JPH054842B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a directional coupler used in a microwave band of approximately 1 GHz or higher.

[Conventional technology]

Figure 5A uses a conventional double-ridge waveguide.
FIG. 5B is a perspective view of a directional coupler that utilizes mutual interference of TE ₁₀ , TE ₂₀ , and TE ₃₀ modes;
FIG. 3 is a cross-sectional view taken along line A-A' in FIG. Fifth
In Figures A and B, a first rectangular waveguide 10 and a second rectangular waveguide 11 each have a height a parallel to the E plane and a width b parallel to the H plane.
The waveguides 10, 1 are parallel to each tube axis in the longitudinal direction of 1.
1 and are formed so that the respective E surfaces of the electrodes face each other and are spaced apart by a predetermined distance s. Here, each rectangular waveguide 10 and 1
1 are coupled to each other via a coupling hole 5 of a rectangular parallelepiped-shaped coupling portion 6 provided at the center of the side wall of the facing E surface. This coupling hole 5 has a length L in the longitudinal direction.
The cross-sectional shape of the coupling hole 5 is a rectangle having a width d parallel to the E plane of the coupling hole 5 and a width s parallel to the H plane. Here, two rectangular waveguides 10 and 11
The cross-sectional shape perpendicular to the tube axis of the coupling portion 6 of the directional coupler having the coupling hole 5 and the coupling hole 5 is a double-ridge waveguide as shown in FIG. 5B. In this directional coupler, each end of the rectangular waveguide 10 is used as a signal input terminal 1 and a signal output terminal 3, and each end of the rectangular waveguide 11 is used as a signal input terminal 2 and a signal output terminal, respectively. It is set as output terminal 4.

If the width s of the coupling hole 5 parallel to the H plane is appropriately set, the TE ₁₀ , TE ₂₀ and TE ₃₀ modes can propagate within the coupling portion 6 as is known. Here, the phase constants of each mode are β ₁₀ , β ₂₀ , and β ₃₀ , respectively, and the coupling hole 5 is adjusted so as to satisfy the relationship (β ₁₀ − β ₃₀ )・L=2π……(1). When the length L in the longitudinal direction is set, the microwave signal input from the signal input terminal 1 is outputted to the signal output terminals 3 and 4 without reflection. Here, the input power of the microwave signal input to signal input terminal 1 is P ₁ , and the output power output to signal output terminals 3 and 4 is
Assuming P ₃ and P ₄ , P ₃ = P ₁ cos ² {(β ₂₀ − β ₃₀ )・L/2}... (2) P ₄ = P ₁ sin ² {(β ₂₀ − β ₃₀ )・L /2}...(3) holds true.

Figure 7 shows the relationship between the height d of the coupling hole 5, which is the width parallel to the E plane of the coupling hole 5, and the difference in phase constant (β ₁₀ −β ₃₀ ) and (β ₂₀ −β ₃₀ ). be. From FIG. 7, it can be seen that the difference in phase constant (β ₂₀ −β ₃₀ ) increases in proportion to the height d of the binding hole 5, while the difference in phase constant (β ₁₀ −β ₃₀ ) increases in proportion to the height d of the binding hole 5. It can be seen that even if the height d is changed, there is almost no change. Therefore, the length L of the coupling hole 5 is adjusted so as to satisfy the non-reflection condition of equation (1) above.
By setting , it is possible to construct a directional coupler having an arbitrary degree of coupling in proportion to the height d of the coupling hole 5.

Furthermore, the directional coupler using the double-ridge waveguide shown in FIGS. 5A and 5B described above is different from the single-ridge waveguide having the same height d of the coupling hole 5 whose cross-sectional shape is shown in FIG. It is known that the directional coupler has almost the same frequency characteristics of the difference in phase constant and the frequency characteristics of the coupling loss between the input and output terminals.

Furthermore, in the conventional directional coupler described above, by increasing the height d of the coupling hole 5, the first rectangular waveguide 10 and the second rectangular waveguide 1
It is known that it is possible to make the coupling between 1 and 1 more dense and reduce the coupling loss.

[Problem that the invention seeks to solve]

However, if the height d of the coupling hole 5 is significantly increased as shown in FIG. 8, the difference in phase constant (β ₂₀
−β ₃₀ ) frequency characteristics deteriorate and become narrow band,
As a result, there has been a problem in that a broadband, tightly coupled directional coupler cannot be realized.

For example, as a method for realizing a directional coupler having a large degree of coupling, it can be realized by cascading two or more of the conventional directional couplers shown in FIGS. 1A and B described above. There were problems in that the external shape became larger and heavier.

An object of the present invention is to solve the above problems and provide a directional coupler that is small and lightweight, has a wide band, and has a high degree of coupling.

[Means for solving problems]

The present invention has a pair of rectangular waveguides arranged close to each other with their E planes facing each other parallel to the tube axis, and a coupling hole of a predetermined length that is uniform in the tube axis direction and is provided on each E plane. In a directional coupler whose shape is set so that the coupling part consisting of a coupling hole and the rectangular waveguides at both ends thereof can propagate TE ₁₀ , TE ₂₀ , and TE ₃₀ modes, the coupling hole is perpendicular to the tube axis of the coupling hole. The dimension of the openings at both ends of the coupling hole in the direction parallel to the E plane is longer than the dimension of the central part of the coupling hole in the direction parallel to the E plane.

[Effect]

With the above configuration, the pair of rectangular waveguides are coupled through the coupling hole, and TE ₁₀ ,
TE ₂₀ and TE ₃₀ modes are allowed to propagate through the coupling hole. Further, for example, the height parallel to the E plane of the central part of the joint part is the same as the height of the conventional example, and as described above, the height of the joint hole in the cross-sectional shape perpendicular to the tube axis of the joint hole is By making the dimension of the openings at both ends in the direction parallel to the E plane longer than the dimension of the central part of the coupling hole in the direction parallel to the E plane, the external shape of the directional coupler can be prevented from increasing. , it is possible to obtain a large degree of coupling between the pair of rectangular waveguides without making the frequency characteristics of the directional coupler narrower than in the conventional example.

〔Example〕

FIG. 1A is a perspective view of a directional coupler using a double-ridge waveguide, which is an embodiment of the present invention.
FIG. 1B is a longitudinal sectional view taken along line B-B' in FIG. 1A. Components in FIGS. 1A and 1B that are the same as those in the above-described drawings are designated by the same reference numerals.

This directional coupler is different from the conventional directional coupler shown in FIGS. 5A and 5B in that the shapes of the coupling holes are different, and specifically, each rectangular waveguide 10
Each ridge part 2 at each end of the coupling hole 5a in contact with 1
1, 22 edge portions 21a, 21b, 22a, 2
2b is chamfered, and as shown in FIG. 31 in a direction parallel to the E plane is longer than the height d of the central part 32 of the coupling hole 5a in a direction parallel to the E plane, symmetrically with respect to the central part 32. It is said that The above differences will be explained below.

In FIGS. 1A and B, as in the conventional example, E
A first rectangular waveguide 10 and a second rectangular waveguide 11 each having a height a parallel to the plane and a width b parallel to the H plane are connected to each other in the longitudinal direction of the waveguides 10 and 11. The E planes of the waveguides 10 and 11 are opposed to each other parallel to the axis and are separated by a predetermined distance s, and each rectangular waveguide 10 and 11 has a side wall between each waveguide 10 and 11. are connected to each other through a connecting hole 5a of a connecting portion 6a provided at the center of each E surface in the tube axis direction. Here, the coupling hole 5a has a uniform predetermined length L in the tube axis direction, and the cross-sectional shape of the coupling hole 5a perpendicular to the tube axis is a double-ridge waveguide as shown in FIG. 1B. In the coupling portion 6a located between the waveguides 10 and 11, a ridge protrudes symmetrically by the same height downward and upward from the height of the upper and lower inner walls of each rectangular waveguide 10 and 11, respectively. Part 21,
22 are formed at a predetermined distance d in the center portion 32 of the coupling hole 5a.

The cross-sectional shape perpendicular to the tube axis of each of the ridge parts 21 and 22 is the ridge part 2 at the opening 30 and 31 at the end of the coupling hole 5a on the waveguide 10 and 11 side, respectively.
1, 22 each edge portion 21a, 21b, 22a,
22b is chamfered so as to be symmetrical with respect to a center line parallel to the E plane at the center position between each waveguide 10, 11 and to have a linear shape in cross section. Here, each chamfered edge portion 21a, 21b, 22
a and 22b have a height c in a direction parallel to the E plane and a width c in a direction parallel to the H plane. Here, the reason why the shape of the chamfer is symmetrical with respect to the center line of the central portion 32 is to prevent the mutual interference of TE ₁₀ , TE ₂₀ and TE ₃₀ from occurring at the same time for each of the rectangular waveguides 10 and 11. This is because the symmetry condition is caused to occur under certain conditions, and when this symmetrical condition is not satisfied, various frequency characteristics described later deteriorate, resulting in a narrow band compared to the conventional example. Furthermore, the length L of the coupling hole 5a in the tube axis direction is TE ₁₀ ,
The above (1) allows propagation of TE ₂₀ and TE ₃₀ modes.
is set by satisfying the formula.

In the directional coupler configured as above, as described above, each rectangular waveguide 10 of the coupling hole 5a in the cross-sectional shape perpendicular to the tube axis of the coupling hole 5a,
The height (2c+d) of the openings 30 and 31 at both ends on the 11 side in the direction parallel to the E plane is the center part 32 of the coupling hole 5a.
It is longer than the height d parallel to the E plane of .

Hereinafter, various theoretical calculation values and measured values for an example of a directional coupler using a double-ridge waveguide configured as described above and the above-mentioned conventional example will be shown. Here, for each rectangular waveguide 10, 11, a=
Using a WRI-320 type rectangular waveguide with a diameter of 3.556 mm and b = 7.112 mm, the height d of the central portion 32 of the coupling hole 5.5a is 0.7.
mm, width s parallel to H plane of coupling holes 5, 5a = 3.0 mm,
Edge portions 21a, 21b, 22a, 22 of the embodiment
The above height of b and width c = 1.0mm, frequency 27G
Calculations and measurements were performed from Hz to 33GHz.

FIG. 9 shows the difference in phase constant (β ₁₀ −β− ₃₀ ) and (β ₂₀
-β ₃₀ ) is a graph showing theoretically calculated values of frequency characteristics. From FIG. 9, it can be seen that the frequency characteristics of the difference in phase constants (β ₁₀ −β ₃₀ ) of the embodiment are almost the same as those of the conventional example, but the difference in phase constants of the embodiment (β ₂₀ −β ₃₀ ) is a larger value compared to the conventional example. Also, the difference in phase constant (β ₁₀
−β ₃₀ ) and (β ₂₀ −β ₃₀ ) frequency characteristics,
It can be seen that there is almost no difference in deterioration of frequency characteristics between the example and the conventional example.

FIG. 10A is a graph showing the frequency characteristics of the coupling loss between input and output terminals 1-3 and 1-4 of the directional coupler of the conventional example, and FIG. 10B is a graph of the directional coupler of the embodiment. It is a graph which shows the frequency characteristic of the coupling loss between input-output terminals 1-3 and 1-4. 10th
From Figures A and B, the measured values and theoretically calculated values for each characteristic almost match, and the coupling loss between the input and output terminals 1-4 of the directional coupler of the example is smaller than that of the conventional example. On the other hand, it can be seen that the coupling loss between the input and output terminals 1-3 of the directional coupler of the example is larger than that of the conventional example. Therefore, as in the embodiment, the edge portions 21a, 21b, 22a, 2
By chamfering 2b, a directional coupler with a higher degree of coupling than the conventional example can be realized without enlarging the external shape of the directional coupler.

Furthermore, FIG. 11A is a frequency characteristic diagram showing the coupling loss between each input terminal 1-1 and 1-2 of a conventional directional coupler, that is, the output level of reflected waves and unnecessary waves. FIG. B is a frequency characteristic diagram showing the coupling loss between each input terminal 1-1 and 1-2 of the directional coupler of the embodiment, that is, the output level of reflected waves and unnecessary waves. From Figure 11 A and B, approx.
It can be seen that each coupling loss between 1 and 1 and between 1 and 2 of 20 dB or more can be obtained, and reflected waves and unnecessary waves can be practically removed.

In the above embodiments, a directional coupler using a double-ridge waveguide has been described. The directional coupler using this single-ridge waveguide may be provided with only one ridge portion 21.
As is well known, it has almost the same various frequency characteristics as the directional coupler using the double-ridge waveguide.

Furthermore, in the joint portion 6a of the above embodiment,
Although the ridge portions 21 and 22 are formed to protrude symmetrically by the same height downward and upward from the height of the upper and lower inner walls of each of the rectangular waveguides 10 and 11, the present invention is not limited thereto. , separated by a predetermined interval d in the center portion 32 and edge portions 21a, 21b, 2
If 2a and 22b are chamfered, the ridge part 2
1 and 22 do not have to be the same height.

In the above embodiment, each edge portion 21a, 21b, 22a, 22b of the ridge portions 21, 22 is chamfered as described above, but the present invention is not limited to this, and as shown in FIG. The mutually opposing top portions 21c and 22c may have a circular or elliptical arc shape in cross section perpendicular to the tube axis. Furthermore, as shown in FIG. 4, a single-ridge waveguide directional coupler may be configured, which includes a ridge portion 21 having an apex 21c having an elliptical arc cross-section. As is well known, it has the same various frequency characteristics as the double-ridge waveguide directional coupler.

Therefore, the gist of the present invention is that the height in the direction parallel to the E plane of the openings 30 and 31 at both ends of each rectangular waveguide side of the coupling hole 5a in the cross-sectional shape perpendicular to the tube axis of the coupling hole 5a is It is longer than the height of the central portion 32 of the coupling hole 5a in the direction parallel to the E plane, and as a result, the degree of coupling is greater than that of the conventional example with the same external shape as the conventional examples shown in FIGS. 5A and B. A broadband directional coupler can be obtained.

Furthermore, with conventional directional couplers that utilize mutual interference between TE ₁₀ , TE ₂₀ , and TE ₃₀ modes, two or more directional couplers must be connected in series to obtain the required degree of coupling. Even if a degree of close coupling is required, by applying the present invention, the required degree of coupling can be obtained with one directional coupler, and it is also effective in reducing the size and weight of the directional coupler.

Furthermore, in conventional directional couplers, the electric field concentrates at the openings 30 and 31 at both ends of the coupling hole 5, causing dielectric breakdown in response to input of large power, so the allowable input power is severely restricted. According to the invention, the opening 3
Since the area of both ends of the coupling hole 5a at 0 and 31 can be increased, electric field concentration at both ends of the coupling hole 5a is alleviated, and there is also an advantage that input allowable power can be increased.

Although the present invention has been described as a directional coupler with a fixed degree of coupling, conventional directional couplers in which TE ₁₀ , TE ₂₀ , and TE ₃₀ utilize mutual interference of modes have coupling holes as described above. By changing only the height d parallel to the E plane of each rectangular waveguide 1
It has the characteristic that the degree of coupling between 0 and 11 can be changed, and it goes without saying that the directional coupler of the present invention also has this characteristic.

〔Effect of the invention〕

As detailed above, according to the present invention, in the cross-sectional shape perpendicular to the tube axis of the coupling hole of the conventional directional coupler, the dimensions of the openings at both ends of the coupling hole in the direction parallel to the E plane are set as above. By making the coupling hole longer than the dimension in the direction parallel to the E plane at the center of the coupling hole, a large degree of coupling can be obtained without increasing the external shape of the directional coupler and without deteriorating the frequency characteristics. be able to. Therefore, in conventional directional couplers, two or more directional couplers had to be connected in series to obtain the required degree of coupling, but with the present invention, one directional coupler has to be connected in series. A high degree of coupling can be obtained in the device, and it is effective in reducing the size and weight of the directional coupler.

In addition, in conventional directional couplers, the electric field concentrates at the openings at both ends of the coupling hole, causing dielectric breakdown in response to high power input, so the allowable input power is severely restricted. Since the area of both ends of the coupling hole in the opening can be increased, electric field concentration at both ends of the coupling hole is alleviated, and there is also an advantage that input allowable power can be increased.

[Brief explanation of the drawing]

FIG. 1A is a perspective view of a directional coupler using a double-ridge waveguide, which is an embodiment of the present invention, and FIG. 1B is a longitudinal cross-sectional view taken along line BB' in FIG. 1A.
2, 3, and 4 are longitudinal cross-sectional views of a directional coupler according to another embodiment of the present invention, and FIG. 5A is a longitudinal sectional view of a directional coupler using a conventional double-ridge waveguide. A perspective view, FIG. 5B is a vertical cross-sectional view taken along line A-A' in FIG. 5A, FIG. 6 is a vertical cross-sectional view of a conventional directional coupler using a single-ridge waveguide, and FIG. is a graph showing the theoretically calculated value of the difference in phase constant with respect to the height of the coupling hole of a conventional directional coupler, and Figure 8 is the theoretically calculated value of the frequency characteristic of the difference in phase constant of the conventional directional coupler. FIG. 9 is a graph showing theoretically calculated values of the frequency characteristics of the difference in phase constant of the directional couplers of the conventional example and the embodiment, and FIGS. Graphs showing measured values and theoretically calculated values of frequency characteristics of coupling loss between output terminals, Figures 11A and B are measured values and theoretical values of frequency characteristics of coupling loss between input and output terminals of the conventional example and the embodiment, respectively. It is a graph showing calculated values. 1, 2... Signal input terminal, 3, 4... Signal output terminal, 5, 5a... Coupling hole, 6, 6a... Coupling part, 10
...first rectangular waveguide, 11...second rectangular waveguide,
21, 22...Rigid part, 21a, 21b, 22
a, 22b...edge portion, 30, 31...openings at both ends of the coupling hole, 32...center portion of the coupling hole.

Claims (1)

[Claims] 1 A pair of rectangular waveguides arranged close to each other with their E planes facing each other parallel to the tube axis, and a coupling hole provided in each E plane and having a predetermined length that is uniform in the direction of the tube axis. In a directional coupler whose shape is set so that the coupling portion formed by the rectangular waveguides at both ends can propagate TE ₁₀ , TE ₂₀ and TE ₃₀ modes, the cross-sectional shape of the coupling hole perpendicular to the tube axis is A directional coupler characterized in that the dimension of the openings at both ends of the coupling hole in the direction parallel to the E plane is longer than the dimension of the central part of the coupling hole in the direction parallel to the E plane.