A method and system for measuring the full polarimetric reflectivity of a radar wave absorbing material

Abstract

This invention relates to the field of electromagnetic measurement technology, and more particularly to a method and system for measuring the total polarization reflectivity of radar absorbing materials. The method includes: constructing a measurement system with dual-polarization transceiver capability and completing polarization calibration; measuring the main polarization radar scattering cross section of a metal sample of the same size as a first measurement value; measuring the total polarization scattering matrix of the sample covered with absorbing material as a second measurement value; and calculating the total polarization reflectivity matrix of the material based on the first and second measurement values. The system includes a compacted-field anechoic chamber, a vector network analyzer, a dual-polarization transceiver link, etc., and is configured to automatically execute the above measurement and calculation process. This invention, by introducing a metal sample as a reference and performing differential calculations, achieves a systematic, automated, and accurate measurement of the total polarization reflectivity of radar absorbing materials, overcoming the technical limitation of traditional methods that can only test reflectivity with the same polarization.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic measurement technology, and in particular to a method and system for measuring the reflectivity of radar absorbing materials. Background Technology

[0002] Reflectivity is an important indicator for evaluating the performance of radar absorbing materials. Under specific polarization and frequency conditions, electromagnetic waves are incident from the same direction and with the same power density onto a radar absorbing material plane and a good conductor plane. The ratio of the specular reflected power of the radar absorbing material plane to that of a good conductor plane of the same size is the reflectivity of the material. Since a good conductor plane does not possess polarization-reversing characteristics, conventional reflectivity tests only perform measurements of the same polarization (such as HH or VV).

[0003] However, with the development of microwave absorbing material technology, more novel materials with polarization deflection characteristics have emerged. For these materials, the traditional method of only measuring the same polarization reflectivity is no longer sufficient to comprehensively and accurately evaluate their electromagnetic properties. Specifically, traditional methods cannot obtain the cross-polarization (HV, VH) reflectivity components of the material, and therefore cannot describe the material's ability to change the polarization state of the incident electromagnetic wave. This limits the complete evaluation of the performance of novel microwave absorbing materials.

[0004] Therefore, there is an urgent need for a solution that can accurately measure the full polarization reflectivity (including HH, HV, VH, VV) of radar absorbing materials under indoor conditions. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for measuring the total polarization reflectivity of radar absorbing materials, so as to solve the problem that traditional reflectivity measurement methods cannot accurately describe and obtain the total polarization components, especially the cross-polarization components.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for measuring the fully polarimetric reflectivity of a radar absorbing material, comprising the following steps: A measurement system with dual-polarization transceiver capability is constructed. The system includes a vector network analyzer, a power amplifier, a low-noise amplifier, a polarization switching switch, a dual-polarization transceiver feed, and a compact field reflector. The transmit link is sequentially connected to the output of the vector network analyzer, the power amplifier, the transmit polarization switching switch, and the transmit feed. The receive link is sequentially connected to the receive feed, the receive polarization switching switch, the low-noise amplifier, and the receive end of the vector network analyzer. Complete system polarization calibration; The metal sample is placed vertically in the test area, and the main polarization radar cross section of the metal sample is measured using the measurement system to obtain the first measured values ​​of HH polarization and VV polarization. The radar absorbing material sample to be tested is attached to another metal sample identical to the metal sample to form a material sample. The material sample is then placed vertically in the test area in the same manner. The full polarization scattering matrix of the material sample is measured using the measurement system to obtain the second measured values ​​of HH, HV, VH, and VV polarizations. Using the first and second measured values, the fully polarimetric reflectivity matrix of the radar absorbing material is calculated.

[0007] Optionally, the completion of system polarization calibration specifically includes: The four polarization error terms HH, HV, VH, and VV of the measurement system are obtained by using either a single calibration body or a three calibration body calibration method.

[0008] Optionally, the dual-polarized transceiver feed is a dual-polarized antenna, which works in conjunction with the polarization switching switch to achieve different polarization combinations.

[0009] Optionally, the dual-polarized transceiver feed is a single-polarized feed antenna with a rotating mechanism, through which the polarization combination state is adjusted.

[0010] Optionally, the fully polarimetric reflectivity matrix of the radar absorbing material is obtained by the following formula: in, This represents the fully polarimetric reflectivity matrix of the material, in dB. , , , This represents the polarization scattering matrix of the second measured value, i.e., the radar absorbing material sample. The components are in dBm. 2 ; , This represents the first measured value, namely the HH and VV polarized radar cross sections of the metal sample, in dBm. 2 .

[0011] In a second aspect, the present invention also provides a system for measuring the fully polarimetric reflectivity of radar absorbing materials, for performing the method described in any one aspect, the system comprising: A compressed field anechoic chamber, wherein the compressed field reflecting surface is provided inside, the compressed field reflecting surface is used to form a quiet zone; Vector network analyzer; Power amplifiers and low-noise amplifiers; Polarization switching switch; A dual-polarized transceiver feed is disposed in the compressed field dark chamber and faces the compressed field reflective surface; The vector network analyzer's output terminal, the power amplifier, the transmit polarization switch, and the transmit feed are sequentially connected to form a transmit link; the receive feed, the receive polarization switch, the low-noise amplifier, and the vector network analyzer's receiving terminal are sequentially connected to form a receive link. The system is configured to: perform system polarization calibration; control the polarization switching switch and the dual-polarization transceiver feed to measure the main polarization radar scattering cross section of the metal sample to obtain a first measurement value; control the polarization switching switch and the dual-polarization transceiver feed to measure the full polarization scattering matrix of the material sample with attached radar absorbing material to obtain a second measurement value; and use the first measurement value and the second measurement value to calculate the full polarization reflectivity matrix of the radar absorbing material.

[0012] Optionally, the system further includes a main control computer, which is connected to the vector network analyzer and the turntable control cabinet, and is used to control the measurement process, data processing, and perform calculations to obtain the fully polarimetric reflectivity matrix of the radar absorbing material.

[0013] The above-described technical solution of the present invention has the following advantages: The present invention provides a method for measuring the total polarization reflectivity of radar absorbing materials. By constructing a dual-polarization transceiver measurement system, the main polarization radar scattering cross section of a metal sample of the same size is first measured as a reference value. Then, the total polarization scattering matrix of the sample covered with absorbing material is measured. Finally, the total polarization reflectivity matrix of the material is directly obtained by calculating the difference between the two measurements. This method enables systematic indoor measurement of the total polarization reflectivity (including cross-polarization components) of radar absorbing materials, solving the technical problem that traditional methods can only test the same polarization reflectivity and cannot comprehensively evaluate the polarization characteristics of materials.

[0014] This invention also provides a fully polarimetric reflectance measurement system. This system integrates a compact-field anechoic chamber, a vector network analyzer, and a dual-polarization transceiver link, and is configured to automatically execute the entire process of polarization calibration, reference measurement, target measurement, and reflectance calculation. This system hardware-encapsulates and automates the aforementioned process, enabling automatic polarization switching, data acquisition, reference comparison, and reflectance calculation, directly outputting the final fully polarimetric reflectance matrix. This significantly improves measurement efficiency, result consistency and reliability, and substantially reduces operational complexity. Attached Figure Description

[0015] The accompanying drawings are provided for illustrative purposes only, and the proportions and quantities of the components in the drawings may not be consistent with the actual product.

[0016] Figure 1 This is a schematic diagram of a radar absorbing material full polarization reflectivity measurement system according to an embodiment of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0018] The method for measuring the fully polarimetric reflectivity of radar absorbing materials provided in this invention includes the following steps: First, build such Figure 1 The measurement system shown consists of a vector network analyzer, a power amplifier, a low-noise amplifier, a polarization switching switch, a dual-polarized transceiver feed, and a compact field reflector. The vector network analyzer is used for signal generation and processing, the power amplifier amplifies the output signal, the low-noise amplifier amplifies the received signal, the polarization switching switch is used to adjust the polarization of the feed antenna on the transmit and receive links, and the feed and compact field reflector are used to generate a plane wave illumination environment within the compact field anechoic chamber.

[0019] The feed antenna can be a dual-polarized antenna combined with a polarization switching switch to achieve different polarization combinations. Alternatively, a single-polarized feed antenna with a rotating mechanism can be used, allowing adjustment of the polarization combination.

[0020] The transmit link connects sequentially to a power amplifier, a transmit polarization switch, and a transmit feed via the output of the vector network analyzer. After being amplified by the power amplifier, the transmit signal is switched to the corresponding polarization by the transmit polarization switch and radiated into the compressed-field anechoic chamber via the transmit feed. The receive link connects to the receive end of the vector network analyzer via a receive feed, a receive polarization switch, and a low-noise amplifier. The received signal is switched to the corresponding polarization by the receive polarization switch via the receive feed, amplified by the low-noise amplifier, and then processed by the vector network analyzer.

[0021] Next, the system polarization calibration is completed. During system polarization calibration, either a single-calibrator calibration method or a three-calibrator calibration method must be used to obtain the four polarization error terms: HH, HV, VH, and VV. This completes the system polarization calibration, enabling the system to accurately acquire the target's radar cross section.

[0022] After completing the system polarization calibration, place the metal sample on a low-dielectric-constant foam support (e.g., a polystyrene foam support). Using a small foam clamp with grooves, place the metal sample perpendicular to the ground on the foam support. An electronic level can be used to confirm the perpendicularity of the metal sample to the darkroom floor. Adjust the orientation of the metal sample so that electromagnetic waves can perpendicularly illuminate its surface. The small foam clamp is prior art and will not be described in detail here.

[0023] After placing the metal template, the pre-built measurement system is used to measure the primary polarization radar cross section of the metal template, that is, to obtain the radar cross section values ​​of the HH and VV polarization combinations, denoted as . and .

[0024] Next, the radar-absorbing material sample is measured. A radar-absorbing material sample of the same size as the metal sample is attached to the same metal sample to form a material-metal composite sample (i.e., the material sample). The material sample is placed in the test area in exactly the same way as in the second step (same support, same vertical orientation, same spatial position) so that electromagnetic waves irradiate its plane perpendicularly.

[0025] After placing the material sample, the fully polarimetric scattering matrix of the material sample was measured using the same measurement system. Specifically, the radar cross-section values ​​of the four polarization combinations HH, HV, VH, and VV were obtained sequentially or simultaneously and denoted as follows: , , , .

[0026] Finally, using the first and second measured values, the total polarization reflectivity matrix of the radar absorbing material is calculated. In a preferred example, the total polarization reflectivity matrix of the radar absorbing material is calculated using the following formula (1). (Unit: dB): (1) in, , , , This represents the measured value of the polarization scattering matrix of the radar absorbing material sample, i.e., the second measured value, in dBm. 2 ; , This represents the first measured value, namely the HH and VV polarized radar cross sections of the metal sample, in dBm. 2 .

[0027] The total polarizability of the material, expressed in matrix form, can be directly obtained through calculation using formula (1). For example, Represents: Under vertical (V) polarized wave incidence, the horizontal (H) polarized scattering component generated by the absorbing material sample, relative to the specular reflection component of an ideal conductor (metal sample) under vertical polarized incident (as shown in the figure). The degree of attenuation (characterized by the reflectivity of the radar absorbing material) is called the HV polarization reflectivity. Similarly, the HH polarization RCS of the absorbing material sample is subtracted from the HH polarization RCS of the metal sample to obtain the HH polarization reflectivity of the absorbing material; the VH polarization RCS of the absorbing material sample is subtracted from the HH polarization RCS of the metal sample to obtain the VH polarization reflectivity; and the VV polarization RCS of the absorbing material sample is subtracted from the VV polarization RCS of the metal sample to obtain the VV polarization reflectivity. Thus, the total polarization reflectivity of the radar absorbing material can be obtained.

[0028] The method in this embodiment is the first to systematically realize the measurement and quantitative expression of the full polarization reflectivity of radar absorbing materials in an indoor confined field environment. By introducing a metal template benchmark and a clear matrix calculation formula, it solves the problem of the inability to obtain cross-polarization reflectivity and provides a standardized evaluation method.

[0029] This embodiment also provides a system for measuring the fully polarimetric reflectivity of radar absorbing materials. This system is deployed in a microwave anechoic chamber, and its core components and connections are as follows: Figure 1 As shown, the system specifically includes a compacted-field anechoic chamber, a vector network analyzer, a power amplifier, a low-noise amplifier, a polarization switching switch, a dual-polarization transceiver feed, a compacted-field reflector, and a main control computer. The main control computer is communicatively connected to the vector network analyzer and the turntable control cabinet. The main control computer runs dedicated measurement and control software, which programs and implements the complete process of the above measurement method and includes a built-in function module for calculation based on formula (1).

[0030] The system workflow is as follows: software controls the turntable rotation, sets vector network analyzer parameters, controls the polarization switching switch status, and automatically acquires and stores background data from the empty anechoic chamber, metal sample data, and microwave absorbing material sample data. (In acquiring...) , as well as , , , Then, the software automatically calls the calculation module to execute the calculation shown in formula (1), and finally displays or outputs the fully polarimetric reflectivity matrix on the interface. This system can automatically complete polarization switching, data acquisition, benchmark comparison, and reflectivity calculation, and directly output the final fully polarized reflectivity matrix, greatly improving measurement efficiency, result reliability, and ease of operation.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that not every embodiment contains only one independent technical solution, and in the absence of conflict between solutions, the various technical features mentioned in each embodiment can be combined in any way to form other implementation methods that can be understood by those skilled in the art.

[0032] Furthermore, without departing from the scope of the present invention, modifications to the technical solutions described in the foregoing embodiments, or equivalent substitutions of some of the technical features, shall not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for measuring the fully polarimetric reflectivity of a radar absorbing material, characterized in that, Includes the following steps: A measurement system with dual-polarization transceiver capability is constructed. The system includes a vector network analyzer, a power amplifier, a low-noise amplifier, a polarization switching switch, a dual-polarization transceiver feed, and a compact field reflector. The transmit link is sequentially connected to the output of the vector network analyzer, the power amplifier, the transmit polarization switching switch, and the transmit feed. The receive link is sequentially connected to the receive feed, the receive polarization switching switch, the low-noise amplifier, and the receive end of the vector network analyzer. Complete system polarization calibration; The metal sample is placed vertically in the test area, and the main polarization radar cross section of the metal sample is measured using the measurement system to obtain the first measured values ​​of HH polarization and VV polarization. The radar absorbing material sample to be tested is attached to another metal sample identical to the metal sample to form a material sample. The material sample is then placed vertically in the test area in the same manner. The full polarization scattering matrix of the material sample is measured using the measurement system to obtain the second measured values ​​of HH, HV, VH, and VV polarizations. Using the first and second measured values, the fully polarimetric reflectivity matrix of the radar absorbing material is calculated.

2. The method according to claim 1, characterized in that: The completion of system polarization calibration specifically includes: The four polarization error terms HH, HV, VH, and VV of the measurement system are obtained by using either a single calibration body or a three calibration body calibration method.

3. The method according to claim 1, characterized in that: The dual-polarized transceiver feed is a dual-polarized antenna, which, in conjunction with the polarization switching switch, enables different polarization combinations.

4. The method according to claim 1, characterized in that: The dual-polarized transceiver feed is a single-polarized feed antenna with a rotating mechanism, which adjusts the polarization combination state.

5. The method according to any one of claims 1 to 4, characterized in that: The fully polarimetric reflectivity matrix of the radar absorbing material is obtained by the following formula: in, This represents the fully polarimetric reflectivity matrix of the material, in dB. , , , This represents the polarization scattering matrix of the second measured value, i.e., the radar absorbing material sample. The components are in dBm. 2 ; , This represents the first measured value, namely the HH and VV polarized radar cross sections of the metal sample, in dBm. 2 .

6. A system for measuring the fully polarimetric reflectivity of radar absorbing materials, characterized in that: The system for performing the method according to any one of claims 1 to 5 comprises: A compressed field anechoic chamber, wherein the compressed field reflecting surface is provided inside, the compressed field reflecting surface is used to form a quiet zone; Vector network analyzer; Power amplifiers and low-noise amplifiers; Polarization switching switch; A dual-polarized transceiver feed is disposed in the compressed field dark chamber and faces the compressed field reflective surface; The vector network analyzer's output terminal, the power amplifier, the transmit polarization switch, and the transmit feed are sequentially connected to form a transmit link; the receive feed, the receive polarization switch, the low-noise amplifier, and the vector network analyzer's receiving terminal are sequentially connected to form a receive link. The system is configured to: perform system polarization calibration; control the polarization switching switch and the dual-polarization transceiver feed to measure the main polarization radar scattering cross section of the metal sample to obtain a first measurement value; control the polarization switching switch and the dual-polarization transceiver feed to measure the full polarization scattering matrix of the material sample with attached radar absorbing material to obtain a second measurement value; and use the first measurement value and the second measurement value to calculate the full polarization reflectivity matrix of the radar absorbing material.

7. The system according to claim 6, characterized in that: The system also includes a main control computer, which is connected to the vector network analyzer and the turntable control cabinet. The main control computer is used to control the measurement process, data processing, and to perform calculations to obtain the fully polarimetric reflectivity matrix of the radar absorbing material.

Images