KR100291396B1 - A plate-type magnetron - Google Patents

Abstract

The planar magnetron has an anode having a plurality of vanes arranged at regular intervals with a cathode for emitting electrons, and forms a working space. At both ends of the working space are provided a pair of pole pieces formed of elastic bellows of length, and an adjustable magnet portion. The yoke used to change the distance between the magnets is arranged to change the frequency of the microwaves. End hats are also placed and the voltage applied to them changes the output power of the microwaves.

Description

Flat Magnetron {A PLATE-TYPE MAGNETRON}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat plate magnetron used in high frequency heating devices such as microwaves, and more particularly, to a multipurpose flat plate magnetron that effectively provides a microwave having a desired output and frequency.

A magnet is a crossed-field device in which magnetic fields and electric fields are orthogonal to each other in the working space of an electron tube, and there are two oscillation modes, namely type A oscillation and type B oscillation.

Type A oscillations depend only on the magnetic field strength and are caused by the periodic rotational movement of electrons generated by the magnetic field. Since the oscillation wavelength is not influenced by the cavity resonator as an external circuit unlike the type B oscillation mode described below, the oscillation wavelength is determined only by the magnetic field and can be expressed by the following equation.

λ = α / H

Is the oscillation wavelength, H is the magnetic field strength, and α is 2πmc / e. Since m is the mass of electrons and e represents the charge of electrons, the integer α is theoretically 10,650, but experimentally has a value of 10,000 to 13,000.

In the type A oscillation, there are two kinds of electron orbits, one of which is an orbit that obtains energy from an alternating electric field, the other is an orbit that energizes an alternating electric field, and in the orbit where energy is obtained, it is necessary to remove electrons.

With reference to FIG. 1, the B-type oscillation will be described.

1 is a view showing a conventional cylindrical magnetron configuration. As shown in this figure, a plurality of vanes 22 extend radially toward the center in the cylindrical anode 21 to form a cavity resonator. The cathode 23 is provided on the central axis of the cylindrical anode to define the working space between the cathode 23 and the vanes 22.

At the upper and lower ends of the anode 21, pole pieces 24 are provided, each of which is attached in close contact with a magnet 26 having a yoke 25. A heat sink 27 is provided between the anode 21 and the yoke 25 for dissipating heat generated by anode loss. This anode loss occurs when electrons are released from the cathode 23 and accelerated by the anode voltage impinging on the anode 21.

A pair of electrodes (end hats) 30 are provided to intersect or perpendicular to the magnetic field direction interposed in the working space. A negative voltage is applied to these end hats 30 to trap electrons in the working space.

In this configuration, the space inside the anode 21 is reduced in vacuum. When a high voltage is applied to the cathode 23 and the vane 22 using the power input unit 28 in the magnetic field formed in the working space by the magnet 26, electrons are emitted from the cathode 23 toward the vanes 22. do.

The emitted electrons thus move under the influence of a magnetic field from the magnet 26 towards the vanes 22 along the spiral or cycloidal path. As a result, these electrons energize the cavity resonator to generate a high frequency electric field which is output as microwaves through the microwave output unit 29.

As the electron source of the magnetron, thermionic cathod is mainly used. Hot cathode electrodes are cathodes where hot electron emission provides an electron source. Hot electron emission is a mechanism that emits electrons across the potential barrier of the material surface by heating the material to a temperature of 1500 to 2500 ° K, giving free electrons in the conduction band the same or greater energy as the work function of the material. The hot cathode is formed of a pure metal or a metal oxide or the like, but at present, a sintered type formed by mixing Ba compound (5BaO · 2Al ₂ O ₃ · CaO, etc.) and W powder, and press sintering the mixture, The impregnation type, which is obtained by impregnating Ba compounds in a molten state, is the mainstream. These have the advantage that the emission density of the electrons is high and the barium aluminite effect is used, so that the gas emission in the vacuum exhaust is small and can be reactivated even when exposed to the atmosphere.

Another type of electron source is the cold cathode. Cold cathodes are cathodes that emit electrons based on electric fields instead of hot electron emission. Field emission is an electron emission method in which a high electric field is applied to and near the surface of a material, thereby lowering the potential barrier at the surface and emitting electrons by the tunnel effect. This cathode is called a cold cathode because it does not need to be heated unlike a hot electron cathode. The current-voltage characteristic can be approximated by the Fowler-Nodeheim equation. 2 is a sectional view showing the configuration of the cold cathode. The emitter portion 90 made of a metal or semiconductor such as Si has a point structure so as to form a high voltage gradient around it, and forms the gate 70 with an insulating layer 80 such as a SiO ₂ film interposed therebetween. It is applied with a metal film. When a voltage is applied to the gate 70, a strong electric field is generated at the tip of the emitter, emitting electrons. Since the cold cathode has a lower operating temperature than the hot cathode and is provided in an array form, the cold cathode has a high current density.

The magnetrons currently used in high frequency heating equipment such as microwave ovens are mainly cylindrical. However, some use flat magnetrons. 3 and 4 are cross-sectional and perspective views, respectively, showing flat plate magnetrons using cold cathodes.

In the flat anode 41 shown in Fig. 3, a plurality of vanes 42 are formed perpendicular to the cathode 43 and the sole portion 51, which constitute a cavity resonator. Here, the sole portion 51 is at the same potential as the cathode 43, but, unlike the cathode 43, indicates a portion that does not contribute to the emission of electrons. The cathode 43 is arranged below the left end of the anode 41. The space between the anode 41 and the sole 51-vanes 42 forms a working space. Pole pieces for forming a uniform magnetic field in the working space are attached to the magnets of the yoke on both sides of the anode 41. This yoke has a heat sink 47 that releases heat generated due to anode loss.

In this configuration, the internal space of the anode 41 is vacuum compressed. Power source input rotor voltage between gate 60 and soul 51-vanes 42 and between anode 41 and soul 51-vanes 42 in a magnetic field formed by the magnet 46 in the working space. When applied, electrons are emitted from the cathode 43 toward the vanes 42 as described using FIG. 2.

The emitted electrons travel along the spiral path in the same manner as in the cylindrical magnetron to the right from the magnet 46 in FIG. 2 under the influence of the magnetic field from the magnet 46 in the working space. In progress, these electrons energize the cavity resonator to generate a high frequency electric field that is output as microwaves through the microwave output section 49.

In the case of the magnetron using the split anode, various various operation modes can be generated according to the split number. The mode commonly used for type B oscillation is π-mode, where the phase difference between adjacent resonators is π radians and the interaction between them is the strongest.

However, in the oscillation of the magnetron, when there is another mode having an oscillation frequency close to the oscillation frequency in this π-mode, mode jumping from π-mode to another mode occurs due to a small change in operating conditions. As a result, the oscillation frequency and output change abruptly. Therefore, it is necessary to make the resonance frequency of each mode as distinct as possible by making the coupling between the resonators as compact as possible.

In a conventional magnetron, split anodes and vanes are connected through a conductor forming an equalized ring to separate the modes. This equalization ring allows the split anodes to have a voltage oscillation in the same phase, so that it is possible to limit the possible modes of oscillation to π-mode and 0-mode (both split anodes and vanes oscillate in the same phase).

In this way, the conventional magnetron is configured such that when a constant magnetic field is applied to the working space by a magnet attached to the yoke, a microwave having a constant frequency and a constant output power is generated. Therefore, the obtained output power and frequency could not be changed depending on the intended use.

Magnetrons are extremely useful for their high oscillation efficiency and high output at low cost, so they can be applied to a wide range of technical fields other than microwave ovens. Accordingly, an important issue is how to realize a multi-purpose magnetron that can be widely applied in various fields such as communication, radar, and electronic devices.

Accordingly, it is an object of the present invention to solve the above problems and to provide a planar magnetron that can be used for multipurpose purposes and which can effectively produce microwaves with the required output and frequency.

In order to achieve the above object, the present invention is configured as follows.

According to the first aspect of the present invention, a flat plate magnetron

A cathode for emitting electrons;

An anode having a plurality of vanes disposed at regular intervals;

A magnet unit for generating a uniform magnetic field in the working space interposed between the cathode and the anode; And

A pair of electrodes arranged opposite to each other in the working space and perpendicular to the uniform magnetic field

And the magnet portion is adjustable to change the magnetic field strength generated in the working space.

According to a second aspect of the present invention, in the flat plate magnetron having the first characteristic, the magnet portion includes: a pair of pole pieces disposed to face each other on both sides of the working space; And a pair of magnets, each attached to a pole piece, set in close contact with the yoke to effect magnet engagement, which magnets are suitable for movement.

According to a third aspect of the present invention, there is provided a flat plate magnetron having the first characteristics, wherein the magnet portion comprises: a pair of pole pieces disposed opposite to each other on the working space; And a pair of magnets each attached to the pole piece and set in close contact with the yoke to form a magnet engagement, the length of the pole piece being variable.

According to a fourth aspect of the present invention, there is provided a flat plate magnetron having the first characteristics, wherein the magnet portion comprises: a pair of pole pieces disposed to face each other on both sides of the working space; And a pair of magnets each attached to the pole piece and set in close contact with the yoke to form a magnet engagement, the length of the yoke being variable.

According to a fifth aspect of the present invention, a flat plate magnetron

A cathode for emitting electrons;

An anode having a plurality of vanes disposed at regular intervals;

A magnet part generating a uniform magnetic field in the working space interposed between the cathode and the anode; And

A pair of electrodes arranged opposite to each other in the working space and perpendicular to the uniform magnetic field

It includes, characterized in that the constant voltage or negative voltage can be selectively applied to the electrode.

In the foregoing, the output power is variable in accordance with the potential change of the electrode, while the frequency is variable in accordance with the distance between the magnets. In addition, when a constant voltage is applied to the electrode, it is possible to remove electrons from the working space which may disturb the oscillation.

1 is a block diagram showing a conventional cylindrical magnetron.

2 is a cross-sectional view showing the configuration of a conventional cold cathode.

3 is a cross-sectional view showing a conventional flat magnetron.

Figure 4 is a perspective view showing a conventional flat magnetron.

5 is a cross-sectional view showing a flat magnetron according to the present invention.

<Explanation of symbols for the main parts of the drawings>

11: anode

12: vane

13: cathode

14: pole piece

15: York

16: magnet

20: end hat

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

5 is a cross-sectional view showing a flat magnetron according to the present invention. As shown in FIG. 5, such a flat plate magnetron comprises an anode 11, a vane 12, a cathode 13, a pole piece 14, a yoke 15, a magnet 16, and an end hat 20. It is composed.

The space interposed between the anode 11 and the cathode 13 arranged in the vertical direction defines a working space. On both sides of the working space 18 in the horizontal direction, a pair of electrodes or end hats 20 to which a constant voltage and a negative voltage are applied are disposed to face each other. A pair of pole pieces 14 for generating the magnetic field necessary for the working space 18 are arranged opposite to each other on the outside of the end hat 20. A pair of magnets 16 are provided on the outside of the pole piece 14. The magnet 16 has a yoke 15 disposed in contact with the anode 11. Elements contributing to the formation of a magnetic field in the working space 18 include a magnet 16, a pole piece 14 and a yoke 15, which are magnetically coupled to each other. These elements are collectively called magnetic parts.

Here, the magnet 16 is ferrite and is fixed to the side wall of the housing. The yoke 15 is made of a galvanized iron material because it also acts as a heat sink for dissipating heat generated from anode loss.

In such a flat plate magnetron, the gap (inter-magnet distance) of the magnet portion affecting the magnetic field strength in the working space 18 is bellowsed on the pole piece 14 and the yoke 15 so that a variation of 20 mm can be achieved. by providing it in the form of bellows. The magnet 16 can also be moved with this change in distance. That is, the magnetic field variable means is not limited to changing the distance between the magnet and the working space by changing the length of the pole piece and the yoke as shown in FIG. 5, and the pole piece and the yoke are fixed and a part of the magnet is magnetized. You can also move it out of circuit or use a magnetic shield.

In addition, as a length adjustment and a magnet moving means, you may carry out directly using a screw, a slide, etc., or indirectly by a piezoelectric element etc.

The positive electrode 11 is produced by the method for producing a flat plate magnetron positive electrode disclosed in Japanese Patent Laid-Open No. 8-315,742.

Next, an operation overview of the flat plate magnetron will be described.

First, the gap distance of the magnet portion is set as desired by manipulating the bellows of the pole piece 14 and the yoke 15 so that a necessary magnetic field is formed in the working space 18. When a voltage is applied in the same manner as described for the conventional magnetron with reference to FIG. 3, electrons are emitted from the cathode 13 and travel along the cycloid path in the working space 18 under the influence of a magnetic field. As a result, these electrons energize the cavity resonator to generate a high frequency electric field. Accordingly, microwaves having a frequency and an output corresponding to the distance between the magnets or the amount of adjustment of the pole piece 14 and the yoke 15 will be extracted.

In the flat plate magnetron shown in FIG. 5, a positive or negative voltage can be selectively applied to the end hat 20, the magnet 16 is movable, and the yoke length and pole piece length are required output and frequency. And to provide a microwave with In other words, this plate-shaped magnetron is configured such that electrons that will disturb the oscillation are removed from the working space by the application of a constant voltage to the end hat 20, which voltage is changed to control the output.

The magnet 16 is movable and the bellows-type pole piece 14 and yoke 15 are adjusted to vary the yoke length and the pole piece length so that the gap distance of the magnet portion is changed to control the frequency.

For example, when the anode voltage is set to 100V, the anode soul distance is 0.5mm, the magnetic field strength is 1,360 gauss (the distance between magnets is set to 30mm), and the end hat is set to -10V voltage, 2.1A discharge current And output power of 160W (2.5GHz) oscillation can be obtained.

When the magnetic field strength is changed to 1,090 gauss, a microwave having a frequency of 3.1 to 5.1 GHz with an oscillating output of 3 to 7 W can be obtained. In addition, when a + 10V voltage is applied to the end hat 20, it can generate microwaves having a frequency of 3.1 to 5.1 GHz with an oscillating output of 10 to 20 W, which is about three times the output.

As described above, according to the first to fourth characteristics of the present invention, since the magnet portion can be configured to change the magnetic field strength generated in the working space, it is possible to change the oscillation frequency by changing the magnetic field strength. In particular, the length of the magnet, the pole piece, and the yoke length are adjusted to change the magnetic field strength in accordance with the gap distance of the magnet portion, so that the frequency can be changed.

According to the fifth characteristic, since electrodes are provided to which a positive or negative voltage can be applied, it is possible to remove from the working space electrons that interfere with oscillation when a constant voltage is applied to these electrodes.

Although the embodiment using the cold cathode has been described, it is also possible to use a hot electron cathode.

Claims (5)

A cathode for emitting electrons; An anode in which a plurality of vanes are arranged at regular intervals; A magnet unit for generating a uniform magnetic field in the working space sandwiched between the cathode and the anode; And A pair of electrodes disposed on both sides of the working space to face each other perpendicular to the uniform magnetic field. Including; The magnet part includes a pair of pole pieces disposed to face each other on both sides of the working space, and a pair of magnets, each of which is attached to the pole piece and is in close contact with the yoke to form a magnetic coupling. The magnet unit is a plate-type magnetron (plate-type magnetron) that can be adjusted to vary the magnetic field strength generated in the working space. 2. A flat plate magnetron according to claim 1, wherein said pair of magnets are movable. 2. A flat plate magnetron according to claim 1, wherein said pole piece is variable in length. 2. The flat plate magnetron of claim 1, wherein said yoke is variable in length. The plate type magnetron of claim 1, wherein a positive or negative voltage is selectively applied to the pair of electrodes.