Patent Grant
7719196
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2007-101713 filed on Apr. 9, 2007, the content of which is incorporated by reference.
1. Field of the Invention
The present invention relates to a structure of a coaxial-to-waveguide transition for an input and/or output of radio frequency signals, and a traveling wave tube including the structure of the coaxial-to-waveguide transition.
2. Description of the Related Art
Conventionally, a traveling wave tube is known as a microwave tube. Many traveling wave tubes include structures of coaxial-to-waveguides transition as input window in which a radio frequency wave is inputted, or output window from which a radio frequency wave is outputted.
The output window included in a traveling wave tube related to the present invention is disclosed, for example, in Japanese Utility Model Laid-Open No. 5-23397 (see
In such a traveling wave tube, the matching property in the vicinity of insulating window member 109 is determined by the characteristic impedance set by the size of the component parts including the coaxial center conductor of exterior portion 111. In the output transition section, in order to reduce the return loss of an amplified radio frequency wave, impedance in the output transition section needs to be adjusted to be optimal.
Incidentally, each of the components configuring the output transition section inevitably causes variation in the outside dimensions, such as the length and the outside diameter due to machining accuracy, dimensional tolerance and the like. Therefore, in the configuration of the output transition section related to the present invention, in order to adjust the characteristic impedance to a desired optimal value, a plurality of components differing in outside dimensions are prepared when manufacturing the individual output transition sections, and the components from which the optimal impedance value is obtained are selected and assembled from a plurality of components. Therefore, there are disadvantages in that the operation of adjusting impedance is complicated, and manufacturing costs increase.
An object of the present invention is to provide a structure of a coaxial-to-waveguide that is transition capable of easily adjusting the characteristic impedance by a coaxial center conductor of exterior portion, and a traveling wave tube.
In order to attain the above-described object, a structure of a coaxial-to-waveguide transition according to the present invention includes a waveguide for inputting or outputting a radio frequency wave, a vacuum envelope provided with a slow-wave circuit, a coaxial connection part connecting the waveguide and the vacuum envelope, an insulating and sealing member which is provided in the coaxial connection part and which hermetically seals a side of vacuum envelope and a side of waveguide, a coaxial center conductor of an exterior portion with one end supported by the waveguide, and a coaxial center conductor of an interior portion with one end abutting on the slow-wave circuit and the other end connected to the coaxial center conductor of an exterior portion. The waveguide is provided with a screw part supporting the coaxial center conductor of the exterior portion movably in an axial direction of the coaxial center conductor of exterior portion. An end of the coaxial center conductor of the exterior portion is connected to an end of the coaxial center conductor of the interior portion movably in an axial direction of the coaxial center conductor of the exterior portion.
The structure of the coaxial-to-waveguide transition according to the present invention configured as described above moves the end of the coaxial center conductor of the exterior portion in the axial direction of the coaxial center conductor of the exterior portion by the screw part, and thereby, impedance is easily adjusted by the coaxial center conductor of the exterior portion.
Further, in the coaxial center conductor of the exterior portion included in the structure of the coaxial-to-waveguide transition according to the present invention, the end portion connected to the coaxial center conductor of the interior portion may be provided to be movable within a moving range in the inside of the waveguide. Thereby, impedance in the waveguide can be adjusted.
Further, in the coaxial center conductor of the exterior portion included in the structure of the coaxial-to-waveguide transition according to the present invention, the end portion connected to the coaxial center conductor of the interior portion may be provided to be movable within a moving range in the inside of the coaxial connection part. Thereby, impedance in the coaxial connection part can be adjusted.
Further, in the coaxial center conductor of the exterior portion included in the structure of the coaxial-to-waveguide transition according to the present invention, the end portion connected to the coaxial center conductor of the interior portion is projected to the inside of the waveguide with respect to the axial direction of the coaxial center conductor of the exterior portion, and the end portion is located in the inside of the waveguide. Thereby, impedance in the waveguide can be adjusted.
Further, in the coaxial center conductor of the exterior portion included in the structure of the coaxial-to-waveguide transition according to the present invention, the end portion connected to the coaxial center conductor of the interior portion is projected to the inside of the coaxial connection part with respect to the axial direction of the coaxial center conductor of the exterior portion, and the end portion is located in the inside of the coaxial connection part. Thereby, impedance in the coaxial connection part can be adjusted.
Further, the screw part included in the structure of the coaxial-to-waveguide transition according to the present invention preferably includes a screw member supporting the coaxial center conductor of the exterior portion, a screw hole which is formed in the waveguide and provided so that the screw member is movable, and a restriction part restricting the movement of the screw member so that the screw member is moved only in the inside of the screw hole. According to this configuration, the screw member which is moved inside the screw hole is restricted in movement in the axial direction of the screw member by the restriction part, and therefore, the screw member is not projected to the inside of the waveguide. Therefore, unintended change in impedance by the screw member is prevented, and the occurrence of arcing in the tip end portion of the screw thread inside the waveguide is prevented.
Further, in the coaxial connection part of the structure of the coaxial-to-waveguide transition according to the present invention, a dielectric for adjusting impedance in the coaxial connection part may be provided at a position adjacent to the insulating and sealing member. According to this configuration, the impedance in the vicinity of the insulating and sealing member is varied to a relatively large extent, and therefore, the structure of the coaxial-to-waveguide transition can be easily applied to the other specifications that have different impedances.
A traveling wave tube according to the present invention includes a structure of the coaxial-to-waveguide transition according to the above described present invention.
According to the present invention, the coaxial center conductor of the exterior portion is supported by turning of the screw part provided in the waveguide to be movable in its axial direction, and the coaxial center conductor of the exterior part is moved in its axial direction by adjustment by the screw part, whereby impedance of the structure of the coaxial-to-waveguide transition can be easily adjusted.
Hereinafter, concrete exemplary embodiments will be described with reference to the drawings.
In this exemplary embodiment, a structure of a coaxial-to-waveguide transition of the present invention will be described as an output transition section included in a traveling wave tube, but the present invention is not limited to the output side, and may naturally be applied to an input transition section.
In order to output amplified radio frequency signals, a traveling wave tube includes output transition section 1 as shown in
Waveguide 6 of output transition section 1 is formed by a metal material, and is provided with connection hole 6a to which coaxial connection part 7b of vacuum envelope 7, which will be described later, is connected, as shown in
Screw part 13 includes screw member 16 which supports one end portion of the coaxial center conductor of exterior portion 11, screw hole 17 which is formed in waveguide 6 so that screw member 16 is movable, and restricting part 18 which restricts movement of screw member 16 so that screw member 16 is moved in only the inside of screw hole 17.
In screw member 16 of screw part 13, a groove in which a screw driver is engaged is formed in a head portion located at an outer peripheral portion side of waveguide 6 though not illustrated. Restricting part 18 of screw part 13 is formed at one end side of screw hole 17 integrally with the inner wall of waveguide 6. Bearing hole 18a (
Accordingly, when the coaxial center conductor of exterior portion 11 is moved in the axial direction of the coaxial center conductor of exterior portion 11, screw member 16 which is moved in the axial direction of screw member 16 abuts on restricting part 18, so that screw part 13 is constructed not to be projected to the inside of waveguide 6. Therefore, the impedance in waveguide 6 is prevented from changing as a result of screw member 16 projecting to the inside of waveguide 6.
Vacuum envelope 7 of output transition section 1 is formed by a metal material, and includes vacuum tube part 7a with helix slow-wave circuit 8 disposed in the inside, and coaxial connection part 7b which is formed integrally with vacuum tube part 7a and which is connected to waveguide 6. Engaging piece 19 which is engaged with connection hole 6a of waveguide 6 is provided at the end portion of coaxial connection part 7b to be elastically displaceable.
The coaxial center conductor of exterior portion 11 is formed into a rod shape by a conductive material, and includes bearing hole 21 (
The coaxial center conductor of exterior portion 11 is formed to be of a predetermined length so that when the coaxial center conductor of exterior portion 11 is moved in the axial direction of the coaxial center conductor of exterior portion 11 by turning of screw part 13, end portion 11a connected to the coaxial center conductor of interior portion 12 displaces within moving range R1 in the inside of waveguide 6. In the coaxial center conductor of exterior portion 11, end portion 11a whose outside diameter is formed to be large is moved in the axial direction of the coaxial center conductor of exterior portion 11 in the inside of waveguide 6, and thereby, the impedance in waveguide 6 is adjusted to a relatively large extent.
The coaxial center conductor of interior portion 12 is formed into a rod shape by a conductive material, and is formed to have a predetermined length corresponding to the length of the coaxial center conductor of exterior portion 11. In the coaxial center conductor of interior portion 12, one end abuts on an end portion of slow-wave circuit 8, and the other end is connected to the coaxial center conductor of exterior portion 11.
Insulating window member 9 is formed into a disk shape by an insulating material such as ceramics, and is provided to be fixed to coaxial connection part 7b. Insertion hole 9a through which the coaxial center conductor of interior portion 12 is inserted is provided in the center of insulating window member 9, and the coaxial center conductor of interior portion 12 is fixed to insertion hole 9a.
About output transition section 1 which is configured as above, an operation of moving the position of end portion 11a of the coaxial center conductor of exterior portion 11 in the axial direction of the coaxial center conductor of exterior portion 11 will be described.
In screw part 13, screw member 16 is moved along screw hole 17 with a screw driver or the like, and thereby, the coaxial center conductor of exterior portion 11 is moved in the axial direction of the coaxial center conductor of exterior portion 11 together with screw member 16. As the coaxial center conductor of exterior portion 11 is moved along its axial direction, the end portion of the coaxial center conductor of interior portion 12 fixed to a side of vacuum envelope 7 is moved with respect to bearing hole 21 of the coaxial center conductor of exterior portion 11. At this time, when end portion 11a of the coaxial center conductor of exterior portion 11 is moved with respect to the axial direction of the coaxial center conductor of exterior portion 11, end portion 11a is kept in a favorable connection state with the end portion of the coaxial center conductor of interior portion 12.
Further, in screw member 16 which is moved inside screw hole 17, the tip end abuts on restricting part 18 and movement in the axial direction of screw member 16 is restricted, and therefore, it is not projected to the inside of waveguide 6. Therefore, unintended change in impedance caused by screw member 16 is prevented, and in the inside of waveguide 6, the occurrence of radio frequency arcing in the tip end portion of the screw thread of screw member 16 is also prevented.
The coaxial center conductor of exterior portion 11 is moved in the axial direction of the coaxial center conductor of exterior portion 11, and thereby, the position of end portion 11a connected to the coaxial center conductor of interior portion 12 is moved within moving range R1 (
Finally, the coaxial center conductor of exterior portion 11, whose position in the axial direction of the coaxial center conductor of exterior portion 11 is adjusted, is fixed by screw member 16 being bonded to screw hole 17 by the end portion of screw member 16 being coated with, for example, a coating material, an adhesive or the like.
As described above, in output transition section 1 of this exemplary embodiment, the position of end portion 11a of the coaxial center conductor of exterior portion 11 is made movable within moving range R1 in the inside of waveguide 6 by screw part 13. Thereby, irrespective of variations in the outside dimensions due to machining inaccuracy, dimensional tolerance and the like of the components configuring output transition section 1, the impedance in waveguide 6 can be easily adjusted to an optimal value. Therefore, according to the traveling wave tube which includes output transition section 1, the operation of selectively assembling the components which include the coaxial center conductors of the exterior portions differing in outside dimension is not involved as in the above described related output transition section. Therefore, according to the traveling wave tube according to the exemplary embodiment, the operation of adjusting the impedance in waveguide 6 is simplified, and the manufacturing cost of the traveling wave tube can be reduced.
Next, an output transition section of another exemplary embodiment will be described with reference to the drawings. The other exemplary embodiment has the same basic configuration as in the above described first exemplary embodiment except for the configuration of the coaxial center conductor of the exterior portion which is adjusted by screw part 13, and therefore, explanation will be omitted by assigning the same members with the same reference numerals and characters as in the first exemplary embodiment.
As shown in
The coaxial center conductor of exterior portion 26 is formed to have a predetermined length so that when it is moved in the axial direction of the coaxial center conductor of exterior portion 26 by screw part 131 end portion 26a formed to have a large outside diameter is displaced within moving range R2 in the inside of coaxial connection part 7b of vacuum envelope 7. The coaxial center conductor of interior portion 27 is formed to have a predetermined length corresponding to the length of the coaxial center conductor of exterior portion 26.
In output transition section 2 configured as above, the position of end portion 26a of the coaxial center conductor of exterior portion 26 is moved within moving range R2 in the inside of coaxial connection part 7b of vacuum envelope 7 by moving screw member 16 of screw part 13 as in the operation of adjusting the impedance in the above described first exemplary embodiment. The position of end portion 26a of the coaxial center conductor of exterior portion 26 is moved within moving range R2, and thereby, impedance in the coaxial connection part 7b is adjusted.
As described above, output transition section 2 of this exemplary embodiment is configured so that the position of end portion 26a of the coaxial center conductor of exterior portion 26 is movable within moving range R2 in the inside of coaxial connection part 7b of vacuum envelope 7. Thereby, in output transition section 2, impedance in coaxial connection part 7b of vacuum envelope 7 can be easily adjusted to an optimal value. Therefore, according to the traveling wave tube that includes output transition section 2, the operation of adjusting the impedance in waveguide 6 is simplified, and the manufacturing cost of the traveling wave tube can be reduced.
As shown in
Dielectric 28 is formed into a disk shape by a dielectric material such as, for example, polytetrafluoroethylene, and is disposed at the position adjacent to insulating window member 9. Insertion hole 28a through which coaxial center conductor of interior portion 27 is inserted is provided in a central portion of dielectric 28.
According to output transition section 3 of this exemplary embodiment, by properly changing the outside dimension such as thickness and the material of dielectric 28 when necessary, the impedance is shifted to a relatively large extent, and output transition section 3 can be easily applied to other specifications that have different impedances.
In output transition sections 1, 2 and 3 of the above described exemplary embodiments, the thickness of the sidewall where screw part 13 is provided is formed to be larger as compared with the opposite sidewall in waveguide 6. However, the present invention is not limited to this configuration, and the thickness of the sidewall may be made uniform and only the screw part may be configured to be thicker than the sidewall.
Further, the structure of the coaxial-to-waveguide transition according to the present invention is preferably applied to a traveling wave tube having an output of 1 kW or less, for example, from about several tens W to several hundreds W.
While this invention has been shown and described with particular reference to exemplary embodiments thereof, the invention is not limited to these embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present Invention as defined by the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-101713 | Apr 2007 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 3707647 | Rawls, Jr. | Dec 1972 | A |
| 4144506 | McCammon et al. | Mar 1979 | A |
| Number | Date | Country |
|---|---|---|
| 5-23397 | Mar 1993 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20080246553 A1 | Oct 2008 | US |
