Information modulation waveform anti-main lobe interference method and system

Abstract

This invention provides a method and system for resisting main lobe interference using information modulation waveforms. First, the radar generates a transmitted waveform and a modulation signal according to its operating mode. A hybrid modulation waveform is generated using the transmitted waveform and encrypted modulation information. The hybrid waveform is transmitted through the radar's transmission channel, and the radar echo is received through the receiving channel. An interference slice is extracted from the radar echo. The modulation information of the interference slice is decoded. Doppler information is extracted using the decoded information from the interference slice. Waveform recovery is performed using the Doppler information and the transmitted waveform. Finally, matched filtering is used to filter the recovered signal and perform target detection. This method is suitable for scenarios involving single self-defense jamming. It only requires modulating the encrypted information onto the transmitted signal in the radar's signal generator, without requiring modifications to complex hardware, making it easy to promote and widely applicable.

Description

Technical Field

[0001] This invention relates to the fields of radar and electronic countermeasures, and in particular to a method and system for resisting main lobe interference using information modulation waveforms. Background Technology

[0002] Radar technology has developed rapidly and has permeated all sectors of the national economy. One of the commonly used signals in modern radar is the linear frequency modulated (LFM) signal. This signal has excellent target detection characteristics, offering both high range resolution and long-range detection, as well as a large Doppler tolerance. Therefore, the LFM signal has become a standard signal for modern radar. Consequently, radar jamming techniques targeting LFM signals have developed rapidly, such as suppression jamming, dense repeater jamming, intermittent sampling jamming, and spectral dispersion jamming. These jamming techniques are becoming increasingly targeted and effective, driving the development of jammers from large platforms to smaller platforms and from high-power to more agile power. Simultaneously, radar anti-jamming measures and methods are becoming increasingly complex. Traditional methods using only the time, frequency, spatial, polarization, and energy domains are no longer sufficient to meet anti-jamming requirements. Often, a simple jamming operation requires complex anti-jamming measures across multiple domains, including space, time, and frequency. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of the prior art by providing a method and system for resisting main lobe interference using information modulation waveforms. This method does not require modification of the entire radar system hardware; only the waveform generator and the modulation information extraction in signal processing need to be updated, making it convenient for engineering implementation.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for resisting main lobe interference in information modulation waveforms, comprising the following steps: S1, Radar generates transmission signal and modulated signal The expression for the transmitted waveform is: ; in, This is the starting frequency for transmitting the signal; The slope of the linear frequency modulated signal; The operating bandwidth of the radar signal; the transmitted waveform The total length of the signal is ; The duration of the signal; Modulation signal The expression is: ; in, Indicates the first One code element, phase is The length of each symbol is Then the modulated signal The total length is ; S2, for the modulated signal Encryption is performed to obtain the encrypted signal: ; in, This is a classic encryption function; The key function used for encryption generates an encrypted hybrid waveform modulated signal from the encrypted signal and the radar transmitted signal. ; Among them, the hybrid waveform modulation signal The total time length is ; S3. Utilize the radar's transmission channel to modulate the mixed waveform signal. The signal is transmitted and received through the receiving channel: ; in, The signal received by the channel; For the target echo signal; This is a self-defense jamming signal, and the time delay of the jamming start point of the first slice relative to the transmitted signal is... , Assuming the noise level is [value], let [value] be [value]. ; S4. Extract the interference slice signal from the interference signal. Extract the starting interference length from the middle. The data, namely: ; in, This marks the time starting point for the first interference slice. Interference slice signal Interference slice extraction is performed, specifically as follows: ; in, For dot product calculation, i.e., interference slice signal Data with a moderate amplitude greater than twice the noise level is retained directly; otherwise, it is set to zero. In the sorted data... For the first There are slices, which are consecutive sets of non-zero data. The total number of slices is assumed to be . indivual; S5. Decode the modulation information of the interference slice to obtain the modulation signal. The symbol estimate: ; in, Encryption function The inverse function of , i.e., the decryption function; For the first The estimated value of each code element; According to the modulation signal symbol estimate The width and symbol interval of the first two slices can be used to calculate the time width of the interference slice. Switching parameters It can determine the time delay of the target's starting position. Among them, time width That is, the first slice The corresponding length, that is: Start position delay ,in, For the second slice Corresponding time starting point ; For the first slice The corresponding starting point of time; The slice length; S6. Utilizing modulation signals symbol estimate The first slice Decoded value The Doppler frequency shift phase factor of the target is obtained: ; in, This indicates taking the average value; S7. Delay at the target's location Waveform recovery is performed at the location where the interference signal is located, i.e., the interference signal is restored. Location delay Radar receiving data Perform a replacement; the length of the replacement data is [length missing]. ; S8, then update the interference signal Use transmission signal Perform time-domain matched filtering to obtain the output signal: ; in, The convolution process is performed on the symbols, and then the matched filter output signal is processed. Then perform target detection.

[0005] Furthermore, the modulation signal in S1 is a random phase modulation signal.

[0006] Furthermore, in S2, the classic encryption functions include chaotic encryption and linear transformation.

[0007] Furthermore, the waveform recovery in step 7 employs recovery of only the data segments affected by interference.

[0008] Furthermore, in S8, the time-domain matched filtering can be processed in the frequency domain, as shown in the formula: ; in, Indicates Fourier transform; This represents the inverse Fourier transform.

[0009] Furthermore, an information modulation waveform anti-main lobe interference system includes: at least one processor, and a memory communicatively connected to at least one of the processors; wherein, The memory stores instructions that can be executed by the processor to implement the information modulation waveform anti-main lobe interference method according to any one of claims 1 to 5.

[0010] The beneficial effects of this invention are: the method is applicable to single self-defense jamming scenarios, and only requires modulating the encrypted information onto the transmitted signal in the radar signal generator. It does not require modification of complex hardware equipment, is easy to promote, and has good applicability. This method only requires adding interference extraction and decoding software algorithms to the signal processing unit, without changing the software in the original radar system. It is easy to upgrade and replace, has good real-time performance, and the computational load is only slightly increased compared to the original system.

[0011] This method only involves signal generation and processing, which can be achieved through software upgrades without altering other system structures, and thus has significant potential for widespread application. Attached Figure Description

[0012] Figure 1 This is a flowchart of a method for resisting main lobe interference in information modulation waveforms. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0014] Please see Figure 1A method for resisting main lobe interference using information modulation waveforms is proposed. First, the radar generates a transmitted waveform and a modulation signal according to its operating mode. A hybrid modulation waveform is generated using the transmitted waveform and encrypted modulation information. The hybrid waveform is transmitted through the radar's transmission channel, and the radar echo is received through the receiving channel. An interference slice is extracted from the radar echo. The modulation information of the interference slice is decoded. Doppler information is extracted using the decoded information of the interference slice. Waveform recovery is performed using the Doppler information and the transmitted waveform. Finally, matched filtering is used to filter the recovered signal and perform target detection. Specifically, it includes the following steps: S1, Radar generates transmission signal and modulated signal The expression for the transmitted waveform is: ; in, This is the starting frequency for transmitting the signal; The slope of the linear frequency modulated signal; The operating bandwidth of the radar signal; the transmitted waveform The total length of the signal is ; The duration of the signal; Modulation signal The expression is: ; in, Indicates the first One code element, phase is The length of each symbol is Then the modulated signal The total length is ; In the embodiments, it is assumed that , MHz, bandwidth microseconds, then , for: ; In the embodiment, the modulation signal The signal is a fixed-phase encoded signal, assuming microseconds ,Right now ; in, There are 10 symbols in total, and their phase is assumed to be... If the length of each symbol is 1 microsecond, then The total length of the signal is 10 microseconds.

[0015] S2, for the modulated signal Encryption is performed to obtain the encrypted signal: ; in, It uses a classic encryption function, but employs chaotic encryption. For the encryption key function, a random sequence is used as the encryption key. The encrypted mixed waveform modulated signal is generated from the encrypted signal and the radar transmitted signal. ; Among them, the hybrid waveform modulation signal The total time length is ; at this time, The length is 110 microseconds.

[0016] S3. Utilize the radar's transmission channel to modulate the mixed waveform signal. The signal is transmitted and received through the receiving channel: ; in, The signal received by the channel has an amplitude lower than the noise level; For the target echo signal; This is a self-defense jamming signal with an amplitude much higher than the noise level, and the time delay of the jamming start point in the first slice relative to the transmitted signal is... , Assuming the noise level is [value], let [value] be [value]. ; In one specific implementation, it is assumed that the time delay of the starting point of the first interference slice is... Microseconds, lasting 2 microseconds.

[0017] S4. Extract the interference slice signal from the interference signal. Extract the starting interference length from the middle. The data, namely: ; in, This marks the time starting point for the first interference slice. Interference slice signal Interference slice extraction is performed, specifically as follows: ; in, For dot product calculation, i.e., interference slice signal Data with a moderate amplitude greater than twice the noise level is retained directly; otherwise, it is set to zero. In the sorted data... For the first There are slices, which are consecutive sets of non-zero data. The total number of slices is assumed to be . indivual; In one specific implementation, the extracted data length is 10 microseconds, and it can be seen from S3 that the time starting point of the first interference slice is 1000 microseconds; S3 indicates that the duration is 2 microseconds and there are only 3 slices. As can be seen from S3, the time length of each slice is 2 microseconds.

[0018] S5. Decode the modulation information of the interference slice to obtain the modulation signal. The symbol estimate: ; in, Encryption function The inverse function of , i.e., the decryption function; For the first The estimated value of each code element; According to the modulation signal symbol estimate The width and symbol interval of the first two slices can be used to calculate the time width of the interference slice. Switching parameters It can determine the time delay of the target location. Among them, time width That is, the first slice The corresponding length, that is: Target starting position delay ,in, For the second slice Corresponding time starting point ; For the first slice The corresponding starting point of time; The slice length; In this example, there are 10 code elements. The modulation information of the interference slice is decoded to obtain... The symbol estimate: ; Phase after decoding of 10 symbols in the example ,according to The first two slices and The time width of the interference slice can be calculated from the width and symbol interval. Switching parameters It can determine the target's location and time delay. The width can be determined from S4. It is 2 microseconds. 1000 microseconds It is 1004 microseconds, so cloud computing obtains This indicates that the interference is intermittent sampling interference with switching from 1 to 1, and the starting position of the target can be calculated to be 998 microseconds.

[0019] S6. Utilizing modulation signals symbol estimate The first slice Decoded value The Doppler frequency shift phase factor of the target is obtained: ; in, This indicates taking the average value; In the embodiments, the following methods are used: The first slice Corresponding phase-coded signal Estimate the Doppler frequency shift phase factor of the target. ; In the formula, This indicates that the average value is taken, that is, the average value is taken over 1 microsecond of the calculation data; S7. Delay at the target's location Waveform recovery is performed at the location where the interference signal is located, i.e., the interference signal is restored. Location delay Radar receiving data Perform a replacement; the length of the replacement data is [length missing]. ; Target location delay in the embodiment The waveform is 998 microseconds. We perform waveform recovery at this point, which means... latency Radar receiving data at microseconds Perform a replacement, specifying the length of the replacement data. The time interval is 100 microseconds, meaning all data within the range of 998 to 1097 microseconds will be replaced.

[0020] S8, then update the interference signal A transmission signal with a duration of 100 microseconds Perform time-domain matched filtering to obtain the output signal: ; in, The convolution process is performed on the symbols, and then the matched filter output signal is processed. Then perform target detection.

[0021] The modulation signal in S1 is a random phase modulation signal.

[0022] In S2, the classic encryption functions include chaotic encryption and linear transformation.

[0023] The waveform recovery described in section 7 uses the recovery of only the data segments affected by interference.

[0024] In S8, the time-domain matched filtering can be processed in the frequency domain, as shown in the formula: ; in, Indicates Fourier transform; This represents the inverse Fourier transform.

[0025] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be defined by the appended claims.

Claims

1. A method for resisting main lobe interference in information modulation waveforms, characterized in that, Includes the following steps: S1, Radar generates transmission signal and modulated signal The expression for the transmitted waveform is: ； in, This is the starting frequency for transmitting the signal; The slope of the linear frequency modulated signal; The operating bandwidth of the radar signal; the transmitted waveform The total length of the signal is ; The duration of the signal; Modulation signal The expression is: ； in, Indicates the first One code element, phase is The length of each symbol is Then the modulated signal The total length is ; S2, for the modulated signal Encryption is performed to obtain the encrypted signal: ； in, This is a classic encryption function; The key function used for encryption generates an encrypted hybrid waveform modulated signal from the encrypted signal and the radar transmitted signal. ； Among them, the hybrid waveform modulation signal The total time length is ; S3. Utilize the radar's transmission channel to modulate the mixed waveform signal. The signal is transmitted and received through the receiving channel: ； in, The signal received by the channel; For the target echo signal; This is a self-defense jamming signal, and the time delay of the jamming start point of the first slice relative to the transmitted signal is... , Assuming the noise level is [value], let [value] be [value]. ; S4. Extract the interference slice signal from the interference signal. Extract the starting interference length from the middle. The data, namely: ； in, This marks the time starting point for the first interference slice. Interference slice signal Interference slice extraction is performed, specifically as follows: ； in, For dot product calculation, i.e., interference slice signal Data with a moderate amplitude greater than twice the noise level is retained directly; otherwise, it is set to zero. In the sorted data... For the first There are slices, which are consecutive sets of non-zero data. The total number of slices is assumed to be . indivual; S5. Decode the modulation information of the interference slice to obtain the modulation signal. The symbol estimate: ； in, Encryption function The inverse function of , i.e., the decryption function; For the first The estimated value of each code element; According to the modulation signal symbol estimate The width and symbol interval of the first two slices can be used to calculate the time width of the interference slice. Switching parameters It can determine the time delay of the target's starting position. Among them, time width That is, the first slice The corresponding length, that is: Start position delay ,in, For the second slice Corresponding time starting point ; For the first slice The corresponding starting point of time; The slice length; S6. Utilizing modulation signals symbol estimate The first slice Decoded value The Doppler frequency shift phase factor of the target is obtained: ； in, This indicates taking the average value; S7. Delay at the target's location Waveform recovery is performed at the location where the interference signal is located, i.e., the interference signal is restored. Location delay Radar receiving data Perform a replacement; the length of the replacement data is [length missing]. ; S8, then update the interference signal Use transmission signal Perform time-domain matched filtering to obtain the output signal: ； in, The convolution process is performed on the symbols, and then the matched filter output signal is processed. Then perform target detection.

2. The method for resisting main lobe interference in information modulation waveforms according to claim 1, characterized in that: The modulation signal in S1 is a random phase modulation signal.

3. The method for resisting main lobe interference in information modulation waveforms according to claim 1, characterized in that: In S2, the classic encryption functions include chaotic encryption and linear transformation.

4. The method for resisting main lobe interference in information modulation waveforms according to claim 1, characterized in that: The waveform recovery described in section 7 uses the recovery of only the data segments affected by interference.

5. The method for resisting main lobe interference in information modulation waveforms according to claim 1, characterized in that: In S8, the time-domain matched filtering can be processed in the frequency domain, as shown in the formula: ； in, Indicates Fourier transform; This represents the inverse Fourier transform.

6. A system for resisting main lobe interference in information modulation waveforms, characterized in that, include: At least one processor, and a memory communicatively connected to at least one of the processors; wherein, The memory stores instructions that can be executed by the processor to implement the information modulation waveform anti-main lobe interference method according to any one of claims 1 to 5.

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