JPS6272202A - Microwave terminating set - Google Patents

Abstract

PURPOSE:To eliminate the reflection due to discontinuous impedance by providing a step having a height corresponding substantially to the thickness of a tip of a microwave absorbing body to a waveguide wall where the tip of the microwave absorbing body is placed so as to make the front ridge of a tape face of wedge form of the microwave absorbing body continuous smoothly with the waveguide wall. CONSTITUTION:A slot 8 having a length corresponding to the length of a microwave absorbing body 7 and having a depth corresponding to the thickness of the tip of the microwave absorbing body 7 is formed to a wall 1A of a waveguide 1 where a bottom of the microwave absorbing body 7 is placed. Then the bottom of the microwave absorbing body 7s is stored in the slot 7 and fixed by soldering or an adhesives. Thus, the step difference due to the thickness of the tip of the microwave absorbing body 7 is eliminated by the step 9 of the slot 8 of the waveguide 1 and the change in the characteristic impedance at the tip of the wedge shape microwave absorbing body is very small. Thus, the microwave is not reflected at the tip of the wedge shape microwave absorbing body. Further, a residual step S and a gap G being allowable to the step 0 are decided relatively by the operating wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a microwave terminator. It concerns a microwave terminator in which a wedge-shaped microwave absorber is placed within a rectangular waveguide, such that the wedge-shaped microwave absorber is located within a rectangular waveguide.

BACKGROUND OF THE INVENTION At present, various types of waveguide type microwave terminators are used for terminating waveguide circuits that are microwave transmitters,
It is used in various parts, such as as a microwave termination part used for circuit division in coupled cavity traveling wave tubes.

Such waveguide-type microwave terminators include those in which a so-called choke structure short-circuit plate with a closed circuit for two operating wavelengths is placed inside the waveguide, and one in which the tip is placed on the central axis of the waveguide. Types in which a microwave absorbing material plate with a triangular tip is placed inside the waveguide, and types in which a plate-shaped or block-shaped microwave absorber with one end wedge-shaped is placed inside the waveguide. There are various types, such as those in which a microwave absorbing material is pasted on the inner surface of the waveguide. Among these, one in which a wedge-shaped microwave absorber is arranged within a waveguide is relatively widely used because it has a simple structure and is easy to manufacture.

FIGS. 2(a) and 2(b) are schematic perspective views of such a type of microwave terminator. The microwave terminator shown in FIG. 2(a) is constructed by arranging a wedge-shaped plate-shaped microwave absorber 2 along the center line of a rectangular waveguide 1 and parallel to the electric surface. , the microwave V! shown in FIG. 2(b). The terminal device is the plate-shaped microwave absorber 2 shown in Fig. 2(a).
As if the thickness of was expanded to the width of a rectangular waveguide,
A wedge-shaped block microwave absorber 3 is arranged inside a rectangular waveguide 1.

The taper of the wedge portion of these plate-shaped microwave absorbers 2 and block-shaped microwave absorbers 3 is for matching with the characteristic impedance of the waveguide, and prevents impedance from becoming discontinuous. It is something that In such a state, the microwave is absorbed by the plate-like microwave absorber 2 and the block-like microwave absorber 3, and a reflection-free termination is realized.

Problems to be Solved by the Invention If we examine in detail a microwave terminator in which a wedge-shaped microwave absorber is arranged as described above, a rectangular waveguide 1 as shown in the longitudinal cross-sectional view of FIG. The open end of the
A flange 4 is provided for connection with other waveguides. Furthermore, a wedge-shaped microwave absorber 5 is arranged within the rectangular waveguide 1, reaching at least the height of the rectangular waveguide when reaching its closed end. Note that the arrow indicated by reference number 6 indicates the direction of incidence of the microwave.

In the above-mentioned microwave terminator, the biggest problem is how to absorb the incident microwave without reflecting it. In other words, the microwave terminator is
The characteristics are determined based on the magnitude of the reflection coefficient. Therefore, in conventional microwave terminators, in order to reduce this reflection coefficient, the presence of a microwave absorber slows down the change in characteristic impedance in the waveguide in the direction of microwave propagation. As mentioned above, the microwave absorber has a tapered wedge shape.

However, in order to maintain the strength of a microwave absorber made of ceramic or the like, the wedge-shaped tip cannot be made very thin. Therefore, conventionally, it has been helpful to form a wedge shape with a thickness of about 0.5 mm or more left at the tip. However, only 0.
Even with a thickness of about 5 mm, the characteristic impedance changes rapidly at the tip of the microwave absorber. In particular, as the frequency becomes higher, such as in the millimeter wave region, the size of the waveguide itself becomes smaller, so changes in its characteristic impedance cannot be ignored, and the reflection of microwaves at the tip of the microwave absorber becomes smaller. This becomes a problem. Therefore, the higher the frequency, the more difficult it is to create a microwave termination with a sufficiently small reflection coefficient.

Therefore, the present invention aims to provide a microwave terminator that eliminates the problem of reflection at the tip of the wedge-shaped microwave absorber as described above.

According to the present invention, a wedge-shaped microwave absorber is placed inside a rectangular waveguide such that the tip of the wedge-shaped microwave absorber is located on the inner wall surface of the rectangular waveguide. In the arranged microwave terminator, the waveguide wall on which the tip of the micro-absorber is located has a step having a height substantially equal to the thickness of the tip of the microwave absorber. It is provided in front of the microwave absorber when viewed from the direction of microwave incidence, so that the waveguide wall continues smoothly from the top of the liquid film to the incidence side of the waveguide.

Effect When the microwave terminator is configured as described above, the step provided on the waveguide wall where the tip of the micro absorber is located substantially eliminates the step difference due to the thickness of the tip of the microwave absorber. be able to. Therefore, the leading edge of the tapered surface of the wedge-shaped portion of the microwave absorber and the waveguide wall are smoothly continuous, and as a result, it is possible to avoid sudden changes in impedance at the tip of the microwave absorber. can. Therefore, the impedance change from the waveguide to the microwave absorber can be smoothed, and reflections due to impedance discontinuity can be eliminated. Thus, with the microwave terminator having the above configuration, it is possible to realize a nearly perfect non-reflection terminator.

Embodiments Hereinafter, embodiments of the microwave terminator according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention. Note that parts corresponding to those of the conventional example shown in FIG. 3 are given the same reference numerals.

The microwave terminator shown in FIG. 1 has a rectangular waveguide 1 constituting its outer periphery, and a flange 4 is provided at the open end of the waveguide for connection to other three-dimensional circuit elements. A microwave absorber 7 that absorbs microwaves incident in the direction of arrow 6 is disposed within the waveguide 1. When viewed in the longitudinal section of the waveguide 1, the microwave absorber 7 has a roughly right triangular shape, the front end of which does not form an acute angle, and has a thickness of, for example, about 0.5n+m, as described above. have. The rear end of the microwave absorber 7 has a height that approximately corresponds to the height of the waveguide 1.

The microwave absorber 7 is manufactured by coating the surface of a ceramic containing SiC or a ceramic such as alumina with carbon-dispersed water that can be manually applied under the trade name "Aqua Darag" in the same way as a conventional microwave terminator.・Can be made from baked goods.

On the other hand, the wall IA of the waveguide where the bottom of the microwave absorber 7 is located has a length corresponding to the length of the microwave absorber 7 and a thickness equal to the thickness of the tip of the microwave absorber 7. A groove 8 is formed with a corresponding depth. The bottom portion of the microwave absorber 7 is accommodated in the groove 8 and fixed by brazing or adhesive.

In this way, the step 9 formed by the groove 8 of the waveguide 1 eliminates the step difference due to the thickness of the tip of the microwave absorber 7, and the change in characteristic impedance at the tip of the wedge-shaped microwave absorber becomes extremely small. Therefore, microwaves are not reflected at the tip of the wedge-shaped microwave absorber.

In this way, the incident microwave is gradually absorbed by the tapered portion of the wedge-shaped microwave absorber 7 with almost no reflected waves. Therefore, according to this embodiment,
It is possible to create a microwave terminator with an extremely small reflection coefficient.

Note that when the microwave absorber 7 is plate-shaped, that is, fin-shaped, as shown in FIG. 2(a), a groove 8 with a width corresponding to the thickness of the plate may be formed in the waveguide wall. Furthermore, when the microwave absorber 7 is block-shaped as in FIG. 2), the groove 8 may be formed in the waveguide wall so as to extend over the entire width of the bottom wall of the waveguide.

Next, the height of step 9 will be described. Operating wavelength 14GH
In the case of the microwave terminator z, as shown in FIG. 1A, the microwave absorber 7 as seen from the direction of microwave incidence
It is preferable that the step 9 has a height such that the step difference S between the tip edge of the tapered surface and the inner surface of the waveguide, that is, the residual step S, is ±0.1 mm or less. In addition, the minus sign of ±0.1 mm is at step 9.
This means that the tapered tip edge of the microwave absorber 7 is lower than the surface of the waveguide wall. Also,
In the case of a microwave terminator with an operating wavelength of 7 GHz, the height of the step 9 is preferably such that the residual step S seen from the direction of microwave incidence is ±0.2 mm or less. The above relationship between the operating wavelength and the residual step S is similar to the micro 2I!
It is also applicable to terminators as well.

The gap G between the tip surface of the microwave absorber 7 and the step 9 on the inner wall of the waveguide shown in FIG.
0.2-0.3n++n for z microwave terminator
It is preferable to do the following. Therefore, the gap G has a somewhat larger allowable range than the residual step S.

In any case, the allowable residual step S and gap G are:
It is determined by the operating wavelength.

In addition, in the above embodiment, the longitudinal cross-sectional shape of the waveguide 1 of the microwave absorber 7 is approximately a right triangle;
As shown in FIG. 2, the longitudinal section of the waveguide may be trapezoidal.

As described in detail of the invention, in the microwave terminator having the structure of the present invention, there is almost no reflection of microwaves by the tip of the wedge-shaped microwave absorber, so the reflection coefficient can be made extremely small. .

In addition, the thickness of the tip of the wedge-shaped microwave absorber is
Even if the waveguide has a large step, it is possible to prevent the microwave from being reflected, thereby increasing the strength of the microwave absorber.

For example, even in a terminator that is used with high power and undergoes a large temperature cycle, the thickness of the tip can be increased to provide sufficient strength, thereby making the microwave absorber difficult to break. Therefore, it is possible to prevent deterioration of characteristics due to cracking of the microwave absorber.

As described above, the microwave terminator according to the present invention can exhibit significant practical effects.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a microwave terminator according to the present invention; FIG. 1A is an enlarged view of the tip of a wedge-shaped microwave absorber of the microwave terminator shown in FIG. 1; Figures 2(a) and 2) are schematic perspective views showing an example of a conventional microwave terminator using a wedge-shaped microwave absorber, and Figure 3 is a schematic perspective view showing an example of a conventional microwave terminator using a wedge-shaped microwave absorber. FIG. 2 is a vertical cross-sectional view of an example of a microwave terminator. [Main reference numbers] 1. Rectangular waveguide 2. Plate microwave absorber 3. Block microwave absorber 4. Flange 5.7. Wedge-shaped microwave absorber 8. Guide Groove 9 in the waveguide wall...Step S in the waveguide wall...Residual step G between the tip edge of the tapered surface of the microwave absorber and the inner surface of the waveguide...The tip of the microwave absorber and the inner wall of the waveguide gap between the steps of

Claims (1)

[Claims] (1) In a microwave terminator in which a wedge-shaped microwave absorber is arranged within a rectangular waveguide such that the tip of the wedge-shaped microwave absorber is located on the inner wall surface of the rectangular waveguide,
On the waveguide wall where the tip of the micro absorber is located, there is a step with a height substantially corresponding to the thickness of the tip of the microwave absorber, which absorbs the microwave when viewed from the direction of microwave incidence. 1. A microwave terminator, characterized in that the waveguide wall is smoothly continuous from the top of the stage to the input side of the waveguide.