KR870000689B1 - An electron tube - Google Patents

Abstract

A magnetron, suitable for industrial purposes, radar pulse emission, esp. for microwave ovens, has a drain electrode near the cathode to capture positive ions of residual gas and to suppress high frequency noise. A spiral drain electrode pref. made of W,Mo, Ta and/or Ti is supported by a support so that its turns to be alternate with those of a spiral cathode, which is around a cathode support and faces an anode vane assembly. For a magnetron giving an output of 800 W at 2.45GHz, the cathode dia. is 0.58 mm, drain electrode dia. is 0.5 mm, cathode pitch, drain electrode pitch is 2.0 mm each, spiral dia. is 5.00mm, anode vane tip inside dia. is 10mm.

Description

Orthogonal Electromagnetic Tube

1 is a longitudinal sectional view showing a general structure of a magnetron as an example of an orthogonal electromagnetic field electron tube.

2 is a schematic diagram showing a noise measurement circuit.

3 is a diagram illustrating noise characteristics of an input line generated in a magnetron.

4 is a schematic diagram explaining the cause.

Figure 5 is a longitudinal cross-sectional view showing the main portion of an embodiment of the present invention.

6 is an enlarged view of the main part.

7 is an operation circuit diagram.

8 to 9 are noise characteristic diagrams respectively.

10 to 12 are main longitudinal cross-sectional views each showing another embodiment of the present invention.

13 to 19 are connection diagrams showing examples of the respective operation circuits.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an orthogonal electron tube, and an orthogonal electromagnetic field tube that obtains a high frequency oscillation or power amplification by giving a magnetic field in a direction perpendicular or slightly perpendicular to the direction of movement of an electron is well known. As can be seen, it is used as a magnetron, a magnetron traveling wave tube, and other similar electron tubes. Electromagnetic devices such as microwave ovens are widely used today, but the regulation of noise leakage is tightened.

Internationally, the International Radio Special Disability Committee (CISPR) is implementing or conducting a review on this noise regulation in each country.

Therefore, in this type of electron tube, it is natural to reduce the noise generated by the electron tube itself, to emit unnecessary radio waves, and to further reduce leakage.

Referring to the conventional structure and noise generation situation using the magnetron as an example, the structure of the magnetron for a microwave oven in the 2.45 GHz band is as shown in FIG. In the figure, reference numeral 21 denotes a magnetron oscillating main body, 22 denotes a radiator, 23 and 23, a ferrite magnet, 24 denotes a yoke, and 25 denotes a serial cable wound in a coil shape. Sword, 26 is anode vane, 27 is anode cylinder, 28 is strapping, 29 is output, 29a is antenna feeder, 30 is a pole piece, Numeral 31 denotes a cathode input insulating cylinder, 32, 33 denotes a cathode support, 34 and 35 denote a cathode terminal, 36 denotes a choke coil, 37 denotes a through-type capacitor, 37a denotes a The cathode input terminal 38 denotes a sealed box.

Thus, a voltage of 1000 (V) is applied between the anode vane 26 and the cathode 25 so that the magnetic flux in the direction parallel to the cathode axis, that is, the tube axis, is oscillated by the magnet in the electromagnetic space 39. It works.

Most of the oscillating microwaves are supplied to the external load at the output through the antenna feeder.

In the microwave power output from the output, a lot of noise other than the fundamental wave is mixed. Meanwhile, unwanted high frequency noise leaks through the cathode terminal and the filter circuit composed of the choke coil and the condenser which form part of the input lead.

These noise components range from a few 10 Hz to several GHz. Of course, the noise circuit leaking toward the power transformer or commercial power line is attenuated by the filter circuit, but a relatively high-quality filter circuit must be used to complete the leakage suppression effect.

Therefore, the noise component leaking the magnetron of the structure shown in FIG. 1 in the direction of the input line by the measurement circuit of FIG. 2 shows a spectrum in which the noise of frequency components up to 1000 MHz is continuously distributed as shown in FIG. It is detected.

In this case, however, the measurement results are obtained when the filter circuit of FIG. 1, that is, the choke coil and the capacitor are not used. In FIG. 2, reference numeral 20 denotes a magnetron under measurement as shown in FIG. 1, 40 is a waveguide, 41 is a dummy rod 42 is a cathode power supply, and 43 is a high voltage. A power supply, 44 is a cathode input line, 45 is a measurement blove such as a pearlite clamp, and 46 is a spectrum analyzer.

As one of the causes of the noise of the magnetron continuously distributed in this way, the following estimation can be made.

In other words, FIG. 4 schematically shows the coaxially arranged anodes and cathodes of the magnetron, but in the figure, the cathode is negative and the anode is positive, and a high voltage of 1000 (V) is applied between the cathodes and the anode. When the hot electrons are released, in the working space 39, the potential distribution becomes concave below as indicated by the dotted line curve a in the figure due to the space charge in the vicinity of the cathode.

)을 발생한다. 발생한 플라스 이온은 곡선(a)으로 표시한 전위 분포의 구석(도면에 부호 m로 표시)에 유입되여 점차 공간전하계중의 전자와 플러스 이온과의 중화가 진행하여 그 결과 이 구석부근의 전위는 상승하여 부호(m)로 표시한 바와 같이 캐소드(25)와 동등, 혹은 이보다 약간 높은 전위까지 높아진다.On the other hand, as indicated by arrow B, a direct current magnetic field of 1000-2000 gauss is applied in the direction of the cathode axis in this working space, and the electrons exiting the cathode revolve around the cathode by the action of the electric field and the magnetic field. Especially for orthogonal electromagnetic fields, the electrons have a long traveling distance, so the electrons are more likely to collide with the residual gas, and there are more positive ions than other straight tubes.

Will occur). The generated plasmon flows into the corner of the potential distribution indicated by the curve (a) (marked in the figure) and gradually neutralizes the electrons and the positive ions in the space charge system. As a result, the potential near the corner rises. As indicated by the sign m, the potential is increased to the potential equivalent to or slightly higher than the cathode 25.

In this state, the potential distribution in the working space becomes as shown by the solid curve b. As a next step, the corner m of the potential is formed again by the space charge. Thus, a series of processes are repeated periodically. As a result, it can be assumed that a complex pulsation phenomenon occurs in the current between the cathode and the anode, that is, the anode current, and leaks to the external circuit as noise.

Therefore, the noise generated in this way is considered to shape a relatively low frequency component such as 1000 MHz or less.

And these noise components are mainly shown as line noise, which leaks on the input line. This noise also causes various radio interferences.

In order to reduce the noise component in the reason of the above noise generation cause, the positive ion which substantially solves the corner of the potential distribution occurring in the electronic working space, especially the cathode, or appears near the corner of the potential distribution It is thought that it can be configured to eliminate the unstable fluctuations near the corners of the potential distribution as it is removed without delay.

The present invention is intended to suppress the occurrence of noise as described above. That is, in the orthogonal electron type electron tube, a drain electrode for collecting the positive ions is formed near the cathode for the outstandingness of ionization of residual gas in the tube which cannot be pitched, and this electrode is formed at a potential such as a cathode or a negative potential with respect to the cathode. In addition, it is possible to suppress the occurrence of noise by suppressing the potential change in the working space near the cathode.

Hereinafter, the embodiment will be described with reference to the drawings by using the magnetron (the same parts are denoted by the same reference numerals).

5 and 6 show only the magnetron oscillation unit main body, and the radiator, the magnetic circuit, the tread box, the filter circuit, and the like are assembled as shown in FIG. Herein, the cathode mechanism is described in detail. The end head 51 a, the ceramic insulator 52, and the conductor block 53 are sequentially fixed to one end of the rod-shaped cathode support 32 disposed on the tube axis. The other side of the cathode support is joined to the cathode terminal 35 and the exhaust pipe 54.

One end of the slip-shaped cathode support 33 is coaxially insulated with a ceramic spacer 55 and joined to the cylindrical part 56 at the end, and the other end is joined to another cathode terminal 34. A triumium tungsten direct cathode 25 wound in a coil form is joined between the round part 56 and the conductor block 53. As a result, the cathode 25 can be energized and heated by the heating power supplied to the cathode terminals 34 and 35.

The outer side of the slip-shaped cathode support 33 is insulated again, and the slip-shaped support 57 of the drain electrode is coaxially disposed, and is coupled to the drain electrode terminal 58 which is hermetically bonded to the upper end of the insulating cylinder 31. . A conductor slip 59 and an end head 51b are connected to the lower end of the drain electrode support 57, and one end of the drain electrode 60 wound in a coil form is bonded to this slip 59. . The drain electrode 60 is wound in the same pitch and in the same spiral shape as the cathode 25, and the other end is mechanically held by the soldering or mechanical indentation on the outer circumference of the ceramic insulator 52, for example. It is terminated and floated. The drain electrode 60 is formed of a surface selected from poorly soluble metals such as W, Mo, Ta, and Ti, or an alloy having a poor primary, secondary, and electron radiating property, and as shown in the drawing. It is located in the vicinity and in a location that does not disturb the flow of electrons from the cathode to the anode.

As an example, a magnetron with an output of about 800 (W) at 245 GHz, the coil wire diameters of the cathode and drain electrodes are 0.58 mm and 0.5 mm pitch intervals, respectively, 20 mm and spiral diameter of 5.0 mm anode vane tip. The inner diameter is 10 mm. Therefore, the helix of the cathode, the drain electrode and the helix are alternately arranged on the same plane at intervals of 1 mm.

In the drawings, reference numerals 31a and 31b denote ceramic insulators. In addition, the anode vane 26 and the anode cylinder constitute a plurality of common resonators and form an anode as a whole.

The magnetron 20 of the embodiment of the present invention having the above structure can be connected to and operated by the power supply circuit of the seventh illustration.

In the figure, reference numeral 61 denotes a cage transformer in which a primary side is connected to a commercial power source, and a high voltage winding 61a and a cathode heating winding 61b are wound on a secondary side, and 62 is a geocondenser of about 0.5 dB; Numeral 63 denotes a high voltage rectifier diode, and numeral 64 denotes a power supply for providing a potential between the cathode and the drain electrode.

In the following operation, the cathode is heated to emit hot electrons. A high voltage of several thousand (V) is applied between the cathode and the anode vane, and a direct current magnetic field of magnetic flux parallel to the tube axis of about 1500 gauss is applied to the electromagnetic space, and the oscillation operation is performed. Microwave energy generated in the common resonator is transmitted from the output to the external load through the antenna feeder. When the cathode is heated, a corner is formed at the potential near the cathode as shown in Fig. 4 by the emission electrons (when there is no drain electrode) .However, when the drain electrode is set to a negative potential of about -200V relative to the cathode, the corner of the potential is formed. The positive ions gathered toward the solar cell are immediately collected by the drain electrode because the drain electrode is at a negative potential again.

That is, positive ions flow into the drain electrode without stopping near the cathode, and electron-ion neutralization phenomenon in which the cathode is unstable does not occur.

As a result, generation of noise especially below an order of 1000 MHz is surely suppressed.

The inventors of the present invention actually measured the noise level of the magnetrons of FIGS. 5 and 6 by the measurement circuit as shown in FIG. This is shown in FIG. 8. In FIG. 8, the exposure phenomenon of the maximum value of the noise frequency component in the range of 0-100 MHz is shown in the graph as a result of changing the voltage of the drain electrode with respect to the cathode.

According to this measured value, the maximum value of the noise was reduced by about 30 dB when the potential of the drain electrode was set to about -150 (V) or less as compared with the case where the potential of the drain electrode was set to 0 (V), that is, the same potential as the cathode.

Moreover, the result of measuring the noise level coming out on the input line side when a magnetron was mounted and operated in a commercial microwave oven is shown in FIG.

In other words, this is the data represented by the curve combining peak values of the spectrum of 10 MHz or less, or the curve 71 in the case of the magnetron of the conventional structure shown in the first example, when the drain electrode is -150V in the magnetron of the embodiment of the present invention. As shown in the curve 72, it is found that the frequency is generally reduced to about 20 dB to 200 V as the entire frequency component range.

As such, the remarkability of the effects of the present invention is extremely obvious. Because of this, there is a possibility that the expensive line filter which is currently equipped in many magnetrons and microwave ovens can be omitted. In the present invention, even when the potential of the drain electrode is about the negative potential of the cathode, for example, about -200V, the current between the cathode and the anode, i.e., the anode current, does not decrease most of the time.

As shown in the above embodiment, when the cathode of the coil and the spiral of the drain electrode were arranged in the same plane, the electrode current was slightly increased when the drain electrode was negative.

In this respect, the present invention is essentially different from known tubes, ie electron tubes such as the grit magnetron for output control. In other words, examples of magnetrons having control grids in the vicinity of the cathode are described in, e.g., Western Gate, Book Cross Electromagnetic Microwave Device (E. OKRESS, CROSSED-FIELD MICROUAVE DEVICES vol, 11, 1961), especially page 85. A technique such as a lattice magnetron disclosed in the second figure of FIG. 2 and in the description of 293 pages or less in the study of ultra-high frequency magnetrons in the Japanese literature (June, 1952, Misuzu Bookstore) There is this. The former measures noise with a tripolar plate, which states that there is no inherent difference in the generation of noise even if the lattice voltage is changed. In other words, in the case of the grid for controlling the output power, the anode is disposed to substantially surround the anode vane, and is separated from the cathode in order to control the electron flow from the cathode.

Therefore, this is essentially different from serving as a drain electrode for collecting and discharging positive ions flowing near the cathode as in the case of the present invention.

In the tenth illustrated embodiment, the electromagnetic radiation cathode 25 uses a spiral cross-sectional shape that is flat in the direction parallel to the cathode axis, that is, the tube axis C. As shown in FIG.

Further, the grain electrode 60 protrudes slightly in the anode 26 direction than the cathode 25, and is located between the spirals of the cathode. In this embodiment, the potential of the drain electrode is set at a slightly negative potential with respect to the cathode. Example-Even if it is set to 150 (V), the reduction of the anode current is about 10% or less, and it is about the fine matter.

As a result, even if the potential of the drain electrode is the same as that of the cathode, the positive ion trapping action can be obtained, and the noise reduction effect can be obtained. In the case where the drain electrode is at the same potential as the cathode, a method of electrically connecting the two electrodes with a high resistance is preferable.

In the embodiment shown in the eleventh illustration, the cylindrical drain electrode 60 having the spirally shaped portion and the spirally recessed portion 81 of the pitch is insulated from the inner side of the coiled cathode 25. On the other hand, the conductor cylinder may be simply disposed near the inner side of the coil-shaped cathode without providing the recessed portion 81, and a negative potential may be applied thereto. 12 shows the case of the heat dissipating cathode 25, in which the drain electrode 60 is wound around the outer periphery of the electron emission layer 81 with a very rough pitch.

In this case, it is preferable to wind a finer pitch than the center portion near both ends of the drain electrode cathode and to minimize the reduction of the electron flow in the center portion. On the other hand, although not shown, in the case of a cathode in which a linear cathode wire is installed parallel to the tube axis direction, a straight wire drain electrode is disposed between adjacent cathode wires and a negative potential is applied to the drain electrode. Also, it may be formed at a relative position so that the reduction of the anode current remains below 10%.

In addition, in each of the above embodiments, the cathode and the drain electrode, etc. are each made and insulated from each other, but are not limited thereto. For example, a coiled cathode and a coiled drain electrode may be wound alternately or in a plurality of spirals. It may be connected electrically in the pipe and may be at the same potential.

In addition, an example of a single coil: An electron emitting layer may be deposited on the surface with a spiral of tungsten wire, and the remaining one may be left in a surface state where electrons are difficult to emit.

In this case as well, operations such as alternating arrangements of cathodes and drains, i.e., non-electron emitting surfaces, of substantially the same potential are obtained. Again, a single example uses a tungsten wire to deposit an electron radiation material on a portion of the surface, and to make the remaining surface non-emissive and wind it onto a coil to form an electron radiation surface and a substantially drain electrode. At the same time, it may be formed so as to face in the direction of the anode. Also in this case, if the non-electromagnetic radiation surface is slightly protruded toward the anode, the effect is again effective. They are extremely easy to fabricate, ensure positive ion capture and reduce noise.

Next, a practical power supply circuit in the case of applying a negative potential to the drain electrode will be described. As shown in FIG. 13, the intermediate tap P1 is formed on the high-voltage secondary winding 61a of the cage transformer 61, and this tab is formed. A double voltage rectifier circuit composed of a capacitor 62 and a diode 63 is connected, and the winding 61C to be connected to the terminal 58 of the drain electrode is wound around the same transformer 61.

As a result, a negative pulse voltage is applied to the drain electrode in a half cycle in which the anode becomes a positive voltage with respect to the cathode. As a result, a relatively simple power supply circuit configuration is achieved.

As shown in Fig. 14, the diode 82 may be connected, or as shown in Fig. 15, the potential may be applied to the drain electrode by the double voltage rectifying circuit formed by the capacitor 83 and the diode 84.

Again, as shown in FIG. 16, a resistor R is connected between the cathode and the drain electrode, a high voltage is applied between the drain electrode and the anode, and a self bias caused by the anode current flowing through the resistor R is applied to the drain electrode. It's okay.

In addition, as shown in FIG. 17, a secondary winding 61d is formed in the transformer 61 for the drain electrode power supply, and the full-wave rectifier circuit 85 is opened to give the drain electrode terminal 58 a negative potential with respect to the cathode. It's okay. Further, as shown in the eighteenth illustration, it may be combined with a high voltage by the full-wave double voltage rectifying circuit, a rectifying circuit for drain electrode voltage consisting of the winding 61C and the diode 82 and the capacitor 86, and the like.

In the nineteenth illustration, the components of the small transformer 86 and the drain electrode double-voltage rectifier circuit 87 on the secondary side are insulated from and disposed in the sealed box 38 of the magnetron. The primary side of the transformer is connected to the cathode input line.

When a voltage of about 3 V is applied to the cathode, the secondary side of the transformer 86 is sufficient if a voltage of about 10-1 00 (V) is obtained.

According to this embodiment, since the power supply for the drain electrode is incorporated in the magnetron itself, there is no need to change the power supply device such as the cage transformer 61 at all. In addition, the current flowing through the drain electrode is extremely small, so that a practically small power supply circuit can be used.

The above has described an example of a magnetron, but the present invention can be widely applied to a magnetron traveling wave tube and other orthogonal electromagnetic field electron tubes.

Claims (7)

An orthogonal electromagnetic field tube in which an electron radiation cathode and an anode coaxially disposed with each other are provided, and a magnetic flux parallel to the cathode axis is given to the space of the electron interaction between the cathode and the anode, wherein the anode is placed near the cathode and at the cathode. An orthogonal electron-type electron tube, wherein a drain electrode for collecting positive ions is provided at a position which does not disturb most of the flow of electrons, which is equal to or equal to the potential of the cathode. The anode is provided with a common resonator, and the electron tube according to claim 1 to operate the magnetron. The cathode is a direct-type cathode wound around a coil with a poorly soluble metal as a gas, and the drain electrode is disposed in the vicinity of the coil-like cathode. The electron tube according to claim 1. The electron tube according to claim 3, wherein the drain electrode is disposed without contact between the spirals of the cathode on the coil. The electron tube according to claim 3, wherein the drain electrode is wound so as to be positioned at the same pitch as the coil-shaped cathode and between the cathode spirals. The electron tube according to claim 1, wherein the outer circumferential end of the drain electrode protrudes in the anode direction from the cathode outer circumferential end. The electron tube according to claim 1, wherein the drain electrode is made of a single or alloy selected from W, Mo, Ta, and Ti.

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