JPH04150401A - Mode-coupled type directional coupler - Google Patents

Abstract

PURPOSE:To increase the degree of coupling of plural auxiliary waveguides with a circular main waveguide even to a high frequency exceeding 100GHz so that the electric power made incident to and reflected by the circuit waveguide can be monitored exactly by providing the plural auxiliary waveguides against the circular main waveguide and providing plural sets of coupling holes in each auxiliary waveguide, with each set of the coupling holes being composed of plural holes. CONSTITUTION:On one auxiliary waveguide 3 side in the figure, the coupling holes 2 are provided at intervals l1 and each two adjacent holes constitute one set. A total of N sets of holes 2 is provided at regular intervals l2, with the total number of the holes 2 being 2N. On the other auxiliary waveguide 3a side, the holes 2a are provided at regular intervals l3 and each adjacent holes constitute one set. A total of N sets of holes 2a are provided at regular intervals of l4. When the auxiliary waveguides 3 and 3a are constituted in such way, the TE10 mode can be monitored from the intervals l1 and l2 satisfying a specific relation on one auxiliary waveguide 3 which uses the propagation mode of the main waveguide 1 as a TE04 mode and the incident power can be monitored at an opened end 5b.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a mode-coupled directional coupler used to monitor the output of a high-power millimeter-wave oscillator gyrotron used for plasma heating in a nuclear fusion experimental device.

[Conventional technology]

FIG. 3 is a partially cutaway perspective view showing a conventional mode coupling type directional coupler.
Circular main waveguide capable of propagating mn mode, 2 is a coupling hole, 3
is a sub-waveguide that couples the TEmn mode through the coupling hole 2. FIG. 4 is a cross-sectional view of the conventional mode-coupling type directional coupler shown in FIG. TEmn mode exits 5a and 5b are open ends of the sub waveguide 3. A plurality of coupling holes 2 having the same shape are provided at equal intervals β. FIG. 5 is a sectional view taken in a plane perpendicular to the central axis of the circular main waveguide 1 of the mode-coupled directional coupler. This shows that it is a rectangular waveguide. Next, the operation will be explained. First, let us consider the field wavelength λg, where the pipe wavelength of the TEmn mode in the circular main waveguide 1 is λg+.
The inner dimensions of the sub-waveguide are determined so that 2 is equal to λg. As a result, the 78mn mode incident from the entrance port 4a of the circular main waveguide 1 is TE in the sub waveguide 3. TE, which couples the mode through the coupling hole 2 but in the sub-waveguide 3. The mode propagates in the direction of the open end 5b because it is added to the 78mn mode in phase, but does not propagate in the direction of the open end 5a because the phase is canceled, and therefore has directionality. In addition, the number of coupling holes 2 should be as small as possible in order to improve frequency characteristics, but in order to accurately measure directionality using a low-output sweep oscillator, the degree of coupling should be 400.
It is desirable that it be larger than about dB, and therefore the number of coupling holes 2 is increased to some extent.

[Problem to be solved by the invention]

Since the conventional mode-coupling type directional coupler is configured as described above, the frequency is 100% as in the high-power millimeter-wave oscillator gyrotron used for plasma heating.
G) If the frequency is increased beyond 1z, the diameter d of the circular main waveguide 1 cannot be made smaller in order to increase the transmission power, so the tube wavelength λ of the 78 mn mode in the circular main waveguide 1
When g+ becomes close to the free space wavelength λ, and when the fundamental mode in the sub-waveguide 3 and the guide wavelength λg2 of the al T E + o mode are made equal to this, the value of the dimension a of the sub-waveguide 3 increases, The sub-waveguide 3 becomes oversized, and modes other than the fundamental mode also occur, making it difficult to monitor the output as a directional coupler. This invention was made to solve the above-mentioned problems, and it is possible to increase the degree of coupling on the circular main waveguide without increasing the dimensions of the sub-waveguide, even for high frequencies exceeding 100 GHz. The object of the present invention is to obtain a novel mode-coupling type directional coupler which is large in size, has excellent directivity, and can accurately monitor input power and reflected power to a circular main wave tube.

[Means to solve the problem]

The mode-coupling type directional coupler according to the present invention includes a circular main waveguide that propagates a fundamental mode and a mode other than the fundamental mode, and a circular main waveguide that is spaced apart from each other in the circumferential direction of the circular main waveguide, Dimension a in the same direction as the direction
is shorter than the diameter d of the circular main waveguide, and includes a plurality of sub-waveguides arranged in the axial direction of the main waveguide, and a plurality of coupling holes electromagnetically coupled to the cavity of each sub-waveguide. A pair of coupling holes are provided in the pipe wall of the circular main waveguide, and the distance between the coarse grooves is set to be different from each other in each sub-waveguide. It is.

[Effect]

In this invention, one set of a plurality of coupling holes is provided so that the phase of the mode in each sub-waveguide is canceled in one direction, so that the mode in the sub-waveguide is This makes it possible to provide directionality by preventing the mode from propagating. Further, by providing a plurality of sub-waveguides and making the distances between the plurality of pairs of coupling holes different from each other, it becomes possible to monitor modes other than the fundamental mode propagating through the circular main waveguide.

【Example】

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 3 and 3a are sub-waveguides arranged symmetrically with respect to the circular main waveguide 1, and on the side of the sub-waveguide 3, 2 is a coupling hole, and these are spaced apart! Two pieces provided with a number 1 form one set, and N groups are provided at equal intervals I12, a total of 2N pieces. Further, on the other side of the sub-waveguide 3a, 2a is a coupling hole, two of which are provided with an interval of 13 as IMi, and N sets are provided at equal intervals of 14. Here, the interval 2. and interval i! ,
3, and the interval 12 and the interval i4 are configured differently. Note that other components that are the same as those shown in FIG. 4 are designated by the same reference numerals, and redundant explanation will be omitted. By the way, for example, if the degree of coupling of the 78 mn mode due to one coupling hole 2 in one sub-waveguide 3 is C8, the incidence port 4a of the circular main waveguide 1 due to the two coupling holes 2 provided at an interval of 2 Sub-waveguide 3 of the TEmn mode incident on the
The coupling coefficient (■) toward the open end 5b of the sub waveguide 3 and the coupling coefficient (■) toward the open end 5a of the sub waveguide 3 can be expressed by the following equations, respectively. ■. C0 (1+exp( 4zz:,) λ. Vb -〇〇, 4 π Z (1+exp(j・λ,) 2πz, 2πZ C2C@ cos 2exp(j °) H
However, λ = 2Ag・−Ag・λg2−λg1 λ, −2λg+・7g2 λg2−]−λg Here, λg and 7g2 are respectively the circular main waveguide 1
and the guide wavelength in the sub waveguide 3. Therefore, in order to improve the directionality, Z= 2 m-nu λb (m+ C1, 2, 3, ・
-...-), it can be l Vb l-0, so for example, TE in one sub-waveguide 3
,. Since the phase of the mode is canceled in the direction of the open end 5a, its T E +. The mode does not propagate and therefore can have directionality. Also, z mm z λt (mz C1, 2131--
-----) --(x), 1 is the maximum, and a large degree of bonding can be obtained with a small number of bonding holes 2. Therefore, 11Jubi1λb+i! ,! - Yasu, --- If 2N coupling holes 2 are provided so that the relationship (2) is obtained, 1
A mode coupling type directional coupler with good directionality can be obtained even for high frequencies exceeding 00GI (z). Similarly, in the other sub-waveguide 3a, for example, T E
The above (1) is made so that the + mode is given directionality so that it does not propagate in the direction of the opening end 5ab but in the direction of the opening end 5bb, and a large degree of coupling is obtained in the coupling hole 2a. ) and the interval Qs, e in the same way as the equation (2).
, can be set. With such a configuration, if the propagation mode of the circular main waveguide 1 is the TEoa mode, one of the sub waveguides 3 can be set to 'El. The incident power can be monitored at the open end 5b.On the other hand, the millimeter waves reflected on the circular main waveguide l are due to discontinuity or bending in the amount of waveguide, or reflection from a load, etc., and the mode However, by providing the other sub-waveguide 3a, for example, T E
It is also possible to monitor reflected power in + + mode. - As an example, the propagation mode of the circular main waveguide 1 is TE, the mode and frequency are 120GIiz, the diameter d of the circular main waveguide 1 is 37 mm, and the vertical dimension a of the sub waveguide 3 is 2.032 m.
m, and the lateral inner dimension is 1.016 mm, then the TE in the circular main waveguide 1, the internal wavelength of the mode λg1 is 2.6
07 mm, TE at sub-waveguide 3. The in-tube wavelength λg2 of the mode is 3.167 mm, and the above-mentioned 2 m and C2
By setting ゜C2-1, 1+C2,1511
m+, j2z-14.75mm. in this way,
When the spacing between the coupling holes 2 is set, the directionality becomes infinite in dB in calculation, and the degree of coupling C is calculated by dividing the number N of pairs of coupling holes 2 by 40. 77dB
Then, 2πi. C=-201og+o(2NCocos A, )
C40 (dB). This makes it possible to accurately measure directionality using a low-output sweep oscillator. Moreover, the degree of mode discrimination against unnecessary modes can be improved by appropriately selecting the number of pairs of coupling holes 2 by utilizing the difference in the wavelength within the circular main waveguide 1. In addition, in the above embodiment, there are N sets of coupling holes 2, each consisting of two coupling holes 2.
A mode-coupling type directional coupler was obtained by using the method shown in FIG. 2, but as shown in FIG. The two coupling holes 2a provided in 2.3 are spaced at a certain distance using the above-mentioned formula to prevent the coupling coefficient from becoming small by increasing the number of coupling holes. A plurality of sets may be provided, and these may be set as 1&ll, and further N&ll coupling holes may be provided. Further, in the above embodiment, the two coupling holes 2 provide directionality, but the number of coupling holes 2 may be three or more, and the spacing between the coupling holes 2 may be adjusted so as to provide directionality. By setting it to , the same effect as in the above embodiment can be achieved. In the second embodiment, 2 for the circular main waveguide 1.
Although four or more sub-waveguides 3 and 3a are shown in the diagram, four or more sub-waveguides can be installed symmetrically to monitor the different reflected modes to further improve the reflected power. It is also possible to monitor accurately. [Effects of the Invention] As described above, according to the present invention, a plurality of sub-waveguides are provided for a circular main waveguide, and each sub-waveguide is provided with a plurality of sets of coupling holes. Therefore, 100
Even for high frequencies exceeding GH2, the degree of coupling with the circular main waveguide is increased without increasing the dimensions of the sub-waveguide, and the incident power and This has the effect of making it possible to accurately monitor reflected power.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a mode-coupled directional coupler according to one embodiment of the present invention, FIG. 2 is a cross-sectional view showing a mode-coupled directional coupler according to another embodiment of the present invention, and FIG. 4 is a partially cutaway 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 type directional coupler shown in FIG. 3. FIG. 3 is a cross-sectional view in a plane perpendicular to the axis of the circular main waveguide of the type directional coupler. 1 is a circular main waveguide, 2 and 2a are coupling holes, and 3 and 3a are sub waveguides. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Agent Masu Oiwa

Claims (1)

[Claims] A circular main wave pipe capable of propagating the fundamental mode of a high power high frequency wave and modes other than the fundamental mode; shorter than the diameter of the circular main wavetube,
and a plurality of sub-waveguides arranged in the tube axis direction of the circular main waveguide, and a plurality of coupling holes that are electromagnetically coupled to the cavities of each of these sub-waveguides are set as one set. , each of the coupling holes in the plurality of pairs with equal distances between the pairs is provided in the tube wall facing the sub-waveguide of the circular main waveguide; Mode coupling type directional coupler with different distances from each other.