A broadband radome based on impedance tapering and a broadband wave-transparent optimization method

Abstract

The application discloses a kind of wideband radome based on impedance gradual change and wideband wave-transparent optimization method, include: several honeycomb core structure units, and the honeycomb core structure unit is arranged in honeycomb array;The cross section of each honeycomb core structure unit is hexagonal, and inside hollow;The wall thickness of each honeycomb core structure unit is linearly changed between its upper surface and lower surface along the direction of electromagnetic wave vertical incidence.The application obtains the wideband radome with good impedance matching characteristics by designing the honeycomb core structure unit and selecting the matrix material, which can solve the problems of wideband wave-transparent, bearing and performance stability that the traditional half-wave wall dielectric radome cannot meet.

Description

Technical Field

[0001] This invention relates to the field of radomes, and in particular to a broadband radome based on impedance gradient and a broadband transmission optimization method. Background Technology

[0002] The radome, located at the front of the aircraft, protects the internal antenna system, ensuring normal communication under harsh environmental conditions. Therefore, the radome must possess load-bearing, protective, and communication capabilities. As the radar communication bandwidth of aircraft continues to expand, the operating bandwidth of radar antennas also increases, requiring the radome to also have broadband wave transmission performance. Half-wavewall dielectric radomes are insufficient to meet the broadband wave transmission requirements of broadband communication technology. New broadband wave transmission radomes are achieved through sandwich structures or frequency-selective surface structures; however, the multi-layered combination and its manufacturing process significantly reduce the performance stability and reliability of the radome. Therefore, it is necessary to develop a new type of radome that meets the application requirements of broadband wave transmission, load-bearing capacity, and stable and reliable performance. Summary of the Invention

[0003] The purpose of this invention is to provide a broadband radome based on impedance gradient and a broadband transmission optimization method to overcome the problems of poor broadband transmission performance, unstable performance, and poor load-bearing capacity in existing broadband radome technologies, and to meet the broadband transmission requirements of radomes in broadband communication technology.

[0004] To achieve the above objectives, the present invention provides a broadband radome based on impedance gradient, comprising: a plurality of honeycomb core structure units arranged in a honeycomb array; each honeycomb core structure unit has a hexagonal cross-section and is hollow inside; the wall thickness of each honeycomb core structure unit varies linearly between its upper and lower surfaces with respect to the perpendicular incident direction of the electromagnetic wave.

[0005] Optionally, the wall thickness of each of the honeycomb core structural units increases linearly from its upper surface to the intermediate layer between the upper and lower surfaces, and decreases linearly from the intermediate layer to the lower surface.

[0006] Optionally, the intermediate layer is located at half the height of the honeycomb core structure unit; the linear change in the wall thickness of the honeycomb core structure unit is symmetrical and linear, with the intermediate layer as the boundary.

[0007] Optionally, the honeycomb core structure unit may be made of Si3N4 ceramic.

[0008] This invention also provides a method for optimizing the wave transmission of a broadband radome, comprising the following steps:

[0009] Step S1: Based on the linear variation law of the wall thickness of the honeycomb core structure unit, obtain the linear variation function of the wall thickness;

[0010] Step S2: Based on the calculation formula of the equivalent dielectric constant of the cellular core structure unit, and combined with the linear variation function of the wall thickness, the function ε of the equivalent dielectric constant of the broadband radome as a function of the vertical incident height is obtained. r_eff (z);

[0011] Step S3: Based on the formula for calculating intrinsic impedance, combined with ε from step S2... r_eff (z) is used to obtain the intrinsic impedance of the broadband radome as a function of the vertical incident height.

[0012] Step S4: Based on the intrinsic impedance obtained in step S3 and the characteristic of continuous change of intrinsic impedance, calculate the input impedance of the broadband radome.

[0013] Step S5: By iteratively calculating the input impedance in step S4, the transmittance T of the broadband radome at the vertical incident height is obtained.

[0014] Optionally, in step S2 of the broadband radome's wave transmission optimization method, the equivalent dielectric constant of the broadband radome varies as a function ε with the vertical incident height. r_eff (z) is:

[0015]

[0016] In the formula, ε r It is the relative permittivity of the matrix material. s is the fill factor. t (z) represents the wall thickness of the honeycomb core structure unit, which varies linearly with the vertical incident height z. t denoted as the side length of the honeycomb core structure unit.

[0017] Optionally, in step S3 of the broadband radome transmission optimization method, the intrinsic impedance of the broadband radome varying with the vertical incident height is:

[0018]

[0019] In the formula, Z0 represents the free-space wave impedance, μ r This indicates the relative permeability of the radome material.

[0020] Optionally, in step S4 of the broadband radome transmission optimization method, the input impedance of the broadband radome is:

[0021]

[0022] In the formula, j is the imaginary unit, c represents the speed of light, f represents the frequency of the incident wave, and n represents the number of iterations; Δz t =H t / N t To divide the impedance-gradient broadband radome into N sections along the z-direction t The height of each subsequent iteration layer; Z t_in(n) This represents the input impedance of the nth layer of the broadband radome.

[0023] Optionally, in step S5 of the broadband radome transmission optimization method, the transmittance T of the broadband radome at the vertical incident height is:

[0024]

[0025] In the formula, This indicates that the broadband radome is divided into N sections along the z-axis. t The theoretical value of the input impedance after the layer.

[0026] Optionally, the method for optimizing the wave transmission of the broadband radome is as follows: the smaller the relative permittivity of the matrix material of the honeycomb core structure unit and the larger the height of the honeycomb core structure unit, the better the wave transmission performance of the broadband radome. The change in wall thickness plays a fine-tuning role in the wave transmission performance of the radome.

[0027] In summary, compared with the prior art, the broadband radome and broadband transmission optimization method based on impedance gradient provided by the present invention have the following beneficial effects:

[0028] 1. The impedance-gradient broadband radome of the present invention improves the electrical continuity of the interface between the thin-walled structure and the gradient structure by using the impedance-gradient structure in the design of the broadband radome. This ensures the continuous transmission of electromagnetic waves in a wide frequency range, thereby achieving broadband wave transmission.

[0029] 2. The broadband radome based on impedance gradient of the present invention overcomes the limitations of broadband transmission impedance matching of low dielectric thin-walled structures and sandwich structures through the synergistic optimization of substrate materials and structural parameters. Compared with the single-factor control of material electromagnetic parameters and structural unit parameters, it realizes continuous variation of intrinsic wave impedance over a larger range.

[0030] 3. The broadband radome based on impedance gradient of the present invention achieves adjustable frequency ratio of the center frequency of the transparent band and high degree of control by adjusting the geometric dimensions of the impedance gradient honeycomb core structure unit.

[0031] 4. The broadband radome based on impedance gradient of the present invention has excellent characteristics such as certain load-bearing capacity and lightweight. Its overall structure is integrally formed, and its structure and performance stability are high. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a three-dimensional structure of a broadband antenna radome unit based on impedance gradient according to the present invention.

[0033] Figure 2 This is the result of the theoretical calculation of the intrinsic impedance of a broadband radome based on impedance gradient according to the present invention;

[0034] Figure 3 This is a simulation result of the broadband transmittance of a broadband radome based on impedance gradient according to the present invention.

[0035] Figure 4 The simulation results of the transmittance of the broadband antenna radome of the present invention under different dielectric constants of the substrate materials are shown.

[0036] Figure 5 The simulation results of the transmittance of the broadband antenna radome of the present invention under different impedance-gradient honeycomb core structure heights are shown.

[0037] Figure 6 The transmittance simulation results of the broadband radome of the present invention under different impedance gradient honeycomb core structure surface wall thicknesses are shown.

[0038] Figure 7 The transmission rate simulation results of the broadband antenna radome of the present invention are shown for the intermediate layer wall thickness of the honeycomb core structure with different impedance gradients. Detailed Implementation

[0039] The following will be combined with the appendix Figures 1-7 The technical content, structural features, objectives and effects of the present invention will be described in detail through preferred embodiments.

[0040] It should be noted that the accompanying drawings are in a very simplified form and use non-precise proportions. They are only used to facilitate and clarify the purpose of illustrating the embodiments of the present invention, and are not intended to limit the implementation conditions of the present invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationship, or adjustments to the size should still fall within the scope of the technical content disclosed in the present invention, provided that they do not affect the effects and objectives that the present invention can produce.

[0041] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0042] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0043] like Figure 1 As shown, this invention provides a broadband radome based on impedance gradient. The broadband radome comprises several honeycomb core structural units arranged in a honeycomb array. Each honeycomb core structural unit has a regular hexagonal cross-section and is hollow inside. The wall thickness of the honeycomb core structural unit varies linearly in the vertical incident direction, increasing first and then decreasing from top to bottom. That is, the honeycomb core structural unit is thinner at both ends and thicker in the middle in the vertical incident direction. The vertical incident direction refers to the direction of electromagnetic wave incidence after entering the broadband radome.

[0044] Wherein, the side length of the regular hexagon of each of the honeycomb core structural units is r. t The height of the honeycomb core structure unit is H t The wall thickness of the honeycomb core structure unit is s. t Specifically, the wall thickness s of the aforementioned honeycomb core structure unit... t Including the wall thickness s of the upper (lower) surface tu The wall thickness of the intermediate layer is s td The upper and lower surfaces represent the thinnest points of the honeycomb core structure unit's wall thickness in its cross-section, while the middle layer represents the thickest point, located at half the height of the entire honeycomb core structure unit. Therefore, the linear variation in the wall thickness of the honeycomb core structure unit is symmetrical and linear, with the middle layer as the boundary.

[0045] The honeycomb core structure unit has a certain load-bearing capacity due to its regular hexagonal structure; and the hollow internal structure of the honeycomb core structure unit makes the broadband radome based on the impedance gradient honeycomb core structure lightweight.

[0046] The broadband radome based on impedance gradient has structural parameters that vary linearly with the vertical incident height z. These linearly varying structural parameters affect the impedance characteristics of the broadband radome, and consequently, the matching characteristics with the boundary conditions for electromagnetic wave propagation.

[0047] The impedance characteristics mentioned above include input impedance and intrinsic impedance. When the input impedance matches the free-space wave impedance, the reflection of incident electromagnetic waves on the surface of the broadband radome is reduced, meaning that electromagnetic waves incident on the surface of the broadband radome can enter the interior of the broadband radome to the greatest extent. The intrinsic impedance characteristics reflect the ability of electromagnetic waves to propagate inside the broadband radome. When the intrinsic impedance of the broadband radome changes continuously, electromagnetic waves can propagate almost without reflection to the bottom inside. In this invention, this is mainly achieved by adjusting the wall thickness s of the honeycomb core structure unit. t The design aims to improve intrinsic impedance, making the intrinsic impedance change continuously.

[0048] In a specific embodiment of this example, the honeycomb core structure unit is made of high-temperature resistant Si3N4 ceramic as the matrix material, and the broadband radome is finally fabricated. The specific structural parameters are: s tu =1.1mm, s td =6.4mm, r t =4mm and H t =10mm; In this embodiment, the broadband radome varies with the wall thickness s of the honeycomb core structure unit. t The linear change in impedance exhibits the characteristic of continuous change in intrinsic impedance, such as... Figure 2 As shown, as the wall thickness of the honeycomb core structure unit linearly changes from 1.6 mm on the upper surface to 6.4 mm in the middle layer, the intrinsic impedance of the broadband radome continuously decreases from 326 Ω to 239 Ω; conversely, as the wall thickness of the honeycomb core structure unit linearly changes again from 6.4 mm in the middle layer to 1.6 mm on the lower surface, the intrinsic impedance of the broadband radome continuously increases from 239 Ω to 326 Ω. Furthermore, the continuously varying intrinsic impedance allows for adjustable broadband transmission capability.

[0049] Furthermore, the broadband wave transmission capability of the broadband radome can be optimized by synergistically controlling the electromagnetic parameters of the electromagnetic material applied to the broadband radome and the structural parameters of the honeycomb core structure unit, so that when electromagnetic waves are incident perpendicularly, the input impedance of the broadband radome matches the free space wave impedance, and the electromagnetic waves can be transmitted to the maximum extent.

[0050] Therefore, the present invention also provides a broadband transmission optimization method for a broadband radome, comprising the following steps:

[0051] Step S1: Based on the linear variation law of the wall thickness of the honeycomb core structure unit, obtain the linear variation function of the wall thickness:

[0052]

[0053] Where s tus td and H t These represent the upper surface wall thickness, middle layer wall thickness, and height of the honeycomb core structure unit of the broadband radome.

[0054] Step S2, based on the dielectric constant ε of the matrix material of the following honeycomb core structure unit. r_eff The calculation formula (2) is used, and the result of step S1 is substituted into it to obtain the function ε of the broadband radome as a function of the vertical incident height z. r_eff (z);

[0055]

[0056] Where, ε r It is the relative permittivity of the matrix material. s is the fill factor (volume fraction of matrix material). t (z) represents the wall thickness of the honeycomb core structure unit, which varies linearly with the vertical incident height z. t denoted as the side length of the honeycomb core structure unit.

[0057] Step S3, based on the intrinsic impedance η of the following honeycomb core structure unit t Calculate formula (3), and substitute it into ε in step S2. r_eff (z), to obtain the intrinsic impedance η of the broadband radome as a function of the vertical incident height z. t (z);

[0058]

[0059] Where Z0 represents the free-space wave impedance, μ r This indicates the relative permeability of the radome material.

[0060] Step S4: For a broadband radome with continuously varying intrinsic impedance, electromagnetic waves can propagate almost without reflection from the top layer to the bottom layer along the incident direction inside it. Considering the broadband radome as a multi-layered structure infinitely divided along the vertical incident height z, the input impedance of the broadband radome can be calculated as follows:

[0061]

[0062] Where j is the imaginary unit, c represents the speed of light, f represents the incident wave frequency, and n represents the number of iterations; Δz t =H t / N t To divide the impedance-gradient broadband radome into N sections along the z-direction t The height of each subsequent iteration layer; Z t_in(n) This represents the input impedance of the nth layer of the broadband radome.

[0063] Step S5, the above formula (4) in N t When Z = +∞, the iterative calculation process can obtain the input impedance of the broadband radome with continuously varying structural parameters, i.e., Z. t_in(+∞) Given the theoretical value of the input impedance of the broadband radome, and considering the feasibility of calculation, it is approximated by a finite iterative process, by infinitely increasing N. t The value of makes By approximating the input impedance of a broadband radome based on impedance gradient, the transmittance T of this broadband radome along the vertical incident height z can be obtained as follows:

[0064]

[0065] Furthermore, the transmittance of the broadband radome was simulated and tested. The simulation results are as follows: Figure 3 As shown. Simulation results show that: for the height H of the honeycomb core structure unit t A 10mm wideband radome can achieve a transmittance of over 90% in the incident wave frequency range of 8.9 to 34.6 GHz.

[0066] In a specific embodiment of this example, simulation tests were also conducted on different matrix materials (i.e., different relative permittivity ε). r ), height H of the honeycomb core structure unit t Upper surface wall thickness s tu Intermediate layer wall thickness s td The effect of impedance-gradient broadband radome transmittance is shown in the following results. Figure 4 , Figure 5 , Figure 6 and Figure 7 As shown.

[0067] Figure 4 The results show that within the incident wave frequency range of 8.9–34.6 GHz, when the relative permittivity ε of the matrix material… r When the range of the impedance gradient is 2 to 4, the transmittance of the broadband radome based on the impedance gradient varies with the relative permittivity ε. r The broadband transmission performance decreases with increasing relative permittivity ε, meaning that the broadband transmission performance decreases with increasing relative permittivity ε. r The increase in [something] weakens.

[0068] Figure 5 The results show that within the incident wave frequency range of 8.9–34.6 GHz, when the height H of the cellular core structure unit… t When the transmittance of the impedance-gradient broadband radome varies with the height H of the honeycomb core structure unit, the transmittance of the radome varies with the height H of the honeycomb core structure unit. t The broadband transmission performance increases with the increase of the height H of the honeycomb core structural unit, that is, the broadband transmission performance increases with the increase of the height H of the honeycomb core structural unit. tIt increases and strengthens.

[0069] Figure 6 The results show that within the incident wave frequency range of 8.9–34.6 GHz, when the upper surface wall thickness s tu When the transmittance of the impedance-gradient broadband radome varies with the upper surface wall thickness s from 0.6 to 2.2 mm, the transmittance of the radome varies with the upper surface wall thickness s. tu The increase in thickness s is negligible, meaning the change in the upper surface wall thickness s is minimal. tu The change has little effect on the transmittance of the impedance-gradient broadband radome.

[0070] Figure 7 The results show that within the incident wave frequency range of 8.9–34.6 GHz, when the intermediate layer wall thickness s td When the transmittance of the broadband radome based on impedance gradient varies from 2.4 to 6.4 mm, the transmittance of the intermediate layer wall thickness s increases with the range of s. td The increase in thickness s is minimal, meaning the intermediate layer wall thickness s... td The change has little effect on the transmittance of the impedance-gradient broadband radome.

[0071] In summary, the preliminary results of this invention indicate that the smaller the relative permittivity of the substrate material, the larger the height of the honeycomb core structure unit, and the better the broadband transmission performance. Furthermore, the variation of the upper surface wall thickness and the middle layer wall thickness plays a fine-tuning role in the transmittance. Through the synergistic optimization of the substrate material and structural parameters, the optimized control design of the broadband radome based on impedance gradient can be achieved.

[0072] In summary, the impedance-gradient broadband radome provided by this invention, through the design of the honeycomb core structure unit and the selection of the substrate material, achieves a broadband radome with excellent impedance matching characteristics, solving the problems of broadband transmission, load-bearing capacity, and performance stability that are difficult to meet with traditional half-wavewall dielectric radomes. Therefore, the impedance-gradient broadband radome designed in this invention has broad application prospects in satellite communication systems, broadband communication aircraft, and other fields.

[0073] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A wideband radome based on impedance tapering, characterized in that, Include: A plurality of honeycomb core structure units, wherein the honeycomb core structure units are arranged in a honeycomb array; Each of the aforementioned honeycomb core structure units has a hexagonal cross-section and is hollow inside; The wall thickness of each of the aforementioned honeycomb core structural units varies linearly between its upper and lower surfaces with respect to the direction of perpendicular incidence of electromagnetic waves. The wall thickness of each of the honeycomb core structural units increases linearly from its upper surface to the intermediate layer between the upper and lower surfaces. The wall thickness decreases linearly from the intermediate layer to the lower surface; The intermediate layer is located at half the height of the honeycomb core structure unit; the linear change in the wall thickness of the honeycomb core structure unit is symmetrical and linear, with the intermediate layer as the boundary. The aforementioned honeycomb core structure unit is made of Si3N4 ceramic.

2. A method for optimizing the wave transmission of a broadband radome, implemented based on the broadband radome as described in claim 1, characterized in that, Includes the following steps: Step S1: Based on the linear variation law of the wall thickness of the honeycomb core structure unit, obtain the linear variation function of the wall thickness; Step S2: Based on the calculation formula of the equivalent dielectric constant of the cellular core structure unit, and combined with the linear variation function of the wall thickness, the function of the equivalent dielectric constant of the broadband radome as a function of the vertical incident height is obtained. ε r_eff ( z ); Step S3, based on the calculation formula of intrinsic impedance, combined with the results in step S2... ε r_eff ( z The intrinsic impedance of the broadband radome as a function of the vertical incident height is obtained. Step S4: Based on the intrinsic impedance obtained in step S3 and the characteristic of continuous change of intrinsic impedance, calculate the input impedance of the broadband radome. Step S5: By iteratively calculating the input impedance in step S4, the transmittance of the broadband radome at the vertical incident height is obtained. T .

3. The method for optimizing the wave transmission of a broadband radome as described in claim 2, characterized in that, In step S2, the equivalent dielectric constant of the broadband radome varies as a function of the vertical incident height. ε r_eff ( z )for: In the formula, ε r It is the relative permittivity of the matrix material. As the fill factor, s t ( z ( ) represents the wall thickness of the honeycomb core structure unit, which varies linearly with the vertical incident height z. r t denoted as the side length of the honeycomb core structure unit.

4. The method for optimizing the wave transmission of a broadband radome as described in claim 3, characterized in that, In step S3, the intrinsic impedance of the broadband radome as a function of the vertical incident height is: In the formula, Z 0 Represents free-space wave impedance. μ r This indicates the relative permeability of the radome substrate material.

5. The method for optimizing the wave transmission of a broadband radome as described in claim 4, characterized in that, In step S4, the input impedance of the broadband radome is: In the formula, j The imaginary unit, c Represents the speed of light. f Indicates the frequency of the incident wave. n Indicates the number of iterations; To adapt the impedance-gradient broadband antenna radome along z Directional segmentation Nt The height of each subsequent iteration layer; H t The height of the honeycomb core structure unit of the broadband radome; The broadband antenna radome is described as follows: n The input impedance of the layer.

6. The method for optimizing the wave transmission of a broadband radome as described in claim 5, characterized in that, In step S5, the transmittance of the broadband radome at the vertical incident height is... T for: In the formula, This indicates that the broadband antenna cover is along... z Divided into N t The theoretical value of the input impedance after the layer.

7. The method for optimizing the wave transmission of a broadband radome as described in claim 6, characterized in that, The smaller the relative permittivity of the matrix material of the honeycomb core structure unit, the greater the height of the honeycomb core structure unit, and the better the wave transmission performance of the broadband radome. The change in wall thickness plays a fine-tuning role in the wave transmission performance of the radome.

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