US2110449A

US2110449A - Magnetron modulator

Info

Publication number: US2110449A
Application number: US61679A
Authority: US
Inventors: Ernest G Linder
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1936-01-31
Filing date: 1936-01-31
Publication date: 1938-03-08
Anticipated expiration: 1955-03-08

Description

March 8, 1938.

E. G. LINDER MAGNETRON MODULATOR Filed Jan. 51; less 3 Sheets-Shee't 1 Filed Jan. 31, 1936 3 Sheets-Sheet 5 Patented Mar. 8, 1938 UNITED STATES MAGNETRON MODULATOR PATENT OFFICE REISSU'ED Ernest G. Linder, Philadelphia, Pa., assignor to Radio Corporation of America, a corporation of Delaware 7 Claims.

My invention relates to a magnetron modulator. More particularly, my invention relates to the modulation of magnetrons by moving the anode with respect to the cathode, or by moving both electrodes with respect to the permanent magnetic field of the magnetron.

A magnetron is a thermionic tube including one or more anodes, a cathode, and a magnetic field. The lines of force of the field are substantially 10 parallel to the cathode. The electrons from the cathode follow a curved path 2 which may be illustrated by Figure IA. The curved or circular path is due to the forces exerted on the electrons by the magnetic field, the anodes 5, l, and the cathode 3.

In contrast to the magnetron, an ordinary triode has a cathode, grid and anode. No magnetic field is required. The electrons travelin a substantially straight line from the cathode to the anode. The number of electrons which reach the anode is normally determined by the spacing of the electrodes, and the relative grid, anode and cathode potentials.

I am aware of ordinary electron tubes in which the electrodes have been relatively movable. The movement of electrodes in such tubes has slightly varied the number of electrons reaching the anode, or the amplification factor if a triode is used. In the case of a diode or triode relatively small movement of the electrodes will have a secondary effect on tube operation.

The operation of a magnetron is especially suited to modulation by relative movement of electrodes or of electrodes with respect to the magnetic field. Since the magnetron is used at ultrahigh frequencies, the capacity between the anodes is of primary importance. Aslight relative movement will have a very large effect on the operating frequency; Furthermore, [the circular path of the electrons makes it possible to completely stop the flow of electrons to one anode and to greatly increase the electron flow to the other.

Since the electron path is dependent upon the lines of force of the permanent magnetic field, the operation of the magnetron will be greatly affected by a slight relative movement of the electrodes with respect to the field. By way of example, the effect of moving the anodes with respect to the cathode is illustrated in Fig. IB and Fig. IC. Other types of relative movement will produce large changes in anode current. These changes are due to the characteristic magnetron operation.

One of the objects of my invention is to modu- MAY 2 1 late a magnetron by changing the relative spacing of the cathode and anode electrodes.

Another object is to modulate a magnetron by moving the cathode and anode electrodes with respect to the magnetic field. 5

Another object is to change the relative spacing of the magnetron electrodes by means of a sound operated diaphragm.

Another object is to vary the operating frequency of a magnetron by moving its electrodes 10 in a non-uniform field.

A further object is to operate a single magnetron as an oscillator, modulator and 'microphone.

A still further object is to vary the frequency 15 of a magnetron oscillator by varying the interelectrode capacitance; a

An additional object is to provide means whereby a magnetron may be made to generate audio frequency currents. 20.

Reference is made to the accompanying drawings in which Figure IA, FigureIB, and Figure IC are illustrative of the operation of a magnetron embodying my invention,

Figure II is a schematic diagram of a mag- 25 netron oscillator including modulation means,

Figure III is an illustration of a magnetron modulated by a sound actuated diaphragm,

Figure IV is a schematic diagram of a modification of Figure I, 30

Figure V is a schematic diagram of a-magnetron in which the anodes are moved with respect to cathode for frequency modulation,

Figure VI is a schematic diagram of a magnetron in which the tube and electrodes are 35 moved with respect to a magnetic field of nonuniform characteristics.

Figure VIa. represents the anodes and the electro-magnet for producing the non-uniform field of Figure VI, 40

Figure VIb is a plan view of the tube moving means shown in elevation in Figure VI.

Figure We is a, plan view of the pivotal mounting'and biasing spring shown in elevation in Figure VI. 45

Figure VII is a schematic diagram of a magnetron similar to Figure VI in which the tube moving means is a sound actuated diaphragm,

and

Figure VIII is a modification of the apparatus 50 of Figure VII. 1

Throughout this specification similar reference numerals will be used to designate similar parts. In Figure II within an evacuated glass envelope l are mounted a cathode 3 and apair of anodes 55 7 line which may be, connected to a dipole antenna I the armature 3|. v magnet is serially connected towalocal battery. a r

Theianodesare connected to a pair of lead wires ll, l3. A conductor 151 connects the lead wires. This conductor and the

anodes

5, 1 .form a resonant circuit. 1 V

, The lead wires 1 I, [3 may form atransmission or the like; The negative terminal .OI-an anode batteryl] is connected to'tlie cathode 3.; The positive terminal of the anode battery is connected to a bridging conductor I9 which is suitably located on the leads ll,'l3.

A U-shape magnetic core 2| is energized byia' core 23' and abattery Suitable jaws (not g microphone. Instead of modulating. the magshown) are attached to: the pole' pieces'gofythe core 2l to clamp the envelope" I; The magnetic lines offorce between the pole. pieces surround 'and are substantially, parallel to the? cathode 3.

The arrangement thus far described may beoperated as a magnetron oscillator. f I -A series of corrugations-11am formed in the section of the envelope adjacent the. leadin 'of.

.tlietransmissionwiresill, l3. .A.connecting link 19 is fixed: to the'. end of, the envelope adjacent the corrugations 21; TA"m'agnetic. armature 3l' is fastened to the endiof the link-.29.. Anele'ct'romagnet 33 is suitablypositioned with respect 'to Thewinding ofthe electro- 35 -and a-microphone 31. J

The corrugations 21 offer;suflicient'iieiribility to the "envelope: I.: to permit movement of the corrugated end of- 'the envelope. with respect to the portion'clamped by the jaws attached to. the

magnetic core 2|; .A slight movement of -.the corrugated en'dwhichalso supportstheleadwires ll, l3. causes a substa ntial'.mdvement..ofI'the anodes 5, I. with-respect to the cathode]; This movement results =.in.:a change. of electron dis-- tribution-represented by Figs.- IB toIC. This I spect'to each other will. s'ubstantlally varytheir change-.will modulate the normalielectronflow.

. .aWhile. Iihayeiillustrated the.electromagnet. 33,

Q 'and microphone 3-'| -as' a convenient 1 means'of flexing'the tube to efiectmodul'ation, itl fs'hould be understood thatfother. meansxmay be-employed.= For example,,a 'sound; actuated: dia.-'

1 Dhr'agm,. a mechanicalr'noveinent for'telegraphic' signalling, orainpllflers may beusedi m :Fig. III, the circuit:.is. representative ,of a

but of. the device.-

magnetron 1 microphone amplifier; In this de.-

' vice the 'magnetronoperates; asia microphone. and also .as' an amplifier; although .amplifica? tion'is not essential; The leads. I I.,. I3 are 'con.-' nected to-the primary 39: of. the pushepullti ans formerv 3|. The anode battery llxis conneeted' to the center tap. ofathe'primary- 39; 1 Theisec: ondary 43 of the transformerrirepresents the-but :-.n1 place ofthe s atement motor .dri-iagure II, a sound operated diaphragm. hasib'een connected to :theLlink H-a .A' movemeht :of; :the'

diaphragm lis transmitted throughthe link 29 to. l

the. flexible end of the envelope; ,Thernove- Y a ment ofJthei-en'velope inLturn varies the relative:

position of anodes and cathode; 'I'his'alter's" the electron distribution andnence: the'current flow through..the':primary'39..1Q

i-A modificationof; Eigure II is. mamas FigureIV. This modification'consists primarily free end of the metal envelope includes a glass insert '49 through which cathode. leads may be brought. a

In this modification, the cathode is moved with respect-to the anode electrodes 5, 'l. The electro-magnetic motor device represented by armature 3I and magnet. 33 has been connected.

. II may beused in place of the links and lever.

Likewisethe diaphragm 45 of Figure III may be "substituted for the electromagnetic motor.

The schematic circuit of Figure IV represents" a combined magnetron oscillator, amplifier, and

netroncscinamr the connection of this figure may be arranged'similar to Figure III with a reentirely: rigid- "Instead of flexing theenvelope,

armatures 6|, were fastened'to the lead wires- II. I3," by forces, generated by the.e1ectromagnets'85 ,fl.

The armatures are attracted or repelled Various movements .of the anodes may be obtained by 'proper'phasing. of the exciting. curre'nts.- The-spaces between the armatures SI; 63 and the walls of the envelope are sufllcient to permit.free' movement of. the V armatures. The bridging conductor '59; which :may :be employed in 'ja magnetr'o'n oscillator, has sufllcient length andlflexibility to permit movement of the" lead wires-J3. 1

Sincethe. anodes 5, I are'attached' to the lead wires, they may be moved-with respect to each other.,: or with respect -to the: cathode 3; If the magnetron isoscillatingas a negative resistance device, theoscillatory frequency is'inversely pro portional to the capacity between the anodesf therefore, the movements of the anodes with recapacities. and'the oscillatory frequency. Ifthe magnetron is oscillating as an electronic oscillator. variations in relative. anode spacing will vary theamplitude'of oscillations Thus,the magnetron oscillator of' Figure V may be .frequency modulated by imprssingcurrent's 01 the magnets 65, 61. j

The: arrangement: 615.:Figur'e V may ployed as Imicrophone-amplifler instead of' an oscillator. As an amplifier, the bridgingconductormaybe omitted. Inboth cases, the'magnetic -fie1d is used. The electro magnet structure- 2|,

23,;25 :of Figure II.is,suitable for thistpurpose.

. .A. U :shapezpermanent magnet m'ay-be s d a; s how'n-in;Fi'g.lV.. g

desired modulation -frequency on the electro- 2 piste /dot. using hea ngemem of'Figure it as 'a microphone-amplifier combination, this device may. be ,used toi'generateaudio frequency currents. Inthe generationof audio. frequency currentsijthe. microphone *31 1 isl omitted. A

portion of the output currents, in the 'proper' phase, is fed; back ;to' the ;exciting" .magnets 35,

SLThe feedback currents may :be; amplified "by aetriodeor the. like. The frequency of the V audioicurrents can be controlledby'adjusting the i natural frequehcy of vibration. of the anodes 3,-

1 ,'ar matures BI, .63 and lead wires H, l3.

Figure VI. represents, a. magnetron oscillator jor amplifier.whichisxmoVediB-S a whole by the modulationjmeans'; Theanode and cathode el'ectoryfcurrenta-onthe-amplification. depends upon -trodes;. are-.moved through a'non uniform magnetieflfleld. Since'the frequency of the oscilla the magnetic field strength, modulation will be effected by the relatively varying field. This arrangement is best adapted to the electronic mode of oscillation. r

In Figure VI, the envelope I is suitably fastened to a pivot member 'II. The pivot member II is pivotally supported by a yoke member I3. One or more biasing springs I are connected between fixed studs 11 on the yoke I3 and the pivot member to yieldably position the tube. These biasing springs may be helical in form similar to the hair spring on a watch.

The electro-magnetic system of this figure differs from the preceding figures. In the preceding figures, the pole pieces of the core 2| were of normal uniform shape and produced a substantially uniform field. The pole pieces I9 for this embodiment of my invention are illustrated in Figure VIII. The effect of the slanting pole pieces 19 is to produce a more dense magnetic field between the near points and less dense between the more widely spaced points. Movement of the anodes 5, I and cathode 3 in the non-uniform field will be equivalent to varying the field. This variation modulates the anode current or varies the frequency of oscillation.

In place of slanting pole pieces, various shape pole pieces may be used. .For example, a V or inverted V-shape pole piece or a conical shape will have the required non-uniform field. Where the field has a rate of variation which is uniform with respect to movements on either side of the cathode, push-pull modulation may be produced. 1

The non-uniform field may be used for purposes other than modulation. For example, a permanent magnet may be substituted for the electrical one and the operating frequency of the magnetron varied by moving the magnet with respect to cathode and anode. Such a system lends itself toportability and simplicity of frequency adjustments.

One means for moving the magnetron of Figure VI is illustrated as an electro-magnetic driver 8I. The driver is shown in plan view in Figure VI and in elevational view in Figure VIb. A pair of arms 83 are rigidly secured to the envelope I. A magnetic armature 85 is secured to the ends of these arms by soldering, welding or the like.

The biasing springs 15 normally position the armature 85 in the center of the air gap of a magnetic core 81. The air gap is of sufiicient width to permit the armature to freely oscillate within the gap when the magnet is energized. The energizing means includes the field coil 89, battery 9| and microphone 93. Amplifiers and lever actions may be employed in place of the direct drive shown.

A modification of Figure VI is illustrated in Figure VII. The essential difference between the apparatus of Figure VI and Figure VII is that the latter has a sound actuated diaphragm 95 to-actuate the magnetron with respect to the non-uniform field. This field is produced by a magnet which has slanting pole pieces I9 similar to those shown in Figure We.

The diaphragm 95 may be a cone of suitable size. A flexible strip 9! of leather or cloth connects the cone to a rigid supporting ring 99. The center of the cone is connected to the movable end of the magnetron by a link IOI. Sound impressed on the diaphragm actuates the magnetron which is pivotally mounted as previously described. This combination may be used as a microphone, microphone-amplifier, or oscillator, modulator and microphone.

In the embodiment of my invention shown in Figure VIII, the magnetron is mounted so that it may be rocked about the axis ofenvelope I. A pair of metal rings I03 are clamped at the ends of the envelope I. A pair of wires I05 are attached to each of the rings. These pairs of wires terminate in supports I01.

The pairs of wires and their connections act as a torsional balance. The suspended magnetron may be rocked about the axis of its envelope I. In this figure, the batteries and connecting' leads have been omitted. The magnetron may be connected and adjusted for generating, amplifying, oscillating, or modulating currents.

The means for rocking the tube may bev a diaphragm, motor, or the like. For purposes of illustration, a sound actuated diaphragm 95 is shown. The diaphragm 95 is coupled to the envelope I. by suitable links IUI, I09. The force applied through these links rotates the magnetron about the axis of envelope I. The field in the present instance is of the uniform type. Normally, the magnetic lines of force are substantially parallel to the cathode 3. As the magnetron is rocked back and forth, the relative angular relation between the electrodes, and the magnetic lines is varied. This variation alters the electron flow and thereby modulates the output.

Thus I have described, and illustrated several embodiments of my invention by means of which a magnetron may be used as a microphone, microphone-amplifier, modulated oscillator, a modulator, or audio frequency generator. Various elements of each of the several arrangements may be added to or substituted for elements of the other combinations. For example, a diaphragm may be substituted for the electromagnetic driving motors and vice versa.

I claim as my invention:

1. A magnetron including a cathode and anode electrodes, means for establishing a magnetic field whose lines of force surround and are substantially parallel to said cathode and means for moving one of said electrodes in relation to said magnetic field in accordance with desired signals.

2. A magnetron including a cathode electrode and a pair of anode electrodes, means for maintaining a magnetic field whose lines of force surround and are substantially parallel to said cathode and means for moving said cathode electrode with respect to said anode electrodes in accordance with desired signals.

3. A magnetron including a cathode electrode and spaced from said electrode a, pair of anode electrodes, means for creating a magnetic field whose lines of force surround and are substantially parallel to said cathode and an electromagneticmotor for varying the orientation of said electrodes by relative motion of said electrodes.

4. A magnetron including a cathode electrode and spaced from said electrode a pair of anode electrodes, means for establishing a magnetic field whose lines of force surround and are substantially parallel to said cathode, and means for moving said electrodes with respect to said field for varying the operational characteristics of said magnetron at a desired rate.

5. A magnetron including an evacuated envelope having a rigid section and a flexible a section an electron. emissivecathode electrode supported by one of said?sections; and agpair of anode electrodes supported by the othenof said sections; means .1 for-establishing a mag:

netic field to. thereby cause electrons emitted from said cathode ,to travelecurved paths to said anodes, and means for:flexingsaid'flexiblefsece Vtion sothat said cathodeand anodes-may-be moved relative; toeachptherto thereby vary the number of electrons traveling-between said cath ode-and anodes. 1

- 6. A magnetrondncludingjan evaeuated ien 'velope having a rigid section anda flexible metalliesection, an-electrorr emissivecathode elec- 15 r for establishing amagnetic field to thereby cause electrons emitted from said cathode to travel:

curved paths to said anoclles,- andl'a pair of anode. v

trode supported by one of said sections, means electrodesl supported-by. the other of saidse'ccathodeand-anqd V 7.- Aj'jmagnetron including an evacuated envelope having a rigid section rand-a flexible section, a'cathode electrode supported by: one I of said sections, and a pair of anode electrodes tions, jandrneans for flexing said metallic sec-V tl on sog -that said cathode and. anodes, may *moved relative to each, other to' thereby vary the. number of electrons traveling'jbetween said 7 supported by the :other of said sections,v .means' 7 for establishing a; magnetiefield' whose lines of force surround and are' substantially parallel to said" cathode, andlrmeans. for moving said flexible sectio'ni in accordance with desired signals so that at least one of said electrodes may be moved with respect tosaidmagnetiofield.

" o, ERNEST GJLINDER; V