JPH10284911A - Coaxial waveguide converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coaxial waveguide converter in which an undesired reflecting component being a problem is minimized in the case of measuring a distance up to a reflecting face such as sand and earth. SOLUTION: One end of a matching stub 11 is connected to an inner wall of a waveguide 1 in an opposite direction from a waveguide short-circuit device 2 when viewing an exciting conductor 3, and the stub 11 is placed so that a component of an electromagnetic wave from the exciting conductor 3 in an opposite direction to a waveguide short-circuit device 2 that is reflected in the coaxial waveguide converter and restores in a direction of the exciting conductor 3 opposite to the waveguide short-circuit device 2 and a component of an electromagnetic wave from the exciting conductor 3 in an opposite direction to the waveguide short-circuit device 2 that is reflected in the matching stub 11 returns again in a direction of the exciting conductor 3 opposite to the waveguide short-circuit device 2 are cancelled together.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a coaxial waveguide converter used in a band, a UHF band, and a microwave band, and particularly to a coaxial waveguide converter having a structure in which an object such as earth and sand or a liquid passes through the inside of the waveguide.

[0002]

2. Description of the Related Art In a coaxial waveguide converter, one end of a waveguide is usually closed by a short-circuit plate, and an object such as earth and sand or a liquid cannot pass through the waveguide. However, it is possible to pass an object by devising the shapes of the short circuiter and the probe. For example, in the paper No. C108 “Coaxial line-to-waveguide converter using a folded probe and a Y-type short-circuiter” of the IEICE Autumn National Convention in September 1994, the short-circuiter is not a conventional plate but a Y-shaped. In this structure, the probe is bent at about one-quarter wavelength of the electromagnetic wave propagating through the waveguide, and the tip is connected to the wall surface of the waveguide, thereby enabling the inflow of an object.

FIG. 5 is a block diagram of a conventional coaxial waveguide converter capable of passing earth and sand and liquid.
FIG. 5A is a cross-sectional view as viewed from the center axis of the waveguide, and FIG.
FIG. 5C is a cross-sectional view as viewed from the side, and FIG. 5C is a diagram illustrating a matching portion between the coaxial line and the waveguide converter. In the figure,
1 is a circular waveguide, 2 is a Y-shaped waveguide short circuit, 3 is a folded excitation conductor, 4 is a dielectric substrate, 5 is a strip conductor, 6 is a ground conductor, 7 is a dielectric substrate 4, A microstrip line composed of a strip conductor 5 and a ground conductor 6;
Is a quarter wavelength microstrip line transformer for impedance matching, 9 is a transformer cover, and 10 is a coaxial connector.

Next, the operation of the conventional coaxial waveguide converter will be described. In FIG. 5, when an electromagnetic wave is incident from the coaxial connector 10, the electromagnetic wave propagates to the excitation conductor 3 via the microstrip line 7, and the electromagnetic wave is converted from the coaxial mode to the waveguide mode in the waveguide 1. The electromagnetic wave converted into the waveguide mode propagates from the excitation conductor 3 in both directions of the axis of the waveguide 1, but the electromagnetic wave propagated to the waveguide short circuit 2 is reflected by the waveguide short circuit 2, Waveguide short circuit 2
It is superimposed on the electromagnetic wave propagating in the direction opposite to the side, and eventually propagates only in one direction of the waveguide 1.

Here, even if the reactance of the coaxial waveguide converter can be reduced to zero by adjusting the distance between the excitation conductor 3 and the waveguide short-circuit device 2, the resistance is connected. It may not match the characteristic impedance of the coaxial line. In this case, the resistance of the coaxial waveguide converter is represented by R,
Assuming that the characteristic impedance of the coaxial line is Z, a quarter
The characteristic impedance of the wavelength microstrip line transformer 8 may be set to (R · Z) ^1/2 .

[0006]

As described above, the conventional coaxial waveguide converter has a matching quarter-wavelength microstrip line transformer between the input coaxial connector and the excitation conductor. Therefore, the matching is obtained when viewed from the coaxial connector side, but the matching is not obtained when viewed from the waveguide side. Therefore, the reflection on the reflection surface to be measured in the waveguide and the reflection viewed from the waveguide side of the coaxial waveguide converter cause multiple reflections, and unnecessary reflection components cause measurement errors.

FIG. 6 shows a system for measuring the distance to earth and sand in a waveguide, wherein 14 is a coaxial waveguide converter,
Reference numeral 15 denotes earth and sand, 16 denotes a network analyzer, and 17 denotes a coaxial cable. An electromagnetic wave is emitted from the network analyzer 16 to excite the coaxial waveguide converter 14 via the coaxial cable 17 to propagate the electromagnetic wave into the waveguide. The electromagnetic wave propagates in the waveguide, is reflected on the surface of the earth and sand 15, returns to the coaxial waveguide converter 14, returns the reflected wave to the network analyzer 16, and is measured by the network analyzer 16. The network analyzer 16 has a time-domain function, and can resolve the state of reflection on the time axis. This is shown in FIG. Since the time axis is considered to be equivalent to the distance axis, the reflection at the coaxial waveguide converter 14 and the reflection at the earth and sand 15 can be separated. Further, by using the gate function of the network analyzer, it is possible to extract the reflection component of only a necessary portion. Here, the reflection of the coaxial waveguide converter 14 can be separated because the position is invariable, but the position of the reflection component of the soil 15 fluctuates because the surface of the earth 15 moves. Also, the multiple reflection between the earth and sand 15 and the coaxial waveguide converter 14 fluctuates similarly. Therefore, there is a problem that unnecessary multiple reflection components cannot be deleted.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to minimize unnecessary reflection components which are problematic when measuring the distance to a reflection surface such as earth and sand. I do.

[0009]

According to a first aspect of the present invention, there is provided a coaxial waveguide converter in which one end of a matching stub is connected to an inner wall of a waveguide in a direction opposite to a waveguide short circuit when viewed from an excitation conductor. There is a component that the electromagnetic wave from the direction opposite to the waveguide short circuit of the excitation conductor is reflected by the coaxial waveguide converter and returns again in the opposite direction to the waveguide short circuit of the excitation conductor and the waveguide short circuit of the excitation conductor. The spacing is such that the electromagnetic wave from the opposite direction to the waveguide is reflected by the matching stub and the component of the waveguide conductor of the excitation conductor and the component returning in the opposite direction cancel each other.

In the coaxial waveguide converter according to the second aspect of the present invention, a threaded hole is formed in a waveguide wall in a direction opposite to the waveguide short-circuiter as viewed from the excitation conductor, and a threaded hole is formed from outside the waveguide. The electromagnetic wave from the direction opposite to the waveguide short circuit of the excitation conductor is reflected by the coaxial waveguide converter and returns to the direction opposite to the waveguide short circuit of the excitation conductor again. The electromagnetic wave from the direction opposite to the waveguide short circuit of the excitation conductor is reflected by the screw type matching stub, and is arranged at such a distance that the component returning to the direction opposite to the waveguide short circuit of the excitation conductor again cancels out. It is.

Further, the coaxial waveguide converter according to the third aspect of the present invention provides a waveguide waveguide on a waveguide wall in a direction opposite to a waveguide short-circuiter as viewed from an excitation conductor, along a waveguide axis direction of the waveguide. Cut three screw holes at intervals of about a quarter wavelength of the electromagnetic wave propagating through
A screw penetrates from the outside of the waveguide into each screw hole.Electromagnetic waves from the direction opposite to the waveguide short circuit of the excitation conductor are reflected on the coaxial waveguide converter and guided again by the excitation conductor. The component returning in the direction opposite to the tube short circuit and the electromagnetic wave from the direction opposite to the waveguide short circuit of the excitation conductor are reflected by the three screw type matching stubs and return to the direction opposite to the waveguide short circuit of the excitation conductor again. The components cancel each other out.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 is a block diagram showing a first embodiment of the present invention, in which 1 is a circular waveguide, 2 is a Y-shaped waveguide short circuit, 3 is a folded excitation conductor, and 4 is a dielectric. Substrate, 5 is a strip conductor, 6 is a ground conductor, 7 is a microstrip line composed of dielectric substrate 4, strip conductor 5, and ground conductor 6, 8 is a quarter for impedance matching
A wavelength microstrip line transformer, 9 is a transformer cover, 10 is a coaxial connector, and 11 is a metal-made metal attached to the inner wall of the waveguide 1 opposite to the waveguide short-circuiter 2 when viewed from the excitation conductor 3. It is a matching stub. Here, the mounting position of the matching stub 11 is such that the electromagnetic wave from the direction opposite to the waveguide short-circuit device 2 of the excitation conductor 3 is reflected on the coaxial waveguide converter and is again brought into contact with the waveguide short-circuit device 2 of the excitation conductor 3. The amplitude of the component returning in the opposite direction and the component of the excitation conductor 3 returning from the direction opposite to the waveguide short circuit 2 after being reflected by the matching stub 11 from the direction opposite to the waveguide short circuit 2. Are selected so that they are almost the same, and the phases of the respective components are opposite phases, that is, the phase difference is 180 degrees. Specifically, the distance between the excitation conductor 3 and the matching stub 11 is set to about a quarter of the wavelength of the electromagnetic wave propagating in the waveguide, and the length of the matching stub 11 is set to a quarter of the electromagnetic wave propagating in the waveguide 1. One wavelength or less.

FIG. 2 shows how the distance to the surface of earth and sand is measured in the first embodiment of the present invention, under the same measurement conditions as in FIG.

Embodiment 2 FIG. FIG. 3 is a block diagram showing a second embodiment of the present invention. In the drawing, 1 is a circular waveguide, 2 is a Y-shaped waveguide short circuit, 3 is a folded excitation conductor, and 4 is a dielectric. A substrate 5, a strip conductor, 6 a ground conductor, 7 a microstrip line composed of a dielectric substrate 4, a strip conductor 5, and a ground conductor 6, a quarter-wave microstrip line transformer 8 for impedance matching,
Reference numeral 9 denotes a transformer cover, reference numeral 10 denotes a coaxial connector, and reference numeral 12 denotes a screw-type matching stub that can change the penetration length into the waveguide by using the matching stub 11 as a screw type. A specific distance between the excitation conductor 3 and the screw-type matching stub 12 is set to about a quarter wavelength of the electromagnetic wave propagating through the waveguide.

Embodiment 3 FIG. 4 is a block diagram showing a third embodiment of the present invention, in which 1 is a circular waveguide, 2 is a Y-shaped waveguide short circuit, 3 is a folded excitation conductor, and 4 is a dielectric. A substrate 5, a strip conductor, 6 a ground conductor, 7 a microstrip line composed of a dielectric substrate 4, a strip conductor 5, and a ground conductor 6, a quarter-wave microstrip line transformer 8 for impedance matching,
9 is a transformer cover, 10 is a coaxial connector, 12 is a screw-type matching stub, and 13 is a three screw-type matching stub with an interval of about a quarter wavelength of an electromagnetic wave propagating through the waveguide. It is a continuous tuner. Specifically, the distance between the excitation conductor 3 and the screw-type matching stub 12 close to the excitation conductor is set to about a quarter wavelength of the electromagnetic wave propagating through the waveguide.

[0016]

According to the first invention, the multiple reflection between the coaxial waveguide converter in the waveguide and the surface to be measured can be minimized, and the error in measuring the distance to the surface to be measured can be reduced. There is.

According to the second invention, when the state of the excitation conductor of the coaxial waveguide converter in the waveguide and the state of the waveguide short circuit change, the coaxial waveguide converter viewed from the waveguide side changes. There is an effect that it can be adjusted to some extent so that the reflection of the vessel becomes small.

According to the third aspect of the present invention, the reflection of the coaxial waveguide converter viewed from the waveguide side can be adjusted to be small irrespective of the individual characteristics of the coaxial waveguide converter. There is an effect that the adjustment can be made almost perfectly even when the state of the excitation conductor and the waveguide short circuit of the coaxial waveguide converter changes.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a coaxial waveguide converter according to the present invention.

FIG. 2 is a diagram showing a time domain waveform at the time of measurement using the coaxial waveguide converter according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram showing Embodiment 2 of a coaxial waveguide converter according to the present invention.

FIG. 4 is a configuration diagram showing Embodiment 3 of a coaxial waveguide converter according to the present invention.

FIG. 5 is a configuration diagram showing a conventional coaxial waveguide converter.

FIG. 6 is a diagram showing a distance measurement system using a conventional coaxial waveguide converter.

FIG. 7 is a diagram showing a time domain waveform at the time of measurement using a conventional coaxial waveguide converter.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 waveguide, 2 waveguide short circuit, 3 excitation conductor, 4 dielectric substrate, 5 strip line, 6 ground conductor, 7 microstrip line, 8 quarter wavelength microstrip line transformer, 9 cover, 10 Coaxial connector, 1
Reference Signs List 1 matching stub, 12 screw type matching stub, 13 triple tuner, 14 coaxial waveguide converter, 15 earth and sand, 16
Network analyzer, 17 coaxial cable.

Claims (3)

[Claims] 1. A waveguide is disposed radially in a waveguide substantially parallel to a tube axis from a central portion of a waveguide section, one end of the central portion is electrically connected to each other, and the other end is respectively connected to the waveguide. A waveguide short-circuiter having a plate-shaped conductor electrically connected to an inner wall of the tube and electrically dividing a waveguide section over a predetermined length;
The center conductor extending toward the center of the inside of the waveguide is extended through a hole formed in the wall surface of the waveguide, and is folded back at a length of about a quarter wavelength of the electromagnetic wave propagating through the waveguide. An excitation conductor connected to a wall, and an impedance matching circuit provided outside the waveguide connected to the excitation conductor, the excitation conductor being excited by the excitation conductor and propagating in the waveguide toward the waveguide short circuiter. Coaxial waveguide converter that combines the reflected electromagnetic wave and the electromagnetic wave propagating in the opposite direction to the waveguide short circuit in a phase that reinforces the coaxial waveguide converter, in a direction opposite to the waveguide short circuit when viewed from the excitation conductor. One end of the waveguide converter is generated such that the electromagnetic wave propagated from the waveguide converter is reflected by the waveguide converter and again generates a reflected wave synthesized with a phase that cancels the reflected wave propagating in the opposite direction to the waveguide short circuit. The other end is connected to the inner wall of the waveguide Coaxial waveguide converter, characterized in that it comprises a reflector which is bought. 2. A reflector formed by cutting a threaded hole in a waveguide wall and penetrating a screw from the outside of the waveguide toward the center of the waveguide cross section from the inner wall of the waveguide. 2. The coaxial waveguide converter according to 1. 3. A waveguide wall is provided with three screw holes at intervals of about one-quarter wavelength of an electromagnetic wave propagating in the waveguide along the tube axis direction of the waveguide. 2. The coaxial waveguide converter according to claim 1, wherein a screw penetrates the hole from outside the waveguide to form a reflector extending from the inner wall of the waveguide toward the center of the cross section of the waveguide.