JP3512993B2 - RF amplifier tube and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to micro-amplifier tubes such as traveling wave tubes or klystrons, and more particularly to integrated pole-piece RF amplifier tubes for amplifying microwave signals in the millimeter wave range. It relates to a manufacturing method.

[0002]

Microwave amplifier tubes such as traveling wave tubes (TWT) or klystrons are well known in the art. These microwave tubes are adapted to amplify, or increase the gain, of RF (radio frequency) signals within the microwave frequency range.

Coupled cavity TWTs generally have a series of tuning cavities that are linked or coupled by an iris formed between the cavities. Microwave RF introduced in the tube
The signal travels in the tube as it passes through each of the coupling cavities.

A typical coupled cavity TWT may have as many as 30 cavities thus formed. When the RF signal travels in the pipe, the path that the RF signal follows bends in a zigzag shape, so that the effective speed of the traveling wave signal decreases and the signal is affected.

The slow waves formed by this type of coupled cavity tube are known as "slow waves."

Each cavity is further linked by a beam tunnel which increases the length of the tube. Amplified RF
To generate the output signal, the electron beam must be emitted as it passes through the beam tunnel. This electron beam is guided by the magnetic field formed in the tunnel region and interacts with the RF signal to provide the desired amplification.

The resulting frequency bandwidth of the RF output signal can be changed by changing the size of the cavity, and the intensity of the RF output signal can be changed by changing the voltage and current of the electron beam.

RF amplifier tubes can utilize either "integral pole pieces" or "slip-on pole pieces". The pole piece is formed of a magnetic material that conducts magnetic flux to the beam tunnel. The integral pole piece forms part of a vacuum vessel which extends inwardly towards the beam region, while the slip-on pole piece lies completely outside the tube's vacuum vessel.

The magnetic field induced in the tunnel region is obtained by magnetic flux lines extending radially through the pole pieces from a magnet located outside the tube region. This type of electron beam focusing method is known as the Periodic Permanent Magnet (PPM) focusing method.

If the pole pieces form part of the tunnel as well as the cavity walls, a magnetic flux will be created in the beam region. Therefore, the beam stiffness value, that is, λ
_p / L becomes large, and favorable conditions for beam focusing are obtained. For this reason, integral pole piece RF amplifier tubes are preferred over slip-on pole piece tubes.

The klystron is similar to the coupled cavity TWT in that it may include multiple cavities through which the electron beam passes. The klystron amplifies the modulation into the electron beam and produces a highly bunched beam containing RF current.

The klystron differs from the coupled cavity TWT in that the cavities are generally uncoupled. However, part of the klystron cavity is 2
One or more cavities may be coupled so that they can interact with the electron beam. This particular type of klystron is known as an extended interaction output circuit.

[0013]

A major problem with RF amplifier tubes is the efficient removal of heat. As the electron beam drifts through the cavity of the tube, the thermal energy generated from the stray electrons stopped at the tunnel wall prevents reluctance changes in the magnetic material, thermal deformation of the cavity surface, or melting of the tunnel wall, Must be removed from the tube.

To remove this heat, a copper plate is usually bonded to a portion made of a magnetic material that transfers heat to a heat sink. This copper lowers the thermal resistance of the heat path, making the tunnel strength below dangerous levels. The minimum heat path length in a typical cylindrical cavity is the cavity radius.

Another problem with RF amplifier tubes is that they can be manufactured to amplify RF signals, or millimeter waves, in the millimeter wavelength range of the microwave spectrum.
It will be more difficult. These very short wavelength signals require precise tolerances in forming the cavities and coupling notches.

In the periodic microwave structure, (R
As a result of the greater variation in the inner dimension (as viewed from the F field) with each cycle, the number of RF reflections in the tube increases. Then, for this reason, the impedance matching between the tube and the RF input waveguide deteriorates, and the value representing the periodicity becomes lower than that in the case where the matching deterioration does not occur.

As a result of these factors, the gain value obtained with the tube is reduced. Therefore, as the frequency increases, the nominal dimension of the component decreases, and the dimensional variation from cycle to cycle must be reduced.

In conventional unitary pole piece RF amplifier tubes, the magnetic and non-magnetic components are usually machined separately, laminated and then brazed. In tubes designed to operate at millimeter wavelengths, the dimensional variations from cycle to cycle are often determined by the tolerances required for this part as well as the non-uniformity of the braze area between the parts.

At higher frequencies, where more periods are usually needed, and thus more components are required, especially if copper plates have to be added to the pole pieces to improve the thermal conductivity along the cavity walls. Eliminating the accumulation of tolerances along is more difficult and costly.

Therefore, the unitary pole-piece type RF amplification tube becomes less effective as the operating frequency increases and as the number of parts increases. Tubes are often machined from a single block of copper using electrical discharge machining techniques to eliminate dimensional variation problems. If light PPM focusing is desired, then the tube is slipped on and brazed with another magnetic circuit.

However, the elimination of the integral pole piece and, consequently, the introduction of magnetic flux into the tunnel wall detracts from the desired focusing performance of the integral pole piece RF amplifier tube. The λp / L ratio is significantly reduced and only higher beam voltages can be focused.

Therefore, to achieve the desired beam focus,
It would be desirable to provide an integral pole piece RF amplifier tube having a pole piece extending completely or at least partially to the tunnel wall and for amplifying millimeter wave RF signals.

It is further desirable to provide an integral pole piece RF amplifier tube in which the copper plate contacts the pole piece along the cavity wall to improve heat removal from the tunnel wall.

Further, it is preferable to provide a relatively inexpensive method of manufacturing an integral pole piece type RF amplification tube having the above characteristics and eliminating the adverse effect of accumulating tolerances.

[0025]

SUMMARY OF THE INVENTION Accordingly, a primary object of the present invention is to provide an integral pole piece configuration having a pole piece extending to the tunnel wall for amplifying millimeter wave RF signals and for improved beam focusing. An object is to provide an RF amplification tube and a manufacturing method thereof.

Another object of the invention is to have a copper plate that amplifies the millimeter wave RF signal and contacts the pole pieces along the cavity wall to improve heat resistance and possible cavity surface resulting from high temperature operation. To provide an integral pole piece RF amplifier tube that minimizes thermal deformation, magnetic material reluctance changes, and tunnel wall melting.

Yet another object of the present invention is to provide a low cost method for manufacturing an integral pole piece RF amplifier tube which eliminates the deleterious effects of tolerance accumulation.

To achieve the above and other objectives, an RF amplification tube having a laminated structure having a plurality of magnetic and non-magnetic plates alternately and integrally provided is provided.

The structure has a substantially planar outer surface and an inner beam tunnel. A plurality of magnets are provided that form a magnetic field in which the magnetic flux first passes through the magnetic plate and then enters the tunnel. The edge of this structure is provided with a planar surface to allow attachment of a planar boundary heat sink to the circuit.

Each of the non-magnetic plates has one or more slots that are resonant cavities after the heat sink is attached.

A beam tunnel penetrates each magnetic plate and allows each electron beam to pass through each cavity. The planar structure provides a low cost structure and the required bandwidth for RF amplification. The non-magnetic plate contributes to the removal of heat from this structure.

In the first embodiment of the present invention, notches are provided in a part of the magnetic plate, and these notches connect the cavities. The positions of these notches are alternating between a first edge coinciding with the first planar surface and a second edge coinciding with a second planar surface opposite the first planar surface.

Alternatively, the positions of the notches may all coincide with one planar surface, or the first portion of the notch may coincide with the first planar surface and the second portion of the notch. The arrangement examples of the former and the latter may be combined so as to coincide with the second planar surface.

In various embodiments of the present invention, the RF amplifier tube forms a coupled cavity traveling wave tube.

In the second embodiment of the invention, notches are not provided and the cavities remain uncoupled. In this embodiment, the RF amplification tube will form a klystron.

The method for manufacturing the RF amplification tube according to the present invention is such that an integrally formed laminated structure is obtained.
The process includes alternately combining a plurality of magnetic plates and non-magnetic plates.

Notches partially entering adjacent non-magnetic plates can be cut into predetermined ones of the magnetic plates. The edges thus selected may alternate between the first side of the structure and the second side opposite this first side, or all along one side. .

Next, one or more slots are cut through a given one of the non-magnetic plates. When a planar heat sink is provided on the side surface of this structure, the slot becomes a tuning cavity and the notch couples these cavities.

Those of ordinary skill in the art will study the following detailed description of the preferred embodiment, and as to other advantages and purposes of the present invention, as well as the construction of the present invention integral pole piece RF amplifier tube for millimeter wave frequencies. I think I can understand it more completely. Next, description will be given with reference to the accompanying drawings.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIGS.

In these figures, the RF amplifier circuit according to the present invention is shown. The tube 10 is formed of a laminated structure that includes a plurality of non-magnetic plates 18 and
It consists of magnetic plates 16 which are alternately assembled and integrally formed. The assembled tube 10 is elongated and has a rectangular shape as a whole, and the end plates 12 arranged at both ends and the first side surface 23 are provided.
And a second side surface 25 opposite to the first side surface 23 and a third side surface 25.
It has a side surface 27 and a fourth side surface 29 opposite to the third side surface 27.

As will be described later, the electron beam generated at one end of the tube 10 passes through a plurality of cavities formed in the TWT and exits from the opposite end of the TWT.

Magnetic plate 16 and non-magnetic plate 18
Is rectangular as a whole. Magnetic plate 16
A preferred material for iron is iron.

Magnetic plate 1 also known as pole piece
6 has a notch 22 located at the edge. The notch 22 shown in the figure has a rectangular shape as a whole and extends in the width direction of the pole piece by a length shorter than half. However, it is known that other notch shapes, for example circular shapes, can also be used to advantage.

The positions of the notches of each magnetic plate 16 are alternately provided between the edge on the first side surface 23 side and the edge on the second side surface 25 side.

As best shown in FIG. 4, the position of the notch 22 of the first magnetic plate 16 ₁ is on the first side surface 23, and the notch 22 of the next magnetic plate 16 ₂ is provided on the second side surface 25. Has been. The notch 22 of the third magnetic plate 16 ₃ is similar to the first magnetic plate 16 _{1 in} the first notch 22.
Located on side 23.

Unlike the above, the position of the notch depends on the TWT.
10 may be all on one side or notch 2
Two arrangement examples may be combined such that a part of 2 is on the first side surface 23 and a part of the 2 is on the second side surface 25.

As a further alternative, the single magnetic plate 16 may have more than one notch 22, for example notches provided at opposite ends of the pole piece.

As will be described below, these notches provide coupling paths for adjacent cavities.

The non-magnetic plates 18 are provided adjacent to the magnetic plate pole pieces 16 and are provided alternately with the pole pieces. The preferred material for the non-magnetic plate 18 is copper.

The non-magnetic plate 18 has one or more slots 24. The slot 24 has a parallelepiped shape as a whole, and from the first side surface 23 to the second side surface 25,
It completely penetrates the non-magnetic plate 18. Slot 2
The shape of 4 may be elliptical in cross section.

Unlike the above, the slot 24 may extend between the third side surface 27 and the fourth side surface 29. The directions of the slots may alternate between a first direction extending between the first side surface 23 and the second side surface 25 and a second direction extending between the side surfaces 27 and 29. These slots 24.
The tuning cavity 26 is constructed.

Since the magnetic plates 16 and the non-magnetic plates 18 are alternately arranged so as to be integrated, the tube 10
A continuous path is formed therein, which passes through each cavity, crosses over each notch, and extends to an adjacent cavity. This path is also shown in the cross-sectional view of FIG.

An electron beam tunnel 14 is completely penetrated in the longitudinal direction of the tube 10. The overall shape of this tunnel 14 is circular and passes through and links the cavities 26. This beam tunnel constitutes a path for the electron beam to pass through the completed coupled cavity tube 10.

Cavity 26 is coupled by notch 22 as described above, and tube 10 acts as a coupled cavity traveling wave tube amplifier. During operation, the electron beam
It interacts with the RF signal passing through the coupling cavity.
The energy from the beam is transferred to the RF signal,
Increase the power of the signal.

Magnetic plate 16 and non-magnetic plate 1
8 has an edge that is flush with the first side surface 23 and the second side surface 25. As will be described later, the first side surface 23 and the second side surface 23
The side surface 25 is a flat surface 32, 32 'for mounting the heat sink 34.

The third side surface 27 and the fourth side surface 29 are flush with some other edges of the non-magnetic plate 18 and the magnetic plate 16. However, the individual magnetic plates 16 extend outwardly from the third side surface 27 and the fourth side surface 29 and form the ears 36. The combination of the side surface and the ear portion 36 determines the attachment position for installing the magnet 42. The magnet 42 shown in FIG.
Is substantially rectangular, but may have other shapes, for example cylindrical.

As shown in FIG. 2, the magnet 42 has a T
Mounted in a mounting position with respect to the WT 10, the magnetic flux lines 44 form a magnetic field through the magnetic plate 16. The magnetic flux lines penetrate the magnetic plate 16 and the non-magnetic plate 1
8 and jumps into the adjacent magnetic plate 16. The magnetic flux lines 44 also traverse the beam tunnel 14 and focus the electron beam.

Next, the magnetic flux line 44 jumps over the space formed by the notch 22, passes through the adjacent cavity 26 again, and returns to the first magnetic plate 16. Here, the shape of the slot 24 and the notch 22 can be changed to bring the surface 32 of the heat sink closer to the beam tunnel 14 to further improve the heat treatment capability of the tube 10.

Next, referring to FIG. In this figure, the tube 10
There is shown another embodiment in which a Klystron operation can be performed. Notches are not provided in a part of the magnetic plate 16.

As the electron beam passes through the tube 10, an electromagnetic field is formed in the cavity 26, which produces an RF signal. As is known in the art, a portion of cavity 26 is coupled by notch 22 and can operate as an enhanced interactive output circuit with improved bandwidth.

To assemble the RF amplification tube 10 according to the present invention, a laminated structure of magnetic and non-magnetic plates of generally rectangular shape must be formed. The magnetic and non-magnetic plates have central alignment holes. Each alignment hole has
A thin molybdenum tube was inserted to allow alternating plates to be aligned.

Once the plates are assembled, they are integrally formed into a laminated structure by brazing or other joining technique. Each non-magnetic plate has a pilot hole 52 extending from the edge associated with the first side surface 23 to the edge associated with the second side surface 25. In Figure 3,
An example of the pilot hole 52 of the non-magnetic plate 18 before assembly is shown.

When the magnetic plate and non-magnetic plate structures are brazed together to form an integral unit, the pilot holes 52 penetrate the width of the structure to cut out cavities as described below. It is a mechanism of.

The next step is to reduce the exposed edges of the rectangular tube 10 to the proper shape. After making the sides square, the desired notches 22 are cut in the sides 23 and 25. These notches extend completely across the thickness of the magnetic plate 16 and extend partially into each adjacent non-magnetic plate 18. As is known in the art, the preferred cutting technique will depend on the tolerance requirements desired.

After forming the notch 22, the cavity 26
Cut out. The preferred method of cutting these cavities 26 is wire electron discharge machining (EDM).
When using this technique, one wire is fed through the pilot hole 52 and the unwanted copper material is cut away to leave the slot 24 without cutting the cavity wall.

By repeating this process, the cavity 26 is formed in the tube 10. After forming the cavity 26, a continuous path results from the notch 22 joining the cavity 26.

Then, using the wire EDM method, the first
Side 23 and second side 25 are at right angles and heat sink surfaces 32, 32 'are provided. The wire EDM method can also be used to remove the side portions of the magnetic plate 16 and non-magnetic plate 18 leaving only the exposed ears 36. If desired, this last step can be performed leaving ears every three pole pieces, as shown in FIG. 1, or every two pole pieces, as shown in FIG.

The molybdenum tube is also removed by this wire EDM method and a machine tool is used to form the electromagnetic beam tunnel 14.

The final step in forming the tube 10 is to provide the end plate 12 with inlet and outlet ports. RF signals are input to the tube 10 at these ports,
And it is for making it possible to output from the tube. These ports can also be formed by conventional milling or EDM methods. The finished TWT 10 may have a heat sink 34 secured to the heat sink surface 32.

To use the integral pole piece RF amplifier tube 10, the tube and other similar circuits must be assembled into a complete amplifier assembly. A matching circuit can be added to the finished coupled cavity tube 10 to match the RF impedance between the RF input port and the tube itself. The matching circuit is a combined cavity tube 1.
It is usually machined to be part of zero.

Next, the tube 10 can be combined with other tube portions as shown in FIG. 7 to form the electron gun 62 and the electron beam collector 64. The electron gun 62 has a cathode 63 that is heated to emit electrons. These electrons are focused into an electron beam 66 by the magnetic field provided in the beam tunnel 14 of the tube 10. The collector 64 receives these electrons and dissipates them after they leave the tube 10.

Those skilled in the art will appreciate that using laminate structures and RF amplifier tubes with generally flat surfaces,
It will be clear that manufacturing is relatively low cost. The copper plates that form the slots provide additional heat robustness by transferring heat from the beam tunnel to the heat sink. In addition, a desired millimeter wave frequency band can be accurately obtained without accumulating errors.

Now that the preferred embodiment of a coupled cavity traveling wave tube for millimeter wave frequencies has been described, it will be apparent to those skilled in the art that the above objects and advantages of the present invention may be obtained. It will be apparent to those skilled in the art that various modifications, adaptations and other embodiments can be made within the spirit and scope of the present invention.

For example, instead of the wire EDM method, other precision cutting methods such as milling or drilling can be used. As is known in the art, the frequency range of the RF signal to be amplified determines the component size. These magnitudes can vary significantly when considering different RF frequency signals and RF levels.

Further, when desired tube characteristics are desired, the slot 24 is provided in the pole piece 16 as in the non-magnetic plate 18.
It is also clear that the notches 22 can be provided in the non-magnetic plate as well as the pole pieces. The non-magnetic plate 18 or the magnetic plate 16 can also be provided with a large number of slots 24.

[Brief description of drawings]

FIG. 1 is a perspective view of an integral pole piece RF amplifier tube according to the present invention.

FIG. 2 is a partial perspective view of an integral pole piece type RF amplification tube showing magnetic flux lines and heat flux lines.

FIG. 3 is a perspective view of an unassembled non-magnetic plate with exposed pilot holes.

FIG. 4 is an exploded view of the integral pole piece RF amplifier tube of FIG.

5 is a sectional view of the inside of the integral pole piece type RF amplification tube taken along the line 5-5 of FIG.

FIG. 6 Integral pole-piece RF for klystron operation
It is a partial perspective view of an amplification tube.

FIG. 7 is a side sectional view of an RF amplification tube assembled to an electron gun and a collector.

[Explanation of symbols]

10 tube 14 beam tunnel 16 Magnetic plate 18 Non-magnetic plate 22 notches 24 slots 23, 25, 27, 29 Side surface 26 Cavity 32, 32 'Surface 34 Heat sink 36 ears 42 magnets 44 magnetic flux line 52 pilot hole 62 electron gun 63 cathode 64 collector 66 electron beam

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Douglas B. Lion USA California 94070 San Carlos Northam Avenue 48 (56) References JP 63-34836 (JP, A) JP 58-188033 (JP, A) ) JP-A-55-154036 (JP, A) JP-A-4-118836 (JP, A) JP-B-44-20167 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01J 9/14 H01J 23/00-23/54

Claims (2)

(57) [Claims] 1. A method of manufacturing an integrally pole piece coupled cavity type traveling wave tube for amplifying a millimeter wave RF signal, wherein a plurality of magnetic plates and non-magnetic plates are assembled alternately to form a laminated structure. An integral pole-piece coupled cavity type traveling wave including the steps of integrally forming the plate on at least one side surface of the laminated structure and cutting a cavity in the laminated structure. Pipe manufacturing method. 2. An integral unit for amplifying a millimeter wave RF signal.
It is a method to manufacture a pole piece coupled cavity type traveling wave tube.
To set up multiple magnetic plates and non-magnetic plates alternately.
That, integrally forming the plate such that the laminated structure, cutting a cavity in the laminated structure, manufactured integral pole piece coupled cavity type traveling wave tube having a step
Build method.