USRE21458E - Magnetron modot - Google Patents

Description

May 21,v 1940. E Q UNDE f' Re. 21,458

MGNETRON MODULATOR Y I y Original Filed Jan. 51, 1956 3 Sheets-Sheet 1 Figi@ ffb. Fzgfe May 21, 1940. E. G. UNDER MAGNETRON MODULATOR Original Filed Jan. 3l, 1936 3 Sheets-Sheet 2 56 I 7 #mu fx@ May 21., 1940 E. G. UNDER MAGNETRN MODULTOR Original Filed Jan. 31, 1936 5 Shasta-Sheet 5 fnv/ernia?- Ressued May 21, 1940 UNITED STATES Re.'21,45s

PATENT OFFICE MAGNETRON MODULATOR Ernest G. Linder, Philadelphia, Pa., assigner to Radio Corporation of America, a corporation of Delaware 9 Claims.

lator. More particularly, my invention relates to the modulation of magnetrons by moving the anode with respect to the cathode, or by moving 5 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, 1, and the l5 cathode 3.

In contrast to the magnetron, an ordinary triode has a cathode, grid and anode. No magnetic field is required. The electrons travel in a substantially straight line from` the cathode to the B 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 25 the electrodes have been relatively movable. 'I'he 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 30 movement of the electrodes will have a secondary eect 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 g magnetic eld. Since the magnetron is used at ultra-high frequencies, the capacity between the anodes is of primary importance. tive movement will have a very large eiect on the operating frequency. Furthermore, the circular lo path of the electrons makes it possible to completely stop the flow of electrons to one anode and to greatly increase the electron 110W to th other.

Since the electron path is dependent upon the L5 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 re- ;0 spect to the cathode is illustrated in Fig. IB and Fig. IC. Other types of relative `movement will vproduce large changes in anode current. These lchanges are due to the characteristic magnetron operation.

g One of the objects of my invention is to modu- A slight relan (Cl. Z50-27.5)

My invention relates to a magnetron modulate a magnetron by changing the relative spacing .of the cathode and anode electrodes.

v 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. l

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

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

A still further object is to vary the frequency l5 of a magnetron oscillator by varying the interelectrode capacitance.

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

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

Figure 1I 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,

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 eld of Figure VI, l40

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

Figure VIc is a plan view of the pivotal mounting and biasing spring shown in elevation in Figure VI.

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 of Figure VII.

Throughout this specication 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 a pair of anodes ,55

5, 1. The cathode is energized by a battery 9. The anodes are connected to a pair of lead wires II, I3. A conductor I5 connects the lead wires. This conductor I5 and the anodes 5, 1 form a resonant circuit.

The lead wires I, I3 may form a transmission line which may Vbe connected to a dipole antenna or the like. The negative terminal of an anode battery I1 is connected to the cathode 3. 'I'he positive terminal of the anode battery is connected to a bridging conductor I9 which is suitably located on the leads II, I3.

A U-shape magnetic core `2| is energized by a core 23 and a battery 25. Suitable jaws (not shown) are attached to the pole pieces of the core 2| to clamp'the envelope I. The magnetic lines of force between the pole pieces surround and are substantially parallel to the cathode 3. 'Ihe arrangement thus far described may be operated as a, magnetron oscillator.

A series of corrugations 21 are formed in the section of the `envelope adjacent the lead-in of the transmission wires II, I3. A connecting link 29 is xed to the end of the envelope adjacent the corrugations 21. A magnetic armature 3| is fastened to the end of the link 29. An electromagnet 33 is suitably positioned with respect to the armature 3|. The winding of the electromagnet is serially connected to a local battery 35 and a microphone 31.

The corrugations 21 offer suicient flexibility 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 end which also supports the lead wires II, I3 causes a substantial movement of the anodes 5, 1 with respect to the cathode 3. This movement results in a change of electron distribution represented by Figs. IB to IC". 'I'his change will modulate the normal electron flow.

While I have illustrated the electromagnet 33 and microphone 31 as a convenient means of flexing the tube to effect modulation, it should be understood that other means may be employed. For example, a sound actuated diaphragm, a mechanical movement for telegraphic signalling, `or amplifiers may be used.

In Fig. III, the circuit is representative of a magnetron microphone-amplifier. In this device the magnetron operates as a microphone and also as an amplifier, although amplification is not essential. The leads II, I3 are connected to the primary 39 of the push-pull transformer 4I. The anode battery I1 is connected to the center tap of the primary 39. 'Ihe secondary 43 of the transformer represents the output of the device.

In place of the electromagnetic motor of Figure II, a sound operated diaphragm 45 has been connected to the link 29. A movement of the diaphragm is transmitted through the link 29 to the exible end of the envelope I. 'Ihe movement of the envelope in turn varies the relative position of anodes and cathode. This alters the electron distribution and hence the current flow through the primary 39.

A modification of Figure II is illustrated in VFigure IV. This modification consists primarily in substituting a flexible metal section 41 in place of the corrugated glass section of envelope I. As is known to those skilled in the art, a suit- ,able metal may be attached to glass by sealing.

The seal oers an airtight bond between the glass envelope I and the metal envelope 41. 'I'he free end of the metal envelope includes a glass insert 49 through which cathode leads may be brought.

In this modification, the cathode 3 is moved with respect to the anode electrodes 5, 1. The electro-magnetic motor device represented by armature 3| and magnet 33 has been connected through links 5|, 53 and lever 55. The lever is pivoted at 51. The single link 29 of Figure Il maybe used in place of the links and lever.

Likewise, the diaphragm 45 of Figure III may be Various movements of the anodes may be obtained by proper phasing of the exciting currents. The spaces between the armatures 6|, 63 and the walls of the envelope are suflicient to permit free movement of the armatures. The bridging conductor 69, which may be employed in a magnetron oscillator, has sunicient length and flexibility to permit movement of the lead wires II, I3. v

Since the anodes 5, 1 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 is oscillating as a negative resistance device, the oscillatory frequency is inversely proportional to the capacity between the anodes; therefore, the movements of the anodes with respect to each other will substantially vary their capacities and the oscillatory frequency. If the m-agnetron is oscillating as an electronic oscillator, variations in relative anode spacing will vary the amplitude of oscillations. Thus, the magnetron oscillator of Figure V may be frequency modulated by impressing currents of the desired modulation frequency on the electromagnets 65, 61.

The arrangement of Figure V may be employed as microphone-amplifier instead of an oscillator. As an amplifier, the bridging conductor may be omitted. In both cases, the magnetic eld is used. The electro-magnet structure 2|, 23, 25 of Figure II is suitable for this purpose. A U shape permanent magnet may be used as shown in Fig. V.

Instead of using the arrangement of Figure V as a microphone-amplier combination, this device may be used to generate audio frequency currents. In the generation of audio frequency currents the microphone 31 is omitted. A portion of the output currents, in the proper phase, is fed back to the exciting magnets 65, 61. The feedback currents may be amplified by a triode or the like. audio currents can be controlled by adjusting the natural frequency of vibration of the anodes 5, 1, armatures 6I, 63 and lead Wires I I, I3.

Figure VI represents a magnetron oscillator The frequency .of ther or amplier which is moved as a Who-le by the ytory currents, or the ampliiication, depends upon V7 vthe magnetic eld strength, modulation will be effected by the relatively varying eld. 'This arlrangement is best adapted to the electronic mode of oscillation.

In Figure VI, the envelope I is suitably fastened to a pivot member 1|. The pivot member 1| is pivotally supported by a yoke member 13. One or more biasing springs 15 are connected between fixed studs 11 on the yoke 13 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 gures, the pole pieces of the core 2| were of normal uniform shape and produced a substantially uniform field. The pole pieces 15 for this embodiment of my invention are illustrated in Figure VIa. The effect of the slanting pole pieces 19 is to produce a more dense magnetic Ifield between the near points and less dense between the more widely spaced points. Movement of the anodes 5, 1 and cathode 3 in the non-uniform eld will be equivalent to varying the eld. 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, aV or inverted V-shape pole piece or a conical shape Will have the required non-uniform eld. Where the eld has a rate o-f variation which is uniform with respect to movements on either side of the cathode, push-pull modulation may be produced.

The non-uniform iield 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 to portability and simplicity of frequency adjustments.

One means for moving the magnetron of Figure VI is illustrated as an electro-magnetic driver 8|. 'Ihe driver is shown in plan view in Figure VI and in elevational view in Figure VII). 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.

'I'he biasing springs 15 normally position the armature 85 in the center of the air gap of a magnetic core 81. 'Ihe air gap is of sufcient Width to permit the armature to freely oscillate within the gap when the magnet is energized. The energizing means includes the eld coil 09, battery 9| and microphone 93. Ampliers and lever actions may be employed in place of the direct drive shown.

A modication 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 eld is produced by a magnet which has slanting pole pieces 19 similar to those shown in Figure VIa.

The diaphragm 95 may be a cone of suitable size. A exible strip 91 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. 'I'his combination maybe 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 of envelope I. A pair of metal rings |03 are clamped at the ends of the envelope I. A pair of wires |05 are attached to each of the rings. These pairs of wires terminate in supports |01.

The pairs of wires and their connections act as a torsional balance. The suspended magnetron may be rocked about the axis of its envelope In this figure, the batteries and connecting leads have been omitted. 'I'he magnetron may be connected and adjusted for genillustration, a soundactuated diaphragm 95 is shown. The diaphragm 95 is coupled to the envelope I by suitable links IOI, |09. The force applied through these links rotates the magnetron about the axis of envelope I. The eld in the present instance is of the uniform type. l

:ilA

Normally, the magnetic ,lines of force are sub- 1 stantially parallel to they cathode 3. As the magnetron is rocked back and forth, the relative angular relation between the electrodes, and the magnetic lines lis varied. This variation alters the electron now and thereby modulates the output.

Thus I have described, and illustrated several embodiments of my invention by means of which a magnetron may bel 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:

l. 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 electromagnetic motor for varying the orientation of said electrodes by relative motion of said electrodes.

2. A magnetron including van evacuated envelope having a rigid section and a flexible section, an electron emissive cathode electrode supported by one of said sections, and a pair of anode electrodes supported by the other of said sections, means for establishing a magnetic neld to thereby cause electrons emitted from said cathode to travel curved paths to said anodes, and means for exing said flexible section so that said cathode and anodes may be moved relative to each other to thereby vary the number of electrons traveling between said cathode and anodes.

3. A magnetron including an evacuated envelope having a rigid section and a flexible metallic section, an electron emissive cathode electrode supported by one of said sections, means for establishing a magneticl field to thereby cause electrons emitted from said cathode to travel curved paths to said anodes, and a pair of anode electrodes supported by the other of said sections, and means for flexing said metallic section so that said cathode and anodes may be moved relative to each other to thereby vary the number of electrons traveling between said cathode and anodes.

electrode and spaced from said cathode electrode a pair of anode electrodes, means for creating a magneticeld whose lines of force surround and aresubstantially parallel to said cathode,

lsaid eld having such a value that the electrons which are released from said cathode move substantially tangentially to said anode electrodes,

' means for moving said anode electrodes With respect to said cathode electrode in accordance with a signal so that the electron current to one of said anode electrodes is increased by a movement which decreases the electron current lto the other of said anode electrodes, whereby a current is produced Whose variations correspond to said signal. I

6. A device for producing modulated ultra high frequency oscillations comprising a magnetron oscillator including a cathodeelectrode and spaced therefrom a pair of anode electrodes, means for producing a magnetic eld Whose lines of force surround and are substantially parallel to said cathode electrode, and means for producing relative movements between said electrodes to vary the characteristics of said oscillations in accordance with said movements.

7. A magnetron including an evacuated envelope having a rigid section and a flexible section, an electron emissive cathode electrode supported solely by one of said sections, and a pair of anode electrodes supported solely by the other of said sections, means for establishing a magnetic field perpendicular to the path of electron flow to thereby cause electrons emitted from said cathode to travel curved paths to said anodes, and means for flexing said flexible section so that said cathode and anodes may be moved relative to each other to thereby vary the number of electrons traveling between said cathode and anodes.

8. A magnetron microphone-oscillator modulator comprising an evacuated envelope having a rigid section and a flexible section, an electron emissive cathode supported solely by one of said sections and a pair of anode electrodes supported solely by the other of saidy sections, means for establishing a magnetic field parallel to the axis of said cathode to thereby establish ultra high frequency oscillations, and means for flexing said fiexible section in accordance with sound pressure variations so that said oscillations are modulated in accordance with said variations.

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

ERNEST G. LINDER.

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