US2832050A - Electron discharge devices - Google Patents

Description

April 22, 19158 .J M. STINCHFIELD 2,832,050

' ELECTRON DISCHARGE DEVICES Filed March 22, 1945 INVENTOIS. filmfiqaagll wfiaw flrro/zwiy UnitedStates Patent 2,832,059 ELECTRON DISCHARGE DEVICES John Maxwell Stiuchfield, Monmouth Junction, N. J., as-

signor to Radio Corporation of America, a corporation of Delaware Application March 22, 1945, Serial No. 584,136 Claims. (Cl. 332-5) My invention relates to ultra high frequency apparatus such as electron discharge devices employing cavity resonators and more particularly to magnet-tons employing cavity resonators and to means for tuning and modulating the same.

Magnetrons employing cavity resonators usually include a cathode surrounded by a plurality of anode segments, the cavity resonators being coupled between adjacent. segments. The anode assembly may be made from a solid block of conducting material with a central chamher having slots radiating therefrom, which may or may not be enlarged at their outer ends, to provide cavity resonators, the portions of the block 1 etween the slots providing the anode segments. In another type of construction a conductor ring supports a plurality of radially directed vanes or slats, the inner ends providing the anode segments and defining a central chamber in which the cathode is placed.

Various attempts have been made to tune this type of apparatus and to modulate the same. This usually required moving parts within the envelope of the magnetron or within the cavity resonators, complicating the structure and introducing undesirable modes of operation. A continuous tuning range with a uniform distribution of intensities in the standing wave pattern and in the desired mode of oscillation would not always result.

It is, therefore, an object of my invention to provide an electron discharge device of the magnetron type employing cavity resonators of improved design which can be tuned and modulated.

Another object of my invention is to provide such a device which can be tuned over a large continuous tuning range with a uniform distribution of intensities in a standing wave pattern and in the desired mode of oscillation.

A still'further object of-my invention is to provide a device of the hind described, which can be tuned or modulated by means external to the device.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figure 1 shows a side elevation of an electron discharge device made according to my invention, Figure 2 is a transverse section taken along the line 2-2 of Figure 1, Figure 3 shows a modification of a detail of the apparatus shown in Figures 1 and 2 and Figure 4 is an axial section of a modified electron discharge device embodying my invention.

In the embodiment 'of my invention shown in Figure 1 an anode block 19 of conducting material has provided at its axis a central cylindrical chamber 11, at the axis of which is mounted an indirectly heated-cathode 12 provided with heater and cathode leads l3 and 1d extend ing through tubular members 15 and 16 and sealed vacuum-tight by means of insulating cup-shaped members 17 and 18.

The attode block is provided with a pluralityot radially directed slots 19 communicating with enlarged cylinder like chambers 29, the longitudinal axes of which extend parallel to the cathode. The slots 19 and chambers 26 provide cavity resonators connected between adjacent anode segments 19 formed by slots 19. The output may be taken by the usual loop 21, the extension of which forms the inner conductor 21?. of a coaxial line, the outer conductor 22 of which is sealed vacuum-tight at 23 and has a screw portion 24 which may cooperate with an extension (not shown) of the outer tubular member 22 to extend the coaxial line or to couple the device to radiator. Magnets 43 and 44 provide the usual magnetic field parallel to the cathode in the cathode-anode space.

In a preferred embodiment of my invention I strap alternate anode segments together by means of conducting straps such as 25 and 26 to insure the desired vr -mode of operation whereladjacent segments operate 180 out of phase with each other. The other intermediate segments may be connected by straps 25 and 26 on the other side of the anode block.

In order to tune the device over a wide range, I employ a tunable resonator coupled in a manner to be described to the strap 26 within the envelope of the device. The tunable resonator illustrated is of the coaxial line type, and includes an outer conductor 30 and inner conductor 31, the ends being closed by a conducting disc 32. The inner conductor 31 is connected to inner conductor 33, which is electrically connected to the strap 26 at a point intermediate its connection with the anode segments 19. The outer conductor 3d is connected to a cone-shaped element 34 having a tubular extension 35 of reduced diameter received Within a bore 36 in the block 10 and a channel 36 in the anode surface and terminating close to the strap 26. Thus, the coaxial line tuning resonator is connected to each pair of adjacent anode segments. A vacuum-tight seal 34 is provided between the inner conductor 33 and the member 34. The coaxial line resonator may be tuned by the slidable shorting ring 38 operated by means of the handle 39.

This arrangement insures a large continuous tuning range with a uniform distribution of intensities in a standing wave pattern and in the desired mode of oscillation. Best results are obtained when the coaxial tuning resonator is completely enclosed, as shown, up to the point of connection with the cavity resonator circuits. At the point of connection between the coaxial tuning resonator and the cavities, the two circuits are joined so that the leakage reactance between them is as near zero as possible. The inner conductor is joined to the heavy strapping conductor 26 joined to the highest potential points of like polarity on the alternate vanes or anode segments. These heavy straps, preferably of cop per, permit the flow of large tuning currents. The outer conductor of the coaxial resonator may be made a part of the solid segment between two cavities as shown in Figure 1 or a part of the vanes if these are employed in the manner shown in. my copending application, Serial No. 584,137 filed March 22, 1945, now Patent No. 2,591,976, dated April 8, 1952, assigned to the same assignee as the present application. It is desirable to have the size and the position of the coaxial resonators such that no extraneous modes of oscillation are introduced, that is the electrical symmetry of the cavities should not be too greatly altered.

The point of connection of the tuning resonator to the cavity is located so that a strong resonance occurs in the desired mode of oscillation and no other strong resonance occurs in the operating range of frequencies. The desired mode of oscillation is the so-called 1r-mode, in which the anode segments are alternately positive and negative at a given instant. Usually this condition is obtained when there is just enough non-symmetry between the angular position of the tuning resonator and that of I, the output line to avoid setting up other modes of oscil lation. For example, the position of the tuning resonator with respect to the load line is less than 90. If an exact 90 symmetry occurs then other disturbing modes of oscillation may also appear. In order to obtain a wide tuning range it is necessary to choose inductance, capacitance and loss characteristics of the tuning resonator with respect to the equivalent characteristics for the loaded cavity resonators.

The tuning resonator may be connected externally to any one of a number of tunable circuit arrangements. For example, as shown a short circuiting ring may be used to change the eflfective length of the resonator. Or an open-ended resonator could also be utilized where the length of the center conductor is varied to tune the tube. Such an arrangement is shown in Figure 3. Here a conductor within which is mounted an inner conductor 31, having telescoped thereover a tubular member 31" fastened to an insulating rod 39'. The effective length of inner member 31 is varied by moving a tubular member 31". A tunable cavity resonator may also be coupled to the open-ended resonator. A small variable capacitance in conjunction with the open-ended resonator will also tune the tube. Thus tuning of the tuning resonator is not limited to the form shown.

The same principle may be employed for frequency modulating the magnetron. This may be accomplished by the addition of a second coaxial line resonator 40, 41 as shown connected to a modulating circuit 42 in Fig. 2. The inner conductor is sealed vacuum-tight to the outer conductor 41 by means of the insulating seal 40'. By means of this circuit the reactance of the resonator is changed which in turn effects the frequency of the cavity resonators within the tube at the modulating frequency. While for purposes of illustration the coaxial line resonator 40, 41 is shown connected to strap 25, for best results it would be connected to another strap such as 26' on the other side of the tube and in a position other than 90 to the output line. Thus not only may the resonant frequency of the device be changed from one frequency to another by means of a tuned coaxial line resonator, but the device may also be frequency modulated at these different resonant frequencies.

Figure 4 illustrates my invention embodied in a vanetype magnetron as shown in my above-mentioned copending application. This magnetron comprises a drumshaped metallic envelope containing a plurality of radially-extending fiat, metallic, anode vanes 51. The inner edges of the vanes 51 provide anode segments and define a cylindrical cathode space 52 in which a cathode 53 is axially mounted. Each pair of adjacent vanes together with the portion of the envelope therebetween constitutes a cavity resonator. A metallic strapping ring 54 is connected to one group of alternate anode vanes near the inner edges thereof. The remaining alternate vanes are connected together by a second metallic strapping ring 55 which may be arranged concentric with the ring 54, as shown.

In order to tune the magnetron a tuning resonator 56, preferably of the coaxial line type, is connected to the vane structure in a manner somewhat similar to that shown in Figures 1 to 3. The inner conductor 57 of resonator 56 is connected to the inner strapping ring 54. The outer conductor 58 of the tuning resonator extends radially inwardly along and in contact with one of the vanes 51 and is connected directly to the outer strapping ring 55. The tuning resonator 56 may be tuned by means of a slidable shorting ring, or by other means. The operation of the tuning resonator in varying the resonant frequency of the system is similar to that described above for Figures 1 to 3.'

While I have indicated the preferred embodiments of my invention of which I am now'aware and have also indicated only one sp cific application for'whichfmy invention may be employed, it will be apparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of my invention as set forth in the appended claims.

What I claim as new is:

1. An electron discharge device including an anode block having a central cylindrical chamber and a plurality of radially directed slots communicating with said chamber, anode segments between said slots, and a cathode adjacent said anode block for supplying elec trons within said central cylindrical chamber, a conducting strap connecting alternate anode segments,and means for varying the frequency of said electron discharge device and including a tunable coaxial line resonator, the inner conductor of which is connected to an intermediate point on said strap and the outer conductor of which is connected to the segment intermediate the segments connected by said strap.

2. An electron discharge device including an anode block having a central cylindrical chamber and a plurality of radially directed slots communicating with said chamber, said slots being enlarged at their outer ends, whereby anode segments connected by cavity resonators are provided, and a cathode adjacent said anode block for supplying electrons within said central chamber, a conducting strap connecting alternate anode segments, means for tuning said electron discharge device and including a coaxial line resonator, the inner conductor of which is connected to an intermediate point on said strap and the outer conductor of which is connected to a segment intermediate the segments connected by said strap. and an adjustable tuning ring within said coaxial line resonator for tuning said coaxial line resonator.

3. An electron discharge device including an anode block having a. central cylindrical chamber and a plurality of radially directed slots communicating with said chamber, anode segments between said slots, and a cathode adjacent said anode block for supplying electrons within said central cylindrical chamber, a conducting strap connecting alternate anode segments, and means for varying the frequency of said electron discharge device and including a tunable coaxial line resonator, said anode block having a bore extending radially from the outside of said block toward the wall of an anode segment, the inner ends of said coaxial line resonator being received within said bore, the inner conductor being connected to an intermediate point on said strap, and the outer conductor contacting said anode block.

4. An electron discharge device including an anode block having a central cylindrical chamber and a plurality of radially directed slots communicating with said chamber, said slots defining anode segments, and a cathode adjacent said anode block for supplying electrons within said central chamber, a conducting strap connecting alternate anode segments, and means for varying the frequency of said electron discharge device and including a tunable coaxial line resonator having an outer tubular member having a reduced inner end and a closed outer end, and an inner conductor, said anode block having a bore extending from the exterior thereof toward the wall of the anode segment intermediate the segments connected by said strap, the inner end of said coaxial line resonator extending within said bore, the inner conductor being connected to said strap and the outer tubular conductor to the walls of said bore, and a tuning member within said coaxial line resonator, the inner conductor of which is connected to an intermediate point on said strap and the outer conductor of which is connected to the intermediate segments connected by said strap.

5. An electron discharge device of the magnetron type having an electrode assembly including a cathode and a plurality of anode segments adjacent said cathode, cavity resonators connecting adjacent anode segments, a conducting strap connecting a pair of alternate anode segments, means for tuning said electron discharge device and including a coaxial line resonator having one conductor connected to said strap intermediate the ends of said strap and another conductor connected to the anode segment intermediate the anode segments connected by said strap, a second strap connected to another pair of alternate anode segments, and means for frequency modulating said electron discharge device including a second coaxial line resonator having one conductor connected to said second strap and the other conductor connected to the anode segment intermediate the segments connected to said second strap.

6. An electron discharge device of the magnetron type having an electrode assembly including a cathode and a plurality of anode segments adjacent said cathode, cavity resonators connecting adjacent anode segments, a con ducting strap connecting a pair of alternate anode segments, means for tuning said electron discharge device and including a coaxial line resonator having an inner conductor connected to said strap intermediate the ends of said strap and its outer conductor connected to the anode segment intermediate the anode segments connected by said strap, a second strap connected to other alternate anode segments, and means for frequency modulating said electron discharge device including a second coaxial line resonator having its inner conductor connected to said second strap and the outer conductor connected to an anode segment intermediate the segments connected to said second strap.

7. An electron discharge device of the magnetron type including an anode block having a central cylindrical chamber and a plurality of radially directed slots communicating with said chamber, said slots providing anode segments therebetween, and a cathode adjacent said anode block for supplying electrons within said central cylindrical chamber, a conducting strap connecting a pair of alternate anode segments, means for tuning said electron discharge device and including a tunable coaxial line resonator, the inner conductor of which is connected to an intermediate point on said strap and the outer conductor of which is connected to the segment intermediate the segments connected by said strap, a second strap connected to another pair of alternate anode segments, and means for frequency modulating said electron discharge device including a second coaxial line resonator having its inner conductor coupled to said second strap and its outer conductor to the anode segment intermediate the segments connected by said second strap.

8. An electron discharge device of the magnetron type having an electrode assembly including a cathode and a plurality of anode segments adjacent said cathode, cavity resonators connected between adjacent anode segments, a

conducting strap connecting alternate anode segments, means for varying the frequency of said electron discharge device and including a coaxial line resonator having inner and outer conductors, one of said conductors being connected to said strap and the other of said conductors to the anode segment intermediate the anode seg ments connected by said strap, and means connected to said coaxial line resonator for applying a modulating voltage between said inner and outer conductors.

9. An electron discharge device of the magnetron type having an electrode assembly including a cathode and a plurality of anode segments adjacent said cathode, cavity resonators connected between adjacent anode segments, a conducting strap connecting alternate anode segments, means for varying the frequency of said. electron discharge device and including a coaxial line resonator having inner and outer conductors, one of said conductors being connected to said strap and the other of said conductors to the anode segment intermediate the anode segments connected by said strap, means connected to said coaxial line resonator for applying a modulating voltage between said inner and outer conductors, and means within said coaxial line resonator for tuning said resonator to vary the resonant frequency of said electron discharge device.

10. An electron discharge device of the magnetron type having an electrode assembly comprising a cathode for supplying electrons and a plurality of anode segments adjacent said cathode for receiving said electrons, cavity resonators connected between adjacent anode segments and normally operable at a predetermined resonant frequency, and means for varying the frequency of said electron discharge device and including a tuning resonator having two conductors respectively connected to two adjacent anode segments and means connected to said tuning resonator for applying a modulating voltage between said two conductors.

References Cited in the file of this patent UNITED STATES PATENTS 2,217,745 Hansell Oct. 15, 1940 2,241,976 Blewett et a1. May 13, 1941 2,311,658 Hansen et a1. Feb. 23, 1943 2,348,986 Linder May 16, 1944 2,411,151 Fisk Nov. 19, 1946 2,414,084 Bowen Jan. 14, 1947 2,414,085 Hartman Jan. 14, 1947 2,435,984 Spencer Feb. 17, 1948 2,445,282 Slater July 13, 1948 2,450,629 Bondley Oct. 5, 1948 2,478,644 Spencer Aug. 9, 1949 2,523,286 Fisk Sept. 26, 1950 2,747,137 Tonks May 22, 1956

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