Full-polarization radar polarization basis non-orthogonal correction method and error angle acquisition method

Abstract

The invention discloses a full-polarization radar polarization basis non-orthogonal error model correction method and a non-orthogonal error angle acquisition method so as to realize high-precision measurement of a target scattering matrix. According to the correction method, a scattering matrix measurement model containing error parameters is established, an influence mechanism of polarization basis non-orthogonality on a scattering matrix is systematically analyzed, and error compensation is carried out on a target measurement scattering matrix. According to the error angle obtaining method, inversion of the error angle is completed through the metal wire. According to the method, the polarization basis non-orthogonality error caused by factors such as antenna installation deviation can be effectively eliminated, the scattering matrix measurement precision and the inversion accuracy of target parameters are remarkably improved, and a reliable polarization basis correction solution is provided for a complete polarization radar system.

Description

Technical Field

[0001] This invention belongs to the field of precision measurement and calibration, specifically relating to a method for correcting a non-orthogonal error model of a fully polarized radar polarization base and a method for obtaining the error angle. Background Technology

[0002] Migration is a unique behavior of insects seeking to escape unfavorable environments and expand their spatial and temporal resources. It is also a significant cause of insect outbreaks in different locations, posing a serious threat to national food security. Radar is the most effective means of monitoring insect migration around the clock. Its core function is to measure insect body size parameters and identify species, providing crucial information for precise pest control. Current high-resolution, fully polarized insect radars employ frequency-modulated stepped-frequency waveforms to achieve high range resolution and utilize a fully polarized system to acquire target polarization information, resulting in higher reliability and information acquisition efficiency.

[0003] A fully polarimetric radar can obtain a scattering matrix containing the target's current viewing angle within a single frequency frame period. The scattering matrix comprehensively characterizes the polarization scattering properties of the target's interaction with electromagnetic waves under different polarization combinations, thereby revealing parameters such as the target's axis, weight, and length. Theoretically, all polarization information of the target can be obtained from the scattering matrix.

[0004] The accuracy of polarization data depends on the overall performance of the radar system. However, issues such as antenna installation deviations can cause non-orthogonality of the polarization bases. When the vertical polarization base system has a rotation angle deviation as its sole error, while the horizontal polarization base remains ideal, the orthogonality of the polarization bases will be disrupted, leading to energy coupling between channels of the scattering matrix. This error severely affects the accuracy of the full polarization measurement data, interfering with the correct inversion of target characteristic parameters and the accuracy of insect population classification. Therefore, it is necessary to obtain the error angle under this condition and calibrate the scattering matrix accordingly. Summary of the Invention

[0005] In view of this, the present invention provides a non-orthogonal correction method for a fully polarized radar polarization basis and a method for obtaining error angles. The specific solution includes a correction method for a non-orthogonal error model of the polarization basis and a method for obtaining error angles based on the non-orthogonal polarization basis.

[0006] The non-orthogonal correction method for the polarization base of a fully polarimetric radar establishes a mathematical model to systematically analyze the influence mechanism of the non-orthogonal rotation deviation of the polarization base on each component of the fully polarimetric scattering matrix. Based on the known error angle, a method for reconstructing the true value from the measured scattering matrix is ​​proposed. The error angle acquisition method based on the non-orthogonal polarization base is based on the mathematical model established in the correction method, selecting a metal wire as the calibration target. First, the azimuth is determined by rotating the metal wire, obtaining the metal wire scattering matrix measurement model at the current angle. Then, it is compared with the scattering matrix model under error-free conditions, and the polarization base deviation angle is determined by the ratio of the two channels.

[0007] The technical solution of this invention is as follows: A non-orthogonal correction method for the polarization base of a fully polarimetric radar and a method for obtaining the error angle, comprising: The steps for correcting the polarization-based nonorthogonal error model are as follows: Step 1: Construction of the fully polarimetric radar scattering matrix model. Under the ideal orthogonal polarization basis, a complete scattering matrix including HH, HV, VH, and VV channels is established to characterize the scattering characteristics of the target under different polarization states, providing a theoretical basis for subsequent error analysis and correction.

[0008] Step 2: Constructing a non-orthogonal error model for the polarization base of the fully polarized radar. This step describes the non-orthogonal rotational deviation of the polarization base in the actual system using a mathematical model, analyzes the coupling influence mechanism of this deviation on each scattering matrix component, and clarifies the quantitative relationship between the error angle and the measurement results.

[0009] Step 3: Based on the scattering matrix correction formula of the non-orthogonal error of the polarization base, and using the error angle as a parameter, establish a mathematical expression for inverting the true scattering matrix from the measured scattering matrix, realize the compensation of the coupling error between channels, and complete the systematic correction of the non-orthogonal polarization base.

[0010] The steps for obtaining the error angle based on non-orthogonal polarization basis are as follows: Step 1: Constructing the scattering matrix model of the metal wire under non-orthogonal polarization basis, and deriving the theoretical expression of the scattering matrix of the metal wire under non-orthogonal polarization basis. This model will include the non-orthogonal deflection angle parameter of the polarization basis to be solved.

[0011] Step 2: Determine the 0° position of the metal wire. By rotating the metal wire and observing the scattering response of its same polarization channel, the physical placement angle corresponding to the theoretical maximum value of the response is defined as the 0° reference azimuth where the metal wire is parallel to the radar line of sight.

[0012] Step 3: Obtain the polarization base deflection angle. At 0° azimuth, compare the measured value of the metal wire scattering matrix with the theoretical model to solve for the non-orthogonal deviation angle of the polarization base.

[0013] Beneficial effects: 1. Revealing the generation mechanism and influence law of polarization basis non-orthogonality error: In order to address the problem of polarization basis non-orthogonality error caused by the angle deviation of a single antenna in a fully polarized radar system, a scattering matrix measurement model including error parameters was established, and the influence mechanism of this error on the target scattering matrix was systematically analyzed. 2. A method for directly obtaining the polarization basis deviation angle based on metal wire calibration is proposed: By constructing the mathematical relationship between the theoretical scattering matrix and the measurement value containing errors, an error compensation algorithm based on polarization basis correction is proposed, and based on this, a method for obtaining the error angle based on metal wire calibration is proposed; 3. Improve the measurement accuracy and inversion reliability of fully polarimetric radar systems: This invention not only reveals the influence law of polarimetric basis nonorthogonality error, providing a theoretical basis for error correction and accurate measurement of fully polarimetric radar systems, but also provides an error compensation solution with engineering application value for fully polarimetric radar systems, thereby improving the accuracy of insect target parameter inversion. Attached Figure Description

[0014] Figure 1 Example diagram of non-orthogonal polarization bases; Figure 2 A schematic diagram comparing the error between the measured and true values ​​of the uncorrected scattering matrix; Figure 3 A schematic diagram comparing the error between the measured and true values ​​of the scattering matrix after correction; Figure 4 Flowchart of the method. Detailed Implementation

[0015] This invention is a method for non-orthogonal correction of polarization base in fully polarized radar and a method for obtaining error angle. The idea is to establish a mathematical model to analyze the influence mechanism of non-orthogonal rotation deviation of polarization base on each component of the scattering matrix, deduce the true value based on the measured value of the scattering matrix, and obtain the non-orthogonal deflection angle of polarization base through a metal wire based on this model.

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0018] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0019] The technical solution of this invention includes a correction method for a non-orthogonal error model based on a polarization basis and a method for obtaining the error angle based on a non-orthogonal polarization basis. The implementation methods of the non-orthogonal correction method and the error angle acquisition method for a fully polarized radar polarization basis in this invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0020] Correction methods for polarization-based nonorthogonal error models: Step 1: Construction of the full polarization radar scattering matrix model. First, a complete scattering matrix containing HH, HV, VH, and VV channels is established under an ideal orthogonal polarization basis to characterize the scattering characteristics of the target under different polarization states.

[0021] Fully polarimetric insect radar can directly measure the scattering matrix of insects by simultaneously or alternately transmitting and receiving H and V polarizations. The scattering matrix of a target can be expressed as: (1.1) Where H represents horizontal polarization and V represents vertical polarization; the first letter of each element indicates the polarization of the receiving antenna, and the second letter indicates the polarization of the transmitting antenna; taking HV as an example, it represents a signal transmitted with V polarization and received with H polarization, representing the target's ability to convert a V-polarized incident signal into an H-polarized signal and scatter it back. Therefore, the four elements S in the above formula... HH S HV S VH S VV This represents the backscattering components of incident signals reflected from different channels to different channels by the target.

[0022] Let the polarization direction of antenna H be... The polarization direction of the V antenna is ,use This represents the polarization state vector of the H antenna. Let V represent the polarization state vector of the antenna. From this, we can obtain the target's scattering matrix: (1.2) (1.3) (1.4) (1.5) The scattering characteristics of a target under different polarization states can be characterized by the above formula. Under normal circumstances, taking the H polarization direction as the reference, then... =0, V antenna is perpendicular to H antenna, then =90, at which point the target scattering matrix remains unchanged.

[0023] Step 2: Constructing a non-orthogonal error model for the polarization base of the fully polarized radar. This step describes the non-orthogonal rotational deviation of the polarization base in the actual system using a mathematical model, analyzes the coupling influence mechanism of this deviation on each scattering matrix component, and clarifies the quantitative relationship between the error angle and the measurement results.

[0024] Assume that the H antenna and the V antenna are not orthogonal and have a certain angular deviation ∆ The schematic diagram is shown in the attached figure. Figure 1 As shown. At this point, the polarization direction of antenna V will change, and the scattering matrix will become: (1.6) (1.7) (1.8) (1.9) At this point, the correspondence between the measured value of the scattering matrix and the true value of the scattering matrix is ​​established when the radar system has a non-orthogonal angle deviation of the polarization base.

[0025] Step 3: Obtain the scattering matrix correction formula based on the non-orthogonal error of the polarization base. Using the error angle as a parameter, and based on the mathematical expression of the scattering matrix under the non-orthogonal polarization base established in Step 2, realize the compensation of the coupling error between channels and complete the systematic correction of the non-orthogonal polarization base.

[0026] Assuming the error angle has been obtained, the true value of the scattering matrix when there is no angle error can be directly obtained from the measured value of the error matrix in the above formula: (1.10) (1.11) (1.12) (1.13) Error angle acquisition method based on non-orthogonal polarization basis: Step 1: Constructing the scattering matrix model of the metal wire under non-orthogonal polarization basis. Based on the above steps for constructing the non-orthogonal error model of the fully polarized radar polarization basis, derive the theoretical expression of the scattering matrix of the metal wire under non-orthogonal polarization basis. This model will include the non-orthogonal deflection angle parameter of the polarization basis to be solved.

[0027] When using a metal wire for calibration, the scattering matrix of the metal wire can be represented as follows: Formulas Section (Next Section) (2.1) in This represents the scattering matrix of the metal wire when it is at 0° relative to the H-polarized antenna.

[0028] When the metal wire is at a certain angle relative to the H-polarized antenna When the scattering matrix is ​​transformed, it becomes: (2.2) The superscript T indicates matrix transpose. The rotation matrix can be represented as: (2.3) Therefore, the elements of the scattering matrix of the wire target with a roll angle are given by the following formula: (2.4) (2.5) (2.6) (2.7) in The four terms indicate that the metal wire has a certain angle relative to the H-polarized antenna. When, the element values ​​of the four channels HH, HV, VH, and VV in the scattering matrix.

[0029] Based on the above analysis, when there is a non-orthogonal angle error in the polarization basis, substituting the equation into the equation yields the measured scattering matrix value under the non-orthogonal angle error condition: (2.8) (2.9) (2.10) (2.11) Step 2: Determine the 0° position of the metal wire. By rotating the metal wire and observing the scattering response of its same polarization channel, the physical placement angle corresponding to the theoretical maximum value of the response is defined as the 0° reference azimuth where the metal wire is parallel to the radar line of sight.

[0030] Since the measured values ​​of the metal wire scattering matrix are related to the current angle of the metal wire, it is necessary to first find the location of 0° to eliminate the possibility of obtaining ∆. During the process, current angle Interference with parameters.

[0031] Since the HH channel is theoretically unaffected by non-orthogonal angle errors, it can be selected as a reference. By rotating the metal wire 360° and observing the amplitude of the HH channel, when its amplitude reaches its maximum value, it can be considered that at this point... Wire angle Then, we can substitute these values ​​into the equation to obtain the HH and HV components of the scattering matrix: (2.12) (2.13) The polarization base deflection angle ∆ can then be obtained from these two items. .

[0032] Step 3: Obtain the polarization base deflection angle. At 0° azimuth, compare the measured value of the metal wire scattering matrix with the theoretical model to solve for the non-orthogonal deviation angle of the polarization base.

[0033] According to the formula in step two, the polarization base deflection angle can be obtained by comparing the ratio of the HH channel to the HV channel of the metal wire at this point: (2.14) The polarization base deflection angle ∆ can be determined using this formula. The angle.

[0034] The verification process includes generating measured values ​​of the scattering matrix with predetermined error parameters, applying the proposed correction algorithm for error compensation, and finally evaluating the accuracy by calculating the error index between the reconstructed scattering matrix and the true scattering matrix. Let the calibrated target scattering matrix be: (3.1) The relative amplitude error is defined as: (3.2) The parameter settings are as follows: 1) The original target scattering matrix is ​​expressed as:

[0035] 2) The true value of the body axis direction is: 3) The polarization base deflection angle is: This embodiment first transforms the original target scattering matrix (parameter 1) using the true value of the target body axis direction (parameter 2) to obtain the target scattering matrix under the set body axis direction. Then, different values ​​of the polarization basis deflection angle (parameter 3) are added to the target scattering matrix to obtain curves showing the error between the measured and true values ​​of each channel of the scattering matrix as a function of the polarization basis deflection angle. Finally, the scattering matrix is ​​corrected using the correction method proposed according to this invention, resulting in curves showing the error between the measured and true values ​​of each channel of the corrected scattering matrix as a function of the polarization basis deflection angle.

[0036] A comparison of the errors between the measured and true values ​​of the uncorrected scattering matrix is ​​attached. Figure 2 As shown.

[0037] A comparison of the errors between the corrected scattering matrix measurements and the true values ​​is shown in the appendix. Figure 3 As shown.

[0038] Experimental results show that, for the uncompensated scattering matrix, the common polarization channel (VV) maintains a low measurement error, closely approximating the theoretical true value. However, the measurement accuracy of the cross polarization channel (HV / VH) decreases significantly, with an error reaching -3 dB at an error angle of 5°.

[0039] Compared to the theoretical case, the corrected scattering matrix exhibits a significantly reduced error, with the numerical difference being negligible, ultimately validating the effectiveness of the correction method. Specifically, the HH channel, theoretically unaffected by non-orthogonal errors, displays an error value close to negative infinity (-inf) on a logarithmic scale and is therefore not shown in the figure. Similarly, the discontinuities observed in other channels stem from the same principle, where the logarithmic calculation approaches negative infinity when the error reaches zero. These results clearly demonstrate that the proposed correction algorithm can completely eliminate the systematic errors caused by polarization basis non-orthogonality, achieving high-precision reconstruction of the scattering matrix.

[0040] Therefore, this invention provides a non-orthogonal correction method for the polarization basis of a fully polarimetric radar and a method for obtaining the error angle, which is applicable to fully polarimetric radar. By using the experimental equipment and experimental procedures described in this invention, error correction and accurate measurement of the target scattering matrix of a fully polarimetric radar system can be achieved.

[0041] In summary, the above are merely embodiments of the present invention based on single-data examples and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A non-orthogonal correction method for the polarization base of a fully polarized radar and a method for obtaining the error angle, characterized in that... It includes a correction method for non-orthogonal error models based on polarization bases and a method for obtaining error angles based on non-orthogonal polarization bases.

2. The method for correcting non-orthogonal polarization-based errors in a fully polarized radar as described in claim 1, and the method for obtaining the error angle, comprising the following steps: Step 1: Constructing the fully polarimetric radar scattering matrix model; Step 2: Construction of the non-orthogonal error model based on polarization of the fully polarized radar; Step 3: Scattering matrix correction formula based on polarization basis non-orthogonal error.

3. The non-orthogonal correction method for fully polarized radar polarization bases and the error angle acquisition method as described in claim 1, wherein the error angle acquisition method based on non-orthogonal polarization bases is characterized in that... The error angle is obtained by determining the position of a rotating metal wire, thus achieving high-precision acquisition of the error angle of a non-orthogonal polarization base. The steps include the following: Step 1: Constructing the scattering matrix model of metal wires under non-orthogonal polarization bases; Step 2: Determine the 0° position of the metal wire; Step 3: Obtain the polarization base deflection angle.

4. The correction method for the non-orthogonal error model of polarization basis as described in claim 2, characterized in that... Step 2: Construction of the non-orthogonal error model based on the polarization basis of the fully polarized radar: Let the polarization direction of antenna H be... The polarization direction of the V antenna is The scattering matrix of the target is obtained as follows: (1.1)； (1.2)； (1.3)； (1.4)； Under normal circumstances, taking the H polarization direction as the reference, then =0, V antenna is perpendicular to H antenna, then =90, at which point the target scattering matrix remains unchanged; assuming the H antenna and V antenna are not orthogonal, and there is a certain angular deviation ∆ At this point, the polarization direction of antenna V will change, and the scattering matrix will become: (1.5)； (1.6)； (1.7)； (1.8)； At this point, the correspondence between the measured value of the scattering matrix and the true value of the scattering matrix is ​​established when the radar system has a non-orthogonal angle deviation of the polarization base.

5. The correction method for the polarization-based non-orthogonal error model as described in claim 2, characterized in that... Step 3: Scattering matrix correction formula based on polarization basis non-orthogonality error: Assuming the error angle has been obtained, the true value of the scattering matrix when there is no angle error can be directly obtained from the measured value of the error matrix in the above formula: (2.1)； (2.2)； (2.3)； (2.4)。 6. The error angle acquisition method based on non-orthogonal polarization basis as described in claim 3, characterized in that, Step 1: Construction of the metal wire scattering matrix model under non-orthogonal polarization basis: The elements of the scattering matrix of the wire target with a roll angle are: (3.1)； (3.2)； (3.3)； (3.4)； When non-orthogonal angle errors of the polarization basis exist, substituting the equations into the equations yields the measured scattering matrix value under the non-orthogonal angle error condition: (3.5)； (3.6)； (3.7)； (3.8)。 7. The error angle acquisition method based on non-orthogonal polarization basis as described in claim 3, characterized in that, In step two, determine the 0° position of the metal wire: Since the HH channel is theoretically unaffected by non-orthogonal angle errors, it is selected as a reference. By rotating the metal wire 360° and observing the amplitude of the HH channel, when its amplitude reaches its maximum value, it is considered that at this point... Wire angle .

8. The error angle acquisition method based on non-orthogonal polarization basis as described in claim 3, characterized in that, In step three, the polarization base deflection angle is obtained: When the angle is 0, the HH and HV components of the scattering matrix of the metal wire are: (4.1)； (4.2)； The polarization base deflection angle is obtained by the ratio of the HH channel to the HV channel of the metal wire at this time: (4.3)。

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