Coherent comb spectrum suppression interference method

Abstract

The invention discloses a coherent comb spectrum suppression interference method, and relates to the field of electronic countermeasures. The method comprises the following steps: receiving a radar signal, and converting the radar signal into a digital IQ signal; a plurality of coherent suppression interference modules are used for carrying out parallel modulation processing on the digital IQ signals in a digital domain, each module independently carries out modulation, and I-path signals and Q-path signals output by all the modules are added to generate coherent comb spectrum suppression interference signals, the modulation processing comprises the following steps: performing Doppler frequency modulation on the signal after amplitude modulation; performing Doppler noise modulation on the signal after Doppler frequency modulation; the modulated signal is converted into an analog signal, and the analog signal is radiated to a radar after up-conversion and amplification; wherein the coherent comb spectrum suppression interference signal is used for suppressing a real target signal at a radar receiving end. The method has the advantages of high coherence, quick response and adaptive adjustment, real target signals can be effectively submerged, and the interference effect is improved.

Description

Technical Field

[0001] This invention relates to a coherent comb spectrum suppression interference method, belonging to the field of electronic warfare simulation technology. Background Technology

[0002] With the continuous advancement of electronic and signal processing technologies, the electronic interference environment faced by monopulse radar and imaging radar is becoming increasingly complex. How radar operates in complex electromagnetic environments has become a key indicator for measuring radar anti-jamming capabilities. Constructing a well-functioning coherent interference countermeasure environment is one of the common methods for testing equipment capabilities.

[0003] Current coherent jamming techniques mainly employ methods such as transmitting false target signals that are coherent with the target echo to cause the radar to generate incorrect range information, changing the frequency of the transmitted jamming signal to cause the radar to measure the wrong target velocity, or using jamming signals to deceive the radar in terms of angle, causing the radar to deviate in its angle measurement of the target.

[0004] However, with the improvement of radar anti-jamming capabilities, current coherent jamming techniques are difficult to effectively interfere with radars after anti-jamming measures are taken. In order to ensure an effective countermeasure effect during the test, it is necessary to generate multi-dimensional and realistic false targets or completely submerge the target in noise, which is very difficult.

[0005] Comb-spectrum jamming technology can generate highly coherent narrowband jamming signals at multiple frequency points, but existing technologies suffer from low coherence and slow response, failing to effectively suppress radar. Especially when facing broadband radar signals, it is necessary to generate multiple coherent narrowband jamming signals to cover the entire radar signal bandwidth. Therefore, a technology capable of rapidly generating highly coherent comb-spectrum jamming signals is needed. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the defects of the prior art and propose a coherent comb spectrum jamming method. Through multi-module parallel modulation processing in the digital domain, a high coherent comb spectrum jamming signal is generated, which significantly improves the jamming effect on radar, thereby solving the problems of low coherence of noise jamming signals and poor jamming effect in the prior art.

[0007] To solve the above-mentioned technical problems, the present invention is implemented using the following technical solution.

[0008] In a first aspect, the present invention discloses a method for suppressing interference using a coherent comb spectrum, comprising: Receive radar signals and convert the radar signals into digital IQ signals; In the digital domain, multiple coherent interference suppression modules are used to perform parallel modulation processing on the digital IQ signal. Each module modulates independently, and the I-channel and Q-channel signals output from all modules are summed to generate a coherent comb spectrum interference suppression signal. The modulation processing includes: Amplitude modulation is performed on the digital IQ signal; Doppler frequency modulation is applied to the amplitude-modulated signal. Doppler noise modulation is applied to the signal modulated by Doppler frequency. The modulated signal is converted into an analog signal, and then radiated to the radar after up-conversion and amplification; The coherent comb spectrum suppression interference signal is used to suppress the real target signal at the radar receiver.

[0009] Furthermore, the amplitude modulation is achieved through complex multiplication, the Doppler frequency modulation is achieved through complex multiplication of the Doppler frequency offset signal generated by the DDS, and the Doppler noise modulation is achieved through complex multiplication of the noise modulation signal, wherein the frequency of the noise modulation signal varies randomly within a preset modulation bandwidth range, and the modulation frequency is 1 / 10 of the modulation bandwidth.

[0010] Furthermore, it also includes pre-reconnaissance of radar signals to obtain parameters such as signal bandwidth, pulse width, repetition period, and intra-pulse modulation characteristics, and adjust the modulation parameters accordingly.

[0011] Furthermore, prior to the modulation process, the radar signal is pre-reconnaissance to obtain radar signal parameters, and the modulation process parameters are adjusted according to the parameters. The radar signal parameters include signal bandwidth, pulse width, repetition period, and intra-pulse modulation characteristics.

[0012] Furthermore, the Doppler frequency offset of each coherent jamming module is calculated based on the radar signal bandwidth obtained from pre-reconnaissance. The Doppler frequency offset interval is the radar signal bandwidth divided by the number of coherent jamming modules minus one.

[0013] Furthermore, the number of the plurality of coherent suppression interference modules is 16, and each module is set with a different Doppler frequency offset.

[0014] Furthermore, the Doppler frequency offsets are -37500kHz, -32500kHz, -27500kHz, -22500kHz, -17500kHz, -12500kHz, -7500kHz, -2500kHz, 2500kHz, 7500kHz, 12500kHz, 17500kHz, 22500kHz, 27500kHz, 32500kHz, and 37500kHz.

[0015] Furthermore, the generation and radiation of the interference signal must be completed within the range gate of the radar, and the interference response time must be less than the duration of the radar range gate to ensure the interference effect.

[0016] Secondly, the present invention also provides a coherent comb spectrum suppression interference system, including a receiving unit, a digital signal processing unit, and a transmitting unit, for implementing the above-mentioned method.

[0017] The effective effects achieved by this invention are as follows: 1. This invention controls the amplitude, Doppler frequency offset, Doppler noise bandwidth, and other parameters of multiple coherent suppression jamming modules based on the radar operating signal, thereby generating multiple narrowband coherent jamming signals at different frequency points. In other words, by performing parallel modulation of multiple modules in the digital domain, a high-coherence comb spectrum jamming signal is generated, which effectively floods the real target signal at multiple frequency points, resulting in good jamming effect.

[0018] 2. Enhance the targeting and adaptability of jamming through pre-reconnaissance and adaptive parameter adjustment; 3. The system has a fast response speed, and the jamming signal can accurately appear within the radar range gate, significantly improving the jamming success rate. Attached Figure Description

[0019] Figure 1 Schematic diagram illustrating the principle of interference suppression in coherent comb spectrum; Figure 2 Diagram showing the interface settings for suppressing interference signals using a coherent comb spectrum; Figure 3 The spectrum diagram of the interference signal suppressed by the coherent comb spectrum; Figure 4 The simulation diagram shows the effect of coherent comb spectrum in suppressing interference. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0021] Example 1: Interference suppression method using coherent comb spectra: This embodiment provides a method for suppressing interference using a coherent comb spectrum, such as... Figure 1 As shown, it includes the following steps: 1. Receive radar signals, and obtain digital IQ signals through down-conversion and analog-to-digital conversion (AD); 2. Parallel modulation processing of the IQ signal is performed using 16 coherent interference suppression modules in the digital domain: Each module performs amplitude modulation: the IQ signal is multiplied by the amplitude control signal, and the amplitude of the I signal is set to 3750. Doppler frequency modulation is performed on each module: the amplitude-modulated signal is multiplied by the Doppler frequency offset signal generated by the DDS, the modulation frequency is set to 8kHz, and the Doppler frequency offset of each module is set to -37500kHz, -32500kHz, ..., 37500kHz respectively; Each module performs Doppler noise modulation: the signal modulated by the Doppler frequency is multiplied by the noise modulation signal, the modulation bandwidth is set to 8000kHz, the noise frequency varies randomly within the bandwidth, and the modulation frequency is 1 / 10 of the modulation bandwidth. 3. Add the I-channel and Q-channel signals output by all modules separately to obtain the composite signal; 4. The synthesized signal is converted from digital to analog (DA), up-converted, and amplified before being radiated to the radar.

[0022] The modulation parameters are set through a software interface, such as... Figure 2 As shown. The spectrum of the generated interference signal is as follows. Figure 3 As shown, at the radar receiver, the real target signal is overwhelmed by multiple narrowband noise signals, and the interference effect simulation is as follows. Figure 4 As shown.

[0023] If coherent comb spectrum jamming technology is required, the jamming system receives radar signals, performs down-conversion and AD conversion, and then performs rapid processing on the target signal in the digital domain according to certain rules, such as copying, amplitude modulation, Doppler frequency modulation, and Doppler noise modulation. Then, it performs DA conversion, and then performs up-conversion, filtering, and amplification to release jamming to the radar. At the radar receiver, multiple high-coherence narrowband noise jamming signals at different frequency points are formed, so that the real target signal is submerged in the noise signal, thus creating a jamming effect. The coherent interference technology is achieved by controlling multiple parameters of multiple phase-coherent interference suppression generation modules in the FPGA. The specific generation method includes the following steps: Step 1), the radar signal is sent to the digital signal processing unit for digital down-conversion after passing through the interference receiving frequency conversion unit; Step 2) After digital down-conversion, the IQ signal enters the coherent suppression interference generation module and then enters multiple independent modulation modules for amplitude modulation. The modulation method is to multiply the IQ signal with the input IQ amplitude to complete the amplitude-phase modulation and output it to the Doppler modulation module. Step 3) The Doppler modulation module directly receives the Doppler frequency offset value, which is independent of the input RF frequency. Based on the received Doppler frequency offset, the DDS is controlled to generate an IQ signal with a frequency equal to the Doppler frequency offset. Then, the IQ signal generated by the DDS is multiplied by the IQ signal obtained after amplitude-phase modulation and output to the Doppler noise modulation module. Step 4) After Doppler frequency offset modulation, according to the received Doppler noise modulation bandwidth and tuning frequency, the frequency is controlled to change randomly within the modulation bandwidth according to the modulation frequency rhythm. After a certain period of time, the output frequency can cover the entire modulation bandwidth. It is then multiplied by the IQ signal obtained after the Doppler modulation module. The result of the multiplication is the output signal of the single coherent suppression interference signal. Step 5): Each independent coherent suppression interference modulation module modulates according to different amplitudes, Doppler frequency offsets and Doppler noise. Then, the I-channel and Q-channel signals output by all independent coherent suppression interference modulation modules are added together to obtain the output of the entire coherent suppression interference module. Step 6) The IQ data output in Step 5) is digitally up-converted and sent to the RF up-conversion unit and amplification module for frequency conversion, filtering and signal amplification, and then radiated to the radar via the transmitting antenna as a coherent interference signal.

[0024] The modulation of the signal according to a certain rule is to modulate the interference signal according to the radar working signal (typically a linear frequency modulated signal) measured by pre-reconnaissance, mainly based on the signal bandwidth, pulse width, repetition frequency, intra-pulse characteristics, etc.

[0025] The coherent comb spectrum suppression interference is generated by controlling the amplitude, Doppler frequency offset, Doppler noise bandwidth, and other parameters of multiple coherent suppression interference modules according to the radar operating signal, thereby generating multiple narrowband coherent interference signals at different frequency points.

[0026] The interference system must have a short interference response time, and the interference signal must be controlled to appear within the range gate of the radar in order for the interference to achieve a good effect.

[0027] This embodiment provides a coherent comb spectrum suppression interference signal generation technique, the specific generation method including the following steps: Step 1), the radar signal is sent to the digital signal processing unit for digital down-conversion after passing through the interference receiving frequency conversion unit; Step 2): The IQ signal after digital down-conversion enters the coherent comb spectrum interference suppression generation module, and simultaneously enters 16 independent modulation modules. The implementation principle is as follows: Figure 1 As shown; Step 3): Using the software interface, generate 16 narrowband signals. Set the amplitude (I-channel) of each signal to 3750 kHz, the modulation frequency to 8 kHz, and the modulation bandwidth to 8000 kHz. Set the Doppler frequency offsets of the 1st to 16th signals to -37500 kHz, -32500 kHz, -27500 kHz, -22500 kHz, -17500 kHz, -12500 kHz, -7500 kHz, -2500 kHz, 2500 kHz, 7500 kHz, 12500 kHz, 17500 kHz, 22500 kHz, 27500 kHz, 32500 kHz, and 37500 kHz, respectively. Set all other parameters to 0. The settings interface is shown below. Figure 2 As shown; Step 4): Each independent coherent suppression interference modulation module is modulated according to different amplitudes, Doppler frequency offsets, Doppler noise bandwidths, and modulation frequencies. Then, the I-channel and Q-channel signals output by all independent coherent suppression interference modulation modules are added together to obtain the output of the entire coherent comb spectrum suppression interference module. Step 5), the signal generated in step 4) is digitally up-converted and then sent to the RF up-conversion unit and amplification module for frequency conversion, filtering, and signal amplification. It is then transmitted to the radar via the transmitting antenna as a one-dimensional range-image static ship decoy interference signal. The signal spectrum is as follows: Figure 3 As shown.

[0028] In this embodiment, when the radar receives the target signal, the true target signal at the radar receiver is submerged in multiple narrowband noise signals, creating an interference effect, such as... Figure 4 As shown; The value of amplitude I is the amplitude value of the quantized digital signal, used to characterize the magnitude of the digital signal.

[0029] The coherent comb-shaped spectrum suppression jamming method provided by this invention is based on the following core principle: by deploying multiple independent coherent suppression jamming modules in parallel in the digital domain, the intercepted radar signal is subjected to cascaded modulation processing, thereby rapidly generating multiple narrowband noise jamming signals with high coherence characteristics and a comb-shaped distribution in the frequency domain. This ultimately results in a spectrum suppression effect on the real target signal at the radar receiver. Its technical principle can be broken down into the following levels: 1. The generation principle of comb-spectrum interference signal: Traditional jamming suppression typically generates broadband noise within a single frequency band, which is easily suppressed by radar filtering or signal processing techniques. This invention employs a "comb spectrum" strategy, dividing the radar signal bandwidth into multiple sub-bands and generating a highly coherent narrowband noise jamming signal in parallel within each sub-band. These narrowband signals are evenly spaced or distributed as needed in the frequency domain, resembling "comb teeth," collectively covering the radar's operating bandwidth. This discretized, multi-frequency jamming method more effectively counters radar's frequency domain filtering, pulse compression, and other anti-jamming measures, improving the concealment and uniformity of the jamming signal.

[0030] 2. Parallel modulation and signal synthesis principles: To achieve fast response and high phase coherence, this invention integrates multiple identical phase coherence suppression interference modules within a digital signal processing unit (such as an FPGA). Each module independently receives the same digital IQ signal and executes three core modulation operations in parallel according to preset parameters: Amplitude modulation: By multiplying the input IQ signal with the amplitude control signal, precise control of the interference signal strength is achieved, ensuring that each "comb tooth" has the desired power level to adapt to the target suppression requirements of different distances and radar cross-sections.

[0031] Doppler frequency modulation: Direct digital frequency synthesis (DDS) technology is used to generate a specific Doppler frequency offset signal independent of the radar carrier frequency, and then multiplying it with the amplitude-modulated signal. This causes a preset shift in the center frequency of the interference signal output by each module, thus forming a discrete "comb" distribution in the frequency domain. The difference in frequency offset between each module determines the spacing and coverage of the comb spectrum.

[0032] Doppler noise modulation: Based on the frequency-shifted signal, it is further multiplied with a bandwidth-limited, randomly varying frequency noise modulation signal. The frequency of this noise modulation signal randomly jumps within a set bandwidth, and its average modulation rate (e.g., 1 / 10 of the bandwidth) ensures the naturalness and time-varying nature of the noise characteristics. This results in a narrowband interference signal that not only has a fixed center frequency offset but also possesses subtle frequency fluctuations similar to real target or environmental echoes, enhancing the realism of the interference and the difficulty of radar identification.

[0033] After all modules are modulated, their output I-channel and Q-channel signals are synchronously added together. This synthesis process is completed in the digital domain, ensuring the phase coherence of the signals, and ultimately outputting a composite coherent comb spectrum interference signal containing multiple narrowband noise components.

[0034] 3. Parameter Adaptation and Fast Response Principles: The effectiveness of jamming is highly dependent on real-time matching of radar signals. Therefore, this method introduces a pre-reconnaissance stage before modulation processing: the system first analyzes the intercepted radar signal, quickly extracting key parameters such as signal bandwidth, pulse width, pulse repetition period, and intra-pulse modulation characteristics. Based on these parameters, the system automatically calculates and sets the key parameters of each modulation module, for example: Based on the radar signal bandwidth and the number of modules, the Doppler frequency offset of each module is dynamically allocated to ensure that the comb spectrum can uniformly cover the entire threat bandwidth.

[0035] Adjust the noise modulation bandwidth to match the processing bandwidth of the radar signal and optimize the distribution of interference energy.

[0036] The entire processing flow—from signal reception, digital down-conversion, parallel modulation, signal synthesis to digital-to-analog conversion and RF transmission—is rigorously designed to be completed within an extremely short timeframe. A key timing constraint is that the total jamming response time must be less than the duration of the radar range gate. This means that the jamming signal can reach the radar receiver within the same time window in which the radar expects to receive the echo from the real target, thus achieving "same-gate" suppression and significantly improving the timeliness and effectiveness of the jamming.

[0037] 4. System Implementation and Effect Principles: In terms of hardware, the above principles are implemented through a dedicated system: the receiving unit performs the conversion from radio frequency to digital signals; the digital signal processing unit, based on an FPGA or similar high-performance processor, carries multiple parallel modulation modules and executes the core algorithm; the transmitting unit reconstructs the generated digital interference signals into analog radio frequency signals and radiates them. The system uses a software interface for parameter configuration and monitoring, such as... Figure 2 As shown, operators are allowed to flexibly set the number of teeth, amplitude, frequency offset, and noise characteristics of the comb spectrum.

[0038] Ultimately, as Figure 3 and Figure 4 As shown, at the radar receiver, multiple narrowband noise "tooth" patterns appear in the frequency domain that overlap with the spectrum of the real target signal. These highly coherent noise signals overwhelm or severely distort the echo characteristics of the real target in terms of energy, making it impossible for the radar to correctly detect and identify the target in terms of range, velocity, or even angle, thereby achieving the purpose of effectively suppressing interference.

[0039] In summary, the implementation principle of this invention integrates key technologies such as parallel digital processing, programmable Doppler modulation, adaptive parameter matching, and ultra-fast response, solving the problems of low phase coherence, slow response, and poor suppression effect on broadband radar in the prior art. It provides an efficient and flexible jamming generation method for radar countermeasures in complex electromagnetic environments.

[0040] As an optional supplement, the present invention also provides some other feasible methods for achieving the technical objectives of the present invention: Optionally, amplitude modulation of the digital IQ signal can be performed using the following steps: 1. Extract the signal envelope: Calculate the instantaneous amplitude of the input digital IQ signal.

[0041] 2. Generate modulated waveform: Generate a low-frequency or random modulated signal according to tactical requirements.

[0042] Sine / periodic modulation: used to simulate the beam modulation of a scanning antenna or a periodically fluctuating target.

[0043] Random noise modulation: Band-limited noise generated after passing through a low-pass filter is used to simulate random fluctuations and more effectively destroy CFAR.

[0044] 3. Perform amplitude modulation: Multiply the I and Q channels of the original signal with the modulation waveform respectively.

[0045] Optionally, Doppler frequency modulation can be applied to the amplitude-modulated signal using the following steps: 1. Set the deception speed: Based on the interference strategy (such as speed dragging or false target speed deception), set the desired Doppler frequency to be simulated.

[0046] 2. Generate complex rotation vector: Generate a complex exponential sequence (rotation vector) of unit amplitude in the digital domain. This sequence can be efficiently generated by a direct digital frequency synthesizer (DDS) or a numerically controlled oscillator (NCO).

[0047] 3. Perform complex multiplication (frequency shift): Perform complex multiplication on the amplitude-modulated complex signal and the complex rotation vector.

[0048] 4. Separate I / Q channels: Calculate the real and imaginary parts of the complex multiplication to obtain the I and Q signals after Doppler modulation.

[0049] Optionally, Doppler noise modulation can be applied to the signal after Doppler frequency modulation using the following steps: 1. Generate baseband noise: Generate a Gaussian white noise sequence.

[0050] 2. Forming band-limited noise: Passing the Gaussian white noise sequence through a digital low-pass filter, the bandwidth of which determines the width of the final "noise gate" on the velocity spectrum.

[0051] 3. Noise Up-conversion and Complex Signal Construction: Band-limited noise is used as the modulating signal and combined with a complex carrier with a center frequency of 0 (actually amplitude modulation). However, a more common approach is to directly use it as an additional phase or frequency modulator. An effective method is to add it as an additional phase term to the rotation vector of the Doppler frequency modulation.

[0052] Generate a new phase term.

[0053] Generate a complex rotation vector with noise modulation.

[0054] 4. Perform final modulation: Perform complex multiplication on the amplitude-modulated digital IQ signal and this more complex rotation vector.

[0055] 5. Output separation: The final digital IQ signal is obtained, which simultaneously includes amplitude, Doppler frequency, and Doppler noise modulation. Example 2

[0056] This embodiment provides a coherent comb spectrum interference suppression system, including: Receiver unit: Used to receive radar signals and perform down-conversion and analog-to-digital conversion; Digital signal processing unit: Implemented based on FPGA, including multiple coherent interference suppression modules (e.g., 16), each module is used to perform amplitude modulation, Doppler frequency modulation and Doppler noise modulation; Transmitting unit: Used to convert the modulated signal from digital to analog, up-convert to frequency, and amplify it before radiating.

[0057] The system has a fast response speed, with an interference reaction time shorter than the radar range gate duration. It can generate multiple narrowband interference signals to form a comb-like spectrum, achieving effective suppression.

[0058] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0059] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0060] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0061] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0062] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for suppressing interference using a coherent comb spectrum, characterized in that, include: Receive radar signals and convert the radar signals into digital IQ signals; In the digital domain, multiple coherent interference suppression modules are used to perform parallel modulation processing on the digital IQ signal. Each module modulates independently, and the I-channel and Q-channel signals output from all modules are summed to generate a coherent comb spectrum interference suppression signal. The modulation processing includes: Amplitude modulation is performed on the digital IQ signal; Doppler frequency modulation is applied to the amplitude-modulated signal. Doppler noise modulation is applied to the signal modulated by Doppler frequency. The modulated signal is converted into an analog signal, and then radiated to the radar after up-conversion and amplification; The coherent comb spectrum suppression interference signal is used to suppress the real target signal at the radar receiver.

2. The method according to claim 1, characterized in that, The amplitude modulation is achieved by multiplying the digital IQ signal with the amplitude control signal.

3. The method according to claim 1, characterized in that, The Doppler frequency modulation is achieved by multiplying the amplitude-modulated signal with the Doppler frequency offset signal generated by direct digital frequency synthesis (DDS). The Doppler frequency offset is independent of the input radio frequency.

4. The method according to claim 1, characterized in that, The Doppler noise modulation is achieved by multiplying the Doppler frequency modulated signal with the noise modulation signal, wherein the frequency of the noise modulation signal varies randomly within a preset modulation bandwidth, and the modulation frequency is 1 / 10 of the modulation bandwidth.

5. The method according to claim 1, characterized in that, Before the modulation process, the radar signal is pre-reconnaissance to obtain radar signal parameters, and the modulation process parameters are adjusted according to the parameters. The radar signal parameters include signal bandwidth, pulse width, repetition period, and intra-pulse modulation characteristics.

6. The method according to claim 5, characterized in that, The Doppler frequency offset of each coherent jamming module is calculated based on the radar signal bandwidth obtained from pre-reconnaissance. The Doppler frequency offset interval is the radar signal bandwidth divided by the number of coherent jamming modules minus one.

7. The method according to claim 1, characterized in that, The number of coherent suppression interference modules is 16, and each module is set with a different Doppler frequency offset.

8. The method according to claim 7, characterized in that, The Doppler frequency offsets are -37500kHz, -32500kHz, -27500kHz, -22500kHz, -17500kHz, -12500kHz, -7500kHz, -2500kHz, 2500kHz, 7500kHz, 12500kHz, 17500kHz, 22500kHz, 27500kHz, 32500kHz, and 37500kHz.

9. The method according to claim 1, characterized in that, The generation and radiation of the interference signal are completed within the range gate of the radar, and the interference response time is less than the duration of the radar range gate.

10. A coherent comb spectrum interference suppression system, characterized in that, To implement the method of any one of claims 1-9, comprising: The receiving unit is used to receive radar signals and perform down-conversion and analog-to-digital conversion to obtain digital IQ signals. The digital signal processing unit includes multiple coherent suppression interference modules, which are used to perform parallel modulation processing on the digital IQ signal in the digital domain to generate a coherent comb spectrum suppression interference signal. The transmitting unit is used to convert the modulated signal from digital to analog, up-convert to frequency, and amplify it before radiating it to the radar.

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