comprising a hollow conducting member, a cathode centrally located therein, a plurality of spaced radial anode arms extend-' ing inwardly from said hollow conducting member and terminating adjacent said cathode, alter.- nate anode arms being connected together by a conducting strap adjacent one end of said arms, a concentric transmission line comprising a hollow outer conductor enclosing a central conductor, said central conductor. being connected to said strap, said outer conductor being connected to said hollow conducting member, a pair of elec-' tron emissive sections on said central conductor spaced from each other and from the point at which said central conductor is coupled to said strap and means adjacent said emissive sections for regulating the electron flow from each of said emissive sections to said outer conductor.

PERCY L. SPENCER. I

REFERENCES CITED The following referen ces are of record in the file of this patent:

UNITED STATES PATENTS Certificate of Correction Patent No. 2,477,317 July 26, 1949 PERCY L. SPENCER It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Oolu nn 1gl life 11, for the Words in inertia read no inertia; column 5, line 7, for thus rea t is;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case 1n the Patent Office.

Signed and sealed this 13th day of December, A. D. 1949.

THOMAS F. MURPHY,

Assistant Uommz'ssioner of Patents.

Images