Three-dimensional band elimination frequency selective surface

Abstract

The utility model provides a three-dimensional band-stop frequency selective surface, belongs to the technical field of microwaves, and solves the problems of poor angular stability and low frequency selection characteristic of the conventional frequency selective surface. According to the three-dimensional band-stop frequency selection surface, a plurality of units distributed in an array shape are arranged on the frequency selection surface, each unit is in a frame shape and internally provided with a medium cavity, two sets of adjacent metal strips which are symmetrical about the edges of the units in the circumferential direction are arranged in each medium cavity, and each set comprises two metal strips. The two metal strips are located in the same plane and are vertically symmetrical. The three-dimensional band-stop frequency selective surface is good in angle stability and high in frequency selection characteristic.

Description

Technical Field

[0001] This invention belongs to the field of microwave technology and relates to a three-dimensional bandstop frequency selective surface. Background Technology

[0002] A frequency selective surface (FSS) is a periodic array structure that has good selectivity for the transmission and reflection of electromagnetic waves. In its bandpass range, electromagnetic waves can pass through the FSS smoothly, while in its bandstop range, electromagnetic waves are completely reflected back. By adjusting and designing the periodic structure, different bandpass and bandstop ranges can be obtained.

[0003] The frequency selectivity of microwave filters (FSS) can be used to design microwave components such as filters. With the rapid development of materials science and technology and processing techniques, FSS has seen rapid development, offering advantages such as ease of fabrication and small size, attracting widespread attention. However, existing FSS are either large and not conformally compatible, or have small absorption bandwidth, limiting their practicality.

[0004] To this end, Chinese patent application (application number: 201510200529.2) discloses a frequency selective surface comprising 100 units and a base plate. The units are arranged in 10 rows and 10 columns, with the units in each row aligned horizontally and the units in each column aligned vertically. Each unit is a square sheet with a side length of 5.8 mm and a thickness of 0.1 mm. A square hole with a side length of 4.2 mm is opened in the center of each unit. The spacing between each unit is 1.9 mm. The units are made of a material with a relative permittivity of 1 and a conductivity of 200 S / m and are attached to a base plate made of insulating material.

[0005] However, the above method has the following drawbacks: 1. The design of this frequency selective surface is mainly based on a planar structure, in which the unit cells can only vary on one plane. Due to the single-planar characteristic of its structure, the frequency response is limited, usually exhibiting a relatively simple resonance effect, and cannot effectively support the selection of multiple frequency ranges, resulting in low frequency selectivity. 2. The frequency selectivity of this frequency selective surface is mainly adjusted within one plane. Such a structure is quite sensitive to changes in the angle of the incident wave. As the incident angle changes, the reflection and transmission characteristics of this frequency selective surface may change significantly, especially in the high-frequency range, where its performance often deteriorates significantly and its angular stability is poor. Utility Model Content

[0006] The purpose of this invention is to address the aforementioned problems in existing technologies by proposing a three-dimensional bandstop frequency selective surface. The technical problem this invention aims to solve is: how to achieve good angular stability and high frequency selectivity of the frequency selective surface.

[0007] The purpose of this utility model can be achieved through the following technical solution: a three-dimensional band-stop frequency selective surface, wherein the frequency selective surface is provided with a plurality of units distributed in an array, wherein the unit is frame-shaped and has a dielectric cavity inside, and the dielectric cavity is provided with two sets of adjacent metal strips that are symmetrical about the edge of the unit in the circumferential direction, each set of metal strips has two strips, and the two metal strips are located in the same plane and are symmetrical about the top and bottom.

[0008] Electromagnetic waves are incident on the metal strips, creating resonance and impeding their passage. The symmetrically placed metal strips couple with each other, achieving two transmission zeros within the stopband and forming a transmission pole on each side of the passband. The units are arranged in an array, allowing for flexible design of each unit's size and spacing, thus optimizing the overall shape and structure and further improving integration. Furthermore, the metal strips are placed within the dielectric frames of the units, effectively utilizing space and enabling miniaturization of the frequency selective surface. This band-stop frequency selective surface has a three-dimensional structure. The reflection and transmission of electromagnetic waves on this surface involve multi-dimensional interactions. When electromagnetic waves are incident at different angles, adjustments are made in multiple dimensions. The three-dimensional structure increases the interaction area between the electromagnetic wave and the material. The symmetrical arrangement of the metal strips maintains stable reflection and transmission characteristics at different incident angles, resulting in good angular stability of the frequency selective surface. The frequency selective surface can be optimized in three dimensions. The stopband bandwidth and filtering characteristics can be adjusted by adjusting the unit size. Alternatively, the position of the transmission poles in the upper and lower sidebands and the frequency selective characteristics of the sidebands, especially the frequency selective characteristics of the upper sideband, can be adjusted by adjusting the spacing between two metal strips in the same group in the height direction while keeping the stopband unchanged. This will result in high frequency selective characteristics of the frequency selective surface.

[0009] The aforementioned three-dimensional bandstop frequency selective surface comprises an outer plate, several horizontal plates, and several vertical plates. The outer plate is rectangular, the horizontal plates are straight and arranged in parallel, and the vertical plates are also straight and arranged in parallel. These horizontal and vertical plates are interleaved to form an array of units, dividing the space within the outer plate into several dielectric cavities. Each unit has a set of metal strips on its two adjacent sidewalls. By changing the spacing between the horizontal and vertical plates, the arrangement and spacing of the metal strips within different dielectric cavities can be adjusted accordingly, thereby flexibly adjusting the stopband bandwidth and filtering characteristics. This flexibility allows the frequency selective surface to be optimized over a wider frequency range to meet different application requirements. Because the metal strips are distributed on both adjacent sidewalls of the unit, this frequency selective surface can reflect electromagnetic waves of arbitrary polarization within the stopband.

[0010] In the aforementioned three-dimensional bandstop frequency selective surface, the metal strips are zigzag-shaped. When electromagnetic waves are incident on these zigzag-shaped metal strips, resonance occurs, impeding the passage of the electromagnetic waves. The symmetrically placed metal strips couple with each other, achieving two transmission zeros within the stopband and two transmission poles in the upper and lower sidebands, respectively, thus improving frequency selectivity. Repeated bending of the metal strips increases the mutual coupling between dipoles, reduces the unit cell size, and significantly optimizes the bandstop characteristics under oblique incidence.

[0011] The aforementioned three-dimensional band-stop frequency selective surface comprises a metal strip consisting of a first folded segment, two straight segments, and two second folded segments. Both ends of the first folded segment are connected to one end of each straight segment, and the other end of each straight segment is connected to one end of each second folded segment. The connected straight segments and second folded segments are symmetrical about the first folded segment. The first folded segment is a folded dipole with a first-order band-stop response. Straight segments serving as stubs are added to both ends of the first folded segment. Each additional straight segment corresponds to the addition of a second folded segment, further increasing coupling and reducing size.

[0012] In the aforementioned three-dimensional bandstop frequency selective surface, the widths of the horizontal portion of folded segment one, the straight segment, and the horizontal portion of folded segment two are the same, while the width of the vertical portion of folded segment one is greater than the width of the vertical portion of folded segment two. By optimizing the width and length of the strips, the coupling strength between resonators can be effectively adjusted, thereby obtaining the target bandstop frequency response characteristics.

[0013] The aforementioned three-dimensional band-stop frequency selective surface uses a metal strip made of copper. Copper is a metal with excellent electrical conductivity, capable of efficiently conducting current and rapidly forming resonance upon electromagnetic wave incidence, thus enhancing the reflection and transmission characteristics of the frequency selective surface. Copper effectively reflects electromagnetic waves, especially at high frequencies. Using a copper metal strip enhances the frequency selective surface's ability to reflect electromagnetic waves, thereby improving the band-stop characteristics. Copper possesses good ductility and machinability, allowing for the creation of complex metal strip shapes and structures through various manufacturing processes. This flexibility enables designers to more easily optimize the geometry of the metal strip to achieve the desired band-stop characteristics.

[0014] The aforementioned three-dimensional bandstop frequency selective surface, wherein the outer plate, horizontal plate, and vertical plate are made of a fiberglass-free substrate. The fiberglass-free substrate provides excellent dielectric constant and low loss characteristics. Compared to traditional materials, its dielectric constant is more uniform, which helps reduce signal attenuation and distortion, resulting in more stable signal transmission and lower insertion loss.

[0015] Compared with existing technologies, this three-dimensional bandstop frequency selective surface has the following advantages:

[0016] 1. In this three-dimensional bandstop frequency selective surface, the units are distributed in an array, which allows for flexible design of the size and spacing of each unit, thereby optimizing the overall shape and structure and further improving the integration. Moreover, the zigzag metal strips are set in the dielectric frame inside the unit, which effectively utilizes the space and thus miniaturizes the frequency selective surface.

[0017] 2. The frequency selection surface of this bandstop is a three-dimensional structure. During the reflection and transmission of electromagnetic waves on this surface, there are multiple dimensions of interaction. When electromagnetic waves are incident at different angles, they will be adjusted in multiple dimensions. Moreover, the three-dimensional structure increases the interaction area between electromagnetic waves and materials. The symmetrical arrangement of metal strips can maintain stable reflection and transmission characteristics at different incident angles, thus making the frequency selection surface angular stability good.

[0018] 3. In this three-dimensional band-stop frequency selective surface, the band-stop frequency selective surface can be optimized in three dimensions. The stopband bandwidth and filtering characteristics can be adjusted by adjusting the unit size. Alternatively, the frequency selective characteristics of the frequency selective surface, especially the frequency selective characteristics of the upper sideband, can be adjusted by changing the position of the sideband transmission poles while keeping the stopband unchanged by adjusting the spacing between two metal strips in the same group in the height direction. This results in high frequency selective characteristics of the frequency selective surface. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of an array of three-dimensional bandstop frequency selective surfaces.

[0020] Figure 2 This is a schematic diagram of the unit cell of this three-dimensional bandstop frequency selective surface.

[0021] Figure 3 This is a top view of a cell in a three-dimensional bandstop frequency selective surface.

[0022] Figure 4 This is a schematic diagram of a metal strip on one side of a cell in a three-dimensional bandstop frequency selective surface.

[0023] In the figure, 1 is the unit; 2 is the dielectric cavity; 3 is the metal strip; 3a is the first folded section; 3b is the straight section; 3c is the second folded section; 4 is the outer plate; 5 is the horizontal plate; and 6 is the vertical plate. Detailed Implementation

[0024] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0025] The specific embodiments described herein are merely illustrative examples illustrating the spirit of this utility model. Those skilled in the art to which this utility model pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of this utility model or exceeding the scope defined by the appended claims.

[0026] like Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, this three-dimensional bandstop frequency selective surface has several arrayed elements 1. With the center of the three-dimensional bandstop frequency selective surface as the origin of the coordinate axis, each element 1 extends symmetrically along the x-axis and y-axis, and the height of the element 1 extends along the z-axis.

[0027] Specifically, this frequency selective surface includes an outer plate 4, several horizontal plates 5, and several vertical plates 6. The outer plate 4 is rectangular, the horizontal plates 5 are flat and arranged in parallel, and the vertical plates 6 are flat and arranged in parallel. The horizontal plates 5 and vertical plates 6 are interleaved to form an array of units 1, dividing the space within the outer plate 4 into several dielectric cavities 2. A set of metal strips 3 is attached to the two adjacent sidewalls of each unit 1, and the metal strips 3 in each dielectric cavity 2 are circumferentially symmetrical about the edge of the unit 1. The metal strips 3 of each dielectric cavity 2 are arranged parallel to the x-axis and y-axis, respectively. Due to the symmetry of the structure, the x-polarized wave and the y-polarized wave have the same reflection coefficient and transmission coefficient. By changing the spacing between the horizontal plates 5 and the spacing between the vertical plates 6, the arrangement and spacing of the metal strips 3 in different dielectric cavities 2 can be adjusted accordingly in the horizontal and vertical directions, thereby flexibly adjusting the stopband bandwidth and filtering characteristics. This flexibility allows the frequency selective surface to be optimized over a wider frequency range to meet different application requirements. Because the metal strips 3 are distributed on both adjacent sidewalls of unit 1, this frequency-selective surface can reflect electromagnetic waves of arbitrary polarization within the stopband.

[0028] Each group of metal strips 3 consists of two strips, which are located in the same plane and are symmetrical vertically. Each metal strip 3 is zigzag-shaped. When electromagnetic waves are incident on the zigzag-shaped metal strips 3, they resonate and impede the passage of electromagnetic waves. The symmetrically placed metal strips 3 are coupled together, achieving two transmission zeros within the stopband. The repeated bending of the metal strips 3 increases the mutual coupling between dipoles, reduces the size of unit 1, and greatly optimizes the band-stop characteristics under oblique incidence.

[0029] The metal strip 3 includes a first folded segment 3a, two straight segments 3b, and two second folded segments 3c. Both ends of the first folded segment 3a are connected to one end of each straight segment 3b, and the other end of each straight segment 3b is connected to one end of each second folded segment 3c. The connected straight segments 3b and second folded segments 3c are symmetrical about the first folded segment 3a. The first folded segment 3a is a first-order band-stop folded dipole. Straight segments 3b, serving as stubs, are added to both ends of the first folded segment 3a. For each additional straight segment 3b, a second folded segment 3c is correspondingly added, further increasing coupling and reducing size.

[0030] The widths of the horizontal portion of folded segment 3a, straight segment 3b, and the horizontal portion of folded segment 3c are the same, while the width of the vertical portion of folded segment 3a is greater than that of the vertical portion of folded segment 3c. By optimizing the width and length of the strips, the coupling strength between resonators can be effectively adjusted, thereby obtaining the target band-stop frequency response characteristics.

[0031] The metal strip 3 is made of copper. Copper is a metal with excellent electrical conductivity, capable of efficiently conducting current and rapidly forming resonance when electromagnetic waves are incident, which helps improve the reflection and transmission characteristics of the frequency-selective surface. Copper effectively reflects electromagnetic waves, especially at high frequencies. Using a copper metal strip 3 enhances the frequency-selective surface's ability to reflect electromagnetic waves, thereby improving the band-stop characteristics. Copper has good ductility and machinability, allowing for the creation of complex shapes and structures for the metal strip 3 through various manufacturing processes. This flexibility enables designers to more easily optimize the geometry of the metal strip 3 to achieve the desired band-stop characteristics.

[0032] The outer plate 4, the horizontal plate 5, and the vertical plate 6 are made of a fiberglass-free substrate. The fiberglass-free substrate provides excellent dielectric constant and low loss characteristics. Compared with traditional materials, its dielectric constant is more uniform, which helps to reduce signal attenuation and distortion, resulting in more stable signal transmission and lower insertion loss.

[0033] Electromagnetic waves incident in free space along the Z-axis cause the metal strip 3 to resonate, hindering the passage of the electromagnetic waves. The half-wavelength corresponding to the resonant frequency is approximately the length of a single metal strip. Adjusting the length of the metal strip 3 can regulate the stopband center frequency. Since the metal strips 3 are distributed on both adjacent sidewalls of each unit 1, this frequency-selective surface can reflect electromagnetic waves of arbitrary polarization within the stopband. This process generates a second-order band-stop frequency response. Repeated bending of the metal strip 3 increases the mutual coupling between dipoles and reduces the size of unit 1. Due to the symmetry of the structure, x-polarized and y-polarized waves have identical reflection and transmission coefficients. Two parallel metal strips 3 on a single sidewall form a second-order response, resulting in two transmission zeros within the stopband and two transmission poles outside the stopband, which is beneficial for achieving high frequency selectivity of the frequency-selective surface.

[0034] The units 1 are arranged in an array, allowing for flexible design of the size and spacing of each unit 1, thereby optimizing the overall shape and structure and further improving integration. Furthermore, the metal strips 3 are placed within the dielectric frame inside the units 1, effectively utilizing space and miniaturizing the frequency selective surface. This band-stop frequency selective surface has a three-dimensional structure. During the reflection and transmission of electromagnetic waves on this surface, multi-dimensional interactions are involved. When electromagnetic waves are incident at different angles, adjustments occur in multiple dimensions. The three-dimensional structure increases the interaction area between the electromagnetic waves and the material. The symmetrical arrangement of the metal strips 3 maintains stable reflection and transmission characteristics at different incident angles, resulting in good angular stability of the frequency selective surface. This band-stop frequency selective surface can be optimized in three dimensions. The stopband bandwidth and filtering characteristics can be adjusted by changing the size of the units 1. Alternatively, the spacing between two metal strips 3 within the same group can be adjusted in the height direction, ensuring the stopband remains constant while adjusting the frequency selectivity of the sidebands, especially the upper sideband, thus achieving high frequency selectivity.

[0035] Although this document frequently uses the terms 1 (unit 1), 2 (medium cavity 2), 3 (metal strip 3), 3a (folded segment 1), 3b (straight segment 3b), 3c (folded segment 2), 4 (outer plate 4), 5 (horizontal plate 5), and 6 (vertical plate 6), the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of this utility model; interpreting them as any kind of additional limitation would contradict the spirit of this utility model.

Claims

1. A three-dimensional bandstop frequency selective surface, wherein the frequency selective surface is provided with a plurality of arrayed units (1), characterized in that, The unit (1) is square and has a medium cavity (2) inside. The medium cavity (2) has two sets of adjacent metal strips (3) that are symmetrical about the edge of the unit in the circumferential direction. Each set of metal strips (3) has two strips, and the two metal strips (3) are located in the same plane and are symmetrical about the top and bottom.

2. The three-dimensional bandstop frequency selective surface according to claim 1, characterized in that, The frequency selection surface includes an outer plate (4), several horizontal plates (5) and several vertical plates (6). The outer plate (4) is square, the horizontal plates (5) are flat and arranged in parallel, and the vertical plates (6) are flat and arranged in parallel. The horizontal plates (5) and vertical plates (6) are interleaved to form units (1) distributed in an array, and the space inside the outer plate (4) is divided into several dielectric cavities (2). A set of metal strips (3) is provided on the two adjacent side walls of each unit (1).

3. A three-dimensional bandstop frequency selective surface according to claim 1 or 2, characterized in that, The metal strip (3) is zigzag-shaped.

4. A three-dimensional bandstop frequency selective surface according to claim 3, characterized in that, The metal strip (3) includes a folded segment one (3a), two straight segments (3b) and two folded segments two (3c). The two ends of the folded segment one (3a) are respectively connected to one end of the straight segment (3b), and the other end of the straight segment (3b) is connected to one end of the folded segment two (3c). The connected straight segment (3b) and folded segment two (3c) are symmetrical about the folded segment one (3a).

5. A three-dimensional bandstop frequency selective surface according to claim 4, characterized in that, The width of the horizontal portion of the first folded segment (3a), the width of the straight segment (3b), and the width of the horizontal portion of the second folded segment (3c) are the same, and the width of the vertical portion of the first folded segment (3a) is greater than the width of the vertical portion of the second folded segment (3c).

6. A three-dimensional bandstop frequency selective surface according to claim 5, characterized in that, The metal strip (3) is made of copper.

7. A three-dimensional bandstop frequency selective surface according to claim 2, characterized in that, The outer plate (4), the horizontal plate (5) and the vertical plate (6) are made of fiberglass-free substrate.

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