Active regulation stealth ceramic radome and design method thereof

Abstract

The application belongs to the field of electromagnetic wave control, and particularly relates to an active regulation stealth ceramic antenna cover and a design method thereof. The antenna cover integrates a ceramic cover, and based on the directional super surface passband range design of the parameter performance demand of a target antenna cover and the change of the used ceramic material with temperature, directional design of a controllable frequency selection surface is supplemented, then the variable capacitance diode of the controllable frequency selection surface is used to actively and accurately calibrate the passband when the ambient temperature changes, so as to compensate the influence of the change of the dielectric constant with temperature, and ensure that the working frequency point of the device remains stable and is not affected by temperature fluctuation. The application can realize transmission passband regulation range of 5.0GHz-9GHz, and the insertion loss is only-0.2dB; the stealth frequency band covers 5GHz-16GHz, and the RCS reduction is-9dB on average; by adjusting the parameters of the frequency selection surface, the influence of the change of the dielectric constant with temperature can be compensated, and the working frequency point can remain stable and is not affected by temperature fluctuation.

Description

Technical Field

[0001] The present invention belongs to the field of electromagnetic wave control, and specifically relates to an actively controlled stealth ceramic radome and a design method thereof. Background Art

[0002] With the development of electromagnetic stealth technology, research on stealth materials and structures has garnered widespread attention, particularly in the military and communications fields. As a crucial component of antenna systems, the stealth performance and electromagnetic transmittance of radomes directly impact the overall system's signal transmission and target protection. Existing stealth radomes often employ passive stealth technology, which reduces electromagnetic wave reflection by coating the surface with absorbing materials or designing multi-layer structures. However, passive stealth materials have poor adaptability in complex environments and are unable to adjust in real time to changes in the external electromagnetic environment, resulting in limitations in their stealth performance across different frequency bands and angles.

[0003] Ceramic materials not only possess excellent high-temperature resistance and mechanical strength, but also possess excellent electromagnetic properties, making them ideal for radome fabrication. By incorporating adjustable materials or structures, dynamic control of electromagnetic waves can be achieved, enabling them to maintain excellent stealth and electromagnetic transmittance across different frequency bands, angles, and environmental conditions. Furthermore, active control technology can reduce material usage and structural complexity, improving system lightweighting and reliability. Therefore, research on an actively controllable stealth ceramic radome and its fabrication technology is not only of great theoretical significance but also holds broad application prospects in the military, aerospace, and high-end communications equipment sectors.

[0004] However, in actual use, the dielectric constant of the quartz ceramic cover changes with increasing temperature, especially in high-temperature environments up to 1000°C. This change can cause frequency shifts in the operating frequency band, affecting the normal operation of the system. The relationship between dielectric constant and temperature can be described by a mathematical formula, such as: εr(T) = εr0 × f(T). Here, εr(T) is the dielectric constant at temperature T, εr0 is the dielectric constant at a reference temperature (such as room temperature), and f(T) is a function that reflects the temperature effect, the specific form of which depends on the temperature characteristics of the material. An increase in the dielectric constant changes the propagation speed of electromagnetic waves in the material, causing the operating frequency to shift. Summary of the Invention

[0005] To address these issues and shortcomings, and to address the problem of temperature fluctuations in the operating band of existing stealth radomes, which can cause frequency shifts in the operating frequency band and thus affect the normal operation of the system, the present invention provides an actively controlled stealth ceramic radome and its design method. This radome, integrated with a ceramic outer cover, features broadband stealth and tunable passband. This allows system mismatches caused by temperature fluctuations to be mitigated by actively adjusting parameters.

[0006] An actively controlled stealth ceramic radome comprises, from top to bottom in thickness direction, a ceramic layer A, a metasurface layer B, air C and a controllable frequency selective surface D.

[0007] The metasurface layer B is constructed by two super units, super unit 0 and super unit 1, in a checkerboard manner. The two super units are alternately arranged in a single longitudinal and transverse direction (that is, two adjacent super units in a single direction are different). The checkerboard structure design allows electromagnetic waves to undergo phase interference and scattering attenuation in different directions, reducing the intensity and directionality of the reflected waves, thereby achieving the purpose of stealth or reducing radar detection.

[0008] The structure of the super unit in the thickness direction is a metal layer B1 and a dielectric layer B0 from top to bottom. The super unit in the horizontal direction is a large square composed of a 3×3 square basic unit matrix.

[0009] The basic unit is a square dielectric layer B0 with a side length of p0, on which a patterned metal layer B1 is arranged; the patterned metal layer B1 is composed of two axially symmetrical bent metal lines, B01 and B02. The bent metal lines in the B01 part extend the induced current path within the basic unit through multiple bending, increasing the equivalent inductance of the basic unit, thereby significantly improving the low-frequency transmission performance of the basic unit and expanding the passband range.

[0010] The direction of the line connecting the two end points of the bent metal line of the basic unit metal layer B1 is defined as horizontal, parallel to the edge of the square dielectric layer B0, and serves as the basic unit 00; the basic unit 00 is rotated 90° counterclockwise around its center to obtain the basic unit 11; and then the basic unit 00 is arranged in a 3×3 matrix to form the super unit 0, and the basic unit 11 is arranged in a 3×3 matrix to form the super unit 1.

[0011] The impedance matching of the air layer C is achieved by adjusting the thickness, thereby optimizing the scattering performance of the metasurface layer B to the incident electromagnetic waves.

[0012] The basic unit of the controllable frequency selective surface D is a square laminated structure with a period of p1, which comprises a metal layer D0, a dielectric layer D1, a metal layer D2, a dielectric layer D3 and a metal layer D4 stacked in sequence in the thickness direction, for a total of five layers.

[0013] The metal layer D0 is identical to the metal layer D4 and consists of a special-shaped metal outer ring D00 and a central metal patch D05.

[0014] The special-shaped metal outer ring D00 is based on a square ring with an outer ring that has the same period p1 as the square (that is, the four outer edges of the square ring coincide with the sides of the square). A regular octagon is divided into four equal parts by its two mutually perpendicular diagonals to obtain a quadrilateral. The right-angled vertices and two right-angled sides of the quadrilateral are then used to adaptively replace the outer corners and the corresponding two sides of the square ring. The four quadrilaterals replace the four outer corner areas of the square ring in a one-to-one correspondence, thus forming the special-shaped metal outer ring D00.

[0015] The central metal patch D05 is a regular octagonal metal patch, the center of which coincides with the center of the basic unit, and the central metal patch D05 does not intersect with the special-shaped metal outer ring D00. The diagonal of the basic unit square overlaps with the two diagonals of the regular octagon.

[0016] Four varactors are placed symmetrically along the diagonal lines connecting the shaped metal outer ring D00 and the central metal patch D05. The controllable frequency selective surface D dynamically controls the operating passband by adjusting the capacitance of the varactors, achieving selective control of the electromagnetic wave frequency.

[0017] The metal layer D2 is a horizontal and vertical cross metal wire grid D20 based on the basic unit square, and the four endpoints of the cross metal wire grid intersect with the four sides of the basic unit square; the center point of the cross metal wire is also provided with a metallized through hole S, which passes through the dielectric layers D1 and D3, and is then connected to the center of the metal layers D0, D2 and D4.

[0018] The size area of ​​a basic unit (11 and 00) of a metasurface is equal to that of four basic units of the controllable frequency selective surface D, that is, p0=2p1, and they are adaptively aligned in the thickness direction.

[0019] Furthermore, the bent metal line of B01 is bent 6 times, and the bent metal lines include: a transverse metal line E1, a longitudinal bent metal line E2, a transverse bent metal line E3, a longitudinal bent metal line E4, a transverse bent metal line E5, a longitudinal bent metal line E6 and a transverse bent metal line E7; and the transverse bent metal line E7 is connected to the axisymmetric part B02.

[0020] Furthermore, the tuning of the D channel of the controllable frequency selective surface is achieved according to the capacitance range of the varactor diode, thereby achieving system adaptation when the ambient temperature changes.

[0021] Furthermore, the varactor diode adopts a GaAs varactor diode of model MA46H120.

[0022] Furthermore, the air C is replaced by electromagnetic foam.

[0023] Furthermore, the design method of the active control stealth ceramic radome includes the following steps:

[0024] Step 1: Based on the parameter performance requirements of the target antenna, the dielectric constant of the ceramic material used, and the frequency shift range of the operating frequency band that changes with temperature, simulation modeling and design are used to determine the basic unit parameter dimensions of the metasurface layer B, the basic unit parameter dimensions of the controllable frequency selective surface D, and the thickness of the air C.

[0025] The basic unit parameter size of the metasurface layer B is expanded through the graphical bending metal lines to expand its passband range, so that it adapts to the frequency shift range of the working frequency band of the ceramic layer A which changes with temperature.

[0026] Step 2: Based on the model determined in step 1, and on the premise that the antenna cover parameters meet the current performance requirements, determine the capacitance range of the varactor diode of the controllable frequency selective surface D of the constructed model, so that the capacitance range of the varactor diode is adapted to the frequency shift range of the operating frequency band of the ceramic layer A that changes with temperature.

[0027] In summary, the antenna cover of the present invention integrates a ceramic outer cover, based on a metasurface passband range design that is directional according to the parameter performance requirements of the target antenna cover and the temperature changes of the ceramic material used, supplemented by the directional design of the controllable frequency selective surface. Then, the passband is actively and accurately calibrated when the ambient temperature changes through the varactor diode of the controllable frequency selective surface to compensate for the influence of the dielectric constant changing with temperature, thereby ensuring that the operating frequency of the device remains stable and is not affected by temperature fluctuations. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A perspective view of an actively controlled stealth ceramic radome according to an embodiment of the present invention;

[0029] Figure 2 Schematic diagram of the super unit and basic unit structure of the super surface layer B of an embodiment of the present invention;

[0030] Figure 3 Schematic diagram of the basic unit transmittance performance of the super surface layer B in the embodiment;

[0031] Figure 4 Schematic diagram of the structure of a controllable frequency selective surface D according to an embodiment of the present invention;

[0032] Figure 5 Schematic diagram of electromagnetic performance of an embodiment of the present invention; DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0034] A design method for an actively controlled stealth ceramic radome comprises the following steps:

[0035] Step 1: Based on the target antenna's performance requirements, the dielectric constant of the ceramic material used, and the temperature-dependent frequency shift range of the operating frequency band, design and determine the basic unit parameter dimensions of the metasurface layer B, the basic unit parameter dimensions of the controllable frequency selective surface D, and the thickness of the air C.

[0036] The basic unit parameter size of the metasurface layer B is expanded through the graphical bending metal lines to expand its passband range, so that it adapts to the frequency shift range of the working frequency band of the ceramic layer A which changes with temperature.

[0037] Step 2: Perform simulation modeling based on the parameters determined in step 1. Under the premise that the antenna cover parameters meet the current performance requirements, determine the capacitance range of the varactor diode of the controllable frequency selective surface D of the constructed model, so that the capacitance range of the varactor diode is adapted to the frequency shift range of the working frequency band of the ceramic layer A that changes with temperature.

[0038] The active control stealth ceramic radome structure finally designed in this embodiment is as follows Figure 1 As shown. The thickness direction of the radome is from top to bottom, consisting of ceramic layer A, super surface layer B, air layer C and controllable frequency selective surface D. Each layer is bonded by adhesive film and cured by heating to form a composite. Super surface layer B is an array constructed by super unit 0 and super unit 1 in a checkerboard manner, and the two super units are arranged alternately in a single direction of the longitudinal and transverse directions. The ceramic cover uses a high-purity quartz fiber needle-punched preform as a reinforcement and a high-purity silica sol as a matrix. After multiple impregnation, compounding, drying, and high-temperature calcination, the green body is obtained, and is prepared by precision CNC machining and post-processing. The thickness of the air layer C is 6 mm.

[0039] The schematic diagram of the metasurface unit structure is shown in Figure 2 As shown, it consists of a 0.25mm thick dielectric layer B0 and a metal layer B1. Super cell 0 is composed of 3×3 basic cells 00, and super cell 1 is composed of 3×3 basic cells 11. The basic cell p0 = 8mm. Super cell 1 is obtained by rotating super cell 0 90° counterclockwise around its center.

[0040] The patterned metal layer B1 consists of two axisymmetric curved metal lines, B01 and B02. For basic unit 00, the curved metal lines in B01, from bottom to top, include: a 2mm-long transverse metal strip E1, a 2.9mm-long longitudinal bent metal strip E2, a 1mm-long transverse bent metal strip E3, a 3.4mm-long longitudinal bent metal strip E4, a 2.2mm-long transverse bent metal strip E5, a 2.2mm-long longitudinal bent metal strip E6, and a 0.5mm-long transverse bent metal strip E7.

[0041] Figure 3 This is a schematic diagram of the basic unit transmittance performance of the metasurface layer B of this embodiment. The curved structure of the metal lines in the metasurface extends the path of the induced current, increases the equivalent inductance of the unit, and significantly improves the low-frequency transmittance performance of the unit, thereby expanding the passband range and further enhancing the energy transmission effect of the bottom FSS.

[0042] The structural diagram of the controllable frequency selective surface D in this embodiment is shown in FIG. Figure 4 As shown: the metal layer D0 includes, from the outside to the inside, a special-shaped metal outer ring D00 and a central metal patch D05, and the metal layer D4 is exactly the same as the metal layer D0.

[0043] The special-shaped metal outer ring D00 is based on a square ring with an outer ring that has the same period p1 = 4mm as the square. A regular octagon (the radius of the corresponding circumscribed circle is 1.25mm) is divided into four equal parts by its two mutually perpendicular diagonals to obtain a quadrilateral. Then, the right-angled vertices and two right-angled sides of the quadrilateral are adaptively used to replace the outer corners and the corresponding two sides of the square ring. The four quadrilaterals replace the four outer corner areas of the square ring (quadrilateral metal patches D01, D02, D03 and D04) one by one.

[0044] The regular octagonal metal patch D05 is located at the center of the basic unit (the radius of the corresponding circumscribed circle is 1.3mm). Varactors V1, V2, V3, and V4 are located in the gaps between metal patches D01, D02, D03, D04, and the center patch D05, arranged diagonally, with two diodes on each diagonal line.

[0045] A metal via S runs through the center of the basic unit with a radius of 0.2mm. Dielectric layers D1 and D3 are made of F4B220m, with a thickness of 1.85mm and a dielectric constant of 2.2. Metal layer D2 consists of a horizontal and vertical cross-shaped metal wire grid D20 with a length equal to the unit's periodicity of 4mm and a width of 0.2mm.

[0046] The entire active control stealth ceramic radome structure of this embodiment was simulated. Under plane wave excitation, the boundary conditions were set to open add space and the diode was set to RLC model. Based on the capacitance range of Macom model MA46H120 varactor diode, the capacitance range adopted in the simulation was 0.3-0.7pF. Figure 5 As shown in FIG, when the varactor changes from 0.3 to 0.7 pF, the tuning range of the passband covers 5 to 9 GHz.

[0047] The radome's RCS reduction performance was analyzed for each capacitance value. The average RCS reduction from 5 GHz to 16 GHz was 9 dB across all capacitance values. Broadband stealth was also ensured during passband tuning.

[0048] From the above embodiments, it can be seen that the actively controlled stealth ceramic antenna cover of the present invention has the ability to actively control the communication passband, broadband stealth characteristics and high temperature resistance characteristics. The passband is controlled by the capacitance of the varactor diode, and the control range covers 5-9GHz, with a maximum insertion loss of 0.2dB. In the 5GHz to 16GHz frequency band, the average RCS reduction reaches 9dB. The introduction of the ceramic cover enables the structure to have high-temperature ablation resistance, which can meet the needs of more high-temperature application scenarios; its excellent active control, stealth and high-temperature ablation resistance make it suitable for communication and stealth applications in high-temperature environments; and it has broadband stealth and passband tunable functions, which can reduce system incompatibility caused by temperature changes by actively adjusting parameters when the ambient temperature changes.

Claims

1. An actively controlled stealth ceramic radome, characterized by: From top to bottom in thickness direction, they are ceramic layer A, metasurface layer B, air C and controllable frequency selective surface D; The metasurface layer B is constructed by two super units, super unit 0 and super unit 1, in a checkerboard pattern. The two super units are alternately arranged in a single direction, longitudinally and transversely. The checkerboard structure design causes phase interference and scattering attenuation of electromagnetic waves in different directions, reducing the intensity and directionality of the reflected waves, thereby achieving the purpose of stealth or reducing radar detection; The structure of the super unit in the thickness direction is metal layer B1 and dielectric layer B0 from top to bottom. The super unit in the horizontal direction is a large square composed of a 3×3 square basic unit matrix. The basic unit is a square dielectric layer B0 with a side length of p0, on which a patterned metal layer B1 is placed. The patterned metal layer B1 is composed of two axisymmetric bent metal lines, B01 and B02. The bent metal lines in the B01 portion extend the induced current path within the basic unit through multiple bends, increasing the equivalent inductance of the basic unit. The direction of the line connecting the two end points of the bent metal line of the basic unit metal layer B1 is defined as horizontal, parallel to the edge of the square dielectric layer B0, and is used as the basic unit 00. The basic unit 00 is rotated 90 degrees counterclockwise around its center to obtain the basic unit 11. The basic unit 00 is then arranged in a 3×3 matrix to form the super unit 0, and the basic unit 11 is arranged in a 3×3 matrix to form the super unit 1. The air C achieves impedance matching, thereby optimizing the scattering performance of the metasurface layer B to the incident electromagnetic wave; The basic unit of the controllable frequency selective surface D is a square laminated structure with a period of p1, which is composed of a metal layer D0, a dielectric layer D1, a metal layer D2, a dielectric layer D3 and a metal layer D4 stacked in sequence in the thickness direction, for a total of 5 layers; Metal layer D0 and metal layer D4 are identical, consisting of a special-shaped metal outer ring D00 and a central metal patch D05; The special-shaped metal outer ring D00 is based on a square ring with the same outer ring period p1. A regular octagon is divided into four equal parts by its two perpendicular diagonals to obtain a quadrilateral. The right-angled vertices and two right-angled sides of the quadrilateral are then used to adaptively replace the outer corners and the corresponding two sides of the square ring. The four quadrilaterals replace the four outer corner areas of the square ring in a one-to-one correspondence, thus forming the special-shaped metal outer ring D00. The central metal patch D05 is a regular octagonal metal patch, the center of which coincides with the center of the basic unit, and the central metal patch D05 does not intersect with the special-shaped metal outer ring D00. The diagonal of the basic unit square overlaps with the two diagonals of the regular octagon. Four symmetrical varactor diodes are located at the four gaps between the two diagonals of the basic unit, connecting the special-shaped metal outer ring D00 and the central metal patch D05. The controllable frequency selective surface D dynamically controls the operating passband by adjusting the capacitance value of the varactor diodes, thereby achieving selective regulation of the electromagnetic wave frequency. Metal layer D2 is a horizontal and vertical cross metal wire grid D20 based on the basic unit square, and the four endpoints of the cross metal wire grid intersect with the four sides of the basic unit square. A metallized through hole S is also provided at the center of the cross metal wire. The metallized through hole S penetrates the dielectric layers D1 and D3 and is connected to the center of the metal layers D0, D2 and D4. The size and area of ​​a basic unit of a metasurface is equal to that of four basic units of the controllable frequency selective surface D, that is, p0=2p1, and they are adaptively aligned in the thickness direction.

2. The actively controlled stealth ceramic radome according to claim 1, characterized in that: The bent metal lines of B01 are bent six times, and the bent metal lines include: a transverse metal line E1, a longitudinal bent metal line E2, a transverse bent metal line E3, a longitudinal bent metal line E4, a transverse bent metal line E5, a longitudinal bent metal line E6, and a transverse bent metal line E7; and are connected to the axisymmetric part B02 through the transverse bent metal line E7.

3. The actively controlled stealth ceramic radome according to claim 1, characterized in that: The tuning of the D channel of the controllable frequency selective surface is achieved by regulating the capacitance range of the variable capacitance diode, thereby achieving system adaptation when the ambient temperature changes.

4. The actively controlled stealth ceramic radome according to claim 1, characterized in that: The varactor diode is a GaAs varactor diode, model MA46H120.

5. The actively controlled stealth ceramic radome according to claim 1, characterized in that: The air C is replaced by electromagnetic foam.

6. The actively controlled stealth ceramic radome according to claim 1, characterized in that: The dielectric constant of the ceramic layer A is 2.4 and the thickness is 8 mm; the thickness of all metal layers is 0.035 mm; the thickness of the dielectric layer B1 is 0.25 mm, the thickness of the dielectric layers D1 and D2 is 1.85 mm, the dielectric constant is 2.2, and the dielectric loss is 0.001; p0 = 8 mm, p1 = 4 mm.

7. The design method of an actively controlled stealth ceramic radome according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: Based on the target antenna's performance requirements, the dielectric constant of the ceramic material used, and the temperature-dependent frequency shift range of the operating frequency band, simulation modeling and design are used to determine the basic unit parameter dimensions of the metasurface layer B, the basic unit parameter dimensions of the controllable frequency selective surface D, and the thickness of the air C. The basic unit parameter size of the metasurface layer B is expanded through the graphic bending metal lines to adapt it to the working frequency band frequency shift range of the ceramic layer A which changes with temperature. Step 2: Based on the model determined in step 1, and on the premise that the antenna cover parameters meet the current performance requirements, determine the capacitance range of the varactor diode of the controllable frequency selective surface D of the constructed model, so that the capacitance range of the varactor diode is adapted to the frequency shift range of the operating frequency band of the ceramic layer A that changes with temperature.

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