Meter-wave frequency band low-scattering platform and implementation method thereof

Abstract

The invention belongs to the technical field of antenna radar scattering, and particularly relates to a meter-wave frequency band low-scattering platform and a design method thereof. The platform comprises an all-metal aircraft model which is provided with P groove structures, P groups of reactance regulation and control structures and a common ground wire. And each group of reactance regulation and control structure consists of two variable capacitance diodes and one direct-current voltage control line. The position of the groove structure is determined through characteristic mode analysis, and the reactance loading value of the reactance regulation and control structure is accurately calculated through an optimization algorithm, so that effective regulation and control of a target angular domain scattered field are realized. According to the invention, scattering reduction of at least 30dB relative to a reference platform can be realized in a meter-wave frequency band through the scattering regulation and control structure which is completely conformal with the platform.

Description

Technical Field

[0001] The present invention belongs to the technical field of antenna radar scattering, and in particular relates to a meter-wave frequency band low-scattering platform and a realization method thereof. Background Art

[0002] In the field of electromagnetic stealth technology, especially in the research of radar cross section (RCS) reduction technology, significant progress has been made in the technology for L-band and above frequency bands. Traditional scattering cross section reduction methods mainly include platform structure optimization, absorbing material loading and metamaterial loading, and have shown good results in high frequency bands. However, the wavelength of electromagnetic waves in the meter-wave band is close to the size of the platform, which makes it difficult for existing local shape optimization technologies to significantly reduce the overall radar cross section of the platform. In addition, the absorption effect of absorbing materials is usually closely related to the relative wavelength of electromagnetic waves. In the meter-wave band, the appropriate thickness of absorbing materials covering the surface of the platform not only has limited absorption effect on electromagnetic waves, but may also have an adverse effect on the mechanical properties of the platform. Similarly, metamaterial loading technology also faces similar challenges and cannot effectively solve the scattering problem in the meter-wave band. Therefore, although there has been some research progress in scattering cross section reduction technology in higher frequency bands (above 1GHz), effective scattering reduction technology for the meter-wave band is still relatively scarce. On the other hand, with the effective breakthroughs of meter-wave radar in key issues such as spatial coverage, measurement accuracy, and anti-interference in recent years, the strategic significance of electromagnetic stealth technology in the meter-wave frequency band in modern warfare has become increasingly prominent. This makes stealth technology in the meter-wave frequency band a key and difficult area of ​​current research.

[0003] In the meter-wave band, the electrical size of the platform is comparable to the wavelength, so optimizing the resonant characteristics of the platform in the meter-wave band becomes an intuitive scattering control method. In the 1970s, Harrington et al. proposed a radar cross section (RCS) control technology based on impedance loading, and proved that reactance loading can achieve resonance of any real current or equal-phase current on the surface of the target body. However, this method in the literature requires reactance loading on each basis function to meet strict equality constraints, which is difficult to achieve in practical applications. Some studies have proposed impedance loading at sparse locations to achieve radar cross section control. For example, in the literature "Radar cross section reduction using characteristic mode analysis", the authors qualitatively loaded impedance elements at locations with strong scattering currents, thereby achieving scattering control of simple cylinders. However, the impedance loading value in this method has not been quantitatively optimized, resulting in a relatively limited reduction effect on the scattering cross section. In addition, some researchers have proposed using active cancellation methods to achieve scattering reduction in the meter-wave band, as described in "Active cancellation of bistatic radar cross section of large aircraft using conformal 4-port magnetic antenna". However, this method requires the amplitude and phase of the incoming signal to be known in advance, and thus relies on highly complex hardware and software systems, which poses great challenges in practical applications and limits its widespread application.

[0004] At present, the existing research or technical solutions for reducing scattering in the meter-wave band have the above problems. Therefore, it is particularly important to develop a new method for reducing scattering in the meter-wave band. In order to solve these technical problems, the present invention proposes a design method for a low-scattering platform in the meter-wave band based on sparse reactance loading. The method accurately determines the reactance loading value through an optimization algorithm, thereby achieving effective control of scattering, providing a novel and efficient solution. Summary of the invention

[0005] The technical solution to achieve the purpose of the present invention is:

[0006] A low-scattering platform in the meter-wave frequency band comprises an aircraft model (1) of an all-metal structure, P slot structures (2), P groups of reactance control structures (3) and a common ground line (4), wherein P is an integer; the position of the slot is determined based on characteristic mode analysis to control the scattering current at the corresponding position; each group of reactance control structures (3) comprises a varactor diode 1 (5) and a varactor diode 2 (6) and a direct current voltage control line (7); the left terminal (8) of each slot structure is connected to the positive electrode (10) of the varactor diode 1 (5); the right terminal (9) of each slot structure is connected to the positive electrode (11) of the varactor diode 2 (6); the negative electrode (12) of the varactor diode (1) and the negative electrode (13) of the varactor diode (2) are simultaneously connected to the direct current voltage control line (7); the aircraft model (1) is connected to the common ground line (4);

[0007] The scattering reduction of the low-scattering platform in the meter-wave frequency band can be controlled by changing the effective capacitance value of the varactor diode 1 (5) and the varactor diode 2 (6); the effective capacitance value of the varactor diode 1 (5) and the varactor diode 2 (6) is adjusted by a DC voltage control line (7);

[0008] The effective capacitance value of the varactor diode can be determined by the following optimization problem,

[0009]

[0010] in represents the N-dimensional real number field, ||·|| 2 represents the L2 norm, represents the 2N-dimensional real number field, and represents the real and imaginary operators, the matrix E is the field matrix in the target frequency and target angle domain calculated by the unit RWG basis function, the vector I is the surface scattered current to be optimized, V is the excitation vector determined by the incident field, diag(·) represents the construction of the diagonal matrix operator, z L represents the loading value to be optimized. According to the mapping function of the effective capacitance value of the varactor diode and the bias voltage, the input voltage value of the P DC voltage control lines can be obtained.

[0011] Compared with the prior art, the present invention has the following notable features:

[0012] (1) The low-scattering platform in the meter-wave frequency band proposed in the present invention can effectively achieve scattering reduction in the meter-wave frequency band, regulate the scattering current on the surface of the aircraft by reactance loading, and the scattering reduction structure is completely conformal to the platform, thereby avoiding damage to the aerodynamic characteristics of the aircraft and ensuring the feasibility and performance of the platform in practical applications.

[0013] (2) Different from other impedance loading or reactance loading methods, the present invention proposes a scattering control strategy based on sparse loading and combines it with an accurate loading value optimization method. This innovative loading strategy has significant advantages in feasibility and scattering reduction effect.

[0014] (3) Based on the system architecture and control methods proposed in the present invention, a significant reduction in scattering can be achieved at the target frequency, and the scattering reduction effect of the platform in the meter-wave frequency band can reach greater than 30 dB. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the implementation cases of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only one embodiment of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0016] Figure 1 Schematic diagram of the reference platform structure in the embodiment.

[0017] Figure 2 : is the current distribution of the scattering mode of the reference platform at different frequencies in the embodiment.

[0018] Figure 3 Schematic diagram of the structure of the low-scattering platform in the meter-wave frequency band proposed in the embodiment.

[0019] Figure 4 4 is a comparison diagram of the single-station radar cross section of the low-scattering platform proposed in the embodiment and the reference platform. Specific implementation plan

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiment is only one embodiment of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] Combination Figure 1 ,The reference platform adopts an all-metal structure with a size of 9.6 m × 6.0 m × 0.9 m, and consists of three parts: fuselage, main wing and tail wing. Firstly, the scattering reduction optimization target is determined to be from 80 MHz to 120 MHz, and the angle of the incident wave is (0.0°, 90.0°). The position and loading value of the reactance loading are obtained according to the following steps.

[0022] First, determine the loading location based on characteristic mode analysis:

[0023] In the first step, characteristic mode analysis is performed on the reference platform structure at 80MHz, 100MHz and 120MHz to obtain the characteristic modes and current distribution of each frequency;

[0024] The second step is to determine the scattering mode with the greatest impact on the radar cross section based on the contribution of each mode to the scattering;

[0025] The third step is to analyze the current distribution of the above scattering mode, identify the local maximum current area therein, and further determine the common position of these areas as the loading position of the slot structure; Figure 2 The local maximum current area of ​​each mode is marked in the figure; in order to achieve broadband scattering control using only a small number of loading structures, the common area of ​​the local maximum current of these scattering modes is selected as the loading position of the slot structure and the varactor diode, thereby constructing the proposed low-scattering platform in the meter-wave frequency band;

[0026] Combination Figure 3 The low-scattering platform in the meter-wave frequency band comprises an aircraft model (1) of an all-metal structure, eight slot structures (2), eight groups of reactance control structures (3) and a common ground line (4); the position of the slot is determined according to the characteristic mode analysis result, so as to control the scattering current at the corresponding position; each group of reactance control structures (3) comprises a varactor diode 1 (5) and a varactor diode 2 (6) and a direct current voltage control line (7); the left terminal (8) of each slot structure is connected to the positive electrode (10) of the varactor diode 1 (5); the right terminal (9) of each slot structure is connected to the positive electrode (11) of the varactor diode 2 (6); the negative electrode (12) of the varactor diode (1) and the negative electrode (13) of the varactor diode (2) are simultaneously connected to a direct current voltage control line (7); the aircraft model (1) is connected to the common ground line (4); the scattering reduction effect of the platform in the meter-wave frequency band is achieved by changing the input voltage of the eight direct current voltage control lines; the input voltage value is determined by the capacitance loading value calculated by the optimization algorithm;

[0027] The reactance loading value is determined according to the following steps:

[0028] The first step is to establish an optimization problem about minimizing the scattered field at the target angle based on the relationship between the reactance loading value and the scattered field.

[0029]

[0030] in represents the N-dimensional real number field, N is the number of RWG basis functions, ||·|| 2 represents the L2 norm, represents the 2N-dimensional real number field, and represents the real and imaginary operators, the matrix E is the field matrix in the target frequency and target angle domain calculated by the unit RWG basis function, the vector I is the surface scattered current to be optimized, V is the excitation vector determined by the incident field, diag(·) represents the construction of the diagonal matrix operator, z L Indicates the load value to be optimized;

[0031] The second step is to introduce the augmented Lagrangian function to transform the original optimization problem into an unconstrained optimization problem.

[0032]

[0033] Where u represents the multiplication factor, ρ represents the penalty parameter, and the superscript T represents the transposition operator. Further based on the augmented Lagrangian function The unconstrained optimization problem is converted into a standard iterative optimization process. For the (k+1)th iteration, the variables are updated as follows:

[0034]

[0035] In the third step, since eight loading positions have been determined, the N-dimensional variable z L The optimization is converted into an 8-dimensional variable z opt The optimization problem z L With z opt The relationship is as follows,

[0036]

[0037] where C is a set of indices of loading positions obtained by eigenmode analysis, z L,i Yes L The i-th element of opt,p Yes opt The pth element of , while taking into account the actual implementation, constrains the capacitance value to be within a given maximum value z max and the minimum value z min Optimize within the range of The optimization step becomes:

[0038]

[0039] in is obtained at the (k+1)th iteration A vector consisting of the first N elements of is obtained at the (k+1)th iteration The vector composed of the last N elements of , and finally the 8-dimensional variable obtained by the Kth time Get the required loading value;

[0040] Finally, determine the input voltage value of the DC voltage control line:

[0041] The first step is to establish a mapping relationship between the effective capacitance value and the reverse bias voltage according to the selected varactor diode model. In this example, the diode model SMV1247-SMV1255 is considered. By referring to the specification parameters and characteristic curve of the diode, the mapping relationship between its effective capacitance value and the reverse bias voltage can be established;

[0042] In the second step, the DC voltage output values ​​of the 8-way DC voltage sources are determined using this mapping relationship, and each loading state is adjusted accordingly.

[0043] Figure 4 The comparison results of the proposed low-scattering platform and the reference platform in single-station radar cross section (RCS) are shown. It can be seen from the figure that in the frequency band range of 84MHz to 120MHz, by adjusting different loading states, a radar cross section reduction of at least 30dB relative to the reference platform can be achieved at the target frequency. This result shows that by optimizing the reactance loading and adjusting the loading state, the electromagnetic stealth performance of the platform in the meter-wave frequency band has been significantly improved.

[0044] The above is a description of the present invention and its implementation scheme provided to engineers and technicians familiar with the field of the present invention. These descriptions should be regarded as illustrative rather than restrictive. Engineers and technicians can make specific operations based on the ideas in the claims of the invention, and naturally can make a series of changes to the implementation scheme based on the above. All of the above should be regarded as the scope of the present invention.

Claims

1. A low-scattering platform in the meter-wave frequency band, characterized in that: It includes an aircraft model (1) with an all-metal structure, P slot structures (2), P groups of reactance control structures (3) and a common ground wire (4), wherein P is an integer; Each group of reactance control structures (3) comprises a varactor diode 1 (5), a varactor diode 2 (6) and a DC voltage control line (7); the left terminal (8) of each slot structure is connected to the positive electrode (10) of the varactor diode 1 (5); the right terminal (9) of each slot structure is connected to the positive electrode (11) of the varactor diode 2 (6); the negative electrode (12) of the varactor diode (1) and the negative electrode (13) of the varactor diode (2) are simultaneously connected to the DC voltage control line (7); the aircraft model (1) is connected to a common ground line (4); The scattering reduction of the low-scattering platform in the meter-wave frequency band can be controlled by changing the effective capacitance value of the varactor diode 1 (5) and the varactor diode 2 (6); the effective capacitance value of the varactor diode 1 (5) and the varactor diode 2 (6) is adjusted by a DC voltage control line (7).

2. A method for realizing a low-scattering platform in a meter-wave frequency band as claimed in claim 1, characterized in that: It includes a method for determining a slot structure loading position, a method for determining a reactance loading value, and a method for determining an input voltage value of a DC voltage control line; The method for determining the loading position of the slot structure is implemented based on characteristic mode analysis, and includes: In the first step, characteristic mode analysis is performed on the reference platform at the set frequency to obtain the characteristic modes and current distribution of each frequency; The second step is to determine the scattering mode with the greatest impact on the radar cross section based on the contribution of each mode to the scattering; The third step is to analyze the current distribution of the above scattering mode, identify the local maximum current area therein, and further determine the common position of these areas as the loading position of the slot structure; The method for determining the reactance loading value is implemented based on an iterative optimization algorithm, and includes: The first step is to establish an optimization problem about minimizing the scattered field at the target angle based on the relationship between the reactance loading value and the scattered field. in represents the N-dimensional real number field, N is the number of RWG basis functions, ||·||2 represents the L2 norm, represents the 2N-dimensional real number field, and represents the real and imaginary operators, the matrix E is the field matrix in the target frequency and target angle domain calculated by the unit RWG basis function, the vector I is the surface scattered current to be optimized, V is the excitation vector determined by the incident field, diag(·) represents the construction of the diagonal matrix operator, z L Indicates the load value to be optimized; The second step is to introduce the augmented Lagrangian function to transform the original optimization problem into an unconstrained optimization problem. Where u represents the multiplication factor, ρ represents the penalty parameter, and the superscript T represents the transposition operator. Further based on the augmented Lagrangian function The unconstrained optimization problem is converted into a standard iterative optimization process. For the (k+1)th iteration, the variables are updated as follows: The third step is to transform the N-dimensional vector z L The optimization is converted into a P-dimensional vector z opt Optimization problem, P is much smaller than N, z L With z opt The relationship is as follows, where C is a set of indices of loading positions obtained by eigenmode analysis, z L,i Yes L The i-th element of opt,p Yes opt The pth element of , while taking into account the actual implementation, constrains the capacitance value to be within a given maximum value z max and the minimum value z min Optimize within the range of The optimization step becomes, in is obtained at the (k+1)th iteration A vector consisting of the first N elements of is obtained at the (k+1)th iteration The vector composed of the last N elements of , and finally the P-dimensional variable obtained for the Kth time Get the required loading value; The method for determining the input voltage value of the DC voltage control line comprises: The first step is to establish a mapping relationship between the effective capacitance value and the reverse bias voltage according to the selected varactor diode model; The second step is to determine the DC voltage output value of the P-way DC voltage source and adjust the loading state.

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