Radar target active stealth test system based on active cancellation and test method

Abstract

The application discloses a radar target active stealth test system and test method based on active cancellation, and relates to the electromagnetic field and microwave technology field.The technical scheme points of the application are as follows: the test system and test method for reducing the target RCS by actively emitting electromagnetic wave signals to cancel the scattered echo by using the retransmission type amplitude modulation phase shift active cancellation circuit.The active stealth system based on active cancellation comprises a radar signal frame receiving antenna, a retransmission type active cancellation circuit module, a control system program and a cancellation parameter library, and a cancellation wave signal emitting antenna.The target RCS is reduced under the condition of a specific frequency after the vector synthesis of the scattered echo of the target and the cancellation wave signal generated by the cancellation antenna, and the active stealth effect is achieved.The test system of the application is suitable for the cancellation of various radar signal wave forms including continuous wave and step frequency wave, has high cancellation precision, and the hardware equipment and test method involved are simple and easy to realize.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic field and microwave technology, and more specifically, to a radar target active stealth test system and test method based on active cancellation. Background Technology

[0002] A significant reduction in radar cross-section (RCS) is a major characteristic of stealth aircraft. However, with the continuous development of stealth technology, traditional passive stealth techniques, such as shape design and radar-absorbing coatings, are no longer sufficient to meet low-frequency stealth requirements, necessitating the consideration of other technologies to compensate for these deficiencies. Active cancellation technology, a key alternative in active stealth methods, actively emits cancelling electromagnetic wave signals to counteract the target's scattered echoes, reducing the RCS and enabling stealth across any frequency band.

[0003] While the technology itself is not complex in theoretical research, achieving effective signal cancellation in practical engineering presents numerous key challenges. These include effective detection of enemy radar signals, efficient generation of equal-amplitude, phase-inverse cancellation signals, time synchronization of signal synthesis, suppression of environmental noise, and accuracy in reducing the target's radar cross-section. These issues make active cancellation systems complex and difficult to implement. Therefore, establishing a simple and feasible active stealth system to conduct cancellation tests on aircraft targets and verify the system's cancellation effectiveness is a crucial technical problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide a radar target active stealth test system and test method based on active cancellation. The test of this system is based on a microwave anechoic chamber platform, which has the characteristics of low environmental noise and fast and accurate RCS measurement system.

[0005] The above-mentioned technical objective of the present invention is achieved through the following technical solution: an active radar target stealth test system based on active cancellation, comprising a receiving antenna, a transmitting antenna, an RCS test platform, a control system, a parameter library, and a repeater-type active cancellation circuit module; the control system simultaneously establishes communication with the repeater-type active cancellation circuit module and the RCS test platform; the parameter library is embedded in the control system;

[0006] The RCS test platform is used to simulate an enemy radar system. The transmitting and receiving antennas of the RCS test platform serve as the transmitting and receiving ends of the enemy radar system, and can measure the RCS of targets at different frequencies in real time.

[0007] The RCS platform is a microwave anechoic chamber testing platform.

[0008] The control system is used to issue amplitude and phase control commands to the circuit module, acquire the angle information of the turntable target, and read and process the RCS data measured by the RCS test platform in real time.

[0009] The parameter library is used to store the optimal cancellation amplitude phase command for the target at different angles;

[0010] The forwarding active cancellation circuit module is used to change the frequency response of the circuit and precisely control the amplitude and phase of different frequency components of the output signal.

[0011] The present invention is further configured such that both the receiving antenna and the transmitting antenna of the RCS test platform are low-scattering antennas.

[0012] The present invention is further configured such that: the forwarding active cancellation circuit module includes a low-noise amplifier, a digitally controlled analog phase shifter and a digital attenuator; the input signal passes through the low-noise amplifier and the digitally controlled analog phase shifter in sequence, and finally the amplitude and phase of different frequency components of the output signal are output through the digital attenuator; the control system is configured to parse instructions and control the digitally controlled analog phase shifter and the digital attenuator by an FPGA chip.

[0013] This invention also provides a method for measuring the RCS reduction of a radar target based on an active cancellation radar target stealth test system, specifically including the following steps:

[0014] S1: The original RCS values ​​of the target at each angle under the condition that the cancellation system is not working;

[0015] S2: The system automatically calibrates and generates a cancellation parameter library;

[0016] S3: Measure the RCS size after target cancellation.

[0017] The present invention is further configured such that the specific steps of S2 are as follows:

[0018] S2-1: At a specific angle of the turntable, the cancellation system is activated and receives the radar incoming wave signal. According to the amplitude and phase parameter instructions, the circuit frequency response is adjusted to generate a cancellation electromagnetic wave signal to cancel the target echo.

[0019] S2-2: The computer control program determines the optimal amplitude and phase cancellation parameters based on the RCS value obtained in real time by the measurement system, and stores them as the optimal cancellation parameters for the corresponding angle in the target parameter library.

[0020] S2-3: Repeat the operation of S2-2 until all preset angle data have been collected, forming a complete aircraft target cancellation parameter library.

[0021] The present invention is further configured such that the specific steps of S3 are as follows:

[0022] S3-1: The turntable restarts to make the aircraft model rotate continuously. The frame receiving antenna receives incoming wave signals from different azimuth angles. The computer control program extracts the corresponding optimal cancellation data from the parameter library and sends it to the repeater cancellation circuit to generate cancellation electromagnetic wave signals that are superimposed on the target echo vector. Echo cancellation is achieved at all angles while the target is rotating.

[0023] S3-2: By comparing the RCS with the initially acquired RCS, the RCS reduction effect after target cancellation can be obtained.

[0024] In summary, the present invention has the following beneficial effects:

[0025] 1. This system effectively utilizes the microwave anechoic chamber RCS testing system. The pulse signal from the vector network analyzer's RF signal source, after being modulated by the system, serves as the enemy radar signal. The testing method is simple and highly feasible.

[0026] 2. The system adopts a forwarding active cancellation circuit structure, which ensures that the frequency component of the cancellation wave signal generated by amplitude modulation and phase shifting is consistent with the incoming wave signal. For different types of radar signal waveforms, the cancellation system can achieve good cancellation effect under the preset frequency conditions.

[0027] 3. The target cancellation parameter library can be obtained offline and automatically generated, which effectively solves the problems of large computational load and time-consuming and laborious manual testing in the cancellation system;

[0028] 4. The system's functionality can be extended and expanded. By changing the hardware configuration of the cancellation circuit, RCS cancellation and reduction can be achieved for electromagnetic wave signals of different frequency bands. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the active stealth radar target test system based on active cancellation in Embodiment 1 of the present invention.

[0030] Figure 2 This is a schematic diagram of the forwarding cancellation circuit structure in Embodiment 1 of the present invention;

[0031] Figure 3 This is a diagram of the computer control system interface in Embodiment 1 of the present invention;

[0032] Figure 4 This is a flowchart of the system calibration mode in Embodiment 1 of the present invention;

[0033] Figure 5 This is a flowchart of the system cancellation mode in Embodiment 2 of the present invention;

[0034] Figure 6 This is a schematic diagram of the compressed field anechoic chamber test in Embodiment 2 of the present invention;

[0035] Figure 7 This is a comparison diagram of RCS measurement before and after target cancellation of an aircraft in Embodiment 2 of the present invention. Detailed Implementation

[0036] The following is in conjunction with the appendix Figure 1-7 The present invention will be described in further detail below.

[0037] Example 1: An experimental system for active radar target stealth based on active cancellation, such as... Figures 1 to 3 As shown, it includes an RCS test platform, a control system, a parameter library, and a forwarding active cancellation circuit module;

[0038] The RCS test platform is used to simulate an enemy radar system. The transmitting and receiving antennas of the test platform serve as the transmitting and receiving ends of the enemy radar system. In this embodiment, both the transmitting and receiving antennas are low-scatter antennas to reduce the impact on the target echo and enable real-time measurement of the target RCS at different frequencies. This embodiment preferably uses a microwave anechoic chamber test platform, which provides two types of RCS test signals: a single-frequency continuous wave and a stepped-frequency wave, representing continuous wave radar signals and stepped-frequency radar signals, respectively. This embodiment can achieve considerable cancellation effects for different signal waveforms.

[0039] The repeater-type active cancellation circuit module mainly consists of a low-noise amplifier, a digitally controlled analog phase shifter, and a digital attenuator. Its structural schematic diagram is shown below. Figure 2 The specific implementation method of the circuit is as follows: the computer control program issues instructions, the FPGA chip parses the instructions and controls the output of the digital control analog phase shifter and digital attenuator, changes the frequency response of the circuit, and precisely controls the amplitude and phase of different frequency components of the output signal.

[0040] The control system and parameter library are the core of this experimental system. The control system establishes communication with the repeater active cancellation circuit module and the RCS test platform. Its main functions include issuing amplitude and phase control commands to the repeater active cancellation circuit module, acquiring the angle information of the turntable target, and reading and processing the RCS data measured by the test platform in real time. The parameter library is embedded in the control system and is used to store the optimal cancellation amplitude and phase commands for the target at different angles.

[0041] To achieve the above functions, the system control program in this embodiment is as follows: Figure 3 As shown, the control program has four operating modes: calibration mode, cancellation mode, single-point mode, and phase scan mode. In calibration mode, the system quickly iterates through the issued commands, then compares them with the real-time acquired target RCS data, searches for the optimal cancellation parameters, saves them, and continuously repeats the calibration process to ultimately form a complete parameter library. The specific process is as follows: Figure 4As shown; in cancellation mode, the system realizes echo cancellation function when the target is rotating. The system synchronously acquires the turntable angle information, reads data from the parameter library and issues commands to control the cancellation circuit to generate a cancellation signal, thus completing the cancellation test when the target is rotating; in single-point mode, by inputting the specified attenuation and phase shift values, the corresponding RCS reduction value can be observed. The reset function sets the attenuation and phase shift states of the circuit module to the initial state (maximum attenuation, phase shift of 0); in limit scan mode, the main function is to fix the attenuation value and observe the influence of the phase shift parameter on the measurement effect, and display the cancellation state under different phase shift angles in the chart on the right, so as to accurately find the optimal cancellation phase shift parameter under specific amplitude conditions.

[0042] Example 2: Test method for radar target active stealth test system based on active cancellation. A schematic diagram of the compact field anechoic chamber test structure is shown below. Figure 6 As shown, once the active cancellation system is built and the cancellation database is collected, the cancelled RCS data can be tested. The specific testing method includes the following steps:

[0043] S1: Test the background noise of the empty room and temporarily store it to obtain the isolation error σ. emp The data for all test targets will be automatically subtracted from it;

[0044] S2: The actual RCS of a known standard calibration sphere can be obtained through theoretical calculation, denoted as σ. sph The echo power of the actual calibration sphere was tested, and its S21 value was measured to be S21. sph ;

[0045] S3: The aircraft target is placed on the turntable and rotated (the cancellation system is off and not working), and the initial echo S21 is measured. tar ;

[0046] S4: Based on the fact that the logarithmic difference between the received power measured by the calibration sphere and the target is equal to the difference in their RCS, the original RCS of the target is calculated as follows:

[0047] σ tar =S21 tar -S21 sph +σ sph ;

[0048] S5: The aircraft target rotates again, the cancellation system is activated, and the control system is in cancellation mode. At this time, the turntable rotates while the cancellation signal is sent synchronously, resulting in the cancelled signal S21. cancel The calculated RCS value after cancellation is:

[0049] σ cancel =S21 cancel -S21 sph +σsph .

[0050] Furthermore, by comparing the RCS difference between the active cancellation system before and after power-on, the cancellation reduction value can be obtained. Figure 7 The figure shows a comparison of the RCS test results of a stealth aircraft model before and after the cancellation system is activated. The figure shows that the system of the present invention has a significant effect on reducing the RCS of the stealth aircraft target.

[0051] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. An active stealth test system for radar targets based on active cancellation, characterized by: It includes a receiving antenna, a transmitting antenna, an RCS test platform, a control system, a parameter library, and a repeater-type active cancellation circuit module; the control system simultaneously establishes communication with the repeater-type active cancellation circuit module and the RCS test platform; the parameter library is embedded in the control system; The RCS test platform is used to simulate an enemy radar system. The transmitting and receiving antennas of the RCS test platform serve as the transmitting and receiving ends of the enemy radar system, and can measure the RCS of targets at different frequencies in real time. The RCS test platform is a microwave anechoic chamber test platform; The control system is used to issue amplitude and phase control commands to the circuit module, acquire the angle information of the turntable target, and read and process the RCS data measured by the RCS test platform in real time. The parameter library is used to store the optimal cancellation amplitude phase command for the target at different angles; The forwarding active cancellation circuit module is used to change the frequency response of the circuit and precisely control the amplitude and phase of different frequency components of the output signal. The forwarding active cancellation circuit module includes a low-noise amplifier, a digitally controlled analog phase shifter, and a digital attenuator. The input signal passes through the low-noise amplifier and the digitally controlled analog phase shifter in sequence, and finally the amplitude and phase of different frequency components of the output signal are output through the digital attenuator. The control system is controlled by the FPGA chip to parse instructions and control the digitally controlled analog phase shifter and the digital attenuator.

2. The radar target active stealth test system based on active cancellation according to claim 1, characterized in that: Both the receiving and transmitting antennas of the RCS test platform are low-scatter antennas.

3. The method for measuring the RCS reduction of a radar target based on active cancellation radar target active stealth test system according to any one of claims 1-2, characterized in that: Specifically, the following steps are included: S1: The original RCS values ​​of the target at each angle under the condition that the cancellation system is not working; S2: The system automatically calibrates and generates a cancellation parameter library; S3: Measure the RCS size after target cancellation.

4. The method according to claim 3, characterized in that: The specific steps of S2 are as follows: S2-1: At a specific angle of the turntable, the cancellation system is activated and receives the radar incoming wave signal. According to the amplitude and phase parameter instructions, the circuit frequency response is adjusted to generate a cancellation electromagnetic wave signal to cancel the target echo. S2-2: The computer control program determines the optimal amplitude and phase cancellation parameters based on the RCS value obtained in real time by the measurement system, and stores them as the optimal cancellation parameters for the corresponding angle in the target parameter library. S2-3: Repeat the operation of S2-2 until all preset angle data have been collected, forming a complete aircraft target cancellation parameter library.

5. The method according to claim 3, characterized in that: The specific steps of S3 are as follows: S3-1: The turntable restarts to make the aircraft model rotate continuously. The receiving antenna receives incoming wave signals from different azimuth angles. The computer control program extracts the corresponding optimal cancellation data from the parameter library and sends it to the repeater cancellation circuit to generate cancellation electromagnetic wave signals that are superimposed on the target echo vector. Echo cancellation is achieved at all angles while the target is rotating. S3-2: By comparing the RCS with the initially acquired RCS, the RCS reduction effect after the aircraft target cancellation can be obtained.

Images