CN112213704A - Target scattering cross section calculation method and device - Google Patents

Target scattering cross section calculation method and device Download PDF

Info

Publication number
CN112213704A
CN112213704A CN202010974486.4A CN202010974486A CN112213704A CN 112213704 A CN112213704 A CN 112213704A CN 202010974486 A CN202010974486 A CN 202010974486A CN 112213704 A CN112213704 A CN 112213704A
Authority
CN
China
Prior art keywords
determining
scattering
dimensional geometric
electromagnetic
light beam
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
CN202010974486.4A
Other languages
Chinese (zh)
Other versions
CN112213704B (en
Inventor
陈刚
贺亚鹏
党红杏
苏翔
郑适
刘丽霞
李�浩
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Xian Institute of Space Radio Technology
Original Assignee
Xian Institute of Space Radio Technology
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Xian Institute of Space Radio Technology filed Critical Xian Institute of Space Radio Technology
Priority to CN202010974486.4A priority Critical patent/CN112213704B/en
Publication of CN112213704A publication Critical patent/CN112213704A/en
Application granted granted Critical
Publication of CN112213704B publication Critical patent/CN112213704B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
    • G01S7/418—Theoretical aspects
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
    • G01S7/414—Discriminating targets with respect to background clutter
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
    • G01S7/415—Identification of targets based on measurements of movement associated with the target

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

The invention provides a method and a device for calculating a scattering cross section of a target, wherein the method comprises the following steps: determining a three-dimensional geometric environment electromagnetic model of the planet surface; determining multiple scattering contribution values among the surface elements; determining a scattering contribution value of edge diffraction of the three-dimensional geometric electromagnetic model; determining an electromagnetic scattering contribution value of surface current of the three-dimensional geometric electromagnetic model; synthesizing the multiple scattering contribution values among the surface elements, the scattering contribution value of edge diffraction and the electromagnetic scattering contribution value into a contribution value of a coherent scattering component; determining a value of incoherent electromagnetic scatter contribution; and superposing the contribution value of the coherent scattering component and the incoherent electromagnetic scattering contribution value to obtain a target scattering cross section of the three-dimensional geometric environment electromagnetic model. The method solves the problems that multiple scattering and edge diffraction are ignored, the application range is limited and the calculation precision is not high enough when the target scattering cross section is calculated by the conventional method.

Description

Target scattering cross section calculation method and device
Technical Field
The invention relates to the technical field of space microwave remote sensing, in particular to a method and a device for calculating a scattering cross section of a target.
Background
In the detection of planets such as moon, Mars, asteroid and the like, the distance and speed measuring sensor is an important load of the lander, whether the lander can reach an appointed detection area with high precision and high reliability is determined, and the current working frequency band reaches the Ka band. The distance measuring and speed measuring sensor is mainly used for receiving the echo scattered by the planet, interpreting and processing the echo to obtain important parameter information such as the distance and the speed of the lander relative to the planet, wherein the scattering cross section of a target is an important parameter of the planet echo.
The traditional method for calculating the scattering cross section of the planet surface target utilizes Kirchhoff (Kirchhoff) approximation, and is a traditional calculation method based on a rough surface scattering model. The main idea is to replace the planet surface with a rough local plane, then calculate the reflection coefficient according to the Fresnel reflection law, and obtain the scattered field of the far zone. It is generally suitable for rough surface structure with incident angle less than 30 deg, large curvature and smooth fluctuation. Although the application range is limited, the expression is relatively simple, so that the method is widely applied. Although the method is high in calculation speed, the calculation accuracy is not high enough, the contribution of scattering mechanisms such as multiple scattering and edge diffraction among surface elements is ignored, the application range is limited, the detection environment is more and more complex along with the requirements of the deep space detection on higher accuracy, larger carrier frequency and bandwidth, and higher requirements for the design of a distance and speed measuring sensor are provided, and a high-efficiency and wider-application-range rapid calculation method for calculating the scattering cross section of the target is urgently needed.
Disclosure of Invention
The technical problem solved by the invention is as follows: the defects of the prior art are overcome, and a method and a device for calculating the scattering cross section of the target are provided.
In order to solve the technical problem, the invention provides a method for calculating a scattering cross section of a target, which comprises the following steps:
determining a three-dimensional geometric environment electromagnetic model of the planet surface;
determining multiple scattering contribution values among the surface elements of the three-dimensional geometric electromagnetic model by adopting a light beam tracking method;
determining a scattering contribution value of edge diffraction of the three-dimensional geometric electromagnetic model by adopting a truncation wedge increment length diffraction coefficient method based on a multiple scattering contribution value among surface elements of the three-dimensional geometric electromagnetic model;
determining an electromagnetic scattering contribution value of the surface current of the three-dimensional geometric electromagnetic model by adopting a physical optical method based on multiple scattering contribution values among surface elements of the three-dimensional geometric electromagnetic model;
synthesizing the multiple scattering contribution values among the surface elements, the scattering contribution value of edge diffraction and the electromagnetic scattering contribution value into a contribution value of a coherent scattering component;
determining an incoherent electromagnetic scattering contribution value of the three-dimensional geometric electromagnetic model by adopting a perturbation method;
and superposing the contribution value of the coherent scattering component and the incoherent electromagnetic scattering contribution value to obtain a target scattering cross section of the three-dimensional geometric environment electromagnetic model.
Optionally, the determining a three-dimensional geometric environment electromagnetic model of the planetary surface comprises:
acquiring a three-dimensional lattice of the surface of a to-be-detected area of a planet;
forming a discrete network geometry structure according to the three-dimensional lattice;
determining a material model of the surface of the region to be detected;
and determining a three-dimensional geometric environment electromagnetic model of the planet surface according to the material model and the geometric structure of the discrete network body.
Optionally, the determining the multiple scattering contribution value between the bins of the three-dimensional geometric electromagnetic model by using a beam tracking method includes:
determining a position of the light source;
presetting the scenery space of the three-dimensional geometric environment electromagnetic model according to the position of the light source;
determining an initial beam of light, wherein the initial beam of light is a planar-wave-cylindrical-shaped initial beam of light generated from the element;
performing surface element intersection judgment according to the initial light beam;
determining intersecting beams in the intersection of the bins;
determining a reflected beam and a refracted beam of the intersecting beams;
iteratively performing the steps of determining the position of the light source to the reflected beam and the refracted beam of the intersecting beam according to the reflected beam and the refracted beam until a tracking cutoff condition is satisfied;
establishing a light beam tree-shaped storage structure according to each reflected light beam and each refracted light beam;
acquiring light beams before a preset time point from a stack, and iteratively executing the step of determining the position of the light source until a light beam tree-shaped storage structure is established according to each reflected light beam and each refracted light beam until the stack is empty;
tracking a path recorded by the light beam tree-shaped storage structure, and determining intersection information of the three-dimensional geometric electromagnetic model surface patch;
determining an illumination area irradiated by the light beam according to the intersection information;
calculating a fringe field of the illumination area based on a physical optical algorithm;
and traversing the light beam tree-shaped storage structure, and determining multiple scattering contribution values among the surface elements of the three-dimensional geometric electromagnetic model.
Optionally, determining a scattering contribution value of edge diffraction of the three-dimensional geometric electromagnetic model by using a truncated pitch increment length diffraction coefficient method based on multiple scattering contribution values among bins of the three-dimensional geometric electromagnetic model includes:
determining incident light rays based on multiple scattering contribution values among surface elements of the three-dimensional geometric electromagnetic model;
determining the irradiated cleft according to the incident light;
determining a first ray grazing incidence track and a second ray grazing incidence track of two surfaces corresponding to each wedge;
determining a first length of the first ray grazing incidence trajectory and a second length of the second ray grazing incidence trajectory, respectively;
determining a scattering contribution of edge diffraction of the three-dimensional geometric electromagnetic model from the first length and the second length by:
Figure BDA0002685292650000031
wherein E isfwThe edge wave field is represented and,
Figure BDA0002685292650000032
IT and MT are respectively equivalent edge current and equivalent edge magnetic current, and IT and MT are respectively corresponding functions of a first length and a second length,
Figure BDA0002685292650000033
is the unit vector of the direction of the incident wave,
Figure BDA0002685292650000034
exp (-jkR)/4 π R is the spherical wave propagation factor, which is the unit vector of the scattered wave direction.
Optionally, the determining, by using a physical optics method, an electromagnetic scattering contribution value of a surface current of the three-dimensional geometric electromagnetic model based on the multiple scattering contribution value between the bins of the three-dimensional geometric electromagnetic model includes:
dividing the three-dimensional geometric electromagnetic model into a plurality of surface patches by adopting a triangular surface element;
obtaining parameter information of the following formula from the light beam tree-shaped storage structure, and determining a scattering contribution value of a patch:
Figure BDA0002685292650000041
wherein the content of the first and second substances,
Figure BDA0002685292650000042
the expression is as follows:
Figure BDA0002685292650000043
η0is the wave impedance in the vacuum and,
Figure BDA0002685292650000044
unit vector of polarization direction of incident magnetic field, H0Is the amplitude of incident magnetic field, R' is the vector of the geometric center position of the triangular surface element, and alpha is
Figure BDA0002685292650000045
Projection on surface element Si,. nuiIs the vertex coordinate of Si, and v4＝ν1；
Calculating the electromagnetic scattering contribution value of the surface current of the three-dimensional geometric electromagnetic model according to the scattering contribution value of one surface element by the following formula:
Figure BDA0002685292650000046
optionally, the determining the incoherent electromagnetic scattering contribution value of the three-dimensional geometric electromagnetic model by using a perturbation method includes:
obtaining parameter information of the following formula from the light beam tree-shaped storage structure, and determining an incoherent electromagnetic scattering contribution value of the three-dimensional geometric electromagnetic model through the following formula:
σpq＝8|k2δcosθicosθsαpq|2W(kx+kisinθi，ky)；
wherein k is the wave number, kx，kyThe wave number of the incident wave is respectively the component in the x and y directions, delta is the surface height fluctuation root mean square, W (k)x ky) In order to be a function of the normalized roughness spectrum,
Figure BDA0002685292650000047
Figure BDA0002685292650000048
where ρ (u, v) is a surface correlation coefficient, αpqNamely the polarization amplitude coefficient; p and q are the polarization of the scattered and incident waves, respectively.
Optionally, the obtaining a target scattering cross section of the three-dimensional geometric environment electromagnetic model by superimposing the coherent scattering component contribution value and the incoherent electromagnetic scattering contribution value includes:
calculating the average coherent radar scattering cross section of the medium target by the following formula:
Figure BDA0002685292650000051
wherein the content of the first and second substances,
Figure BDA0002685292650000052
mean coherent radar cross section of medium object, theta0lFor local incident pitch angle, Rp(θ0l) As reflection coefficient, χ (-2 k)0cosθ0l) As a characteristic function, k0Is the free space wavenumber; p and q are the polarization of the scattered and incident waves, respectively;
calculating a total incoherent scattering cross-section of the three-dimensional geometric electromagnetic model by the following formula:
Figure BDA0002685292650000053
wherein the content of the first and second substances,
Figure BDA0002685292650000054
for the shading function, the expression that the integration is carried out only in the area where the incident wave energy irradiates the curved surface and the observation direction can be seen is as follows:
Figure BDA0002685292650000055
wherein the content of the first and second substances,
Figure BDA0002685292650000056
is the rough surface scattering coefficient, which is a function related to local incident angle, surface dielectric constant, rough surface statistical parameters, and polarization of incident wave and scattering wave;
calculating the target scattering cross section of the three-dimensional geometric environment electromagnetic model according to the average coherent radar scattering cross section and the total incoherent scattering cross section of the medium target by the following formula:
Figure BDA0002685292650000057
in order to solve the above technical problem, the present invention further provides an apparatus for calculating a scattering cross section of a target, including:
the three-dimensional geometric environment electromagnetic model determining module is used for determining a three-dimensional geometric environment electromagnetic model of the planet surface;
the multi-scattering contribution value determining module is used for determining the multi-scattering contribution value among the surface elements of the three-dimensional geometric electromagnetic model by adopting a light beam tracking method;
the edge diffraction scattering contribution value determining module is used for determining the edge diffraction scattering contribution value of the three-dimensional geometric electromagnetic model by adopting a truncated wedge increment length diffraction coefficient method based on the multiple scattering contribution value among the surface elements of the three-dimensional geometric electromagnetic model;
the electromagnetic scattering contribution value determining module is used for determining an electromagnetic scattering contribution value from the surface current of the three-dimensional geometric electromagnetic model by adopting a physical optical method based on multiple scattering contribution values among the surface elements of the three-dimensional geometric electromagnetic model;
a coherent scattering component contribution value determining module, configured to synthesize the multiple scattering contribution values between the bins, the edge-diffracted scattering contribution value, and the electromagnetic scattering contribution value into a coherent scattering component contribution value;
the incoherent electromagnetic scattering contribution value determining module is used for determining the incoherent electromagnetic scattering contribution value of the three-dimensional geometric electromagnetic model by adopting a perturbation method;
and the target scattering cross section determining module is used for superposing the contribution value of the coherent scattering component and the incoherent electromagnetic scattering contribution value to obtain a target scattering cross section of the three-dimensional geometric environment electromagnetic model.
Optionally, the three-dimensional geometric environment electromagnetic model determination module comprises:
the three-dimensional lattice acquisition submodule is used for acquiring a three-dimensional lattice of the surface of a region to be detected of the planet;
the discrete network body geometrical structure forming submodule is used for forming a discrete network body geometrical structure according to the three-dimensional lattice;
the material model determining submodule is used for determining a material model of the surface of the region to be detected;
and the three-dimensional geometric environment electromagnetic model determining submodule is used for determining the three-dimensional geometric environment electromagnetic model of the planet surface according to the material model and the geometric structure of the discrete network body.
Optionally, the inter-bin multiple scattering contribution determining module includes:
the position determining submodule of the fixed light source is used for determining the position of the light source;
the preset processing submodule is used for presetting the scenery space of the three-dimensional geometric environment electromagnetic model according to the position of the light source;
an initial beam determination submodule for determining an initial beam, wherein the initial beam is a planar-wave-cylinder-shaped initial beam generated from the element;
the surface element intersection judging submodule is used for judging the intersection of the surface elements according to the initial light beam;
an intersecting beam determining submodule for determining intersecting beams in the binning intersection;
a reflected beam and refracted beam determination submodule for determining a reflected beam and a refracted beam of the intersecting beams;
a first iteration execution sub-module for iteratively executing the steps of determining the position of the light source to the reflected light beam and the refracted light beam of the intersecting light beam according to the reflected light beam and the refracted light beam until a tracking cutoff condition is satisfied;
the light beam tree-shaped storage structure establishing submodule is used for establishing a light beam tree-shaped storage structure according to each reflected light beam and each refracted light beam;
a second iteration execution submodule, configured to acquire a light beam before a preset time point from a stack, and iteratively execute the step of determining the position of the light source until a light beam tree-like storage structure is established according to each reflected light beam and each refracted light beam until the stack is empty;
the intersection information determining submodule is used for tracking a path recorded by the light beam tree-shaped storage structure and determining the intersection information of the three-dimensional geometric electromagnetic model surface patch;
the illumination area determining submodule is used for determining an illumination area irradiated by the light beam according to the intersection information;
a scattered field calculation sub-module of the illumination area for calculating a scattered field of the illumination area based on a physical optical algorithm;
and the multiple scattering contribution value determining submodule between the surface elements is used for traversing the light beam tree-shaped storage structure and determining the multiple scattering contribution value between the surface elements of the three-dimensional geometric electromagnetic model.
Optionally, the module for determining a scattering contribution value of edge diffraction comprises:
the incident ray determination submodule is used for determining incident rays based on multiple scattering contribution values among surface elements of the three-dimensional geometric electromagnetic model;
the first determining submodule is used for determining the irradiated wedges according to incident light;
the second determining submodule is used for determining a first ray grazing incidence track and a second ray grazing incidence track of two surfaces corresponding to each wedge;
a third determining submodule, configured to determine a first length of the first grazing incidence trajectory and a second length of the second grazing incidence trajectory, respectively;
a fourth determining submodule, configured to determine a scattering contribution value of edge diffraction of the three-dimensional geometric electromagnetic model according to the first length and the second length by using the following formula:
Figure BDA0002685292650000081
wherein E isfwThe edge wave field is represented and,
Figure BDA0002685292650000082
IT and MT are respectively equivalent edge current and equivalent edge magnetic current, and IT and MT are respectively corresponding functions of a first length and a second length,
Figure BDA0002685292650000083
is the unit vector of the direction of the incident wave,
Figure BDA0002685292650000084
exp (-jkR)/4 π R is the spherical wave propagation factor, which is the unit vector of the scattered wave direction.
Optionally, the electromagnetic scattering contribution determining module includes:
the subdivision submodule is used for dividing the three-dimensional geometric electromagnetic model into a plurality of surface patches by adopting a triangular surface element;
a patch scattering contribution value determining submodule, configured to obtain parameter information of the following formula from the beam tree storage structure, and determine a patch scattering contribution value:
Figure BDA0002685292650000085
wherein the content of the first and second substances,
Figure BDA0002685292650000086
the expression is as follows:
Figure BDA0002685292650000087
Figure BDA0002685292650000088
η0is the wave impedance in the vacuum and,
Figure BDA0002685292650000089
unit vector of polarization direction of incident magnetic field, H0Is the amplitude of incident magnetic field, R' is the vector of the geometric center position of the triangular surface element, and alpha is
Figure BDA00026852926500000810
Projection on surface element Si,. nuiIs the vertex coordinate of Si, and v4＝ν1；
The electromagnetic scattering contribution value determination submodule of the surface current arrival of the three-dimensional geometric electromagnetic model is used for calculating the electromagnetic scattering contribution value of the surface current arrival of the three-dimensional geometric electromagnetic model according to the scattering contribution value of one surface element through the following formula:
Figure BDA00026852926500000811
optionally, the incoherent electromagnetic scattering contribution value determining module is specifically configured to:
obtaining parameter information of the following formula from the light beam tree-shaped storage structure, and determining an incoherent electromagnetic scattering contribution value of the three-dimensional geometric electromagnetic model through the following formula:
σpq＝8|k2δcosθicosθsαpq|2W(kx+kisinθi,ky)；
wherein k is the wave number, kx，kyThe wave number of the incident wave is respectively the component in the x and y directions, delta is the surface height fluctuation root mean square, W (k)x ky) In order to be a function of the normalized roughness spectrum,
Figure BDA0002685292650000091
Figure BDA0002685292650000092
where ρ (u, v) is a surface correlation coefficient, αpqNamely the polarization amplitude coefficient; p and q are the polarization of the scattered and incident waves, respectively.
Optionally, the target scattering cross-section determining module is specifically configured to:
calculating the average coherent radar scattering cross section of the medium target by the following formula:
Figure BDA0002685292650000093
wherein the content of the first and second substances,
Figure BDA0002685292650000094
mean coherent radar cross section of medium object, theta0lFor local incident pitch angle, Rp(θ0l) As reflection coefficient, χ (-2 k)0cosθ0l) As a characteristic function, k0Is the free space wavenumber; p and q are the polarization of the scattered and incident waves, respectively;
calculating a total incoherent scattering cross-section of the three-dimensional geometric electromagnetic model by the following formula:
Figure BDA0002685292650000095
wherein the content of the first and second substances,
Figure BDA0002685292650000096
for the shading function, the expression that the integration is carried out only in the area where the incident wave energy irradiates the curved surface and the observation direction can be seen is as follows:
Figure BDA0002685292650000097
wherein the content of the first and second substances,
Figure BDA0002685292650000098
is the rough surface scattering coefficient, which is a function related to local incident angle, surface dielectric constant, rough surface statistical parameters, and polarization of incident wave and scattering wave;
calculating the target scattering cross section of the three-dimensional geometric environment electromagnetic model according to the average coherent radar scattering cross section and the total incoherent scattering cross section of the medium target by the following formula:
Figure BDA0002685292650000099
compared with the prior art, the invention has the advantages that: aiming at the defects that multiple scattering and edge diffraction are ignored when a target scattering cross section is calculated by a satellite-borne distance and speed measuring sensor of the prior art, the invention solves the problems of multiple scattering based on a light beam tracking method, processes diffraction by a truncation increment length diffraction coefficient method, processes surface current scattering by a physical optical method, and processes micro fluctuation scattering similar to a planet surface by combining a perturbation method, thereby effectively overcoming the defects that the planet surface is replaced by a rough local plane by the traditional processing method, and then the reflection coefficient is calculated according to a Fresnel reflection law to obtain a scattering field in a far area, so that the incident angle is less than 30 degrees, the application range is limited and the calculation precision is not high enough.
Drawings
FIG. 1 is a flowchart illustrating steps of a method for calculating a scattering cross-section of an object according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a physical-optical approximation of a target surface provided by an embodiment of the present invention;
FIG. 3 is a schematic view of the scattering of a micro-rough surface according to an embodiment of the present invention;
FIG. 4 is a sample rough cube model generated at a time provided by an embodiment of the present invention;
FIG. 5 is a result diagram of calculating scattering cross-sections of targets at different angles by using the method for calculating scattering cross-sections of targets provided by the embodiment of the present invention, with respect to the model of FIG. 4;
fig. 6 is a schematic structural diagram of an apparatus for calculating a scattering cross section of a target according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, a flowchart illustrating steps of a method for calculating a scattering cross section of a target according to an embodiment of the present invention is shown, and as shown in fig. 1, the method may specifically include the following steps:
step 110: a three-dimensional geometric environmental electromagnetic model of the planetary surface is determined.
The method comprises the steps of obtaining three-dimensional lattice distribution of the surface of a lander detection area by using an optical camera or other means, representing one edge into two half-edge data structures with opposite directions in a topological sense by taking the edge as a core, connecting vertexes, edges and rings in series in a triangular grid mode to form a discrete grid body geometric structure capable of meeting the requirement of electromagnetic calculation, and constructing a high-precision planetary surface three-dimensional geometric environment electromagnetic model by combining material models (such as relative dielectric constant and relative magnetic permeability) to serve as input of next electromagnetic calculation. In a specific implementation manner of the present invention, the step 110 may include:
substep A1: acquiring a three-dimensional lattice of the surface of a to-be-detected area of a planet;
substep A2: forming a discrete network geometry structure according to the three-dimensional lattice;
substep A3: determining a material model of the surface of the region to be detected;
substep A4: and determining a three-dimensional geometric environment electromagnetic model of the planet surface according to the material model and the geometric structure of the discrete network body.
Step 120: and determining the multiple scattering contribution value among the surface elements of the three-dimensional geometric electromagnetic model by adopting a beam tracking method.
Ray tracing algorithms employ images composed of pixels. For each pixel in the image, it projects a chief ray into the scene. The direction of the chief ray is obtained by tracking from the eye to the pixel centerline. Once the direction of the principal ray is determined, each object in the scene begins to be examined to see if it intersects any of them. When a situation occurs in which the principal ray intersects a plurality of objects, an object whose intersection point is closest to the eye is selected. Shadow rays are cast from the intersection points toward the light source. If the particular ray does not intersect an object on its way to the light source, then the point is illuminated. If it intersects another object, the object casts a shadow thereon. If this is repeated for each pixel, a two-dimensional representation of the three-dimensional scene can be obtained.
In a specific implementation manner of the present invention, the step 120 may include:
substep B1: the position of the light source is determined.
And preprocessing the scene space according to the position of the light source, and performing surface element priority arrangement to eliminate the shielding among the objects.
Substep B2: and presetting the scenery space of the three-dimensional geometric environment electromagnetic model according to the position of the light source.
Substep B3: an initial beam is determined.
Wherein the initiation light is an initiation beam of light in the shape of a planar wave cylinder generated from the element.
Substep B4: and performing surface element intersection judgment according to the initial light beam.
Substep B5: the intersecting beams in the intersection of the bins are determined.
Substep B6: reflected and refracted beams of the intersecting beams are determined.
And performing surface element intersection judgment on the initial light beam of the plane wave cylinder shape generated by the element, finding out the intersected light beam, and then generating a reflected light beam and a refracted light beam according to the linear transformation of reflection and refraction.
Substep B7: iteratively performing the steps of determining the position of the light source to the reflected beam and the refracted beam of the intersecting beam according to the reflected beam and the refracted beam until a tracking cutoff condition is satisfied.
The scene is again pre-processed from the reflected and refracted beams and the process is then repeated until the tracking cut-off condition is met.
Substep B8: and establishing a light beam tree-shaped storage structure according to each reflected light beam and each refracted light beam.
And establishing a light beam tree-shaped storage structure, and storing the intersection information and the path of the light beam to finish the tracking of the light beam.
Substep B9: and acquiring the light beams before a preset time point from the stack, and iteratively executing the step of determining the position of the light source until the light beam tree-shaped storage structure is established according to each reflected light beam and each refracted light beam until the stack is empty.
The previously left beam is removed from the stack and the process of B1-B8 is repeated until the stack is empty.
Substep B10: and tracking the path recorded by the light beam tree-shaped storage structure, and determining the intersection information of the three-dimensional geometric electromagnetic model surface patch.
Substep B11: and determining an illumination area irradiated by the light beam according to the intersection information.
Substep B12: calculating a fringe field of the illumination region based on a physical-optical algorithm.
And tracking the field value of the path recorded by the light beam tree-shaped storage structure, acquiring illumination areas irradiated by the light beams according to the intersection information recorded on each panel, and calculating the scattered field on the areas by using a physical optical algorithm.
Substep B13: and traversing the light beam tree-shaped storage structure, and determining multiple scattering contribution values among the surface elements of the three-dimensional geometric electromagnetic model.
Step 130: and determining the scattering contribution value of the edge diffraction of the three-dimensional geometric electromagnetic model by adopting a truncation wedge increment length diffraction coefficient method based on the multiple scattering contribution value among the surface elements of the three-dimensional geometric electromagnetic model.
To calculate the scattered fields from edges, cusps, corners and in shadow areas, calculations were performed using truncated wedge delta length diffraction coefficient (TWILDC) taking into account the applicability of the algorithm.
In a specific implementation manner of the present invention, the step 130 may include:
substep C1: and determining incident light rays based on multiple scattering contribution values among the surface elements of the three-dimensional geometric electromagnetic model.
Substep C2: the irradiated cleft is determined according to the incident light.
Substep C3: and determining a first ray grazing incidence track and a second ray grazing incidence track of two surfaces corresponding to each wedge.
Ray grazing incidence trajectories for both faces (face 0 and face n) of the split are found for each split.
Substep C4: a first length of the first grazing incidence trajectory and a second length of the second grazing incidence trajectory are determined, respectively.
Substep C5: and determining the scattering contribution value of the edge diffraction of the three-dimensional geometric electromagnetic model according to the first length and the second length by the following formula.
Figure BDA0002685292650000131
Wherein E isfwThe edge wave field is represented and,
Figure BDA0002685292650000132
IT and MT are respectively equivalent edge current and equivalent edge magnetic current, and IT and MT are respectively corresponding functions of a first length and a second length,
Figure BDA0002685292650000133
is the unit vector of the direction of the incident wave,
Figure BDA0002685292650000134
exp (-jkR)/4 π R is the spherical wave propagation factor, which is the unit vector of the scattered wave direction.
Step 140: and determining the electromagnetic scattering contribution value of the surface current of the three-dimensional geometric electromagnetic model by adopting a physical optical method based on the multiple scattering contribution value among the surface elements of the three-dimensional geometric electromagnetic model.
The physical optics method, one of the high frequency approximation methods in electromagnetic calculations, represents the scattering field by the integral of the induced current on the surface of the scatterer. And calculating the scattered field of the surface of the three-dimensional geometric environment electromagnetic model based on a physical optical method.
In a specific implementation manner of the present invention, the step 140 may include:
substep D1: and dividing the three-dimensional geometric electromagnetic model into a plurality of surface patches by adopting a triangular surface element.
Substep D2: obtaining parameter information of the following formula from the light beam tree-shaped storage structure, and determining a scattering contribution value of a patch:
Figure BDA0002685292650000135
wherein the content of the first and second substances,
Figure BDA0002685292650000141
the expression is as follows:
Figure BDA0002685292650000142
η0is the wave impedance in the vacuum and,
Figure BDA0002685292650000143
unit vector of polarization direction of incident magnetic field, H0Is the amplitude of incident magnetic field, R' is the vector of the geometric center position of the triangular surface element, and alpha is
Figure BDA0002685292650000144
Projection on surface element Si,. nuiIs the vertex coordinate of Si, and v4＝ν1。
Substep D3: calculating the electromagnetic scattering contribution value of the surface current of the three-dimensional geometric electromagnetic model according to the scattering contribution value of one surface element by the following formula:
Figure BDA0002685292650000145
except that the electromagnetic scattering contribution of the surface of the three-dimensional geometric electromagnetic model can be calculated by calculating the scattered field of one patch and summing the scattered fields of a plurality of patches.
The electromagnetic scattering contribution value of the surface of the three-dimensional geometric electromagnetic model can also be calculated by determining parameters of a formula from the beam tree storage structure based on the following formula:
Figure BDA0002685292650000146
Figure BDA0002685292650000147
and (6) performing calculation.
In particular, Physical Optics (PO) is commonly used to address the problem of electromagnetic scattering of electrically large sized targets. The basic principle is to replace the scatterer itself with the induced current on the surface of the scatterer and to find the scattering field of the object by approximating and integrating the surface induced field. Consider a finite scatterer in free space, with a closed surface S, and a point of view P outside the surface S, where a plane wave of unity amplitude is incident, as shown in figure 2. Where R 'represents a source point position vector, which is a position vector of the surface point Q, R represents an observation point position vector, which is a position vector of the field point P, R (R ═ R-R') represents a position vector of the surface point Q to the field point P,
Figure BDA0002685292650000148
is the unit vector of the direction of the incident wave,
Figure BDA0002685292650000149
is the unit vector of the direction of the scattered wave,
Figure BDA00026852926500001410
is the outer normal unit vector at surface point Q. The expression of the scattering electric field at the point P is as follows;
Figure BDA00026852926500001411
step 150: the multiple scattering contribution between the bins, the scattering contribution from edge diffraction and the electromagnetic scattering contribution are combined to the contribution of the coherent scattering component.
Step 160: and determining the incoherent electromagnetic scattering contribution value of the three-dimensional geometric electromagnetic model by adopting a perturbation method.
Consider a horizontally polarized plane wave incident on a microrough interface as shown in fig. 3. Wherein Ei, Hi and Es respectively enter the electromagnetic field and the scattered electric field, and theta i, theta s, theta i ', theta s' and
Figure BDA0002685292650000154
an incident pitch angle and a scattering pitch angle in the medium 1, a transmission pitch angle and a scattering pitch angle in the medium 2, and a scattering azimuth angle in the medium 1, respectively.
In a specific implementation manner of the present invention, the step 160 may include:
sub-step E1: obtaining parameter information of the following formula from the light beam tree-shaped storage structure, and determining an incoherent electromagnetic scattering contribution value of the three-dimensional geometric electromagnetic model through the following formula:
obtaining parameter information of the following formula from the light beam tree-shaped storage structure, and determining an incoherent electromagnetic scattering contribution value of the three-dimensional geometric electromagnetic model through the following formula:
σpq＝8|k2δcosθicosθsαpq|2W(kx+kisinθi，ky)；
wherein k isWave number, kx，kyThe wave number of the incident wave is respectively the component in the x and y directions, delta is the surface height fluctuation root mean square, W (k)x ky) In order to be a function of the normalized roughness spectrum,
Figure BDA0002685292650000151
Figure BDA0002685292650000152
where ρ (u, v) is a surface correlation coefficient, αpqNamely the polarization amplitude coefficient; p and q are the polarization of the scattered and incident waves, respectively.
For a known spectral distribution (e.g., a Gaussian spectral distribution), W (k) is determinedx,ky) After that, substituting σpqThe scattering coefficient distribution can be found by the expression (2).
Step 170: and superposing the contribution value of the coherent scattering component and the incoherent electromagnetic scattering contribution value to obtain a target scattering cross section of the three-dimensional geometric environment electromagnetic model.
The scattering cross section area obtained by the method of combining beam tracking with physical optics and truncated wedge increment length diffraction coefficient is defined as
Figure BDA0002685292650000153
In a specific implementation manner of the present invention, the step 170 may include:
sub-step F1: calculating the average coherent radar scattering cross section of the medium target by the following formula:
Figure BDA0002685292650000161
wherein the content of the first and second substances,
Figure BDA0002685292650000162
mean coherent radar cross section of medium object, theta0lFor local incident pitch angle, Rp(θ0l) As reflection coefficient, χ (-2 k)0cosθ0l) As a characteristic function, k0Is the free space wavenumber; p and q are the polarization of the scattered and incident waves, respectively.
Sub-step F2: calculating a total incoherent scattering cross-section of the three-dimensional geometric electromagnetic model by the following formula:
Figure BDA0002685292650000163
wherein the content of the first and second substances,
Figure BDA0002685292650000164
for the shading function, the expression that the integration is carried out only in the area where the incident wave energy irradiates the curved surface and the observation direction can be seen is as follows:
Figure BDA0002685292650000165
wherein the content of the first and second substances,
Figure BDA0002685292650000166
is the rough surface scattering coefficient, which is a function of local incident angle, surface dielectric constant, rough surface statistical parameters, and polarization of incident and scattered waves.
Therefore, for a given rough medium target, the radar scattering cross section of the conductor under the undisturbed condition, the dielectric parameter of the medium and the characteristic function of the surface are known, and the coherent radar scattering cross section can be obtained.
At a high frequency approximation, the incoherent scattering of the individual cell faces can be considered approximately uncorrelated with one another. Thus, the total incoherent scattering cross-section of the object is the sum of the incoherent scattering cross-sections of the individual cell faces.
Sub-step F3: calculating the target scattering cross section of the three-dimensional geometric environment electromagnetic model according to the average coherent radar scattering cross section and the total incoherent scattering cross section of the medium target by the following formula:
Figure BDA0002685292650000167
in one example: assuming a cube with a side length of 1 cm, the roughness is: the root mean square height is 30 microns and the correlation length is 150 microns, satisfying a gaussian distribution. The rough model generated at a time is shown in fig. 4.
Assuming that the wavelength of incident plane electromagnetic waves is 1 mm, the azimuth angle is 0 degree and the pitch angle is 0-90 degrees at a single station, and sampling is carried out at intervals of 1 degree, and 91 sampling points are provided. The calculation is performed by using an accurate algorithm (multilayer fast multipole algorithm) and a proposed fast hybrid algorithm, respectively. The calculation results are shown in FIG. 5, where (a) is HH polarization comparison and (b) is VV polarization comparison. The calculation time of the precise algorithm (configuration: Intel (R) Xeon (R) W5590 series CPU main frequency 3.33GHz, 2 processor 8 cores, internal memory 48GHz and 64-bit operation Win7 system) is 8.88 hours. And the calculation time of a fast mixing approximation algorithm (configuration: Intel (R) core (TM) i7-4712MQ series CPU main frequency 2.30GHz, 2 processor 8 cores, 8GHz memory and 64-bit Win7 operating system) is 5 minutes.
The calculation results show that the peak deviation of the VV polarization is 0.50dB, the mean deviation is 0.93dB, and the root mean square error is 2.30 dB. The peak deviation of the HH polarization was 0.49dB, the mean deviation was 1.24dB, and the root mean square error was 1.73 dB. The parameter deviation is better than 3 dB.
Therefore, the fast hybrid approximation algorithm provided by the invention realizes efficient and fast electromagnetic calculation on the premise of keeping the calculation accuracy.
Referring to fig. 6, a schematic structural diagram of an apparatus for calculating a scattering cross section of a target according to an embodiment of the present invention is shown, where the apparatus may specifically include the following modules:
a three-dimensional geometric environment electromagnetic model determining module 201, configured to determine a three-dimensional geometric environment electromagnetic model of a planet surface;
an inter-bin multiple scattering contribution determining module 202, configured to determine an inter-bin multiple scattering contribution of the three-dimensional geometric electromagnetic model by using a beam tracking method;
the edge diffraction scattering contribution value determining module 203 is configured to determine, based on multiple scattering contribution values among bins of the three-dimensional geometric electromagnetic model, a scattering contribution value of edge diffraction of the three-dimensional geometric electromagnetic model by using a truncated pitch increment length diffraction coefficient method;
an electromagnetic scattering contribution value determining module 204, configured to determine an electromagnetic scattering contribution value of a surface current of the three-dimensional geometric electromagnetic model by using a physical optics method based on multiple scattering contribution values among bins of the three-dimensional geometric electromagnetic model;
a coherent scattering component contribution determining module 205, configured to synthesize the multiple scattering contribution among the bins, the edge-diffracted scattering contribution, and the electromagnetic scattering contribution into a coherent scattering component contribution;
an incoherent electromagnetic scattering contribution value determining module 206, configured to determine an incoherent electromagnetic scattering contribution value of the three-dimensional geometric electromagnetic model by using a perturbation method;
and the target scattering cross section determining module 207 is configured to superimpose the contribution value of the coherent scattering component and the incoherent electromagnetic scattering contribution value to obtain a target scattering cross section of the three-dimensional geometric environment electromagnetic model.
Optionally, the three-dimensional geometric environment electromagnetic model determination module comprises:
the three-dimensional lattice acquisition submodule is used for acquiring a three-dimensional lattice of the surface of a region to be detected of the planet;
the discrete network body geometrical structure forming submodule is used for forming a discrete network body geometrical structure according to the three-dimensional lattice;
the material model determining submodule is used for determining a material model of the surface of the region to be detected;
and the three-dimensional geometric environment electromagnetic model determining submodule is used for determining the three-dimensional geometric environment electromagnetic model of the planet surface according to the material model and the geometric structure of the discrete network body.
Optionally, the inter-bin multiple scattering contribution determining module includes:
the position determining submodule of the fixed light source is used for determining the position of the light source;
the preset processing submodule is used for presetting the scenery space of the three-dimensional geometric environment electromagnetic model according to the position of the light source;
an initial beam determination submodule for determining an initial beam, wherein the initial beam is a planar-wave-cylinder-shaped initial beam generated from the element;
the surface element intersection judging submodule is used for judging the intersection of the surface elements according to the initial light beam;
an intersecting beam determining submodule for determining intersecting beams in the binning intersection;
a reflected beam and refracted beam determination submodule for determining a reflected beam and a refracted beam of the intersecting beams;
a first iteration execution sub-module for iteratively executing the steps of determining the position of the light source to the reflected light beam and the refracted light beam of the intersecting light beam according to the reflected light beam and the refracted light beam until a tracking cutoff condition is satisfied;
the light beam tree-shaped storage structure establishing submodule is used for establishing a light beam tree-shaped storage structure according to each reflected light beam and each refracted light beam;
a second iteration execution submodule, configured to acquire a light beam before a preset time point from a stack, and iteratively execute the step of determining the position of the light source until a light beam tree-like storage structure is established according to each reflected light beam and each refracted light beam until the stack is empty;
the intersection information determining submodule is used for tracking a path recorded by the light beam tree-shaped storage structure and determining the intersection information of the three-dimensional geometric electromagnetic model surface patch;
the illumination area determining submodule is used for determining an illumination area irradiated by the light beam according to the intersection information;
a scattered field calculation sub-module of the illumination area for calculating a scattered field of the illumination area based on a physical optical algorithm;
and the multiple scattering contribution value determining submodule between the surface elements is used for traversing the light beam tree-shaped storage structure and determining the multiple scattering contribution value between the surface elements of the three-dimensional geometric electromagnetic model.
Optionally, the module for determining a scattering contribution value of edge diffraction comprises:
the incident ray determination submodule is used for determining incident rays based on multiple scattering contribution values among surface elements of the three-dimensional geometric electromagnetic model;
the first determining submodule is used for determining the irradiated wedges according to incident light;
the second determining submodule is used for determining a first ray grazing incidence track and a second ray grazing incidence track of two surfaces corresponding to each wedge;
a third determining submodule, configured to determine a first length of the first grazing incidence trajectory and a second length of the second grazing incidence trajectory, respectively;
a fourth determining submodule, configured to determine a scattering contribution value of edge diffraction of the three-dimensional geometric electromagnetic model according to the first length and the second length by using the following formula:
Figure BDA0002685292650000191
wherein E isfwThe edge wave field is represented and,
Figure BDA0002685292650000192
IT and MT are respectively equivalent edge current and equivalent edge magnetic current, and IT and MT are respectively corresponding functions of a first length and a second length,
Figure BDA0002685292650000193
is the unit vector of the direction of the incident wave,
Figure BDA0002685292650000194
exp (-jkR)/4 π R is the spherical wave propagation factor, which is the unit vector of the scattered wave direction.
Optionally, the electromagnetic scattering contribution determining module is specifically configured to:
the subdivision submodule is used for dividing the three-dimensional geometric electromagnetic model into a plurality of surface patches by adopting a triangular surface element;
a patch scattering contribution value determining submodule, configured to obtain parameter information of the following formula from the beam tree storage structure, and determine a patch scattering contribution value:
Figure BDA0002685292650000201
wherein the content of the first and second substances,
Figure BDA0002685292650000202
the expression is as follows:
Figure BDA0002685292650000203
Figure BDA0002685292650000204
η0is the wave impedance in the vacuum and,
Figure BDA0002685292650000205
unit vector of polarization direction of incident magnetic field, H0Is the amplitude of incident magnetic field, R' is the vector of the geometric center position of the triangular surface element, and alpha is
Figure BDA0002685292650000206
Projection on surface element Si,. nuiIs the vertex coordinate of Si, and v4＝ν1；
The electromagnetic scattering contribution value determination submodule of the surface current arrival of the three-dimensional geometric electromagnetic model is used for calculating the electromagnetic scattering contribution value of the surface current arrival of the three-dimensional geometric electromagnetic model according to the scattering contribution value of one surface element through the following formula:
Figure BDA0002685292650000207
optionally, the incoherent electromagnetic scattering contribution value determining module is specifically configured to:
obtaining parameter information of the following formula from the light beam tree-shaped storage structure, and determining an incoherent electromagnetic scattering contribution value of the three-dimensional geometric electromagnetic model through the following formula:
σpq＝8|k2δcosθicosθsαpq|2W(kx+kisinθi，ky)；
wherein k is the wave number, kx，kyThe wave number of the incident wave is respectively the component in the x and y directions, delta is the surface height fluctuation root mean square, W (k)x ky) In order to be a function of the normalized roughness spectrum,
Figure BDA0002685292650000208
Figure BDA0002685292650000209
where ρ (u, v) is a surface correlation coefficient, αpqNamely the polarization amplitude coefficient; p and q are the polarization of the scattered and incident waves, respectively.
Optionally, the target scattering cross-section determining module comprises:
a first calculation submodule for calculating an average coherent radar scattering cross-section of the medium target by the following formula:
Figure BDA00026852926500002010
wherein the content of the first and second substances,
Figure BDA00026852926500002011
mean coherent radar cross section of medium object, theta0lFor local incident pitch angle, Rp(θ0l) As reflection coefficient, χ (-2 k)0cosθ0l) As a characteristic function, k0Is the free space wavenumber; p and q are the polarization of the scattered and incident waves, respectively;
a second calculation submodule for calculating a total incoherent scattering cross-section of the three-dimensional geometric electromagnetic model by the following formula:
Figure BDA0002685292650000211
wherein the content of the first and second substances,
Figure BDA0002685292650000212
for the shading function, the expression that the integration is carried out only in the area where the incident wave energy irradiates the curved surface and the observation direction can be seen is as follows:
Figure BDA0002685292650000213
wherein the content of the first and second substances,
Figure BDA0002685292650000214
is the rough surface scattering coefficient, which is a function related to local incident angle, surface dielectric constant, rough surface statistical parameters, and polarization of incident wave and scattering wave;
a third calculating submodule, configured to calculate a target scattering cross section of the three-dimensional geometric environment electromagnetic model according to the average coherent radar scattering cross section and the total incoherent scattering cross section of the medium target by using the following formula:
Figure BDA0002685292650000215
while the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (14)

1. A method for calculating a scattering cross-section of an object, comprising:
determining a three-dimensional geometric environment electromagnetic model of the planet surface;
determining multiple scattering contribution values among the surface elements of the three-dimensional geometric electromagnetic model by adopting a light beam tracking method;
determining a scattering contribution value of edge diffraction of the three-dimensional geometric electromagnetic model by adopting a truncation wedge increment length diffraction coefficient method based on a multiple scattering contribution value among surface elements of the three-dimensional geometric electromagnetic model;
determining an electromagnetic scattering contribution value of surface current of the three-dimensional geometric electromagnetic model by adopting a physical optical method based on multiple scattering contribution values among surface elements of the three-dimensional geometric electromagnetic model;
synthesizing the multiple scattering contribution values among the surface elements, the scattering contribution value of edge diffraction and the electromagnetic scattering contribution value into a contribution value of a coherent scattering component;
determining an incoherent electromagnetic scattering contribution value of the three-dimensional geometric electromagnetic model by adopting a perturbation method;
and superposing the contribution value of the coherent scattering component and the incoherent electromagnetic scattering contribution value to obtain a target scattering cross section of the three-dimensional geometric environment electromagnetic model.
2. The method of claim 1, wherein determining the three-dimensional geometric environmental electromagnetic model of the planetary surface comprises:
acquiring a three-dimensional lattice of the surface of a to-be-detected area of a planet;
forming a discrete network geometry structure according to the three-dimensional lattice;
determining a material model of the surface of the region to be detected;
and determining a three-dimensional geometric environment electromagnetic model of the planet surface according to the material model and the geometric structure of the discrete network body.
3. The method of claim 1, wherein said determining multiple scattering contributions between bins of said three-dimensional geometric electromagnetic model using beam tracking comprises:
determining a position of the light source;
presetting the scenery space of the three-dimensional geometric environment electromagnetic model according to the position of the light source;
determining an initial light beam, wherein the initial light beam is a plane-wave-cylindrical initial light beam generated from a bin;
performing surface element intersection judgment according to the initial light beam;
determining intersecting beams in the intersection of the bins;
determining a reflected beam and a refracted beam of the intersecting beams;
iteratively performing the steps of determining the position of the light source to the reflected beam and the refracted beam of the intersecting beam according to the reflected beam and the refracted beam until a tracking cutoff condition is satisfied;
establishing a light beam tree-shaped storage structure according to each reflected light beam and each refracted light beam;
acquiring light beams before a preset time point from a stack, and iteratively executing the step of determining the position of the light source until a light beam tree-shaped storage structure is established according to each reflected light beam and each refracted light beam until the stack is empty;
tracking a path recorded by the light beam tree-shaped storage structure, and determining intersection information of the three-dimensional geometric electromagnetic model surface patch;
determining an illumination area irradiated by the light beam according to the intersection information;
calculating a fringe field of the illumination area based on a physical optical algorithm;
and traversing the light beam tree-shaped storage structure, and determining multiple scattering contribution values among the surface elements of the three-dimensional geometric electromagnetic model.
4. The method according to claim 1, wherein determining the scattering contribution of edge diffraction of the three-dimensional geometric electromagnetic model by using a truncated pitch increment length diffraction coefficient method based on the multiple scattering contribution between bins of the three-dimensional geometric electromagnetic model comprises:
determining incident light rays based on multiple scattering contribution values among surface elements of the three-dimensional geometric electromagnetic model;
determining the irradiated cleft according to the incident light;
determining a first ray grazing incidence track and a second ray grazing incidence track of two surfaces corresponding to each wedge;
determining a first length of the first ray grazing incidence trajectory and a second length of the second ray grazing incidence trajectory, respectively;
determining a scattering contribution of edge diffraction of the three-dimensional geometric electromagnetic model from the first length and the second length by:
Figure FDA0002685292640000031
wherein E isfwThe edge wave field is represented and,
Figure FDA0002685292640000032
ITand MTRespectively an equivalent edge current and an equivalent edge current, and ITAnd MTRespectively a function of the first length and the second length,
Figure FDA0002685292640000033
is the unit vector of the direction of the incident wave,
Figure FDA0002685292640000034
exp (-jkR)/4 π R is the spherical wave propagation factor, which is the unit vector of the scattered wave direction.
5. The method according to claim 3, wherein the determining the electromagnetic scattering contribution value of the surface current of the three-dimensional geometric electromagnetic model by using a physical optical method based on the multiple scattering contribution value among the bins of the three-dimensional geometric electromagnetic model comprises:
dividing the three-dimensional geometric electromagnetic model into a plurality of surface patches by adopting a triangular surface element;
obtaining parameter information of the following formula from the light beam tree-shaped storage structure, and determining a scattering contribution value of a patch:
Figure FDA0002685292640000035
wherein the content of the first and second substances,
Figure FDA0002685292640000036
the expression is as follows:
Figure FDA0002685292640000037
η0is the wave impedance in the vacuum and,
Figure FDA0002685292640000038
unit vector of polarization direction of incident magnetic field, H0Is the amplitude of incident magnetic field, R' is the vector of the geometric center position of the triangular surface element, and alpha is
Figure FDA0002685292640000039
Projection on the surface element Si, viIs the vertex coordinate of Si, and v4＝ν1；
Calculating the electromagnetic scattering contribution value of the surface current of the three-dimensional geometric electromagnetic model according to the scattering contribution value of one surface element by the following formula:
Figure FDA00026852926400000310
6. the method of claim 3, wherein said determining the incoherent electromagnetic scattering contribution of the three-dimensional geometric electromagnetic model using perturbation comprises:
obtaining parameter information of the following formula from the light beam tree-shaped storage structure, and determining an incoherent electromagnetic scattering contribution value of the three-dimensional geometric electromagnetic model through the following formula:
σpq＝8|k2δcosθicosθsαpq|2W(kx+kisinθi,ky)；
wherein k is the wave number, kx，kyThe wave number of the incident wave is respectively the component in the x and y directions, delta is the surface height fluctuation root mean square, W (k)x ky) In order to be a function of the normalized roughness spectrum,
Figure FDA0002685292640000041
Figure FDA0002685292640000042
where ρ (u, v) is a surface correlation coefficient, αpqNamely the polarization amplitude coefficient; p and q are the polarization of the scattered and incident waves, respectively.
7. The method according to claim 1, wherein the adding the contribution value of the coherent scattering component and the incoherent electromagnetic scattering contribution value to obtain an object scattering cross section of the three-dimensional geometric environment electromagnetic model comprises:
calculating the average coherent radar scattering cross section of the medium target by the following formula:
Figure FDA0002685292640000043
wherein the content of the first and second substances,
Figure FDA0002685292640000044
mean coherent radar cross section of medium object, theta0lFor local incident pitch angle, Rp(θ0l) As reflection coefficient, χ (-2 k)0cosθ0l) As a characteristic function, k0Is the free space wavenumber; p and q are scattering and incoming, respectivelyPolarization of the radio wave;
calculating a total incoherent scattering cross-section of the three-dimensional geometric electromagnetic model by the following formula:
Figure FDA0002685292640000045
wherein the content of the first and second substances,
Figure FDA0002685292640000046
for the shading function, the expression that the integration is carried out only in the area where the incident wave energy irradiates the curved surface and the observation direction can be seen is as follows:
Figure FDA0002685292640000047
wherein the content of the first and second substances,
Figure FDA0002685292640000048
is the rough surface scattering coefficient, which is a function related to local incident angle, surface dielectric constant, rough surface statistical parameters, and polarization of incident wave and scattering wave;
calculating the target scattering cross section of the three-dimensional geometric environment electromagnetic model according to the average coherent radar scattering cross section and the total incoherent scattering cross section of the medium target by the following formula:
Figure FDA0002685292640000049
8. an object scattering cross-section calculation apparatus, comprising:
the three-dimensional geometric environment electromagnetic model determining module is used for determining a three-dimensional geometric environment electromagnetic model of the planet surface;
the multi-scattering contribution value determining module is used for determining the multi-scattering contribution value among the surface elements of the three-dimensional geometric electromagnetic model by adopting a light beam tracking method;
the edge diffraction scattering contribution value determining module is used for determining the edge diffraction scattering contribution value of the three-dimensional geometric electromagnetic model by adopting a truncated wedge increment length diffraction coefficient method based on the multiple scattering contribution value among the surface elements of the three-dimensional geometric electromagnetic model;
the electromagnetic scattering contribution value determining module is used for determining an electromagnetic scattering contribution value from the surface current of the three-dimensional geometric electromagnetic model by adopting a physical optical method based on multiple scattering contribution values among the surface elements of the three-dimensional geometric electromagnetic model;
a coherent scattering component contribution value determining module, configured to synthesize the multiple scattering contribution values between the bins, the edge-diffracted scattering contribution value, and the electromagnetic scattering contribution value into a coherent scattering component contribution value;
the incoherent electromagnetic scattering contribution value determining module is used for determining the incoherent electromagnetic scattering contribution value of the three-dimensional geometric electromagnetic model by adopting a perturbation method;
and the target scattering cross section determining module is used for superposing the contribution value of the coherent scattering component and the incoherent electromagnetic scattering contribution value to obtain a target scattering cross section of the three-dimensional geometric environment electromagnetic model.
9. The apparatus of claim 8, wherein the three-dimensional geometric environment electromagnetic model determination module comprises:
the three-dimensional lattice acquisition submodule is used for acquiring a three-dimensional lattice of the surface of a region to be detected of the planet;
the discrete network body geometrical structure forming submodule is used for forming a discrete network body geometrical structure according to the three-dimensional lattice;
the material model determining submodule is used for determining a material model of the surface of the region to be detected;
and the three-dimensional geometric environment electromagnetic model determining submodule is used for determining the three-dimensional geometric environment electromagnetic model of the planet surface according to the material model and the geometric structure of the discrete network body.
10. The apparatus of claim 8, wherein the inter-bin multiple scattering contribution determining module comprises:
the position determining submodule of the fixed light source is used for determining the position of the light source;
the preset processing submodule is used for presetting the scenery space of the three-dimensional geometric environment electromagnetic model according to the position of the light source;
an initial light beam determination submodule for determining an initial light beam, wherein the initial light beam is a planar-wave-cylindrical-shaped initial light beam generated from a bin;
the surface element intersection judging submodule is used for judging the intersection of the surface elements according to the initial light beam;
an intersecting beam determining submodule for determining intersecting beams in the binning intersection;
a reflected beam and refracted beam determination submodule for determining a reflected beam and a refracted beam of the intersecting beams;
a first iteration execution sub-module for iteratively executing the steps of determining the position of the light source to the reflected light beam and the refracted light beam of the intersecting light beam according to the reflected light beam and the refracted light beam until a tracking cutoff condition is satisfied;
the light beam tree-shaped storage structure establishing submodule is used for establishing a light beam tree-shaped storage structure according to each reflected light beam and each refracted light beam;
a second iteration execution submodule, configured to acquire a light beam before a preset time point from a stack, and iteratively execute the step of determining the position of the light source until a light beam tree-like storage structure is established according to each reflected light beam and each refracted light beam until the stack is empty;
the intersection information determining submodule is used for tracking a path recorded by the light beam tree-shaped storage structure and determining the intersection information of the three-dimensional geometric electromagnetic model surface patch;
the illumination area determining submodule is used for determining an illumination area irradiated by the light beam according to the intersection information;
a scattered field calculation sub-module of the illumination area for calculating a scattered field of the illumination area based on a physical optical algorithm;
and the multiple scattering contribution value determining submodule between the surface elements is used for traversing the light beam tree-shaped storage structure and determining the multiple scattering contribution value between the surface elements of the three-dimensional geometric electromagnetic model.
11. The apparatus of claim 8, wherein the module for determining the scattering contribution from the edge diffraction comprises:
the incident ray determination submodule is used for determining incident rays based on multiple scattering contribution values among surface elements of the three-dimensional geometric electromagnetic model;
the first determining submodule is used for determining the irradiated wedges according to incident light;
the second determining submodule is used for determining a first ray grazing incidence track and a second ray grazing incidence track of two surfaces corresponding to each wedge;
a third determining submodule, configured to determine a first length of the first grazing incidence trajectory and a second length of the second grazing incidence trajectory, respectively;
a fourth determining submodule, configured to determine a scattering contribution value of edge diffraction of the three-dimensional geometric electromagnetic model according to the first length and the second length by using the following formula:
Figure FDA0002685292640000071
wherein E isfwThe edge wave field is represented and,
Figure FDA0002685292640000072
ITand MTRespectively an equivalent edge current and an equivalent edge current, and ITAnd MTRespectively a function of the first length and the second length,
Figure FDA0002685292640000073
is the unit vector of the direction of the incident wave,
Figure FDA0002685292640000074
exp (-jkR)/4 π R is the spherical wave propagation factor, which is the unit vector of the scattered wave direction.
12. The apparatus of claim 10, wherein the electromagnetic scattering contribution determination module comprises:
the subdivision submodule is used for dividing the three-dimensional geometric electromagnetic model into a plurality of surface patches by adopting a triangular surface element;
a patch scattering contribution value determining submodule, configured to obtain parameter information of the following formula from the beam tree storage structure, and determine a patch scattering contribution value:
Figure FDA0002685292640000075
wherein the content of the first and second substances,
Figure FDA0002685292640000076
the expression is as follows:
Figure FDA0002685292640000077
Figure FDA0002685292640000078
η0is the wave impedance in the vacuum and,
Figure FDA0002685292640000079
unit vector of polarization direction of incident magnetic field, H0Is the amplitude of incident magnetic field, R' is the vector of the geometric center position of the triangular surface element, and alpha is
Figure FDA00026852926400000710
Projection on the surface element Si, viIs the vertex coordinate of Si, and v4＝v1；
The electromagnetic scattering contribution value determination submodule of the surface current arrival of the three-dimensional geometric electromagnetic model is used for calculating the electromagnetic scattering contribution value of the surface current arrival of the three-dimensional geometric electromagnetic model according to the scattering contribution value of one surface element through the following formula:
Figure FDA0002685292640000081
13. the apparatus of claim 10, wherein the incoherent electromagnetic scatter contribution determination module is specifically configured to:
obtaining parameter information of the following formula from the light beam tree-shaped storage structure, and determining an incoherent electromagnetic scattering contribution value of the three-dimensional geometric electromagnetic model through the following formula:
σpq＝8|k2δcosθicosθsαpq|2W(kx+kisinθi,ky)；
wherein k is the wave number, kx，kyThe wave number of the incident wave is respectively the component in the x and y directions, delta is the surface height fluctuation root mean square, W (k)x ky) In order to be a function of the normalized roughness spectrum,
Figure FDA0002685292640000082
Figure FDA0002685292640000083
where ρ (u, v) is a surface correlation coefficient, αpqNamely the polarization amplitude coefficient; p and q are the polarization of the scattered and incident waves, respectively.
14. The method apparatus of claim 8, wherein the target scattering cross-section determination module comprises:
a first calculation submodule for calculating an average coherent radar scattering cross-section of the medium target by the following formula:
Figure FDA0002685292640000084
wherein the content of the first and second substances,
Figure FDA0002685292640000085
mean coherent radar cross section of medium object, theta0lFor local incident pitch angle, Rp(θ0l) As reflection coefficient, χ (-2 k)0cosθ0l) As a characteristic function, k0Is the free space wavenumber; p and q are the polarization of the scattered and incident waves, respectively;
a second calculation submodule for calculating a total incoherent scattering cross-section of the three-dimensional geometric electromagnetic model by the following formula:
Figure FDA0002685292640000086
wherein the content of the first and second substances,
Figure FDA0002685292640000091
for the shading function, the expression that the integration is carried out only in the area where the incident wave energy irradiates the curved surface and the observation direction can be seen is as follows:
Figure FDA0002685292640000092
wherein the content of the first and second substances,
Figure FDA0002685292640000093
is the rough surface scattering coefficient, which is a function related to local incident angle, surface dielectric constant, rough surface statistical parameters, and polarization of incident wave and scattering wave;
a third calculating submodule, configured to calculate a target scattering cross section of the three-dimensional geometric environment electromagnetic model according to the average coherent radar scattering cross section and the total incoherent scattering cross section of the medium target by using the following formula:
Figure FDA0002685292640000094
CN202010974486.4A 2020-09-16 2020-09-16 Target scattering cross section calculation method and device Active CN112213704B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202010974486.4A CN112213704B (en) 2020-09-16 2020-09-16 Target scattering cross section calculation method and device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202010974486.4A CN112213704B (en) 2020-09-16 2020-09-16 Target scattering cross section calculation method and device

Publications (2)

Publication Number Publication Date
CN112213704A true CN112213704A (en) 2021-01-12
CN112213704B CN112213704B (en) 2024-04-09

Family

ID=74050610

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202010974486.4A Active CN112213704B (en) 2020-09-16 2020-09-16 Target scattering cross section calculation method and device

Country Status (1)

Country Link
CN (1) CN112213704B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114387594A (en) * 2022-01-17 2022-04-22 中国人民解放军63660部队 High-frequency electromagnetic scattering shielding identification method

Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6580388B1 (en) * 2001-11-20 2003-06-17 The United States Of America As Represented By The Secretary Of The Navy Calculation methodology for complex target signatures
CN101216556A (en) * 2007-12-27 2008-07-09 复旦大学 Electrically Large complex target and rugged face background composite electromagnetic scattering numerical value emulation method
US20100066595A1 (en) * 2008-09-18 2010-03-18 Lee Chul J Electromagnetic (em) solver using a shooting bouncing ray (sbr) technique
CN102226840A (en) * 2011-03-23 2011-10-26 中国人民解放军海军工程大学 Radar cross-section layered calculation method of ship target within atmospheric duct range
EP2887092A1 (en) * 2013-12-18 2015-06-24 BAE SYSTEMS plc Computing radar cross section
CN108388732A (en) * 2018-02-27 2018-08-10 中国人民解放军空军工程大学 Plunder extra large Target multipath scattering properties emulated computation method and system
CN108829906A (en) * 2017-12-29 2018-11-16 西安电子科技大学 A kind of rescattering calculation method of complex target to background light radiation
KR20190059384A (en) * 2017-11-23 2019-05-31 인하대학교 산학협력단 Apparatus and method for measuring of radar cross section based on physical theory of diffraction
CN110208760A (en) * 2019-05-27 2019-09-06 西安空间无线电技术研究所 A kind of radar return emulation mode based on time domain up-sampling
CN110457812A (en) * 2019-08-08 2019-11-15 北京航空航天大学 A kind of recognition methods and system of complex target strong electromagnetic scattering source
CN110927687A (en) * 2019-11-09 2020-03-27 中国电波传播研究所（中国电子科技集团公司第二十二研究所） Meteor detection method based on incoherent scattering radar
CN111537987A (en) * 2020-05-07 2020-08-14 中国科学院地质与地球物理研究所 Genetic algorithm-based incoherent scattering radar data inversion method

Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6580388B1 (en) * 2001-11-20 2003-06-17 The United States Of America As Represented By The Secretary Of The Navy Calculation methodology for complex target signatures
CN101216556A (en) * 2007-12-27 2008-07-09 复旦大学 Electrically Large complex target and rugged face background composite electromagnetic scattering numerical value emulation method
US20100066595A1 (en) * 2008-09-18 2010-03-18 Lee Chul J Electromagnetic (em) solver using a shooting bouncing ray (sbr) technique
CN102226840A (en) * 2011-03-23 2011-10-26 中国人民解放军海军工程大学 Radar cross-section layered calculation method of ship target within atmospheric duct range
EP2887092A1 (en) * 2013-12-18 2015-06-24 BAE SYSTEMS plc Computing radar cross section
KR20190059384A (en) * 2017-11-23 2019-05-31 인하대학교 산학협력단 Apparatus and method for measuring of radar cross section based on physical theory of diffraction
CN108829906A (en) * 2017-12-29 2018-11-16 西安电子科技大学 A kind of rescattering calculation method of complex target to background light radiation
CN108388732A (en) * 2018-02-27 2018-08-10 中国人民解放军空军工程大学 Plunder extra large Target multipath scattering properties emulated computation method and system
CN110208760A (en) * 2019-05-27 2019-09-06 西安空间无线电技术研究所 A kind of radar return emulation mode based on time domain up-sampling
CN110457812A (en) * 2019-08-08 2019-11-15 北京航空航天大学 A kind of recognition methods and system of complex target strong electromagnetic scattering source
CN110927687A (en) * 2019-11-09 2020-03-27 中国电波传播研究所（中国电子科技集团公司第二十二研究所） Meteor detection method based on incoherent scattering radar
CN111537987A (en) * 2020-05-07 2020-08-14 中国科学院地质与地球物理研究所 Genetic algorithm-based incoherent scattering radar data inversion method

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
ZHUO LI: "Electromagnetic Scattering Characteristics of PEC Targets in the Terahertz Regime", 《IEEE ANTENNAS AND PROPAGATION MAGAZINE 》, vol. 51, no. 1, pages 39, XP011257601 *
陈刚: "太赫兹低频段随机粗糙金属板散射特性研究", 《雷达学报》, vol. 7, no. 1, pages 75 - 82 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114387594A (en) * 2022-01-17 2022-04-22 中国人民解放军63660部队 High-frequency electromagnetic scattering shielding identification method
CN114387594B (en) * 2022-01-17 2024-04-19 中国人民解放军63660部队 High-frequency electromagnetic scattering shielding identification method

Also Published As

Publication number Publication date
CN112213704B (en) 2024-04-09

Similar Documents

Publication Publication Date Title
Lukács et al. Faithful least-squares fitting of spheres, cylinders, cones and tori for reliable segmentation
CN108829906B (en) Secondary scattering calculation method for background light radiation by complex target
CN110907901B (en) Sea warfare passive interference calculation and evaluation method based on TDSBR
IL266060A (en) Robust merge of 3d textured meshes
JP7017684B2 (en) Three-dimensional reconstruction method based on half-value probability density distribution
Beekmans et al. Cloud photogrammetry with dense stereo for fisheye cameras
CN115754959A (en) Method for establishing target-environment composite radar scattering cross section calculation model
CN112213704B (en) Target scattering cross section calculation method and device
Noguchi et al. Microscopic shape from focus using a projected illumination pattern
CN110186415B (en) Method for acquiring channel information aiming at ray tracing of reflection or scattering propagation
Knaell Three-dimensional SAR from practical apertures
CN115205354B (en) Phased array laser radar imaging method based on RANSAC and ICP point cloud registration
CN114720953A (en) Method and device for extracting geometric parameters of building based on CSAR image
Drap et al. Underwater multimodal survey: Merging optical and acoustic data
Kong 3D image reconstruction of marine plankton based on virtual reality
Wang et al. An affine transform center line extraction and discontinuity deviation correction method for non-orthogonal grid laser
CN111144226A (en) Sea surface infrared small target detection method based on sea clutter curvature characteristic
CN113126053B (en) Method and device for evaluating radar cross section of ship
CN117765172B (en) Method and device for three-dimensional reconstruction of remote sensing image
Li et al. Notice of Retraction: Optical Sources Optimization for 3D Reconstruction Based on Underwater Vision System
Komuro et al. Numerical evaluation of transport-of-intensity phase imaging with oblique illumination for refractive index tomography
Partridge et al. Three-dimensional surface reconstruction using emission polarization
Dickey et al. Recovering shape from shadows in synthetic aperture radar imagery
Al-Shimiry et al. Water depth estimation by analyzing laser spot images using digital image processing
Xu et al. A Novel Passive Millimeter-wave Local Encryption Algorithm Research

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant