JP2842058B2 - Traveling wave tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traveling wave tube having a waveguide window.

[0002]

2. Description of the Related Art When an RF input or output terminal of a traveling-wave tube is a waveguide, a waveguide window is generally required to seal the inside of the tube in a vacuum-tight manner and to allow electromagnetic waves to pass with low loss. In general, the most frequently used waveguide window is called a pill box window. As shown in FIG. 7, a part of a rectangular waveguide 1 is formed into a circular waveguide 2 and a thin film is formed at the center of the circular waveguide 2. The ceramic disk 3 is air-tightly sealed by brazing.

[0003] TE ₁₀ propagation mode square wave waveguide 1 in this case, a TE ₁₁ circular waveguide 2. The length l of the circular waveguide is about one half of the guide wavelength of the electromagnetic wave to be propagated, and the reflections generated at both ends of the circular waveguide are combined and canceled out, thereby achieving impedance matching and providing a window for the waveguide. Function. Therefore, the best matching can be obtained at the center frequency, and the matching becomes gradually poorer as the distance from the center frequency increases.

Further, as shown in a typical example of the impedance matching characteristic in FIG.
There is a resonance mode called a mode. In FIG. 8, there are ghost modes at frequencies of 5.3 GHz, 5.7 GHz, 6.85 GHz and 7.3 GHz. Therefore,
The usable band is constrained in the ghost mode, and in the case of FIG. 8, the frequency band between the frequency of 5.7 GHz and 6.85 GHz is 1.
10 GHz. This is about 20% in the fractional band. In the actual design of the pillbox window, each part is dimensioned so that it is matched within the required band and there is no ghost mode.

[0005]

Since the pillbox window has a large allowable passing power, it is often used as an output window of a microwave tube having a relatively large output. However,
When used at ghost mode frequencies, it resonates in the pillbox window and its electromagnetic energy is trapped in the window, resulting in excessive heat generation. When the passing power is large, the heat generated in the ceramic disk by the heat generation exceeds the breaking limit, and the ceramic disk may be broken. Especially in the case of traveling wave tubes, the amplification band is wide, and considerable output is obtained even when used outside the specified operating band.
The pillbox window breaks and the hermetic seal is compromised. Therefore, all functions of the traveling wave tube are lost. Since traveling wave tubes, especially high power traveling wave tubes, are expensive, it is strongly desired to prevent such accidents from the viewpoint of economy.

In order to overcome such a problem, a person skilled in the art, of course, must obey the handling restriction that the conventional traveling wave tube is never operated outside the specified operating frequency band. Have been protected. However, it is unavoidable that a ghost mode frequency may be erroneously input to the traveling wave tube due to erroneous handling or a failure of the device.

As another countermeasure, it is conceivable to create a pillbox window in which there is no ghost mode or the ghost mode is separated from a specified operating frequency band to a point where there is no practical problem. However, this has the drawback that a slightly complicated structure is required and the allowable passing power is inferior.

[0008]

SUMMARY OF THE INVENTION The traveling wave tube of the present invention has an R
A traveling-wave tube having a structure in which the F input terminal is a coaxial window and the RF output terminal is a waveguide having a pillbox window was housed in a case composed of a substrate and a case cover, and attached to the case cover. In a traveling wave tube having a structure in which an input coaxial connector and an RF input coaxial window of a traveling wave tube are connected by a coaxial cable, a ghost mode filter is inserted between the input coaxial connector and the RF input coaxial window. Are connected by a coaxial cable.

The ghost mode filter is composed of a coaxial line, and a coaxial resonator is provided in parallel with the main coaxial line. One end of an inner conductor of the coaxial resonator is formed in the main coaxial line. It is characterized in that it is connected to a conductor and the other end is short-circuited at a position which is an integral multiple of about one-half the wavelength of the ghost mode frequency in the pillbox window.

The ghost mode filter is constituted by a coaxial line, and a coaxial resonator is provided in parallel with the main coaxial line. One end of an inner conductor of the coaxial resonator is connected to the main coaxial line. Place a gap and close to the conductor,
It is characterized in that the other end is short-circuited at an odd multiple of about one fourth of the wavelength of the ghost mode frequency of the pillbox window.

[0011]

The ghost mode filter can sufficiently attenuate the ghost mode frequency component of the RF input signal. Therefore, even when a ghost mode frequency signal is input, the signal enters the traveling wave tube as a sufficiently attenuated minute signal, so that the output level of the traveling wave tube becomes minute and the pillbox window is broken. Such a thing does not occur.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 shows a traveling wave tube according to an embodiment of the present invention, particularly a traveling wave tube of a periodic permanent magnet focusing and forced air cooling type. FIG. 1 (a) is an external perspective view, and FIG. 1 (b) is a case cover. FIG. 3 is a view of the upper part of the device viewed from above with a cutout. The traveling wave tube tube 11 includes an electron gun 12, a slow wave circuit 13 surrounded by a periodic magnetic field focusing device, a collector 14, an RF input terminal 15, and an RF output terminal 16. This tube is supported and fixed on a case substrate 17 by a slow wave circuit support base 18 and a collector support plate 19. The case cover 20 covers the whole, and a lead wire 21 for supplying power to each electrode is provided outside the case cover 20.
And RF input / output terminals 22 and 16 are drawn out. Cooling air suction port 2 for forced air cooling is provided in case substrate 17.
3. A discharge port 24 is provided in the case cover 20.

The RF output terminal 16 is a rectangular waveguide flange, and a pillbox window 25 is provided in the middle of the rectangular waveguide. The RF input terminal 22 is a coaxial connector, the input terminal 15 of the tube 11 is a coaxial hermetic window, and a ghost mode filter 31 is inserted between the two.
Each is connected by a coaxial cable 26. The ghost mode filter 30 is fixed on the case substrate 17.

FIG. 2 shows a ghost mode used in the present invention.
It is a figure which shows the 1st Example of a filter, The figure (a) is an external appearance perspective view, and the figure (b) is a sectional view. A groove 34 for the main coaxial line 33 and a groove 36 for the coaxial resonator 35 are provided in the metal block 32 in a direction perpendicular to the groove 34.
7, 38 are provided. At both ends of the main coaxial line 33, coaxial connectors 39 are attached as input / output terminals. The inner conductor 38 for the coaxial resonator 35 is the inner conductor 37 of the main coaxial line 33.
The other end of the coaxial line is short-circuited and terminated by a metal component 40 slidable in the axial direction. The metal plate 41 covers the metal block 32 and is fixed with screws 42, and forms a part of the outer coaxial conductor. The metal plate 43 is a cover that covers the groove 36.

In such a configuration, an RF input signal applied to the traveling-wave tube is input from one coaxial connector 39, propagates through the main coaxial line 33, and is transmitted through the other coaxial connector 3.
9 and input to the traveling wave tube 11. In this embodiment, a coaxial resonator 35 is connected in parallel with the main coaxial line 33.
Are provided. The coaxial resonator 35 resonates at a frequency at which the coaxial line length m is an integral multiple of about one-half the wavelength of the signal wave, and RF energy is trapped therein. The frequency characteristic of the RF signal has a dip 4 at this resonance frequency as shown in FIG.
4 results. The depth h and the width Δf of the dip 44 depend on the characteristic impedance and loss of the coaxial line of the coaxial resonator 35 and the degree of coupling with the main coaxial line 33. By matching this resonance frequency to the ghost mode frequency of the pillbox window, this frequency component of the RF input signal can be attenuated. The necessary frequency width and attenuation can be obtained by appropriately selecting the above parameters. One method of increasing the amount of attenuation is to set the resonance frequencies of the plurality of coaxial resonators 35 to the same frequency.

FIG. 4 shows a ghost mode used in the present invention.
FIG. 6 is a sectional view showing a second embodiment of the filter. In this embodiment, the coaxial resonator 3 is used to increase the depth of the dip characteristic.
5 is characterized in that the degree of coupling to the main coaxial line 33 is reduced. For this reason, the inner diameter of the outer conductor 45 at the coupling portion of the coaxial resonator 35 is reduced. The rest is the same as FIG.

FIG. 5 shows a ghost mode used in the present invention.
FIG. 7 is a cross-sectional view of a third embodiment of the filter. In this embodiment, the inner conductor 38 'for the coaxial resonator 35 is arranged with a gap between and adjacent to the inner conductor 37 of the main coaxial line 33, and the coaxial line length m is approximately one quarter of the wavelength of the signal wave. It resonates at a frequency that is an odd multiple of. Other configurations are shown in FIG.
This is the same as the embodiment.

FIG. 6 shows a ghost mode used in the present invention.
FIG. 9 is a sectional view of a fourth embodiment of the filter. In this embodiment, the main coaxial line 3 of the coaxial resonator 35 is used in order to easily adjust the center frequency, width and depth of the dip of the dip characteristic.
3 is characterized by a high degree of coupling. For this purpose, a disk 46 is attached to the tip of the inner conductor 38 'of the coaxial resonator 35. Other than this, it is the same as FIG.

The resonance frequency of the coaxial resonator 35 depends on the proximity of the inner conductor 38 'to the inner conductor 37 or the metal component 40.
Is adjusted to a desired value. After the adjustment, it is fixed using screws, an adhesive or the like. In the above embodiment, the metal component 40 is slidable for adjusting the resonance frequency.
A method in which the inner conductors 38, 38 'and the metal component 40 are formed as an integral metal component and the coaxial line length m is selected to a desired value has the same operation and effect, and is of course included in the scope of the present invention. is there.

[0020]

As described above, according to the present invention, by inserting a ghost mode filter at the input side of the traveling wave tube, the ghost mode frequency of the pillbox window can be reduced.
The F input signal can be sufficiently attenuated and prevented from entering the traveling wave tube. As a result, even if the ghost mode frequency RF input signal is accidentally input to the traveling wave tube, the pillbox window does not break. That is, even if a ghost mode frequency is applied to the traveling wave tube due to an erroneous operation or a device failure, the expensive traveling wave tube is not broken. Therefore, there is an effect that reliability and economy have been improved. The ghost mode filter can be manufactured at low cost because it is constituted by a coaxial line.

[Brief description of the drawings]

1A and 1B show a traveling wave tube according to an embodiment of the present invention, wherein FIG. 1A is an external perspective view, and FIG.

2A and 2B show a first embodiment of a ghost mode filter used in the present invention, wherein FIG. 2A is an external perspective view, and FIG. 2B is a cross-sectional view.

FIG. 3 is a characteristic diagram of a ghost mode filter.

FIG. 4 is a sectional view showing a second embodiment of the ghost mode filter used in the present invention.

FIG. 5 is a sectional view showing a third embodiment of the ghost mode filter used in the present invention.

FIG. 6 is a sectional view showing a fourth embodiment of the ghost mode filter used in the present invention.

FIG. 7 is a diagram showing a structure of a pill box window.

FIG. 8 is a diagram showing typical impedance matching characteristics of a pillbox window.

[Explanation of symbols]

 Reference Signs List 11 traveling wave tube 15 RF input terminal (coaxial window) 16 RF output terminal 17 case substrate 20 case cover 22 RF input terminal (coaxial connector) 25 pill box window 26 coaxial cable 31 ghost mode filter 33 main coaxial line 35 Coaxial resonator 37, 38, 38 'Inner conductor 40 Metal part

Claims (4)

(57) [Claims] A traveling wave tube having a structure in which an RF input terminal is a coaxial window and an RF output terminal is a waveguide having a pillbox window is housed in a case comprising a substrate and a case cover, In a traveling wave tube having a structure in which an input coaxial connector attached to the case cover and an RF input coaxial window of the traveling wave tube are connected by a coaxial cable, a ghost is provided between the input coaxial connector and the RF input coaxial window. A traveling wave tube having a mode filter inserted therein and connected to each other by a coaxial cable. Wherein said ghost mode filter is constituted by a coaxial line, traveling-wave tube according to claim 1, characterized in that a coaxial resonator in parallel with this main coaxial line. 3. The inner conductor of the coaxial resonator has one end connected to the inner conductor of the main coaxial line and the other end being an integral multiple of about one half of the wavelength of the ghost mode frequency of the pillbox window. 3. The traveling-wave tube according to claim 2, wherein a short-circuit is terminated at a position. 4. The inner conductor of the coaxial resonator has one end arranged with a gap and close to the inner conductor of the main coaxial line,
3. The traveling wave tube according to claim 2, wherein the other end is short-circuited at an odd multiple of about a quarter of the wavelength of the ghost mode frequency of the pillbox window.