JPS5849565Y2 - Metal-ceramic traveling wave tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a metal-ceramic traveling wave tube whose outer envelope is composed of metal and ceramic parts.

Traveling wave tubes are widely used as amplifier tubes in microwave communication equipment because of their characteristics of wide band, high gain, and high efficiency.

FIG. 1 is a cross-sectional view of an example of a conventional metal-ceramic traveling wave tube in which the input/output circuit is coaxially coupled.

A conventional traveling wave tube will be explained below based on FIG.

The tube 1 mainly consists of an electron gun 11 that emits an electron beam, a slow wave circuit 12 that interacts the electron beam with a high frequency, and a collector 13 that captures the electron beam.
2 is housed together with a slow-wave circuit support rod 15 inside an elongated metallic outer tube 14 that forms a part of the vacuum envelope of the bulb 1 .

The periodic magnetic field device 31 is constructed by alternately combining cylindrical permanent magnets and magnetic pole pieces, and is arranged coaxially with the tube for electron beam focusing.

The high frequency input is transmitted from the input coaxial circuit 16 attached to the end of the outer tube 14 to the slow wave circuit 12, interacts with the electron beam, is amplified as it propagates on the slow wave circuit 12, and is output as a high frequency output from the coaxial It is taken out from the circuit 17.

The electron gun 11 includes an anode, a Wehnelt electrode, and a cathode electrode, each of which is connected to an external power source (not shown) through a high-voltage lead wire 21 insulated from each other by a ceramic component 18, and to the collector 13 through a high-voltage lead wire 22. A high voltage is supplied from 1), and the slow wave circuit is set to ground potential.

In order to improve the overall efficiency of the traveling wave tube, it is common to lower the voltage at the collector 13 below the slow wave circuit voltage, and the collector 13 is usually insulated from the slow wave circuit 12 by a cylindrical ceramic 19.

A heat dissipation block 24 having an insulating plate 23 in the middle is attached around the collector 13 for cooling the collector.
The tube 1 including the periodic magnetic field device 31 is housed in a metal case 32.

In order to prevent the tube 1, the magnetic field focusing device 31, and the heat dissipation block 24 from being misaligned with each other, the metal case 3
2, a solid agent 3 made of resin or the like is inserted into the gap in the metal case 32 through an injection hole 33.
4 is filled.

After the solid agent 34 is solidified, the injection hole 33 is sealed with a metal lid (not shown) or the like.

In recent years, there has been a demand for traveling wave tubes with particularly high gain and high efficiency in the design of communication equipment that uses traveling wave tubes as amplifier tubes. If we tried to achieve high efficiency, we would encounter the following problems.

That is, in order to increase the gain of the traveling wave tube and operate it stably, it is necessary to prevent the leakage high frequency power leaking from the output side of the traveling wave tube from returning to the input end of the slow wave circuit 12. In the structure shown in the figure, a part of the amplified high-frequency output passes through the output end of the outer tube 14 and passes through the cylindrical ceramic 19.
It leaks from the metal case 32 and is transmitted through the path 41 between the periodic magnetic field device 31, enters the bulb 1 from the ceramic component 18, passes inside the input end of the outer tube 14, and returns to the input end of the slow wave circuit 12. However, there are disadvantages such as making the operation of the traveling wave tube unstable, deteriorating the high frequency characteristics, and sometimes causing self-oscillation.

In addition, leakage from the cylindrical ceramic 19 occurs and the metal case 3
A part of the high-frequency power transmitted through the path 41 between the periodic magnetic field device 31 and the periodic magnetic field device 31 passes through the path 42 and is radiated to the outside as unnecessary radio waves via the high-voltage lead wires 24 and 25, and is transmitted to other devices in the microwave communication device. In order to obtain a particularly highly efficient traveling wave tube, it is necessary to lower the collector voltage to an extremely lower level than the voltage of the slow wave circuit.
In order to ensure sufficient insulation of the cylindrical ceramic 19, the dimensional length of the cylindrical ceramic 19 must be increased, which increases the leakage high frequency power from the cylindrical ceramic 19, and there is a possibility that the above-mentioned drawbacks will occur significantly. Ta.

Conventionally, as a method to eliminate this kind of inconvenience, a method was proposed in which an insulating plate was used near the collector 13 to form a high-frequency bus capacitor to bypass the leaked high-frequency power and prevent it from returning to the input side. 44-20651
)It has been known.

However, in order to obtain sufficient capacitor capacity, the insulating plate, which also has the function of insulating the slow-wave circuit and the collector, must be considerably stiffened, and if the potential difference between the collector and the slow-wave circuit is large, sparks may occur. Cheap.

Therefore, it is difficult to obtain sufficient microwave attenuation.
It was unsuitable for high gain and high efficiency traveling wave tubes.

Therefore, the purpose of the present invention is to eliminate the above-mentioned drawbacks of conventional traveling wave tubes with a simple structure, effectively prevent self-oscillation caused by unnecessary feedback of high-frequency power, characteristic deterioration, etc., and prevent unnecessary radio waves from flowing outside the traveling wave tube. An object of the present invention is to provide a metal-ceramic traveling wave tube that prevents radiation of radiation.

An embodiment of the present invention will be explained below based on FIG.

The same reference numerals are used for the same or corresponding parts as in FIG. 1.

The tube 1 has an electron gun section 11 inside the outer container, just like the conventional type.
, a slow wave circuit 12, a collector 13, etc., and the tube 1 is provided with a periodic magnetic field device 31 for electron beam focusing and a heat radiation block 24 for cooling the collector.

The cylindrical ceramic 19 interposed between the output side end of the outer tube 14 and the collector 13 is selected to have a length that can sufficiently withstand the potential difference between the slow wave circuit 12 and the collector 13.

In the present invention, radio wave shielding bodies 35, 36.37 in the form of non-magnetic metal plates are placed on the outer peripheral surface of the periodic magnetic field device 31 composed of a cylindrical permanent magnet and magnetic pole pieces.
The inner and outer circumferences of the solid agent 7 are in contact with the outer surface of the periodic magnetic field device 31 and the inner surface of the metal case 32, respectively, and are interposed between the solid agents 34.

With this structure, the high-frequency power leaking from the cylindrical ceramic 19 is blocked by the radio wave shields 35, 36, 37, and the high-frequency power leaking to the electron gun side is eliminated or greatly reduced as a traveling wave. The operation of the tube does not become unstable, self-oscillation can be prevented, and radiation of unnecessary radio waves to the outside of the traveling wave tube is improved.

That is, the leaked high-frequency power is reflected toward the collector side by the radio wave shield 35 closest to the collector side, but when the operating frequency becomes as high as several GHz, the leakage high-frequency power is reflected by the inner and outer peripheral surfaces of the shield member 35, the outer peripheral surface of the periodic magnetic field device 31, and the metal. A portion of the high frequency power leaks through a small gap between the case 32 and the inner wall.

However, the leaked high-frequency power is reflected by the shield 36 and further by the shield 3T, and the high-frequency power leaked to the electron gun side through the path 41 is reduced.

When the interval between the radio wave shields 35, 36, and 37 is selected to be λ/4, where λ is the wavelength of the operating frequency, the high frequency power is reduced most.

Of course, if the number of radio wave shields 35.degree.

The required number of radio wave shields 35, 36 and 37 varies depending on the magnitude of the high frequency power leaking from the cylindrical ceramic 19 and the gain of the traveling wave tube, but two to three radio wave shields are sufficient to prevent leakage high frequency power. It can be prevented.

It is practical to arrange the radio wave shield as follows.

That is, the injection hole 3 is located at the tip of the collector of the metal case 32.
3, and the solid agent 34 is filled halfway into the periodic magnetic field device 31.

The solid agent 34 is initially in a viscous liquid state and generally becomes solid after being left for several hours.

After the solid agent 34 is solidified, a liquid conductive film made of a mixture of highly conductive silver powder and epoxy resin is applied to the surface of the solid agent 34 to a thickness of about 0.1 to 0.5 mm and solidified.

By repeating filling, solidifying, and applying the conductive film with the solid agent 34 in this manner, the radio wave shields 35, 36, and 37 are formed.

After the entire gap in the metal case 32 is filled with the solid agent 34, the injection hole 33 is sealed with a metal lid (not shown) or the like.

The tube 1, the magnetic field focusing device 31, the heat radiation block 24, etc. are held mechanically and stably.

When a radio wave shield is formed with the dimensions described above,
The conductive coating is sufficiently adhered not only to the surface of the solid agent 34 but also to the outer circumferential surface of the periodic magnetic field device 31 and the inner wall of the metal case 32, reducing the possibility that gaps will occur between the inner and outer circumferential surfaces of the radio wave shields 35, 36, and 37. , it is also possible to reduce the number of radio wave shields.

It has been experimentally confirmed that when the radio wave shield is a single sheet and the radio wave shield 35 closest to the collector side is formed of the conductive film described above, the wave of the traveling wave tube passes through the paths 41 and 42. It has been found that the unnecessary radio waves radiated to the outside are reduced by several tens of dB compared to the conventional type shown in FIG.

Although the above embodiment describes a coaxially coupled metal-ceramic traveling wave tube, the present invention can also be applied to a waveguide-coupled metal-ceramic traveling wave tube that uses a waveguide for input/output extraction. .

As explained above, according to the present invention, the unnecessary return of high-frequency power from the collector side to the electron gun side is eliminated or reduced to a negligible level, making it possible to prevent the emission of unnecessary radio waves to the outside and to prevent the emission of traveling waves. It becomes easy to produce a high-gain, high-efficiency traveling wave tube without damaging the characteristics of the resin filled inside the tube.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a conventional coaxially coupled metal-ceramic traveling wave tube, and FIG. 2 is a longitudinal sectional view of an example of a metal-ceramic traveling wave tube according to the present invention. In the figure, 1 is a tube, 11 is an electron gun, 12 is a slow wave circuit, 13 is a collector, 14 is an elongated metallic outer tube, 18
19 is a ceramic part, 19 is a cylindrical ceramic, 24 is a heat dissipation block for collector cooling including an insulating plate 23, 31 is a periodic magnetic field device for electron beam focusing, 32 is a metal case, 33 is an injection hole, and 34 is a solid agent. , 35, 36, and 37 indicate radio wave shields.

Claims (1)

[Scope of utility model registration request] A tube including a slow-wave circuit in which an electron gun that generates an electron beam interacts with a high frequency wave, a collector electrically insulated with a cylindrical ceramic and the slow-wave circuit, and a tube for focusing the electron beam. In a traveling wave tube in which a periodic magnetic field device is housed in a metal case, a plurality of metal plates are provided between the metal case and the periodic magnetic field device for blocking high frequency power leaking from the collector side to the electron gun side. A radio wave shielding body is placed in close contact with the inner wall of the metal case and the outer circumferential surface of the periodic magnetic field device, with a solid agent filled in the gap in the metal case, and the radio wave shield is placed periodically at intervals of 1/4 of the wavelength of the operating frequency of the traveling wave tube. A metal-ceramic traveling wave tube characterized by its unique arrangement.