A multi-band omnidirectional matching stealth structure

Abstract

The present invention discloses a multi-band omnidirectional matching stealth structure. From the outside to the inside, the stealth structure comprises a semi-circular cylindrical metal sheet cavity, a semi-cylindrical cavity, a rectangular cylindrical metal sheet cavity, and a triangular cylindrical cavity. The semi-circular cylindrical metal sheet cavity and the rectangular cylindrical metal sheet cavity together form a quadrilateral stealth area, which is used to place the stealthed object. The semi-circular cylindrical metal sheet cavity and the rectangular cylindrical metal sheet cavity are respectively provided with a non-uniform Fabry-Perot resonant cavity array and a uniform Fabry-Perot resonant cavity array. The non-uniform Fabry-Perot resonant cavity array and the uniform Fabry-Perot resonant cavity array are both composed of a plurality of metal sheets arranged at intervals, with dielectric material filled between each metal sheet. Slow light speed material is arranged in the semi-cylindrical cavity and the triangular cylindrical cavity. The present invention has a simple structure, convenient design, matches with free space, has low scattering, can operate in multiple frequency bands, and can be widely used in various military fields such as radar, target stealth, and sensing.

Description

Technical Field

[0001] The present invention belongs to the field of artificial electromagnetic media and relates to a stealth structure, in particular to a multi-band omnidirectional matching stealth structure. Background Art

[0002] Since Pendry et al. proposed a perfect electromagnetic cloaking structure based on transformation optics, designing cloaking structures using artificial electromagnetic materials has become a hot topic among international scientists in this field. From DC to optical wavelengths, covering various frequency bands and adapting to various polarizations, electromagnetic cloaking structures have been proposed and demonstrated experimentally. However, an ideal full-parameter electromagnetic cloaking structure capable of achieving omnidirectional perfect matching in free space has yet to be realized. The fundamental reason is that an omnidirectional perfect matching cloaking structure requires constructing two electromagnetically isolated regions in free space and manipulating the incident electromagnetic wave to propagate around one region to render the other region invisible. From a transformation optics perspective, this involves transforming a point in space into a surface. This transformation inevitably results in extreme (infinite) parameter requirements on the outer surface of the cloaking region. Since the propagation path in the detour region is longer than the straight propagation path in free space, the material in the detour region must be lossless and have a refractive index lower than that of air to maintain amplitude invariance and provide phase compensation. This requires superluminal transparent transmission materials. More importantly, the materials in the detour region must be omnidirectionally matched to free space, resulting in anisotropic and sometimes even spatially non-uniform electromagnetic parameters (varies across space). These stringent requirements, including extreme parameters, superluminal transmission, and omnidirectional perfectly matched transparency, have long hindered the theoretical advancement of perfect stealth structures. The development of the Fabry-Perot resonant cavity has made this material possible. It is typically composed of metal sheets arranged at regular intervals to form a resonant cavity filled with air. When the optical path of a TM-polarized electromagnetic wave within the cavity is an integer multiple of its wavelength, it achieves full transmission, with the transmitted wave maintaining phase alignment with the incident wave. However, this structure generally results in significant scattering. Summary of the Invention

[0003] In order to solve the problems existing in the background technology, the present invention provides a multi-band omnidirectional matching stealth structure.

[0004] The technical solution adopted in the present invention is as follows:

[0005] The stealth structure includes a cylindrical inner cavity with a triangular cross section and a cylindrical outer cavity with a semicircular cross section. The cylindrical inner cavity is located at the center of the stealth structure. Three cylindrical outer cavities are distributed around the outer periphery of the cylindrical inner cavity, and the rectangular side surfaces of the three cylindrical outer cavities respectively coincide with the three rectangular side surfaces of the cylindrical inner cavity.

[0006] Metal sheets are provided in both the cylindrical inner cavity and the cylindrical outer cavity. By reasonably arranging the metal sheets, the reflection of the stealth structure to the transverse magnetic polarization wave is reduced, thereby achieving the stealth effect of the stealth structure in the transverse magnetic polarization wave.

[0007] The cylindrical outer cavity is mainly composed of a semi-cylindrical cavity and a semi-ring cylindrical metal sheet cavity. The semi-cylindrical cavity and the semi-ring cylindrical metal sheet cavity are respectively located on the inner and outer sides of the cylindrical outer cavity. The semi-cylindrical cavity and the semi-ring cylindrical metal sheet cavity are coaxially arranged. The rectangular side of the semi-cylindrical cavity and the rectangular side of the semi-ring cylindrical metal sheet cavity are on the same plane. The arc side of the semi-cylindrical cavity and the inner arc side of the semi-ring cylindrical metal sheet cavity coincide with each other. A non-uniform Fabry-Perot resonant cavity array is arranged in the semi-ring cylindrical metal sheet cavity.

[0008] The columnar inner cavity includes a triangular columnar cavity, a rectangular columnar metal sheet cavity and an invisible area. The triangular columnar cavity is located at the center of the columnar inner cavity. The triangular columnar cavity and the columnar inner cavity are coaxially arranged, and the three rectangular sides of the triangular columnar cavity are respectively parallel to the three rectangular sides of the columnar inner cavity. Three rectangular columnar metal sheet cavities are distributed around the outer periphery of the triangular columnar cavity, and one side of the three rectangular columnar metal sheet cavities coincides with the three rectangular sides of the triangular columnar cavity, and the other side of the three rectangular columnar metal sheet cavities coincides with the rectangular sides of the three semi-cylindrical cavities; the invisible area is the area in the columnar inner cavity except the triangular columnar cavity and the rectangular columnar metal sheet cavity; a uniform Fabry-Perot resonant cavity array is arranged in the rectangular columnar metal sheet cavity.

[0009] The non-uniform Fabry-Perot resonant cavity array is mainly formed by a plurality of metal sheets uniformly spaced along the circumference of a semi-cylindrical cavity. The width direction of the metal sheets in the non-uniform Fabry-Perot resonant cavity array is parallel to the radial direction of the semi-cylindrical cavity, and the length direction is parallel to the axial direction of the semi-cylindrical cavity. A first dielectric material and air are provided between two adjacent metal sheets in the semi-cylindrical metal sheet cavity.

[0010] The uniform Fabry-Perot resonant cavity array is mainly formed by a plurality of metal sheets arranged at intervals along the circumference of a triangular cylindrical cavity. The width direction of the metal sheets of the uniform Fabry-Perot resonant cavity array is perpendicular to the circumference of the triangular cylindrical cavity, and the length direction is parallel to the axial direction of the triangular cylindrical cavity. A first dielectric material is arranged between adjacent metal sheets in the rectangular cylindrical metal sheet cavity.

[0011] The invisible area is provided with invisible objects.

[0012] The semi-cylindrical cavity and the triangular column cavity are both filled with a second dielectric material, and the second dielectric material is a Rogers dielectric plate or a polytetrafluoroethylene dielectric plate.

[0013] The metal sheet is made of a metal material with an electrical conductivity greater than 100.

[0014] The first dielectric material is a non-magnetic material, and the non-magnetic material is a Teflon sheet or a Rogers sheet.

[0015] The columnar inner cavity and the triangular column cavity are both equilateral triangle structures.

[0016] A Fabry-Perot resonator is primarily composed of two metal sheets. When the two metal sheets are parallel, the structure is called a uniform Fabry-Perot resonator. When the two metal sheets are not parallel, the structure is called an inhomogeneous Fabry-Perot resonator. Multiple Fabry-Perot resonators together form a Fabry-Perot resonator array.

[0017] The omnidirectional matching stealth structure can achieve omnidirectional matching stealth at a specific frequency of TM wave, such as Figure 1 As shown in Figure (a), the present invention has a cloverleaf shape, with a semi-circular cylindrical metal sheet cavity, a semi-circular cylindrical cavity, a rectangular cylindrical metal sheet cavity, and a triangular cylindrical cavity from the outside to the inside. The semi-circular cylindrical metal sheet cavity and the rectangular cylindrical metal sheet cavity together form a quadrilateral stealth area. TM waves incident from all sides of the cylindrical structure, which omnidirectionally matches the overall stealth structure, can completely penetrate the structure.

[0018] The outermost layer is constructed using metal sheets to create a non-uniform Fabry-Perot resonant cavity array. The cavities are filled with a dielectric of varying thickness to achieve a gradually varying effective dielectric constant. This reduces scattering caused by the Fabry-Perot resonant cavity when TM-polarized waves are introduced. The semi-cylindrical and triangular prism cavities are filled with slow-light materials to compensate for phase shifts. A uniform Fabry-Perot resonant cavity connects the semi-cylindrical and triangular prism cavities. The non-uniform and uniform Fabry-Perot resonant cavity arrays together form a quadrilateral cloaking zone. Any object placed within the cloaking zone remains undetectable, and the structure itself remains undetectable when exposed to TM-polarized electromagnetic waves of a specific frequency, thus achieving omnidirectional matched cloaking.

[0019] The beneficial effects of the present invention are:

[0020] 1. This invention achieves omnidirectional matching stealth in free space. While maintaining its own stealth, any object placed within the quadrilateral columnar stealth area remains undetectable. Furthermore, because the equivalent dielectric constant within the non-uniform Fabry-Perot resonant cavity is inversely proportional to its radius, it can reduce scattering caused by the Fabry-Perot resonant cavity.

[0021] 2. The present invention has a simple structure, convenient design, matches with free space, has small scattering, can operate in multiple frequency bands, and can be widely used in various military fields such as radar, target stealth and sensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 (a) is a plan view of the structure of the present invention; Figure 1 (b) is a detailed diagram of the non-uniform Fabry-Perot resonant cavity in the structure of the present invention;

[0023] Figure 2 (a) Schematic diagram of the uniform Fabry-Perot resonant cavity structure; Figure 2 (b) is a schematic diagram of the non-uniform Fabry-Perot resonant cavity structure;

[0024] Figure 3 (a) is a schematic diagram of free space; Figure 3 (b) is a schematic diagram of coordinate changes;

[0025] Figure 4 (a) is a simulation diagram of the present invention at 5 GHz; Figure 4 (b) is a simulation diagram of the present invention at 10 GHz;

[0026] Figure 5 (a) is a radar cross-sectional area diagram of the stealth structure of the present invention and the comparative experiment at 5 GHz; Figure 5 (b) is a radar cross-sectional area diagram of the stealth structure of the present invention and the comparative experiment at 10 GHz. DETAILED DESCRIPTION

[0027] The technical solutions of the present invention are described clearly and completely below with reference to the embodiments. It is obvious that the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] like Figure 1 As shown in (a), the stealth structure includes a cylindrical inner cavity with a triangular cross section and a cylindrical outer cavity with a semicircular cross section. The cylindrical inner cavity is located at the center of the stealth structure. Three cylindrical outer cavities are distributed around the outer periphery of the cylindrical inner cavity, and the rectangular side surfaces of the three cylindrical outer cavities respectively coincide with the three rectangular side surfaces of the cylindrical inner cavity.

[0029] In the outer surface of the cylindrical outer cavity, the rectangular plane parallel to the axial direction of the cylindrical outer cavity is the rectangular side surface of the cylindrical outer cavity; in the outer surface of the cylindrical inner cavity, the rectangular plane parallel to the axial direction of the cylindrical inner cavity is the rectangular side surface of the cylindrical inner cavity.

[0030] Metal sheets are provided in both the cylindrical inner cavity and the cylindrical outer cavity. By reasonably arranging the metal sheets, the reflection of the stealth structure to the transverse magnetic polarization wave (i.e., TM polarization wave) is reduced, thereby achieving the stealth effect of the stealth structure in the transverse magnetic polarization wave.

[0031] The cylindrical outer cavity is mainly composed of a semi-cylindrical cavity and a semi-ring cylindrical metal sheet cavity. The semi-cylindrical cavity and the semi-ring cylindrical metal sheet cavity are respectively located on the inner and outer sides of the cylindrical outer cavity. The semi-cylindrical cavity and the semi-ring cylindrical metal sheet cavity are coaxially arranged. The rectangular side of the semi-cylindrical cavity and the rectangular side of the semi-ring cylindrical metal sheet cavity are on the same plane. The arc side of the semi-cylindrical cavity and the inner arc side of the semi-ring cylindrical metal sheet cavity coincide with each other. A non-uniform Fabry-Perot resonant cavity array is arranged in the semi-ring cylindrical metal sheet cavity.

[0032] On the outer surface of the semi-cylindrical cavity, the rectangular plane parallel to the semi-cylindrical cavity's axis is the rectangular side surface of the semi-cylindrical cavity; on the side surface of the semi-cylindrical cavity, the curved surface is the arcuate side surface; the rectangular side surface of the semi-cylindrical cavity and the arcuate side surface of the semi-cylindrical cavity together constitute the side surface of the semi-cylindrical cavity. On the outer surface of the semi-annular cylindrical metal sheet cavity, the rectangular plane parallel to the semi-annular cylindrical metal sheet cavity's axis is the rectangular side surface of the semi-cylindrical cavity; on the side surface of the semi-annular cylindrical metal sheet cavity, the curved surface closest to the cylindrical inner cavity is the inner arcuate side surface.

[0033] The columnar inner cavity includes a triangular columnar cavity, a rectangular columnar metal sheet cavity and an invisible area. The triangular columnar cavity is located at the center of the columnar inner cavity. The triangular columnar cavity and the columnar inner cavity are coaxially arranged, and the three rectangular sides of the triangular columnar cavity are respectively parallel to the three rectangular sides of the columnar inner cavity. The triangular columnar cavity is a triangular columnar structure obtained by scaling the columnar inner cavity according to a certain proportion. Three rectangular columnar metal sheet cavities are distributed around the outer periphery of the triangular columnar cavity, and one side of the three rectangular columnar metal sheet cavities respectively coincides with the three rectangular sides of the triangular columnar cavity, and the other side of the three rectangular columnar metal sheet cavities respectively coincides with the rectangular sides of the three semi-cylindrical cavities; the invisible area is the area in the columnar inner cavity except the triangular columnar cavity and the rectangular columnar metal sheet cavity; a uniform Fabry-Perot resonant cavity array is arranged in the rectangular columnar metal sheet cavity.

[0034] In the outer surface of the triangular cylindrical cavity, the rectangular plane parallel to the axial direction of the triangular cylindrical cavity is the rectangular side surface of the triangular cylindrical cavity; in the outer surface of the rectangular cylindrical metal sheet cavity, the rectangular plane parallel to the axial direction of the rectangular cylindrical metal sheet cavity is the side surface of the rectangular cylindrical metal sheet cavity.

[0035] Specifically, the rectangular cylindrical metal sheet cavity is located between the semi-cylindrical cavity and the triangular cylindrical cavity. The two adjacent rectangular cylindrical metal sheet cavities and the two adjacent semi-circular cylindrical metal sheet cavities together form an invisible area. The four sides of the invisible area respectively coincide with a rectangular side surface of the two semi-circular cylindrical metal sheet cavities and a rectangular side surface of the two rectangular cylindrical metal sheet cavities.

[0036] like Figure 1As shown in (b) and 2(b), the non-uniform Fabry-Perot resonant cavity array is mainly formed by a plurality of metal sheets uniformly spaced along the circumference of a semi-cylindrical cavity. The width direction of the metal sheets in the non-uniform Fabry-Perot resonant cavity array is parallel to the radial direction of the semi-cylindrical cavity, and the length direction is parallel to the axial direction of the semi-cylindrical cavity. That is, each metal sheet in the non-uniform Fabry-Perot resonant cavity array is arranged along the radial direction of the semi-cylindrical cavity, and the metal sheet extends along the axial direction of the semi-circular cylindrical metal sheet cavity. A first dielectric material and air are arranged between two adjacent metal sheets in the semi-circular cylindrical metal sheet cavity. The first dielectric material and the air are arranged in layers, and the arrangement order is metal sheet, first dielectric material, air, and next metal sheet.

[0037] like Figure 2 As shown in (a), the uniform Fabry-Perot resonant cavity array is mainly formed by a plurality of metal sheets arranged at intervals along the circumference of a triangular cylindrical cavity. The width direction of the metal sheets of the uniform Fabry-Perot resonant cavity array is perpendicular to the circumference of the triangular cylindrical cavity, and the length direction is parallel to the axial direction of the triangular cylindrical cavity. That is, each metal sheet in the uniform Fabry-Perot resonant cavity array is arranged along a direction perpendicular to the circumference of the triangular cylindrical cavity, and the metal sheet extends along the axial direction of the rectangular cylindrical metal sheet cavity. A first dielectric material is arranged between adjacent metal sheets in the rectangular cylindrical metal sheet cavity.

[0038] The circumference of the triangular cylindrical cavity is the direction of the side length of the triangular cylindrical cavity's end face. Specifically, the end face in the present invention refers to the face of the cylindrical structure perpendicular to the structure's own axis, the rectangular side face refers to the face of the cylindrical structure parallel to the structure's own axis, and the arcuate side face refers to the face of the cylindrical structure formed by rotating around the structure's own axis. The cylindrical structure includes semi-circular cylindrical metal sheet cavities, semi-cylindrical cavities, rectangular cylindrical metal sheet cavities, triangular cylindrical cavities, cylindrical inner cavities, and cylindrical outer cavities.

[0039] The invisible area is filled with air, and any material placed in it will remain undetected.

[0040] The semi-cylindrical cavity and the triangular column cavity are both filled with a second dielectric material. The second dielectric material is a Rogers dielectric plate or a polytetrafluoroethylene dielectric plate, but is not limited thereto.

[0041] The second dielectric material (slow light material) is stacked by ordinary dielectric materials. The second dielectric material is any ordinary dielectric material whose refractive index at the working frequency is greater than the refractive index of the surrounding environment. It only needs to satisfy that the optical path of the wave in the semi-cylindrical cavity and the triangular cylindrical cavity is equal to the optical path of the wave in the clover stealth structure in free space.

[0042] The metal sheet is a metal material with an electrical conductivity greater than 100.

[0043] The first dielectric material is a low-loss non-magnetic material, and the non-magnetic material is a Teflon sheet or a Rogers sheet.

[0044] Both the columnar inner cavity and the triangular column cavity are equilateral triangle structures.

[0045] The non-uniform Fabry-Perot resonator array is a semicircular cylindrical cavity structure formed by multiple metal plates arranged at a fixed angle to each other. The gaps between the metal plates change with the radius. The gaps are filled with a dielectric material of varying thickness and air, making the equivalent electrical parameters within the cavity inversely proportional to the radius, thereby reducing scattering of the stealth structure.

[0046] A non-uniform Fabry-Perot resonator (resonator) consists of air and a dielectric material with a gradient thickness. When the resonator gap is less than one-tenth the wavelength of a transverse magnetic (TM) polarized wave, the air and the dielectric material can be considered a metamaterial. The metamaterial's effective dielectric constant varies with the ratio of the dielectric material thickness to the resonator thickness, making the refractive index inversely proportional to the radius, thereby reducing scattering caused by the resonator. After entering the resonator through an omnidirectional matching stealth structure, the TM polarized wave travels an optical path in each resonator equal to an integer multiple of the operating wavelength, ensuring that the phase of the TM polarized wave on the outer and inner cylindrical surfaces of the non-uniform Fabry-Perot resonator array remains consistent.

[0047] A uniform Fabry-Perot resonator array is primarily constructed from metal sheets spaced evenly apart. The thickness of the filler material within the resonator is equal to the spacing between the sheets. This ensures that the optical path traveled by the wave in the resonator is an integer multiple of the operating wavelength. The operating wavelength of an omnidirectionally matched stealth structure is the inverse of the operating frequency.

[0048] After the TM polarized wave is incident on the resonant cavity, the optical path it travels in each resonant cavity is equal to an integer multiple of the working wavelength. At this time, the incident wave and the outgoing wave are in phase, achieving full transmission.

[0049] The materials filled in the non-uniform Fabry-Perot resonant cavity array are as follows: Figure 1 As shown in (b), the thickness of the filled material changes with the radius, and the change curve is as follows Figure 1 (b) shows the equivalent dielectric constant of the filling material being inversely proportional to the radius. A uniform Fabry-Perot resonator array is filled with dielectric material. A TM wave at the operating frequency is incident on the omnidirectionally matched stealth structure and then enters the resonant cavity. The optical path traveled in each resonant cavity is an integer multiple of the operating wavelength.

[0050] In a specific implementation, the dielectric material and the metal sheet are fixed by setting components or fixed ends on both end faces of the overall columnar structure of the omnidirectional matching stealth structure.

[0051] The working principle of the present invention is:

[0052] According to the principle of transformation optics, the circular area in free space, such as Figure 3 As shown in (a), it is compressed to a smaller circular area II, as shown in Figure 3 As shown in (b), the black wireframe is stretched into region I. At this time, region I adopts the cylindrical coordinate system. The inner radius of region I is ρ1, and the outer radius is ρ2 = 2ρ1. Region I can guide the TM polarized electromagnetic wave along the ρ direction to the inner region (region II) without any phase accumulation. At this time, the ideal electrical parameters of region I are μ z =0, ε ρ =∞. However, this extremely exotic property is difficult to achieve in reality. For this reason, we can consider the Fabry-Perot resonant medium, that is, when the wavelength of the wave along the propagation path is equal to an integer multiple of the working wavelength, the Fabry-Perot resonant medium can achieve full transmission. However, for a general Fabry-Perot resonant medium, its internal dielectric constant remains unchanged at a fixed value, which will cause a certain amount of scattering. In order to reduce scattering, we fill the Fabry-Perot resonant medium with a material of gradient thickness so that its equivalent dielectric constant is inversely proportional to the radius. At this time, the equivalent electrical parameter of region I can be expressed as μ z =1, ε ρ =∞, where a(ρ) = A / ρ and A is a constant. The inner radius of the non-uniform Fabry-Perot medium is ρ1 and the outer radius is ρ2, and its equivalent dielectric constant is The above conditions can be expressed as:

[0053]

[0054]

[0055] Where k represents the wavelength of the wave traveling k times in the Fabry-Perot medium. Substituting formula (1) into formula (2), we can obtain:

[0056]

[0057] In addition, since the path of the TM wave in region II is shorter than the circular region before transformation in free space (i.e. Figure 3 (a)) The path traveled by the wave is short. To ensure phase consistency, region II needs to be filled with a slow-light material, that is, a material with a refractive index greater than that of the surrounding environment, so that the optical path traveled by the wave in the material is the same as the optical path traveled by the wave in the circular region in free space. Their electrical parameters can be expressed as μ z =1,ε u =ε v =(ρ2 / ρ1) 2 .

[0058] In practice, in order to realize the Fabry-Perot medium, a periodic array structure of metal slits is usually used, which can support the propagation of surface plasmons. Figure 2 (a) and Figure 2 As shown in (b), for a uniform Fabry-Perot resonant cavity, the cavity spacing is D and the interior is filled with a dielectric (dielectric constant is ε1). Here λ>>D, λ represents the operating wavelength

[0059] For the inhomogeneous Fabry-Perot resonant cavity, the cavity spacing is D ρ , the interior is filled with air (dielectric constant is ε0) and thickness is d ρ The dielectric constant is ε1. for:

[0060]

[0061] Based on the above theory, we designed Figure 1 (a) The invisible structure shown. The details of the non-uniform Fabry-Perot resonant cavity are shown in Figure 1 As shown in (b), assuming that the inner and outer radii are ρ1 and ρ2 respectively, and the angle between the two metal plates is θ, then the cavity gap D ρ It can be expressed as

[0062]

[0063] Therefore, substituting (5) into (4) yields the thickness d of the filling material in the non-uniform Fabry-Perot resonant cavity: ρ for

[0064]

[0065] These non-uniform Fabry-Perot resonant cavities can transform the field on the edge of the clover-shaped cylindrical cavity to a semicircle without causing phase change. For a uniform Fabry-Perot resonant cavity, its length is l and it is filled with a dielectric (with a dielectric constant of ε1). When it satisfies the Fabry-Perot resonance condition, it has:

[0066]

[0067] The triangular cylindrical cavity and the semi-cylindrical cavity are filled with full-speed-of-light material to supplement the phase. Therefore, the designed structure can achieve omnidirectional matching stealth.

[0068] Specific embodiment: The cross-sectional structure of the cylinder of the present invention is as follows Figure 1As shown in (a), it is mainly composed of three areas: a non-uniform Fabry-Perot resonator array, a uniform Fabry-Perot resonator array, and a triangular cylindrical cavity and a semi-cylindrical cavity filled with light-speed material. Each non-uniform Fabry-Perot resonator array is composed of 90 pieces of metal materials with different thicknesses (dielectric constant 6.15, loss tangent 0.0038). The material is copper-clad on one side, and the copper foil thickness is 0.035mm. Each piece of material is fan-shaped with an angle of 2 degrees between each other. The radius in the fan-shaped area is ρ1 = 21.57mm, and the outer radius is ρ2 = 42.53mm. Substituting it into formula (6), the material thickness curve is as follows Figure 1 As shown in (b), the gap between the metal sheets changes from 0.69mm to 0.13mm, and the gap between the metal sheets changes from 0.75mm to 1.48mm. Therefore, its equivalent dielectric constant changes from 4.20 to 1.08. The length and height of the materials are 20.96mm and 200mm, respectively. The uniform Fabry-Perot resonator array is composed of 52 pieces of metal material with a thickness of 0.81mm, and the length and height of the materials are 12.10mm and 200mm, respectively. The material is copper-clad on both sides, and the copper foil thickness is 0.018mm. The optical path traveled by the wave in the uniform and non-uniform Fabry-Perot resonator arrays is 30mm. Therefore, this omnidirectional stealth structure can operate in frequency bands such as 5GHz, 10GHz, and 15GHz. The side length of the triangular cylindrical cavity is 43.16mm, and the radius of the semi-cylindrical cavity is 21.58mm. The cavity is filled with F4B material (dielectric constant 3.88, loss tangent 0.002) with a thickness of 5 mm. The triangular cylindrical cavity and the semi-cylindrical cavity are filled by continuous stacking.

[0069] According to the above embodiment, the omnidirectional stealth effect under the point source condition is obtained by simulation using the simulation component. Figure 4 (a) and Figure 4 (b), where Figure 4 (a) is the field distribution at 5 GHz. Figure 4 (b) is the field pattern distribution at 10 GHz. From the results, we can see that the stealth structure of the present invention can achieve omnidirectional matching stealth in multiple frequency bands and can reduce the scattering caused by the Fabry-Perot resonant cavity.

[0070] In order to quantitatively describe the effect of the stealth structure, we used simulation software to obtain the radar cross-sectional area diagram, such as Figure 5 (a) and Figure 5 As shown in (b), the comparative experiment is the case where a metal column is placed in the invisible area. Figure 5 (a) is a comparison of the radar cross-sectional area of ​​the 5GHz stealth structure and the comparative experiment. Figure 5(b) is a comparison of the radar cross-sections of the stealth structure and the comparative experiment at 10 GHz. The results show that for metallic media, the metal pillars cause significant scattering, but the addition of the stealth structure significantly suppresses the scattering.

[0071] The above examples do not limit the present invention in any form. Any technician familiar with the profession can use the technical content disclosed above to change or modify it into equivalent examples with equivalent changes. However, any simple modifications, equivalent changes and modifications made to the above examples based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A multi-band omnidirectional matching stealth structure, characterized by: The stealth structure includes a cylindrical inner cavity with a triangular cross section and a cylindrical outer cavity with a semicircular cross section. The cylindrical inner cavity is located at the center of the stealth structure. Three cylindrical outer cavities are distributed around the outer periphery of the cylindrical inner cavity, and the rectangular side surfaces of the three cylindrical outer cavities respectively coincide with the three rectangular side surfaces of the cylindrical inner cavity. Metal sheets are provided in both the cylindrical inner cavity and the cylindrical outer cavity. By rationally arranging the metal sheets, the reflection of the stealth structure on the transverse magnetic polarization wave is reduced, thereby achieving the stealth effect of the stealth structure in the transverse magnetic polarization wave. The cylindrical outer cavity is mainly composed of a semi-cylindrical cavity and a semi-ring cylindrical metal sheet cavity. The semi-cylindrical cavity and the semi-ring cylindrical metal sheet cavity are respectively located on the inner and outer sides of the cylindrical outer cavity. The semi-cylindrical cavity and the semi-ring cylindrical metal sheet cavity are coaxially arranged. The rectangular side of the semi-cylindrical cavity and the rectangular side of the semi-ring cylindrical metal sheet cavity are on the same plane. The arcuate side of the semi-cylindrical cavity and the inner arcuate side of the semi-ring cylindrical metal sheet cavity coincide with each other. A non-uniform Fabry-Perot resonant cavity array is provided in the semi-circular cylindrical metal sheet cavity; The cylindrical inner cavity includes a triangular cylindrical cavity, a rectangular cylindrical metal sheet cavity and an invisible area. The triangular cylindrical cavity is located at the center of the cylindrical inner cavity. The triangular cylindrical cavity and the cylindrical inner cavity are coaxially arranged, and the three rectangular sides of the triangular cylindrical cavity are respectively parallel to the three rectangular sides of the cylindrical inner cavity. Three rectangular cylindrical metal sheet cavities are distributed around the outer periphery of the triangular cylindrical cavity, and one side of the three rectangular cylindrical metal sheet cavities respectively coincides with the three rectangular sides of the triangular cylindrical cavity, and the other side of the three rectangular cylindrical metal sheet cavities respectively coincides with the rectangular sides of the three semi-cylindrical cavities; the invisible area is the area in the cylindrical inner cavity excluding the triangular cylindrical cavity and the rectangular cylindrical metal sheet cavity; a uniform Fabry-Perot resonant cavity array is arranged in the rectangular cylindrical metal sheet cavity; The non-uniform Fabry-Perot resonant cavity array is mainly formed by a plurality of metal sheets uniformly spaced along the circumference of a semi-cylindrical cavity. The width direction of the metal sheets in the non-uniform Fabry-Perot resonant cavity array is parallel to the radial direction of the semi-cylindrical cavity, and the length direction is parallel to the axial direction of the semi-cylindrical cavity. A first dielectric material and air are provided between two adjacent metal sheets in the semi-cylindrical metal sheet cavity. The uniform Fabry-Perot resonant cavity array is mainly formed by a plurality of metal sheets arranged at intervals along the circumference of a triangular cylindrical cavity. The width direction of the metal sheets of the uniform Fabry-Perot resonant cavity array is perpendicular to the circumference of the triangular cylindrical cavity, and the length direction is parallel to the axial direction of the triangular cylindrical cavity. A first dielectric material is arranged between adjacent metal sheets in the rectangular cylindrical metal sheet cavity.

2. The multi-band omnidirectional matching stealth structure according to claim 1, characterized in that: The invisible area is filled with invisible objects.

3. The multi-band omnidirectional matching stealth structure according to claim 1, characterized in that: The semi-cylindrical cavity and the triangular column cavity are both filled with a second dielectric material, and the second dielectric material is a Rogers dielectric plate or a polytetrafluoroethylene dielectric plate.

4. The multi-band omnidirectional matching stealth structure according to claim 1, characterized in that: The metal sheet is made of a metal material with an electrical conductivity greater than 100.

5. The multi-band omnidirectional matching stealth structure according to claim 1, characterized in that: The first dielectric material is a non-magnetic material, and the non-magnetic material is a Teflon sheet or a Rogers sheet.

6. The multi-band omnidirectional matching stealth structure according to claim 1, characterized in that: The columnar inner cavity and the triangular column cavity are both equilateral triangle structures.

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