JPH0810802B2 - Mode coupling type directional coupler - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a mode coupling type directional coupler used for monitoring the output of a high power millimeter wave oscillator gyrotron used for plasma heating in a nuclear fusion experimental apparatus.

[Prior art]

FIG. 3 is a partially cutaway perspective view showing a conventional mode-coupling type directional coupler, in which 1 is a TE of high power and high frequency.
A circular main waveguide capable of propagating the mn mode, 2 is a coupling hole, and 3 is a sub-waveguide for coupling the TE mn mode through the coupling hole 2. FIG. 4 is a cross-sectional view of the conventional mode-coupling type directional coupler shown in FIG. 3, in which 4a is a TEmn mode entrance of the circular main waveguide 1, and 4b is a circular main waveguide 1. The TEmn mode outlets 5a and 5b are the open ends of the sub-waveguide 3. A plurality of coupling holes 2 having the same shape are provided at equal intervals l. FIG. 5 is a cross-sectional view taken along a plane perpendicular to the central axis of the circular main waveguide 1 of the mode-coupling type directional coupler. In the figure, the sub-waveguide 3 has a shape in which the opening has vertical and horizontal inner dimensions a. It shows that it is a rectangular waveguide of × b. Next, the operation will be described. First, when the guide wavelength of the TEmn mode in the circular main waveguide 1 is set to λg ₁ , the spacing l of the coupling holes 2 is set to 1 / 4λg ₁ and the TE mode which is the fundamental mode in the sub-waveguide 3 is set. The inner size of the sub-waveguide is determined so that the _10- mode guide wavelength λg ₂ is equal to λg ₁ . This TEmn mode incident from the incident port 4a of the circular main waveguide 1 binds through TE ₁₀ mode and the coupling hole 2 of Fukushirubeha tube 3, TE ₁₀ mode Fukushirubeha tube 3 has an opening The TEmn mode propagates in the direction of the edge 5b because it is added in phase, but it does not propagate in the direction of the opening edge 5a because the phase is canceled, and thus has directionality. Also, the number of coupling holes 2 should be as small as possible in order to improve the frequency characteristics, but in order to accurately measure the directivity using a low-output sweep oscillator, the coupling degree should be greater than approximately 40 dB. However, the number of coupling holes 2 is increased to some extent.

[Problems to be Solved by the Invention]

The conventional mode-coupled directional coupler is configured as above, so that the frequency is 100G as in high power millimeter wave oscillator gyrotron used for plasma heating.
If the frequency becomes higher than Hz, the diameter d of the circular main waveguide 1 cannot be reduced because the transmission power is increased.
The guide wavelength λg ₁ of the TEmn mode in the circular main waveguide 1 becomes closer to the free space wavelength λ, which is the fundamental mode in the sub waveguide 3.
If the guide wavelength λg ₂ of the TE ₁₀ mode is made equal to this, the value of the dimension a of the sub-waveguide 3 becomes large, the sub-waveguide 3 becomes oversized, and modes other than the fundamental mode also occur, There was a problem that it became difficult to monitor the output as a directional coupler. The present invention has been made in order to solve the above problems, and even for high frequencies exceeding 100 GHz, the degree of coupling with the circular main waveguide can be achieved without increasing the size of the sub-waveguide. It is an object of the present invention to obtain a novel mode-coupling type directional coupler which is large in size and has excellent directivity and which can accurately monitor input power and reflected power to a circular main waveguide.

A mode-coupling type directional coupler according to the present invention has an interval satisfying a condition that a coupling coefficient in an opening direction capable of monitoring incident power high frequency of a sub-waveguide is 0. Two coupling holes are formed as a group, and these groups are formed with an interval satisfying the condition that the coupling coefficient in the opening direction that can monitor the reflected power high frequency of the sub-waveguide is maximum. It is the one. In the mode-coupling type directional coupler according to another invention, the distance between the coupling holes and the distance between the groups are different for each sub-waveguide.

[Action]

In the mode coupling type directional coupler according to the present invention, the two coupling holes forming a pair are spaced so that the coupling coefficient in the opening direction capable of monitoring the incident power high frequency of the sub-waveguide is 0. The spacing between these groups is set so that the coupling coefficient in the opening direction where the reflected power high frequency of the sub-waveguide can be monitored is maximized, so that the incident power high-frequency can be monitored for the sub-waveguide. It becomes possible to cancel the phase of. The mode-coupling type directional coupler in another aspect of the invention makes the mode other than the fundamental mode propagating in the circular main waveguide different by varying the distance between the coupling holes and the distance between the groups for each sub-waveguide. Will also be able to monitor.

【Example】

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 3 and 3a are sub-waveguides symmetrically arranged with respect to the circular main waveguide 1, and on one sub-waveguide 3 side, 2 is a coupling hole and these are spaced apart. Two sets provided with l ₁ are one set, and N sets are provided at equal intervals l ₂ , a total of 2N sets are provided. Also in the other sub-wave tube 3a side, 2a is a coupling hole, these two is a set provided with a spacing l _3, are provided N sets every regular intervals l _4. Where interval l ₁ and interval l ₃ are different, and
l ₂ and the interval l ₄ are configured differently. In addition, the same components as those shown in FIG. 4 are denoted by the same reference numerals and duplicate description will be omitted. By the way, for example, if the coupling degree of the TEmn mode by one coupling hole 2 in one sub-waveguide 3 is C ₀ , the distance z
The TEmn mode incident end 4a of the circular main waveguide 1 by the two coupling holes 2 provided in 1.
The coupling coefficient V _{f in the} direction and the coupling coefficient V _{b in the} direction of the opening end 5a of the sub-waveguide 3 can be expressed by the following equations. However, Here, λg ₁ and λg ₂ are in-tube wavelengths in the circular main waveguide 1 and the sub-waveguide 3, respectively. Therefore, in order to improve the directionality, Then, | V _b | = 0 can be set, so that, for example, in the TE ₁₀ mode in one of the sub-waveguides 3, the phase is canceled in the direction of the opening end 5a, so that the TE ₁₀ mode is Is not propagated and thus can be directional. Also, Then, | V _f | becomes maximum, and a large degree of coupling can be obtained with few coupling holes 2. Therefore, If 2N coupling holes 2 are provided so that the relationship of
A mode-coupling type directional coupler having good directivity even for high frequencies exceeding 0 GHz can be obtained. Similarly, in the other sub-waveguide 3a, for example, for the TE ₁₁ mode, the TE ₁₁ mode is not propagated in the direction of the opening end 5ab this time, but has a directivity so as to propagate in the direction of the opening end 5bb, and the coupling hole is also formed. In order to obtain a high degree of coupling in 2a, the above (1)
The intervals l ₃ and l ₄ can be set in the same manner as the formula (2). With such a configuration, when the propagation mode of the circular main waveguide 1 is the TE ₀₄ mode, one sub-waveguide 3 allows TE _{10 to be obtained} by the intervals l ₁ and l ₂ satisfying the above formulas (1) and (2). The incident power can be monitored at the opening end 5b of the mode. On the other hand, the millimeter wave reflected on the circular main waveguide 1 is a discontinuity or bending of the waveguide, or a reflection from a load or the like, and its mode is changed. However, by providing the other sub-waveguide 3a, it becomes possible to monitor the reflected power also in the TE ₁₁ mode, for example. As an example, the propagation mode of the circular main waveguide 1 is TE ₀₄ mode, the frequency is 120 GHz, the diameter d of the circular main waveguide 1 is 37 mm,
The vertical inner dimension a of the sub-waveguide 3 is 2.032 mm, and the horizontal inner dimension b is 1.016.
mm, the TE ₀₄ mode in-tube wavelength λg ₁ in the circular main waveguide ₁ is 2.607 mm, and the TE ₁₀ mode in-wavelength λg ₂ in the sub-waveguide ₃ is 3.167 mm. In the above equation, m ₁ = By setting 2, m ₂ = 1, l ₁ = 2.15 mm and l ₂ = 14.75 mm. In this way, if the distance between the coupling holes 2 is set, the directivity is calculated
The degree of coupling becomes infinite in dB, and the coupling degree C is 40, where the number N of pairs of coupling holes 2 is 40, and the coupling degree C ₀ by one coupling hole 2 is 77 dB. Becomes As a result, it becomes possible to accurately measure the directivity by the low-output sweep oscillator. Further, the mode discrimination degree with respect to the unnecessary mode is a good mode discrimination degree by appropriately selecting the number of the pairs of coupling holes 2 by utilizing the difference in the guide wavelength in the circular main waveguide 1. In the above embodiment has been give two pair to N sets of coupling holes 2 by the mode coupling type directional coupler, as shown in FIG. 2, two coupling provided at intervals l ₁ Hole 2 and spacing
A plurality of sets of two coupling holes 2a provided at l ₃ are provided with a certain interval l ₅ and an interval l ₆ which are obtained by using the above formula so that the coupling coefficient does not become small by increasing the number of coupling holes. , And N sets of coupling holes may be further provided. Further, in the above-mentioned embodiment, the two coupling holes 2 are used to provide the directivity, but the number of the coupling holes 2 may be three or more, and the spacing between the coupling holes 2 may be directed. By setting to, the same effect as the above-mentioned embodiment can be obtained. In addition, in the above embodiment, the circular main waveguide 1 has two
It is shown that one sub-waveguide 3, 3a is punched, but it is symmetrically 4
It is also possible to monitor the reflected power more accurately by providing more than one sub-waveguide and monitoring different reflected modes.

【The invention's effect】

As described above, according to the present invention, a pair of two coupling holes formed with a distance satisfying the condition that the coupling coefficient in the opening direction for monitoring the incident power high frequency of the sub-waveguide is 0 is set. , Since the groups are formed so as to have a spacing that satisfies the condition that the coupling coefficient in the opening direction that can monitor the reflected power high frequency of the sub-waveguide is the maximum, the coupling with the circular waveguide is performed. It is possible to increase the degree and give directionality, and it is possible to accurately monitor the incident power high frequency and the reflected power high frequency with respect to the circular main waveguide. Further, according to another invention, since the distance between the coupling holes and the distance between the pairs are different for each sub-waveguide, modes other than the fundamental mode propagating in the circular main waveguide are also monitored. There is an effect that can be.

[Brief description of drawings]

FIG. 1 is a sectional view showing a mode coupling type directional coupler according to an embodiment of the present invention, FIG. 2 is a sectional view showing a mode coupling type directional coupler according to another embodiment of the present invention, and FIG. Is a partially broken perspective view showing a conventional mode coupling type directional coupler, FIG. 4 is a sectional view showing the mode coupling type directional coupler shown in FIG. 3, and FIG. 5 is a mode coupling shown in FIG. It is sectional drawing in the surface perpendicular | vertical to the axis of the circular main waveguide of a mold directional coupler. 1 is a circular main waveguide, 2 and 2a are coupling holes, and 3 and 3a are sub-waveguides. In the drawings, the same reference numerals indicate the same or corresponding parts.

Front page continuation (72) Takashi Nagashima, Takashi Nagashima, No. 801 Nakahara, Nakayama, Naka-machi, Naka-gun, Ibaraki Prefecture 1 Inside the Naka Institute of the Japan Atomic Energy Research Institute (72) Naoki Nakamura 8-1-1 Tsukaguchihonmachi, Amagasaki City, Hyogo Prefecture Sanryo Denki Co., Ltd. (56) References Japanese Unexamined Patent Publication No. 56-2702 (JP, A) Actually developed 60-144301 (JP, U)

Claims (2)

[Claims] 1. A circular main waveguide capable of propagating a high power high frequency fundamental mode and a mode other than this fundamental mode, and a circular main waveguide spaced apart from each other in the circumferential direction, the same as the circular main waveguide in the radial direction. A plurality of sub-waveguides each having a dimension in a direction smaller than a diameter of the circular main waveguide and arranged in a tube axis direction of the circular main waveguide, the sub-waveguides of the circular main waveguide. In the mode-coupling type directional coupler having a plurality of coupling holes in the tube wall facing each other, there is an interval satisfying the condition that the coupling coefficient in the opening direction for monitoring the incident power high frequency of the sub-waveguide is 0. The two coupling holes formed by the above are formed as a set, and the sets are formed with a space satisfying the condition that the maximum coupling coefficient in the opening direction that can monitor the reflected power high frequency of the sub-waveguide is obtained. Mode-coupling type directivity characterized by If device. 2. The mode coupling type directional coupler according to claim 1, wherein the distance between the coupling holes and the distance between the groups are different for each sub-waveguide.