JPS583402B2 - variable attenuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable attenuator that can continuously or stepwise change the amount of attenuation of electromagnetic wave power passing through a waveguide or coaxial transmission line, and is particularly compact. The present invention relates to a variable attenuator that has a large power capacity and a wide frequency adaptation range.

An example of the structure of a conventional waveguide type variable resistance attenuator is shown in FIGS. 1a and 1b.

In the figure, a is an example of a vane type variable resistance attenuator, and b is an example of a flap type variable resistance attenuator, 1 is a metal waveguide portion, and 2 is an example of a metal waveguide portion, which is arranged inside the waveguide in consideration of maximum attenuation and electrical matching. The electromagnetic wave resistor 3 is an adjustment shaft that functions to change the position of the electromagnetic wave resistor in the waveguide.

Both of these variable resistance attenuators are located at the position of the electromagnetic wave resistor 2 (
The amount of coupling between the resistor and the electromagnetic waves can be changed by changing the vane shape) or the insertion depth (flap shape), and thereby the amount of attenuation can be adjusted arbitrarily within a certain range.

In addition, although not shown, the square TE mode can be changed to the circular T mode.
There is also a rotary variable attenuator that converts the mode to E and installs a very thin resistive film in the circular waveguide section, tilting the resistive film to absorb the electric field component parallel to the resistive film and pass only the vertical component. It is used a lot.

However, in both cases, a resistor that serves as an electromagnetic wave absorber is structurally present in the space inside the waveguide, so the heat generated in the resistor when absorbing passing electromagnetic waves is processed (heat dissipation).
There is a problem with the input power being limited.

Further, depending on the shape and structure of the resistor in the waveguide, for example, if the resistive film is made thick, the electrical matching with the electromagnetic waves passing through it is likely to be disturbed, making it difficult to improve the VSWR characteristics.

Particularly in ultra-high frequency band waveguides, the internal space is very small (for example, in the 60 GHz band or higher, the waveguide diameter is 3 × 1.5 mm or less), and the internal space is It is difficult to insert and move a resistor in the

Furthermore, rotary variable resistance attenuators and the like have drawbacks such as extremely precise and complicated structures and frequent failures during use.

In order to solve these drawbacks, the present invention has modified the conventional structure and installed electromagnetic wave absorbers of appropriate shape, size, and number so that the amount of attenuation of electromagnetic waves passing through the pipe increases gradually in the axial direction. A movable metal plate is closely attached to the outside of a waveguide provided with a coupling window of an appropriate size, and by moving the movable plate, the amount of coupling from a fixed size coupling window to an electromagnetic wave absorber is changed. The present invention provides a variable attenuator that attenuates transmitted electromagnetic waves.

The present invention will be described in detail below with reference to the drawings.

FIG. 2 is a perspective view of one embodiment of the waveguide type variable attenuator according to the present invention, FIG. 3 is a sectional view taken along the A-N plane of FIG. 2, and FIG. FIG.

1 is a waveguide section, and as shown in Figure 6, a part of the waveguide section is equipped with an electromagnetic wave absorber, which is determined based on the amount (length) versus attenuation characteristics and the range of required attenuation required for the variable attenuator. area (length l
) is provided with a coupling window 5.

Reference numeral 4 denotes a movable metal plate closely attached to the waveguide section 1 so as to cover the coupling window 5, and the side facing the coupling window 5 has a movable metal plate in consideration of minimum and maximum attenuation as a variable attenuator. Electromagnetic wave absorbers 2 are embedded at appropriate lengths, thicknesses, and intervals.

6 is a heat dissipation plate that is made integrally with the movable metal plate 4 and efficiently radiates heat generated in the electromagnetic wave absorber 2 to the external space when high power is input; 7 is a movable metal plate attached above and below the waveguide 1; This is a connecting member for integrally connecting the plates 4.

With the above configuration, the electromagnetic wave entering from one side of the waveguide 1 propagates inside the tube, and the electromagnetic wave absorber 2 at the coupling window 5
Attenuation determined by the shape (thickness, length, width) of the

Generally, the relationship between the thickness of a plate-shaped electromagnetic wave absorber (having constant length and width) provided on the inner wall between the waveguides and the amount of attenuation is as shown in FIG.

Furthermore, the amount of attenuation increases monotonically with respect to the length of the electromagnetic wave absorber.

Based on these relationships, by making the shape of the electromagnetic wave absorber 2 that covers the coupling window 5 as shown in Figure 5 a = d, the electromagnetic wave from the input port is attenuated so that the amount of attenuation gradually increases as it passes through the pipe. This makes it possible for each absorber to absorb the electromagnetic waves equally.

Here, FIGS. 5a to 5d are illustrations of various embodiments of embedding the absorber 2 in the movable metal plate 4 that is integrally constructed with the radiation fins.

Further, in the above explanation, the shape of the coupling window 5 is a square as shown in FIG. 6, but the shape of the electromagnetic wave absorber 2 is a square, and the shape of the coupling window 5 is as shown in FIGS.
It is clear that similar effects can be obtained even if the electromagnetic wave absorber has the shape shown in FIG.

The shape of the electromagnetic wave absorber 2 or the coupling window 5 described above is determined by the temperature limit and frequency characteristics of the electromagnetic wave absorber.

In the embodiment of the present invention described above, the electromagnetic wave absorber in the coupling window 5 provided in the tube wall of the waveguide section 1 is moved by moving the metal movable plate 4 attached closely to the waveguide section 1. The amount of coupling of electromagnetic waves to 2 can be adjusted, and an arbitrary amount of attenuation can be given to the passing electromagnetic waves.

The heat generated when the electromagnetic wave absorber 2 attenuates the passing electromagnetic waves is efficiently radiated into space by the heat sink 6 provided integrally with the metal movable plate 4 housing the electromagnetic wave absorber 2.

In this way, the variable attenuator of the present invention has a structure in which a movable electromagnetic wave absorber is attached from the outside of the waveguide to the inner wall surface of the waveguide, without placing a resistor inside the waveguide. It does not disturb electromagnetic waves, has good electrical matching characteristics, and has the advantage of being applicable to small-diameter waveguides in ultra-high frequency bands, which were impossible to manufacture with conventional methods.

In addition, since the electromagnetic wave absorber part is structurally located on the surface of the movable metal plate outside the waveguide, it is easy to attach and detach. Because it is attached to one body and an electromagnetic wave absorber of any shape can be attached, it has excellent power resistance characteristics and can effectively operate even against high-power input electromagnetic waves that were previously unusable.

Furthermore, based on the relationship between the shape of the electromagnetic wave absorber and its attenuation characteristics, movable plates with various attenuation amounts are prepared in advance, and the optimum one can be selected as needed. You can also select and install one with damping characteristics.

Possible options include embedding the electromagnetic wave absorber only in the movable metal plate that covers the coupling window on one side of the waveguide wall, or installing electromagnetic wave absorbers on both sides and moving only the movable metal plate on one side.

FIG. 7 shows another embodiment of the present invention, in which an electromagnetic wave absorber 2 with a uniform surface shape and thickness in the tube axis direction is embedded in a movable metal plate 4, and as described above, the coupling window 2 of the waveguide is By forming the shape as shown in FIG. acd, a continuously variable amount of attenuation can be obtained as the movable metal plate 4 moves.

The above is an explanation of the configuration, operation, and effect when a waveguide is used, but the configuration, operation, and effect when using a coaxial line are completely the same as in the case of the waveguide type.

As explained above, the variable attenuator of the present invention has a movable metal plate embedded with an electromagnetic wave absorber of an appropriate size and shape closely attached to the outside of a waveguide provided with a coupling window of an appropriate shape. Because it is an attached structure, electrical matching is good and it can be applied to small-diameter waveguides for ultra-high frequency bands, and the electromagnetic wave absorber, movable metal plate, and integrated heat sink are directly connected. Because of this structure, the power resistance characteristics are significantly improved.

In addition, since the electromagnetic wave absorber is not placed in the internal space of the waveguide, its shape, area, etc. can be freely designed without compromising the matching of electromagnetic waves, and adjustment is easy, making it possible to create a movable plate with arbitrary attenuation characteristics. The design is easy by preparing a waveguide, making the movement of the movable plate installed in the waveguide independent, and attaching an electromagnetic wave absorber to only one movable plate.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a conventional variable resistance attenuator, FIG. 2 is a perspective view of an embodiment of the variable attenuator of the present invention, and FIG. 3 is a line AA and A'-A' in FIG. 4 is a diagram showing the amount (area) versus attenuation characteristic of the electromagnetic wave absorber, FIG. 5 is a diagram showing various structural examples of the electromagnetic wave absorber section of the present invention, and FIG. FIG. 1 is a perspective view of only the waveguide portion, and a sectional view of another embodiment of the present invention. 1... waveguide section, 2... electromagnetic wave absorber, 4... movable metal plate, 5... coupling window,
6... Heat sink.

Claims (1)

[Scope of Claims] 1. A coupling window provided on the wall of a waveguide or the outer conductor of a coaxial line, and a movable metal that is attached in close contact with the coupling window so as to cover the coupling window and that is movable relative to the coupling window. Electromagnetic waves passing through the tube are embedded in the plate and the surface of the movable metal plate on the coupling window side, with electromagnetic absorbers of appropriate shape, size, and number so that the amount of attenuation of the electromagnetic waves passing through the tube increases gradually in the tube axis direction. 1. A variable attenuator, comprising: an electromagnetic wave absorber in which the electromagnetic wave is absorbed equally by each absorber. 2. A coupling window provided in the tube wall of a waveguide or an outer conductor of a coaxial line, a movable metal plate that is attached in close contact with the coupling window so as to cover the coupling window and is movable relative to the coupling window, and the movable metal plate. An electromagnetic wave absorber having a uniform shape in the direction of the tube axis is embedded in the surface of the plate on the side of the coupling window, and the coupling window has a suitable shape so that the amount of attenuation of the electromagnetic waves passing therethrough gradually increases in the direction of the tube axis. A variable attenuator characterized by having a configuration with a shape, size, and number of pieces.