JP4004850B2 - Magnetron device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetron device provided with a filter to reduce spurious radiation, and more particularly to a magnetron device with good oscillation stability.
[0002]
[Prior art]
A magnetron is widely used in transmitters such as radar devices because it is inexpensive and easy to handle, but it can be said that it is one of the devices in which it is difficult to suppress spurious radiation due to its oscillation mechanism. On the other hand, in recent years, there is a situation in which the regulation of spurious radiation becomes stricter with respect to a device that emits microwaves, and a magnetron device provided with a filter has been developed in order to reduce spurious radiation.
[0003]
In general, a magnetron oscillates in a main mode called a π mode, but various spurious emissions are also generated. Among spurious emissions, the radiation power in the mode caused by the resonance circuit of the magnetron called π-1 mode is the largest. For example, in a vane strap type magnetron in which the π mode oscillates in the 9.4 GHz band, the π-1 mode is in the vicinity of 10.5 GHz, which is a higher frequency band than the π mode. Therefore, spurious radiation can be suppressed by using a filter in which the frequency of the π mode is a pass band and the frequency of the π-1 mode is a stop band.
[0004]
FIG. 7 shows a block diagram of a conventional example. The microwave oscillated by the magnetron 1 is supplied to a load such as an antenna of the radar apparatus via the isolator 6 and the filter 3. As the filter 3, a band pass filter, a low pass filter, a band rejection filter or the like having a frequency of π mode as a pass band and a frequency of π-1 mode as a stop band is used. The isolator 6 is provided in order to prevent the microwave oscillated by the magnetron 1 from being reflected by the filter 3 and affecting the oscillation of the magnetron. In the magnetron device having such a structure, the spurious suppression effect can be expected from the characteristic characteristic of the filter as it is, and the design is easy. However, the magnetron device using the isolator 6 has a high cost of the isolator, and it is difficult to reduce the cost of the device.
[0005]
FIG. 8 shows another conventional example in which the magnetron 1 and the filter 3 are directly coupled by the transmission line 7. In this case, since the microwave reflected by the filter 3 is directly incident on the magnetron 1, the reflected wave affects the oscillation of the magnetron 1. Therefore, the line length of the transmission line 7 cannot be arbitrarily determined and needs to be set to a desired length. Conventionally, the line length of this transmission line has been adjusted so that the phase of the π mode output can be extracted most effectively. However, in the magnetron device in which the line length is set in this way, the oscillation in the π mode is not stable, the frequency of so-called missing pulses that operate in the π-1 mode is increased, and the stability of the oscillation is good. There was no problem. There is also a problem that the spurious suppression effect inherent to the filter cannot be obtained.
[0006]
[Problems to be solved by the invention]
As described above, the configuration using the conventional isolator has a problem that the cost of the isolator is high and it is difficult to reduce the cost of the apparatus. Further, in the configuration in which a spurious suppression filter is directly coupled to the magnetron via a transmission line, there is a problem in that the oscillation stability of the magnetron is poor and the spurious suppression effect of the filter cannot be obtained sufficiently. An object of the present invention is to solve the above-described problems and provide a device having good oscillation stability in a magnetron device having a configuration in which a magnetron and a filter are directly coupled by a transmission line.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 of the present application is a magnetron device in which a magnetron and a filter for blocking radio waves in a predetermined frequency band are coupled by a transmission line, wherein the magnetron, the transmission line, and the filter are used. the resonant frequency of the configured circuit system, one of the spurious components the magnetron emits, sets the length of the transmission line so as to substantially coincide with a frequency of at least one spurious component included in the stop band of the filter The Q value of the resonance mode of the one spurious component is lowered .
[0008]
The invention according to claim 2 is characterized in that, in the invention of claim 1, the resonance frequency adjusting mechanism is provided in the transmission line.
[0009]
The invention according to claim 3 is the invention according to claim 1 or 2, wherein another transmission line is coupled to a load side of the filter to which the magnetron and the transmission line are coupled, and the transmission output is adjusted to the transmission line. An adjusting mechanism is installed.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. FIG. 1 shows an embodiment of the present invention. The magnetron 1 uses a vane strap type, the frequency of a π mode as a main mode is 9.441 GHz, and the frequency of a π-1 mode which is one of spurious components is 10. It is 464 GHz.
[0011]
FIG. 2 shows the result of measuring the impedance Zm of the magnetron 1 of the present invention. Resonances corresponding to the π mode and π-1 mode are indicated by marker 1 (▲) and marker 2 (▼), respectively. On the other hand, the filter 3 is a low-pass filter that passes the π mode frequency of the magnetron 1 and blocks the π-1 mode frequency, and has the impedance Zf shown in FIG. Here, the marker 1 (▲) and the marker 2 (▼) are set to the same frequency as that in FIG. 2 (9.441 GHz and 10.464 GHz, respectively). From FIG. 3, it can be seen that there is almost no reflection in the π mode and a characteristic close to complete reflection in the π-1 mode. In such a device, when the line length of the transmission line 2 is determined so that the transmission output of the π mode is transmitted satisfactorily, the resonance of the π-1 mode of the magnetron 1 is blocked by the filter 3 in that frequency band, that is, Since it is in a state close to complete reflection, the Q value becomes high. This is the reason why the conventional magnetron device in which the magnetron and the filter are coupled by the transmission line does not operate stably. Therefore, in the present invention, in order to lower the Q value of the resonance in the π-1 mode, the resonance frequency in the circuit system constituted by the magnetron 1, the transmission line 2, and the filter 3 is made to coincide with the frequency of the π-1 mode. Like that. With this configuration, the microwave energy in the π-1 mode loses resistance due to the resonance of the transmission line, and the Q value decreases.
[0012]
Hereinafter, a method for setting the length L of the transmission line 2 will be described as a method for adjusting the resonance frequency in the circuit system including the magnetron 1, the transmission line 2, and the filter 3 to the frequency of the π-1 mode. This can be realized by setting the sum of the imaginary components of the admittance of this circuit system to zero. As shown in FIG. 2, the impedance of the magnetron 1 is Zm = 0.786 + 0.205j in the π-1 mode and the phase angle is 128 degrees. As shown in FIG. 3, the impedance including the filter 3 is Zf = 0.33-1.149j and the phase angle is -82 degrees. Therefore, in order to reduce the imaginary component of the admittance including the magnetron to 0, a transmission line having a line length of 128 degrees may be added to the magnetron. On the other hand, in order to set the imaginary component of the admittance including the filter to 0, a transmission line having a line length of −82 degrees may be added to the filter. Therefore, the line length of the transmission line 2 may be 46 degrees (128-82 degrees). The effective wavelength λg at the frequency of π-1 mode of 10.464 GHz is 36.76 mm because the used waveguide is a rectangular waveguide of 22.9 mm × 10.2 mm. Therefore, the line length L of the transmission line is L = 36.76 mm × (46/720) = 2.35 mm. Since it is equivalent to adding a line having an integral multiple of λg / 2 to the transmission line, the line length L may be set to 2.35 mm, 20.73 mm, 39.11 mm, or the like.
[0013]
FIG. 4 shows the relationship between the transmission line length and the miss pulse. FIG. 4 shows that the range in which the magnetron oscillates stably is L ± λ / 16. On the contrary, the value obtained by converting the allowable value on this dimension to the allowable value of the frequency with the transmission line length fixed becomes the allowable value of the frequency when the resonance frequency of the transmission line is matched with the frequency of the π-1 mode. .
[0014]
Next, the case where the adjustment mechanism which adjusts the resonant frequency of a transmission line is added using FIG. 5 is demonstrated. In FIG. 5, a rectangular waveguide 4 is used as a transmission line between the magnetron 1 and the filter 3, and a resonance frequency adjusting screw stub 8 is provided on the rectangular waveguide 4 as a resonance frequency adjusting mechanism. This is provided to compensate for the impedance variation in the π-1 mode of the magnetron. The length of the screw stub 8 inserted into the rectangular waveguide 8 is adjusted to adjust the capacitance value at the tip. The resonance frequency can be set to a desired value.
[0015]
FIG. 6 shows another embodiment of the transmission output adjusting mechanism shown in FIG. 5 in which another rectangular waveguide 5 is coupled to the load side of the filter 3 and the π-mode transmission output adjustment mechanism is coupled to the rectangular waveguide 5. A screw stub 9 is added. This is provided to compensate for the fact that if the resonant frequency of the circuit system is substantially matched with the frequency of the π-1 mode, it also affects the oscillation of the π mode and the output decreases. Yes. In addition, there is an effect of compensating for variations in impedance in the π mode of the magnetron 1. Therefore, as shown in FIG. 6, not only when the rectangular waveguide 4 is provided with the screw stub 8 for adjusting the resonance frequency, but only when the length of the rectangular waveguide 4 is set to a predetermined length, the resonance is achieved. Even if the screw stub 8 for frequency adjustment is not provided, there is an effect for adjusting the oscillation output in the π mode. The transmission output adjusting screw stub 9 is preferably installed on the load side from the filter 3. If the filter 3 is installed in the rectangular waveguide 4 on the magnetron 1 side, the adjustment of the transmission output affects the impedance of the magnetron in the π-1 mode, and the stability of the magnetron operation is lowered. It is.
[0016]
In the above description, a rectangular waveguide is shown as the transmission line. However, the transmission line can be realized by a coaxial line or a planar circuit. In addition, the filter is shown as a low-pass filter that passes the π mode and cuts off the π-1 mode. However, a band-pass filter or a band-stop filter can be used if the main mode passes and the spurious component is cut off. Etc. can be similarly realized. In addition, although the case where the main mode of oscillation of the magnetron is the π mode and the π-1 mode is used as the spurious component has been described, it is needless to say that the present invention is not limited to this.
[0017]
【The invention's effect】
As described above, in the present invention, by adjusting the resonance frequency of the circuit system from the magnetron to the filter to the frequency at which radiation is desired to be suppressed, the Q value of the frequency can be lowered, and a magnetron device with good stability can be obtained. Realized.
[0018]
Further, by providing the transmission line with a resonance frequency adjusting screw stub and a transmission output adjusting screw stub, it is possible to compensate for variations in the impedance of the magnetron and to manufacture a magnetron device with a high yield.
[Brief description of the drawings]
FIG. 1 is a block diagram of a magnetron apparatus showing an embodiment of the present invention.
FIG. 2 is a diagram showing measurement results of impedance of the magnetron of FIG. 1;
FIG. 3 is a diagram illustrating a measurement result of impedance of the filter of FIG. 1;
FIG. 4 is a diagram showing the relationship between transmission line length and miss pulse frequency.
FIG. 5 is a diagram for explaining a method of adjusting a resonance frequency of a transmission line according to the present invention.
FIG. 6 is a diagram illustrating a method for adjusting a transmission output according to the present invention.
FIG. 7 is a block diagram showing a conventional example.
FIG. 8 is a block diagram showing another conventional example.
[Explanation of symbols]
1: magnetron, 2: transmission line, 3: filter, 4: rectangular waveguide, 5: rectangular waveguide, 6: isolator, 7: transmission line, 8: screw stub for adjusting resonance frequency, 9: transmission output Screw stub for adjustment

Claims (3)

A magnetron, the magnetron apparatus coupled by a transmission line filter for blocking a radio wave in a predetermined frequency band, the magnetron, the resonance frequency of the formed circuit system by the transmission line and the filter, the magnetron emits Of the spurious components, the length of the transmission line is set so as to substantially match the frequency of at least one spurious component included in the blocking frequency band of the filter, and the Q value of the resonance mode of the one spurious component is lowered. Magnetron device characterized by.   The magnetron device according to claim 1, wherein an adjustment mechanism for the resonance frequency is installed in the transmission line.   2. The transmission device according to claim 1, wherein another transmission line is coupled to a load side of the filter to which the magnetron and the transmission line are coupled, and an adjustment mechanism for adjusting a transmission output is installed in the other transmission line. 2. The magnetron device according to any one of the above.

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