Multilayer dielectric broadband antenna housing and impedance matching design method thereof

Abstract

The invention discloses a multilayer dielectric broadband antenna housing and an impedance matching design method thereof, and the method comprises the steps: S1, calculating the normalized input impedance of each dielectric layer through a layer-by-layer iteration mode, and obtaining the normalized input impedance Zin of the multilayer dielectric broadband antenna housing; s2, through the normalized input impedance Zin of the multi-layer dielectric broadband antenna housing, obtaining the wave transmission rate T of the multi-layer dielectric broadband antenna housing in the vertical incident direction; s3, analyzing the relationship between the impedance characteristics and the transmission characteristics in the perfect impedance matching state and the imperfect matching state; and S4, obtaining the final normalized input impedance of the multilayer dielectric broadband antenna housing with the impedance gradual change characteristic. Through theoretical design, the broadband wave-transparent performance of the multilayer dielectric broadband antenna housing is accurately and effectively improved, and the multilayer dielectric broadband antenna housing designed through the impedance matching design method can adapt to broadband antenna housings with different frequency bands and different wave-transparent rate requirements.

Description

Technical Field

[0001] The invention relates to the technical field of radomes, and in particular to a multi-layer dielectric broadband radome and an impedance matching design method thereof. Background Art

[0002] Radomes usually have a single-layer or multi-layer dielectric structure. Some special radomes also need to be coated with anti-static, rain-proof and aviation paint on the surface of the radome. The impact of these dielectric materials on the performance of the radome can be described using the equivalent transmission line theory. As the communication bandwidth of aircraft radars continues to expand, the working bandwidth of radar antennas is also continuously increasing, which requires the radome to also have broadband wave-transmitting performance.

[0003] Although there are relevant theoretical studies on the design of multi-layer dielectric broadband radome, it lacks the support of universal design basis and methods, making it difficult to achieve rapid and effective design of broadband radome. Therefore, it is necessary to develop a design method for broadband radome to meet the broadband wave-transparent design requirements of multi-layer dielectric broadband radome. Summary of the invention

[0004] The purpose of the present invention is to provide a multi-layer dielectric broadband radome and an impedance matching design method thereof, which can overcome the deficiencies and defects in the existing broadband radome design technology and meet the broadband wave-transparent design requirements of the multi-layer dielectric broadband radome.

[0005] To achieve the above object, the present invention provides a multi-layer dielectric broadband antenna cover having an impedance gradient structure, wherein the impedance gradient structure is a honeycomb core structure, which is formed by a plurality of regular hexagonal structural frames arranged in a honeycomb shape;

[0006] The wall thickness of the honeycomb core structure changes linearly in the vertical incident direction of the electromagnetic wave, that is, in the vertical incident direction of the electromagnetic wave from top to bottom, the wall thickness first increases and then decreases;

[0007] The multi-layer dielectric broadband antenna cover is provided with a first dielectric layer, a second dielectric layer, ..., an nth dielectric layer in sequence from bottom to top, that is, in a direction opposite to the vertical incident direction of the electromagnetic wave.

[0008] The present invention also provides an impedance matching design method for a multi-layer dielectric broadband antenna cover, comprising the following steps:

[0009] S1, calculate the normalized input impedance of each dielectric layer by layer iteration, and obtain the normalized input impedance Z of the multi-layer dielectric broadband radome in ;

[0010] S2, normalized input impedance Z through a multilayer dielectric broadband radome in , the wave transmittance T of the multilayer dielectric broadband antenna cover in the vertical incident direction is obtained;

[0011] S3, analyzing the relationship between the impedance characteristics and the transmission characteristics under perfect impedance matching and imperfect impedance matching conditions;

[0012] S4, obtain the final normalized input impedance of the multilayer dielectric broadband radome with impedance gradient characteristics.

[0013] Optionally, step S1 includes:

[0014] S1.1, calculate the normalized input impedance Z on the first dielectric layer in(1 ) is calculated as:

[0015]

[0016] In the formula, is the normalized eigenwave impedance of the first dielectric layer, and the parameter d1 is the thickness of the first dielectric layer, f is the frequency of the incident electromagnetic wave, c is the speed of light, and tanh is the hyperbolic tangent function; μ1 is the complex relative magnetic permeability of the first dielectric layer, and ε1 is the complex relative permittivity of the first dielectric layer;

[0017] S1.2, the normalized input impedance Z through the first dielectric layer in(1) , the normalized input impedance Z on the second dielectric layer is calculated in(2) The calculation formula is:

[0018]

[0019] In the formula, is the normalized eigenwave impedance of the second dielectric layer, and the parameter d2 is the thickness of the second dielectric layer; μ2 is the complex relative permeability of the second dielectric layer, and ε2 is the complex relative permittivity of the second dielectric layer;

[0020] S1.3, through layer-by-layer iteration, the normalized input impedance Z on the n-1th dielectric layer is obtained in(n-1) , and then the normalized input impedance Z on the nth dielectric layer is calculated in(n) The calculation formula is:

[0021]

[0022] In the formula, is the normalized eigenwave impedance of the nth dielectric layer, and the parameter d n is the thickness of the nth dielectric layer; μ n is the complex relative permeability of the nth dielectric layer, ε n is the complex relative permittivity of the nth dielectric layer;

[0023] S1.4, through iterative calculation, the normalized input impedance Z of the multilayer dielectric broadband radome is obtained in .

[0024] Optionally, the normalized input impedance Z of the multilayer dielectric broadband radome in step S1.4 is in for:

[0025] Z in =Z in '+jZ in ”

[0026] In the formula, the real part Z in ' and the imaginary part Z in ” represent the normalized input resistance and normalized input reactance of the multilayer dielectric broadband radome, respectively.

[0027] Optionally, the calculation formula of the wave transmittance T of the multilayer dielectric broadband antenna cover in the vertical incident direction in step S2 is:

[0028] T=|2Z in / (Z in +Z0)| 2 (4)

[0029] Where Z0 is the electromagnetic wave impedance of free space.

[0030] Optionally, the relationship between the impedance characteristic and the transmission characteristic in the perfect impedance matching state in step S3 is:

[0031] When the transmittance T=1, the electromagnetic wave impedance Z0 of free space is 1, the normalized input resistance of the multilayer dielectric broadband antenna cover is equal to 1, and the normalized input reactance is equal to 0.

[0032] Optionally, the step S3 of analyzing the relationship between the impedance characteristic and the transmission characteristic under the imperfect impedance matching state comprises the following steps:

[0033] When the wave transmission rate T≠1, by setting the wave transmission threshold T c (T≥T c ) to analyze and predict the transmission characteristics of multilayer dielectric broadband radomes;

[0034] Establish the wave transmission threshold T c Next Z in ' and Z in The relationship between:

[0035]

[0036] According to the inequality equation (5), a two-dimensional coordinate system of impedance characteristics is established to further analyze the strength of the transmission characteristics.

[0037] Optionally, the normalized input impedance calculation formula of the multilayer dielectric broadband radome with impedance gradient characteristics in step S4 is:

[0038]

[0039] Where j is an imaginary unit, c is the speed of light, f is the frequency of the incident electromagnetic wave, and n is the number of iterations; ΔZ t is the height of the iteration layer; Z t_in(n) represents the input impedance of the nth layer of the multilayer dielectric broadband radome with impedance gradient characteristics, ε t_eff (z) represents the function of the equivalent dielectric constant of the multilayer dielectric broadband radome with impedance gradient characteristics changing with the vertical incidence height, η t (z) represents the intrinsic impedance of the multilayer dielectric broadband antenna cover with impedance gradient characteristics as it changes with the vertical incidence height.

[0040] In summary, compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. The present invention provides a multi-layer dielectric broadband radome and an impedance matching design method thereof, which provides a theoretical design range of the input impedance of the broadband radome, clarifies the control design direction of the broadband radome in terms of materials and structure, provides a design basis for the broadband radome, enhances the effectiveness of the broadband radome design and improves the design efficiency.

[0042] 2. The present invention provides a multi-layer dielectric broadband antenna cover and an impedance matching design method thereof, wherein the antenna cover adopts an impedance gradient honeycomb core structure, which improves the input impedance within a wide frequency range, realizes a broadband matching design of the input impedance of the antenna cover and the electromagnetic wave impedance of the free space, and finally obtains a broadband wave transmission effect.

[0043] 3. The present invention provides a multi-layer dielectric broadband antenna cover and an impedance matching design method thereof, wherein the impedance characteristic region can be adjusted according to different wave transmission thresholds, and can adapt to the design of broadband antenna covers with different wave transmission requirements in different frequency bands. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A schematic diagram of a multi-layer dielectric broadband antenna cover of the present invention;

[0045] Figure 2 It is a schematic diagram of the impedance gradient honeycomb core structure used in the multi-layer dielectric broadband antenna cover of the present invention;

[0046] Figure 3 is the design result of the real part of the input impedance of the multilayer dielectric broadband radome of the present invention;

[0047] Figure 4is the design result of the imaginary part of the input impedance of the multilayer dielectric broadband radome of the present invention;

[0048] Figure 5 It is a schematic diagram of impedance matching design analysis of the multi-layer dielectric broadband antenna cover of the present invention;

[0049] Figure 6 This is a diagram showing the effect of wave transmittance of the multi-layer dielectric broadband antenna cover of the present invention. DETAILED DESCRIPTION

[0050] The following will be combined with the attached Figures 1 to 6 , the technical content, structural features, objectives achieved and effects of the present invention are described in detail through preferred embodiments.

[0051] It should be noted that the drawings are in a very simplified form and use non-precise proportions. They are only used to conveniently and clearly assist in explaining the embodiments of the present invention, and are not used to limit the conditions for the implementation of the present invention. Therefore, they have no substantive technical significance. Any structural modification, change in proportional relationship or adjustment of size, without affecting the effects and purposes that can be achieved by the present invention, should still fall within the scope of the technical content disclosed by the present invention.

[0052] In the description of the present invention, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0053] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0054] like Figure 2As shown, the multi-layer dielectric broadband antenna cover 200 has an impedance gradient structure, and the impedance gradient structure of the multi-layer dielectric broadband antenna cover 200 is a honeycomb core structure, that is, it is composed of a number of regular hexagonal structural frames arranged in a honeycomb shape; the wall thickness of the honeycomb core structure of the multi-layer dielectric broadband antenna cover 200 changes linearly in the vertical incident direction, that is, in the vertical incident direction from top to bottom, the wall thickness first increases and then decreases; wherein, the vertical incident direction refers to the incident direction of the electromagnetic wave in the free space after entering the broadband antenna cover.

[0055] In addition, if Figure 1 As shown, the broadband antenna cover with an impedance gradient structure of the present invention is composed of multiple layers of dielectrics. Along the bottom-up direction (the direction opposite to the vertical incident direction of the electromagnetic wave), that is, from close to the antenna 100 to far away from the antenna 100, n dielectric layers are arranged, and the first dielectric layer 201, the second dielectric layer 202, ..., the nth dielectric layer 203 are arranged in sequence.

[0056] The multi-layer dielectric broadband antenna cover 200 with a gradient impedance structure has a gradient impedance characteristic.

[0057] Due to the impedance gradient characteristics of the multi-layer dielectric broadband radome 200, the present invention also provides an impedance matching design method for the multi-layer dielectric broadband radome 200, so as to establish an analytical relationship between the input impedance and the wave transmittance of the multi-layer dielectric broadband radome 200 under non-perfect matching, and to optimize the input impedance of the multi-layer dielectric broadband radome 200 in a targeted manner according to the analytical relationship, so as to finally achieve the broadband wave transmittance requirements of the multi-layer dielectric broadband radome 200. Specifically, firstly, by constructing an associated analytical model of the impedance gradient characteristics and transmission characteristics of the multi-layer dielectric broadband radome 200, and then according to the wave transmittance requirements of the broadband radome, the impedance matching design of the broadband radome is performed to match it with the electromagnetic wave impedance of the free space, so as to achieve the highest transmission efficiency.

[0058] The impedance gradient characteristics of the multi-layer dielectric broadband antenna cover 200 are obtained through a layer-by-layer iterative analytical model; and the transmission characteristics are described based on the equivalent transmission line theory.

[0059] The multilayer dielectric has an important influence on the broadband wave transmission performance of the broadband radome, which can be described using the equivalent transmission line theory. The transmission line theory is based on the following assumptions: 1) the electromagnetic wave is a plane wave in the near area of ​​the antenna, and it propagates in a straight line from the transmitting aperture; 2) the curvature radius of the multilayer dielectric broadband radome 200 is much larger than the wavelength of the electromagnetic wave.

[0060] Based on the above assumptions, the interaction between the electromagnetic waves emitted by the antenna and the multilayer dielectric broadband antenna cover 200 can be approximated as the interaction between a plane wave and a dielectric plate. Therefore, the transmission characteristics of the multilayer dielectric broadband antenna cover 200 can be described using the equivalent transmission line theory.

[0061] The transmittance T of the electromagnetic wave vertically incident on the multi-layer dielectric broadband antenna cover 200 can be calculated from the relative complex dielectric constant, relative complex magnetic permeability and layer thickness of each dielectric layer. The normalized input impedance of the first dielectric layer 201 is iterated upward layer by layer to obtain the normalized input impedance of the nth dielectric layer 203.

[0062] Based on the above theoretical basis, the impedance matching design method of the multi-layer dielectric broadband antenna cover 200 is as follows:

[0063] Step S1, calculating the normalized input impedance of each dielectric layer by layer iteration, and obtaining the normalized input impedance Z of the multi-layer dielectric broadband antenna cover in .

[0064] S1.1, Calculate the normalized input impedance Z on the first dielectric layer 201 in(1) The calculation formula (the calculation formula can be calculated from the complex relative permittivity (ε1=ε1'-jε1") of the first dielectric layer 201 and the complex relative magnetic permeability (μ1=μ1'-jμ1") of the first dielectric layer 201 at the operating frequency):

[0065]

[0066] In the formula, is the normalized eigenwave impedance of the first dielectric layer 201, and the parameter d1 is the thickness of the first dielectric layer 201, f is the frequency of the incident electromagnetic wave, c is the speed of light, and tanh is the hyperbolic tangent function.

[0067] S1.2, through the normalized input impedance Z on the first dielectric layer 201 in(1) , calculate the normalized input impedance Z on the second dielectric layer 202 in(2) The calculation formula (which can be calculated from the complex relative dielectric constant (ε2=ε2'-jε2") of the second dielectric layer 202 and the complex relative magnetic permeability (μ2=μ2'-jμ2") of the second dielectric layer 202 at the operating frequency):

[0068]

[0069] In the formula, is the normalized eigenwave impedance of the second dielectric layer 202, and the parameter d2 is the thickness of the second dielectric layer 202 .

[0070] S1.3, through layer-by-layer iteration, the normalized input impedance Z on the n-1th dielectric layer is obtained in(n-1) , and then calculate the normalized input impedance Z on the nth dielectric layer 203 in(n) The calculation formula (based on the complex relative dielectric constant (ε n =ε n '-jε n ”) and the complex relative permeability (μ n =μ n '-jμ n ”) calculated as follows:

[0071]

[0072] In the formula, is the normalized eigenwave impedance of the nth dielectric layer 203, and the parameter d n is the thickness of the nth dielectric layer 203 .

[0073] S1.4, through the above iterative calculation, the normalized input impedance Z of the multilayer dielectric broadband antenna cover 200 is obtained in , which is Z in(n) The calculation result is expressed as Z in =Z in '+jZ in ”.

[0074] In the formula, the real part Z in ' and the imaginary part Z in ” represent the normalized input resistance and normalized input reactance of the multilayer dielectric broadband radome 200, respectively.

[0075] Step S2, through the normalized input impedance Z of the multi-layer dielectric broadband radome in , and obtain the transmittance T of the multilayer dielectric broadband antenna cover in the vertical incidence direction.

[0076] The calculation formula of the wave transmittance T of the multi-layer dielectric broadband antenna cover 200 in the vertical incident direction is:

[0077] T=|2Z in / (Z in +Z0)| 2 (4)

[0078] Where Z0 is the electromagnetic wave impedance of free space.

[0079] Step S3, analyzing the relationship between the impedance characteristics and the transmission characteristics in the perfect impedance matching state and the imperfect impedance matching state.

[0080] S3.1, obtain the relationship between the impedance characteristics and the transmission characteristics under the perfect impedance matching state;

[0081] When the transmittance T reaches the maximum (i.e., transmittance T=1), the multilayer dielectric broadband antenna cover 200 reaches an impedance matching condition close to a perfect state. Under this condition, the electromagnetic wave impedance Z0 of the free space is 1, the normalized input resistance of the multilayer dielectric broadband antenna cover 200 is equal to 1, and the normalized input reactance is equal to 0.

[0082] S3.2, analyze the relationship between impedance characteristics and transmission characteristics under imperfect impedance matching conditions;

[0083] S3.2.1, under the condition of imperfect impedance matching, the wave transmission rate T≠1, by setting the wave transmission threshold T c (T c is an arbitrary constant between 0 and 1) to limit the range of the transmittance T and make T ≥ T c , in order to analyze and predict the transmission characteristics of the multi-layer dielectric broadband radome 200;

[0084] S3.2.2, the complex form Z of the normalized input impedance of the multilayer dielectric broadband radome 200 in =Z in '+jZ in Substitute into formula (4) and derive the wave transmission threshold T c Next Z in ' and Z in ", which can be described by the following inequality:

[0085]

[0086] S3.2.3, establish a two-dimensional coordinate system for impedance characteristics;

[0087] Specifically, Z in ' is the x-axis, Z in " is the y-axis, and the impedance characteristic area is: As the center of the circle, The area outside the circle with a radius of can be further analyzed based on the impedance characteristic area to determine the strength of the transmission characteristics, that is, the size of the wave transmittance.

[0088] Step S4, obtaining the final normalized input impedance calculation formula of the multilayer dielectric broadband antenna cover 200 with impedance gradient characteristics:

[0089]

[0090] Where j is an imaginary unit, c is the speed of light, f is the frequency of the incident electromagnetic wave, and n is the number of iterations; ΔZ t is the height of the iteration layer; Z t_in(n) represents the input impedance of the nth layer of the multilayer dielectric broadband radome 200 with impedance gradient characteristics, ε t_eff (z) represents the function of the equivalent dielectric constant of the multilayer dielectric broadband radome 200 with impedance gradient characteristics changing with the vertical incident height, η t (z) represents the intrinsic impedance of the multilayer dielectric broadband antenna cover 200 with impedance gradient characteristics that changes with the vertical incident height.

[0091] In the above calculation formula (6), as the number of iterations increases, Z t_in(n) The theoretical calculation results of Z gradually stabilize; specifically, when the number of iterations is greater than 30, t_in(n) Remains almost unchanged.

[0092] The theoretical calculation results of the normalized input impedance of the multilayer dielectric broadband antenna cover 200 with impedance gradient characteristics are output as an image, forming a graph as shown in FIG. Figure 3 The input impedance real part design result of the multilayer dielectric broadband radome 200 is shown in FIG. Figure 4 The design result of the imaginary part of the input impedance of the multilayer dielectric broadband antenna cover 200 is shown in FIG. In the low frequency range below 8 GHz, the input impedance of the multilayer dielectric broadband antenna cover 200 has a large mismatch with the electromagnetic wave impedance of free space, and the wave transmittance in this frequency band is small; in the high frequency range above 8 GHz, the normalized input impedance real part Z in ' fluctuates around 1 (i.e. the normalized input resistance is equal to 1), the imaginary part Z in " fluctuates around 0 (i.e., the normalized input reactance is equal to 0). Combined with the theoretical analysis of step S6, the result shows that the input impedance of the multilayer dielectric broadband antenna cover 200 is well matched with the electromagnetic wave impedance of the free space, and a higher wave transmittance can be obtained in the high frequency range above 8 GHz.

[0093] like Figure 5 As shown in FIG. 1 , the impedance matching design analysis result of the multilayer dielectric broadband radome 200 is performed by using the impedance matching design method of the multilayer dielectric broadband radome 200. c =0.7 Substituting into formula (5), we can obtain the normalized input impedance real part Z in ' and the imaginary part Z in "The inequality between:

[0094] (Z in '-0.21) 2 +Z in ”2 ≥0.51 2

[0095] Then, the impedance characteristic region that meets the wave transmission threshold limit is determined. In the impedance characteristic two-dimensional coordinate system, the impedance characteristic region is: the area outside the circle with (0.21, 0) as the center and 0.51 as the radius. All impedances with a wave transmission threshold T ≥ 0.7 are within this region.

[0096] Furthermore, the real part of the normalized input impedance Z in ' is the x-axis, imaginary part Z in " is the y-axis, and the frequency is the z-axis. The impedance characteristic region in the three-dimensional coordinate system related to the frequency is: the region outside the gray cylinder, and the input impedance in this region can meet the condition that the wave transmittance is greater than the wave transmittance threshold. Therefore, the gray solid line in the figure represents the perfect matching characteristic line, which represents the normalized input impedance real part Z in ' is 1, the imaginary part Z in " is 0, the wave transmittance of the point on the perfect matching characteristic line is 1; the wave transmittance can be determined according to the vertical distance from the impedance characteristic point to the perfect matching characteristic line; specifically, the closer the normalized input impedance is to this perfect matching characteristic line, the greater the wave transmittance, and vice versa. The wave transmittance band where the wave transmittance is greater than the wave transmittance threshold can also be determined by the frequency range in the impedance characteristic region. The wave transmittance band can be determined by the real part Z of the normalized input impedance. in ' and the imaginary part Z in "Sure.

[0097] Going further, Figure 5 The figure also shows the difference in transmission characteristics between the multilayer dielectric broadband radome 200 designed by the impedance matching design method of the present invention and the single-layer dielectric radome. Most of the transmission characteristic lines of the multilayer dielectric broadband radome 200 of the present invention are located in the impedance characteristic region that meets the wave transmission threshold limit (i.e., T≥0.7), while most of the transmission characteristic lines of the single-layer dielectric radome are not located in the impedance characteristic region that meets the wave transmission threshold limit (i.e., T≥0.7). The figure shows that the multilayer dielectric broadband radome 200 of the present invention has better transmission characteristics.

[0098] After further analysis, it was found that the multi-layer dielectric broadband antenna cover 200 has a transmittance of more than 70% in the frequency range above 7 GHz; while the single-layer dielectric antenna cover has a transmittance of more than 70% only in the frequency range above 7 GHz; the multi-layer dielectric broadband antenna cover 200 specifically improves the impedance matching characteristics in the C-Ka band.

[0099] like Figure 6As shown, the multi-layer dielectric broadband radome 200 designed using the impedance matching design method of the multi-layer dielectric broadband radome 200 has significantly improved broadband wave transmission performance compared to the single-layer dielectric radome; the multi-layer dielectric broadband radome 200 can achieve more than 80% broadband wave transmission in the P-Ku band and part of the Ka band, and more than 90% broadband wave transmission in the Ku band and part of the X and Ka bands.

[0100] In summary, the multi-layer dielectric broadband antenna cover and its impedance matching design method provided by the present invention can accurately and effectively improve the broadband wave transmission performance of the multi-layer dielectric broadband antenna cover through the support of a clear theoretical design range, and the multi-layer dielectric broadband antenna cover designed by the impedance matching design method can adapt to broadband antenna covers with different frequency bands and different wave transmittance requirements.

[0101] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the invention. After reading the above content, it will be obvious to those skilled in the art for various modifications and substitutions of the present invention. Therefore, the protection scope of the present invention should be limited by the attached claims.

Claims

1. A multi-layer dielectric broadband antenna cover, characterized in that: The broadband antenna cover has an impedance gradient structure, which is a honeycomb core structure, formed by a plurality of regular hexagonal structural frames arranged in a honeycomb shape; The wall thickness of the honeycomb core structure changes linearly in the vertical incident direction of the electromagnetic wave, that is, in the vertical incident direction of the electromagnetic wave from top to bottom, the wall thickness first increases and then decreases; The multi-layer dielectric broadband antenna cover is provided with a first dielectric layer, a second dielectric layer, ..., an nth dielectric layer in sequence from bottom to top, that is, in a direction opposite to the vertical incident direction of the electromagnetic wave.

2. An impedance matching design method for a multi-layer dielectric broadband radome, based on the multi-layer broadband radome as claimed in claim 1, characterized in that: The following steps are involved: S1, calculate the normalized input impedance of each dielectric layer by layer iteration, and obtain the normalized input impedance Z of the multi-layer dielectric broadband radome in ; S2, normalized input impedance Z through a multilayer dielectric broadband radome in , the wave transmittance T of the multilayer dielectric broadband antenna cover in the vertical incident direction is obtained; S3, analyzing the relationship between the impedance characteristics and the transmission characteristics under perfect impedance matching and imperfect impedance matching conditions; S4, obtain the final normalized input impedance of the multilayer dielectric broadband radome with impedance gradient characteristics.

3. The impedance matching design method according to claim 2, characterized in that: The step S1 comprises: S1.1, calculate the normalized input impedance Z on the first dielectric layer in(1 ) is calculated as: In the formula, is the normalized eigenwave impedance of the first dielectric layer, and the parameter d1 is the thickness of the first dielectric layer, f is the frequency of the incident electromagnetic wave, c is the speed of light, and tanh is the hyperbolic tangent function; μ1 is the complex relative magnetic permeability of the first dielectric layer, and ε1 is the complex relative permittivity of the first dielectric layer; S1.2, the normalized input impedance Z through the first dielectric layer in(1) , the normalized input impedance Z on the second dielectric layer is calculated in(2) The calculation formula is: In the formula, is the normalized eigenwave impedance of the second dielectric layer, and the parameter d2 is the thickness of the second dielectric layer; μ2 is the complex relative permeability of the second dielectric layer, and ε2 is the complex relative permittivity of the second dielectric layer; S1.3, through layer-by-layer iteration, the normalized input impedance Z on the n-1th dielectric layer is obtained in(n-1) , and then the normalized input impedance Z on the nth dielectric layer is calculated in(n) The calculation formula is: In the formula, is the normalized eigenwave impedance of the nth dielectric layer, and the parameter d n is the thickness of the nth dielectric layer; μ n is the complex relative permeability of the nth dielectric layer, ε n is the complex relative permittivity of the nth dielectric layer; S1.4, through iterative calculation, the normalized input impedance Z of the multilayer dielectric broadband radome is obtained in .

4. The impedance matching design method according to claim 3, characterized in that: The normalized input impedance Z of the multilayer dielectric broadband radome in step S1.4 is in for: WITH in =Z in '+jZ in ” In the formula, the real part Z in ' and the imaginary part Z in ” represent the normalized input resistance and normalized input reactance of the multilayer dielectric broadband radome, respectively.

5. The impedance matching design method according to claim 4, characterized in that: The calculation formula of the wave transmittance T of the multilayer dielectric broadband antenna cover in the vertical incident direction in step S2 is: T=|2Z in / (Z in +Z0)| 2 (4) Where Z0 is the electromagnetic wave impedance of free space.

6. The impedance matching design method according to claim 5, characterized in that: The relationship between the impedance characteristic and the transmission characteristic in the perfect impedance matching state in step S3 is: When the transmittance T=1, the electromagnetic wave impedance Z0 of free space is 1, the normalized input resistance of the multilayer dielectric broadband antenna cover is equal to 1, and the normalized input reactance is equal to 0.

7. The impedance matching design method according to claim 6, characterized in that: The step S3 of analyzing the relationship between the impedance characteristics and the transmission characteristics under the imperfect impedance matching state comprises the following steps: When the wave transmission rate T≠1, by setting the wave transmission threshold T c (T≥T c ) to analyze and predict the transmission characteristics of multilayer dielectric broadband radomes; Establish the wave transmission threshold T c Next Z in ' and Z in The relationship between: According to the inequality equation (5), a two-dimensional coordinate system of impedance characteristics is established to further analyze the strength of the transmission characteristics.

8. The impedance matching design method according to claim 7, characterized in that: The normalized input impedance calculation formula of the multilayer dielectric broadband radome with impedance gradient characteristics in step S4 is: Where j is an imaginary unit, c is the speed of light, f is the frequency of the incident electromagnetic wave, and n is the number of iterations; ΔZ t is the height of the iteration layer; Z t_in(n) represents the input impedance of the nth layer of the multilayer dielectric broadband radome with impedance gradient characteristics, ε t_eff (z) represents the function of the equivalent dielectric constant of the multilayer dielectric broadband radome with impedance gradient characteristics changing with the vertical incidence height, η t (z) represents the intrinsic impedance of the multilayer dielectric broadband antenna cover with impedance gradient characteristics as it changes with the vertical incidence height.

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