A four-component decomposition method suitable for ship target scattering characteristics

Abstract

The application discloses a four-component decomposition method suitable for ship target scattering characteristics, and comprises the following steps: S1, analyzing a ship structure to obtain volume scattering and helical scattering components for describing irrationality of the ship structure; S2, according to structure characteristics of the ship, using a +45 dipole component to describe a linear polarization scatterer on the ship, and using an asymmetric scattering component to describe an asymmetric scattering structure on the ship; S3, using mirror surface scattering, double-hop scattering, the +45 dipole component and the asymmetric scattering component to obtain a four-component decomposition model suitable for ship scattering characteristics; and S4, obtaining scattering characteristics of a target ship according to the four-component decomposition model. The +45 directional dipole and the non-reflection asymmetric scattering component can reasonably describe scattering structures on the ship, and can effectively increase an inter-class distance between the ship and clutter, so that the target can be detected from the sea clutter.

Description

Technical Field

[0001] This invention relates to the field of synthetic aperture radar target detection and recognition technology, and more specifically, to a four-component decomposition method applicable to the scattering characteristics of ship targets. Background Technology

[0002] Synthetic Aperture Radar (SAR), with its unique advantages of all-weather, all-day, and continuous observation, is widely used in military and civilian fields. SAR backscattering information contains rich polarization information, reflecting the target's geometry and physical characteristics, and can fully characterize the target's scattering properties. In PolSAR data target information extraction, target decomposition is a commonly used and highly effective method. It represents the average scattering mechanism of the target as the sum of independent scattering mechanisms, thus associating each resolution cell with its corresponding physical scattering mechanism, thereby separating the scattering mechanism in the target's polarization features for classification and identification. Decomposition methods include those based on the scattering matrix, the Kennaugh matrix, and those based on covariance or coherence matrices. Among these, decomposition based on covariance or coherence matrices is the most widely used. These methods typically assume the existence of a scatterer within the scattering target and derive different scattering models based on different scatterers.

[0003] Maritime target detection is an important topic in Earth observation research, and various ship detection algorithms have emerged. However, few studies have explored applying model-based scattering characteristic decomposition algorithms to ships, and existing model-based polarization decomposition algorithms primarily focus on terrestrial vegetation and urban areas, with few specifically targeting maritime targets. Due to the differences between man-made targets and terrestrial vegetation or urban areas, applying existing model-based polarization decomposition methods to maritime targets presents the following problems: 1) Volume scattering models are not suitable for maritime ships. Volume scattering models are used to describe dense random dipoles, such as tree canopy regions. As is well known, the structural outlines of various components on ships are clear, especially on flat-surfaced vessels such as aircraft carriers or container ships; random dipole clouds resembling tree canopy structures do not exist on such ships; 2) Existing scattering models do not adequately represent ship targets. The ship target has a neat structure, and the edges of the ship's outline, mast, doors and windows, and container edges should exhibit a linear polarization effect. Existing four-component decomposition models do not correctly describe these structures. 3) Besides the specular scattering model, the other three components should correctly characterize the ship; that is, we should be able to distinguish the ship target using only a single component. However, in the actual decomposition process, we found that in the spiral scattering model, the ship's spiral scattering power value is zero, making it impossible for the human eye to distinguish the ship on this power map.

[0004] Therefore, there is an urgent need for a four-component decomposition method applicable to the scattering characteristics of ship targets to reasonably describe the scatterers on ships. Summary of the Invention

[0005] The purpose of this invention is to provide a four-component decomposition method applicable to the scattering characteristics of ship targets, so as to overcome the defects of the existing technology.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A four-component decomposition method applicable to the scattering characteristics of ship targets includes the following steps:

[0008] S1. Analyze the ship structure to obtain the volume scattering and helical scattering components used to describe the irrationality of the ship structure;

[0009] S2. Based on the structural characteristics of the ship, the linearly polarized scattering body on the ship is described by the ±45° dipole component, and the asymmetric scattering structure on the ship is described by the asymmetric scattering component.

[0010] S3. A four-component decomposition model suitable for ship scattering characteristics is obtained by using mirror scattering, double-hop scattering, ±45° dipole components and asymmetric scattering components.

[0011] S4. The scattering characteristics of the target ship are obtained based on the four-component decomposition model.

[0012] Further, step S3 includes:

[0013] S30. Use specular scattering and double-hop scattering components to describe the odd and even scattering components on a ship.

[0014] S31. Use ±45° dipole components to describe the linearly polarized scatterers on a ship;

[0015] S32. Describe the asymmetric scattering structure on a ship using asymmetric scattering components;

[0016] S33. Based on the specular scattering component, double-hop scattering component, ±45° dipole component, and asymmetric scattering component, a four-component decomposition model suitable for ship scattering characteristics is obtained.

[0017] Further, step S30 includes:

[0018] The scattering matrix of the specular scattering component can be expressed as:

[0019]

[0020]

[0021] The scattering matrix of the double-hop scattering component can be expressed as:

[0022]

[0023]

[0024] In the formula, Let k represent the mirror scattering matrix. p Let [T] denote the specular scattering vector under Paulige conditions. s The coherence matrices β and β' represent the specular scattering. * Denotes the coefficients to be determined. Let k represent the double-hop scattering matrix. p Let [T] denote the double-hop scattering vector under Paulige conditions. d Let α and α' represent the coherence matrices of double-hop scattering. * This represents the coefficient to be determined.

[0025] Further, the ±45° dipole component in step S31 is expressed as:

[0026]

[0027] In the formula, Re represents the operation of taking the real part. k represents the scattering matrix of a 45° dipole. p This represents the scattering vector of a 45° dipole. The coherence matrix representing a 45° dipole. This represents the scattering matrix of a -45° dipole. The coherence matrix represents the -45° dipole.

[0028] Furthermore, the asymmetric scattering component in step S32 is described as follows:

[0029]

[0030] In the formula, [S Asym ] represents the scattering matrix of the asymmetric scattering component, and γ and ρ represent the ratios of the backscattering coefficients of HH and HV to the backscattering coefficients of VV, respectively.

[0031] The coherence matrix of the non-reflection symmetric scattering model can be expressed as:

[0032]

[0033] In the formula, T Asym The coherence matrix represents the asymmetric scattering component.

[0034] Furthermore, the four-component decomposition model in step S33 is as follows:

[0035]

[0036]

[0037] In the formula, [T] represents the total coherence matrix, f s f d f Od f Asym T represents the expansion coefficient. ij Let i,j = 1,2,3 represent the elements corresponding to the coherence matrix [T].

[0038] Further, step S4 includes:

[0039] The power of the ±45° oriented dipole is Solve for f Asym Then, using the existing four-component solution approach, we can solve for the remaining components.

[0040] The power values ​​of surface scattering, double-hop scattering, ±45° directional dipole scattering, and non-reflective symmetric scattering can be expressed as:

[0041]

[0042] Compared with the prior art, the advantages of the present invention are as follows: The present invention provides a four-component decomposition method applicable to the scattering characteristics of ship targets. By utilizing ±45° directional dipoles and non-reflective symmetric scattering components, the scattering structure on the ship can be reasonably described, and the interclass distance between the ship and clutter can be effectively increased, which is beneficial for detecting targets from sea clutter. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a diagram illustrating the scattering characteristics of ships in this invention.

[0045] Figure 2 These are four scattering component diagrams applied to the scattering characteristics of ships.

[0046] Figure 3 This is a flowchart of the algorithm of the present invention.

[0047] Figure 4 This is a qualitative analysis of the spiral scattering component in the existing four-component decomposition model and the asymmetric scattering component in this invention.

[0048] Figure 5 It is a measure of the distance between different decomposition model classes. Detailed Implementation

[0049] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0050] See Figure 1 As shown in the figure, the ship's overall outline, window sills, container edges, hull components, and mast are all linear scatterers, exhibiting linear polarization response. The ±45° directional dipole component describes the linear scatterer at a 45° angle to the radar line of sight; therefore, using the ±45° directional dipole component to describe the linearly polarized scatterers on the ship is reasonable. Furthermore, due to the complexity of man-made structures, different scatterers produce different scattering mechanisms, and using only the helical scattering component to describe the asymmetric scattering characteristics of the ship is incomplete. Therefore, this invention introduces an asymmetric scattering component to characterize the ship's asymmetric scattering information. This overcomes the limitations of the helical scattering mechanism and fully describes the asymmetric scatterers on the ship using all elements of the coherence matrix.

[0051] See Figure 2 and Figure 3 As shown, this embodiment discloses a four-component decomposition method applicable to the scattering characteristics of ship targets, including the following steps:

[0052] Step S1: Analyze the ship structure to obtain the volume scattering and spiral scattering components used to describe the irrationality of the ship structure.

[0053] Step S2: Based on the structural characteristics of the ship, the linearly polarized scatterers on the ship are described using the ±45° dipole component, and the asymmetric scattering structure on the ship is described using the asymmetric scattering component.

[0054] Specifically, the scattering structure on the ship was further analyzed, and the rationale for using ±45° dipole components to describe the linearly polarized scatterers on the ship was explained.

[0055] A thorough analysis of the scattering characteristics of ship structures reveals that the overall outline of the ship, window sills, container edges, hull component outlines, and masts are all linear scatterers exhibiting linear polarization responses. When applying existing four-component decomposition models to ships, the volume scattering component cannot effectively describe the ship's scattering characteristics. Due to the ship's regular geometric structure, it exhibits more linear polarization responses, and random dipole clouds resembling tree canopies are absent on ships. Therefore, using the ±45° dipole component to describe the scattering structure on a ship is more reasonable than using the volume scattering component.

[0056] The limitations of using helical scattering components to describe asymmetric scatterers on ships are analyzed in depth, and the effectiveness of using asymmetric scattering components to describe asymmetric scatterers on ships is reasonably explained.

[0057] Specifically, when applying the helical scattering component to ships, it was found that ships could not be identified by the human eye on the helical scattering power map. Due to the complexity of man-made structures, different scatterers produce different scattering mechanisms, and it is incomplete to use only helical scattering to describe the asymmetric scattering characteristics of ships.

[0058] Step S3: Using specular scattering, double-hop scattering, ±45° dipole components, and asymmetric scattering components, a four-component decomposition model suitable for ship scattering characteristics is obtained. Specifically, it includes:

[0059] Step S30: Use the specular scattering component and the double-hop scattering component to describe the odd and even scattering components on the ship.

[0060] Specifically, the scattering matrix of the specular scattering component can be expressed as:

[0061]

[0062]

[0063] Specifically, the scattering matrix of the double-hop scattering component can be expressed as:

[0064]

[0065]

[0066] In the formula, Let k represent the mirror scattering matrix. p Let [T] denote the specular scattering vector under Paulige conditions. s The coherence matrices β and β' represent the specular scattering. * This represents the coefficient to be determined. Let k represent the double-hop scattering matrix. p Let [T] denote the double-hop scattering vector under Paulige conditions. dLet α and α' represent the coherence matrices of double-hop scattering. * This represents the coefficient to be determined.

[0067] Step S31: Use the ±45° dipole component to describe the linearly polarized scatterers on the ship.

[0068] Specifically, the scattering characteristics of a directional dipole are highly dependent on the target orientation relative to the polarized coordinate system. This behavior is exhibited when the target contains dipoles pointing at ±45°. Combining the scattering matrix of the odd-hop reflector (plate) with the scattering matrix of the ±45° dihedron yields a composite directional dipole scattering matrix:

[0069]

[0070] In the formula, Re represents the operation of taking the real part. k represents the scattering matrix of a 45° dipole. p This represents the scattering vector of a 45° dipole. The coherence matrix representing a 45° dipole. This represents the scattering matrix of a -45° dipole. The coherence matrix represents the -45° dipole.

[0071] Step S32: Describe the asymmetric scattering structure on the ship using asymmetric scattering components.

[0072] Specifically, due to the complexity of asymmetric scattering, there is no precise mathematical model to describe it. The general form of the asymmetric scattering components is typically used, and its definition is as follows:

[0073]

[0074] In the formula, [S Asym ] represents the scattering matrix of the asymmetric scattering component, and γ and ρ represent the ratios of the backscattering coefficients of HH and HV to the backscattering coefficients of VV, respectively.

[0075] The coherence matrix of the non-reflection symmetric scattering model can be expressed as:

[0076]

[0077] In the formula, T Asym The coherence matrix represents the asymmetric scattering component.

[0078] Step S33: Based on the specular scattering component, double-hop scattering component, ±45° dipole component, and asymmetric scattering component, obtain a four-component decomposition model suitable for ship scattering characteristics.

[0079] Specifically, by using surface scattering, double-hop scattering, ±45° oriented dipoles, and asymmetric scattering components to describe all scattering structures on the ship, a four-component decomposition model based on the coherence matrix can be obtained as follows:

[0080]

[0081]

[0082] In the formula, [T] represents the total coherence matrix, f s f d f Od f Asym T represents the expansion coefficient. ij Let i,j = 1,2,3 represent the elements corresponding to the coherence matrix [T].

[0083] Step S4: Obtain the scattering characteristics of the target ship based on the four-component decomposition model.

[0084] Specifically, firstly, the power of the ±45° oriented dipole is Then, solve for f. Asym Using the existing four-component solution approach, we solve for the remaining components, that is, if a certain pixel's... View α = 0, because when This means that surface scattering is dominant in this region; if a pixel contains When β = 0, because when This means that double-hop scattering is dominant in this region. Therefore, the remaining four unknowns can be solved.

[0085] The power values ​​for surface scattering, double-hop scattering, ±45° directional dipole scattering, and non-reflective symmetric scattering can be expressed as:

[0086]

[0087] To further illustrate the advantages of this invention, a qualitative analysis is performed on the asymmetric scattering component in the decomposition model of this invention and the spiral scattering component in other decomposition models. From Figure 4 As can be seen, in the decomposition models BF4, Y4O, Y4R, and S4R, the human eye cannot accurately determine whether the area pointed to by the red arrow on the helical scattering power map is a ship. However, in the asymmetric scattering component power map of this invention, this area appears as a bright spot, revealing the outline features of a ship.

[0088] Quantitative evaluation of the inter-class distances of ships and sea clutter under different decomposition models. Figure 5As can be seen, in this invention, the center distance between the ship and clutter categories is greater. This means that when detecting ships, it is easier to detect them from sea clutter.

[0089] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, the patent owner may make various modifications or alterations within the scope of the appended claims, as long as they do not exceed the protection scope described in the claims of the present invention, they shall be within the protection scope of the present invention.

Claims

1. A four-component decomposition method applicable to the scattering characteristics of ship targets, characterized in that, Includes the following steps: S1. Analyze the ship structure to obtain the volume scattering and helical scattering components used to describe the irrationality of the ship structure; S2. Based on the structural characteristics of the ship, the linearly polarized scattering body on the ship is described by the ±45° dipole component, and the asymmetric scattering structure on the ship is described by the asymmetric scattering component. S3. A four-component decomposition model suitable for ship scattering characteristics is obtained by using mirror scattering, double-hop scattering, ±45° dipole components and asymmetric scattering components. S4. The scattering characteristics of the target ship are obtained based on the four-component decomposition model. The ±45° dipole component is represented as: In the formula, Re represents the operation of taking the real part. k represents the scattering matrix of a 45° dipole. p This represents the scattering vector of a 45° dipole. The coherence matrix representing a 45° dipole. This represents the scattering matrix of a -45° dipole. Let T denote the coherence matrix of the -45° dipole, and let T denote the total coherence matrix. 13 This represents the element corresponding to the coherence matrix T.

2. The four-component decomposition method for the scattering characteristics of ship targets according to claim 1, characterized in that, Step S3 includes: S30. Use specular scattering and double-hop scattering components to describe the odd and even scattering components on a ship. S31. Use ±45° dipole components to describe the linearly polarized scatterers on a ship; S32. Describe the asymmetric scattering structure on a ship using asymmetric scattering components; S33. Based on the specular scattering component, double-hop scattering component, ±45° dipole component, and asymmetric scattering component, a four-component decomposition model suitable for ship scattering characteristics is obtained.

3. The four-component decomposition method for the scattering characteristics of ship targets according to claim 2, characterized in that, Step S30 includes: The scattering matrix of the specular scattering component is expressed as: The scattering matrix of the double-hop scattering component is expressed as: In the formula, Let k represent the mirror scattering matrix. p Let [T] denote the specular scattering vector under Paulige conditions. s The coherence matrices β and β' represent the specular scattering. * Denotes the coefficients to be determined. Let k represent the double-hop scattering matrix. p Let [T] denote the double-hop scattering vector under Paulige conditions. d Let α and α' represent the coherence matrices of double-hop scattering. * This represents the coefficient to be determined.

4. The four-component decomposition method for the scattering characteristics of ship targets according to claim 3, characterized in that, The asymmetric scattering component in step S32 is described as follows: In the formula, [D Asym ] represents the scattering matrix of the asymmetric scattering component, and γ and ρ represent the ratios of the backscattering coefficients of HH and HV to the backscattering coefficients of VV, respectively. The coherence matrix of the non-reflection symmetric scattering model is expressed as: In the formula, T Asym The coherence matrix represents the asymmetric scattering component.

5. The four-component decomposition method for the scattering characteristics of ship targets according to claim 4, characterized in that, The four-component decomposition model in step S33 is: In the formula, [T] represents the total coherence matrix, f s f d f Od f Asym T represents the expansion coefficient. ij Let i,j = 1,2,3 represent the elements corresponding to the coherence matrix [T].

6. The four-component decomposition method for the scattering characteristics of ship targets according to claim 5, characterized in that, Step S4 includes: The power of the ±45° oriented dipole is Solve for f Asym Then, using the existing four-component solution approach, we can solve for the remaining components. The power values ​​for surface scattering, double-hop scattering, ±45° oriented dipole scattering, and non-reflective symmetric scattering are expressed as:

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