JPH0142541B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to line conversion of each microwave line in a microwave circuit, and in particular to rectangular waveguides and circular waveguides often used in antennas and microwave receivers for satellite broadcast reception, etc. This invention relates to a rectangular-to-circular waveguide conversion device required for line conversion of a wave tube. Configuration of conventional example and its problems An example of a conventional rectangular-circular waveguide device is shown in FIG. In the figure, a rectangular waveguide 1 is smoothly converted to a circular waveguide 2 by providing a taper from a circular shape to a rectangular shape. However, in this case, there is a drawback that the overall length is extremely long, which is inconvenient when attached to a receiver or the like. FIG. 2 shows another conventional example. In FIG. 2, an elliptical waveguide 4 is inserted between a rectangular waveguide 1 and a circular waveguide 2 to perform rectangular-circular waveguide conversion. Although this method can make the total length shorter than the taper method shown in FIG. 1, it has the disadvantage of narrowing the bandwidth. In FIGS. 1 and 2, 1 is a rectangular waveguide, 2 is a circular waveguide, 3 is a tapered waveguide from a rectangular to circular waveguide, and 4 is an elliptical waveguide. OBJECT OF THE INVENTION The present invention eliminates such drawbacks and provides broadband,
The present invention aims to provide a rectangular and circular waveguide conversion device that has good matching impedance and can have a short overall length. Structure of the Invention The rectangular-circular waveguide conversion device according to the present invention connects an elongated waveguide to a first rectangular waveguide, and connects a second rectangular waveguide to the elongated waveguide. The first rectangular waveguide and the circular waveguide are connected by connecting the first rectangular waveguide and the circular waveguide to the second rectangular waveguide. It is possible to obtain a conversion device that can perform the conversion smoothly. DESCRIPTION OF EMBODIMENTS An embodiment of the present invention is shown in FIGS. 3 and 4. In Figure 3, 1 is a rectangular waveguide, 2 is a circular waveguide,
Reference numerals 5 and 6 denote a long elliptical waveguide and a nearly square rectangular waveguide connected between the rectangular waveguide 1 and the circular waveguide 2. FIG. 4 shows how this connection is made. Figure a shows a connection sectional view of each waveguide, and b and c show input front views seen from the input side of the rectangular waveguide 1 and the input side of the circular waveguide 2. In FIG. 4, the same reference numerals as in FIG. 3 indicate the same parts. That is, in FIG. 4, the conversion from the rectangular waveguide 1 to the circular waveguide 2 is performed in two steps. The two sides are connected to a long elliptical waveguide 5, which is a first conversion waveguide and is surrounded by two circular arcs. By doing so, the rectangular waveguide 1 and the oblong waveguide 5 are smoothly converted by electric field coupling, as shown by the electric field distributions 1 and 5 in FIG. Next, a rectangular waveguide 6 with a nearly square cross section as shown in 6 in FIG. 4 or 5 is connected between the long elliptical waveguide 5 and the circular waveguide 2, and then A circular waveguide 2 is connected to. The rectangular waveguide 6 has a shorter width a ₂ (corresponding to the width of the H plane) and a longer vertical width b ₂ (corresponding to the width of the E plane) than the width a of the regular rectangular waveguide 1. The height is slightly longer than the width (aspect ratio approximately 6:
5) The cross section is nearly square, and each corner of the cross section has a slight curvature. Further, the horizontal width of this rectangular waveguide 6 is approximately equal to the diameter of the circular waveguide 2, and the vertical width is slightly longer than this diameter.
By doing so, the circular waveguide 2 and the rectangular waveguide 6 are smoothly converted by electric field coupling as shown at 2 and 6 in FIG. On the other hand, as is clear from the electric field distributions 5 and 6 in FIG. 5, the rectangular waveguide 6 and the oblong waveguide 5 are smoothly coupled. Generally, a circular waveguide exhibits a higher characteristic impedance than a rectangular waveguide. In other words, the characteristic impedance Z _w of a rectangular waveguide is Z _w =Z ₀ 2b/A・λ _gR /λ... However, λ _gR is the wavelength inside the tube, Z ₀ is the characteristic impedance in free space, a and b are the long and short sides of the rectangular waveguide, and λ is the wavelength in free space. Now, connect the rectangular waveguide to WR75 (a=19.05mm, b=
a/2), the characteristic impedance Z _WR is 509 (Ω) when the input signal frequency is 11.7 GHz and 12.2 GHz.
and 493 (Ω). On the other hand, the characteristic impedance Z _wc and the guide wavelength λ _gc of the circular waveguide are expressed by the following equations. Z _wc =Z ₀ λ _gc /λ... however,

[Formula] r: radius of circular waveguide, x^ (m, m): Betzell function Jm (x^ [m, m]) = root of O, in TE ₁₁ mode, J ₁ (x^ (1 , 1))=0, and
x^(1, 1) = 1841. When the input signal frequency is 11.7GHz and 12.2GHz and the circular waveguide is CR62 (r≈8mm), the characteristic impedance is Z _wc1 = 1249 (Ω) and Z _wc2 , respectively.
The characteristic impedance is approximately 930 (Ω), which is approximately twice that of the rectangular waveguide described above. Therefore,
It is not easy to configure a waveguide conversion between a rectangular waveguide and a circular waveguide so as to smoothly couple the waveguide with a short waveguide length. Therefore, in this device, as shown in FIG. 4 and FIG. A tube 6 is provided, and the width a ₁ of the elongated waveguide 5 is approximately equal to the width a ₀ of the rectangular waveguide 1, and the height b ₁ is higher than the height b ₀ of the rectangular waveguide 1. long elliptical waveguide 5
The characteristic impedance of the rectangular waveguide 6 is increased, and the width a ₂ of the approximately square rectangular waveguide 6 is set to a ₀ of the rectangular waveguide 1.
By making the waveguide narrower and making the height larger than the height _b1 of the elongated waveguide 5, the characteristic impedance becomes larger from the equation, approaching the characteristic impedance of the circular waveguide 2, resulting in smooth waveguide. I'm getting a tube conversion. Further, the length of the rectangular waveguide 6 is made approximately 1.5 times longer than the length of the oblong waveguide 5, thereby making the coupling from the circular waveguide 2 smoother. In Fig. 5, a ₀ = 19.05 mm for rectangular waveguide 1,
b ₀ ≒ 9.5 mm (WR75), radius r of circular waveguide 2
≒8mm (CR62), the long elliptical waveguide 5
b ₁ ≒13mm, arc radius R≒10mm, waveguide length approximately 8mm
(At this time, the wavelength inside the tube is equivalently close to that of a rectangular waveguide with a width of 20 mm and a length of 13 mm, so the waveguide length is 8 mm.
is equivalent to approximately 1/4 wavelength of the pipe wavelength)
In the square rectangular waveguide 6, a ₂ ≒15mm, b ₂ ≒18
mm, and the waveguide length is approximately 12 mm (this equivalently corresponds to approximately 1/4 wavelength of the guide wavelength).
In particular, it is possible to construct a rectangular and circular waveguide converter that is broadband matched in the 12 GHz band (approximately 11.7 to 12.7 GHz). Therefore, as shown in Fig. 4a, a rectangular waveguide (WR75) and a circular waveguide (CR62) are placed at both ends of an integrated long elliptical waveguide 5 and a nearly square rectangular waveguide 6. A simple rectangular-circular waveguide converter can be constructed by attaching flanges to the elongated waveguide 5 and the rectangular waveguide 6, respectively, as shown in FIG. By attaching this, it can be configured as a very small rectangular-circular conversion adapter with a total length of approximately 2 cm. In addition, in FIG. 6, 7 and 8 indicate flanges, and 9 indicates a retainer of the flange. As described in detail above, the present invention is applicable to rectangular waveguides (for example, the ratio of the width of the H plane to the height of the E plane is 2:1).
In a rectangular-circular waveguide conversion device between a circular waveguide and a rectangular waveguide, by interposing an elongated waveguide and a nearly square rectangular waveguide between the two, it is possible to achieve small size, wide band, and consistency. This results in good waveguide conversion. A waveguide conversion device is required to bring the characteristic impedances between two waveguide lines with different characteristic impedances closer together using a conductive tube conversion device, and to combine the transmission electromagnetic field modes in each waveguide without loss. . Therefore, for waveguide conversion,
Sudden impedance transformations or transformations that significantly change the dimensions of the structure impede smooth coupling of transmitted electromagnetic field modes, leading to increased transformation losses and impedance mismatches. In the rectangular to circular waveguide conversion of the present invention, the conversion is performed in two steps. First, in a long elliptical waveguide, in order to approximate the circular waveguide mode, the side surface corresponding to the E plane of the rectangular waveguide is made into an arc so that the electric field in the tube is concentrated at the center of the conductive tube. And, when the long elliptical waveguide is superimposed on the rectangular waveguide, the arc becomes the E of the rectangular waveguide.
By making the plane cross at two points, the arcs and the E plane are almost at the same position, making it easier to couple, and the height b ₁ is set to the height of the rectangular waveguide.
Increase the characteristic impedance by making b slightly larger than ₀ . Next, the width a ₂ of the second rectangular waveguide 6 is made to be approximately equal to the length a ₁ of the two parallel sides of the oblong waveguide, and slightly shorter than the diameter 2r of the circular waveguide 2. Hidden and second rectangular waveguide 6
The height b ₂ of the waveguide is made larger than that of the elongated waveguide b ₁ so as to be closer to that of the square waveguide, thereby smoothing the coupling with the circular waveguide mode.
In addition, since the internal wavelength of the long elliptical waveguide 5 is equivalently approximately equal to the internal wavelength of a rectangular waveguide with a long side of 20 mm, the length is set to approximately 1/4 of the internal wavelength. The length of the second rectangular wave tube is also approximately equal to 1/4 the wavelength within the tube, thereby converting the characteristic impedance of each conductive wave tube. With the above configuration, waveguide conversion between a standard rectangular waveguide and a circular waveguide can be performed smoothly over a wide band with extremely low insertion loss, and since it can be made short, it can be made small and light, so it can be used for actual satellite TV. When attached to a broadcast receiving converter or the like, the converter can be configured compactly and is highly suitable for mass production. In this example, the length of the rectangular-circular waveguide section is 2 cm.
This can be done by adding the thickness of the flange (usually about 4 mm), and the conventional example shown in Fig. 1 requires a length of about 20 cm, making it possible to significantly reduce the size. Effects of the Invention As described above, according to the present invention, conversion between a circular waveguide and a rectangular waveguide can be configured with good matching over a wide band, low loss (0.01 dB or less), and a very short structure. Accordingly, it is possible to provide a rectangular-circular waveguide converter and a converting device that are small and inexpensive.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a conventional tapered rectangular-circular waveguide converter, FIG. 2 is a perspective view of another conventional rectangular-circular waveguide converter via an elliptical waveguide, FIG. 3 shows a rectangle in one embodiment of the present invention.
Perspective view of circular waveguide conversion device, Figure 4 a, b, c
5 is a cross-sectional view, a front view, and a rear view of the same device, FIG. FIG. 2 is a cross-sectional view of a main part of an example of a rectangular-circular waveguide conversion adapter. 1... Rectangular waveguide, 2... Circular waveguide, 5...
Long elliptical waveguide, 6... Rectangular waveguide, 7, 8
...Flange.

Claims (1)

[Claims] 1. An elongated waveguide is connected to a first rectangular waveguide whose H-plane width is larger than the E-plane width, and a second rectangular waveguide is connected to this elongated waveguide. A circular waveguide is connected to the second rectangular waveguide, and the center axes of the respective waveguides are arranged in a straight line, and the long elliptical waveguide has a cross section of two. The parallel long sides of the book are surrounded by two symmetrical arcs, and the two parallel long sides correspond to the H plane of the first rectangular waveguide, and the distance between them corresponds to the first rectangular waveguide. The symmetrical arc is made larger than the width of the E-plane of the waveguide, and when superimposed on the first rectangular waveguide, this arc crosses the E-plane of the first rectangular waveguide at two points. The width of the second rectangular waveguide corresponding to the H-plane of the first rectangular waveguide is the length of two parallel sides of the elongated ellipsoidal waveguide and the length of the circular waveguide. The vertical width corresponding to the E plane is larger than the distance between the parallel long sides of the elongated ellipsoidal waveguide, larger than the lateral width, and substantially equal to the lateral width;
A rectangular-to-circular waveguide conversion device, characterized in that the length of the elongated ellipsoidal waveguide and the second rectangular waveguide is approximately 1/4 of the equivalent internal wavelength of each waveguide. . 2. The rectangular-to-circular waveguide conversion device according to claim 1, wherein each corner of the inner wall of the second rectangular waveguide has a constant curvature. 3. A rectangular monocircular waveguide according to claim 1 or 2, characterized in that the two arcs of the elongated ellipsoidal waveguide are located concentrically with the circle of the circular waveguide. Pipe converter.