A function reconfigurable electromagnetic superstructure for radar cross section reduction

Abstract

The application discloses a function reconfigurable electromagnetic superstructure for radar scattering cross section reduction, and belongs to the technical field of electrically variable electromagnetic regulation superstructure.The application realizes the switching of two functions on the same structure, and introduces a curved metal structure with broadband resonance characteristics into the design of a switchable surface.Through the special design of the connection mode of resistors, PIN diodes and metal strips in different directions, the same switchable function of two frequency bands is realized on the same structure.Because the realization of the two states depends on the multi-resonance characteristics of the same curved structure, the two functions have the same working frequency band, and both exhibit broadband characteristics.The superstructure units are arranged in an array under the satisfaction of the cancellation principle, the superstructure realizes the broadband stealth design under two different working principles, can realize flexible switching and dynamic control, optimizes the design of a traditional stealth scheme, and can meet a complex radar detection environment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrically variable electromagnetic regulation superstructure, and more particularly, relates to a function reconfigurable electromagnetic superstructure for radar scattering cross section reduction. BACKGROUND

[0002] Stealth technology is a technology for making a target not be found in electromagnetic wave, sound wave, infrared light and visible light detection. The stealth capability of a target in electromagnetic wave is a key in modern informationized war and is a focus of attention of countries in the world. Radar scattering cross section (RCS) is a measure of the reflection power capability of a target in a specific direction when the target is irradiated by electromagnetic wave, and is an important evaluation index in electromagnetic stealth technology. Loading of wave-absorbing materials and shape design are common electromagnetic stealth technologies in early research, but limit other engineering performances of a radar target. Electromagnetic superstructure is widely applied in the field of electromagnetic stealth due to its excellent electromagnetic performance.

[0003] Superstructure technology provides many electromagnetic stealth schemes by virtue of excellent electromagnetic performance, such as an artificial magnetic conductor (AMC) phase cancellation surface, a frequency selective absorber (FSA) surface and various low scattering schemes. The principle of the AMC phase cancellation scheme is regulation of spatial distribution of reflected electromagnetic wave energy. After the same incident electromagnetic wave is reflected by different AMC surfaces, a phase difference of 180° is formed between reflected waves, and based on the interference cancellation principle, a chessboard-like structure is formed to reduce reflected wave energy in the direction of incident electromagnetic wave. Although the AMC cancellation scheme can effectively reduce the single-station RCS of a radar target, the bistatic RCS is increased, which reduces the survival rate of the radar target under a dual-base station radar and limits the application occasions of the scheme. The FSA frequency selective absorption scheme is realized by converting incident electromagnetic wave energy into heat. Electromagnetic induction current is generated on the resonant structure by incident electromagnetic wave energy, and is converted into Joule heat through a lumped resistance or loss material to reduce reflected electromagnetic wave energy. The FSA scheme can effectively reduce the single-station and bistatic RCS, but the generation of heat increases the possibility of detection of the target by infrared light. Therefore, the AMC, FSA and other low scattering schemes can achieve stealth design in a certain detection environment based on specific working principles, but have respective application defects and are insufficient to meet the increasingly complex detection environment.

[0004] Functional reconfigurable electromagnetic superstructure has attracted much attention and developed rapidly due to its flexible real-time control of functions. Early researches on functional reconfigurable electromagnetic superstructure focused on the switching of reflection and absorption functions, and only had one stealth state and another state of strong reflection. Recently, there are also researches and designs on switching between two stealth states, but there are problems such as non-uniform working frequency bands of the two stealth states, narrow bandwidth and large size, which do not meet the wideband stealth requirements in a fixed frequency band; at the same time, the large size of the unit will cause the problem of periodic superstructure grating.

[0005] In summary, the existing problems of the prior art are that the common superstructure stealth technology can meet the stealth requirements in a specific environment, but the single-function stealth scheme has limitations in application scenarios. The multi-functional switchable stealth technology can select different stealth strategies in different battlefield environments without changing the structure shape, and has shown significant advantages in the increasingly complex electromagnetic detection environment. However, the current stealth function switching research has problems such as non-uniform working frequency bands of the switching states and narrow working bandwidth. Therefore, designing a superstructure applied to radar target cross-section area reduction, which can not only realize flexible switching between two different stealth states, but also ensure the wideband characteristics of the two stealth states and the same working frequency band, is the key and difficulty of current stealth superstructure design. SUMMARY

[0006] In view of the above defects or improvement needs of the prior art, the present application provides a functional reconfigurable electromagnetic superstructure for radar scattering cross-section area reduction, which aims to solve the technical problems of non-uniform working frequency bands of the switching states and narrow working bandwidth in the current stealth function switching research.

[0007] To achieve the above-mentioned purpose, the present application provides a functional reconfigurable electromagnetic superstructure for radar scattering cross-section area reduction, comprising: a plurality of functional subarrays; the arrangement mode of the plurality of functional subarrays satisfies the interference cancellation principle; the functional subarray comprises a plurality of periodically arranged basic units; the basic unit comprises an X-direction dielectric substrate, a Y-direction dielectric substrate and a metal reflection plate; the X-direction dielectric substrate and the Y-direction dielectric substrate are arranged on the metal reflection plate and both adopt a bent metal strip as a resonant structure;

[0008] The X-direction dielectric substrate is provided with PIN diodes and absorption resistors in parallel with each other; the Y-direction dielectric substrate is provided with PIN diodes and absorption resistors in series with each other;

[0009] The switching state of the PIN diode is controlled by a direct current bias, and the switching between the absorption and cancellation functions is realized in the same frequency band, thereby reducing the radar scattering cross-section area of the target.

[0010] Further, the X-direction dielectric substrate and the Y-direction dielectric substrate are distributed in a three-dimensional orthogonal nested manner.

[0011] Further, the X-direction medium substrate is provided with two non-communicating metal strips; one of the metal strips is horizontally distributed in the middle section and vertically downward bent at both ends; the other metal strip is horizontally distributed at the bottom of the substrate as a reflecting ground; the Y-direction medium substrate is provided with one metal strip; the metal strip is horizontally distributed in the middle section and vertically downward bent at both ends, and a metal reflecting plate is used as the reflecting ground.

[0012] Further, the X-direction medium substrate is connected to two groups of circuits formed by parallel connection of resistors and PIN diodes; the Y-direction medium substrate is connected to two groups of circuits formed by series connection of resistors and PIN diodes.

[0013] Further, the two groups of circuits in the X-direction medium substrate and the Y-direction medium substrate are symmetrically distributed at the positions where the metal strips are horizontally distributed.

[0014] Further, a number of self-resonant inductors in the working frequency band are used to realize isolation between the in-band DC bias circuit and the microwave circuit.

[0015] Further, the X-direction medium substrate and the Y-direction medium substrate are printed circuit boards or ceramic substrates.

[0016] Further, the metal reflecting plate is realized by etching a metal pattern on a substrate covered with metal and using surface mount technology to solder lumped elements.

[0017] Overall, compared with the prior art, the above technical solutions conceived by the present application can achieve the following beneficial effects.

[0018] Due to the differences in the basic principles of the two ways of absorption (amplitude regulation) and cancellation (phase regulation), there are differences in design: the absorption structure needs to satisfy that the distance between the absorption structure and the reflecting plate is one-quarter of the wavelength, while the phase regulation unit requires that the metal structure is close to the reflecting plate. There are related researches that use different metal structures or different branches of the same metal structure in the same unit to realize the two functions, but such design leads to the problem of large difference in the working frequency bands of the two modes and narrow bandwidth. The present application realizes the switching of the two functions in the same structure, and introduces a curved metal structure with wideband resonance characteristics into the design of the switchable surface. By specially designing the connection mode of the resistors, PIN diodes and metal strips in different directions, the switchable function of the same frequency band is realized in the same structure. Since the realization of the two states depends on the multi-resonance characteristics of the same curved structure, the working frequency bands of the two functions are the same, and both exhibit wideband characteristics. The electromagnetic superstructure formed by arranging and laying out under the satisfaction of the interference cancellation principle has two switchable schemes with different working principles and the same frequency band, which provides a new idea for reducing the radar cross section.

[0019] The design of the bending structure is beneficial to the miniaturization of the unit structure, and can effectively solve the problem of periodic superstructure reflection grating.

[0020] The cancellation stealth mode can effectively reduce the single-station RCS, but the bistatic RCS of part of the space angle is significantly enhanced; under the absorption stealth mode, the single-station and bistatic RCS can be significantly reduced, but the heat generation will reduce the survival rate of the target under infrared detection. The single function scheme can realize the reduction of scattering bandwidth and the improvement of intensity, but ignores the disadvantages of the scheme in practical application. The functional reconfigurable electromagnetic stealth superstructure proposed by combining the above two scheme ideas can effectively avoid the defects of the single function structure, and can flexibly and real-timely switch to cope with different detection environments. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a functional reconfigurable superstructure basic unit structure for S, C band target radar scattering cross section reduction provided by the embodiment of the application;

[0022] Figure 2 In the figure, (a) is a functional subarray composed of 4*4 basic units, (b) is a 2*2 superstructure obtained by rotating the functional subarray around the Z axis, and (c) is a direct current bias circuit.

[0023] Figure 3 is a functional reconfigurable superstructure unit model provided by the embodiment of the application, and the reflection coefficient amplitude and phase diagram under two working modes are shown; wherein the reflection coefficient amplitudes of the unit in the x and y directions under the absorption mode are as shown in Figure 3 (a) of the figure, xx , and yy respectively represent the reflection coefficient amplitudes of the x polarized and Y polarized electromagnetic waves; the reflection coefficient amplitudes and phase curves of the unit in the x and y directions under the cancellation mode are as shown in Figure 3 (b) of the figure, respectively represent the reflection coefficient phases of the x polarized and Y polarized electromagnetic waves.

[0024] Figure 4 is the scattering characteristics of the functional reconfigurable stealth super surface under two working modes provided by the embodiment of the application; under the absorption and cancellation modes, the RCS values of the superstructure and the RCS curve of the same area metal surface are as shown in Figure 4 (a) of the figure, Figure 4 (b) of the figure shows the RCS reduction amount relative to the metal surface;

[0025] Figure 5 is a three-dimensional scattering pattern comparison of the functional reconfigurable stealth super surface under two working modes and the same area ideal metal conductor at 3, 5 and 7 GHz frequency points provided by the embodiment of the application; wherein, Figure 5Fig. 3 shows the three-dimensional scattering diagram of the function reconfigurable stealth superstructure in the absorption mode at 3, 5 and 7 GHz; Figure 5 Fig. 4 shows the three-dimensional scattering diagram of the function reconfigurable stealth superstructure in the cancellation mode at 3, 5 and 7 GHz; Figure 5 Fig. 5 shows the three-dimensional scattering diagram of the ideal metal conductor with the same area at 3, 5 and 7 GHz. DETAILED DESCRIPTION

[0026] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0027] Based on the traditional stealth schemes such as cancellation and absorption, the present application adopts a three-dimensional spatial structure, introduces PIN diodes and DC bias circuits as active control devices in the microwave circuit, and realizes the design of the function reconfigurable stealth superstructure in the cancellation and absorption modes by changing the applied DC bias to control the on-off state of the diode.

[0028] The function reconfigurable electromagnetic superstructure for reducing the radar cross section area comprises a plurality of function subarrays, the arrangement mode of the plurality of function subarrays satisfies the interference cancellation principle to realize the cancellation function, and in specific implementation, the rotationally symmetric arrangement mode can be adopted, that is, the adjacent function subarrays are rotationally symmetric by 90 degrees, or the chessboard mode can be adopted.

[0029] The X-direction dielectric substrate and the Y-direction dielectric substrate are arranged on the metal reflection plate and adopt the bent metal strip as the resonant structure, the PIN diode and the absorption resistor are arranged on the X-direction dielectric substrate in parallel with each other, the PIN diode and the absorption resistor are arranged on the Y-direction dielectric substrate in series with each other, the on-off state of the PIN diode is controlled by the DC bias, the two function state switching of absorption and cancellation is realized in the same frequency band, and the radar cross section area of the target is reduced.

[0030] In order to reduce the complexity of design and facilitate manufacturing, the X-direction medium substrate and the Y-direction medium substrate are three-dimensionally orthogonally nested.

[0031] The X-direction medium substrate is provided with two non-communicating metal strips; the middle section of one metal strip is horizontally distributed, and the two ends are vertically bent downward; the other metal strip is horizontally distributed at the bottom of the substrate as a reflecting ground; the Y-direction medium substrate is provided with one metal strip; the middle section of the metal strip is horizontally distributed, and the two ends are vertically bent downward, and a metal reflecting plate is used as a reflecting ground.

[0032] In order to ensure that the Y-direction metal strip of the unit is disconnected and does not participate in reflection in the cancellation mode, two groups of PIN diodes are used; at the same time, two groups of resistors are arranged to improve the absorption bandwidth of the ground absorption zero point, and the symmetrical arrangement reduces the design complexity. The X-direction medium substrate is connected to two groups of circuits formed by the parallel connection of resistors and PIN diodes; the Y-direction medium substrate is connected to two groups of circuits formed by the series connection of resistors and PIN diodes. The two groups of circuits in the X-direction medium substrate and the Y-direction medium substrate are symmetrically distributed at the horizontal distribution position of the metal strip.

[0033] In order to avoid the influence of direct current circuit on microwave circuit, a number of self-resonant inductors in the working frequency band are used to realize the isolation of in-band DC bias circuit and microwave circuit.

[0034] In the present application, the X-direction medium substrate and the Y-direction medium substrate are printed circuit boards and ceramic substrates; the metal reflecting plate is realized by etching a metal pattern on the substrate covered with metal and using surface mount technology to solder lumped elements.

[0035] The embodiment of the present application provides a functional reconfigurable superstructure for reducing the radar scattering cross section of S and C band targets. Figure 1 As shown in the figure, the two kinds of medium substrates in the unit are orthogonally nested with each other, both of which use downward bent metal strips as resonant structures, the PIN diode and the absorption resistor on the X-direction medium substrate are connected in parallel, and a metal strip structure is used as a reflecting ground; the PIN diode and the absorption resistor on the Y-direction medium substrate are connected in series, and a metal reflecting plate is used as a reflecting ground. When the X-direction resistor is short-circuited and the Y-direction circuit is disconnected, the metal structure reflects X-polarized incident electromagnetic waves, and Y-polarized incident electromagnetic waves are reflected by the ground, and the unit exhibits a 180° phase difference in reflection to different polarized incident electromagnetic waves; when the X-direction and Y-direction resistors are connected to the metal structure at the same time, the unit exhibits absorption characteristics to two different polarized incident electromagnetic waves.

[0036] As shown in the figure,Figure 2 As shown in (a), the functional subarray is composed of 4*4 basic units. Under the condition of destructive interference, the superstructure is obtained by rotational symmetry of the functional subarray about the Z-axis, as follows. Figure 2 As shown in (b), the superstructure dimensions are 128*128*16mm. 3 .

[0037] DC bias circuit such as Figure 2 As shown in (c), the design integrates with the microwave circuit, employing four inductors with self-resonant frequencies of 2.5GHz, 4GHz, 5.5GHz, and 7GHz connected in series to achieve isolation between the DC bias circuit and the microwave circuit; an RF PIN diode is selected as the active switching device. To achieve good absorption matching between the superstructure and spatial electromagnetic waves, the absorption resistor has a resistance of 160Ω. When the DC bias causes the PIN diode on the substrate in the X direction of the unit to be off and the PIN diode on the substrate in the Y direction of the unit to be on, the superstructure exhibits absorption of spatial electromagnetic waves; when the DC bias causes the PIN diode on the dielectric substrate in the X direction of the unit to be on and the PIN diode on the dielectric substrate in the Y direction of the unit to be off, the superstructure exhibits destructive scattering of spatial electromagnetic waves.

[0038] Simulation calculations show that the reconfigurable superstructure has the following geometric parameters: p = 16 mm, h = 16 mm, h1 = 2.2 mm, Δh = 3 mm, l1 = l2 = 13, l3 = 12.8 mm, l4 = 12, d1 = 4 mm, d2 = 1.2 mm, d3 = 4.5 mm, and w = 0.8 mm. The surface electrode pattern of the superstructure is achieved by etching a copper layer on a dielectric substrate with a relative permittivity of 2.2 and a thickness of 0.254 mm.

[0039] The reflection coefficient amplitude and phase curves of this superstructure unit structure in the 1-9 GHz frequency range under two operating modes are as follows: Figure 3 As shown in (a)-(b). When this superstructure operates in absorption mode, as... Figure 3 As shown in (a), the -10dB absorption band of X-polarized electromagnetic waves is 2.3-7.8 GHz, and that of Y-polarized electromagnetic waves is 2.7-8.1 GHz. The anisotropy of the unit structure leads to the difference in the absorption bands of electromagnetic waves with different polarizations, satisfying the requirement of achieving a 10dB monocentric RCS reduction in the overlapping frequency band. When the superstructure operates in destructive mode, the functional subarray exhibits total reflection of both X-polarized and Y-polarized incident electromagnetic waves, as shown in (a). Figure 3 As shown in (b), the two electromagnetic waves exhibit a phase difference of 180°±37° in the 2.3-7.5GHz frequency band. When arranged in a checkerboard pattern, a 10dB single-station RCS reduction can be achieved.

[0040] Because this reconfigurable superstructure is rotationally symmetric in space, it exhibits insensitivity to electromagnetic wave polarization. For example... Figure 4 As shown in (a), the proposed functionally reconfigurable superstructure achieves a significant reduction in RCS compared to metallic reflective surfaces through two functionalities. The relative values ​​of RCS reduction are as follows: Figure 4 As shown in (b), when the superstructure operates in cancellation mode, a 10 dB broadband RCS reduction can be achieved in the 2.40-7.25 GHz frequency band; when the superstructure operates in absorption mode, a 10 dB broadband RCS reduction can be achieved in the 2.53-6.97 GHz frequency band. Compared with existing stealth function switchable research, under the condition that the absorption mode bandwidth is basically similar, the superstructure achieves a 100.5% increase in operating bandwidth in cancellation mode, compared with 16.7% in the prior art, representing a bandwidth increase of 5.01 times; the operating frequency bands of the two stealth functions achieve wide-band overlap, with an overlap rate of 91.5%, compared with 17.1% in the prior art, representing a 4.35 times increase in the overlap rate of the switching frequency bands.

[0041] The three-dimensional scattering patterns of the functionally reconfigurable stealth superstructure at 3, 5, and 7 GHz frequencies in absorption mode are shown below. Figure 5 As shown in (a), the three-dimensional scattering patterns of the destructive mode at 3, 5, and 7 GHz are as follows. Figure 5 As shown in (b), the three-dimensional scattering patterns of an ideal metallic conductor of the same area at frequencies of 3, 5, and 7 GHz are as follows. Figure 5 As shown in (c), a comparison reveals that when the absorption relation is satisfied, the monostatic and bistatic RCS are significantly reduced, indicating that the superstructure absorbs electromagnetic wave energy; when the destructive relation is satisfied, the scattering pattern shows lobes, indicating that the superstructure modulates the spatial distribution of electromagnetic wave energy. That is, this electromagnetic material can operate in two modes, and the operating mode of the superstructure can be controlled by a DC bias voltage.

[0042] Ultimately, by using the functionally reconfigurable superstructure proposed in this invention for reducing the radar cross-section of the target, both broadband stealth of the structure and real-time flexible control of the superstructure's operating mode can be achieved.

[0043] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A function reconfigurable electromagnetic superstructure for radar cross section reduction, characterized in that, The application relates to a radar absorbing structure. The arrangement mode of the multiple groups of functional subarrays meets the interference cancellation principle; the functional subarray comprises multiple groups of periodically arranged basic units; the basic unit comprises an X-direction medium substrate, a Y-direction medium substrate and a metal reflection plate; the X-direction medium substrate and the Y-direction medium substrate are arranged on the metal reflection plate and adopt a bent metal strip as a resonant structure; the X-direction medium substrate is provided with two disconnected metal strips; the middle section of one metal strip is horizontally distributed, and the two ends are vertically bent downward; the other metal strip is horizontally distributed at the bottom of the substrate as a reflection ground; the Y-direction medium substrate is provided with one metal strip; the middle section of the metal strip is horizontally distributed, and the two ends are vertically bent downward; the metal reflection plate is used as a reflection ground; the bent structure in the X direction is lifted and staggered with the Y direction; in order to meet the spacing requirement of the reflection ground and the metal strip in the absorption mode, a horizontal strip is separately arranged in the X direction as a reflection ground structure in the absorption mode; the PIN diode and the absorption resistor are arranged on the X-direction medium substrate in parallel with each other; the PIN diode and the absorption resistor are arranged on the Y-direction medium substrate in series with each other; the switch state of the PIN diode is controlled through a direct current bias, absorption and cancellation two function state switching in the same frequency band are realized, and the target radar scattering cross section area is reduced. The X-direction medium substrate and the Y-direction medium substrate are three-dimensionally orthogonally nested. The X-direction medium substrate is connected with two groups of circuits formed by connecting the resistor and the PIN diode in parallel; the Y-direction medium substrate is connected with two groups of circuits formed by connecting the resistor and the PIN diode in series. The two groups of circuits in the X-direction medium substrate and the Y-direction medium substrate are symmetrically distributed at the horizontal distribution position of the metal strip. A plurality of self-resonant inductors in the working frequency band are connected in series to realize the isolation between the direct current bias circuit and the microwave circuit.

2. The function reconfigurable electromagnetic superstructure for radar cross section reduction of claim 1, wherein, The X-direction medium substrate and the Y-direction medium substrate are printed circuit boards and ceramic substrates.

3. The function reconfigurable electromagnetic superstructure for radar cross section reduction of claim 1, wherein, The metal reflection plate is realized by etching a metal pattern on the substrate covered with metal and welding a surface-mounted component.

4. A function reconfigurable electromagnetic superstructure for radar cross section reduction according to claim 3, characterized in that, ​ 5. A functionally reconfigurable electromagnetic superstructure for radar cross section reduction according to any one of claims 1-4, characterized in that, ​ 6. A functionally reconfigurable electromagnetic superstructure for radar cross section reduction according to any one of claims 1-5, characterized in that, ​ 7. A functionally reconfigurable electromagnetic superstructure for radar cross section reduction according to any of claims 1-6, characterized in that, ​

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