Inclined flying insect body shape parameter estimation based on scattering matrix recovery

Abstract

The invention provides oblique flying insect body shape parameter estimation based on scattering matrix recovery, and belongs to the technical field of insect radars, and the method comprises the steps: firstly calculating a three-dimensional attitude angle of an insect body axis relative to a radar antenna coordinate system; then, according to the solved three-dimensional attitude angle, recovering a scattering matrix obtained by measuring the insect at the angle to a traditional level flight attitude scattering matrix; and finally, estimating the body shape parameters of the insect based on a traditional body shape parameter inversion method of the flat-flight attitude insect. Therefore, the method can be used for measuring the body shape parameter of the insect in any flight attitude by the radar, and the huge breakthrough of estimating the body shape parameter of the insect from the traditional fixed attitude observation to any attitude observation is realized for the first time.

Description

Technical Field

[0001] The present invention belongs to the technical field of insect radar, and particularly relates to an estimation of the body size parameters of obliquely flying insects based on the recovery of the scattering matrix. Background Art

[0002] So far, the measurement of the biological parameters of insects crossing the insect radar beam has been based on the assumption that the insects maintain a horizontal flight attitude. This assumption simplifies the measurement model to a certain extent, but it is not entirely accurate in reality. It is reasonable to imagine that during the cruising stage of insect migration, the body is mainly in a horizontal flight attitude; while during the takeoff and landing stages, the body attitude of the insects will be inclined. When the insects fly obliquely, the radar wave observed vertically is no longer vertically incident, and the surface of the insect's body facing the radar has changed. Since the electromagnetic scattering of the insects is sensitive to the attitude, this will obviously affect the echo characteristics of the insects, and further affect the target biological parameters measured by the insect radar, such as body length, body weight, etc. In addition, when the radar beam is not vertically upward, for example, when the tracking radar continuously measures the insects, the yaw angle, pitch angle, and roll angle of the insects relative to the polarization plane of the radar incident wave are not 0. At this time, the traditional insect body size parameter estimation algorithm is no longer applicable. Therefore, in practical applications, the relative relationship between the flight attitude of the insects and the radar beam is often more complex. In order to improve the accuracy of insect body size parameter estimation, it is necessary to consider the scattering characteristics of the insects in different flight attitudes.

[0003] In summary, the existing insect radar measurement technology has certain limitations in the case of complex and variable insect flight attitudes. In order to overcome these limitations, it is urgent to study the body size parameter estimation algorithm for non-horizontal attitude insects in order to provide more accurate measurement results in a wider range of application scenarios. Summary of the Invention

[0004] To solve the above problems, the present invention provides a method and system for estimating the body size parameters of obliquely flying insects based on the recovery of the scattering matrix, which can be used for the radar to measure the body size parameters of insects in any flight attitude.

[0005] A method for estimating the body size parameters of obliquely flying insects based on the recovery of the scattering matrix includes the following steps: S1: Based on the projection relationship between the body axis of the obliquely flying insect and the antenna polarization plane, obtain the three-dimensional attitude angles of the body axis of the obliquely flying insect relative to the antenna polarization coordinate system and , where is the angle between the projection of the body axis of the obliquely flying insect on the antenna polarization plane and the H polarization direction of the electromagnetic wave, is the angle between the body axis of the obliquely flying insect and the antenna polarization plane; S2: Equivalent the obliquely flying insect to an oblate spheroid, and construct the polarization scattering matrix of the obliquely flying posture of the oblate spheroid insect according to Rayleigh scattering, where each component of the polarization scattering matrix of the obliquely flying posture is a three-dimensional attitude angle and , the scattering amplitude along the body axis direction of the oblate spheroid insect and the scattering amplitude perpendicular to the body axis direction joint expression; S3: Based on the polarization scattering matrix of the obliquely flying posture, calculate the scattering amplitude and the scattering amplitude , thereby reconstructing the polarization scattering matrix of the level flying posture of the oblate spheroid insect ; S4: Invert the body size parameters of the obliquely flying insect based on the polarization scattering matrix of the level flying posture.

[0006] Furthermore, in step S1, the method for obtaining the three-dimensional attitude angles and of the body axis of the obliquely flying insect relative to the antenna polarization coordinate system is as follows: Obtain the rotation matrix of the body axis of the insect relative to the antenna polarization coordinate system of the polarization plane as follows:

[0007] Assume that the initial body axis direction of the insect is along the positive X-axis direction of the antenna polarization coordinate system . After rotation by the rotation matrix , the new direction of the insect body axis is obtained; Based on the new direction of the insect body axis, obtain the included angle as follows:

[0008] Based on the new direction of the insect body axis, obtain the included angle as follows:

[0009] where, , , are the components of the new direction of the insect body axis on the X, Y, and Z axes of the antenna polarization coordinate system respectively.

[0010] Furthermore, the polarization scattering matrix in step S2 is:

[0011] Among them, is the polarization scattering matrix in the oblique flight attitude in the polarization channel hh component, is the polarization scattering matrix in the oblique flight attitude in the polarization channel hv component, is the polarization scattering matrix in the oblique flight attitude in the polarization channel vh component, is the polarization scattering matrix in the oblique flight attitude in the polarization channel vv component, and there are:

[0012]

[0013]

[0014] Among them, is the scattering amplitude of the prolate ellipsoid insect along the body axis direction, is the scattering amplitude of the prolate ellipsoid insect perpendicular to the body axis direction.

[0015] Furthermore, in step S3, the calculation methods of the scattering amplitudes and the scattering amplitude are as follows: Construct the level flight attitude polarization scattering matrix when the insect body axis is parallel to the antenna H polarization direction as follows:

[0016] Among them, the scattering amplitudes , are unknowns related to the three-dimensional attitude angles and ; Construct the mapping relationship between the four components of the oblique flight attitude polarization scattering matrix , , , and , as follows:

[0017] Based on the above mapping relationship, perform the inverse operation of the matrix to solve the scattering components , , and reconstruct the level flight attitude polarization scattering matrix .

[0018] Furthermore, the polarization scattering matrix in the oblique flight attitude is obtained as follows: Based on the field amplitude received by the antenna obtain the polarization scattering matrix in the oblique flight attitude The general expressions of each component are as follows:

[0019] Wherein, is the dielectric constant of the environment where the obliquely flying insect is located, is the wave number in the medium, , are respectively the electric field direction and magnetic field direction of the incident wave incident on the obliquely flying insect, , are respectively the electric field direction and magnetic field direction of the scattered wave scattered by the obliquely flying insect, is the unit vector of the three axes of the body coordinate system of the obliquely flying insect, is the angle between the electric field direction of the incident wave and the X-axis of the antenna polarization coordinate system, , , are the components of the angle on the three axes of the antenna polarization coordinate system; Assume that the electromagnetic wave emission and reception directions of the monostatic radar are along the +z axis of the antenna polarization coordinate system and the -z axis of the antenna polarization coordinate system respectively, then there are:

[0020] Wherein, is the unit vector of the three axes of the antenna polarization coordinate system; Meanwhile, the direction vector of the scatterer is as follows:

[0021] Meanwhile, the scattering amplitude , the scattering amplitude and , , are related as follows:

[0022]

[0023] By solving the above equations simultaneously, the joint expressions of the three-dimensional attitude angles and , the scattering amplitude along the body axis direction of the prolate ellipsoid insect and the scattering amplitude perpendicular to the body axis direction are as follows:

[0024] Construct the polarization scattering matrix in the oblique flight attitude according to the combined expression .

[0025] Furthermore, the Euler transformation relationship between the three-axis unit vectors of the oblique flying insect body coordinate system and the three-axis unit vectors of the antenna polarization coordinate system is as follows: .

[0026] Furthermore, the calculation method of the components of the included angle , , on the three axes of the antenna polarization coordinate system is as follows:

[0027]

[0028]

[0029] where the volume of the prolate spheroid insect, is the major semi-axis of the prolate spheroid insect, is the minor semi-axis of the prolate spheroid insect, is the complex relative permittivity of the prolate spheroid insect, is the source position inside the prolate spheroid insect, , , are the shape factors corresponding to the components , , respectively, and the shape factors , , satisfy , and at the same time, the calculation method of the shape factors , , is as follows:

[0030] where represents an intermediate variable.

[0031] Furthermore, the method for obtaining the general expressions of the components of the polarization scattering matrix in the oblique flight attitude according to the field amplitude received by the antenna is: Construct the calculation formula for the field amplitude received by the antenna as follows:

[0032] Among them, the volume of the prolate ellipsoid insect , is the major semi - axis of the prolate ellipsoid insect, is the minor semi - axis of the prolate ellipsoid insect, is the complex relative permittivity of the prolate ellipsoid insect, is the source position inside the prolate ellipsoid insect, , , are the shape factors corresponding to the components , , respectively; is the angle between the direction of the incident wave electric field and the axis of the body coordinate system of the obliquely flying insect, is the incident wave electric field; , , , , , are all coefficients related to the major semi - axis and minor semi - axis of the prolate ellipsoid insect, and there are

[0033]

[0034]

[0035]

[0036]

[0037]

[0038] Among them, is the proportionality coefficient to ensure that the unit direction vector of the minor semi - axis is a unit vector, is the angle between the projection of the unit direction vector of the minor semi - axis in the plane of the antenna polarization coordinate system and the axis, is the angle between the major semi - axis and the axis of the antenna polarization coordinate system, is the angle between the direction of the incident wave electric field and the axis of the antenna polarization coordinate system; Based on the calculation formula of the field amplitude received by the antenna, the polarization scattering matrix for the oblique - flying attitude is constructed as follows:

[0039] Among them, , , , are the four components of the polarization scattering matrix in the oblique flight attitude, and is the phase factor related to the component , and there are:

[0040]

[0041] Among them, is the phase factor related to the component ;

[0042] Among them, is the phase factor related to the component ;

[0043] Among them, is the phase factor related to the component ; According to the mapping relationship between the electric and magnetic fields of the scattered wave, the electric and magnetic fields of the incident wave, and the components , , the four , , , are written in matrix form:

[0044] Among them,

[0045] The electric and magnetic fields of the scattered wave are:

[0046] The electric and magnetic fields of the incident wave are:

[0047] Based on the polarization scattering matrix in the oblique flight attitude in matrix form , the general expressions of the components of the polarization scattering matrix in the oblique flight attitude are obtained.

[0048] Further, in step S4, the polarization-averaged RCS parameter method or the polarization invariant parameter method is used to invert the scattering matrix in the level flight attitude to obtain the body size parameters of the obliquely flying insect.

[0049] Further, an estimation system for the body size parameters of an obliquely flying insect based on scattering matrix recovery includes an attitude angle acquisition module, an obliquely flying attitude polarization scattering matrix acquisition module, a level flight attitude polarization scattering matrix acquisition module, and a body size parameter estimation module; The attitude angle acquisition module obtains the three-dimensional attitude angles of the body axis of the obliquely flying insect relative to the antenna polarization coordinate system based on the projection relationship between the body axis of the obliquely flying insect and the antenna polarization plane and , where is the angle between the projection of the body axis of the obliquely flying insect on the antenna polarization plane and the H polarization direction of the electromagnetic wave, is the angle between the body axis of the obliquely flying insect and the antenna polarization plane; The obliquely flying attitude polarization scattering matrix acquisition module equivalentizes the obliquely flying insect to an oblate spheroid and constructs the obliquely flying attitude polarization scattering matrix of the oblate spheroid insect according to Rayleigh scattering, where each component of the obliquely flying attitude polarization scattering matrix is the three-dimensional attitude angles and , the scattering amplitude along the body axis direction of the oblate spheroid insect, and the scattering amplitude perpendicular to the body axis direction; The level flight attitude polarization scattering matrix acquisition module calculates the scattering amplitude and the scattering amplitude based on the obliquely flying attitude polarization scattering matrix, thereby reconstructing the level flight attitude polarization scattering matrix of the oblate spheroid insect; The body size parameter estimation module inversely obtains the body size parameters of the obliquely flying insect based on the level flight attitude polarization scattering matrix.

[0050] Beneficial effects: The present invention provides an estimation method for the body size parameters of an obliquely flying insect based on scattering matrix recovery. First, the three-dimensional attitude angles and of the insect body axis relative to the radar antenna coordinate system are calculated; then, according to the obtained three-dimensional attitude angles and , the scattering matrix measured by the insect at this angle is restored to the traditional level flight attitude scattering matrix; finally, the body size parameters of the insect can be estimated based on the body size parameter inversion method of the traditional level flight attitude insect; therefore, the present invention can be used for the radar to measure the body size parameters of insects in any flight attitude, and for the first time, a huge breakthrough has been achieved in the estimation of insect body size parameters from the traditional fixed attitude observation to any attitude observation. Description of the Drawings

[0051] Figure 1 Flow chart of a method for estimating the body size parameters of obliquely flying insects based on scattering matrix recovery provided by the present invention; Figure 2 Schematic diagram of the relative attitude between an insect and the antenna polarization plane provided by the present invention; Figure 3 Schematic diagram of radar full-polarization observation provided by the present invention; Figure 4 Flat flight matrix of a certain Spodoptera frugiperda provided by the present invention Recovery result (9.4 GHz, average error 0.44 dB); Figure 5 Flat flight matrix of a certain Spodoptera frugiperda provided by the present invention Recovery result (9.4 GHz, average error 0.93 dB). Detailed implementation manners

[0052] In order to enable those skilled in the art to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application.

[0053] As Figure 1 shown, a method for estimating the body size parameters of obliquely flying insects based on scattering matrix recovery includes the following steps: S1: Based on the projection relationship between the body axis of an obliquely flying insect and the antenna polarization plane, obtain the three-dimensional attitude angles and of the body axis of the obliquely flying insect relative to the antenna polarization coordinate system, where is the angle between the projection of the body axis of the obliquely flying insect on the antenna polarization plane and the H polarization direction of the electromagnetic wave, and is the angle between the body axis of the obliquely flying insect and the antenna polarization plane; It should be noted that step S1 is intended to calculate the insect attitude angle. Specifically, the insect attitude angle is the rotation angle of the insect body axis relative to the antenna polarization plane reference coordinate system . As Figure 2 shown. Among them, the azimuth angle of the insect attitude is defined as the angle between the projection of the insect body axis on the polarization plane (i.e., the plane formed by the H and V polarization vectors, the plane perpendicular to the antenna line-of-sight direction) and the H polarization direction; the pitch angle is defined as the angle between the body axis and its projection on the polarization plane. Therefore, the rotation matrix of the insect body axis relative to the polarization plane reference system can be defined as: (1) where , They are respectively the rotation matrices for rotating by angle about the axis and rotating by angle about the new axis.

[0054] Using the above rotation matrices, the true attitude angles of the insect body axis in the reference coordinate system of the antenna polarization plane can be calculated. Assuming that the initial body axis direction of the insect is along the positive direction of the X-axis , through the matrix rotation, the new direction of the insect body axis can be obtained. .

[0055] Therefore, the azimuth angle of the insect relative to the H polarization direction is calculated by the formula: (2) The elevation angle relative to the polarization plane is calculated by the formula: (3) where , , are respectively the components of the new body axis direction vector of the insect on the , , axes.

[0056] S2: Equivalent the obliquely flying insect to an oblate spheroid, and construct the polarization scattering matrix of the obliquely flying attitude of the oblate spheroid insect according to Rayleigh scattering, where each component of the polarization scattering matrix of the obliquely flying attitude is a joint expression of the three-dimensional attitude angles and , the scattering amplitude along the body axis direction of the oblate spheroid insect and the scattering amplitude perpendicular to the body axis direction; It should be noted that step S2 aims to perform Rayleigh scattering modeling of the oblate spheroid; specifically, in order to facilitate the qualitative analysis of the electromagnetic scattering characteristics of the insect, it is a reasonable and ideal choice to equivalent the body of the insect to an oblate spheroid. Assume that a linearly polarized plane wave propagates in a medium with a dielectric constant of and a magnetic permeability of , is the wavelength of the wave in this medium, its electric field strength is , is the unit vector in the propagation direction of the incident wave, is the unit vector in the polarization direction of the wave. This wave is incident on a target, and in the propagation of the reflected wave at a distance from the target in the direction of the scattered field in the far field can be expressed as: (4) where is the wavenumber in the medium, is called the scattering amplitude and is written as: (5) The above is the exact expression for representing the scattering amplitude using the total internal electric field of the target where is the complex relative permittivity of the target, given by Equation (6), is the source position inside the target.

[0057] (6) Insect radars are usually monostatic, so , and thus the backscattering radar cross-section and are related as: (7) In the present invention, the insect is modeled as a prolate ellipsoid with major semi-axis a and minor semi-axes b = c, and its surface equation is: (8) And the components of the incident wave electric field in the three-axis directions of the antenna polarization plane reference coordinate system are respectively , and . The components of the electric field component inside the Rayleigh scattering target on each coordinate axis are given by the following equations: (9) where: (10) , , are factors depending on the shape of the scatterer, is the integration variable. It is known that the shape factors satisfy the following equation: (11) For a prolate ellipsoid , there are: (12) Therefore, once the ellipsoidal target shape factor and dielectric constant are known, the scattering amplitude of the Rayleigh scatterer can be calculated. Modeling the insect as a prolate ellipsoid and considering the radar observation of an insect in an arbitrary posture, as Figure 3 shown. The radar polarization plane is plane, and the angle between the direction of the electric field vector and the axis is , so the incident field can be written as: (13) The center of the ellipsoid is located at the beam center, and the semi-axis lengths are , and the corresponding unit vectors are , respectively, and satisfy the right-hand rule. The major axis (red solid line) makes an angle of with the axis, and the projection of the major axis in the plane (red dashed line) makes an angle of with the axis. The unit direction vector of the minor axis makes an angle of with the projection in the axis and . From the geometric relationship, can be expressed as: (14) where , , are the unit vectors of the axis of the antenna polarization plane reference coordinate system, respectively, and and are the proportionality coefficients to ensure that , are unit vectors. Decompose the incident field in the rectangular coordinate system composed of the three axes of the ellipsoid to obtain its components along different axes of the ellipsoid, and are written as: (15)

[0058] (16) (17)

[0059] According to Equation (9), the built-in electric field can be written as the vector superposition of the component of the incident field along the major axis of the ellipsoid and the component perpendicular to the major axis of the ellipsoid, each multiplied by different coefficients: (18) Wherein is the unit direction vector of the built-in electric field, is the amplitude of the built-in electric field. It can be easily seen that is in direct proportion to : (19) Substituting Eqs. (18) and (19) into Eq. (5), we can obtain: (20) Wherein . From Eq. (4), we can write the scattered field as: (21) The radar receiving polarization plane is plane, and the included angle between the direction of the electric field vector and axis is . Thus, the unit direction vector of the received field can be written as: (22) Then the amplitude of the field received by the antenna can be written as: (23) At this time, based on we can obtain the target scattering matrix S as: (24) Wherein is the phase factor. Let , then the elements of matrix S are expressed as: (25) (26) (27) (28) From Figure 2 it can be seen that the angles and determine the attitude of the ellipsoid relative to the antenna polarization coordinate system. Assume that the incident plane wave is along direction. Introduce a coordinate system, called the body coordinate reference system, which is obtained by rotating the antenna polarization coordinate system by three Euler angles , and . First, rotate by an angle of around the axis to obtain The system. Then, rotate around axis by angle to obtain the system. Finally, rotate around axis by angle to obtain the system. When the target is in the case where the axis of symmetry is on the axis, the third angle ( ) can be set to zero, and the "main" reference frame is determined by the angles and . The unit vector of the body reference frame is related to the unit vector of the antenna polarization coordinate system by an Euler transformation as shown in the following equation: (29) Writing equations (25) - (28) in matrix form, they can be uniformly expressed as: (30) where:

[0060] (31) is the projection matrix of the scattered wave field: (32) is the projection matrix of the incident wave field: (33) where , are the electromagnetic and magnetic field directions of the incident wave, , are the electromagnetic and magnetic field directions of the scattered wave.

[0061] At this time, the components of the scattering matrix, that is, the general expressions of equations (25) - (28) can be written as: (34) S3: Calculate the scattering amplitude and the scattering amplitude from the polarization scattering matrix in the oblique flight attitude, so as to reconstruct the polarization scattering matrix of the prolate ellipsoid insect in the level flight attitude; It should be noted that step S3 aims to derive the general expression of the polarization scattering matrix of insects in the oblique flight attitude. Specifically, for prolate ellipsoid insects, there are: , . Assuming that the electromagnetic wave emission and reception directions of a monostatic radar are along the +z axis and -z axis respectively, then there are: (35) Obtain the direction vector of the scatterer from Equation (29): (36) By applying Equations (35) and (36) to Equation (34), the scattering amplitude components are obtained as follows: (37) where and are the scattering components of the prolate spheroid insect along the body axis and perpendicular to the body axis direction, respectively, and can be expressed as: (38) (39) In the case of a monostatic radar, the backscatter alignment (BSA) convention is usually used. Therefore, the backscatter matrix of the prolate spheroid is: (40) From this, the general expression of the polarization scattering matrix of the prolate spheroid insect can be obtained with respect to the attitude angles and in the radar antenna coordinate system.

[0062]

[0063] (41) The scattering matrix of the insect in the level flight attitude when the radar beam is vertically upward and the insect body axis is parallel to the antenna H polarization direction can be expressed as: (42) Therefore, to realize the reconstruction of the scattering matrix of the insect in the platform attitude, that is, it is necessary to solve the scattering amplitudes and of the prolate spheroid insect along the body axis and perpendicular to the body weight direction. According to Equations (37) and (40), the relationships between the four components of the scattering matrix of the obliquely flying insect and and can be established as: (43) Denote the coefficient matrix as 𝐴 and the measured scattering component vector as 𝑏. Therefore, we have: (44) where .

[0064] From this, the scattering amplitudes and , thus reconstructing the scattering matrix of the horizontally flying insect.

[0065] S4: Invert the body size parameters of the obliquely flying insect based on the horizontally flying attitude polarization scattering matrix.

[0066] Finally, based on the restored horizontally flying attitude scattering matrix , the traditional algorithms for estimating insect radar body size parameters (such as the polarization-averaged RCS parameter , the polarization invariant parameter , etc., fitting formulas) can be used to estimate the body size parameters of the insect.

[0067] Based on the measured data of 33 insects in the microwave anechoic chamber, the performance of reconstructing the horizontally flying attitude matrix of the present invention at different antenna observation perspectives at the 9.4 GHz frequency of the traditional insect radar was analyzed. Among them, the antenna observations included 4 azimuth angles (0° / 30° / 60° / 90°) and 5 elevation angles (0° / 5° / 15° / 30° / 45°), a total of 20 combinations of observation perspectives. Taking a certain Spodoptera frugiperda (weight 137.35 mg, body length 16 mm, body width 5 mm) as an example, Figure 4 and Figure 5 respectively show the restoration results of the horizontally flying matrix and . The abscissa represents the serial numbers of different observation perspectives; among them, the estimated average error is 0.44 dB, estimated average error is 0.93 dB. For all 33 insects, the and average absolute errors are less than 1 dB at different perspectives. Using the polarization-averaged RCS parameter to estimate the weight and body length parameters of the insect, the average relative errors are 18.9% and 17.3% respectively. To sum up, generally speaking, the algorithm proposed in the present invention can effectively restore the obliquely flying attitude scattering matrix to the horizontally flying attitude scattering matrix and can achieve high-precision estimation of insect body size parameters.

[0068] To sum up, the present invention discloses an algorithm for estimating the body size parameters of obliquely flying insects based on scattering matrix restoration. This invention can be used for estimating the body size parameters of non-horizontally flying insects and realizes the breakthrough from vertical observation to arbitrary attitude observation for insect body size parameter estimation for the first time. The present invention first calculates the three-dimensional attitude angles and of the insect body axis relative to the radar antenna coordinate system, and then according to the obtained three-dimensional attitude angles and , the scattering matrix measured for the insect at this angle is restored to the scattering matrix in the traditional level flight attitude; finally, the body size parameters of the insect can be estimated based on the body size parameter inversion method for insects in the traditional level flight attitude; based on the measured multi-view data of 33 insects in the microwave anechoic chamber, the effectiveness of the proposed method is verified.

[0069] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can certainly make various corresponding changes and deformations according to the present invention. However, these corresponding changes and deformations should all fall within the protection scope of the appended claims of the present invention.

Claims

1. A method for estimating body shape parameters of obliquely flying insects based on scattering matrix recovery, characterized in that: The following steps are involved: S1: Based on the projection relationship between the body axis of the oblique-flying insect and the polarization plane of the antenna, the three-dimensional attitude angle of the body axis of the oblique-flying insect relative to the antenna polarization coordinate system is obtained. and ,in, is the angle between the projection of the body axis of the oblique-flying insect on the polarization plane of the antenna and the H polarization direction of the electromagnetic wave, is the angle between the body axis of the oblique-flying insect and the polarization plane of the antenna; S2: The oblique-flying insects are equivalent to prolate ellipsoids, and the oblique-flight attitude polarization scattering matrix of the prolate ellipsoid insects is constructed based on Rayleigh scattering. The components of the oblique-flight attitude polarization scattering matrix are three-dimensional attitude angles. and , the scattering amplitude along the body axis of the ellipsoidal insect and the scattering amplitude perpendicular to the body axis The joint expression of S3: Calculate the scattering amplitude based on the polarization scattering matrix of the oblique flight attitude and scattering amplitude , thus reconstructing the polarization scattering matrix of the horizontal flight posture of the ellipsoidal insect ; S4: The body parameters of oblique-flying insects are obtained by inverting the polarization scattering matrix of the level-flight posture.

2. The method for estimating body shape parameters of oblique flying insects based on scattering matrix recovery according to claim 1, characterized in that: In step S1, the three-dimensional attitude angle of the body axis of the oblique flying insect relative to the antenna polarization coordinate system is and The method to obtain is: Get the rotation matrix of the antenna polarization coordinate system of the insect body axis relative to the polarization plane as follows: Assuming that the insect's initial body axis is The positive direction along the X-axis of the antenna polarization coordinate system , through the rotation matrix Rotate, and you get the new direction of the insect's body axis ; Based on the new direction of insect body axis Get the angle as follows: Based on the new direction of insect body axis Get the angle as follows: in, , , The new direction of insect body axis Components on the X, Y, and Z axes of the antenna polarization coordinate system.

3. The method for estimating body shape parameters of oblique flying insects based on scattering matrix recovery according to claim 1, characterized in that: The polarization scattering matrix of the oblique flight attitude in step S2 for: in, is the polarization scattering matrix of the oblique flight attitude In the polarization channel hh The weight, is the polarization scattering matrix of the oblique flight attitude In the polarization channel hv The weight, is the polarization scattering matrix of the oblique flight attitude In the polarization channel v The weight, is the polarization scattering matrix of the oblique flight attitude In the polarization channel vv of weight, and has: in, is the scattering amplitude of the prolate ellipsoid insect along the body axis, is the scattering amplitude of the prolate ellipsoid insect perpendicular to the body axis.

4. The method for estimating body shape parameters of oblique flying insects based on scattering matrix recovery according to claim 3, characterized in that: In step S3, the scattering amplitude and scattering amplitude The solution method is: Constructing the polarization scattering matrix of the horizontal flight posture when the insect body axis is parallel to the H polarization direction of the antenna as follows: Among them, the scattering amplitude , is the 3D attitude angle and The unknowns involved; Constructing the polarization scattering matrix of oblique flight attitude The four components , , , and , The mapping relationship is as follows: Based on the mapping relationship, the inverse operation of the matrix is ​​performed to solve the scattered component. , , reconstruct the polarization scattering matrix of the level flight attitude .

5. The method for estimating body shape parameters of oblique flying insects based on scattering matrix recovery as claimed in claim 3, characterized in that: Polarization scattering matrix of oblique flight attitude The method to obtain is: According to the field amplitude received by the antenna Get the polarization scattering matrix of the oblique flight attitude The general expressions for the components are as follows: in, is the dielectric constant of the environment where the oblique flying insects are located, is the wave number in the medium, , are the electric field direction and magnetic field direction of the incident wave incident on the oblique flying insect, , are the electric field direction and magnetic field direction of the scattered wave scattered by the oblique flying insect, is the three-axis unit vector of the oblique flying insect's body coordinate system, is the angle between the electric field direction of the incident wave and the X-axis of the antenna polarization coordinate system, , , Angle Components on the three axes of the antenna polarization coordinate system; Assuming that the electromagnetic wave transmission and reception directions of the single-station radar are along the +z axis and -z axis of the antenna polarization coordinate system, respectively, we have: in, is the three-axis unit vector of the antenna polarization coordinate system; At the same time, the direction vector of the scatterer is as follows: At the same time, the scattering amplitude , scattering amplitude and , , The relationship is as follows: Combining the above equations, we get the three-dimensional attitude angle and , the scattering amplitude along the body axis of the ellipsoidal insect and the scattering amplitude perpendicular to the body axis The joint expression is as follows: The polarization scattering matrix of the oblique flight attitude is constructed according to the joint expression .

6. The method for estimating body shape parameters of oblique flying insects based on scattering matrix recovery according to claim 5, characterized in that: Three-axis unit vectors of the coordinate system of the oblique flying insect The three-axis unit vector of the antenna polarization coordinate system The Euler transformation relationship between them is as follows: 。 7. The method for estimating body parameters of oblique-flying insects based on scattering matrix recovery according to claim 5, characterized in that: Angle Components on the three axes of the antenna polarization coordinate system , , The calculation method is as follows: Among them, the volume of the ellipsoid insect , is the long semi-axis of the prolate ellipsoid insect, is the short semi-axis of the prolate ellipsoid insect, is the complex relative permittivity of the prolate ellipsoid insect, is the source position inside the prolate ellipsoid insect, , , Respectively , , The corresponding shape factor, and the shape factor , , satisfy , while the form factor , , The calculation method is as follows: in, Represents an intermediate variable.

8. The method for estimating body parameters of oblique flying insects based on scattering matrix recovery according to claim 5, characterized in that: According to the field amplitude received by the antenna Get the polarization scattering matrix of the oblique flight attitude The general expression method for each component is: Construct the field amplitude received by the antenna The calculation formula is as follows: Among them, the volume of the ellipsoid insect , is the long semi-axis of the prolate ellipsoid insect, is the short semi-axis of the prolate ellipsoid insect, is the complex relative permittivity of the prolate ellipsoid insect, is the source position inside the prolate ellipsoid insect, , , Respectively , , The corresponding form factor; is the direction of the electric field of the incident wave and the coordinate system of the oblique flying insect The angle of the axis, is the electric field of the incident wave; , , , , , are coefficients related to the major and minor axes of the prolate ellipsoid insects, and in, To ensure that the minor semi-axis unit direction vector is the scale factor of the unit vector, is the unit direction vector of the minor semiaxis In the antenna polarization coordinate system Projection in the plane and Axis angle, is the semi-major axis and the antenna polarization coordinate system The angle of the axis, is the electric field direction of the incident wave and the antenna polarization coordinate system The angle of the axis; Based on the field amplitude received by the antenna The calculation formula for constructing the oblique flight attitude polarization scattering matrix as follows: in, , , , is the polarization scattering matrix of the oblique flight attitude The four components of For and weight The phase factor is: in, For and weight The phase factor involved; in, For and weight The phase factor involved; in, For and weight The phase factor involved; According to the electric and magnetic fields of the scattered wave, the electric and magnetic fields of the incident wave, and the components , , The mapping relationship between the four , , , Written in matrix form: in, Electric and magnetic fields of scattered waves for: Electric and magnetic fields of the incident wave for: Polarization scattering matrix based on oblique flight attitude in matrix form , and obtain the polarization scattering matrix of the oblique flight attitude General expressions for the components.

9. The method for estimating body parameters of oblique-flying insects based on scattering matrix recovery according to claim 1, characterized in that: In step S4, the polarization average RCS parameter method or the polarization invariant parameter method is used to invert the scattering matrix of the level flight posture to obtain the body parameters of the oblique flight insect.

10. A system for estimating body parameters of obliquely flying insects based on scattering matrix recovery, characterized in that: It includes an attitude angle acquisition module, an oblique flight attitude polarization scattering matrix acquisition module, a level flight attitude polarization scattering matrix acquisition module, and a body parameter estimation module; The attitude angle acquisition module acquires the three-dimensional attitude angle of the oblique flying insect body axis relative to the antenna polarization coordinate system based on the projection relationship between the oblique flying insect body axis and the antenna polarization plane. and ,in, is the angle between the projection of the body axis of the oblique-flying insect on the polarization plane of the antenna and the H polarization direction of the electromagnetic wave, is the angle between the body axis of the oblique-flying insect and the polarization plane of the antenna; The oblique flight attitude polarization scattering matrix acquisition module treats the oblique flight insect as a prolate ellipsoid, and constructs the oblique flight attitude polarization scattering matrix of the prolate ellipsoid insect based on Rayleigh scattering, wherein each component of the oblique flight attitude polarization scattering matrix is ​​a three-dimensional attitude angle and , the scattering amplitude along the body axis of the ellipsoidal insect and the scattering amplitude perpendicular to the body axis The joint expression of The level flight attitude polarization scattering matrix acquisition module calculates the scattering amplitude based on the oblique flight attitude polarization scattering matrix and scattering amplitude , thus reconstructing the polarization scattering matrix of the horizontal flight posture of the ellipsoidal insect ; The body parameter estimation module obtains the body parameters of the oblique flying insect based on the polarization scattering matrix inversion of the level flying posture.

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