US2413385A

US2413385A - Electron discharge device of the magnetron type

Info

Publication number: US2413385A
Application number: US584364A
Authority: US
Inventors: Robert C Schmidt
Original assignee: Raytheon Manufacturing Co
Current assignee: Raytheon Co
Priority date: 1945-03-23
Filing date: 1945-03-23
Publication date: 1946-12-31
Anticipated expiration: 1963-12-31

Description

Dec. 31, 1946. R. c. SCHMIDT ELECTRON DISGH'KRGE DEVICE OF THE MAGNETRON TYPE 2 Sheets-Sheet 2 Filed March 23, 1945 //l/L A/7'0/?. lioamr 65 50/0110:

Patented Dec. 31, 1946 UNITED STATES PATENT OFFICE ELECTRON DISCHARGE DEVICE OF THE MAGNETRON TYPE Claims. 1

This invention relates to electron-discharge devices, such as magnetrons, for example, and more particularly to tuning means for such devices.

One of the objects of the present invention is to provide novel and eilicient means for varying the frequency of the oscillations generated by the device.

Another object of the present invention is to provide novel and reliable electronic tuning means for such a device.

These objects and such other aims and objects of the present invention as may hereinafter apffit pear will be best understood from the following description taken in connection with the accompanying drawings of embodiments of the invention herein presented for illustrative purposes.

In the drawings Fig. 1 is a vertical section taken substantially through the center of an electron-discharge device comprising one illustrative embodiment of the invention;

Fig. 2 is a section on line 2-2 of Fig. 1 showing a top plan view of a concentric line through which oscillations are led out of the device and of a stub line comprising the tuning means, certain parts being broken away to show the interior construction; and

Fig. 3 is a sectional elevation of another illustrative embodiment of the tuning means.

In the drawings the invention is illustratively shown in its application to an electron-discharge device of the magnetron type, comprising an envelope including a cylinder 2 closed at its ends by caps I and B, respectively, said caps being soldered to the ends of said cylinder 2 to form an hermetically sealed enclosure. Said cylinder 2 and caps I and i may be made of copper or other suitable electrically conductive material. A central annular projection B is formed upon the inner surface of said cylinder, to which are soldered a plurality of suitably spaced, radiallydisposed plates or arms l0. Said arms In, cylinder 2 and caps 4 and 6 constitute the anode structure of the device, and the inner ends of said arms ill form anode faces for receiving electrons from a cathode l2 supported centrally of said anode faces. Said plates may conveniently be stamped from a plate of highly conductive copper.

Said cathode I2 is preferably of the indirectlyheated. thermionic type provided with an outer electrically conductive sleeve l4 coated with electron-emissive oxides or other electron-emissive material. It contains a heater-wire of conventional construction, not shown, of which the end conductors l8 and I8 project centrally from the opposite end of the cathode. One of said conductors, the conductor ID, for example, may be connected to said outer conductive cathode sleeve ll, the other conductor It being insulated from said sleeve. The cathode I2 is preferably supported by a cathode and heater-wire lead-in conductor 20, welded to the end of said conductor ii. A second lead-in conductor 22 has its inner end welded to the free end of said conductor l8. Said lead-in conductors 20 and 22, are connected to a suitable source of voltage, not shown, and are sealed in well-known conventional manner through glass seals 24 and 26 at the outer ends of conductive pipes 28 and 30. (See Fig. 1.) Light conductive shields 32, 34, herein conveniently integral with said cathode sleeve II, are provided at opposite ends of the latter to prevent electron beams from being projected outwardly toward said end caps l and 6.

If such a device he placed between suitable pole pieces 38 and 38 to produce a longitudinal magnetic field within the device and said device be energized, oscillations will be generated which may be led out of the device by a coupling loop Ill (see Fig. 2), extending into the space between two of said anode arms lli. One end of said coupling loop I is connected to the inner end of a conductive pipe 42 hermetically sealed through the wall of said cylinder 2, substantially midway between the endsof the latter, and its other end is connected to a conductor 44 which extends through said pipe 42 and is sealed through a glass seal 46 mounted at the outer end of said pipe 42.

Each pair of anode arms It forms with the portion of the projection 8 between them an oscillating cavity or cavity resonator. A capacitance exists between the cathode I2 and the end faces of said anode arms l0 and also between the side walls of each resonator cavity 48. The conductive path around each cavity is afforded by the side walls thereof and the portion of said pro- ,iection 8 between them, constitutes an inductonce. The anode structure is therefore so designed and spaced relatively to the cathode that said inductances and capacitances constitute tuned circuits. It is desired that these circuits shall be resonant at a definite, predetermined frequency at which the device is to operate.

I shall now describe one illustrative embodiment of means in accordance with my invention for varying the frequency of the oscillations generated by the device. A coupling loop 50 extends into one of the cavity resonators 48. One end of said loop is connected to the inner end of an outer tubular conductor 52 having a reduced end auasea 3 sealed through the wall of the envelope, and the outer end of said loop is connected to the inner end 01' a conductor I extending axially of said tubular member. The conductor together with members capacitatively coupled thereto and forming a high frequency extension of said conductor 58, as described below, constitute with the tubular member 52, a coaxial line. The outer section El of the central conductor of the coaxial line is sealed through a glass seal 51 carried in said tubular member 52. Said coaxial line is closed on by 9. Partition 68 at its outer end, so that it forms a stub line. Said central conductor has incorporated therein electron-emissive means, said means herein consisting of two tubular cathodes comprising conductive sleeves 80 and 82. The sleeve 82 is insulated from the end of conductor 50 and from a central hollow conductor 85 by insulating rings 84 of glass or other suitable insulating material. The sleeve 62 is also insulated from the conductors 65 and 5| by similar rings 84. The capacities which exist through the rings 84 form low impedances for the high frequency currents and thus cause the members 56, 62, 65, B0 and Ii to act as the center conductor of the coaxial line. The outer surface of each cathode sleeve may be provided with a coating 58 of electron-emissive material, such as the oxides of alkaline-earth metals. Preferably said coating will be in the form of a band encircling each of said sleeves Bil, 62. Herein, the cathodes are of the indirectlyheated. thermionic type, heaters 88 and I0 being connected in series by conductor l2 and I4 with a battery 16. Energy is supplied to the two cathodes from a potential divider 18, one negative pole of which being connected to said cathode sleeve 52 by conductor 82 through a resistance 88, the other negative pole being connected to said cathode sleeve 60 by conductor 84, through resistance 88, the positive poles being connected by conductor 90 to said tubular conductor 52 acting as an anode. Contacts 92 and 94 engage resistances 86 and 88. respectively, and serve to vary the voltage as will be hereinafter more fully explained.

The coaxial line described above constitutes a reactance coupled to the oscillating circuit of the electron-discharge device by said coupling loop 50. Herein, when the cathode sleeves ill and B2 are energized, the maximum length of said coaxial line terminates at a: (see Fig. 2) and the minimum length terminates at 1/, the distance d between the points a: and 1/ being equal to that is to say, to one-quarter of a 'wave length when n is equal to one.

In accordance with my understanding of the operation of my invention, the oscillations generated in the device generate a standing wave in the tubular conductor 52 and a reactive impedance is reflected back into the tube which may be either inductive or capacitive, dependent upon the length of the conductive line, and it is by varying the magnitude of the inductive or capacitive impedance by varying the length of the coaxial line, that the tuning of the device is effected.

When voltage is impressed upon the cathode Gil, an electron flow will radiate outwardly from the electron-emissive coating 88 encircling said cathode to the inner wall of said tubular conductor 52. Similarly when voltage is impressed upon the cathode 62. an electron flow will radiate from the latters electron-emissive surface ll across to the surrounding inner wall of the tubular member conductor 52. Such an electron flow constitutes a relatively low impedance which blocks the progress of the oscillations along said tubular conductor and thus limits the length of the concentric conductive line.

Referring more particularly to Fig. 2, means are therein diagrammatically illustrated for moving the contacts 82 and 94 alOl'ig the resistances 88 and 88, respectively, said means herein illustratively comprising a handle 98 on an insulating bar ill attached to the two conductors 82 and 84. Assuming that the contacts 92 and 84 are at the extreme left end (viewing Fig. 2) of their respective resistances 8i and 88, if said bar 88 be moved to the right (viewing Fig. 2), more and more of the resistance 88 will be cut out of the energizing circuit of the cathode 60 and more and more of the resistance 85 'will be thrown into the energizing circuit of the cathode B2. The electron flow from the cathode B0 to the tubular conductor 52 will thus gradually increase while the electron flow from the cathode 62 to said tubular conductor will gradually decrease, until, when the contact 98 reaches the right end of resistance 86 (view Fig. 2), and the contact 94 reaches the right end of the resistance 88. the electron flow from the cathode 60 will be at its maximum and the electron flow from the cathode 62 will be at its minimum. Displacement of said contacts 92 and 94 from the right ends respectively to the left ends of said resistances 86 and 88 respectively will gradually decrease the electron flow from the cathode 60 from its maximum to its minimum and gradually increase the electron flow from the cathode 62 from its minimum to its maximum. It is my present understanding of the operation of my invention that as. by the adjustment of said contacts 92 and 8| the electron emission from one cathode is caused to predominate more and more over the electron emission from the other cathode, the coaxial line is lengthened or shortened according as the adjustment is such as to cause the predominating electron emission to come from the cathode ill or from the cathode 62. It will thus be seen that the adjustment described furnishes an eilective and simple means for shifting the location of the terminating impedance produced by the electron flow from the line a: to the line 11 and vice versa, thus to vary the length of the coaxial line and correspondingly to vary the frequencies of the oscillations generated by the device throughout the adjustment range of said coaxial line.

In the illustrative embodiment of the invention shown in Fig. 3, a tubular conductor iflll is hermetically secured in the wall I02 of a magnetron which may and preferably will'be identical with the one illustrated in Figs. 1 and 2. A central conductor IIM extends axially of said tubular conductor Ill and an extension I 05 thereof is sealed through a glass seal "l6 closing the other end of said tubular conductor. The other end oi said conductor IM terminates in a. loop I08 located in one of the cavity resonators I III of said magnetron, the free end of said loop I" being connected to the inner end of said tubular conductor Hill, said conductor Hi4, its extensions and said tubular conductor lllil forming a concentric line. A cathode H2 is mounted on said central conductor I as an extension thereof and is insulated therefrom and from the hollow conductor III! by insulating rings I I3. Here likewise the capacities through the rings III cause the members Ill, 2 and III! to act as the central conductor of a coaxial line. Said cathode is preferably of the indirectly-heated, thermionic type provided with an outer, electrically conductive sleeve Ill coated with electron-emissive oxides or other suitable electron-emisslve material, preferably in the form of a band lit encircling said sleeve Ill. A heater coil III is contained within said cathode 2, one end of said coil being connected by a conductor I20 with one pole of a battery I22. the other end of said coil being connected by a conductor I24 with the other pole of said battery- Said conductors I20 and I24 are hermetically sealed through an insulating button I28 of glass forming the outer end wall of said central conductor I05. Said cathode is energized by a battery I28 or other suitable source of energy. The positive pole of said battery is connected by a conductor Ilil to the wall of said tubular conductor ltlil. The battery has connected across it a potentiometer I32. An adiustable contact I on said potentiometer is connected to the inner wall of said cathode M2 by a conductor I36 sealed through said insulating button I26. Said tubular conductor I00 and the inner assembly of the coaxial line are closed oil by a partition I38 at the outer end so as to form a stub line. The maximum length of said coaxial line terminates at a: and the minimum length terminates at u, the distance d between the points a: and 1! being equal to which is one-quarter of a wave length when n is equal to one. Said coaxial line constitutes a reactance coupled to the oscillatory circuit of the electron-discharge device by said coupling loop I08.

Referring to Fig. 3, it will be apparent that movement of the adjustable contact ill to the right in said Fig. 3 will gradually increase the electron flow from the cathode to said tubular conductor 52 while movement oi. said contact along said resistance in the opposite direction will gradually decrease the flow of electrons from said cathode to said tubular conductor 52. These changes in the magnitude of the electron flow T vary the reflected inductive or capacitive impedance in the tubular conductor I00 and thus either increase or decrease the length of the coaxial line according as said electron flow is increased or decreased. This, in turn, through said coupling loop I08 produces corresponding changes in the frequencies of the device.

I am aware that the present invention can be embodied in other specific forms without departing from the spirit or essential attributes thereof, and I therefore desire the present description 20 be considered in all respects as illustrative and lot restrictive, reference being had to the appended claims rather than to the aforesaid description to indicate the scope of the invention.

What is claimed is:

l. tn electron-discharge device comprising a cathode, an anode structure spaced from said cathode and incorporating a cavity resonator, a tubular conductor, a second conductor extending axially through said tubular conductor and constituting a coaxial line therewith, said coaxial line being coupled to said cavity resonator, electron-emissive means connected to said second conductor through means having a low impedance to high frequency currents, and means connected intermediate said electron-emissive means 6 and said tubular conductor for impressing a voltage therebetween, whereby said coaxial line may be effectively terminated at said electron-emissive means.

2. An electron-discharge device comprising a cathode, an anode structure spaced from said cathode and incorporating a cavity resonator. a tubular conductor, a second conductor extending axially through said tubular conductor and constituting a coaxial line therewith, said coaxial line being coupled to said cavity resonator, electron-emissive means mounted in said second conductor and connected thereto through means having a low impedance to high frequency currents, and means connected intermediate said electron-emissive means and said tubular condoctor for impressing a voltage therebetween, whereby said coaxial line may be eilectiveiy terminated at said electron-emissive means.

3. An electron-discharge device comprising a cathode, an anode structure spaced from said cathode and incorporating a cavity resonator, a tubular conductor, a second conductor extending axially through said tubular conductor and constituting a coaxial line therewith, said coaxial line being coupled to said cavity resonator, and electron-emissive means mounted in said second conductor and connected thereto through means having a low impedance to high frequency currents, and means connected intermediate said electron-emissive means and said tubular conductor for impressing a variable voltage therebetween, whereby said coaxial line may be eilectively terminated at said electron-emissive means.

4. An electron-discharge device comprising a cathode, an anode structure spaced from said cathode and incorporating a cavity resonator, a tubular conductor, a second conductor extending axially through said tubular conductor and constituting a coaxial line therewith, said coaxial line being coupled to one end of a loop in said cavity resonator, the other end of said loop being connected to said anode structure, electron-emissive means connected to said second conductor through means having a low impedance to high frequency currents, and means connected intermediate said electron-emissive means and said tubular conductor for impressing a voltage therebetween, whereby said coaxial line may be effectively terminated at said electron-emissive means.

5. An electron-discharge device comprising a cathode, an anode structure spaced from said cathode and incorporating a cavity resonator. a tubular conductor, a second conductor extending axially through said tubular conductor and constituting a coaxial line therewith, said coaxial line being coupled to said cavity resonator, two cathodes spaced longitudinally of said conductor and connected thereto through means having a low impedance to high frequency currents, and means intermediate said two cathodes, respectively, and said tubular conductors for impressing a variable voltage therebetween, connected whereby said coaxial line may be efiectively terminated at either cathode.

6. An electron-discharge device comprising a cathode, an anode structure spaced from said cathode and incorporating a cavity resonator, a tubular conductor, a second conductor extending axially through said tubular conductor and constituting therewith a coaxial line coupled to said cavity resonator, electron-emissive means connected to said second conductor through means having a low impedance to high frequency currents, means connected intermediate said electron-emissive means and said tubular conductor for impressing a voltage therebetween to create an impedance across said coaxial line, and including means for varying the eiiectlve position of said impedance lengthwise of said tubular conductor to vary the length of said coaxial line and the frequencies of said device.

7. An electron-discharge device comprising a cathode, an anode structure spaced from said cathode and incorporating a cavity resonator, a tubular conductor, a second conductor extending axially through said tubular conductor, said tubular conductor and said second conductor constituting a coaxial line coupled to said cavity resonator, a cathode connected to said second conductor through means having a low impedance to high frequency currents, means connected intermediate said eiectron-emissive means and said tubular conductor for impressing a voltage therebetween to create an impedance across said coaxial line, and including means for varying the voltage impressed between said cathode and said tubular conductor to vary the efl'ective position of said impedance lengthwise of said tubular conductor to vary the length of said coaxial line and the frequency 01' the device.

8. An electron-discharge device comprising a cathode, an anode structure spaced from said cathode and incorporating a cavity resonator, a tubular conductor, a second conductor extending axially through said tubular conductor, said tubular conductor and said second conductor constituting a coaxial line coupled to said cavity resonator, two cathodes connected to said second conductor through means having a low impedance to high frequency currents, means connected intermediate said cathodes and said tubular conductor for impressing a voltage therebetween to create an impedance across said coaxial 8 line, and including means for varying relativeli to each other the voltages impressed between sak two cathodes respectively and said tubular conductor to vary the eil'ective position of said impedance lengthwise oi said tubular conductor and the frequency of the device.

9. An electron-discharge device comprising a cathode, an anode structure spaced from said cathode and incorporating a cavity resonator, s tubular conductor, a second conductor extending axially through said tubular conductor, said tubular conductor and said second conductor constituting a coaxial conductive line coupled to said cavity resonator, a cathode mounted in said second conductor and connected thereto through means having a low impedance to high frequency currents, means connected intermediate said cathode and said tubular conductor for impressing a voltage therebetween to create an impedance across said coaxial line. and including means for varying the voltage impressed between said cathode and said tubular conductor to vary the eitectiv position of said impedance and the frequency of the device.

10. An electron-discharge device comprising a cathode, an anode structure spaced from said cathode and incorporating a, cavity resonator, a transmission line, including a pair of conductors, coupled to said cavity resonator, one of said conductors being provided with an electron-emissive portion, and means, connected intermediate said electron-emissive portion and the other of said conductors, for impressing a voltage therebetween, whereby a flow of electrons may be instituted between said electron-emissive portion and said last-named conductor to short circuit said transmission line.

ROBERT C. SCHMIDT.

Certificate of Correction Patent No. 2,413,385.

December 31, 1946.

ROBERT C. SCHMIDT It is hereby certified that errors appear in the numbered patent requiring correction as follows:

grinted specification of the above olumn 6, line 61, claim 5, after the word "means insert connected; line 63, strike out connected; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 25th day of March, A. D. 1947.

LESLIE FRAZER,

First Assistant Omission of Patents.