Double-station RCS scaling test system and test method for electrically large-size target in indoor compact range
By designing a dual-station RCS scaled-down test system for electrically large targets in an indoor compact field, and by adopting the calibration body substitution method and scaled-down target model, the problem of dual-station RCS measurement of electrically large targets under indoor field constraints was solved, and efficient electromagnetic scattering characteristic measurement was achieved in a limited space.
Patent Information
- Application Number
- CN202511330562.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-17
- Publication Date
- 2026-02-10
Smart Images
Figure CN121500263A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electromagnetic scattering measurement, specifically to a method for bistatic measurement of the radar cross section of electrically large scaled targets and certain full-size components under indoor field conditions. Background Technology
[0002] Radar cross section (RCS) is a crucial characteristic of radar targets, and RCS testing methods have become increasingly accurate, reliable, and efficient with technological advancements. RCS measurement methods can be categorized by site conditions into indoor and outdoor measurements. They can also be classified by radar station receiving and transmitting positions into monostatic and bistatic RCS. Furthermore, they can be classified by target physical characteristics into electrically large target RCS measurement and electrically small target RCS measurement.
[0003] The advantages of indoor RCS measurements include a controlled electromagnetic environment, resistance to external interference, and good confidentiality. However, indoor measurements also present challenges, such as the large footprint required for indoor RCS system layouts to meet the far-field conditions for electrically large targets. Therefore, a compact field is needed to achieve the far-field conditions required for RCS testing. In practical military applications, most stealth targets are typically monostatic stealth, meaning that the radar waves reflected from the target in the direction of radar wave incidence are very weak, thus achieving a stealth effect that makes them undetectable by radar. However, most stealth targets often fail to achieve stealth in other directions, so bistatic RCS measurements are necessary to determine the stealth performance of stealth targets.
[0004] Indoor scaled-down target RCS measurement is conducted in ordinary microwave anechoic chambers and compressed fields to measure the point-frequency and swept-frequency radar cross sections, complex radar cross sections, polarization scattering matrices, and high-resolution microwave imaging of scaled-down target models such as aircraft and missiles, as well as certain full-size components. However, existing indoor scaled-down target RCS measurements only use single-station methods or are designed for electrically small targets. Therefore, there is an urgent need to propose a bistatic RCS scaled-down testing method for electrically large targets in an indoor compressed field, enabling bistatic measurement of electrically large targets. Summary of the Invention
[0005] The purpose of this invention is to propose an indoor compact field electric large-size target bistatic RCS scaling test system and an indoor compact field electric large-size target bistatic RCS scaling test method based on the system.
[0006] The technical solution to achieve the purpose of this invention is as follows: an indoor compact field electric large-size target bistatic RCS scaled-down test system, including a transmitter feed, a receiver feed, a transmitter compact field parabolic reflector, a receiver compact field parabolic reflector, a transmitter compact field movable support, a receiver compact field movable support, a target under test, a target placement turntable, a vector network analyzer, a three-port power divider, and a control and data processing center. The target under test includes two types: one is a calibration body, and the other is a scaled-down target model.
[0007] The launch feed and the launch compaction field parabolic reflector form the launch compaction field. The launch feed is located at the focal point of the launch compaction field parabolic reflector and faces the center of the launch compaction field parabolic reflector. The launch compaction field is fixed on the launch compaction field movable support so that the indoor position of the launch compaction field can be moved according to experimental requirements.
[0008] The receiving feed and the receiving compact field parabolic reflector form the receiving compact field. The receiving feed is located at the focal point of the receiving compact field parabolic reflector and faces the center of the receiving compact field parabolic reflector. The receiving compact field is fixed on the movable support of the transmitting compact field so that the indoor position of the receiving compact field can be moved according to experimental requirements.
[0009] The launch compact field parabolic launch surface and the receiving compact field parabolic launch surface form a certain angle with the target placement turntable as the axis. This angle can be changed by moving the movable support of the launch compact field or the movable support of the receiving compact field to simulate different dual-station positions in actual scenarios.
[0010] The three-port power divider consists of an input terminal, a first output terminal, and a second output terminal. The low-frequency signal generated by the vector network analyzer is fed into the input terminal of the three-port power divider. The first output terminal of the three-port power divider is connected to the input terminal of the transmitter feed, and the second output terminal of the three-port power divider is connected to the input terminal of the receiver feed, ensuring the signal coherence of the two stations.
[0011] Furthermore, the common quiet zone formed by the launch compaction field and the receiving compaction field is not smaller than the size of the target to be measured.
[0012] Furthermore, when fixing the horizontal height of the transmitting and receiving compressed fields, the center of the parabolic reflector of the transmitting compressed field must be located on the same horizontal plane as the center of the parabolic reflector of the receiving compressed field. The height of this horizontal plane is the same as the height of the horizontal plane where the target is located.
[0013] Furthermore, the scaled-down model is a complete replica of the full-size target system. It requires that the scaled-down size be a linear simulation of the full-size real target size, with identical electromagnetic conditions. The scaled-down size should be less than or equal to the size of the compacted field quiet zone in order to obtain the electromagnetic scattering characteristics of the real target.
[0014] Furthermore, the parabolic reflector of the compressed emission field transforms the spherical wave radiated by the emission feed into a plane wave at a relatively short distance and transmits it to the target under test, so as to form a plane wave illumination area (quiet zone) with an almost ideal amplitude and phase distribution in a limited space, thereby meeting the requirements of far-field testing.
[0015] Furthermore, the receiving compressed field parabolic reflector transforms the plane wave radiated by the target under test into a spherical wave at a relatively short distance and transmits it to the receiving feed, completing the transformation from far-field conditions to near-field conditions on the test site within a limited space.
[0016] Furthermore, the transmitting feed includes a first controlled frequency source, a frequency multiplier, a power amplifier, and a transmitting antenna. The first output terminal of the three-port power divider is connected to the input terminal of the first controlled frequency source to achieve the first frequency multiplication of the measurement signal. The output terminal of the first controlled frequency source is connected to the input terminal of the frequency multiplier to achieve the second frequency multiplication of the measurement signal. The output terminal of the frequency multiplier is connected to the input terminal of the power amplifier to increase the power of the measurement signal. The output terminal of the power amplifier is connected to the transmitting antenna to transmit the generated high-frequency measurement signal to the transmitting compact field through the transmitting antenna.
[0017] Furthermore, the receiving feed includes a second controlled frequency source, a frequency multiplier, a mixer, a receiving antenna, a low-noise amplifier, an intermediate frequency (IF) filter circuit, and an IF amplifier circuit. The second output of the three-port power divider is connected to the input of the second controlled frequency source to achieve the first frequency multiplication of the measurement signal. The output of the second controlled frequency source is connected to the input of the frequency multiplier to achieve the second frequency multiplication of the measurement signal. The output of the frequency multiplier is connected to the local oscillator input of the mixer. The receiving antenna is used to receive the echo signal reflected from the receiving compression area. The receiving antenna is connected to the input of the low-noise amplifier to increase the power of the echo signal. The output of the low-noise amplifier is connected to the RF input of the mixer to mix the echo signal generated by the target with the local oscillator signal to obtain the IF value. The IF output of the mixer is connected to the input of the IF filter circuit. The output of the IF filter circuit is connected to the input of the IF amplifier circuit. The output of the IF amplifier circuit is connected to the input of the vector network analyzer.
[0018] Furthermore, the antenna adopts a standard gain corrugated horn antenna, with corrugated slots cut into the inner wall of a regular horn.
[0019] A method for scaling down the RCS of a large-size electric target in an indoor compact field, based on the aforementioned indoor compact field large-size electric target bistatic RCS scaling down test system, employs a calibration body substitution method to measure the RCS, and includes the following steps:
[0020] Step 101: After setting up an indoor compact field electric large-size target bistation RCS scaled-down test system, place the target to be tested bracket on the target placement turntable without placing the target to be tested, and obtain the indoor background signal when there is no target.
[0021] Step 102: Fix the calibration body onto the target bracket to be tested;
[0022] Step 103: Set the target bracket and target placement turntable to the desired state so that the calibration body is at the predetermined distance, azimuth angle and elevation angle;
[0023] Step 104: The control and data processing center controls the vector network analyzer to generate a reference signal, which is converted into a high-frequency, high-power measurement signal by the transmitting feed and transmitted to the transmitting compact field parabolic surface. This signal is then converted into a quasi-plane wave and irradiated onto the target. The calibration body reflects the measurement signal to the receiving compact field parabolic surface. The measurement signal at this time serves as an echo signal, containing the target characteristic information of the calibration body. The receiving compact field parabolic surface focuses the echo signal, which is then received by the receiving feed. The intermediate frequency signal from the receiving feed is output to the vector network analyzer.
[0024] Step 105: The control and data processing center records the intermediate frequency signal containing the target characteristic information of the calibration body;
[0025] Step 106: Replace the calibration body with a scaled-down target model;
[0026] Step 107: The control and data processing center controls the vector network analyzer to generate a reference signal, which is converted into a high-frequency, high-power measurement signal by the transmitting feed and transmitted to the transmitting compact field parabolic surface. This signal is converted into a quasi-plane wave and illuminates the target under test. The scaled-down target model reflects the measurement signal to the receiving compact field parabolic surface. The measurement signal at this time serves as an echo signal, containing the target characteristic information of the calibration body. The receiving compact field parabolic surface focuses the echo signal, which is received by the receiving feed. The intermediate frequency signal from the receiving feed is output to the vector network analyzer.
[0027] Step 108: The control and data processing center records the intermediate frequency signal containing the target characteristic information of the scaled-down target model;
[0028] Step 109: Using the known RCS from the calibration body, the intermediate frequency signal output from the receiving feed obtained by measuring the calibration body, and the intermediate frequency signal output from the receiving feed obtained by measuring the scaled-down target model, calculate and process to obtain the RCS value of the scaled-down target model.
[0029] Compared with the prior art, the present invention has the following significant advantages: it overcomes the problem that traditional electrical large-size target measurement is limited by the site and cannot be carried out indoors, fills the gap in indoor compact field bistation RCS scaling test of electrical large-size targets, and has great application prospects. Attached Figure Description
[0030] Figure 1 This is a schematic diagram of the construction of a single compression field according to the present invention.
[0031] Figure 2This is a schematic diagram (top view) of the compact field dual-station RCS testing system of the present invention.
[0032] Figure 3 This is a side view of the layout of the compression field testing system of the present invention.
[0033] Figure 4 This is a block diagram of the test transceiver system of the present invention. Figure 5 This is a flowchart of the testing method of the present invention. Detailed Implementation
[0034] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.
[0035] This invention uses a linearly scaled-down model of a calibration body and a full-size target (i.e., a scaled-down target model) as the target under test. A dual-station, compressed-field test system is constructed in a microwave anechoic chamber using a transmit feed, a receive feed, a transmit compressed-field parabolic reflector, a receive compressed-field parabolic reflector, a target placement turntable, and a control and data processing center. By measuring the receiver output power (in W) of the calibration body with a known RCS value under specific azimuth and attitude, and the receiver output power (in W) of the target under test with an unknown RCS value under specific azimuth and attitude, a mathematical model is established using the known RCS of the calibration body, the intermediate frequency (IF) signal from the receive feed measured by the calibration body, and the IF signal from the receive feed measured by the scaled-down target model. The model is then used to calculate and process the definite RCS value of the scaled-down target model under the specified test conditions.
[0036] An indoor compact field electric large-size target bistation RCS scaling test system includes a transmitter feed, a receiver feed, a transmitter compact field parabolic reflector, a receiver compact field parabolic reflector, a transmitter compact field movable support, a receiver compact field movable support, a target under test, a target under test bracket, a target placement turntable, a vector network analyzer, a three-port power divider, and a control and data processing center.
[0037] The vector network analyzer generates a reference signal, which is converted into a high-frequency, high-power measurement signal by a transmitting feed and transmitted to a transmitting compressed-field parabolic surface. This signal is then converted into a quasi-plane wave and directed to the target under test. The target reflects the measurement signal back to the receiving compressed-field parabolic surface. This measurement signal, as an echo signal, contains target characteristic information. The receiving compressed-field parabolic surface focuses the echo signal, which is then received by the receiving feed. The intermediate frequency signal from the receiving feed is output to the vector network analyzer. The control and data processing center processes the experimental data to obtain the target's RCS value. Specifically, by controlling experimental variables, experimental data from a calibration body and a scaled-down target model under identical experimental conditions are measured. The RCS value of the scaled-down target model is obtained through a substitution method.
[0038] (1) Target to be measured
[0039] The targets to be tested fall into two categories: calibration bodies and scaled-down target models. The scaled-down model is a complete replica of the full-size target system. It requires that the scaled-down size be a linear simulation of the full-size real target size, with identical electromagnetic conditions. The scaled-down size should be less than or equal to the size of the compressed field quiet zone to obtain the electromagnetic scattering characteristics of the real target.
[0040] Measurements using a scaled-down model must meet similarity criteria (for metallic targets), as shown in Equation 1.1.1, where L is the size of the full-size target; f is the measurement signal frequency of the full-size target system; L m The size of the target model at scale; f m This represents the frequency of testing in the scaled-down model system.
[0041]
[0042] The similarity criterion states that if the model size is reduced (or increased) by a factor of m, the required measurement frequency must be increased (or reduced) by a factor of m, where m is called the scaling factor. The radar cross section σ of the measured scaled-down target model... m The radar cross section σ of a full-size real target has the following relationship:
[0043]
[0044] According to Equation 1.1.2, the larger the scaling factor, the easier it is to meet the far-field conditions. Assuming the scaling factor is 100, the maximum size of the scaled-down aircraft model is 0.5 meters, and the test frequency becomes 100 GHz. At this time, the test distance to meet the far-field conditions is greater than 167 meters, which is still difficult to achieve in the field. Therefore, it is necessary to build a compact field indoors to create the far-field conditions.
[0045] (2) Transmitting compressed field and receiving compressed field
[0046] See Figure 1The emission feed and the emission compaction field parabolic reflector constitute the emission compaction field. The emission feed is located at the focal point of the emission compaction field parabolic reflector and faces the center of the emission compaction field parabolic reflector. The emission compaction field is fixed on a movable support frame to allow the indoor position of the emission compaction field to be moved according to experimental requirements.
[0047] The receiving feed and the receiving compressed field parabolic reflector constitute the receiving compressed field. The receiving feed is located at the focal point of the receiving compressed field parabolic reflector and faces the center of the receiving compressed field parabolic reflector. The receiving compressed field is fixed on the movable support of the transmitting compressed field so that the indoor position of the receiving compressed field can be moved according to experimental requirements.
[0048] (3) Microwave anechoic chamber indoor dual-station compact field test environment
[0049] See Figure 2 1. Set up a dual-station compact field test environment in a microwave anechoic chamber. The quiet zone should be no less than 0.5 meters (i.e. no less than the size of the target to be tested). The transmission direction of the transmitting compact field and the receiving direction of the receiving compact field should form a certain angle with the target placement turntable as the axis, so that the transmitting compact field and the receiving compact field form a common quiet zone at the target placement turntable. When setting up the test environment on site, the target to be tested bracket is placed on the target placement turntable in the common quiet zone, and the target to be tested is placed on the target to be tested bracket.
[0050] Furthermore, the target bracket and target placement turntable are made of low RCS metal and wrapped with low-density absorbing foam material. During the test, the pitch angle of the target is controlled by controlling the target bracket, and the horizontal azimuth angle of the target is controlled by controlling the target placement turntable. The illumination direction on the target is changed by moving the transmitting or receiving compact field to measure the target RCS value under different conditions.
[0051] See Figure 3 A more detailed view of the compacted field setup is shown in the side view. The height and position of the target placement turntable must ensure that the target under test is within the common quiet zone of the transmission / reception compacted field. After determining the spatial position of the target under test and fixing the parabolic emission surface of the transmission / reception compacted field to the indoor movable support, the horizontal plane where the target under test is located is the center plane of the parabolic emission surface of the transmission / reception compacted field.
[0052] The transmitting and receiving compacted field parabolic transmitting surfaces maintain a certain angle with respect to the target under test. This angle can be changed by moving the movable support of the transmitting or receiving compacted field to simulate different bistation positions in actual scenarios. It is required that the common quiet zone formed by the transmitting and receiving compacted fields under this angle is not smaller than the size of the target under test.
[0053] (4) Fully coherent system
[0054] See Figure 4 The vector network analyzer, the transmitter feed (internal structure), the receiver feed (internal structure), the control and data processing center, and the target placement turntable constitute a fully coherent system capable of amplitude and phase measurement.
[0055] The vector network analyzer generates a 120MHz clock signal, which is split into two paths by a power divider. These paths serve as reference clocks for the transmitting and receiving feeds. The transmitting feed first generates a 15.67GHz signal, which is then multiplied by six and amplified by a power amplifier to output a 94GHz signal. The receiving feed first generates a 15.69GHz signal, which is multiplied by six and used as the local oscillator signal. This signal is then mixed with the echo signal reflected from the target under test to obtain a 120MHz intermediate frequency (IF) signal. This IF signal is filtered, amplified, and then received by the vector network analyzer.
[0056] The three-port power divider consists of an input terminal, a first output terminal, and a second output terminal. A low-frequency signal generated at the output of the vector network analyzer is fed into the input of the three-port power divider. The first output of the three-port power divider is connected to the input of the transmitting feed, and the second output of the three-port power divider is connected to the input of the receiving feed, ensuring signal coherence between the two stations.
[0057] The transmitting feed consists of a first controlled frequency source, a frequency multiplier, a power amplifier, and a transmitting antenna, used to transmit measurement signals. The first output terminal of the power divider is connected to the input terminal of the first controlled frequency source to achieve the first frequency multiplication of the measurement signal. The output terminal of the first controlled frequency source is connected to the input terminal of the frequency multiplier to achieve the second frequency multiplication of the measurement signal. The output terminal of the frequency multiplier is connected to the input terminal of the power amplifier to increase the power of the measurement signal. The output terminal of the power amplifier is connected to the transmitting antenna to transmit the generated high-frequency measurement signal to the transmitting compact field.
[0058] The receiving feed includes a second controlled frequency source, a frequency multiplier, a mixer, a receiving antenna, a low-noise amplifier, an intermediate frequency (IF) filter circuit, and an IF amplifier circuit. The second output of the three-port power divider is connected to the input of the second controlled frequency source to achieve the first frequency multiplication of the measurement signal. The output of the second controlled frequency source is connected to the input of the frequency multiplier to achieve the second frequency multiplication of the measurement signal. The output of the frequency multiplier is connected to the local oscillator input of the mixer. The receiving antenna is used to receive the echo signal reflected from the receiving compaction area. The receiving antenna is connected to the input of the low-noise amplifier to increase the power of the echo signal. The output of the low-noise amplifier is connected to the RF input of the mixer to mix the echo signal generated by the target with the local oscillator signal to obtain the IF value. The IF output of the mixer is connected to the input of the IF filter circuit. The output of the IF filter circuit is connected to the input of the IF amplifier circuit. The output of the IF amplifier circuit is connected to the input of the vector network analyzer.
[0059] Furthermore, the transmitting and receiving antennas employ standard gain corrugated horn antennas as reference standard antennas. The corrugated horn improves its performance by slotting the inner wall of a standard horn. By selecting the corrugation form, feed characteristics with low cross-polarization and low sidelobes that meet the requirements of a compact field system can be obtained.
[0060] The control and data processing center controls the vector network analyzer to generate different frequencies and powers and rotates the target placement turntable, and processes the measurement data.
[0061] This invention also proposes a method for scaling down the RCS of a large-size target in an indoor compact field using a bistation method. The method employs a calibration body substitution method to measure the RCS and includes the following steps:
[0062] Step 101: After setting up an indoor compact field electric large-size target bistation RCS scaled-down test system, place the target to be tested bracket on the target placement turntable without placing the target to be tested, and obtain the indoor background signal when there is no target.
[0063] Step 102: Fix the calibration body onto the target bracket to be tested;
[0064] Step 103: Set the target bracket and target placement turntable to the desired state so that the calibration body is at the predetermined distance, azimuth angle and elevation angle;
[0065] Step 104: The control and data processing center controls the vector network analyzer to generate a low-frequency measurement signal. The low-frequency measurement signal is converted into a high-frequency, high-power measurement signal by the transmitting feed and transmitted to the transmitting compact field parabolic transmitting surface, which converts it into a quasi-plane wave that illuminates the calibration body. The calibration body reflects the measurement signal to the receiving compact field parabolic transmitting surface, thereby focusing the echo signal and receiving it by the receiving feed.
[0066] Step 105: The control and data processing center records the intermediate frequency signal containing the calibration matrix RCS information;
[0067] Step 106: Replace the calibration body with a scaled-down target model;
[0068] Step 107: The control and data processing center controls the vector network analyzer to generate a low-frequency measurement signal. The low-frequency measurement signal is converted into a high-frequency, high-power measurement signal by the transmitting feed and transmitted to the transmitting compact field parabolic transmitting surface, which converts it into a quasi-plane wave that illuminates the calibration body. The scaled target model reflects the measurement signal to the receiving compact field parabolic transmitting surface, thereby focusing the echo signal and receiving it by the receiving feed.
[0069] Step 108: The control and data processing center records the intermediate frequency signal containing the RCS information of the scaled-down target model;
[0070] Step 109: Change the relative positions of the transmitting and receiving compressed fields and the azimuth and elevation attitude angles of the scaled-down target under test, and repeat steps 107 and 108 to measure multiple sets of data. Using the known RCS from the calibration model and the intermediate frequency signal output from the receiving feed obtained from the calibration model, and the intermediate frequency signal output from the receiving feed obtained from the scaled-down target model, establish a mathematical model and calculate and process it to obtain the determined RCS value of the scaled-down target model under the test conditions.
[0071] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.
Claims
1. A dual-station RCS scaling test system for large-size targets in an indoor compact field, characterized in that, It includes a transmitter feed, a receiver feed, a transmitter compacted field parabolic reflector, a receiver compacted field parabolic reflector, a transmitter compacted field movable support, a receiver compacted field movable support, a target under test, a target placement turntable, a vector network analyzer, a three-port power divider, and a control and data processing center. The target under test includes two types: one is a calibration body, and the other is a scaled-down target model. The launch feed and the launch compaction field parabolic reflector form the launch compaction field. The launch feed is located at the focal point of the launch compaction field parabolic reflector and faces the center of the launch compaction field parabolic reflector. The launch compaction field is fixed on the launch compaction field movable support so that the indoor position of the launch compaction field can be moved according to experimental requirements. The receiving feed and the receiving compact field parabolic reflector form the receiving compact field. The receiving feed is located at the focal point of the receiving compact field parabolic reflector and faces the center of the receiving compact field parabolic reflector. The receiving compact field is fixed on the movable support of the transmitting compact field so that the indoor position of the receiving compact field can be moved according to experimental requirements. The launch compact field parabolic launch surface and the receiving compact field parabolic launch surface form a certain angle with the target placement turntable as the axis. This angle can be changed by moving the movable support of the launch compact field or the movable support of the receiving compact field to simulate different dual-station positions in actual scenarios. The three-port power divider consists of an input terminal, a first output terminal, and a second output terminal. The low-frequency signal generated by the vector network analyzer is fed into the input terminal of the three-port power divider. The first output terminal of the three-port power divider is connected to the input terminal of the transmitter feed, and the second output terminal of the three-port power divider is connected to the input terminal of the receiver feed, ensuring the signal coherence of the two stations.
2. The indoor compact field electric large-size target bistation RCS scaling test system according to claim 1, characterized in that, The common quiet zone formed by the launch compaction field and the receiving compaction field is not smaller than the size of the target to be measured.
3. The indoor compact field electric large-size target bistation RCS scaling test system according to claim 1, characterized in that, When the horizontal height of the transmitting and receiving compressed fields is fixed, the center of the parabolic reflector of the transmitting compressed field must be located on the same horizontal plane as the center of the parabolic reflector of the receiving compressed field. The height of this horizontal plane is the same as the height of the horizontal plane where the target is located.
4. The indoor compact field electric large-size target bistation RCS scaling test system according to claim 1, characterized in that, The scaled-down model is a complete replica of the full-size target system. It requires that the scaled-down size be a linear simulation of the full-size real target size, with identical electromagnetic conditions. The scaled-down size should be less than or equal to the size of the compacted field quiet zone in order to obtain the electromagnetic scattering characteristics of the real target.
5. The indoor compact field electric large-size target bistation RCS scaling test system according to claim 1, characterized in that, The parabolic reflector of the compressed field transforms the spherical wave radiated by the feed source into a plane wave at a relatively short distance and transmits it to the target under test, so as to form a plane wave illumination area (quiet zone) with an almost ideal amplitude and phase distribution in a limited space, thereby meeting the requirements of far-field testing.
6. The indoor compact field electric large-size target bistation RCS scaling test system according to claim 1, characterized in that, The receiving compressed field parabolic reflector transforms the plane wave radiated by the target under test into a spherical wave at a relatively short distance and transmits it to the receiving feed, completing the transformation from far-field conditions to near-field conditions on the test site within a limited space.
7. The indoor compact field electric large-size target dual-station RCS scaling test system according to claim 1, characterized in that, The transmitting feed includes a first controlled frequency source, a frequency multiplier, a power amplifier, and a transmitting antenna. The first output terminal of the three-port power divider is connected to the input terminal of the first controlled frequency source to achieve the first frequency multiplication of the measurement signal. The output terminal of the first controlled frequency source is connected to the input terminal of the frequency multiplier to achieve the second frequency multiplication of the measurement signal. The output terminal of the frequency multiplier is connected to the input terminal of the power amplifier to increase the power of the measurement signal. The output terminal of the power amplifier is connected to the transmitting antenna to transmit the generated high-frequency measurement signal to the transmitting compact field.
8. The indoor compact field electric large-size target bistation RCS scaling test system according to claim 1, characterized in that, The receiving feed includes a second controlled frequency source, a frequency multiplier, a mixer, a receiving antenna, a low-noise amplifier, an intermediate frequency (IF) filter circuit, and an IF amplifier circuit. The second output of the three-port power divider is connected to the input of the second controlled frequency source to achieve the first frequency multiplication of the measurement signal. The output of the second controlled frequency source is connected to the input of the frequency multiplier to achieve the second frequency multiplication of the measurement signal. The output of the frequency multiplier is connected to the local oscillator input of the mixer. The receiving antenna is used to receive the echo signal reflected from the receiving compaction area. The receiving antenna is connected to the input of the low-noise amplifier to increase the power of the echo signal. The output of the low-noise amplifier is connected to the RF input of the mixer to mix the echo signal generated by the target with the local oscillator signal to obtain the IF value. The IF output of the mixer is connected to the input of the IF filter circuit. The output of the IF filter circuit is connected to the input of the IF amplifier circuit. The output of the IF amplifier circuit is connected to the input of the vector network analyzer.
9. The indoor compact field electric large-size target bistation RCS scaling test system according to claim 7 or 8, characterized in that, The antenna is a standard gain corrugated horn antenna, with corrugated slots cut into the inner wall of a regular horn.
10. A method for bistatic RCS scaling test of large-size targets in an indoor compact field, characterized in that, Based on the indoor compact field electric large-size target bistation RCS scaling test system according to any one of claims 1-9, the RCS is measured using the calibration body substitution method, comprising the following steps: Step 101: After setting up an indoor compact field electric large-size target bistation RCS scaled-down test system, place the target to be tested bracket on the target placement turntable without placing the target to be tested, and obtain the indoor background signal when there is no target. Step 102: Fix the calibration body onto the target bracket to be tested; Step 103: Set the target bracket and target placement turntable to the desired state so that the calibration body is at the predetermined distance, azimuth angle and elevation angle; Step 104: The control and data processing center controls the vector network analyzer to generate a reference signal, which is converted into a high-frequency, high-power measurement signal by the transmitting feed and transmitted to the transmitting compact field parabolic surface. This signal is then converted into a quasi-plane wave and irradiated onto the target. The calibration body reflects the measurement signal to the receiving compact field parabolic surface. The measurement signal at this time serves as an echo signal, containing the target characteristic information of the calibration body. The receiving compact field parabolic surface focuses the echo signal, which is then received by the receiving feed. The intermediate frequency signal from the receiving feed is output to the vector network analyzer. Step 105: The control and data processing center records the intermediate frequency signal containing the target characteristic information of the calibration body; Step 106: Replace the calibration body with a scaled-down target model; Step 107: The control and data processing center controls the vector network analyzer to generate a reference signal, which is converted into a high-frequency, high-power measurement signal by the transmitting feed and transmitted to the transmitting compact field parabolic surface. This signal is then converted into a quasi-plane wave and irradiated onto the target under test. The scaled-down target model reflects the measurement signal to the receiving compact field parabolic surface. The measurement signal at this time serves as an echo signal and contains the target characteristic information of the calibration body. The receiving compact field parabolic surface focuses the echo signal and it is received by the receiving feed. The intermediate frequency signal from the receiving feed is output to the vector network analyzer. Step 108: The control and data processing center records the intermediate frequency signal containing the target characteristic information of the scaled-down target model; Step 109: Using the known RCS from the calibration body, the intermediate frequency signal output from the receiving feed obtained by measuring the calibration body, and the intermediate frequency signal output from the receiving feed obtained by measuring the scaled-down target model, calculate and process to obtain the RCS value of the scaled-down target model.