Broadband frequency selective surface radome with wide-angle harmonic suppression function

Abstract

The invention belongs to the technical field of microwaves. The invention provides a broadband frequency selective surface radome with a wide-angle harmonic suppression function. According to the embodiment of the invention, the regular hexagonal periodic arrangement mode is selected, so that the structures of the FSS units under wide-angle incidence can be ensured to have good in-band wave-transparent characteristics and harmonic band suppression characteristics. By adopting the structure of the double-layer FSS unit, the wide wave-transparent bandwidth can be realized. A transmission zero point can be introduced by loading a circular hole on the aperture type FSS unit, and the position of the transmission zero point and the bandwidth of a stop band can be adjusted by adjusting the size of the circular hole, thereby achieving a good inhibition effect in a harmonic frequency band. By designing the FSS unit form, the wave-transparent bandwidth of the frequency selective surface structure is improved, and two transmission zeros are introduced at the harmonic position, so that good isolation is achieved in the harmonic band of the wave-transparent bandwidth. By optimizing the thickness and the stacking arrangement of the core layer, the filter has good passband transmission characteristics and harmonic band suppression characteristics under a large incident angle.

Description

Technical Field

[0001] The disclosed embodiments relate to the field of microwave technology, and in particular to a broadband frequency selective surface radome with wide-angle harmonic suppression function. Background Art

[0002] In radar systems, radomes play a vital role. They not only protect the antenna and electronic equipment inside the radome from the harsh external environment, but also do not affect the radar antenna's transmission and reception of electromagnetic wave signals to the minimum extent. In practical applications, radar systems not only radiate electromagnetic waves at their operating frequencies, but also radiate harmonics, especially the second harmonic, which has a large radiation power and will seriously affect the electromagnetic environment. It may make the equipment working at the harmonic frequency unable to work normally. Therefore, the design of frequency selective surface radomes is extremely important for radar harmonic suppression.

[0003] In previous related research literature, the main application of frequency selective surfaces in radar systems is RCS reduction. Outside the radar operating band, the radome has reflective characteristics, thereby reducing the RCS of the antenna by relying on the low RCS shape of the radome. However, in the related literature, the frequency selective surface structures designed by researchers either have extremely narrow bandwidth and good out-of-band steep drop, or extremely wide bandwidth and poor out-of-band steep drop, and have low passband transmittance or extremely poor out-of-band isolation at large angles of incidence.

[0004] Therefore, it is necessary to improve one or more problems existing in the above-mentioned related technical solutions.

[0005] It should be noted that this section is intended to provide background or context for the technical solutions of the present disclosure stated in the claims. The description herein is not admitted to be prior art by virtue of being included in this section. Summary of the invention

[0006] In order to avoid the shortcomings of the prior art, the present invention provides a broadband frequency selective surface radome with wide-angle harmonic suppression function, which is used to solve the problems in the prior art that either the bandwidth is extremely narrow and the out-of-band steep drop is good, or the bandwidth is extremely wide and the out-of-band steep drop is poor, and the passband transmittance is low or the out-of-band isolation is extremely poor at large angles of incidence.

[0007] According to an embodiment of the present disclosure, a broadband frequency selective surface radome with a wide-angle harmonic suppression function is provided, the radome comprising: The first skin, the first adhesive film, the first dielectric base, the first FSS layer, the second adhesive film, the core layer, the third adhesive film, the second FSS layer, the second dielectric base, the fourth adhesive film and the second skin are arranged in sequence.

[0008] Furthermore, the first FSS layer is composed of a plurality of first FSS units in the form of regular hexagons that are periodically and evenly arranged, and the second FSS layer is composed of a plurality of second FSS units in the form of regular hexagons that are periodically and evenly arranged, and both the first FSS unit and the second FSS unit are in the form of aperture-type regular hexagonal rings loaded with circular holes.

[0009] Further, the thickness of the first FSS unit and the second FSS unit are both 0.015 mm to 0.020 mm, the diameter of the circular hole of the first FSS unit is 1.05 mm to 1.15 mm, and the diameter of the circular hole of the second FSS unit is 0.85 mm to 0.95 mm.

[0010] Furthermore, the first skin and the second skin have the same thickness, and both have a thickness of 0.33 mm to 0.66 mm, a relative dielectric constant of 4.2 to 4.4, and a loss tangent of 0.005 to 0.01.

[0011] Furthermore, the materials of the first skin and the second skin are both cyanate ester or epoxy resin.

[0012] Furthermore, the thickness of the core layer is 2.3 mm to 2.7 mm, the relative dielectric constant is 1.0 to 1.1, and the loss tangent is 0.001 to 0.005.

[0013] Furthermore, the material of the core layer is PMI foam.

[0014] Furthermore, the thickness of the first adhesive film, the second adhesive film, the third adhesive film and the fourth adhesive film are all 0.08 mm to 0.12 mm, and the relative dielectric constants are all 2.8 to 3.2.

[0015] Furthermore, the thickness of the first dielectric substrate and the second dielectric substrate are both 0.1 mm to 0.15 mm, the relative dielectric constant is 3.0 to 3.3, and the loss tangent is 0.001 to 0.01.

[0016] Furthermore, the materials of the first dielectric substrate and the second dielectric substrate are both Rogers RT5880 or polyimide.

[0017] The technical solution provided by the embodiments of the present disclosure may have the following beneficial effects: In the embodiments of the present disclosure, through the above-mentioned broadband frequency selective surface radome with wide-angle harmonic suppression function, on the one hand, the periodic arrangement of regular hexagons can ensure that the structure of the FSS unit has good in-band transmission characteristics and harmonic band suppression characteristics under wide-angle incidence. The structure of the double-layer FSS unit can achieve a wider transmission bandwidth. Loading a circular hole on the aperture-type FSS unit can introduce a transmission zero point, and adjusting the size of the circular hole can adjust the transmission zero point position and the stopband bandwidth to achieve good suppression in the harmonic band. On the other hand, by designing the FSS unit form, not only the transmission bandwidth of the frequency selective surface structure is improved, but also two transmission zero points are introduced at the harmonic position, so that good isolation is achieved in the harmonic band of the transmission bandwidth. By optimizing the core layer thickness and the stacking arrangement, the frequency selective surface structure has good passband transmission characteristics and harmonic band suppression characteristics at large incident angles. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification are used to explain the principles of the present disclosure. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0019] Figure 1 A schematic structural diagram of a broadband frequency selective surface radome with wide-angle harmonic suppression function in an exemplary embodiment of the present disclosure is shown; Figure 2 A schematic diagram showing the structure of a first FSS unit and a second FSS unit in an exemplary embodiment of the present disclosure is shown; Figure 3 A schematic diagram showing a periodic arrangement of the first FSS layer in an exemplary embodiment of the present disclosure; Figure 4 The transmission characteristic curve simulation result of the broadband frequency selective surface radome with wide-angle harmonic suppression function under TE polarization in the exemplary embodiment of the present disclosure is shown; Figure 5 The transmission characteristic curve simulation result of the broadband frequency selective surface radome with wide-angle harmonic suppression function under TM polarization in the exemplary embodiment of the present disclosure is shown.

[0020] In the figure, 1, the first skin; 2, the first adhesive film; 3, the first dielectric substrate; 4, the first FSS layer; 41, the first FSS unit; 5, the second adhesive film; 6, the core layer; 7, the third adhesive film; 8, the second FSS layer; 9, the second dielectric substrate; 91, the second FSS unit; 10, the fourth adhesive film; 11, the second skin. DETAILED DESCRIPTION

[0021] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the disclosure will be more comprehensive and complete and to fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0022] In addition, the accompanying drawings are only schematic illustrations of the embodiments of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and their repeated descriptions will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0023] In this exemplary embodiment, a broadband frequency selective surface radar cover with wide-angle harmonic suppression function is provided. Figure 1 As shown in , the broadband frequency selective surface radar cover with wide-angle harmonic suppression function may include: A first skin (1), a first adhesive film (2), a first dielectric base, a first FSS layer (4), a second adhesive film (5), a core layer (6), a third adhesive film (7), a second FSS layer (8), a second dielectric base (9), a fourth adhesive film (10) and a second skin (11) are arranged in sequence.

[0024] Specifically, the broadband frequency selective surface radome with wide-angle harmonic suppression function comprises two layers of skin, one core layer (6), two layers of dielectric substrate, two layers of FSS, and four layers of adhesive film. The first and eleventh layers are the first skin (1) and the second skin (11), respectively, and are used as surface layers for impact resistance, water resistance and dust resistance; the sixth layer is the core layer (6), which is used as a structural strength support layer and also realizes lightness; the third and ninth layers are the first dielectric substrate (3) and the second dielectric substrate (9), respectively, and are used as carriers for the FSS metal layer, and the FSS metal layer is attached to one side of the dielectric substrate; the fourth and eighth layers are the first FSS layer (4) and the second FSS layer (8), respectively, and form filtering characteristics with wide passband wave transmission and harmonic suppression; the second, fifth, seventh and tenth layers are the first adhesive film (2), the second adhesive film (5), the third adhesive film (7) and the fourth adhesive film (10), respectively, and are used for bonding the first skin (1), the first dielectric substrate, the first FSS layer (4), the core layer (6), the second FSS layer (8), the second dielectric substrate (9) and the second skin (11) to form an integrated complete structure.

[0025] Through the above-mentioned broadband frequency selective surface radome with wide-angle harmonic suppression function, on the one hand, the use of a regular hexagonal periodic arrangement can ensure that the structure of the FSS unit has good in-band transmission characteristics and harmonic band suppression characteristics under wide-angle incidence. The use of a double-layer FSS unit structure can achieve a wider transmission bandwidth. Loading a circular hole on the aperture-type FSS unit can introduce a transmission zero point, and adjusting the size of the circular hole can adjust the transmission zero point position and the stopband bandwidth to achieve good suppression in the harmonic band. On the other hand, by designing the FSS unit form, not only the transmission bandwidth of the frequency selective surface structure is improved, but also two transmission zero points are introduced at the harmonic position, so that good isolation is achieved in the harmonic band of the transmission bandwidth. By optimizing the core layer thickness and the stacking arrangement, the frequency selective surface structure has good passband transmission characteristics and harmonic band suppression characteristics at large incident angles.

[0026] Next, we will refer to Figures 1 to 5 The respective parts of the above-mentioned broadband frequency selective surface radome with wide-angle harmonic suppression function in this exemplary embodiment are described in more detail.

[0027] In one embodiment, Figure 2 As shown, the first FSS unit (41) and the second FSS unit (91) are both in the form of an aperture-type regular hexagonal ring loaded with a circular hole, wherein the aperture-type regular hexagonal ring determines the filtering type of the structure to be a bandpass type, the metal strips between adjacent aperture-type regular hexagonal rings can be equivalent to inductors, the gaps inside the aperture-type regular hexagonal rings can be equivalent to capacitors, the inductors and capacitors are in a parallel relationship, thereby forming a two-port parallel capacitor-inductor equivalent circuit, thereby achieving a bandpass characteristic, and the resonant frequency is.

[0028] The two-layer FSS structure and the dielectric layer in between form a second-order bandpass filter, thereby achieving a wider passband bandwidth and a steeper out-of-band cutoff characteristic.

[0029] The circular holes loaded in the first FSS unit (41) and the second FSS unit (91) and the aperture-type regular hexagonal ring form an equivalent circuit in which a capacitor and an inductor are connected in series and then in parallel with the inductor, wherein the capacitor and the inductor connected in series form a transmission zero at the resonance point, and the resonance point is located in the passband twice frequency band, so that a high cutoff characteristic can be achieved in the passband twice frequency band. In the passband, the series capacitor and inductor circuit is a capacitive circuit, so that the inductor connected in parallel forms a bandpass characteristic. The size of the circular hole determines the position of the inserted transmission zero point. In the two FSS layers, circular holes of different sizes are loaded respectively to insert two transmission zero points. The size of the two circular holes can be adjusted to adjust the frequency band and bandwidth of the stopband. The stopband is adjusted to the twice frequency band of the passband by design, so as to achieve the suppression of the second harmonic.

[0030] In one embodiment, Figure 3 As shown, the first FSS unit (41) and the second FSS unit (91) are arranged in a regular hexagon, and this structure has a great advantage in angular stability. When the electromagnetic wave is incident at an azimuth angle of 0-360°, the FSS has extremely stable transmission characteristics. At the same elevation angle, TE and TM polarizations have the same transmission characteristics at different azimuths; when the electromagnetic wave is incident at an elevation angle of 0-45°, the FSS structure has a stable transmission characteristic curve, the passband position and the stopband position move very little, and the passband insertion loss is also very small.

[0031] In one embodiment, the thickness of the first FSS unit (41) and the second FSS unit (91) are both 0.015 mm to 0.020 mm, the diameter of the circular hole of the first FSS unit (41) is 1.05 mm to 1.15 mm, and the diameter of the circular hole of the second FSS unit (91) is 0.85 mm to 0.95 mm.

[0032] In one embodiment, the first skin (1) and the second skin (11) have the same thickness, and both have a thickness of 0.33 mm to 0.66 mm, a relative dielectric constant of 4.2 to 4.4, and a loss tangent of 0.005 to 0.01. The materials of the first skin (1) and the second skin (11) are both cyanate ester or epoxy resin.

[0033] In one embodiment, the core layer (6) has a thickness of 2.3 mm to 2.7 mm, a relative dielectric constant of 1.0 to 1.1, and a loss tangent of 0.001 to 0.005.

[0034] The material of the core layer (6) is PMI foam.

[0035] In one embodiment, the thickness of the first adhesive film (2), the second adhesive film (5), the third adhesive film (7) and the fourth adhesive film (10) are all 0.08 mm to 0.12 mm, and the relative dielectric constants are all 2.8 to 3.2.

[0036] In one embodiment, the thickness of the first dielectric substrate and the second dielectric substrate are both 0.1 mm to 0.15 mm, the relative dielectric constant is 3.0 to 3.3, and the loss tangent is 0.001 to 0.01.

[0037] The materials of the first dielectric base and the second dielectric base are both Rogers RT5880 or polyimide.

[0038] In a specific embodiment, Figure 4 and Figure 5As shown, a transmission characteristic curve of a FSS layer structure working in the Ku band is given through design and optimization. The selected skin material is epoxy glass cloth, with a relative dielectric constant of 4.3 and a loss tangent of 0.008. The core layer (6) material is PMI foam, with a relative dielectric constant of 1.08 and a loss tangent of 0.005. The dielectric substrate material is polyimide, with a relative dielectric constant of 3.2 and a loss tangent of 0.005. The FSS layer is attached to the inner side of the dielectric substrate, and its thickness is 0.018mm copper. The dielectric constant of the film is close to that of polyimide. Through optimization design, when the incident angle of the electromagnetic wave is 0~45°, in the 14GHz~18GHz frequency band, the FSS structure has a passband transmission loss of less than 1dB under TE and TM polarized waves, and in the 28GHz~36GHz frequency band, the structure has good cutoff characteristics.

[0039] Through the above-mentioned broadband frequency selective surface radome with wide-angle harmonic suppression function, on the one hand, the use of a regular hexagonal periodic arrangement can ensure that the structure of the FSS unit has good in-band transmission characteristics and harmonic band suppression characteristics under wide-angle incidence. The use of a double-layer FSS unit structure can achieve a wider transmission bandwidth. Loading a circular hole on the aperture-type FSS unit can introduce a transmission zero point, and adjusting the size of the circular hole can adjust the transmission zero point position and the stopband bandwidth to achieve good suppression in the harmonic band. On the other hand, by designing the FSS unit form, not only the transmission bandwidth of the frequency selective surface structure is improved, but also two transmission zero points are introduced at the harmonic position, so that good isolation is achieved in the harmonic band of the transmission bandwidth. By optimizing the core layer thickness and the stacking arrangement, the frequency selective surface structure has good passband transmission characteristics and harmonic band suppression characteristics at large incident angles.

[0040] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. in the above description indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present disclosure and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present disclosure.

[0041] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0042] In the embodiments of the present disclosure, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0043] In the embodiments of the present disclosure, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes the first feature being directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0044] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0045] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present disclosure are indicated by the appended claims.

Claims

1. A broadband frequency selective surface radome with wide-angle harmonic suppression function, characterized in that: The radome includes: The first skin, the first adhesive film, the first dielectric base, the first FSS layer, the second adhesive film, the core layer, the third adhesive film, the second FSS layer, the second dielectric base, the fourth adhesive film and the second skin are arranged in sequence.

2. The broadband frequency selective surface radome with wide-angle harmonic suppression function according to claim 1, characterized in that: The first FSS layer is composed of a plurality of first FSS units in the form of regular hexagons that are periodically and evenly arranged, and the second FSS layer is composed of a plurality of second FSS units in the form of regular hexagons that are periodically and evenly arranged. Both the first FSS unit and the second FSS unit are in the form of aperture-type regular hexagonal rings loaded with circular holes.

3. The broadband frequency selective surface radome with wide-angle harmonic suppression function according to claim 2, characterized in that: The thickness of the first FSS unit and the second FSS unit are both 0.015 mm to 0.020 mm, the diameter of the circular hole of the first FSS unit is 1.05 mm to 1.15 mm, and the diameter of the circular hole of the second FSS unit is 0.85 mm to 0.95 mm.

4. The broadband frequency selective surface radome with wide-angle harmonic suppression function according to claim 1, characterized in that: The first skin and the second skin have the same thickness, and both are 0.33 mm to 0.66 mm, and both have relative dielectric constants of 4.2 to 4.4 and loss tangents of 0.005 to 0.

01.

5. The broadband frequency selective surface radome with wide-angle harmonic suppression function according to claim 4, characterized in that: The materials of the first skin and the second skin are both cyanate ester or epoxy resin.

6. The broadband frequency selective surface radome with wide-angle harmonic suppression function according to claim 1, characterized in that: The thickness of the core layer is 2.3 mm to 2.7 mm, the relative dielectric constant is 1.0 to 1.1, and the loss tangent is 0.001 to 0.

005.

7. The broadband frequency selective surface radome with wide-angle harmonic suppression function according to claim 6, characterized in that: The material of the core layer is PMI foam.

8. The broadband frequency selective surface radome with wide-angle harmonic suppression function according to claim 1, characterized in that: The thickness of the first adhesive film, the second adhesive film, the third adhesive film and the fourth adhesive film are all 0.08 mm to 0.12 mm, and the relative dielectric constants are all 2.8 to 3.

2.

9. The broadband frequency selective surface radome with wide-angle harmonic suppression function according to claim 1, characterized in that: The thickness of the first dielectric substrate and the second dielectric substrate are both 0.1 mm to 0.15 mm, the relative dielectric constant is 3.0 to 3.3, and the loss tangent is 0.001 to 0.

01.

10. The broadband frequency selective surface radome with wide-angle harmonic suppression function according to claim 9, characterized in that: The materials of the first dielectric substrate and the second dielectric substrate are both Rogers RT5880 or polyimide.

Images