A self-concealing jamming method for pulse Doppler radar

Abstract

A self-concealing jamming method for pulse Doppler radar, S1. Measure the radar parameters, generate a jamming signal; S2. A series of accurate modulation jamming signals are formed near the real target echo through distance modulation, speed modulation, amplitude modulation; the present application perceives the environment threat target, aims at the PD system radar, destroys the constant false alarm signal detection mechanism of the radar by accurately controlling the frequency domain and time domain characteristics of the jamming signal, so that the radar cannot detect the target at all, delays the radar to discover the target, or gives the target indication information wrongly, and the signal environment received by the radar is completely normal, the operator of the radar cannot detect the existence of the jamming, and a novel self-concealing jamming effect is achieved.

Description

Technical Field

[0001] This invention relates to the field of radar countermeasures, and in particular to a self-concealing jamming method for pulse Doppler radar. Background Technology

[0002] Doppler radar is a type of radar that uses the Doppler effect to measure the radial velocity component of a target relative to the radar, or to extract targets with a specific radial velocity. If the radar transmits a pulse signal, it is called pulse-Doppler radar (PD radar). PD radar can be deployed at fixed ground stations or installed on moving platforms such as ships, aircraft, or satellites.

[0003] Existing PD radar jamming methods generally employ high-power noise suppression jamming and coherent jamming. Because the jamming signal is relatively strong, it easily exposes the location, distance, and angle of the jamming source. Since the jamming source and the target platform are essentially in the same location, this exposes the jamming source's positional information, making it vulnerable to attack. Furthermore, if the radar operator implements anti-jamming measures, the jamming effect will be significantly reduced or even rendered ineffective. For example, after using frequency hopping jamming, the radar's transmit power, operating frequency, repetition frequency, and receiver bandwidth will change. If the jamming parameters cannot keep pace with the radar parameters, the jamming will become ineffective. Frequency agility technology can also monitor the target environment and jamming characteristics in real time, automatically providing the radar with the optimal technical parameters based on the monitoring results, thereby reducing the jamming effect. If the radar uses sidelobe cancellation technology, it uses an omnidirectional or weakly directional antenna as an auxiliary antenna, and the gain is comparable to the sidelobe of the main antenna. Due to the path difference caused by the different spatial positions of each antenna, the interference signal received by each antenna has a fixed phase shift. The interference signals received by each auxiliary antenna are weighted and summed through an adaptive algorithm, and then subtracted from the interference signal received by the main antenna. The weights are adaptively adjusted to minimize the suppression power of the main channel, thereby canceling the interference and reducing the interference effect.

[0004] In addition, there is random Doppler frequency interference. This interference is a relay of the received radar signal. This signal does not contain the Doppler frequency of the real target, but rather randomly adds Doppler frequencies with different frequency shifts, generating several frequency shifts in the interference signal. This causes the speed tracking circuit of the velocity measurement system to simultaneously detect multiple false target Doppler frequencies, preventing it from accurately measuring the target's speed based on the Doppler filter output, resulting in detection and tracking errors. However, this random Doppler frequency shift of interference lacks precise Doppler modulation design. If the radar uses coherent accumulation, the interference is canceled out due to its non-coherence, significantly reducing the interference effect. Therefore, how to effectively interfere with / deceive enemy PD radar's detection of one's own position and speed has long been a difficult technical problem to solve.

[0005] For the reasons mentioned above, a self-concealing jamming method for pulse Doppler radar has been developed. Summary of the Invention

[0006] The purpose of this invention is to provide a self-concealing jamming method for pulse Doppler radar in order to solve the above-mentioned problems. By sensing the environmental threat target, and targeting PD system radar, the method precisely controls the frequency and time domain characteristics of the jamming signal to disrupt the radar's constant false alarm signal detection mechanism. This makes the radar completely unable to detect the target, delays the radar's detection of the target, or incorrectly provides target indication information. Moreover, the signal environment received by the radar is completely normal, and the radar operator cannot detect the existence of the jamming, thus achieving a novel jamming effect of concealing itself.

[0007] This invention provides a self-concealing jamming method for pulse Doppler radar, S1. Measuring radar parameters and generating jamming signals:

[0008] Measuring the pulse width of radar signals Signal bandwidth Pulse repetition frequency Pulse repetition period Signal amplitude Direction of incoming wave Estimate the distance between the target and the radar. Calculate and store the complex RCS of the self-defense target in advance, and use the obtained Doppler modulation parameters , , And the detected radar signal pulse descriptor, generating interference signal;

[0009] S2. By using range modulation, velocity modulation, and amplitude modulation, a series of precisely modulated interference signals are generated near the echo of the real target:

[0010] The number of pulses used for pulse Doppler processing is ,form One pulse Doppler processing channel, pulse repetition period is... The corresponding pulse repetition frequency is The target radial velocity is The radar signal wavelength is The target Doppler frequency is: The radar's Doppler range is Doppler resolution is Speed ​​resolution is ;

[0011] S21. Speed ​​modulation: By controlling the Doppler frequency of the interference pulse train. A series of false targets are created near the speed of the real target, with the speed difference between the false targets being... The velocity resolution cell width of the radar is estimated by measuring radar parameters. The Doppler frequency difference between the interference pulse and the target echo is:

[0012] ,in The number of false targets for speed;

[0013] S22. Distance modulation: by controlling the pulse delay A series of range-oriented false targets are created near the real target, with the distance difference between the false targets and the real target being... The range resolution cell width of the radar is determined by measuring the radar signal bandwidth. Based on estimation, the width of the radar's range resolution cell is... , To achieve the speed of light, and in order to create distance-based false targets both before and after the real target, the time delay of each interference pulse is:

[0014] ,

[0015] For pulses with negative time delay, in actual system implementation, they are delayed by one pulse repetition cycle:

[0016]

[0017] in This represents the distance to the false target.

[0018] S23. Amplitude Modulation: By controlling the amplitude of the false target, the controlled amplitude relationship between the real target and the false target is ensured in the radar velocity-range image. This causes the interference pulse to form a rectangular area or a honeycomb shape amplitude relationship in the radar range-Doppler image, thereby rendering the radar's constant false alarm detection and processing ineffective. Neither the real target nor the false target can be detected, thus achieving the target concealment effect.

[0019] The amplitude of each interference pulse is:

[0020] ,

[0021] in, The amplitude of the detected radar signal, The radar cross-section of the self-defense target. For the first Distance modulation, For the first Speed ​​modulation.

[0022] The beneficial effects are as follows: This invention proposes a novel jamming method that can conceal real targets. By sensing environmental threats to targets, and targeting PD-type radars, it precisely controls the frequency and time domain characteristics of the jamming signal to disrupt the radar's constant false alarm rate (CFAR) signal detection mechanism. This results in the radar being unable to detect the target at all, delaying the radar's target detection, or incorrectly providing target indication information. Furthermore, the signal environment received by the radar is completely normal, and the radar operator cannot detect the existence of the jamming, thus achieving a novel jamming effect that conceals itself. The parts not described in detail in this invention are commonly used existing technologies. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 It is a system composition block diagram;

[0025] Figure 2 This is a flowchart of the interference implementation process;

[0026] Figure 3 It is a diagram of interference signal modulation and generation;

[0027] Figure 4 It is a two-dimensional distance-velocity signal graph under interference-free conditions;

[0028] Figure 5 This is a two-dimensional distance signal diagram under interference-free conditions;

[0029] Figure 6 It is a two-dimensional velocity signal graph under interference-free conditions;

[0030] Figure 7 This is a graph showing the results of constant false alarm detection processing under interference-free conditions;

[0031] Figure 8 It is a two-dimensional signal diagram of range-velocity after superimposed interference;

[0032] Figure 9 This is a top view of the range-velocity two-dimensional signal after superimposed interference;

[0033] Figure 10 This is a distance-dimensional signal diagram after superimposed interference;

[0034] Figure 11 This is a velocity-dimensional signal diagram after superimposed interference;

[0035] Figure 12The result of constant false alarm rate (CFAR) detection with added interference is: target cannot be detected. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0037] System composition such as Figure 1 As shown, the system includes a receiving antenna, a transmitting antenna, a receiving front-end module, a frequency synthesizer module, a down-conversion module / up-conversion module, an AD / DA conversion module, an FPGA processing module, a control module, and a control platform. First, the receiving antenna receives the radar radiated signal. After down-conversion and AD processing sampling, the signal enters the FPGA processing module. Based on the measured radar parameters (radar carrier frequency, pulse width, repetition frequency, angle of arrival, signal amplitude, signal bandwidth) and control information, the echo signal is modulated to form an interference baseband signal. The interference baseband signal is then converted by DA, up-converted, and a power amplifier before being radiated towards the radar through the antenna, forming an interference signal.

[0038] The process of generating scrambling signals is as follows: Figure 2 As shown, the Doppler frequency is calculated based on the relative radial velocity and the radar signal carrier frequency. The modulation phase is calculated based on the radar signal carrier frequency, relative radial distance, and target complex RCS. The modulation amplitude is calculated based on the target's complex RCS and the radar signal amplitude. Then, using the obtained Doppler modulation parameters , , And the detected radar signal pulse descriptor, generating interference signal;

[0039] Interference signal pattern generation method as follows Figure 3 As shown, a series of precisely modulated interference signals are generated near the echo of the real target through range modulation, velocity modulation, and amplitude modulation.

[0040] For distance modulation, the pulse delay is controlled. A series of range-oriented false targets are created near the real target, with the distance difference between the false targets and the real target being... The range resolution cell width of the radar is estimated by measuring radar parameters. The time delay of each interference pulse is:

[0041]

[0042] For speed modulation, the Doppler frequency of the pulse train is controlled. A series of false targets are created near the speed of the real target, with the speed difference between the false targets being... The velocity resolution cell width of the radar is estimated by measuring radar parameters. The Doppler frequency difference between the interference pulse and the target echo is:

[0043]

[0044] For amplitude modulation, by controlling the amplitude of the false target, the amplitude relationship between the real target and the false target in the radar velocity-range image is guaranteed to satisfy the rectangular region and honeycomb shape, thereby making the radar's constant false alarm detection process ineffective. Neither the real target nor the false target can be detected, thus achieving the target concealment effect.

[0045] When no jamming signal is emitted, the radar processing results are as follows: Figures 4-7 As shown, after radar pulse compression and Doppler processing, the target echo forms a distinct peak, which appears as a nail shape in the radar's range-velocity matrix image. The radar uses constant false alarm rate (CFAR) detection technology to distinguish between the signal and noise output by the receiver while maintaining a constant false alarm probability to determine whether the target signal exists. The detection threshold is rapidly and adaptively adjusted according to changes in input noise. Under interference-free conditions, the radar can find the correct speed and range position of the target after CFAR detection processing.

[0046] After measuring radar parameters, the jammer modulates the signal in terms of velocity, range, and amplitude according to the aforementioned method, and transmits jamming signals. The target echo and jamming signal, after radar pulse compression and Doppler processing, form a series of regularly occurring peaks, creating rectangular or honeycomb-shaped images in the radar's range-velocity matrix. Because these precisely modulated jamming signals and the real target echo signals have very similar range, velocity, and amplitude, the constant false alarm rate (CFAR) detection threshold is raised. CFAR detection technology refers to the technique used by a radar system to distinguish between the receiver's output signal and noise to determine the presence of a target signal while maintaining a constant false alarm probability. To keep the false alarm probability constant, this threshold is rapidly and adaptively adjusted according to changes in input noise. The noise processing method varies depending on the noise distribution; therefore, CFAR detection technology includes two main parts: CFAR processing technology and target detection technology. CFAR processing technology includes fast threshold and slow threshold processing techniques, while target detection includes likelihood ratio detection, binary detection, sequential detection, and nonparametric detection. After being jammed by the technology proposed in this invention, the radar cannot detect the target's presence after CFAR processing. The radar processing result is as follows: Figures 8-12 As shown.

[0047] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A self-concealing jamming method for pulse Doppler radar, characterized in that: S1. Measure radar parameters and generate interference signals: Measuring the pulse width of radar signals Signal bandwidth Pulse repetition frequency Pulse repetition period Signal amplitude Direction of incoming wave Estimate the distance between the target and the radar. Calculate and store the complex RCS of the self-defense target in advance, and use the obtained Doppler modulation parameters , , And the detected radar signal pulse descriptor, generating interference signal; S2. By using range modulation, velocity modulation, and amplitude modulation, a series of precisely modulated interference signals are generated near the echo of the real target: The number of pulses used for pulse Doppler processing is ,form One pulse Doppler processing channel, pulse repetition period is... The corresponding pulse repetition frequency is The target radial velocity is The radar signal wavelength is The target Doppler frequency is: ; The radar's Doppler range is Doppler resolution is Speed ​​resolution is ; S21. Speed ​​modulation: By controlling the Doppler frequency of the interference pulse train. A series of false targets are created near the speed of the real target, with the speed difference between the false targets being... The velocity resolution cell width of the radar is estimated by measuring radar parameters. The Doppler frequency difference between the interference pulse and the target echo is: ,in The number of false targets for speed; S22. Distance modulation: by controlling the pulse delay A series of false targets are created near the real target in the range direction, and the distance difference between the false targets and the real target is... The range resolution cell width of the radar is determined by measuring the radar signal bandwidth. Based on estimation, the width of the radar's range resolution cell is... , To achieve the speed of light, and in order to create false targets both in front of and behind the real target, the time delay of each interference pulse is: ， For pulses with negative time delay, in actual system implementation, they are delayed by one pulse repetition cycle: ， in This represents the distance to the false target. S23. Amplitude Modulation: By controlling the amplitude of the false target, the controlled amplitude relationship between the real target and the false target is ensured in the radar velocity-range image. This causes the interference pulse to form a rectangular area or a honeycomb shape amplitude relationship in the radar range-Doppler image, thereby rendering the radar's constant false alarm detection and processing ineffective. Neither the real target nor the false target can be detected, thus achieving the target concealment effect. The amplitude of each interference pulse is: ， in, The amplitude of the detected radar signal, The radar cross-section of the self-defense target. For the first Distance modulation, For the first Speed ​​modulation.

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