A low-scattering platform in the meter-wave frequency band and its implementation method

Abstract

The present invention belongs to the field of antenna radar scattering technology, and in particular relates to a low-scattering platform in the meter-wave frequency band and a design method thereof. The platform comprises an all-metal aircraft model having P slot structures, P groups of reactance control structures, and a common ground wire. Each group of reactance control structures consists of two varactor diodes and a DC voltage control line. The position of the slot structure is determined by characteristic mode analysis, and the reactance loading value of the reactance control structure is accurately calculated by an optimization algorithm to achieve effective control of the target angular domain scattering field. The present invention can achieve a scattering reduction of at least 30dB relative to a reference platform in the meter-wave frequency band through a scattering control structure that is completely conformal to the platform.

Description

Technical Field

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

[0002] In the field of electromagnetic stealth technology, particularly research on radar cross-section (RCS) reduction, significant progress has been made in the L-band and above. Traditional RCS reduction methods primarily include platform structure optimization, absorbing material loading, and metamaterial loading, and have demonstrated promising results in high-frequency bands. However, the wavelength of electromagnetic waves in the meter-wave band is close to the platform's dimensions, making it difficult for existing local shape optimization techniques to significantly reduce the platform's overall RCS. Furthermore, the absorption efficiency of absorbing materials is typically closely related to the relative wavelength of the electromagnetic waves. In the meter-wave band, even a moderately thick coating of absorbing material on the platform surface not only has limited electromagnetic wave absorption but may also adversely affect the platform's mechanical properties. Similarly, metamaterial loading technology faces similar challenges and cannot effectively address scattering issues in the meter-wave band. Therefore, despite some progress in RCS reduction at higher frequencies (above 1 GHz), effective scattering reduction technologies for the meter-wave band remain relatively scarce. On the other hand, with recent breakthroughs in key areas such as meter-wave radar coverage, measurement accuracy, and anti-interference, the strategic significance of electromagnetic stealth technology in the meter-wave band has become increasingly prominent in modern warfare. This has made stealth technology in the meter-wave band a key and challenging area of ​​current research.

[0003] In the meter-wave band, the electrical dimensions of a platform are comparable to its wavelength. Therefore, optimizing its resonant characteristics in this band becomes an intuitive approach to scattering control. In the 1970s, Harrington et al. proposed a radar cross-section (RCS) control technique based on impedance loading and demonstrated that reactance loading can achieve resonance of arbitrary real currents or isophase currents on the target surface. However, this method requires reactance loading on each basis function to meet strict equality constraints, which is difficult to implement in practical applications. Some studies have proposed applying impedance loading at sparse locations to achieve RCS control. For example, in the paper "Radar cross section reduction using characteristic mode analysis," the authors qualitatively load impedance elements at locations with strong scattering currents, achieving scattering control for a simple cylinder. However, the impedance loading values ​​in this method were not quantitatively optimized, resulting in relatively limited scattering cross-section reduction. Additionally, some researchers have proposed using active cancellation 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 prior knowledge of the amplitude and phase of the incoming signal, and thus relies on highly complex hardware and software systems, which poses great challenges in practical applications and limits its widespread use.

[0004] Currently, existing research and technical solutions for reducing scattering in the meter-wave band all suffer from the aforementioned problems. Therefore, developing a new method for reducing scattering in the meter-wave band is particularly important. To address these technical challenges, this paper proposes a design method for a low-scattering platform in the meter-wave band based on sparse reactance loading. This method uses an optimization algorithm to accurately determine the reactance loading value, thereby effectively controlling scattering and providing a novel and efficient solution. Summary of the Invention

[0005] The technical solutions for achieving the purpose of the present invention are:

[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 scattered current at the corresponding position; 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 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 the DC voltage control line (7);

[0008] The effective capacitance 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 part 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 It represents the load value to be optimized. The input voltage values ​​of the P DC voltage control lines can be obtained according to the mapping function of the effective capacitance value of the varactor diode and the bias voltage.

[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 aircraft surface through 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 30dB. 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 paying any 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 3. 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 clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiment is only one embodiment of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0021] Combine Figure 1 ,The reference platform adopts an all-metal structure with a size of 9.6 m × 6.0 m × 0.9 m, ,including three parts: fuselage, main wing and tail wing. ,First, the scattering reduction optimization target is determined to be 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 was performed on the reference platform structure at 80 MHz, 100 MHz, and 120 MHz to obtain the characteristic modes and current distribution at 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 pattern, identify the local maximum current area, and further determine the common position of these areas as the loading position of the slot structure; Figure 2 The local maximum current regions of each mode are marked in the figure. To achieve broadband scattering control using only a small number of loading structures, the common regions of the local maximum current of these scattering modes are selected as the loading locations for the slot structure and varactor diode, thereby constructing the proposed low-scattering platform in the meter-wave frequency band.

[0026] Combine Figure 3 The low-scattering platform in the meter-wave frequency band includes an aircraft model (1) of an all-metal structure, 8 slot structures (2), 8 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) includes a varactor diode 1 (5) and 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 a DC 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 8 DC 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 part 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 superscript T represents the transpose operator. 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 8 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 It is z L The i-th element, z opt,p It is z opt The pth element of , 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 and the reverse bias voltage based on the selected varactor diode model. In this example, the diode models SMV1247-SMV1255 are considered. By consulting the specifications and characteristic curves of the diodes, the mapping relationship between their effective capacitance and reverse bias voltage can be established.

[0042] In the second step, the DC voltage output values ​​of the eight DC voltage sources are determined using this mapping relationship, and the loading states are adjusted accordingly.

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

[0044] The foregoing description of the present invention and its embodiments is provided for the benefit of those skilled in the art. Such description should be construed as illustrative rather than restrictive. Engineers and technicians may implement the concepts set forth in the appended claims and may also make a variety of modifications to the embodiments described above. All of the foregoing should be considered within 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) includes 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 the common ground line (4); The scattering reduction of the low-scattering platform in the meter-wave frequency band is 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 the DC voltage control line (7).

2. A method for implementing a low-scattering platform in the meter-wave frequency band according to claim 1, characterized in that: It includes a method for determining the loading position of the slot structure, a method for determining the reactance loading value, and a method for determining the input voltage value of the DC voltage control line; The method for determining the loading position of the slot structure is based on characteristic mode analysis and includes: The first step is to perform characteristic mode analysis on the reference platform at the set frequency to obtain the characteristic mode 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 pattern, identify the local maximum current area, 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 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 part 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 superscript T represents the transpose operator. The unconstrained optimization problem is converted into a standard iterative optimization process. For the k+1th 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 It is z L The i-th element, z opt,p It is z opt The pth element of , 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+1th iteration A vector consisting of the first N elements of is obtained at the k+1th iteration The vector composed of the last N elements of , and finally the P-dimensional variable obtained by the Kth time Get the required loading value; The method for determining the input voltage value of the DC voltage control line includes: The first step is to establish a mapping relationship between the effective capacitance value and the reverse bias voltage according to the model of the selected varactor diode; 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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