CN112068101A - Target scattering separation method based on mode filtering - Google Patents

Target scattering separation method based on mode filtering Download PDF

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CN112068101A
CN112068101A CN202010943150.1A CN202010943150A CN112068101A CN 112068101 A CN112068101 A CN 112068101A CN 202010943150 A CN202010943150 A CN 202010943150A CN 112068101 A CN112068101 A CN 112068101A
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wave
mode
separated
target
directional diagram
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CN112068101B (en
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张帅
周肖
龚书喜
宋子璇
白婵
柏文泉
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Xidian University
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    • 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
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
    • G01N27/82—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws
    • G01N27/83—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws by investigating stray magnetic fields
    • 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
    • G01S7/411—Identification of targets based on measurements of radar reflectivity
    • 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

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Abstract

The invention provides a target scattering separation method based on mode filtering, which mainly solves the problem that the prior art can not accurately separate the scattering of each area of a target through single-frequency point measurement. The implementation scheme is as follows: acquiring field data of the whole space of the whole scatterer and preprocessing the field data; unfolding a far-field directional diagram on the whole space based on spherical waves to obtain spherical wave mode coefficients; and filtering high-order mode items in the spherical wave mode coefficient through a mode filter, and finally obtaining the filtered scattering field of each region of the whole scatterer. The invention only needs single-frequency point scattering data of the whole scatterer, so that the scattering field of each region of the whole scatterer can be separated from measurement scenes with extremely narrow bandwidth such as UHF/VHF, and meanwhile, the scattering measurement efficiency of each region is improved. Can be used for target regional scattering measurement.

Description

Target scattering separation method based on mode filtering
Technical Field
The invention belongs to the technical field of electromagnetism, and particularly relates to a target scattering separation method which can be used for target regional scattering measurement.
Background
The scattering measurement of the airplane is one of the main methods for judging the coating failure of the airplane body, the airplane can possibly cause the coating damage of a certain part after executing a flight task to cause the change of scattering performance, the airplane body can be divided into regions in the prior art, the regions are detected for multiple times, and the scattering performance of each region before and after executing the task is compared respectively to judge the damaged region of the coating. However, this method may cause secondary damage during disassembly and shipping inspection. When scattering is measured outdoors, a large measurement error may be formed due to the harsh electromagnetic environment.
For example, a patent application with application publication number CN201910767035.0 entitled "a time domain gate transformation method and apparatus" discloses a method for separating and removing stray influence outside a target region, which is mainly based on a time domain gate technology, and is characterized in that frequency domain RCS data of a target to be detected is acquired, the frequency domain RCS data is transformed into time domain RCS data according to a frequency domain time domain transformation method, a time domain gate function for time domain gating is acquired, the time domain gate function is applied to the time domain RCS data to obtain time domain gating data, the time domain gating data is transformed into frequency domain data according to a time domain frequency domain transformation method, the frequency domain data is renormalized to remove data aliasing, but the technology needs electromagnetic measurement data of a broadband to separate and remove stray influence outside the target region, the separation effect is influenced by measurement bandwidth, especially for measurement scenes with narrower absolute bandwidth such as UHF/VHF, it is difficult to separate stray influences outside the target area.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a target scattering separation method based on mode filtering, which aims to solve the problem of accurately separating the scattering of each region of a target through single-frequency point measurement and improve the scattering measurement efficiency of each region.
In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:
(1) for the whole scattererThe scattered field data are sampled to obtain a far field directional diagram covering the scattered field data of the spherical area of the part
Figure BDA0002674356370000011
To far field directional diagram
Figure BDA0002674356370000012
Coordinate translation operation and directional diagram zero filling operation are carried out to obtain a far field directional diagram on the whole space
Figure BDA0002674356370000021
Wherein theta is a pitch angle in a rectangular coordinate system of a measuring space,
Figure BDA0002674356370000022
measuring the azimuth angle in the space rectangular coordinate system;
(2) for far field directional diagram in the whole space
Figure BDA0002674356370000023
Based on the spherical wave expansion, obtaining a spherical wave mode expansion coefficient:
(2a) for far field directional diagram in the whole space
Figure BDA0002674356370000024
Based on spherical wave expansion, the expansion expression is as follows:
Figure BDA0002674356370000025
wherein s represents an emergent wave, a represents an incident wave, m is a mode term mark having a value of 0 to infinity, n is a mode term mark having a value of 1 to infinity,
Figure BDA0002674356370000026
the m-n spherical wave expansion coefficient of the outgoing wave of the transverse electric wave TE,
Figure BDA0002674356370000027
m.n spherical waves of TE incident waveThe coefficient of expansion is such that,
Figure BDA0002674356370000028
is an m-n term spherical wave expansion coefficient of the outgoing wave of the transverse magnetic wave TM,
Figure BDA0002674356370000029
is the m & n spherical wave expansion coefficient of TM incident wave,
Figure BDA00026743563700000210
is a TE emergent wave mode of m-n terms,
Figure BDA00026743563700000211
is a TE incident wave mode of m-n terms,
Figure BDA00026743563700000212
is an m.n term TM emergent wave mode,
Figure BDA00026743563700000213
is an m.n term TM incident wave mode, and j is an imaginary number symbol;
(2b) cutting out the above
Figure BDA00026743563700000214
The A term and the B term in the spherical wave expansion expression of the method obtain a complete scattering information far-field directional diagram capable of containing a target scatterer to be separated
Figure BDA00026743563700000215
Figure BDA00026743563700000216
Wherein B is 2nextpow2(MN)，MN＝[kR0]+ u, a ═ 2B, u is a self-defined integer, R0Is the radius of the smallest sphere which takes the origin of the measurement coordinate as the center and surrounds the object to be separated;
(2c) for the complete scattering information far-field directional diagram containing the target scatterer to be separated
Figure BDA00026743563700000217
Spreading to obtain spherical wave spreading coefficient of TE wave
Figure BDA00026743563700000218
And the spherical wave expansion coefficient of TM wave
Figure BDA00026743563700000219
Figure BDA00026743563700000220
Figure BDA00026743563700000221
Wherein i ═ s or a, k are wavenumbers;
(3) filtering out spherical wave high-order mode items to obtain a far field directional diagram of the target to be separated after filtering
Figure BDA00026743563700000222
(3a) Obtaining the number of truncated modes N of the spherical wave function0：N0＝[kR1]+v，
Wherein, [ kR ]1]Is kR1Integer rounded up, R1Taking the aperture center of the target to be separated as an origin and the radius of a minimum ball surrounding the target to be separated, wherein v is a self-setting integer;
(3b) selecting a mode filter Filter (n) for filtering out the spherical wave expansion coefficient of the TE wave
Figure BDA0002674356370000031
And the spherical wave expansion coefficient of TM wave
Figure BDA0002674356370000032
Obtaining the TE wave mode coefficient representing the target to be separated from the medium-high order mode coefficient
Figure BDA0002674356370000033
And TM wave mode coefficient
Figure BDA0002674356370000034
(3c) Intercepting the complete scattering information far field directional diagram containing the target scatterer to be separated
Figure BDA0002674356370000035
2N in spherical wave expansion expression0 2Term, obtaining far field pattern of the filtered object to be separated
Figure BDA0002674356370000036
Figure BDA0002674356370000037
(4) Obtaining far field directional diagram of target to be separated in array
Figure BDA0002674356370000038
And the far field directional diagram of the target to be separated after filtering
Figure BDA0002674356370000039
Far field pattern in array with object to be separated
Figure BDA00026743563700000310
And comparing, and when the horizontal section pattern curves or the vertical section pattern curves of the two can be matched, successfully separating the scattered field of the target to be separated from the scattered field of the whole scatterer.
Compared with the prior art, the invention has the following advantages:
according to the invention, single-frequency point scattered field data of the whole scatterer are sampled, and a scattered field directional diagram is expanded and filtered based on spherical waves, so that scattered fields of all parts in the whole scatterer can be obtained through a mathematical post-processing method, the requirement on a broadband measurement system is reduced, and the scattering measurement efficiency and precision of all parts are improved; meanwhile, the requirement on a broadband measurement system is reduced, so that the scattering fields of all parts of the whole scatterer can be separated for UHF/VHF frequency band measurement scenes.
Drawings
FIG. 1 is a flow chart of an implementation of an embodiment of the present invention;
FIG. 2 is a diagram of a three-unit metal patch array model in the scatterer to be measured according to the present invention;
fig. 3 is a two-station RCS cross-sectional pattern of a three-element metal patch array in a scatterer to be measured according to the present invention;
fig. 4 is an in-array two-station RCS cross-sectional pattern of one unit in a three-unit metal patch array in a scatterer to be measured according to the present invention;
figure 5 is a cross-sectional view of a dual station RCS of one cell isolated from a three-cell metal patch array in a scatterer under test using the present invention;
FIG. 6 is a comparison diagram of the total field pattern of the three-unit metal patch array in the scatterer to be measured, the in-array pattern of one unit, and the unit pattern separated from the array in the vertical azimuth plane;
fig. 7 is a comparison graph of the total field pattern of the three-element metal patch array coated with the wave-absorbing material in the scatterer to be measured of the present invention, the in-array pattern of one element, and the element pattern separated from the array in the vertical azimuth plane.
Detailed Description
Embodiments and effects of the present invention will be described in further detail below with reference to the accompanying drawings.
Referring to FIG. 2, the scatterer used in this example is three identical metal patch units M, M placed in the XOY plane from the three-dimensional coordinate system XYZ2,M3Formed patch array M ═ M1,M2,M3]Directly above it is a unit amplitude plane wave, M2The aperture center of the unit is located at the origin of coordinates of XYZ of a three-dimensional coordinate system, M1And M3The distance from the aperture center of the unit to the coordinate origin of the three-dimensional coordinate system XYZ is p, and the size of each patch unit is lambdaλ, where λ is the wavelength.
Referring to fig. 1, the implementation steps of the invention are as follows:
step 1, obtaining scattering field measurement data of scatterers and preprocessing the scattering field measurement data to obtain far field directional diagrams on the whole space
Figure BDA0002674356370000041
(1a) Sampling scattered field data of the whole scatterer, namely sampling scattered field data of a three-unit metal patch array M, wherein the sampling of the scattered field data needs to be performed by a scanning mode to perform area sampling:
the scanning method of the present embodiment selects and adopts but is not limited to planar scanning, and the area of sampling adopts but is not limited to far field; obtaining the far field directional diagram of the three-unit metal patch array M
Figure BDA0002674356370000042
Wherein theta is a pitch angle in a rectangular coordinate system of a measuring space,
Figure BDA0002674356370000043
measuring the azimuth angle in the space rectangular coordinate system;
(1b) will direct far field pattern
Figure BDA0002674356370000044
Translating to the aperture center of the patch unit to be separated to obtain a translated far-field directional diagram
Figure BDA0002674356370000045
Figure BDA0002674356370000046
Wherein, (x, y, z) is the caliber center coordinate of the patch unit to be separated,
Figure BDA0002674356370000047
representing the phase of coordinate translation, j is an imaginary number symbol, and k is a wave number;
(1c) for far field directional diagram obtained after translation
Figure BDA0002674356370000051
Carrying out directional diagram zero filling operation to obtain a far field directional diagram on the whole space
Figure BDA0002674356370000052
Step 2, aiming far field directional diagram on the whole space
Figure BDA0002674356370000053
Based on the spherical wave expansion, obtaining a spherical wave mode expansion coefficient:
(2a) for far field directional diagram in the whole space
Figure BDA0002674356370000054
Based on the spherical wave expansion, namely expanding into the superposition of a series of spherical wave mode terms, the expansion expression is as follows:
Figure BDA0002674356370000055
wherein s represents an emergent wave, a represents an incident wave, m is a mode term mark having a value of 0 to infinity, n is a mode term mark having a value of 1 to infinity,
Figure BDA0002674356370000056
the m-n spherical wave expansion coefficient of the outgoing wave of the transverse electric wave TE,
Figure BDA0002674356370000057
is the m-n spherical wave expansion coefficient of TE incident wave,
Figure BDA0002674356370000058
is an m-n term spherical wave expansion coefficient of the outgoing wave of the transverse magnetic wave TM,
Figure BDA0002674356370000059
is the m & n spherical wave expansion coefficient of TM incident wave,
Figure BDA00026743563700000510
is a TE emergent wave mode of m-n terms,
Figure BDA00026743563700000511
is a TE incident wave mode of m-n terms,
Figure BDA00026743563700000512
is an m.n term TM emergent wave mode,
Figure BDA00026743563700000513
is m.n term TM incident wave mode;
the front A term and the front B term of a series of spherical wave mode terms in the expansion expression contain complete scattering information of the three-unit metal patch array M;
(2b) cutting out the above
Figure BDA00026743563700000514
The first A term and the B term in the spherical wave expansion expression are used for obtaining a complete scattering information far field directional diagram capable of containing a to-be-three-unit metal patch array M
Figure BDA00026743563700000515
Figure BDA00026743563700000516
Wherein B is 2nextpow2(MN)，MN＝[kR0]+ u, a ═ 2B, u is a self-defined integer, R0The radius of the minimum sphere which takes the origin of the measurement coordinate as the center and surrounds the paster unit to be separated; when separating M1,M3When the scattered field of the patch unit is present,
Figure BDA00026743563700000517
when separating M2When the scattered field of the patch unit is present,
Figure BDA00026743563700000518
(2c) according to the complete scattering information far-field directional diagram containing the target scatterer to be separated
Figure BDA00026743563700000519
Obtaining a spherical wave expansion coefficient of the TE wave
Figure BDA00026743563700000520
And the spherical wave expansion coefficient of TM wave
Figure BDA00026743563700000521
Figure BDA0002674356370000061
Figure BDA0002674356370000062
Wherein i ═ s or a.
Step 3, filtering high-order mode items of the spherical waves to obtain a far-field directional diagram of the target to be separated after filtering
Figure BDA0002674356370000063
(3a) Obtaining the number of truncated modes N of the spherical wave function0：
(3a1) Setting an integer v, wherein the integer v depends on the coordinate position relation of the source point and the field point and the required precision;
(3a2) acquiring the radius of a minimum ball which takes the aperture center of the target to be separated as an origin and surrounds the target to be separated:
Figure BDA0002674356370000064
(3a3) from the results of (3a1) and (3a2), calculation was madeNumber of truncated modes N of spherical wave function0
N0＝[kR1]+ v, wherein, [ kR1]Is kR1An integer rounded up;
(3b) selecting a mode filter Filter (n) for filtering out the spherical wave expansion coefficient of the TE wave
Figure BDA0002674356370000065
And the spherical wave expansion coefficient of TM wave
Figure BDA0002674356370000066
Medium high order mode coefficient:
the conventional mode filter includes a rectangular window, a cosine square window, a hanning window, a hamming window, a blackman window, etc., and the mode filter (n) of the present embodiment is a rectangular window, i.e., a rectangular window
Figure BDA0002674356370000067
TE wave mode coefficient representing target to be separated is obtained through rectangular window
Figure BDA0002674356370000068
And TM wave mode coefficient
Figure BDA0002674356370000069
Figure BDA00026743563700000610
Figure BDA00026743563700000611
(3c) Intercepting the spherical wave expansion expression in the step (2b)
Figure BDA00026743563700000612
Spherical wave mode front 2N in0 2Item, obtaining far field directional diagram of the filtered patch unit to be separated
Figure BDA00026743563700000613
Figure BDA00026743563700000614
And 4, carrying out visual analysis on the far-field directional diagram of the to-be-separated patch unit obtained after filtering, and determining whether to finally separate the scattered field of the to-be-separated patch unit from the whole scattered field of the three-unit metal patch M.
(4.1) sampling scattered field data of the to-be-separated patch unit in the three-unit metal patch array M, in this example, the first unit M in the three-unit metal patch array M1Sampling the scattered field of the unit to obtain the far field directional diagram of the unit in the array
Figure BDA0002674356370000071
And the scattering field of the to-be-separated patch unit is used as a reference for whether the scattering field is separated from the whole scattering field of the three-unit metal patch array M;
(4.2) obtaining the far field directional diagram of the to-be-separated patch unit after filtering
Figure BDA0002674356370000072
With reference far field pattern
Figure BDA0002674356370000073
And comparing, namely successfully separating the scattered field of the to-be-separated patch unit from the integral scattered field of the three-unit metal patch array M when the vertical azimuth plane directional diagram curves of the three-unit metal patch array M can be matched.
The technical effects of the invention are further explained by combining simulation experiments as follows:
1. the experimental environment is as follows:
experimental software: FEKO + WinProp2018, MATLAB R2017a,
configuration of an experimental computer: intel (R) core (TM) i7-8700K CPU 3.70GHZ, Windows 10(Pro)
The experimental conditions are as follows: a plane wave of unit amplitude with a frequency of 2GHZ is irradiated to a three-unit metal patch array M along a Z-axis direction of a three-dimensional coordinate system XYZ.
2. The experimental contents are as follows:
experiment 1, measuring a scattering field of a three-unit metal patch array M by using FEKO + WinProp2018 software to obtain a double-station RCS (radar cross section) directional diagram of the three-unit metal patch array M, as shown in FIG. 3;
experiment 2, FEKO + WinProp2018 software is used for aligning the second unit M in the three-unit metal patch array M2Measuring the scattered field of the unit to obtain M2The dual station RCS cross-sectional pattern of the cell, as shown in fig. 4;
experiment 3, using MATLAB R2017a software, the scattered field of the three-unit metal patch array M was developed and mode-filtered based on spherical waves, resulting in M separated from fig. 32The dual station RCS cross-sectional pattern of the cell, as shown in fig. 5;
the far field patterns in the vertical azimuth plane obtained in experiment 1, experiment 2 and experiment 3 were compared as shown in fig. 6.
Comparing fig. 4 and 5, the shadow distribution of the two is substantially the same, M in the three-unit metal patch array M in fig. 62Far field directional diagram of unit in vertical azimuth plane and M separated from three-unit metal patch array M2The unit is jointed with the far field directional diagram curve on the vertical azimuth surface, the goodness of fit is high, and M is successfully matched2The scattering field of the unit is separated from the whole scattering field of the three-unit metal patch array M.
Experiment 4, M in three-unit metal patch array1,M3The patch unit is coated with the wave-absorbing material, and the experiment 1, the experiment 2 and the experiment 3 are repeated, and the result is shown in fig. 7.
As can be seen from FIG. 7, M in the three-unit metal patch array coated with the wave-absorbing material2Far field directional diagram of unit in vertical azimuth plane and M separated from three-unit metal patch array coated with wave absorbing material2The unit is jointed with the far field directional diagram curve on the vertical azimuth surface, the goodness of fit is high, and M is successfully matched2Scattered field of unit from coating absorbing materialAnd separating the whole scattering field of the three-unit metal patch array after the material is fed.

Claims (6)

1. A target scattering separation method based on mode filtering is characterized by comprising the following steps:
(1) sampling scattered field data of the whole scatterer to obtain a far field directional diagram covering scattered field data of a spherical area of a part
Figure FDA0002674356360000011
To far field directional diagram
Figure FDA0002674356360000012
Coordinate translation operation and directional diagram zero filling operation are carried out to obtain a far field directional diagram on the whole space
Figure FDA0002674356360000013
Wherein theta is a pitch angle in a rectangular coordinate system of a measuring space,
Figure FDA0002674356360000014
measuring the azimuth angle in the space rectangular coordinate system;
(2) for far field directional diagram in the whole space
Figure FDA0002674356360000015
Based on the spherical wave expansion, obtaining a spherical wave mode expansion coefficient:
(2a) for far field directional diagram in the whole space
Figure FDA0002674356360000016
Based on spherical wave expansion, the expansion expression is as follows:
Figure FDA0002674356360000017
wherein s represents an emergent wave, a represents an incident wave, and m is a mode entry mark with a value of 0 to infinityNote that n is a mode item mark with a value of 1 to infinity,
Figure FDA0002674356360000018
the m-n spherical wave expansion coefficient of the outgoing wave of the transverse electric wave TE,
Figure FDA0002674356360000019
is the m-n spherical wave expansion coefficient of TE incident wave,
Figure FDA00026743563600000110
is an m-n term spherical wave expansion coefficient of the outgoing wave of the transverse magnetic wave TM,
Figure FDA00026743563600000111
is the m & n spherical wave expansion coefficient of TM incident wave,
Figure FDA00026743563600000112
is a TE emergent wave mode of m-n terms,
Figure FDA00026743563600000113
is a TE incident wave mode of m-n terms,
Figure FDA00026743563600000114
is an m.n term TM emergent wave mode,
Figure FDA00026743563600000115
is an m.n term TM incident wave mode, and j is an imaginary number symbol;
(2b) cutting out the above
Figure FDA00026743563600000116
The A term and the B term in the spherical wave expansion expression of the method obtain a complete scattering information far-field directional diagram capable of containing a target scatterer to be separated
Figure FDA00026743563600000117
Figure FDA00026743563600000118
Wherein B is 2nextpow2(MN)，MN＝[kR0]+ u, a ═ 2B, u is a self-defined integer, R0Is the radius of the smallest sphere which takes the origin of the measurement coordinate as the center and surrounds the object to be separated;
(2c) for the complete scattering information far-field directional diagram containing the target scatterer to be separated
Figure FDA00026743563600000119
Processing to obtain spherical wave expansion coefficient of TE wave
Figure FDA00026743563600000120
And the spherical wave expansion coefficient of TM wave
Figure FDA00026743563600000121
Figure FDA0002674356360000021
Figure FDA0002674356360000022
Wherein i ═ s or a, k are wavenumbers;
(3) filtering out spherical wave high-order mode items to obtain a far field directional diagram of the target to be separated after filtering
Figure FDA0002674356360000023
(3a) Obtaining the number of truncated modes N of the spherical wave function0：N0＝[kR1]+v，
Wherein, [ kR ]1]Is kR1Integer rounded up, R1Is based on the aperture center of the target to be separatedThe radius of a smallest sphere which is a point and surrounds the target to be separated, and v is a self-set integer;
(3b) selecting a mode filter Filter (n) for filtering out the spherical wave expansion coefficient of the TE wave
Figure FDA0002674356360000024
And the spherical wave expansion coefficient of TM wave
Figure FDA0002674356360000025
Obtaining the TE wave mode coefficient representing the target to be separated from the medium-high order mode coefficient
Figure FDA0002674356360000026
And TM wave mode coefficient
Figure FDA0002674356360000027
(3c) Intercepting the complete scattering information far field directional diagram containing the target scatterer to be separated
Figure FDA0002674356360000028
2N in spherical wave expansion expression0 2Term, obtaining far field pattern of the filtered object to be separated
Figure FDA0002674356360000029
Figure FDA00026743563600000210
(4) Obtaining far field patterns of objects to be separated in the whole scatterer
Figure FDA00026743563600000211
And the far field directional diagram of the target to be separated after filtering
Figure FDA00026743563600000212
And wait to divideFar field pattern in array from target
Figure FDA00026743563600000213
And comparing, and when the horizontal section pattern curves or the vertical section pattern curves of the two can be matched, successfully separating the scattered field of the target to be separated from the scattered field of the whole scatterer.
2. The method of claim 1, wherein the scattered field data of the entire scatterer is sampled in (1) in a scanning manner selected from one of a plane, a cylinder, and a sphere, and the sampled region is selected from one of a near field, a quasi-far field, and a far field.
3. The method of claim 1, wherein (1) the far-field pattern is aligned
Figure FDA0002674356360000031
Performing coordinate translation operation to obtain far-field directional diagram
Figure FDA0002674356360000032
Translating to the aperture center of the target to be separated to obtain a translated scattered field directional diagram
Figure FDA0002674356360000033
Is represented as follows:
Figure FDA0002674356360000034
wherein (x, y, z) is the aperture center coordinate of the object to be separated,
Figure FDA0002674356360000035
denotes the phase of the coordinate shift, j is the sign of the imaginary number, and k is the wave number.
4. The method of claim 1, wherein the mode filter (n) selected in (3b) is any one of a rectangular window, a cosine square window, a hanning window, a hamming window, and a blackman window.
5. The method according to claim 1, wherein the TE wave mode coefficients characterizing the objects to be separated are obtained in (3b)
Figure FDA0002674356360000036
Is represented as follows:
Figure FDA0002674356360000037
wherein Filter (n) is the selected mode filter,
Figure FDA0002674356360000038
is the spherical wave expansion coefficient of the TE wave.
6. The method according to claim 1, wherein TM wave mode coefficients characterizing the objects to be separated are obtained in (3b)
Figure FDA0002674356360000039
Is represented as follows:
Figure FDA00026743563600000310
wherein Filter (n) is the selected mode filter,
Figure FDA00026743563600000311
is the spherical wave expansion coefficient of the TM wave.
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