JPH0323683Y2 - - Google Patents

Description

[Detailed description of the invention] (Technical field) This invention is used to connect an oversized transmission waveguide and a fundamental mode transmission waveguide for transmitting electromagnetic waves in the microwave band or millimeter wave band. The present invention relates to a waveguide connection device.

(Prior Art) In order to reduce loss in the transmission of electromagnetic waves in the microwave band or millimeter wave band, oversized transmission waveguides are often used. In a waveguide connecting device that connects this oversized transmission waveguide and a fundamental mode transmission waveguide, it is necessary to suppress the generation of unnecessary electromagnetic field modes and impedance mismatch as much as possible. Therefore, in this conventional connection device, a tapered waveguide whose diameter is slightly changed from the same diameter as the oversized transmission waveguide is used to suppress the generation of unnecessary electromagnetic fields and impedance mismatch.

However, in this waveguide connection device, the tapered waveguide becomes long, which becomes an obstacle to downsizing the connection device.
Another drawback was that manufacturing the tapered waveguide was very difficult.

In addition, in order to reduce the size, as shown in the cross-sectional view in FIG. In equipment, losses are large due to impedance mismatch and generation of unnecessary electromagnetic field modes.
Furthermore, it had the disadvantage of poor frequency characteristics due to multimode reflection.

To explain this in more detail, the oversized transmission waveguide 1 shown in FIG.
(published on the 25th, Maruzen, pp. 38-42), from the circular TE ₁₁ mode, which is the basic transmission mode, to the higher-order TM mode in which the electric field also exists in the tube axis direction, and the electric field in the tube axis direction. Both high-order TE modes that do not exist can be excited from the tapered waveguide 2.
Therefore, there is a high possibility that higher-order modes with large transmission losses will be excited, and when the oversized transmission waveguide 1 and the tapered waveguide 2 are connected to both ends of the oversized transmission waveguide 1,
Coupled with the resonance phenomenon caused by the connection, the circular
In TE ₁₁ mode transmission, the transmission loss may be much larger than expected.

As an example, oversize waveguide 1 (diameter φ70
Tapered waveguide 2 (diameter φ70) at both ends of mm length 4m)
Fig. 2 shows the loss characteristics when electromagnetic waves are transmitted from the fundamental mode waveguides 3 (diameter 1.7 mm) at both ends of the waveguides (tapered from mm to 1.7 mm, length 90 mm). As you can see from this Figure 2, the first
The method shown in the figure has a lot of loss (approximately 15dB to 20dB),
The drawback was that it caused ripples in the frequency characteristics.

(Purpose of the invention) An object of the invention is to provide a waveguide connecting device with low transmission loss, good frequency characteristics, and short length.

(Structure of the invention) The waveguide connecting device of the present invention connects a circular oversized transmission waveguide and a fundamental mode transmission waveguide with a circular tapered waveguide. A size transmission waveguide and the tapered waveguide are electromagnetically connected, and the diameter of the tapered waveguide on the side facing the oversized transmission waveguide is smaller than the diameter of the oversized transmission waveguide. Moreover, it is larger than 1/5 of its diameter.

(Example) Next, the present invention will be explained in detail with reference to Examples.

FIG. 3 is a sectional view showing an embodiment of the present invention. In this embodiment, the tapered waveguide 4 has an aperture φ ₂ smaller than the aperture φ 1 of the oversized transmission waveguide 1 at one end of the oversized transmission waveguide ₁ to an aperture φ of the fundamental mode transmission waveguide 3 . Convert to ₃ .

In this embodiment, for example, a tapered waveguide 4 (tapered length 90 mm from diameter φ ₂ 20 mm to φ ₃ 1.7 mm) is installed at both ends of an oversized transmission waveguide 1 (diameter φ ₁ 70 mm, length 4 m). , by aligning the aperture surfaces and centers of both to separate them mechanically but connect them electromagnetically,
Fundamental mode transmission waveguide 3 at one end (diameter φ ₃ 1.7
When electromagnetic waves were transmitted from 1.5 mm), the loss characteristics (loss approximately 7 to 8 dB) shown in the characteristic diagram in Figure 4 were obtained.
Therefore, when comparing the loss characteristics of the conventional waveguide connection device shown in Fig. 1 (Fig. 2) and the loss characteristics of this embodiment (Fig. 4), the transmission loss of this embodiment is much higher. It can be seen that the frequency characteristics are low and the frequency characteristics are good (small ripple).

The reason why the transmission loss according to this embodiment shown in FIG. 4 is smaller than the transmission loss according to the conventional example shown in FIG. 2 will be considered. The conductors between the oversized transmission waveguide 1 and the tapered waveguide 4 according to this embodiment are mechanically separated. Therefore, as is well known, from the tapered waveguide 4 to the oversized transmission waveguide 1, at least a higher-order mode in which the wall current flows in the tube axis direction, such as TM
modes are difficult to excite. Then, the resonance phenomenon caused by multimode reflection is reduced. In this embodiment, a tapered waveguide 4 and an oversized transmission waveguide 1 are used.
In the 136 GHz band, both are oversized waveguides, so their characteristic impedances are almost the same as in free space. As a result, even if the apertures of the two are slightly different, there is little electrical discontinuity, and the excitation from the tapered waveguide 4 to the oversized transmission waveguide 1, or the excitation in the opposite direction, is circular, which is the fundamental mode. It is thought that TE ₁₁ mode will be the main mode. However, if the diameter of the tapered waveguide 4 is too smaller than the diameter of the oversized transmission waveguide 1, there is a possibility that sufficient energy (power) may not be transferred between the two. Here, the power distribution of the aperture surface of the oversized transmission waveguide 1 in the circular TE ₁₁ mode can be calculated using equation (1.194) on pages 40 and 41 of the document. Figure 5 shows a circular waveguide in circular TE ₁₁ mode transmission (here, oversized transmission waveguide 1).
The calculation results of the power distribution on the aperture surface are shown. When the ratio of the aperture to the diameter of a circular waveguide (aperture ratio) is 0.29, the amount of power occupied by the aperture is approximately 0.21 (-
6.8dB). Also, the amount of electricity is 1/10
The aperture ratio of (10 dB) is about 1/5. Fourth
In the experimental example shown in the figure (transmission loss 7 to 8 dB),
The transmission loss of the oversized transmission waveguide 1 is estimated to be 1 dB or less, and the coupling loss from the tapered waveguide 4 located on the left side of the figure to the oversized transmission waveguide 1 is estimated to be negligible. Coupling loss from size transmission waveguide 1 to tapered waveguide 4 is 7dB
It is estimated that the Therefore, the results calculated from the aperture power distribution of circular TE ₁₁ mode transmission and the experimental values are in good agreement. Although not quantitative,
In circular TE ₁₁ mode transmission, energy (power)
The literature shows that
Also shown on page 410, Figure 14.27.

As described above, in this embodiment, at one end of the oversized transmission waveguide 1, the diameter φ ₂ is smaller than the diameter φ ₁ of the oversized transmission waveguide 1, and the diameter φ ₃ of the fundamental mode transmission waveguide 3 is changed. It is a small device having a structure consisting of a tapered waveguide 4 for conversion, and can connect the oversized transmission waveguide 1 and the fundamental mode transmission waveguide 3 with low loss and good frequency characteristics.

(Effects of the Invention) As described in detail above, according to the present invention, it is possible to provide a waveguide connecting device with relatively little transmission loss and good frequency characteristics even when the length is short.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view conceptually showing a conventional waveguide connection device, and FIG. 2 is a diagram showing the characteristics of this conventional device.
FIG. 3 is a cross-sectional view conceptually showing an embodiment of the present invention, FIG. 4 is a diagram showing the characteristics of this embodiment, and FIG. 5 is a diagram showing the power distribution on the aperture surface of a circular waveguide. . 1... Oversized transmission waveguide, 2, 4... Tapered waveguide, 3... Fundamental mode transmission waveguide.

Claims (1)

[Scope of utility model registration request] In a waveguide connection device that connects a circular oversized transmission waveguide and a fundamental mode transmission waveguide with a circular tapered waveguide, the oversized transmission waveguide and the tapered waveguide are electromagnetically connected. and the diameter of the tapered waveguide on the side facing the oversized transmission waveguide is smaller than the diameter of the oversized transmission waveguide and larger than 1/5 of that diameter. Waveguide connection device.