JPS6117162B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a flexible waveguide for electromagnetic waves that transmits ultra-high frequency linearly polarized electromagnetic waves and can be manufactured continuously. In recent years, in addition to the conventional rectangular and circular waveguides with a unit length of 3 to 4 m, waveguides for transmitting the electromagnetic waves mentioned above have been used.
A long flexible waveguide (hereinafter referred to as elliptical waveguide 1) having a length of about 50 to 150 m and having flexibility that can be handled in the same way as a coaxial cable has been put into practical use. There is. Moreover, Fig. 1 A, Fig. 1 B (A- in Fig. 1 A)
As shown in Figure A), some of these waveguides are in the form of longitudinally seamed welded pipes so that they can be manufactured in one continuous length, and the surface of the pipe is welded to further increase flexibility. A spiral or bellows-like corrugated corrugation is applied to the top in the length direction. In addition, this long elliptical flexible waveguide eliminates the deterioration of characteristics caused by attenuation, reflection, airtight leakage, etc. at numerous connection points that tend to occur when using conventional waveguides, and it In addition, transportation, installation,
It has the advantage of being easy to handle and being economical. However, in such an elliptical waveguide 1, the ratio of the frequency interval between the fundamental wave cutoff frequency and the first higher-order wave cutoff frequency and the center frequency of those frequencies, that is, the ratio band, is different from that of the conventional rectangular waveguide. It is known that it is narrower and has higher impedance than the waveguide 2, making broadband matching difficult. On the other hand, among the conventionally known waveguides, there is a longitudinal axis inside the rectangular waveguide 2, such as the double-sided rigid waveguide shown in FIG. 2A and the one-sided rigid waveguide shown in FIG. The rectangular ridge waveguide 3 with a ridge 6 on the long side along the waveguide has a capacitance loaded inside the waveguide, and has a lower characteristic impedance than a waveguide without a ridge. Furthermore, it is known that the specific band is wide. In other words, if the inner diameter dimensions of the long and short sides are the same, the rectangular ridge waveguide 3 is the rectangular waveguide 2 without ridges.
It is known that a ridge waveguide has an upper limit frequency determined by a higher first-order high-order wave cut-off frequency than that of a ridge waveguide, and has smaller dimensions if the same upper limit frequency is used. However, due to the structure of such a rigid waveguide, it is also true that manufacturing a long one requires many difficulties and costs. Therefore, in this invention, the broadband properties and low impedance properties of the conventional rectangular rigid waveguide 3 are incorporated into a long flexible waveguide, and a wider usable band is achieved compared to the conventional long flexible waveguide. A long flexible waveguide with a cocoon-shaped cross section that has low loss and easy broadband matching with a rectangular waveguide, is relatively easy to manufacture, and can be manufactured continuously at low cost. We are proposing a tube. In a broad sense, the configuration of the present invention is as follows:
In a flexible waveguide for electromagnetic waves, when considering the inner diameter cross-sectional shape as a smooth tube that is electrically equivalent, there are It is a cocoon-like shape that is equivalent to a symmetrically loaded lip, and its inner diameter cross-sectional shape is expressed by the functional formula (x ² + y ² ) ² + (4b ² −a ² ) (x ² + y ² ) in the x-y orthogonal coordinate system. )=4b ² x ² where 0.40<k<0.45 (k=b/a) 1.00<2a/A<1.08 2a is the long axis diameter of the cocoon-shaped cross section A is the long side diameter of the corresponding rectangular waveguide The length 2√ ² −4 ² results in a flexible waveguide for electromagnetic waves, which is set to be expressed by the minor axis diameter of the eyebrow-shaped cross section. In addition, in the present invention, on the surface of a metal tube with a thin tube wall,
In a flexible waveguide for electromagnetic waves that has a spiral or bellows-like corrugation and is flexible, when considering the inner diameter cross-sectional shape as a smooth tube that is electrically equivalent, it is an elliptical waveguide. It is a cocoon-like shape that is equivalent to symmetrically loading ribs on the tube walls facing each other along the long axis diameter ^{of 2} ) ² + (4b ² − a ² ) (x ² + y ² ) = 4b ² x ² …(1) where 0.40<k<0.45 (k=b/a) 1.00<2a/A<1.08 2a is The major axis diameter of the cocoon-shaped cross section ^is set so that A is the length of the long side of the corresponding ^rectangular waveguide to be connected. A spiral or bellows-like corrugated corrugation applied in the length direction on the pipe wall of is expressed by the function equation in the parameters of equation (1) above. Here, k ₁ and a ₁ are parameters representing the blister-shaped cross-sectional shape of the valley part of the corrugation, and k ₂ and a ₂
is also a parameter representing the cocoon-shaped cross-sectional shape of the mountain portion. Also provided is a flexible waveguide for electromagnetic waves set in the shape represented by . DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be explained below by comparing the flexible waveguide for electromagnetic waves of the present invention with a conventional one using the drawings. Note that the corrugation along the longitudinal axis will be described later, but first consider the cross-sectional shape of a smooth tube, which is considered to be electrically equivalent to the cross-sectional shape of a waveguide. 3A and 3B illustrate the basic cross-sectional shape of a long flexible waveguide with ridges, excluding the corrugation, according to an embodiment of the present invention. Figure 3A shows a cocoon-shaped waveguide 4 corresponding to the double-sided rigid waveguide in Figure 2A, while Figure 3B shows a bead-shaped waveguide 5 corresponding to the one-sided rigid waveguide in Figure 2A. are shown respectively. As an example of the cross-sectional shape of the cocoon-shaped flexible waveguide corresponding to the double-sided ridges in FIG.
Generally, it is expressed by the functional formula (x ² +y ² ) ² + (4b ² -a ² ) (x ² +y ² )=4b ² x ² (Booth's string-like linear shape) in an orthogonal coordinate system: 2b<a. However, 2a represents the long axis diameter of the cocoon-shaped cross section, and 2√ ² −4 ² represents the short axis diameter of the cocoon-shaped cross section. Regarding the functional formula representing the above cross-sectional shape,
The reason why we say "exactly" or "approximately" is because when molding such a waveguide, it is possible to approximate the cross-sectional shape by connecting several circular arcs for ease of processing. However, when considering the shape of the waveguide tube wall, the shape based on this functional formula and inequality is It is not necessarily an appropriate shape or range of inequality.For example, when b/a = 0.35, 0.48, the ratio of the major axis and minor axis of the waveguide is 1:
71, 1: 0.28, and from the viewpoint of electrical characteristics, compared to a rectangular waveguide, the former has a small attenuation and is desirable, but the frequency band that can be used in the fundamental mode is narrow and the characteristic impedance is very large, and the latter has a large attenuation. , the characteristic impedance becomes lower. Therefore, in any case, considering that a rectangular waveguide is connected to both ends, electrically it cannot be put to practical use except for special purposes. On the other hand, mechanically, the former is difficult to twist, and if deformation or deviation from the specified dimensions occurs, it will have a large effect on electrical performance, and the latter is difficult to manufacture due to its flatness, and the flexibility of the H-plane There are disadvantages such as loss of quality. Therefore, we considered connection with a rectangular waveguide, and in terms of electrical characteristics, (i) wide usable frequency band, (ii) low transmission loss, and (iii)
In order to facilitate broadband matching with the rectangular waveguide to be connected, the parameters or coefficients in the above equation should be adjusted to achieve a cross-sectional shape in which the cutoff frequency and characteristic impedance of the fundamental mode wave are close to the characteristics of the rectangular waveguide. a,
By varying b and K (=b/a), the relationship between the cross-sectional shape and electrical properties was analyzed by numerical calculation. As a result, it was found that in the frequency band below 6 GHz, the cross-sectional shape of a Booth string-shaped waveguide is appropriate if each parameter has a value within the following range. . That is, 0.40<K<0.45 (K=b/a) 1.00<2a/A<1.08 Here, A is the length of the long side of the rectangular waveguide to be connected. As a specific example of the cocoon-shaped waveguide 4 using these values, we will take a Booth string-like linear waveguide with the dimension shown below, and the major axis diameter and minor axis diameter are shown in Figure 4. , mutually corresponding rectangular waveguides 2,
A conceptual diagram for shape comparison with the elliptical waveguide 1 is shown, and
A comparison of the electrical properties of each is shown in Table 1 below. The demension and other comparison conditions of the various waveguides in Table 1 are as follows. (1) Major axis diameter A = 40 mm (2) Minor axis diameter B = 20 mm {For rectangular waveguide 2} B = 24 mm {Maximum minor axis diameter of elliptical waveguide 1 and cocoon waveguide 4 Value} (3) Cocoon shape k=b/a=0.4237 (4) Frequency f=6.175GHz (5) Waveguide material Pure copper

【table】

[Table] In the above table Characteristic impedance = (Voltage between top and bottom walls) /
(Axial surface current)
From Table 1, it can be seen that the ratio band between the fundamental wave cutoff frequency and the first higher order wave cutoff frequency of the cocoon-shaped waveguide 4 is wider than that of the elliptical waveguide 1. In addition, the cocoon-shaped waveguide 4 has a characteristic impedance that is between the values of the rectangular waveguide 2 and the elliptical waveguide 1, and as can be inferred from the shape comparison diagram in FIG. Even when directly connected to the rectangular waveguide 2, the susceptance can be made smaller than that of the elliptical shape, so it is known that impedance matching can be more easily achieved with the rectangular waveguide 2 of standards such as JIS and IEC. Next, let's talk about corrugation. Corrugations are formed by stamping concave portions along the length of the wall of a smooth tube. As shown in the BB' cross-sectional view in Figure A, a corrugated corrugation with a sinusoidal waveform or a vertical cross-sectional shape similar to a sinusoidal wave is desirable. Regarding the pitch of this corrugation, it is stated that in the case of conventional corrugated waveguides, it is roughly 1/4 or less of the free space wavelength, but in the prototype test of a cocoon-shaped waveguide with corrugation, The results show that when forming the tube wall thickness t into a cocoon-shaped cross-sectional shape, the thickness t is approximately 100 times smaller than the major axis 2a of the waveguide, so that the processability is not impaired and the formed tube is not easily deformed. Even if you choose 1 and provide a polyethylene layer on the outer wall surface of the pipe wall to increase weather resistance and mechanical strength, you can still obtain the flexibility and torsion properties necessary for installation, and maintain the electrical properties even after installation. It has been found that in order to minimize the change in the pitch, the ratio of the pitch to the major axis should be selected to be approximately 0.12 to 0.25. Also, regarding the depth of the corrugation selected under the same conditions and reasons as above, the depth of the corrugation should be
It is sufficient if it is about 0.025 to 0.06, and this is the shape of the valley part stamped in the cross-sectional shape of the waveguide (indicated by suffix 1).
Shape of the part of the mountain that does not undergo stamping (Saphics 2)
(represented by ) using the above parameters, those having the following relationship have good electrical and mechanical properties. In the case of the string-like shape of the booth: 0.980<K ₂ /K ₁ <0.995 (K=b/a) 1.05<a ₂ /a ₁ <1.15 Here, the inequality expressing the cocoon-shaped shape and the range shown in the above inequality An example of the corrugation depth is found as follows. In addition, in this calculation, a 6 GHz band waveguide is considered, and all parameters are used with intermediate values within the ranges shown in each inequality. ●Long side length of rectangular waveguide: A=40mm ●Dimensions of valley part of eyebrow-shaped corrugated waveguide: 2a ₁ = 1.04A=41.6mm, a ₁ = 20.8mm k ₁ = 0.425 √ ² ₁ −4 ² ₁ =a ₁ √1−4 ² ₁ =10.96mm ●Dimensions of the crest of the eyebrow-shaped corrugated waveguide: a ₂ =1.1 a ₁ =22.88mm k ₂ =0.9875 k ₁ 0.420 √ ² ₂ − 4 ² ₂ = a ₂ √1-4 ² ₂ = 12.41mm ● Equivalent major axis of the eyebrow-shaped corrugated waveguide: 2a = 43.68 mm ● Ratio between the depth of corrugation and its equivalent major axis: On the major axis: 2.08 mm, 0.048 On the minor axis: 1.45 mm, 0.033 or more Regarding the cocoon-shaped flexible waveguide 4 of this invention,
The range of parameters of the functional expression expressing the cross-sectional shape and corrugation depth, which are its characteristics, has been explained. This waveguide is extremely effective in transmitting ultra-high frequency linearly polarized electromagnetic waves, and is highly practical as a feeding waveguide for a microwave antenna, for example.

[Brief explanation of the drawing]

Figure 1A is a cross-sectional view of a conventional elliptical flexible waveguide, Figure 1B is a vertical cross-sectional view of Figure 1A in the direction of arrow AA'',
Figure 2A is a cross-sectional view showing a conventional double-sided rigid waveguide, Figure 2B is a cross-sectional view showing a conventional single-sided rigid waveguide, and Figure 3A is a cross-sectional view of the cocoon-shaped waveguide of the present invention. Figure 3A is a cross-sectional diagram of a magatto-shaped waveguide loaded on one side, and Figure 4 is a cocoon-shaped waveguide of the present invention.
A conceptual diagram comparing the cross-sectional shapes of a rectangular waveguide and an elliptical waveguide. FIG. It is a BB″ cross-sectional view of Figure A. In each figure, 1 is an elliptical waveguide, 2 is a rectangular waveguide, 3 is a rectangular rigid waveguide,
4 is a cocoon-shaped waveguide, and 5 is a bead-shaped waveguide.

Claims (1)

[Claims] 1. In a flexible waveguide for electromagnetic waves,
Its inner diameter cross-sectional shape is a cocoon-like shape equivalent to that of an elliptical waveguide with ridges symmetrically loaded on the tube walls facing each other along the long axis, and its inner diameter cross-sectional shape is x-
Functional formula of y orthogonal coordinate system (x ² + y ² ) ² + (4b ² − a ² ) (x ² + y ² ) = 4b ² x ² …(1) where 0.40<k<0.45 (k=b/a ) 1.00<2a/A<1.08 2a is the long axis diameter of the cocoon-shaped cross section A is the length of the long side of the corresponding rectangular waveguide to be connected 2√ ² −4 ² is the short axis diameter of the cocoon-shaped cross section A flexible waveguide for electromagnetic waves set to 2. In a flexible waveguide that has a spiral or bellows-like wave corrugation in the longitudinal direction on the surface of a metal tube with a thin wall, the inner diameter cross-sectional shape is electrically equivalent and smooth. When considered as a tube, it is a cocoon-like shape that is equivalent to loading ridges symmetrically on the tube walls facing each other along the long axis diameter of an elliptical waveguide, and its cross-sectional shape is expressed in the x-y orthogonal coordinate system. Functional formula (x ² + y ² ) ² + (4b ² −a ² ) (x ² + y ² )=4b ² x ² …(1) where 0.40<k<0.45 (k=b/a) 1.00< 2a/A＜1.08 2a is the long axis diameter of the cocoon-shaped cross section A is the length of the long side of the corresponding rectangular waveguide to be connected 2√ ² −4 ² is set to be expressed by the short axis diameter of the cocoon-shaped cross section In addition, the spiral or bellows-shaped wave corrugation applied to the wall of the waveguide in the length direction is expressed by the function equation in the parameters of the above equation (1). Here, k ₁ and a ₁ are parameters representing the cocoon-shaped cross-sectional shape of the valley part of the corrugation, and k ₂ and a ₂
is also a parameter representing the cocoon-shaped cross-sectional shape of the mountain portion. A flexible waveguide for electromagnetic waves configured in the form shown below.