A passive polarization calibration body for full polarization measurement radar system calibration

Abstract

The present invention discloses a passive polarization calibration body for calibrating a full-polarization measurement radar system. When rotated in azimuth, its polarization scattering matrix at different azimuth angles includes non-depolarized scattering components similar to those of metal spheres, cylinders, and the like, and depolarized scattering components similar to those of right-angle dihedral reflectors. By using a single passive polarization calibration body and measuring its full-polarization scattering data at multiple azimuth rotation angles using a turntable imaging measurement radar, multiple polarization scattering matrix measurement values ​​required for full-polarization calibration of a general non-reciprocal radar system can be obtained, thereby achieving polarization calibration of the measurement radar system. Furthermore, since only a single calibration body needs to be measured using a turntable, measurement uncertainty caused by calibration body replacement during the measurement process is reduced. Furthermore, since no additional mechanical rotating devices such as stepping motors are required, the difficulty of angle alignment and the influence of interfering scattering components are reduced, thereby improving the efficiency and accuracy of polarization calibration measurements.

Description

Technical Field

[0001] The present invention relates to the technical field of polarization scattering matrix measurement and calibration processing of radar systems, and in particular to a passive polarization calibration body for calibration of a full polarization measurement radar system. Background Art

[0002] When using a radar system to measure the polarization scattering matrix (PSM) of a target, the measured value cannot directly and accurately reflect the polarization scattering characteristics of the target due to the presence of background clutter, polarization channel gain imbalance, and cross-coupling errors. Polarization calibration is required to obtain the true PSM of the target. As described by Wiesbeck et al. in their 1991 paper "A Complete Error Model for FreeSpace Polarimetric Measurements", the relationship between the measured PSM value and the true value of the target is as follows: Figure 1 shown.

[0003] according to Figure 1 The PSM measurement signal transmission model is shown, and the radar target polarization signal measurement value can be expressed as:

[0004] S M =RST+B (1)

[0005] Where, is the target polarization scattering matrix measurement; is the target's true polarization scattering matrix; is the system transmit channel transfer function; is the system receiving channel transfer function; is the background clutter in the measurement environment.

[0006] Generally, background clutter B can be eliminated by vector subtraction technology. The PSM measurement value after eliminating background clutter is:

[0007] M=S M -B=RST (2)

[0008] Normalize the transmission matrix of the transmitting channel and the receiving channel and expand them into matrix form, then equation (2) can be written as:

[0009]

[0010] Where, is the polarization crosstalk factor; g HH =R HH T HH , g HV=R HH T VV , g VH =R VV T HH , g VV =R VV T VV The operator ⊙ is the Hadamard product.

[0011] From formula (3), it can be seen that there are 8 unknown quantities to be solved in the radar system polarization calibration signal model, namely g HH , g HV , g VH and g VV Four channel gain factors, and and Polarimetric calibration involves measuring several calibration bodies with known theoretical polarimetric scattering matrices. The measurement results are then combined into a system of equations to solve the eight unknowns. Finally, the true value of the polarimetric scattering matrix of the target to be calibrated is calculated based on the measurement results of the target to be calibrated, completing the polarimetric calibration.

[0012] The prior art-1 related to the present invention is analyzed as follows:

[0013] 1) Technical solution of prior art-1

[0014] Theoretically, only two measurements of the calibration object are needed to construct the eight equations. However, due to the symmetry of the passive calibration object, the eight equations obtained from the two measurements are not mutually independent. Measurements on another calibration object are required to obtain the eight independent equations and solve the eight unknowns. A metal rectangular dihedral corner reflector is a commonly used passive polarization calibration object. As described in Unal et al.'s 1994 paper "Calibration of a Polarimetric Radar Using a Rotatable Dihedral Corner Reflector" and Welsh et al.'s 2004 paper "Full Polarimetric Calibration for Radar Cross-Section Measurements: Performance Analysis," the PSM measurements of a rectangular dihedral corner reflector at two different angles (e.g., 0° and 45°) rotated around the radar's line of sight are typically measured. This is then combined with other non-depolarizing calibration objects (such as metal spheres or metal plates) to achieve polarization calibration of the radar system. Taking a rectangular right-angle dihedral reflector as an example, the schematic diagram of its rotation around the radar line of sight is as follows: Figure 2 shown.

[0015] According to the theoretical formula of Physical Optics (PO), the rectangular right-angle dihedral corner reflector PSM rotated clockwise around the radar line of sight by an angle θ is:

[0016]

[0017] Where, w and h are the width and height of each rectangular panel of the dihedral corner reflector, respectively, and λ is the wavelength of the electromagnetic wave.

[0018] When a dihedral corner reflector rotated by an angle θ around the radar line of sight is used as a calibration body, the measurement values ​​of each polarization channel can be expressed as:

[0019]

[0020] Taking the HH polarization component as an example, the measured values ​​of the dihedral corner reflector when it is rotated 0° and 45° are

[0021]

[0022]

[0023] For any measurement value with a rotation angle of θ, it can be linearly represented by the measurement values ​​of the two states of 0° and 45°:

[0024]

[0025] The following four equations can be constructed based on the measured values ​​of the dihedral corner reflector at 0° and 45°:

[0026]

[0027] Another calibration body used is a metal plate as an example. As recorded by Welsh et al. in the article "Full Polarimetric Calibration for Radar Cross-Section Measurements: Performance Analysis" in 2004, according to the PO formula, the theoretical PSM value of the metal plate is:

[0028]

[0029] The PSM measurements for the metal plate are:

[0030]

[0031]

[0032] The following equation can be constructed from the PSM measurements of the metal plate:

[0033]

[0034] By combining the three equations in (12) to (15) and the equation (21), the eight error parameters of the non-reciprocal radar system can be solved and polarization calibration can be completed.

[0035] 2) Disadvantages of Existing Technology-1

[0036] During the polarization calibration measurement process, multiple calibration bodies need to be measured. Replacing the calibration bodies not only consumes more measurement time, but also causes errors in the installation position and line-of-sight alignment of different calibration bodies, thereby affecting the measured value of the polarization scattering matrix of the calibration body and causing the polarization calibration uncertainty to worsen. In addition, during the polarization calibration measurement, the dihedral corner reflector needs to be connected to the shaft of a stepper motor with an angle encoder via a connecting rod. The stepper motor drives the dihedral corner reflector to rotate around the radar line of sight (LOS) for full polarization measurement. For the turntable imaging measurement radar system, additional mechanical rotating devices such as stepper motors will increase the difficulty of aligning the attitude angle of the calibration body during actual measurement, and may also generate interference clutter scattering components, affecting the polarization calibration accuracy.

[0037] The prior art 2 related to the present invention is analyzed as follows:

[0038] 1) Technical solution of prior art 2

[0039] The idea of ​​prior art 2 is to design a new passive polarization calibration body. For example, Xu Xiaojian et al. disclosed in the invention patent with publication number CN201810441875.3, "Passive Polarization Calibration Body for Polarization Scattering Matrix Measurement", and Xu Xiaojian et al. recorded in the article "A New Polarimetric Passive Radar Calibration for FullyPolarimetric Measurement" in 2018 and "A New Quarter Concave Cylinder Linked Dihedral Reflector for Fully Polarimetric Calibration of Wideband Nonreciprocal Radar Systems" in 2023. The new calibration body contains both depolarized scattering components and non-depolarized scattering components, and its PSM theoretical value can be written as:

[0040]

[0041] Where S(θ) represents the polarization scattering matrix when the rotation angle around the radar line of sight is θ, S s It is the non-depolarized scattering component in the polarization component of the calibration body polarization scattering matrix, which has the same characteristics as the scattering body such as "metal ball". d It is the depolarized scattering component in the polarization scattering matrix of the calibration body that has the same scattering characteristics as scatterers such as "dihedral corner reflectors".

[0042] Full polarimetric measurements are performed on the calibration object at three different angles around the radar line of sight: 0°, 90°, and θ. Mathematical calculations on the measurement results achieve an effect similar to that of measuring a metal sphere and a dihedral reflector separately. Subsequent mathematical calculations based on methods described in existing public literature (for example, "A Complete Error Model for Free Space Polarimetric Measurements" by Wiesbeck et al., 1991) can solve for the polarimetric error parameters of the measurement system. Therefore, full polarimetric calibration can be completed using a single passive polarimetric calibration object.

[0043] 2) Disadvantages of Existing Technology 2

[0044] During polarization calibration measurements, this passive polarization calibration body still needs to be driven by a stepper motor to rotate around the radar line of sight for full polarization measurements. For turntable imaging measurement radar systems, additional mechanical rotation devices such as stepper motors will increase the difficulty of aligning the calibration body's attitude angle during actual measurements, and may also generate interfering clutter scattering components, affecting the polarization calibration accuracy. Summary of the Invention

[0045] The present invention aims to provide a passive polarization calibration body for calibrating a full-polarimetric radar system. Specifically, a novel passive polarization calibration body design for measuring the polarization scattering matrix of a turntable imaging radar system is proposed. This design allows full polarization calibration of the radar system by simply rotating the body in azimuth, eliminating the need for additional mechanical rotation devices such as stepper motors. This significantly improves polarization calibration measurement efficiency and minimizes the impact of interfering scattering components on polarization calibration accuracy.

[0046] To achieve the above objectives, the present invention provides a passive polarization calibration body for calibrating a full-polarization measurement radar system. The polarization scattering matrix of the passive polarization calibration body when rotated in azimuth includes a non-depolarized scattering component and a depolarized scattering component. The passive polarization calibration body includes a mirror reflection structure similar to a metal sphere or cylinder and a dihedral structure that rotates at different angles around the radar line of sight.

[0047] Preferably, the mirror reflection structure is a single-curved or double-curved structure.

[0048] Preferably, the dihedral angle structure is a combination of any two of a 0° dihedral corner reflector, a 22.5° dihedral corner reflector, and a 45° dihedral corner reflector.

[0049] Preferably, the theoretical polarization scattering matrix of the passive polarization calibration body when rotating along the azimuth direction has different forms at different azimuth angles, which can be expressed as:

[0050]

[0051] Where S(φ) represents the polarization scattering matrix of the calibration body at azimuth angle φ, S n is the non-depolarized scattered component contained in the calibration body, φ n is the azimuth corresponding to the non-depolarized scattered component, Sd is the depolarized scattered component contained in the calibration body, φ d (θ) is the azimuth angle of the dihedral depolarization scattering component when the radar line of sight is rotated by an angle of θ.

[0052] Preferably, placing a single passive polarization calibration body on a turntable of an imaging measurement radar to perform omnidirectional polarization measurement specifically includes the following steps:

[0053] S1. Place a single passive polarization calibration body on the turntable of the imaging measurement radar to perform omnidirectional polarization measurement, and obtain omnidirectional polarization scattering matrix measurement values ​​when the passive polarization calibration body is rotated at multiple angles along the azimuth direction;

[0054] S2. Measure the targetless background environment to obtain a background clutter matrix, and perform background cancellation on the omnidirectional polarization scattering matrix measurement result obtained in step S1;

[0055] S3. Extracting broadband measurement values ​​of different polarization scattering components according to the azimuth positions of different scattering components of the passive polarization calibration body, and calculating a theoretical value of the polarization scattering matrix of the passive polarization calibration body;

[0056] S4, solving the polarization error parameters of the full polarization measurement radar system;

[0057] S5. Perform polarization calibration on the target to be calibrated.

[0058] Preferably, in step S3, broadband measurement values ​​of the non-depolarized scattered component and the depolarized scattered component are extracted according to the azimuth angle positions of different scattered components of the passive polarization calibration body, and theoretical values ​​of the polarization scattering matrix of different components are calculated. The polarization scattering matrix of different components is expressed as:

[0059]

[0060] Where S1, S2, and S3 represent the three polarization scattering matrix components extracted at different azimuth angles corresponding to different scattering components for polarization calibration.

[0061] Therefore, the present invention adopts the above-mentioned passive polarization calibration body for calibration of a full polarization measurement radar system, and the beneficial effects are as follows:

[0062] (1) The passive polarization calibration body provided by the present invention does not require the use of additional mechanical rotating devices such as stepping motors, which reduces the difficulty of aligning the calibration body with the radar line of sight during the measurement process and reduces the influence of interference scattering components on the polarization calibration measurement accuracy. At the same time, since only a single calibration body needs to be measured, the measurement uncertainty caused by the replacement of the calibration body during the measurement process is reduced, thereby improving the efficiency and accuracy of the polarization calibration measurement.

[0063] (2) Compared with prior art 1, the present invention can complete full polarization calibration of the turntable imaging radar system using a single calibration body, without the need for other calibration bodies. This reduces the need to replace multiple calibration bodies during polarization calibration measurement, saves measurement time, and improves polarization calibration measurement efficiency.

[0064] (3) Compared with the prior art-2, the calibration body proposed in the present invention does not require the use of additional mechanical rotating devices such as stepping motors, which reduces the difficulty of aligning the calibration body with the radar line of sight during the measurement process and reduces the influence of interference scattering components on the polarization calibration measurement accuracy.

[0065] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 The present invention is a polarization scattering matrix measurement signal transmission model of a passive polarization calibration body background technology for full polarization measurement radar system calibration;

[0067] Figure 2 The present invention is a passive polarization calibration body for full polarization measurement radar system calibration. Background technology of the present invention is a dihedral corner reflector that rotates at different angles around the radar line of sight, wherein (a) is a rotation angle of 0°, and (b) is a rotation angle of θ;

[0068] Figure 3 This is a schematic diagram of the geometric structure of an embodiment of a passive polarization calibration body for calibrating a full polarization measurement radar system according to the present invention, which comprises a cylindrical surface, a combination of a 0° dihedral angle and a 22.5° dihedral angle, and an azimuth angle spacing of 112.5°. (a) is a schematic diagram of the cylindrical surface component, (b) is a schematic diagram of the 0° dihedral angle component, (c) is a schematic diagram of the 22.5° dihedral angle component, and (d) is a stereoscopic view of the calibration body.

[0069] Figure 4 This is an embodiment of a passive polarization calibration body for full polarization measurement radar system calibration of the present invention Figure 3 Figure 2 shows the simulation results of the frequency-dependent polarization scattering matrix characteristics of each scattering component of the calibration body, where (a) is a schematic diagram of the cylindrical component, (b) is a schematic diagram of the 0° dihedral angle component, and (c) is a schematic diagram of the 22.5° dihedral angle component.

[0070] Figure 5 Schematic diagram of the geometric structure of a passive polarization calibration body embodiment of the present invention for calibrating a full polarization measurement radar system, comprising a cylindrical surface, a combination of a 22.5° dihedral angle and a 45° dihedral angle, with an azimuth angle spacing of 112.5° between the three. (a) is a schematic diagram of the cylindrical surface component, (b) is a schematic diagram of the 22.5° dihedral angle component, (c) is a schematic diagram of the 45° dihedral angle component, and (d) is a stereoscopic view of the calibration body.

[0071] Figure 6 Schematic diagram of the geometric structure of a passive polarization calibration body embodiment of the present invention for calibrating a full polarization measurement radar system, comprising a cylindrical surface, a combination of a 0° dihedral angle and a 22.5° dihedral angle, with an azimuth angle spacing of 90° between the three. (a) is a schematic diagram of the cylindrical surface component, (b) is a schematic diagram of the 0° dihedral angle component, (c) is a schematic diagram of the 22.5° dihedral angle component, and (d) is a stereoscopic view of the calibration body.

[0072] Figure 7 Schematic diagram of the geometric structure of a passive polarization calibration body embodiment of the present invention for calibrating a full polarization measurement radar system, comprising a cylindrical surface, a combination of a 0° dihedral angle and a 45° dihedral angle, with an azimuth angle spacing of 90° between the three. (a) is a schematic diagram of the cylindrical surface component, (b) is a schematic diagram of the 0° dihedral angle component, (c) is a schematic diagram of the 45° dihedral angle component, and (d) is a stereoscopic view of the calibration body.

[0073] Figure 8 This is a schematic diagram of the geometric structure of an embodiment of a passive polarization calibration body for calibrating a full polarization measurement radar system according to the present invention, comprising an ellipsoidal surface, a combination of a 0° dihedral angle and a 22.5° dihedral angle, with an azimuth angle spacing of 112.5° between the three. (a) is a schematic diagram of the ellipsoidal surface component, (b) is a schematic diagram of the 0° dihedral angle component, (c) is a schematic diagram of the 22.5° dihedral angle component, and (d) is a stereoscopic view of the calibration body. DETAILED DESCRIPTION

[0074] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0075] Unless otherwise defined, the technical or scientific terms used in the present invention shall have the usual meanings understood by persons of ordinary skill in the field to which the present invention belongs. The words "first", "second" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "include" or "comprise" mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0076] A passive polarization calibration body for calibrating a full-polarization measurement radar system has a special form of theoretical polarization scattering matrix. By using a single passive polarization calibration body and measuring its full-polarization scattering data at multiple azimuth rotation angles using a turntable imaging measurement radar, multiple polarization scattering matrix measurement values ​​required for full-polarization calibration of a general non-reciprocal radar system can be obtained, thereby solving for the polarization error parameters of the measurement system and achieving polarization calibration.

[0077] As shown in the figure, a passive polarization calibration body is used to calibrate a full-polarization measurement radar system. The polarization scattering matrix of the passive polarization calibration body when it rotates along the azimuth direction contains a non-depolarized scattering component and a depolarized scattering component. The passive polarization calibration body includes a mirror reflection structure similar to a metal sphere, a metal cylinder or a metal plate, and a dihedral angle structure that rotates at different angles around the radar line of sight. The mirror reflection structure is a single-curved or hyperbolic structure, and the dihedral angle structure is a combination of any two of dihedral angle reflectors of typical angles, such as a 0° dihedral angle reflector, a 22.5° dihedral angle reflector and a 45° dihedral angle reflector.

[0078] The theoretical polarization scattering matrix of the passive polarization calibration body of the present invention has a special form. When the passive polarization calibration body rotates along the azimuth direction, its theoretical polarization scattering matrix has different forms at different azimuth angles, which can be expressed as:

[0079]

[0080] Where S(φ) represents the polarization scattering matrix of the calibration body at azimuth angle φ, S n is the non-depolarized scattered component contained in the calibration body, φ n is the azimuth corresponding to the non-depolarized scattered component, Sd is the depolarized scattered component contained in the calibration body, φ d(θ) is the azimuth angle of the dihedral depolarization scattering component when the radar line of sight is rotated by an angle of θ.

[0081] Figure 3 This is a shape design of the passive polarization calibration body proposed in the present invention. A single passive polarization calibration body is placed on the turntable of the imaging measurement radar to perform omnidirectional polarization measurement. The specific measurement and calibration includes the following steps:

[0082] S1. Place a single passive polarization calibration body on the turntable of the imaging measurement radar to perform omnidirectional polarization measurement, and obtain omnidirectional polarization scattering matrix measurement values ​​when the passive polarization calibration body is rotated at multiple angles along the azimuth direction;

[0083] S2. Measure the targetless background environment to obtain a background clutter matrix, and perform background cancellation on the omnidirectional polarization scattering matrix measurement result obtained in step S1;

[0084] S3. Extracting broadband measurement values ​​of different polarization scattering components according to the azimuth positions of different scattering components of the passive polarization calibration body, and calculating a theoretical value of the polarization scattering matrix of the passive polarization calibration body;

[0085] Specifically, according to the azimuth angle positions of different scattering components of the passive polarization calibration body, the broadband measurement values ​​of the non-depolarized scattering component and the depolarized scattering component are extracted, and the theoretical values ​​of the polarization scattering matrix of different components are calculated. The polarization scattering matrix of different components is expressed as:

[0086]

[0087] Where S1, S2, and S3 represent the three polarization scattering matrix components extracted at different azimuth angles corresponding to different scattering components for polarization calibration.

[0088] S4, solving the polarization error parameters of the full polarization measurement radar system;

[0089] S5. Perform polarization calibration on the target to be calibrated.

[0090] By extracting the polarization scattering matrix measurements of the three different components in step S3 and performing mathematical operations on the full polarization measurement results, a similar effect can be achieved as with separate full polarization measurements of a metal sphere and a dihedral corner reflector. Subsequent mathematical operations can then be performed according to methods found in existing literature (e.g., Wiesbeck et al., 1991, "A Complete Error Model for Free Space Polarimetric Measurements") to determine the polarization error parameters of the radar system and complete the full polarimetric calibration of the measurement radar system.

[0091] A specific shape design scheme of the passive polarization calibration body proposed in the present invention is given below, but the present invention is not limited to this specific shape scheme.

[0092] like Figure 3 As shown, the passive polarization calibration body is composed of three scattering components: cylindrical component, 0° dihedral component and 22.5° dihedral component. The azimuth angle spacing of the three scattering components is 112.5°. The height of the calibration body is h and the diameter is d.

[0093] The electromagnetic scattering calculation of the polarization scattering matrix of the passive polarization calibration body is performed using the Method of Moment (MoM). The specific dimensions of the calibration body and the relevant calculation parameters are set as follows: height h = 0 cm, diameter d = 20 cm, and the calculation frequency is 4 GHz–18 GHz. The polarization scattering matrix of each scattering component varies with frequency as shown in the following figure: Figure 4 shown.

[0094] In the present invention, the passive polarization calibration body is designed in the following way: Figure 3 The cylindrical surface, 0° dihedral angle and 22.5° dihedral angle combination shown. The passive calibration body's external design options may also include but are not limited to the following:

[0095] (1) A combination of a cylindrical surface, a 22.5° dihedral angle, and a 45° dihedral angle, with an azimuth spacing of 112.5°. The geometric structure diagram of the combination is shown in the figure below. Figure 5 shown.

[0096] (2) A combination of a cylindrical surface, a 0° dihedral angle, and a 22.5° dihedral angle, with the azimuth angle spacing of the three being 90°. The geometric structure diagram is shown in the figure below. Figure 6 shown.

[0097] (3) A combination of a cylindrical surface, a 0° dihedral angle, and a 45° dihedral angle, with the azimuth angle spacing of the three being 90°. The geometric structure diagram is shown in the figure below. Figure 7 shown.

[0098] (4) A combination of an ellipsoid or sphere, a 0° dihedral angle, and a 22.5° dihedral angle, with an azimuth angle spacing of 112.5°. The geometric structure diagram is as follows: Figure 8 shown.

[0099] For calibration bodies with other external designs, as long as the variation characteristics of their polarization scattering matrix with azimuth angle satisfy equation (1), they can be analyzed and calculated according to the concept of the present invention. By simply performing omnidirectional measurements on a single calibration body of this type, full polarization calibration of the turntable measurement radar system can be achieved.

[0100] Therefore, the present invention adopts the above-mentioned passive polarization calibration body for calibrating the full-polarization measurement radar system, eliminating the need for additional mechanical rotation devices such as stepping motors, thereby reducing the difficulty of aligning the calibration body with the radar line of sight during the measurement process and reducing the impact of interference scattering components on the polarization calibration measurement accuracy. At the same time, since only a single calibration body needs to be measured, the measurement uncertainty caused by calibration body replacement during the measurement process is reduced, thereby improving the efficiency and accuracy of polarization calibration measurements.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A passive polarization calibration body for calibrating a full polarization measurement radar system, characterized by: The polarization scattering matrix of the passive polarization calibration body when rotating along the azimuth direction includes a non-depolarized scattering component and a depolarized scattering component. The passive polarization calibration body includes a mirror reflection structure similar to a metal sphere or a cylinder and a dihedral angle structure rotating at different angles around the radar line of sight. The dihedral angle structure is a combination of any two of a 0° dihedral angle reflector, a 22.5° dihedral angle reflector, and a 45° dihedral angle reflector.

2. The passive polarization calibration body for full polarization measurement radar system calibration according to claim 1, characterized in that: The mirror reflection structure is a single-curved surface or a double-curved surface structure.

3. The passive polarization calibration body for full polarization measurement radar system calibration according to claim 1, characterized in that: The theoretical polarization scattering matrix of the passive polarization calibration body when rotating along the azimuth direction has different forms at different azimuth angles, which can be expressed as: Where S(φ) represents the polarization scattering matrix of the calibration body at azimuth angle φ, S n is the non-depolarized scattered component contained in the calibration body, φ n is the azimuth angle corresponding to the non-depolarized scattered component, S d is the depolarized scattered component contained in the calibration body, φ d (θ) is the azimuth angle of the dihedral depolarization scattering component when the radar line of sight is rotated by an angle of θ.

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