JP2001298301A - Waveguide connecting element, impedance matching method for the same and s band radar system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waveguide connecting element which allows impedance matching of waveguides in different forms while changing the direction of waveguide. SOLUTION: A rectangular waveguide 2 is connected to one joint 4 and a flat waveguide 3 is connected to the other joint 5. In order to match the impedance of both waveguides, heights (a) and (b) of two E corners 7 and 8 in the direction of E, namely, the dimensions of cuts 7a and 8a are suitably set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveguide connecting element for connecting a waveguide for transmitting a high frequency wave such as a microwave and changing the direction of the guided wave, and an impedance conversion method for the same. The present invention relates to an S-band radar device using a connection element.

[0002]

2. Description of the Related Art Waveguides, coaxial cables, and the like have been put into practical use as waveguides.
Various shapes such as a rectangular waveguide, a flat waveguide, and a circular waveguide have been put to practical use. Since these waveguides have different characteristics, they are used properly depending on the situation.

The aerial of a marine radar is 30
Since it is required to withstand high-speed rotation of about revolutions per minute and strong wind at a wind speed of 100 m / s, it is necessary to make the shape as low as possible in air resistance. The high-frequency pulse oscillated by the oscillator is supplied from the tip of the antenna via a waveguide, but as a waveguide for transmitting this high-frequency pulse, an S-band radar or the like having a large waveguide size conventionally has the most air. Coaxial cables with low resistance were used.

[0004]

However, since both the output terminal of the oscillator and the input terminal of the antenna are waveguides, coaxial-waveguide conversion elements are required at both ends of the coaxial cable. Further, when the frequency becomes about S band (about 3 GHz), the coaxial cable has a large loss. Since the coaxial cable is not self-supporting, there have been various problems such as the necessity of separately providing a horizontal bar for suspending and supporting the coaxial cable.

Therefore, it is conceivable to use a waveguide as a waveguide from the oscillator to the antenna. However, a conventional rectangular waveguide has a problem that the air resistance is large because the height in the E direction is large. Therefore, a flat waveguide may be used. However, since the input end of the antenna is a normal rectangular waveguide, a converter for converting impedance at the input terminal is required. The connection of the waveguide to the antenna is performed by turning the waveguide by 180 ° at the tip of the antenna as shown in FIG. 5B, and both a corner element and an impedance conversion element for this turn are provided. This is difficult at the tip of the antenna where space is limited, and the air resistance also increases.

According to the present invention, while changing the direction of the waveguide,
An object of the present invention is to provide a waveguide connecting element capable of performing impedance matching of waveguides having different shapes and an impedance matching method thereof.

[0007]

According to the first aspect of the present invention, there are provided two junctions for connecting two waveguides having different shapes, a plurality of direction changing parts for changing the direction of the waveguide, and An impedance matching unit for matching the impedance of the junction,
It is characterized by having.

According to a second aspect of the present invention, there is provided a waveguide connection in which a first junction connecting a rectangular waveguide and a second junction connecting a flat waveguide are connected via two corners. The element is characterized in that the cut-off dimension of each corner is set so that the impedance of the first joint and the impedance of the second joint match.

According to a third aspect of the present invention, in the second aspect of the present invention, when λ is a signal wavelength and m is an arbitrary integer, the length of the matching portion is (2m + 1) λ / 8 (where λ is (Indicating the wavelength in the waveguide).

According to a fourth aspect of the present invention, there is provided a waveguide connection in which a first junction connecting a rectangular waveguide and a second junction connecting a flat waveguide are connected via two corners. By adjusting the cut-off dimension of each corner in the element,
The impedance of the first junction and the impedance of the second junction are matched.

According to a fifth aspect of the present invention, the waveguide connecting element according to any one of the first, second, and third aspects is connected to the feeder of the antenna, and the flat waveguide is connected to the waveguide connecting element. Are connected.

A corner or a bend is used as an element for changing the direction of the waveguide, but by making this shape appropriate, the reactance of that portion can be changed. The impedances of the waveguides of different shapes connected to each other can be matched. Thus, the connection element that changes the direction of the waveguide can also serve as a matching element that matches the impedance of the waveguide having a different shape.

The corner elements include an E corner and an H corner. In the second to fourth aspects of the present invention, the combination of the two corners includes two E corners, two H corners or one E corner. Any combination of one H corner may be used. In general, the corner has a shape in which a rectangular waveguide is bent by 90 degrees, and the corner is cut into a triangle (triangular prism) and narrowed. By changing the size of the cut, the impedance (reactance) of the portion changes. . Therefore, in the present invention, the impedance matching of two waveguides having different shapes is achieved by appropriately setting the cut-off dimension. Then, the length of the matching portion is set to (2m + 1) λ / 8
As a result, the design of the cutout dimension, that is, the alignment is facilitated.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A waveguide connecting element according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of the waveguide connecting element divided into upper and lower parts. FIG.
It is a plane sectional view in the state where a waveguide was connected to the same waveguide connection element. The waveguide connection element 1 has a substantially U-shape including two E corners, and connects the two waveguides so that the waveguide turns 180 degrees. One joint 4 has a structure for holding the rectangular waveguide 2, and the other joint 5 has a structure for holding the flat waveguide 3. The waveguide connecting element 1 is manufactured by die-casting a conductive non-ferrous metal such as aluminum. When this waveguide connection element is used for an S-band radar, the rectangular waveguide is R32
(Inner diameter 72.1 mm × 34.0 mm: wall thickness 2 mm), and the flat waveguide is M32 (inner diameter 72.1 mm × 18.0 mm).
mm: wall thickness 2 mm).

An intermediate portion 6 between the two E corners 7 and 8
Has a length C of (3/8) λ ≒ 5.0 so that the impedance of the rectangular waveguide 2 and the flat waveguide 3 can be easily matched.
cm. The length of the rectangular waveguide 2 in the E direction is A (= 34 mm), and the length of the flat waveguide in the E direction is B
(= 18 mm), the length of the intermediate portion 6 in the E direction is √
(A · B) (≒ 24.7 mm). Two E
The waveguides of the corners 7 and 8 are narrowed by cut-offs 7a and 8a each having a triangular prism shape at the corners.
This part functions as an inductor. The length of the E corner 7 in the E direction is a, and the length of the E corner 8 in the E direction is b.

By appropriately setting a and b, the impedance of the rectangular waveguide 2 and the impedance of the flat waveguide 3 are matched. By setting the length C of the intermediate portion 6 to (3/8) λ, the vectors of the reflection coefficients at both corners 7 and 8 are orthogonal to each other, and it is easy to achieve matching.

A method of adjusting the impedance matching between the rectangular waveguide 2 and the flat waveguide 3 by the cut-and-try method will be described with reference to the Smith chart of FIG. First, in FIG. 6A, the reflection coefficient (impedance) of one of the prototyped waveguide connection elements from the other is measured.
It is assumed that the obtained reflection coefficient is, for example, a value plotted in FIG. When the height b of the E corner 8 is changed, the reactance changes and the reflection coefficient moves on the circular arc (isoresistance curve) B1 in the direction of the arrow. Then, b is adjusted to an appropriate size so that the reflection coefficient becomes P2. This P2 is obtained by rotating a circle of R / Z ₀ = 1 by 270 degrees. That is, next to the height a of the E corner 7
Is adjusted, but E corner 7 and E corner 8 are 3λ
This is because the direction of change of the vector of the reflection coefficient when the reactance is changed is shifted by 270 degrees because the distance is / 8.

Next, in FIG. 1B, when the height a of the E corner 7 is changed, the reactance changes and the reflection coefficient moves on the circular arc (isoresistance curve) B2 in the direction of the arrow. Then, a is adjusted to an appropriate size so that the reflection coefficient becomes P3. This P3 is the center of the Smith chart, which means that the impedance matching between the rectangular waveguide side and the flat waveguide side has been achieved.

As described above, the length of the intermediate portion 6 is set to (2 m +
1) By setting the length to λ / 8, the direction of change of the reflection coefficient vector when the height a of the E corner 7 or the length b of the E corner 8 is adjusted becomes orthogonal to facilitate the adjustment. Note that the heights a and b of the E corner correspond to the cutout dimensions 7a and 8a of the corner.

Next, the joint will be described with reference to FIG. This waveguide connecting element can be divided into an upper divided body 1b and a lower divided body 1a at the center of the H plane.
These divided bodies are connected by tightening the flanges 12a and 12b with bolts and nuts. At this time, the rectangular waveguide 2 and the flat waveguide 3 inserted into the joints 4 and 5
Is pinched. Hereinafter, the joint 4 will be described. Half-wavelength choke grooves 15 are formed near the respective end faces of the lower divided body 1a and the upper divided body 1b. The rectangular waveguide 2 has an end face cut in a direction perpendicular to the length direction thereof, and a notch groove 18 is provided in the vicinity of the end face of the bottom face 17 of the waveguide 2 in a direction perpendicular to the length direction of the waveguide 2. Are formed.

On the inner bottom surface 13 of the lower divided body 1a, there is provided a projection 14 which fits into the cutout groove 18. In order to connect the waveguide 2 to the connection element 1, the waveguide 2 is inserted into the inner surface of the lower divided body 1a, the notch groove 18 is fitted into the projection 14, and the flange of the upper divided body 1b is 12
b is brought into contact with the flange 12a of the lower divided body 1a, and both flanges are fixed with bolts and nuts, and the upper and lower short surfaces (E surfaces) of the waveguide 2 are clamped and fixed by the connection element 1. . The flat waveguide 3 and the joint 5 have the same configuration, and the rectangular waveguide 2 and the flat waveguide 3 are simultaneously bonded.

FIG. 4 shows a partial plan view of the lower divided body 1a in a state where the rectangular waveguide 2 is inserted into the joint 4 of the lower divided body 1a, and a horizontal sectional view near the end face of the waveguide 2. FIG. The lower divided body 1 is provided at the end face of the waveguide 2 and near the end face.
A gap 19 starting from the end face of the waveguide 2 is provided between the gap a and a, and the length d1 of the gap 19 is made equal to １ ／ wavelength. In addition, the lower divided body 1a starts from the end point of the gap 19 as a starting point.
A groove 20 continuous with the gap 19 is provided in a direction parallel to the waveguide 2 in the inside, and its length d2 is made equal to に wavelength. The gap 19 and the groove 20 are provided in the upper divided body 1b in the same manner. The sum of the lengths d1 and d2 is ２
Since the half wavelength choke groove 15 is formed by the gap 19 and the groove 20, the reflection of the microwave does not occur at the connection point 21 between the waveguide 2 and the connection element 1. The example in which the groove 20 is provided in parallel with the waveguide 2 has been described, but the direction is not particularly limited as long as the length of the groove 20 is equal to 特 に wavelength.

FIG. 5A is a diagram showing an example in which the above-described waveguide connection element 1 is applied to an S-band radar device. In the drawing, the antenna 30 receives power supply of a high-frequency pulse from a power supply unit 30a at the end thereof, and outputs a received reflected echo from the power supply unit 30a. The rectangular waveguide joining section 4 of the above-described waveguide connecting element 1 is connected to the feeding section 30a,
A flat waveguide 31 for feeding power is connected to the flat waveguide junction 5 on the opposite side. This flat waveguide has an antenna 30
And is connected to a rotary joint (not shown) inside the rotating shaft 32. The rotary joint is connected to a transmission unit (magnetron) and a reception unit via an isolator. As described above, the flat waveguide 31 is used as the feeding waveguide, and the connection between the flat waveguide 31 and the antenna 30 and the impedance matching are performed by one waveguide connection element 1.
The cross-sectional area of the entire antenna in the rotation direction can be reduced, and the air resistance during rotation can be reduced.

In the above embodiment, the waveguide connection element having two E corners has been described. However, a waveguide connection element having two H corners can be designed according to the same theory. In the above embodiment, the connection directions of the two corners are also connected such that the waveguide direction turns 180 degrees.
The connection may be such that the waveguide direction moves in a swastika shape in parallel.
Furthermore, the present invention can be applied to a device that connects the E corner and the H corner to change the waveguide direction spatially (not in the same plane).

In the above-described embodiment, the connection between the rectangular waveguide used for the S band and the flat waveguide is described. However, the frequency band and the shape of the waveguide are not limited thereto.

[0026]

According to the present invention, it is possible to connect a waveguide having a different shape to the connection element for changing the direction of the guided wave and also to serve as a matching element for matching the impedance. Further, according to the present invention, it is possible to reduce the air resistance in the rotational direction of the antenna of the S-band radar.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a waveguide connecting element according to an embodiment of the present invention.

FIG. 2 is a plan sectional view of the waveguide connecting element.

FIG. 3 is a Smith chart for explaining impedance matching of the waveguide connecting element.

FIG. 4 is a cross-sectional view of the vicinity of a joint of the waveguide connecting element.

FIG. 5 is a schematic structural diagram of an antenna part of an embodiment of the present invention and a conventional S-band radar device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Waveguide connection element 1a ... Lower divided body 1b ... Upper divided body 2 ... Rectangular waveguide 3 ... Flat waveguide 4 ... Joint part (of rectangular waveguide) 5 ... (of flat waveguide) Joining part 6 ... Alignment part 7,8 ... E corner 7a, 8a ... Cut off 12a, 12b ... Flange 13 ... Inner bottom surface 14 ... Protrusion 15 ... Half wavelength choke groove 17 ... Bottom 18 ... Notch groove 19 ... Gap 20 ... Groove 21 … Connection point

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takeshi Omori 9-52 Ashihara-cho, Nishinomiya-shi, Hyogo F-term in Furuno Electric Co., Ltd. (reference) 5J011 DA05

Claims (5)

[Claims] 1. A method for connecting two waveguides having different shapes.
A waveguide connection element, comprising: one junction, a plurality of direction changing units that change the direction of the waveguide, and an impedance matching unit that matches the impedance of the two junctions. 2. A first joint for connecting a rectangular waveguide,
What is claimed is: 1. A waveguide connecting element in which a flat joint is connected to a second joint through two corners, wherein the cut-off dimension of each corner is determined by the first joint and the second joint. A waveguide connection element set so that the impedance of the waveguide is matched. 3. The length of the matching section, λ is the signal wavelength, m
3. The waveguide connection element according to claim 2, wherein, when is an arbitrary integer, (2m + 1) λ / 8. 4. A first joint for connecting a rectangular waveguide,
In a waveguide connecting element in which a flat joint is connected to a second joint through two corners, the cut-off dimension of each corner is adjusted, and the first joint and the second joint are adjusted. An impedance matching method for a waveguide connecting element for matching the impedance of a junction. 5. The antenna according to claim 1, wherein the antenna power supply unit is provided.
4. An S-band radar device, wherein the waveguide connection element according to claim 3 is connected, and a flat waveguide is connected to the waveguide connection element.