A frequency selective unit and a frequency selective surface for the low frequency range

Abstract

The utility model relates to the technical field of antenna stealth, specifically relates to a frequency selection unit and frequency selection surface for low frequency range, the frequency selection unit is spliced by first metal layer, second metal layer, third metal layer and fourth metal layer, the first metal layer is formed by MXM square metal patch, wherein 3<=M<=7 and M is odd, second metal layer is spliced by four sub metal layer units and second metal layer is central symmetry structure, the sub metal layer unit is the structure after first metal layer equal proportion reduction to one fourth, third metal layer and first metal layer structure are same and both are in diagonal position, fourth metal layer and second metal layer structure are same and both are in diagonal position, the frequency selection unit structure simple in the utility model can realize the absorption of internal fixed frequency point electromagnetic wave, and the electromagnetic wave of other frequency is completely transparent, can satisfy the frequency selection of antenna, and does not influence the use of antenna itself.

Description

Technical Field

[0001] This utility model relates to the field of antenna stealth technology, specifically to a frequency selection unit and frequency selection surface for the low-frequency range. Background Technology

[0002] As wireless communication systems develop towards higher frequencies and greater density, the electromagnetic scattering characteristics of antennas have become a key factor affecting the stealth performance of equipment. Therefore, reducing the radar cross section of communication equipment has become an important means of stealth and has received much attention. The radar cross section of the antenna in communication equipment contributes significantly to the overall radar cross section. Therefore, it is necessary to design a material to reduce the radar cross section of the antenna in communication equipment.

[0003] The current approach involves adding a frequency-selective layer to the radome surface, allowing specific frequencies to pass through while absorbing other frequencies, thus not affecting the antenna's actual operation. However, current frequency-selective layers have complex shapes and weak targeting, easily leading to resource waste.

[0004] In view of this, this utility model is hereby proposed. Utility Model Content

[0005] This invention provides a frequency selection unit and frequency selection surface for the low-frequency range, solving the problems of complex shapes, weak targeting, and easy waste of resources in current frequency selection layers.

[0006] To achieve the above objectives, this utility model provides the following technical method:

[0007] A frequency selection unit for low-frequency range is provided, the frequency selection unit being composed of a first metal layer, a second metal layer, a third metal layer and a fourth metal layer. The first metal layer is formed by M×M square metal patches, where 3≤M≤7 and M is an odd number. The second metal layer is composed of four sub-metal layer units and has a centrally symmetrical structure. The sub-metal layer units are structures that are scaled down to one-quarter of the size of the first metal layer. The third metal layer has the same structure as the first metal layer and the two are located diagonally opposite each other. The fourth metal layer has the same structure as the second metal layer and the two are located diagonally opposite each other.

[0008] Specifically, the first metal layer has an axisymmetric structure, and both diagonals of the first metal layer are axes of symmetry. The two diagonals are the first diagonal and the second diagonal, respectively. The first diagonal is the line connecting the upper left corner and the lower right corner of the first metal layer, and the second diagonal is the line connecting the lower left corner and the upper right corner of the first metal layer.

[0009] Specifically, in the first metal layer, the diagonal connecting the lower left and upper right corners of the metal patch is the third diagonal, and metal patches that are on the same third diagonal have the same side length.

[0010] Specifically, the metal patch located on the second diagonal has the smallest side length, while the metal patches located on both sides of the second diagonal have increasingly larger side lengths as the distance between them and the second diagonal increases.

[0011] Specifically, M=5, the smallest metal patch has a side length of 0.5X~0.65X, and the largest metal patch has a side length of X.

[0012] Specifically, the side lengths of the metal patches, from smallest to largest, are 0.65X, 0.75X, 0.8X, 0.9X, and X.

[0013] Specifically, the thickness of the metal patch is 0.01 mm to 0.5 mm.

[0014] This embodiment also proposes a frequency selection surface for the low-frequency range, which is composed of multiple frequency selection units as described above.

[0015] The advantages of this utility model are specifically reflected in the following aspects:

[0016] The frequency selection unit in this invention is formed by a specific arrangement of multiple square metal patches, resulting in a simple structure. After electromagnetic waves pass through the radar absorbing layer surface, they can absorb electromagnetic waves at a fixed internal frequency point while completely transmitting electromagnetic waves of other frequencies. This satisfies the frequency selection requirement for the antenna, preventing external electromagnetic waves used for scanning from entering at low frequencies while not affecting the antenna's own electromagnetic wave emission and reception of specific frequency electromagnetic waves. Furthermore, the frequency selection unit in this invention can operate in high-temperature environments, offering flexible application scenarios and greatly expanding its scope of use. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the frequency selection unit of this utility model;

[0018] Figure 2 This is a schematic diagram of the structure of the first metal layer of this utility model;

[0019] Figure 3 This is a schematic diagram of the structure of the second metal layer of this utility model;

[0020] Figure 4 This is a diagram showing the electromagnetic wave absorption results corresponding to the frequency selection unit of this utility model;

[0021] Reference numerals: 1, First metal layer; 101, Metal patch; 102, First diagonal; 103, Second diagonal; 104, Third diagonal; 2, Second metal layer; 201, Sub-metal layer unit; 3, Third metal layer; 4, Fourth metal layer. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0023] Example 1

[0024] refer to Figures 1 to 3 This embodiment provides a frequency selection unit for the low-frequency range. The frequency selection unit is composed of a first metal layer 1, a second metal layer 2, a third metal layer 3, and a fourth metal layer 4. The first metal layer 1 is formed by M×M square metal patches 101. The metal patches 101 can be made of gold, silver, aluminum, copper, nickel, or chromium, and have a thickness of 0.01 mm to 0.5 mm. In this example, the metal patches 101 are made of copper and have a thickness of 0.3 mm. The second metal layer 2 is composed of four sub-metal layer units 201 and has a centrally symmetrical structure. The sub-metal layer units 201 are the structure of the first metal layer 1 scaled down to one-quarter of its original size. The third metal layer 3 has the same structure and material as the first metal layer 1 and they are located diagonally opposite each other. The fourth metal layer 4 has the same structure and material as the second metal layer 2 and they are located diagonally opposite each other. Where M is an odd number, and the preferred value range is 3≤M≤7. In this embodiment, M=5. In this embodiment, the frequency selection unit consists of multiple square metal patches 101 arranged in a specific structure. The structures of the first metal layer 1, the second metal layer 2, the third metal layer 3 and the fourth metal layer 4 also have a certain regularity. The structure is simple and can achieve the effect of accurately selecting low-frequency electromagnetic waves.

[0025] Specifically, the first metal layer 1 has an axisymmetric structure, and both diagonals of the first metal layer 1 are axes of symmetry. The two diagonals are the first diagonal 102 and the second diagonal 103. The first diagonal 102 is the line connecting the upper left corner and the lower right corner of the first metal layer 1, and the second diagonal 103 is the line connecting the lower left corner and the upper right corner of the first metal layer 1. In the first metal layer 1, the metal patches 101 on the same line as the third diagonal 104 have the same side length, wherein the third diagonal 104 is the diagonal connecting the lower left corner and the upper right corner of the metal patch.

[0026] The metal patch 101 located on the second diagonal 103 has the smallest side length. That is, the third diagonal 104 of the metal patch 101 with the smallest side length is on the same line as the second diagonal 103. The greater the distance between the metal patches 101 located on either side of the second diagonal 103 and the second diagonal 103, the larger their side lengths. The smallest metal patch 101 has a side length of 0.5X~0.65X, and the largest metal patch 101 has a side length of X. For example, in this embodiment, the extensions of the two adjacent sides of the metal patches 101 at the four corners of the frequency absorbing unit form a square. In the first metal layer 1, the five metal patches 101 in the first row have lengths of X, 0.9X, ... from left to right. 0.8X, 0.75X, 0.65X, so the lengths of the five metal patches 101 in the second row from left to right are 0.9X, 0.8X, 0.75X, 0.65X, 0.75X, respectively; the lengths of the five metal patches 101 in the third row from left to right are 0.8X, 0.75X, 0.65X, 0.75X, 0.8X, respectively; the lengths of the five metal patches 101 in the fourth row from left to right are 0.75X, 0.65X, 0.75X, 0.8X, 0.9X, respectively; and the lengths of the five metal patches 101 in the fifth row from left to right are 0.65X, 0.75X, 0.8X, 0.9X, X, respectively. In this embodiment, X is 0.3mm.

[0027] In the above embodiments, the side length of the square formed by the extension lines of the two adjacent sides of the metal patches 101 at the four corners of the frequency absorbing unit, the distance between each metal patch 101, and the side length of each metal patch 101 can all be determined according to design requirements and are not limited to those listed in the above embodiments.

[0028] Example 2

[0029] This embodiment proposes a frequency selective surface for low frequency range. The frequency selective surface is disposed on a metal substrate, such as an antenna radome. The frequency selective surface can be formed by a frequency selective unit in a single embodiment, or it can be spliced ​​together by multiple frequency selective units in embodiment 1.

[0030] To better illustrate the beneficial effects of this invention, the inventors conducted absorption tests on the frequency selection unit proposed in Embodiment 1, and the absorption results were obtained for reference. Figure 4 ,from Figure 4 It can be seen that the frequency selection unit proposed in this invention has excellent absorption capability in the low-frequency range of 1.3GHz-3.5GHz. Therefore, it can form a stopband in the range of 1.3GHz-3.5GHz and a passband in the remaining frequency bands. The resulting frequency selection surface allows electromagnetic waves of some frequencies to be absorbed while the remaining bands can pass through.

[0031] The above description is merely a specific embodiment of this utility model, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this utility model.

[0032] It should be understood that this utility model is not limited to the content already described above, and modifications and changes can be made without departing from its scope. The scope of this utility model is limited only by the appended claims.

Claims

1. A frequency selection unit for the low-frequency range, characterized in that, The frequency selection unit is composed of a first metal layer (1), a second metal layer (2), a third metal layer (3) and a fourth metal layer (4). The first metal layer (1) is formed by M×M square metal patches (101), where 3≤M≤7 and M is an odd number. The second metal layer (2) is composed of four sub-metal layer units (201) and the second metal layer (2) is a centrally symmetrical structure. The sub-metal layer unit (201) is the structure of the first metal layer (1) scaled down to one-quarter. The third metal layer (3) has the same structure as the first metal layer (1) and the two are located diagonally opposite each other. The fourth metal layer (4) has the same structure as the second metal layer (2) and the two are located diagonally opposite each other.

2. The frequency selection unit for the low-frequency range according to claim 1, characterized in that, The first metal layer (1) has an axisymmetric structure, and both diagonals of the first metal layer (1) are axes of symmetry. The two diagonals are the first diagonal (102) and the second diagonal (103). The first diagonal (102) is the line connecting the upper left corner and the lower right corner of the first metal layer (1), and the second diagonal (103) is the line connecting the lower left corner and the upper right corner of the first metal layer (1).

3. The frequency selection unit for the low-frequency range according to claim 2, characterized in that, In the first metal layer (1), the diagonal connecting the lower left and upper right corners of the metal patch (101) is the third diagonal (104), and the metal patches (101) on the same line as the third diagonal (104) have the same side length.

4. The frequency selection unit for the low-frequency range according to claim 3, characterized in that, The metal patch (101) located on the second diagonal (103) has the smallest side length. The side lengths of the metal patches located on both sides of the second diagonal (103) gradually increase as the distance between them and the second diagonal (103) increases.

5. The frequency selection unit for the low-frequency range according to claim 4, characterized in that, M=5, the side length of the smallest metal patch (101) is 0.5X~0.65X, and the side length of the largest metal patch (101) is X.

6. The frequency selection unit for the low-frequency range according to claim 5, characterized in that, The side lengths of the metal patch (101) from smallest to largest are 0.65X, 0.75X, 0.8X, 0.9X, and X.

7. The frequency selection unit for the low-frequency range according to claim 1, characterized in that, The thickness of the metal patch (101) is 0.01 mm to 0.5 mm.

8. A frequency selective surface for use in the low-frequency range, characterized in that, It is composed of multiple frequency selection units as described in any one of claims 1 to 7.

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