JP4057761B2 - Waveguide connection element, waveguide connection element impedance matching method, and S-band radar apparatus - Google Patents

Description

[0001]
BACKGROUND 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 waveguide, an impedance conversion method therefor, and an S band using the waveguide connecting element. The present invention relates to a radar device.
[0002]
[Prior art]
Waveguides, coaxial cables, etc. have been put to practical use as waveguides. Of these, waveguides of various shapes such as rectangular waveguides, flat waveguides, circular waveguides have been put to practical use. Has been. Since these waveguides have different characteristics, they are properly used according to the situation.
[0003]
By the way, since the antenna of the marine radar is required to withstand high speed rotation of about 30 times / minute and strong wind of 100 m / s, it is necessary to make the air resistance as low as possible. The high-frequency pulse oscillated by the oscillator is supplied from the tip of the antenna via the waveguide. Conventionally, the S-band radar having a large waveguide size has the most air as a waveguide for transmitting the high-frequency pulse. A coaxial cable with low resistance was used.
[0004]
[Problems to be solved by the invention]
However, since both the output terminal of the oscillator and the input terminal of the antenna are waveguides, a coaxial-waveguide conversion element is required at both ends of the coaxial cable. Further, when the frequency is about S band (about 3 GHz), the coaxial cable has a large loss. Since the coaxial cable is not self-supporting, there are various problems such as a separate horizontal bar that suspends and supports the coaxial cable.
[0005]
Therefore, it is conceivable to use a waveguide as a waveguide line from the oscillator to the antenna. However, a normal rectangular waveguide has a problem that 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 that converts impedance at the input terminal is required. As shown in FIG. 5B, the waveguide is connected to the antenna by turning the waveguide by 180 ° at the tip of the antenna. Both the corner element and the impedance conversion element are provided for this turn. This is difficult at the tip of the antenna with space limitations, and there is a problem that air resistance increases.
[0006]
An object of the present invention is to provide a waveguide connecting element capable of performing impedance matching of waveguides having different shapes while changing the waveguide direction, and an impedance matching method thereof.
[0007]
[Means for Solving the Problems]
The invention of claim 1 is a waveguide connecting element in which a first joint for connecting a rectangular waveguide and a second joint for connecting a flat waveguide are connected via two corners. Thus, the cut-off dimension of each corner is matched with the impedance when the first junction portion side is viewed from the rectangular waveguide to the impedance when the flat waveguide side is viewed from the second junction portion. It is characterized by setting .
[0008]
According to a second aspect of the present invention, the first and second joint portions have 90 ° corners, and the rectangular waveguide and the flat waveguide are arranged in parallel to each other. The junction is arranged at the ends of the rectangular waveguide and the flat waveguide so that the propagation path is folded back .
[0009]
According to a third aspect of the present invention, in the second aspect of the present invention, when the length of the matching portion is λ is a signal wavelength and m is an arbitrary integer, (2m + 1) λ / 8 (λ is a wavelength in the waveguide) It is characterized by the following.
[0010]
The invention according to claim 4 is a waveguide connection element in which a first junction for connecting rectangular waveguides and a second junction for connecting flat waveguides are connected via two corners. The impedance of the first joint and the second joint is matched by adjusting the cut-off dimension of each corner.
[0011]
In the invention of claim 5, the waveguide connecting element according to claim 1, 2 or 3 is connected to the feeding portion of the antenna, and a flat waveguide is connected to the waveguide connecting element. It is characterized by that.
[0012]
Corners, bends, etc. are used as elements to change the direction of the waveguide. By making this shape appropriate, the reactance of that part can be changed, and this is used to connect to both ends. It is possible to match impedances of differently shaped waveguides. As a result, the connecting element that changes the direction of the waveguide can also serve as a matching element that matches the impedances of the waveguides having different shapes.
[0013]
The corner elements include an E corner and an H corner. In the inventions of claims 2 to 4, a combination of two corners is two E corners, two H corners, or one E corner and one H corner. Any combination of corners is acceptable. 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) to narrow it. The impedance (reactance) of the portion changes by changing the size of the cut-off. . Therefore, in the present invention, impedance matching between two waveguides having different shapes is obtained by appropriately setting the cut-off dimension. The length of the matching portion is set to (2m + 1) λ / 8, thereby facilitating the design of the cut-off dimensions, that is, matching.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
A waveguide connection 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. 2 is a cross-sectional plan view of a state where a waveguide is connected to the waveguide connection element.
The waveguide connecting 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 sandwiching the rectangular waveguide 2, and the other joint 5 has a structure for sandwiching 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 connecting element is used for an S-band radar, R32 (inner diameter 72.1 mm × 34.0 mm: wall thickness 2 mm) is used for the rectangular waveguide, and M32 (inner diameter 72.1 mm) is used for the flat waveguide. × 18.0 mm: wall thickness 2 mm).
[0015]
The intermediate portion 6 between the two E corners 7 and 8 has a length C of (3/8) λ≈5.0 cm so that impedances of the rectangular waveguide 2 and the flat waveguide 3 can be easily matched. Has been. When 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). The two E corners 7 and 8 each have a corner narrowed by triangular prism-shaped cut-outs 7a and 8a, and these portions function as inductors. 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.
[0016]
By appropriately setting these 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, making it easy to achieve matching.
[0017]
A method for adjusting impedance matching between the rectangular waveguide 2 and the flat waveguide 3 by the cut-and-trie method will be described with reference to the Smith chart of FIG. First, in FIG. 2A, the reflection coefficient (impedance) of one of the prototyped waveguide connection elements is measured. Assume that the obtained reflection coefficient is a value plotted in FIG. When the height b of the E corner 8 is changed, the reactance changes and the reflection coefficient moves in the direction of the arrow on the circular arc (isoresistance curve) B1. 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, the height a of the E corner 7 is adjusted next, but since the E corner 7 and the E corner 8 are separated by 3λ / 8, the change direction of the vector of the reflection coefficient when the reactance is changed. This is because of a deviation of 270 degrees.
[0018]
Next, in FIG. 5B, when the height a of the E corner 7 is changed, the reactance changes and the reflection coefficient moves in the direction of the arrow on the circular arc (isoresistance curve) B2. Then, a is adjusted to an appropriate size so that the reflection coefficient becomes P3. This P3 is the center of the Smith chart, thereby matching the impedance of the rectangular waveguide side and the flat waveguide side.
[0019]
By changing the length of the intermediate portion 6 to (2m + 1) λ / 8 as described above, the change direction of the reflection coefficient vector when the height a of the E corner 7 or b of the E corner 8 is adjusted is changed. It becomes orthogonal and adjustment becomes easy. Note that the heights a and b of the E corner correspond to the cut-off dimensions 7a and 8a of the corner.
[0020]
Next, the joint portion will be described with reference to FIG. The waveguide connecting element can be divided into an upper divided body 1b and a lower divided body 1a at the center of the H surface, and these divided bodies are connected by fastening flanges 12a and 12b with bolts and nuts. Is done. At this time, the rectangular waveguide 2 and the flat waveguide 3 inserted into the joint portions 4 and 5 are sandwiched. Hereinafter, the joint portion 4 will be described. Half-wave choke grooves 15 are formed in the vicinity of the 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 its length direction, and a notch groove 18 is formed 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. Is formed.
[0021]
Further, a protrusion 14 that fits into the notch groove 18 is provided on the inner bottom surface 13 of the lower divided body 1a. 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 cutout groove 18 is fitted into the protruding portion 14, and the flange of the upper divided body 1b is inserted. 12b is brought into contact with the flange 12a of the lower divided body 1a, both the flanges are fixed with bolts and nuts, and the upper and lower short surfaces (E surface) of the waveguide 2 are clamped and fixed by the connecting element 1. . The flat waveguide 3 and the joint 5 have the same configuration, and the waveguides are joined by the rectangular waveguide 2 and the flat waveguide 3 at the same time.
[0022]
FIG. 4 is a diagram showing a partial plan view of the lower divided body 1a and a horizontal sectional view in the vicinity of the end face of the waveguide 2 in a state where the rectangular waveguide 2 is inserted into the joint 4 of the lower divided body 1a. . A gap 19 starting from the end face of the waveguide 2 is provided between the end face of the waveguide 2 and in the vicinity of the end face 1a, and the length d1 of the gap 19 is equal to ¼ wavelength. To do. Further, a groove 20 continuous with the gap 19 is provided in the lower split body 1a in the direction parallel to the waveguide 2 with the end point of the gap 19 as the starting point, and its length d2 is equal to ¼ wavelength. To do. The gap 19 and the groove 20 are similarly provided for the upper divided body 1b. The sum of the lengths d1 and d2 is equal to ½ wavelength, and therefore, the half-wave choke groove 15 is formed by the gap 19 and the groove 20, so that a micropoint is formed at the connection point 21 between the waveguide 2 and the connection element 1. There is no wave reflection. The example in which the groove 20 is provided in parallel with the waveguide 2 has been described. However, the direction of the groove 20 is not particularly limited as long as the length of the groove 20 is equal to ¼ wavelength.
[0023]
FIG. 5A is a diagram showing an example in which the waveguide connecting element 1 is applied to an S-band radar device. In the figure, the antenna 30 is fed with a high frequency pulse from the feeding portion 30a at the end thereof, and outputs the received reflected echo from the feeding portion 30a. A rectangular waveguide joint 4 of the above-mentioned waveguide connection element 1 is connected to the power feeding portion 30a, and a flat waveguide 31 for power feeding is connected to the flat waveguide joint 5 on the opposite side. Yes. The flat waveguide is guided to the rotating shaft 32 of the 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 a power supply waveguide, and the connection between the flat waveguide 31 and the antenna 30 and the impedance matching are performed by the single waveguide connecting element 1. The cross-sectional area of the whole rotation direction can be reduced, and the air resistance at the time of rotation can be reduced.
[0024]
In the above embodiment, the waveguide connecting element having two E corners has been described. However, a device having two H corners can be designed by the same theory. In addition, the connection direction of the two corners is also connected so that the waveguide direction turns 180 degrees in the above-described embodiment, but may be connected so that the waveguide direction moves in parallel in a bowl shape. Furthermore, the present invention can also be applied to a device in which the E corner and the H corner are connected to change the waveguide direction spatially (not within the same plane).
[0025]
Moreover, although the said embodiment demonstrated what connects the rectangular waveguide used for S band, and a flat waveguide, a frequency band and the shape of a waveguide are not limited to this.
[0026]
【The invention's effect】
According to the present invention, the connecting element that changes the direction of the waveguide can serve as a matching element that connects the waveguides having different shapes and matches the impedance.
According to the present invention, the air resistance in the rotation direction of the antenna of the S-band radar can be reduced.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a waveguide connection 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 the joint of the waveguide connecting element.
FIG. 5 is a schematic structural diagram of an antenna portion 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 part divided body 1b ... Upper part divided body 2 ... Rectangular waveguide 3 ... Flat waveguide 4 ... Joint part 5 (of the rectangular waveguide) ... (of flat waveguide) Joining part 6 ... matching parts 7 and 8 ... E corners 7a and 8a ... Cut-offs 12a and 12b ... Flange 13 ... Inner bottom face 14 ... Projection part 15 ... Half-wave choke groove 17 ... Bottom face 18 ... Notch groove 19 ... Clearance 20 ... Groove 21 ... connection point

Claims (5)

A waveguide connection element in which a first joint for connecting a rectangular waveguide and a second joint for connecting a flat waveguide are connected via two corners,
The cut-off dimension of each corner was set so that the impedance of the rectangular waveguide viewed from the first junction side matched the impedance of the second junction viewed from the flat waveguide side . Waveguide connection element. The first and second joints are each 90 ° corners, and the rectangular waveguide and the flat waveguide are arranged in parallel to each other, and the signal propagation path is folded at the joint. The waveguide connection element according to claim 1, wherein the joint portion is disposed at an end portion of the rectangular waveguide and the flat waveguide . The length of the matching section, the signal wavelength lambda, when m is an arbitrary integer, (2m + 1) λ / 8 and so as waveguide connecting device according to claim 1 or 2 was. In the waveguide connecting element in which the first joint for connecting the rectangular waveguide and the second joint for connecting the flat waveguide are connected via two corners,
By adjusting the cut-off dimension of each corner, the impedance of the rectangular waveguide as viewed from the first junction is matched with the impedance of the second junction as viewed from the flat waveguide . Impedance matching method for waveguide connection element. An S-band radar apparatus in which the waveguide connecting element according to claim 1, 2 or 3 is connected to an antenna feeding unit, and a flat waveguide is connected to the waveguide connecting element.

Images