JP2023146436A - Frequency selective plate - Google Patents

Abstract

To provide a frequency selective plate whose transmission characteristics do not deteriorate even when the incident direction of radio waves is wide angle.SOLUTION: A frequency selective plate 100 has a first dielectric substrate 101 and a second dielectric substrate 104. The first dielectric substrate 101 has a first conductor layer 102 and a second conductor layer 103 with a plurality of frequency selective elements with conductor patterns that transmit radio waves of a first frequency and reflect radio waves of a second frequency. The second dielectric substrate 104 is stacked on the top surface of the first conductor layer 102.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD This disclosure relates to frequency selection plates.

In order to reduce the RCS (Radar Cross Section) of aircraft, flying objects, ships, etc., a technology in which the frequency selection plate 100 is placed in front of the antenna is required. Conventional frequency selection plates have had a major problem with transmission loss. In order to compensate for the transmission loss of the frequency selection board, it was necessary to increase the number of modules and increase the aperture diameter of the antenna, thereby increasing the antenna gain, resulting in high costs. Therefore, in order to realize a low-cost antenna, a frequency selection plate having low loss transmission characteristics is required. In particular, the transmission characteristics of the frequency selection plate in the wide-angle direction generally have a large loss and need to be improved.

For example, patent documents describe configurations of frequency selection plates. The frequency selection board described in the patent document has a structure in which a dielectric sheet having a plurality of circular ring-shaped elements is arranged on the front and back sides with a spacer in between. The frequency selection plate as described above is designed to reflect or transmit radio waves of a specific frequency by arranging circular ring elements that resonate at a certain frequency.

Japanese Patent Publication No. 6-177639

The configuration of a frequency selection plate as described in patent documents is generally determined so as to match the impedance when radio waves are incident from the front direction. Therefore, when the direction of incidence of radio waves becomes a wide-angle direction, there is a problem that the impedance changes and the transmission characteristics deteriorate.

A frequency selection plate according to the present disclosure includes a first dielectric substrate and a conductor pattern formed on the first dielectric substrate that transmits radio waves of a first frequency and reflects radio waves of a second frequency. The device includes first and second conductor layers having a plurality of frequency selection elements formed thereon, and a second dielectric substrate laminated on the first conductor layer.

According to the present disclosure, the second dielectric substrate operates as a matching layer when radio waves are incident from a wide-angle direction, so that the transmission characteristics at the time of wide-angle incidence are improved.

5 is a diagram showing transmission and reflection of radio waves in the frequency selection plate 100 according to the first embodiment. FIG. FIG. 3 is a diagram showing a longitudinal cross-sectional view of the frequency selection board 100 according to the first embodiment. 1 is an exploded perspective view showing the configuration of a frequency selection plate 100 according to Embodiment 1. FIG. FIG. 2 is a top view showing the element shape of frequency selection board 100 according to Embodiment 1. FIG. 3 is a diagram showing an example of an element shape created in a conductor layer according to Embodiment 1. FIG. 7 is a diagram showing a longitudinal cross-sectional view of a frequency selection board 100 according to a second embodiment. FIG. FIG. 2 is an exploded perspective view showing the configuration of a frequency selection plate 100 according to a second embodiment. 7 is a diagram showing a longitudinal cross-sectional view of a frequency selection board 100 according to a third embodiment. FIG. 7 is an exploded perspective view showing the configuration of a frequency selection plate 100 according to a third embodiment. FIG. 7 is a top view of frequency selection board 100 according to Embodiment 3. FIG. FIG. 7 is a diagram showing the configuration of a frequency selection board 100 according to a fourth embodiment. 7 is a diagram showing a longitudinal cross-sectional view of a frequency selection board 100 according to a fourth embodiment. FIG. 7 is an exploded perspective view showing the configuration of a frequency selection plate 100 according to Embodiment 4. FIG. FIG. 7 is a diagram showing a configuration of a frequency selection version 100 according to a fifth embodiment. 7 is an exploded perspective view showing the configuration of a frequency selection plate 100 according to Embodiment 5. FIG.

Embodiments of the present disclosure will be described below with reference to the drawings. In each figure, the same or corresponding parts are given the same reference numerals. Duplicate explanations will be simplified or omitted as appropriate. Note that the present disclosure is not limited to the embodiments described below.

Embodiment 1.
A frequency selection board 100 according to Embodiment 1 of the present disclosure will be described with reference to FIGS. 1 to 5.
FIG. 1 is a diagram showing transmission and reflection of radio waves through the frequency selection plate 100. FIG. 2 is a longitudinal cross-sectional view of the frequency selection plate 100 according to the first embodiment. FIG. 3 is an exploded perspective view showing the configuration of frequency selection plate 100 according to the first embodiment. FIG. 4 is a diagram showing the element shape of the frequency selection plate 100 shown in FIG. 2. FIG. 5 shows an example of the element shape created in the conductor layer. As shown in FIGS. 2 to 5, the frequency selection board 100 according to the first embodiment includes a first dielectric substrate 101, a first conductor layer 102, a second conductor layer 103, a second dielectric substrate 104, a first element 105, and a second element 106.

As shown in FIG. 1, the frequency selection plate 100 has a characteristic that when the radio wave 1000a has the first frequency, it passes through the frequency selection plate 100 like the radio wave 1000b of the first frequency, and the radio wave 1000a has the first frequency. 2, it has a characteristic of being reflected or scattered by the frequency selection plate 100, like the radio wave 1000c of the second frequency.
Note that the first frequency is a higher frequency than the second frequency, the second frequency is a lower frequency than the first frequency, and the frequency difference between the low and high frequencies is determined by design. It is between 0.4 times and 0.7 times when the frequency is 1.

The first dielectric substrate 101 includes a first conductor layer 102 formed on the front surface and a second conductor layer 103 formed on the back surface. That is, the back surface of the first conductor layer 102 is laminated on the front surface of the first dielectric substrate 101, and the surface of the second conductor layer 103 is laminated on the back surface of the first dielectric substrate 101. The back side of the second conductor layer 102 faces the space.
The material of the dielectric substrate 101 is not a so-called printed circuit board, but may be a dielectric material such as a spacer, a honeycomb substrate, Rohacell, or a foaming agent. Furthermore, although the first embodiment is described as having one layer, it may be configured with one or more layers, or may have a multilayer configuration in which the above-mentioned spacers and the like are combined. Assuming that the wavelength propagating in the dielectric is λ, the first dielectric substrate 101 has a thickness of d as shown in FIG. 2, and is 0.01 times or more the wavelength λ of the first frequency designed in advance. It has a thickness less than 0.25 times.
Note that in FIG. 2, the x-axis is an axis parallel to the surface of the second dielectric substrate 104, and the z-axis is an axis perpendicular to the surface of the second dielectric substrate 104 and the spatial direction. θ is the angle between the z-axis and the direction of incidence of the radio wave.

The second dielectric substrate 104 is laminated on the surface side of the first conductor layer 102. The second dielectric substrate 104 has a thickness of d as shown in FIG. 1, and is arranged on the space side from the first conductor layer 102. The thickness d of the second dielectric substrate 104 is 0.01 times or more and less than 0.25 times the wavelength λ of the first frequency (wavelength that propagates in the dielectric) designed in advance.
The material of the second dielectric substrate 104 is mainly composed of dielectric. Although the first embodiment is described with one layer, it may be configured with one or more layers.

As shown in FIG. 3, a plurality of first elements 105 are arranged on the first conductor layer 102 at a predetermined distance apart. A plurality of second elements 106 are arranged on the second conductor layer 103 at a predetermined distance apart. The correspondence between the second conductor layer 103 and the second element 106 is shown in FIG. 3 by replacing the first conductor layer 102 with the second conductor layer 103 and replacing the first element 105 with the second element 106. It is the same as the thing.
In the first embodiment, the first conductor layer 102 and the second conductor layer 103 are described as two layers, but the first conductor layer 102 or the second conductor layer 103 may be one layer.
The dimensions and shapes of the first element 105 and the second element 106 are adjusted so that they have electrical characteristics that transmit radio waves of a first frequency and reflect or scatter radio waves of a second frequency. .

As an example of the first element 105, a ring-shaped element 107 is described. The ring-shaped element 105 is formed by a conductor pattern having an annular groove portion with a predetermined groove width δ and a conductor layer peeled off. The dielectric surface of the annular groove is exposed, and a circular conductor patch whose diameter D2 is half of the wavelength λ of the first frequency is formed inside the annular groove. The outer diameter of the annular groove is equal to the diameter D2 plus 2δ. The first element 105 may have a conductor pattern shape other than the ring shape, which is the first element shape 107 as shown in FIG. For example, the first element 105 has a second element shape 108 which is a circular patch shape, a third element shape 109 which is a cross shape in which grooves of peeled dielectric intersect in a cross shape, and a fourth element shape 110. A double ring shape in which two large and small annular conductors with different diameters are arranged concentrically, a fifth element shape 111 in which a groove formed by peeling off the dielectric forms a rectangular shape, and a sixth element shape 112 in a rectangular shape. Any conductor pattern shape, such as a certain meander line shape, may be used.

Next, the operation of frequency selection board 100 according to the first embodiment will be explained.
The radio waves of the first frequency transmitted through the second dielectric substrate 104 from the space on the surface side of the second dielectric substrate 104 are transmitted through the first conductor layer 102 formed on the first dielectric substrate 101, It resonates in the plurality of frequency selection elements 105 and 106 of the second conductor layer 103, transmits through the first dielectric substrate 101, and propagates to the back side of the second conductor layer 103.
Similarly, the radio waves of the first frequency transmitted through the first dielectric substrate 101 from the space on the back surface side of the second conductor layer 103 are transmitted through the second conductor layer 103 formed on the first dielectric substrate 101. , resonates in the plurality of frequency selection elements 106 and 105 of the first conductor layer 102, transmits through the second dielectric substrate 104, and propagates to the space on the front side of the second dielectric substrate 104.
On the other hand, the second frequency radio waves transmitted through the second dielectric substrate 104 from the space on the surface side of the second dielectric substrate 104 are transmitted through the first dielectric substrate 101, the first conductor layer 102, the second The light cannot pass through the frequency selection plate 100 composed of the conductor layer 103 and the plurality of frequency selection elements 105 and 106, and is reflected or scattered into the space on the surface side of the second dielectric 104.

Generally, adding layers of dielectric increases losses.
However, in the frequency selection plate 100 according to the first embodiment, the thickness of the second dielectric substrate 102 is adjusted so as to match the impedance of the space in the state of wide-angle incidence of θ=45° or more from the θ=60° direction. and determine the electrical material constants.

According to the frequency selection board 100 according to the first embodiment described above, the first dielectric substrate 101, the first conductor layer 102, the second conductor layer 103, the second dielectric substrate 104, the first The structure includes an element 105 and a second element 106. Thereby, the second dielectric substrate becomes a matching layer, and the transmission characteristics when radio waves are incident at a wide angle are improved.

Embodiment 2.
A frequency selection board 100 according to a second embodiment of the present disclosure will be described with reference to FIGS. 6 and 7. The same configurations as in the first embodiment are given the same reference numerals, and the explanation thereof will be omitted, and the configurations that are different from the first embodiment will be explained.

FIG. 6 is a longitudinal cross-sectional view of the frequency selection plate 100 according to the second embodiment. FIG. 7 is an exploded perspective view showing the configuration of frequency selection plate 100 according to the second embodiment. As shown in FIGS. 6 and 7, the frequency selection board 100 according to the second embodiment has a configuration in which a third dielectric substrate 201 is further added to the frequency selection board 100 of the first embodiment.

Next, the operation of the frequency selection board 100 according to the second embodiment will be explained using FIG. 6.
In FIG. 6, the x-axis is an axis parallel to the surface of the second dielectric substrate 104, the z-axis is an axis perpendicular to the surface of the second dielectric substrate 104 and the spatial direction, and the angle θ is , is the angle between the z-axis and the direction of incidence of radio waves.
In the second embodiment, the second dielectric substrate 104 is arranged on the space side with respect to the first conductor layer 102, and the third dielectric substrate 201 is arranged on the space side with respect to the second conductor layer 103. It is placed. Generally, adding layers of dielectric increases losses.
However, the thickness of the second dielectric substrate 104 and the third dielectric substrate 113 and the electrical By determining the material constants, the transmission characteristics when radio waves are incident at wide angles can be improved.

According to the frequency selection board 100 according to the second embodiment described above, the third dielectric substrate 201 is provided in addition to the frequency selection board 100 according to the first embodiment. As a result, the second dielectric substrate 104 and the third dielectric substrate 201 become matching layers, and the transmission characteristics when radio waves are incident at a wide angle are improved.

Embodiment 3.
A frequency selection board 100 according to Embodiment 3 of the present disclosure will be described with reference to FIGS. 8 and 9. The same configurations as in the second embodiment are given the same reference numerals, and the explanation thereof will be omitted, and the configurations that are different from the second embodiment will be explained.

FIG. 8 is a longitudinal cross-sectional view of the frequency selection plate 100 according to the third embodiment. FIG. 9 is an exploded perspective view showing the configuration of frequency selection plate 100 according to the third embodiment. FIG. 10 is a top view of frequency selection board 100 according to the third embodiment. As shown in FIGS. 8 to 10, the frequency selection board 100 according to the third embodiment has a configuration in which a first metamaterial 301 and a second metamaterial 302 are further added to the structure of the second embodiment. .

Next, the configuration of frequency selection board 100 according to Embodiment 3 will be described.
In the third embodiment, the first metamaterial 301 and the second metamaterial 302 have a split ring shape as shown in FIG. 10, but they may have any shape. Further, a plurality of first metamaterials 301 are arranged on the dielectric substrate 104 at a predetermined distance apart.
The correspondence between the dielectric substrate 201 and the first metamaterial 301 is the same as in FIG. 9 in which the dielectric substrate 104 is replaced with the dielectric substrate 201 and the first metamaterial 301 is replaced with the second metamaterial 302. It is.
Further, although the first metamaterial 301 and the second metamaterial 302 are arranged on both sides with the substrate in between, they may be arranged on one side.

The dimensions, shape, etc. of the metamaterial are determined so as to match the impedance of the first metamaterial 301 and the second metamaterial 302 in a wide-angle incident state.
The first metamaterial 301 in FIG. 10 shows an example in which an annular groove portion having a so-called C-shape in which a portion of the annular portion is missing is formed in the conductor layer.

The frequency selection board 100 according to the third embodiment described above has the same role as the second dielectric substrate 104 and the third dielectric substrate 201 described in the second embodiment. 2 metamaterial 302 is further added. As a result, the transmission characteristics when radio waves are incident at a wide angle can be improved compared to the configuration having the second dielectric substrate 104 and the third dielectric substrate 201 shown in Embodiment 2.

Embodiment 4.
A frequency selection board 100 according to Embodiment 4 of the present disclosure will be described with reference to FIGS. 11 to 13. The same configurations as in the first embodiment are given the same reference numerals, and the explanation thereof will be omitted, and the configurations that are different from the first embodiment will be explained.

FIG. 11 shows the configuration of a frequency selection board 100 according to the fourth embodiment. FIG. 12 is a longitudinal cross-sectional view of the frequency selection plate 100 according to the fourth embodiment. FIG. 13 is an exploded perspective view of the frequency selection plate 100 according to the fourth embodiment. As shown in FIGS. 11 to 13, a frequency selection board 100 according to the fourth embodiment has a configuration in which a fourth dielectric substrate 401 and a patch antenna 402 are added to the structure of the first embodiment, and as shown in FIG. , a plurality of patch antennas 402 are used to form a patch array antenna.
In FIG. 11, a patch antenna 402 is formed on a fourth dielectric substrate 401. The fourth dielectric substrate 401 has a configuration example in which a patch antenna 402 is placed facing the third dielectric substrate 201 with a predetermined gap therebetween. It shows.
Further, FIG. 12 shows a configuration example of another aspect in which the fourth dielectric substrate 401 is laminated on the third dielectric substrate 201 with the patch antenna 402 facing the third dielectric substrate 201. There is.
13 shows, in FIG. 12, a second dielectric substrate 104, a second conductor layer 102, a first dielectric substrate 101, a second conductor layer 103, a third dielectric substrate 201, a patch antenna 402, FIG. 4 is a perspective view schematically expressing the laminated structure and arrangement relationship in which each layer of the fourth dielectric substrate 401 is laminated in order from the top.

Next, the configuration of frequency selection board 100 according to Embodiment 4 will be explained. In the fourth embodiment, the patch antenna 402 shown in FIG. 13 is shown as having a rectangular shape, but it may have any shape such as a circular shape or a ring shape. Further, although the antenna is limited to a patch antenna or a patch array antenna, any antenna such as a dipole antenna, a horn antenna, or a slot antenna may be used. Further, as shown in FIG. 11, the distance between the plurality of patch antennas 402 and the third dielectric substrate 201 may be increased, or as shown in FIG. You don't have to keep a distance between them. Generally, the patch antenna and the frequency selection plate are designed separately, but the patch antenna 402 and the frequency selection plate 100 may be combined in a matching design.

According to the frequency selection board 100 according to the fourth embodiment described above, the configuration is the same as in the first embodiment except that the fourth dielectric substrate 401 and the patch antenna 402 are provided. As a result, the transmission characteristics when radio waves are incident at a wide angle can be improved compared to the configuration having the second dielectric substrate 104 and the third dielectric substrate 201 shown in Embodiment 2.

Embodiment 5.
A frequency selection board 100 according to Embodiment 5 of the present disclosure will be described with reference to FIGS. 14 and 15. The same configurations as those in the fourth embodiment are designated by the same reference numerals, and the description thereof will be omitted, and the configurations similar to those in the fourth embodiment will be described.

FIG. 14 is an exploded perspective view of the frequency selection plate 100 according to the fifth embodiment. As shown in FIGS. 14 and 15, a frequency selection plate 100 according to the fifth embodiment has a configuration in which a radome 501 is further added to the structure of the fourth embodiment.

Next, the configuration of frequency selection board 100 according to Embodiment 5 will be explained.
The radome 501 in the fifth embodiment protects the patch antenna 402 and the frequency selection plate 100, and generally deteriorates the transmission characteristics. The radome 501, the patch antenna 402, and the frequency selection plate 100 are generally designed individually, but they may all be combined for matching design.
The radome 501 is placed facing the second dielectric substrate 104 with a predetermined gap therebetween.
Further, the fourth dielectric substrate 401 has a configuration in which the patch antenna 402 is arranged with a predetermined gap therebetween, with the patch antenna 402 facing the third dielectric substrate 201. An example is shown.
It goes without saying that the fourth dielectric substrate 401 may be stacked on the third dielectric substrate 201 with the patch antenna 402 facing the third dielectric substrate 201.
The radome 501 is formed by fixing a cylindrical dielectric side surface around a disk-shaped front surface made of a dielectric, and the front surface and the side surface may be integrally formed.
15 shows the front side of the radome 501, the second dielectric substrate 104, the second conductor layer 102, the first dielectric substrate 101, the second conductor layer 103, and the third dielectric layer in FIG. FIG. 3 is a perspective view schematically expressing the laminated structure and arrangement relationship in which each layer of a substrate 201, a patch antenna 402, and a fourth dielectric substrate 401 are laminated in order from the front side of a radome 501.

According to the frequency selection plate 100 according to the fifth embodiment described above, a radome 501 is further added to the structure of the fourth embodiment. As a result, the transmission characteristics when radio waves are incident at a wide angle can be improved compared to the configuration shown in Embodiment 4. Further, by designing the radome 501, the frequency selection plate shown in Embodiment 4, and the patch antenna 402 as one unit, it is possible to realize an antenna with low overall electrical loss.

Note that the present disclosure is not limited to the embodiments described above, and within the scope of the present disclosure, any combination of the embodiments or modifications or variations of any constituent elements of the embodiments may be made. It is possible to omit any component in each of the above.

The frequency selection board 100 according to the present disclosure can be used, for example, in an antenna device having the frequency selection board 100.

1000a Radio waves incident on the frequency selection board 1000b Radio waves transmitted through the frequency selection board 1000c Radio waves 100 reflected on the frequency selection board Frequency selection board 101 First dielectric substrate 102 Second conductor layer 103 Second conductor Layer 104 Second dielectric substrate 105 First element 106 Second element 107 First element shape 108 Second element shape 109 Third element shape 110 Fourth element shape 111 Fifth element shape 112 6 element shape 201 Third dielectric substrate 301 First metamaterial 302 Second metamaterial 401 Fourth dielectric substrate 402 Patch antenna 501 Radome

Claims (14)

a first dielectric substrate;
First and second frequency selection elements formed on the first dielectric substrate and having a plurality of frequency selection elements each having a conductive pattern that transmits radio waves of a first frequency and reflects radio waves of a second frequency. a conductor layer; a second dielectric substrate laminated on the first conductor layer;
Frequency selection board with. 2. The frequency selection plate according to claim 1, wherein the second dielectric substrate transmits radio waves incident at an angle of 45° or more with respect to the layer thickness direction. 2. The frequency selection board according to claim 1, wherein the second dielectric substrate matches the impedance of the space with respect to radio waves incident at an angle inclined at least 60 degrees with respect to the layer thickness direction. The frequency selection element includes at least an annular element formed with an annular opening, a multiple annular element formed with concentric annular openings, a circular element, a slot-shaped slot element, a rectangular element, and a meander line-shaped element. The frequency selection board according to any one of claims 1 to 3, comprising one or more of them. The frequency selection board according to any one of claims 1 to 4, further comprising a third dielectric substrate laminated on the second conductor layer. Any one of claims 1 to 5, wherein the second dielectric substrate and the third dielectric substrate have a thickness of 0.01λ (wavelength) or more and less than 0.25λ (wavelength) at the first frequency. Frequency selection board as described in section. 7. The frequency selection board according to claim 1, wherein a plurality of frequency selection elements on the first and second conductor layers are arranged at predetermined intervals. 8. The frequency selection board according to claim 1, wherein the second dielectric substrate and the third dielectric substrate include a metamaterial. 9. The frequency selection board according to claim 8, wherein a plurality of metamaterials included in the second dielectric substrate and the third dielectric substrate are arranged at predetermined intervals. 10. The frequency selection plate according to claim 8, wherein the metamaterial has at least one or more of a split ring shape, a ring shape, and a rectangular shape. 8. The frequency selection board according to claim 1, further comprising a fourth dielectric substrate having an antenna laminated on the third dielectric substrate. 12. The frequency selection board according to claim 11, wherein a plurality of antennas on the fourth dielectric substrate are arranged at predetermined intervals. 13. The frequency selection board according to claim 11, wherein the antenna on the fourth dielectric substrate comprises at least one or more of a patch antenna, a dipole antenna, a horn antenna, and a slot antenna. The frequency selection board according to any one of claims 1 to 13, further comprising a radome on the space side of the second dielectric substrate.

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