EP0160094A4

EP0160094A4 - Tuning apparatus for a radio frequency power device.

Info

Publication number: EP0160094A4
Application number: EP19850900516
Authority: EP
Inventors: Geoffrey Thornber
Original assignee: Brunswick Corp
Current assignee: Brunswick Corp
Priority date: 1983-11-02
Filing date: 1984-11-02
Publication date: 1988-06-16
Also published as: WO1985002071A1; JPS61500290A; EP0160094A1

Abstract

A tuning assembly (42) for selectively oscillating the frequency of an electromagnetic field within a hermetically sealed device (12), which device includes a rigid, hermetically sealed housing (14), apparatus for generating the electromagnetic field therewithin (32, 34 and 36), for elements for defining a cavity (30) within the housing for establishing the frequency of the electromagnetic field. The tuning assembly (42) includes electrically conductive members (54) mounted for linear movement within the cavity (30) to selectively vary the volume of the cavity (30) to oscillate the established frequency. Elements (52) disposed within the rigid housing (14) are provided for mounting the electrically conductive members (54), and are adapted for oscillatory movement at a predetermined mechanical resonant frequency to move the electrically conductive members (54) in the described linear manner. The tuning assembly (42) incorporates an electron emitter assembly having a highly efficient cathode assembly (24, 102) arranged in the form of a helical spring (102), the cathode assembly (24, 102) being composed of porous tungsten impregnated by an electronemissive material and being directly heated by an electric current (at 108). Finally, a power source (108) is provided exterior to the rigid housing (14) and is magnetically coupled to the mounting elements (44) for exciting the mounting of elements (44).

Description

TUNING APPARATUS FOR A RADIO FREQUENCY POWER DEVICE

Cross Reference to Related Applications

This application is a continuation-in-part of U. S. Patent Application S.N. 362,895, filed April 19, 1982, which was a divisional application of U. S. Patent Application S.N. 066,226, filed August' 13, 1979.

Technical 'Field,

This invention relates generally to radio frequency power devices and more particularly to tuning assemblies for oscillating the frequency output of such devices . More specifically, the subject invention relates to a novel tuning assembly for oscillating the frequency of an electromagnetic field generated within a hermetically sealed device, and in particular within a magnetron tube, to thereby oscillate the frequency output of such device.

Background of the Invention

Radio frequency power devices are well known in the art. Such power devices may generate radio frequency outputs at a fixed frequency or at variable frequencies oscillating within a specified operating frequency band. In general, such radio frequency power devices include therewithin a hermetically sealed housing which is either evacuated, as in the case of a vacuum tube or a magne- tron, or is filled with an inert gas. A variety of well known systems are utilized to generate an electromagnetic field within the hermetic housing, with the current induced from such an electromagnetic field being directed to an output antenna. One commonly used arrangement for generating such an electromagnetic field includes positioning an anode ring- about a centrally disposed cathode within the hermetic ho sing, and then establishing a magnetic field around, the anode. This is commonly done by positioning a pair of magnets on either side of the anode. In. this manner, an electrical field is created between the cathode and anode, and a magnetic field is generated within the interaction space between the cathode and anode, thereby establishing an electromagnetic field at the anode. In this particular arrangement, the anode ring defines a cavity space radially inwardly thereof, wherein the fre- quency of the electromagnetic field is established. In other arrangements, such as in a coaxial magnetron tube, the cavity space wherein the frequency of the electro¬ magnetic field is defined may be located exterior to the anode. In the above described arrangement, the frequency of the electromagnetic field is defined by the physical size and shape of the cavity as well as the conductive prop¬ erties of the material utilized to form the cavity. One known cavity arrangement includes a plurality of tabs or vanes projecting radially inwardly from the inner surface of the anode ring, and the frequency of the electromagnetic field is determined by the conductive properties of the vanes, the size of the vanes, the spac¬ ing between the vanes , and the manner in which the vanes may be electrically interconnected at their radially inner edges. Thus, by adjusting ttiese variables of the vane structure and thereby changing the overall volume of the cavity, any desired frequency may be pre-selected prior to construction of the radio frequency device. The manner in which th^'e vane structure is constructed and altered so as to establish a desired fixed frequency is well known in the art and will not be discussed in any detail herein.

Once the shape and the volume of the frequency determining cavity is established, the frequency of the electromagnetic field generated within such a device is set, and the resultant frequency output of the devices becomes fixed. In variable frequency power devices, how¬ ever, the frequency of the electromagnetic field within the hermetic housing is tunable or varied in an oscillat- ing manner by changing the volume of the frequency deter¬ mining cavity in an oscillatory fashion, thereby changing the inductive properties thereof. One known technique for changing the volume of the frequency determining cavity includes positioning an electrically conductive member within the cavity and oscillating that member therewithin, thereby varying the volume of the cavity in an oscillatory manner. To achieve such oscillatory motion of an electrically conductive member within the cavity, prior devices have commonly utilized mechanical arrangements for moving the electrically conductive member.

One such mechanical tuning arrangement utilizes a thin wall bellows or diaphragm as part of the hermetic housing. The electrically conductive members are then mechanically connected to such a bellows or diaphragm, and the bellows or diaphragm are mechanically oscillated • by a motor located outside the hermetic housing.

Another known tuning arrangement for changing the volume of the frequency determining cavity includes positioning electrically conductive members within the cavity and rotating such members along the inner surface of the anode ring. Such rotation is effected by magneti¬ cally coupling the rotating electrically conductive member to an electromagnetic power source disposed out- side the housing. A distinct disadvantage to this latter technique, however, is that by rotating an electrically conductive member within the frequency determining cavity, the electromagnetic field frequency can be varied, but not in an oscillatory manner. The movable bellows or diaphragm arrangement described above, however, also has certain disadvantages. One major disadvantage with this mechanical tuning arrangement is that the walls of the bellows or diaphragm must be relatively thin to effect such movement and are thereby subject to mechanical fatigue and failure. If such a bellows or diaphragm does fail, the vacuum or inert gas environment within the hermetic housing is destroyed, and the power source thereby becomes useless. Another disadvantage is that since the bellows or dia¬ phragm must be constructed from a thin- walled material, atmospheric gas can penetrate such thin material over a period of ttime and can thereby affect the internal environment. Therefore, such mechanical arrangements have a relatively short storage or shelf life.

A further disadvantage of the above mechanical tun- ing assemblies is that a significant energy input is required to operate such assemblies. This requirement is due to the mechanical resistance offered by the bellows or. diaphragm arrangement as well as to the atmospheric dampening effect on the mechanical parts located exterior to the hermetic housing or envelope.

The novel tuning assembly of the present invention, however, overcomes the disadvantages of known mechanical tuning assemblies, and provides a relatively simple yet efficient means for oscillating the frequency of the electromagnetic field generated within such radio frequency power sources.

Summary of the Invention

Therefore, it is one object of the present invention to provide a tuning assembly for selectively oscillating the frequency output of a radio frequency power source. It is another object of the present invention to provide a tuning assembly for selectively oscillating the frequency of an electromagnetic field within a hermetically sealed device wherein the device has a rigid or hermetic housing. A further object of the present invention is to pro¬ vide a magnetron tube having an oscillating frequency output and a rigid, hermetically sealed housing.

It is yet another object of the present invention to provide a tunable magnetron tube wherein the mechanical components of the tuner assembly are located entirely within a rigid, inflexible hermetic housing.

In accordance with the invention, a tuning assembly is provided^* for selectively oscillating the frequency of an electromagnetic field within a hermetically sealed device wherein such device includes a rigid, hermetically sealed housing, 'a mechanism for generating an electro¬ magnetic field within the housing, and elements for defining a cavity within the housing for establishing the frequency of the electromagnetic field. The novel tuning assembly includes electrically conductive members mounted for linear movement within the frequency defining cavity to selectively vary the volume of the cavity to oscillate, the e tablished frequency of the electromag- netic field. A mounting assembly for mounting the electrically conductive members is disposed within the rigid housing and is adapted for oscillatory movement at a pre-determined mechanical resonant frequency to move the electrically conductive members in the aforementioned linear manner. Finally, a power source is located exterior to the rigid housing and is magnetically coupled to the mounting assembly for exciting the mounting assembly.

The tuning assembly of the present invention may be adapted to oscillate the electromagnetic^* field frequency within any hermetically sealed device having a rigid, hermetically sealed housing and a frequency defining cavity within such housing. The subject invention, how¬ ever, is particularly useful in radio frequency power sources such as variable frequency magnetron tubes .

In one preferred embodiment of the present inven¬ tion, the mounting mechanism includes a support member for securely mounting the electrically conductive members within the housing. A spring, mechanism is provided for interconnecting the support member and the housing and is adapted to permit oscillatory movement of the support member within the housing. The pre-selected mechanical resonant frequency of the mounting mechanism is directly determinable in accordance with known techniques from the mass of the electrically conductive members and the mounting mechanism as well as the spring rate of the spring mechanism. The support member, is maintained at a constant pre-determined oscillatory movement by pulsing the power source at the same frequency as the pre¬ selected mechanical resonant frequency of the mounting mechanism. .In this manner, the frequency of the electro- magnetic field, and thereby the output frequency of the device, may be selectively oscillated in accordance with the pre-selected mechanical resonant frequency of the tuning assembly.

Brief Description of the Drawings The novel features which are believed to be char¬ acteristic of the present invention are set forth in the appended claims. The invention itself, however, together with further objects and attendant advantages thereof will become apparent and best understood by reference to the following detailed description taken in connection with the accompanying drawings, setting forth by way of illustration and example certain embodiments of the invention in the several figures of which like reference numerals identify like elements, and in which: Figure 1 is a side-sectional view of a magnetron tube mounted within a device, illustrating one embodiment of the tuning assembly of the present invention;

Figure 2 is a cross-sectional view taken substan¬ tially along the line 2-2 of Figure 1, illustrating the frequency defining cavity of the magnetron tube of Figure 1; ^:>

Figure 3 is a cross-sectional view taken substan¬ tially along the line 3-3 of Figure 1, illustrating the mounting mechanism of the present invention; Figure 4 is an exploded side elevation view, with some parts in section, of the tuning assembly of the present invention in relation to the anode structure of the magnetron tube shown in Figure 1;

Figure" 5 is an enlarged front prospective view of the electrically conductive members and support member of one embodiment of the tuning assembly of the pres nt invention; '

Figure 6 is a side elevation view of the embodiment illustrated in Figure 5; Figure 7 is an enlarged front prospective view of the mounting members and support member of a second embodiment of the tuning assembly constructed in accordance with the present invention;

Figure 8 is a side elevation view of the embodiment illustrated in Figure 7;

Figure 9 is a side elevation view of one electri¬ cally conductive member of the embodiment illustrated in Figures 5 and 6; and

Figure 10 is a side elevation view of one electri- cally conductive member of the embodiment illustrated in Figures 7 and 8.

Detailed Description of the Preferred Embodiments

Referring to Figure 1, a hermetically sealed device such as a magnetron tube 10 is illustrated and incorpo- rates the tuning assembly of the present invention.

Radio frequency power sources such as the magnetron tube 10 have many different uses , Figure 1 illustrating the tube 10 mounted in an enclosure 12. It is to be under¬ stood, however, that the present invention is not to be limited for use in such a magnetron tube 10, but rather may be utilized ^*in any device wherein the device includes a rigid hermetic housing and requires selective oscilla¬ tion of an electromagnetic field generated within the housing. The illustrated magnetron tube 10 includes a her¬ metically sealed housing 14 having an evacuated internal atmosphere. The housing 14 is entirely rigid and is com¬ prised of a tuner assembly housing 16, an anode assembly 18, and two magnetic pole piece housings 20 and 22 dis- posed on either side of the anode 18.. These members 16-22 are -all heliarc welded together to form the hermetically sealed housing 14.

Disposed within the housing 14 is the anode assembly 18, which forms a part of the housing 14, and a cathode assembly 24 spaced from the anode 18. In preferred form, the cathode 24 is centrally disposed along the longitudinal axis of the housing 14, which in preferred form is annular in shape. The anode 18 preferably is in the. form of an annular ring 26 having an inner raised rim portion 28 projecting radially inwardly toward the cathode 24 from the center portion of the ring 26. The inner surface of the ring 26 defines generally a cavity area 30 (Figure 2) which is disposed between the anode 18 and the cathode 24. The cavity area 30 comprises the area to establish the frequency of the electromagnetic field generated at the anode 18 by the electrons emitted from the cathode 24, which interact with the anode 18 and the magnetic field within the anode 18, as described in greater detail below. Disposed on either side of and coaxially with the anode ring 26 are a pair of magnetic pole pieces 32 and 34. The magnetic pole pieces 32 and 34 act in conjunc¬ tion with a permanent magnet assembly 36 so as to create a magnetic field about the anode 18 and the cathode 24. The interaction of the electrical field between the cathode 24 and the anode 18 and the magnetic field created by the magnetic assembly 36 and the pole pieces 32 and 34 occurs within the cavity 30 to establish an electromagnetic field at the anode 18.

The electromagnetic field at the anode 18 creates an alternating current in the anode 18 which passes along an antenna member 38. The alternating current induced in the anode 18 flows back and forth along the antenna 38 and changes at a specific radio frequency rate estab¬ lished by the cavity 30. This current, generates electro- magnetic waves from the antenna 38 which propagate outwardly•through the radome structure 40.

Referring more particularly to Figures 1, 3, and 4, the magnetron tube 10 includes a tuning assembly 42 constructed in accordance with the present invention. The assembly 42 includes the outer hermetically sealed housing 16, which is preferably annular in shape, and a tuning mechanism 43. More particularly, a mount¬ ing assembly 44 is disposed coaxially within the housing 16. In preferred form, the mounting assembly 44 includes a tubular support member 46 suspended for linear reciprocating or oscillatory movement within the housing 16, and a tubular support element 48 which has a smaller diameter than the diameter of the support member 46 and is mounted on an annular flange 50 coaxially with and for linear movement with the support member 46.

An electrically conductive element 52 is mounted on the end of the tubular support element 48 and extends into the cavity 30 defined by the anode 18. In preferred form, the electrically conductive element 52 includes a plurality of electrically conductive members 54 circum- ferentially spaced about the end of the support element 48 and projecting into the cavity 30 as described in greater detail below. The electrically conductive element 52, the support element 48 and the support member 46 are all secured together to form the tuning mechanism 43 and move in unison in a linear oscillating manner. A spring assembly 56 is provided for interconnecting the mounting assembly 44 to the housing 16. In preferred form, the spring assembly 56 includes a plurality of leaf springs 58 securely mounted at one end to the support member 46 adjacent to the junction of the support ele¬ ment 48 and at the other end to the housing 16, and a plurality of leaf springs 60 securely mounted to the lower opposite end of the support member 46 and the housing 16.- The ends of each spring 58, 60 are securely mounted so that the mounting assembly 44 is suspended within the housing 16. In the illustrated form, there are four leaf springs 58 and four leaf springs 60, each in the form of an elongated "s." The springs 58 are positioned equidistantly about the circumference of the support member 46, and the springs 60 are also disposed equidistantly about the circumference of the support member 46.

.In the preferred form, the support member 46 and the support element 48 are constructed from non-magnetic material. To assist in exciting the oscillatory move¬ ment of the mounting assembly 44, the mounting assembly 44 further includes an annular magnetic member 62 secured about the support member 46 by a pair of annular brackets 64, 66. The magnetic member 62 is adapted to move in uniform linear movement with the mounting assembly 44.

The tuning mechanism 43, which includes the entire mounting assembly 44 and the electrically conductive element 52, is designed to move at a natural, pre- selected mechanical resonant frequency in a linear direction coaxial with the longitudinal axis thereof. The natural resonant frequency of the tuning mechanism 43 is dependent on the mass and spring rate of the mechanism 43. Therefore, the natural resonant frequency of the tuning mechanism 43 may be readily pre-selected by varying either the mass of the mechanism 43 and/or the spring rate of the spring assembly 56. The techniques for calculating the natural resonant frequency from the mass and spring rate are well known in the art and will therefore not be described herein.. Once the mass of the tuning mechanism 43 and the spring rate of the spring mechanism 56 have been selected, however, the natural resonant frequency of the mechanism 43 may still be altered by inserting a spring coil 66 (Figure 1) within the support member 46. The spring coil 66 is affixed to the inner surface of the flange 50 and the inner surface of the bottom portion of the housing 16. The spring rate of the coil spring 66 may be selectively varied so as to 'achieve the desired natural resonant frequency for the tuning mechanism 43.

To excite the tuner mechanism 43 at its natural resonant frequency, a power source 68 is provided about the exterior surface of the housing 16 and is magneti¬ cally coupled to the magnetic member 62. In preferred form, the power source 68 comprises an electromagnetic .coil 70 wrapped around the housing 16. The coil 70 is adapted to be alternately energized and de-energized in a pulsating manner so that when the coil 70 is energized, the magnetic member 62 is attracted to move the tuning mechanism 43 in a first linear direction. After such a pulsing of the coil, the coil 70 returns to a de- energized state, and the spring mechanism 56 returns the tuning mechanism 43 beyond its initial position, thereby moving the mechanism 43 in a second opposite linear direction. Therefore, the coil 70 is repeatedly pulsed at the same frequency rate as the natural resonant fre- quency of the tuning mechanism 43 so as to maintain the tuning mechanism 43 in a constant oscillating motion. This oscillating movement of the tuning mechanism 43 causes the electrically conductive element 52 to oscil¬ late within the cavity 30. This mechanical oscillation of the electrically conductive element 52 within the cavity 30 changes the volume of the cavity 30 in an oscillatory manner, and as the volumes of the cavity 30 is changed, the nductance of current from the electro¬ magnetic field is changed in a similar oscillatory manner so as to vary the frequency of the electromagnetic field within the cavity 30 in such an oscillatory manner. Referring to Figures 1, 2, and 4, the annular assembly 18 includes the anode ring 26 and the rim mem¬ ber 28. In the preferred embodiment, the annular anode assembly 18 further includes a plurality of spaced tabs in the form^'of vanes 72 integrally formed with the rim 28 and extending radially inwardly toward the cathode

24. Each .vane 72 is a flat electrically conductive mem¬ ber having a plane aligned with the central axis of the anode ring 26. The vanes 72 divide the cavity area 30 into a plurality of individual cavities or chambers 74 defined between the vanes 72. In addition, a plurality of electrically conductive strap members 76 are prefer¬ ably provided in the form of annular rings which selec¬ tively interconnect a plurality of vanes 72. In pre¬ ferred form, there are_. two strap members 76 and 76'^* which interconnect alternate vanes 72 so that one-half of the vanes 72 are electrically connected to one strap 76, and the other half of the vanes 72 are interconnected to the second strap 76'. The straps are utilized in con¬ junction with the vanes 72 and the ring 28 to define a particular frequency for the electromagnetic field created within the cavity area 30. Use of such straps 76, 76', and the technique for calculating the appropri¬ ate dimensions and arrangements of the vanes 72, the straps 76, 76', and the ring 26, to establish a specific frequency, are well known in the art and are therefore not disclosed specifically herein.

When the anode assembly 18 is constructed in the above described preferred form, the electrically con¬ ductive element 52 is preferably in the form of a plurality of electrically conductive members 54. The members 54 are mounted circumferentially about the end of the support element 48 and are appropriately spaced so that each member 54 is adapted for positioning within one cavity 74. The end portion of each member 54 is positioned so that it remains within a cavity 74 as the tuning mechanism 43 is oscillated. As the tuning mechanism 43 oscillates the electrically conductive member 54 also oscillates within a cavity 74, thereby changing the volume of each cavity 74 in a uniform oscillating manner. Thus, the entire volume of the cavity area 30 is changed in a uniform oscillating man¬ ner. This, change in the volume Of each cavity 74 by the

» presence of an electrically conductive member therein alters the inductance of current by the annular ring 28 and changes the frequency of the electromagnetic field present within the cavity area 30. This change in the electromagnetic field is proportional to -the change of the volume of the cavity area 30, so that the frequency of the electromagnetic field oscillates in a propor¬ tional manner with the oscillation of the tuning echa- nism 43. As the frequency of the electromagnetic field within the cavity area 30 oscillates, the output fre¬ quency of the magnetron 'tube 10 similarly oscillates about the pre-selected frequency.

Referring to Figures 1 and 4, the magnetic pole pieces 32 and 34 are preferably comprised of a soft magnetic material, such as iron, which is not permanently magnetized. The magnetic pole pieces 32 and 34 direct the magnetic field from the permanent magnetic assembly 36 into the interaction space between the cathode assembly 24 and the anode assembly 18. The permanent magnetic assembly 36 may comprise any known arrangement. In the illustrated embodiment, the assembly 36 includes two permanent magnets 78 and 80 interconnected by steel tubes 82, 82', and a sleeve member 84. Thus, the strength of the magnetic field may be selectively varied depending upon the strength of the permanent magnets 78, 80. The magnetic pole piece 34 includes an annular bracket assembly 86, which functions to mount the perma¬ nent magnet 80 as well as to form the housing 20, and a magnetic pole piece member 88. The magnetic pole piece member 88 includes a plurality of orifices or channels 90 which are coaxially aligned with the longitudinal axis of the electrically conductive members 54 and the anode ring 26. The channels 90 function as passageways for the electrically conductive members 54 between the support element 48 and the cavities 74.

Referring more specifically to Figures 4, 5 , 6, and 9, one preferred embodiment of the electrically conduc¬ tive members 54 is illustrated therein. In this embodi¬ ment, each electrically conductive member 54 comprises a pin member 92 constructed from any suitable electri¬ cally conductive material. The pin 92 has a substan¬ tially uniform diameter along its length, and includes a base portion 94 which is notched to form a ledge for mounting the pin 92 to the support element.48. The diameter of the pin 92 is selected so that the pin 92 freely passes through a channel 90 and is positioned between a pair of vanes 72 without making contact therewith.

When the electrically conductive member 54 is in the form of the pin 92, however, there is a tendency for secondary resonant effects to be introduced into the magnetic pole piece 34 due to the oscillation of the electrically conductive pin 92 within the channel 90. When it is desired to avoid such secondary resonant effects , a second preferred embodiment of the invention may be utilized.

Referring to Figures 7, 8, and 10, wherein the second embodiment of the electrically conductive member 54 is illustrated, the member 54 is in the form of an elongated member 95 having an expanded diameter end portion 96 for positioning within a cavity 74. The end portion 96 is constructed from electrically conductive material and is of sufficient diameter to substantially fill the cavity 74 in cross-sectional dimension, as illustrated in Figure 2. The elongated member 95 also includes a shaft portion 98 which interconnects the end portion 96 to the support element 48, and the diameter of the shaft portion 98 is substantially less than the diameter of the end portion 96. The shaft portion 98 is sized so that the shaft portion 98 remains within the channel 90 as the tuning mechanism 43. oscillates. In this manner, the amount of material within the channel

90 is substantially reduced, which in turn substantially reduces the secondary resonant eff cts . Furthermore, the shaft portion 98 may also be constructed from an electrically non-conductive material such as a ceramic material. In this manner, the secondary resonant effects in the magnetic pole piece 34 are almost non¬ existent. The shaft 98 preferably includes a base portion 100' which is notched to form a ledge for attach- ment to the support element 48.

Referring now to Figure 1, the cathode structure 24 is preferably in the form of a helical, spring-like mem¬ ber 102 positioned between two end plates 104, 106. The helical member 102 is preferably constructed from porous tungsten impregnated by electron emissive material, such as barium and calcium aluminates, as known in the art. This particular cathode structure is directly heated by a current from conductors 108. This direct heating of the impregnated tungsten causes improved electron emis- sion by the cathode 24 and rapid warm-up. It has been found that this arrangement for heating the cathode permits warm-up in about 5 seconds instead of about 12 to 20 seconds if the cathode were indirectly heated in the conventional way. In addition, the helical shape of the cathode 24 presents a cylindrical outline with greatly increased emissive surface. This combination of the increased emissive surface and the directly heated cathode with fast warm-up provides a considerably more efficient electron emitter assembly than has been previously known in a pulse magnetron. The tuning assembly 42 as described above provides a constantly variable frequency across a specific fre¬ quency band, generally varying 57. on either side of a center frequency. For example, the tuning mechanism 42 as disclosed in the magnetron 10 of Figure 1 can provide a 100-300 MHz frequency variation around any selected center frequency, the selected center frequency being

< established by the dimensions of the anode assembly and the cavity defining elements. Such a center frequency can be established at any desired frequency, for example, between 1-50 gigahertz, by utilizing known technique in the art. To achieve such a frequency variation, the natural resonant frequency of the tuning mechanism 43 may be generally set at approximately 15-20 cycles per second. However, as previously described, the natural resonant frequency of the tuning mechanism 43 may be established at any selected level, thereby permitting any desired frequency variation to occur in the electro¬ magnetic field at the anode 18.

As can be seen from the above, the present invention provides a novel mechanism whereby the frequency of an electromagnetic field within a hermetically sealed device may be readily varied in an oscillatory manner. This oscillatory variation of the frequency is achieved by a mechanical oscillating device which has all moving mechanical components disposed within a rigid housing. Therefore, there are no thin walled or flexible portions required in the hermetically sealed housing, which design prevents atmospheric leakage and provides a long storage or shelf life. Furthermore, in the example wherein the tuning assembly of the invention is used in a magnetron or other vacuum tube, all the mechanical parts perform within a vacuumj'' thereby obviating the dampening effect of any atmospheric environment. Finally, the tuning assembly of the present invention is based on a natural resonant frequency of the tuning mechanism. To oscil- 5 late this mechanism in a desired manner, only a small amount of energy in a pulsed form is required, inasmuch as the power source for moving the tuning assembly is magnetically coupled to the tuning mechanism.

It will be understood that the invention may be Q embodied in other specific forms without departing from the spirit or central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims.

Claims

AMENDED CLAIMS

[received by the International Bureau on 18 April 1985 (18.04.85); original claim 20 cancelled; remaining claims unchanged (7 pages)]

1. A pulsed magnetro _ ube comprising: rigid hermetic housing means; a cathode assembly disposed along the center axis of said housing means; an anode assembly disposed within said housing means ; means for generating an electromagnetic field at said anode assembly; means disposed within said housing means for defining the frequency of said electromagnetic field; tuning means mounted within said housing means for linear movement to selectively vary said frequency in - an oscillatory manner; said tuning means being concentric with said cathode assembly and mounted at the same end of said magnetron tube as said cathode assembly; and power means disposed exterior to said housing means for exciting said tuning means.—

2. The magnetron tube as described in claim 1, wherein said frequency defining means comprises an assembly defining at least one cavity having a fixed volume pre-selected to establish the frequency of said electromagnetic field.

3. The magnetron tube as described in claim 2, wherein said tuning means comprises an electrically conductive element disposed for linear movement within said cavity in an oscillatory manner to selectively vary the volume of said cavity to thereby vary the frequency of said electromagnetic field. 4. The magnetron tube as described in claim 3, wherein said tuning means further comprises mounting means for securing said electrically conductive element in position within said cavity, resilient means for interconnecting said mounting means and said housing means, and a magnetic member affixed to said mounting means, said tuning means having a pre-determined mechanical resonant frequency, and wherein said power means comprise a pulsed electromagnetic power source disposed exterior to said housing means and magnetically coupled to said magnetic member, whereby energization of said power source moves said tuning means in a first linear direction, and said resilient means moves said tuning means in a reverse linear direction upon de- energization of said power source.

5. The magnetron tube as described in claim 2, wherein said cavity defining assembly comprises an annular 'body forming a portion of said anode and a plurality of spaced tabs in the form of vanes projecting radially inwardly from said annular body to define a plurality of cavities therebetween.

6. The magnetron tube as described in claim 5, wherein said tuning means comprises a plurality of electrically conductive members, each disposed for uniform linear movement within one said cavity in an oscillatory manner to vary the volumes of said cavities a pre-determined amount to selectively vary the frequency of said electromagnetic field.

7. The magnetron tube as described in claim 6, wherein said tuning means further comprises a tubular mounting support coaxially disposed proximate said annular body and having one end adapted to secure said electrically conductive members circumferentially thereabout, spring means interconnecting said mounting support and the inner surface of said housing means and adapted to permit linear reciprocating movement of said mounting support within said housing means, and a magnetic member secured to said mounting support, said tuning means having a pre-determined mechanical resonant frequency, and wherein said power means comprises an electromagnetic coil disposed about said housing means and magnetically coupled to said magnetic member such that pulsing of said coil moves said tuning means in a first linear direction, said spring means moving said tuning means in a reverse linear direction, whereby repeated pulsing of said coil at said pre-determined resonant frequency moves said electrically conductive members in an oscillatory manner within said cavities.

8. The magnetron tube as described in claim 7, wherein each said electrically conductive member comprises an electrically conductive pin of substantially uniform diameter mounted to said mounting support and having an end portion projecting into one said cavity.

9. The magnetron tube as described in claim 7, wherein each said electrically conductive member includes an electrically conductive end portion positioned within one said cavity and a shaft portion having a diameter substantially less than said end portion extending from said end portion to said mounting support.

10. The magnetron tube as described in claim 1, wherein said shaft portion is constructed from non- conductive ceramic.

11. A pulsed magnetron tube comprising: rigid hermetic housing means; a cathode assembly disposed along the center axis of said housing means; said cathode assembly comprising a directly heated helical cathode member constructed from porous tungsten impregnated with an emissive material; an anode assembly disposed within said housing means; means for generating an electromagnetic field at said anode assembly; means disposed within said housing means for defining the frequency of said electromagnetic field; tuning means mounted within said housing means for linear movement to selectively vary said frequency in an oscillatory manner; said tuning means being concentric with said cathode assembly and mounted' at the same end of said magnetron tube as said cathode assembly; and power means disposed exterior to said housing means for exciting said tuning means.

12. A magnetically coupled tunable magnetron tube comprising: rigid hermetic housing means; a cathode and conductor disposed within said housing means; an annular anode assembly spaced from and surrounding said cathode within said housing means; means for generating an electromagnetic field at said anode assembly; means for defining a cavity radially inwardly of said anode assembly for establishing the frequency of said electromagnetic field; tuning means mounted within said housing means concentric with said cathode and conductor and adapted for linear movement to selectively vary said frequency in an oscillatory manner, said tuning means being mounted at the same end of said magnetron tube as said cathode and conductor; and power means disposed exterior to said housing means and magnetically coupled to said tuning means for moving said tuning means in an oscillatory manner.

13. The magnetron tube as described in claim 12, wherein said tuning means is adapted for oscillatory movement at a pre-selected mechanical resonant frequency and includes electrically conductive means disposed for linear oscillatory movement within said cavity to selectively vary the volume of said cavity to thereby vary the frequency of said electromagnetic field.

14. The magnetron tube as described in claim 13, wherein said annular anode assembly includes an electrically conductive ring surrounding said cathode, wherein said cavity defining means comprises said ring and a plurality of electrically conductive spaced-apart tabs in the form of vanes projecting radially inwardly from said ring to define a plurality of cavities therebetween, and wherein said tuning means further includes a tubular mounting support disposed coaxially with and spaced from said ring, said electrically conductive means comprising a plurality of electrically conductive members secured to one end of said mounting support, each said electrically conductive member being mounted for uniform linear oscillatory movement within one said cavity to vary the volumes of said cavities a pre-determined amount to thereby selectively vary the f rquency of said electromagnetic f ield .

15. The magnetron tube as described in claim 14, wherein said electromagnetic field generating means comprises a pair of magnetic elements disposed coaxially with and on either side of said anode ring, one said magnetic element being interposed between said anode ring and said tubular mounting support and having a plurality of channels therein axially parallel with the axis of said anode ring for providing passageways for said electrically conductive members between said cavities and said mounting support.

16. The magnetron tube as described in claim 15, wherein each said electrically conductive member 'comprises an electrically conductive pin of substantially uniform diameter mounted to said mounting support, passing through -one said channel and having an end portion projecting into one said cavity.

17. The magnetron tube as described in claim 15, wherein each said electrically conductive member includes an electrically conductive end portion positioned within one said cavity, and a shaft portion having a diameter substantially less than said end portion extending from said end portion through one said channel to said mounting support.

18. In an electron emitter assembly for a pulse magnetron, the improvement comprising a cathode structure arranged in the form of a helical spring, said cathode structure being composed of porous tungsten impregnated with an electron-emissive material, said cathode structure being directly heated by an electric current; whereby said cathode structure combines the features of efficient shape, high electron emissivity and rapid warm-up, thereby providing a greatly improved electron emitter assembly.

19. The electron emitter assembly of claim 18 wherein said electron emissive material comprises a mixture of barium and calcium aluminates.

20. Cancelled

STATEMENTUNDERARTICLE19

Pages 18 to 23 inclusive of the original international application have been amended by substitution of new pages 18 to 23A inclusive, these new pages having the designation "(amended)" immediately after the page number. Specifically claims 1, 11, and 19 have been amended as these claims were amended in the priority application. Claim 11 has been both amended and rewritten in independent form. Claim 20 has been cancelled and omitted from the new pages of claims.

The additions to the amended claims do not go beyond the disclosure of the original application as filed, since this subject matter was disclosed in the specification and the drawings, as originally filed.