A dual-frequency cooperative anti-main lobe jamming method based on dual-band radar joint detection

Abstract

A dual-frequency cooperative anti-main lobe interference method based on dual-band radar joint detection, the dual-band radar transmits signals with different frequency modulation slopes at the same time, the false target positions formed by different frequency modulation slopes are different, the true target positions are the same, the detection results of different frequency bands are compared, if the dual-band detects the target at the same distance at the same time, it is determined to be a true target, otherwise it is determined to be a false target, the number of remaining false targets is checked, and the transmission signal parameters are adjusted according to the effect of removing interference.

Description

Technical Field

[0001] This invention belongs to the field of radar detection and anti-jamming technology, specifically relating to a dual-frequency cooperative anti-main lobe interference technology. Background Technology

[0002] Main lobe interference refers to interference signals entering through the main lobe of a radar antenna. Because the antenna's main lobe gain is high, the interference is amplified, creating false targets and severely impacting radar detection. With the development of digital radio frequency memory, interference agents can effectively intercept radar signals and reproduce them with high fidelity, producing interference with both suppression and deception effects. Main lobe interference not only has an absolute advantage in energy, but also exhibits a high degree of similarity to the echo signal of the true target in multiple dimensions, including the spatial, temporal, and frequency domains, making it difficult to completely eliminate during processing.

[0003] Frequency-controlled arrays can be used to form angle-range two-dimensional antenna patterns, enabling adaptive suppression of main lobe deception interference. However, this method is complex to design and difficult to implement in engineering. Adaptive beamforming techniques from a spatial perspective can counteract secondary main lobe interference, but are ineffective against defensive and coaxial support interference. Eigenspace projection filters out strong interference from a spatial spectrum estimation perspective, but requires prior information on the number of interference sources and demands that the interference be uncorrelated with the signal and noise. Blind source separation methods do not require knowledge of the source signal and transmission channel parameters, but the separation effect deteriorates as the difference between the target and interference directions decreases. Polarized digital beamforming, polarization coding, and polarization diversity interference suppression techniques are sensitive to noise. Therefore, existing technologies have limitations in main lobe anti-interference and cannot effectively identify and suppress interference.

[0004] Radar jamming countermeasures are essentially a confrontation of multi-dimensional electromagnetic wave resources. With the development of radar technology, some radars have begun to integrate multiple frequency bands, possessing the ability to perform frequency diversity operations across multiple frequency bands, and performing signal-level collaborative processing on multi-frequency band echo data, thus increasing the dimensions of signal processing. Summary of the Invention

[0005] The spacing between dense false targets generated by slice-based repeater jamming is linearly related to the frequency modulation of the radar transmitted signal. For radar platforms operating simultaneously on both frequencies, the actual target distance is fixed during synchronous transmission and reception. Utilizing the characteristic differences between targets and jamming during multi-band diversity operation, and the influence of transmitted signal parameters and jamming parameters on the generation location of dense false targets, signal-level joint processing is performed on the dual-frequency echo signals. The actual targets remain consistent in the time domain. False targets are removed by leveraging the differences between false targets and the consistency of actual targets, thus suppressing main lobe interference. This method is simple to implement and computationally inexpensive.

[0006] Dual-band radar transmits signals simultaneously using different frequency modulation slopes. Different frequency modulation slopes result in different positions for false targets, while the positions for true targets are the same. By comparing the detection results of different frequency bands, if both frequency bands detect a target simultaneously within the same range, it is considered a true target; otherwise, it is considered a false target. The number of remaining false targets is checked, and the transmission signal parameters are adjusted based on the effectiveness of interference removal.

[0007] If all false targets are removed, the interference is considered to have been effectively suppressed.

[0008] If the remaining targets are not found, then the false targets are considered to overlap within multiple distance thresholds.

[0009] If the false targets overlap at a position that is a common multiple of their spacing, the dual-band transmission signal parameters are adjusted to increase the common multiple of the spacing between false targets in different bands; if the dual-band determines that the false targets that are close to each other are within the same distance threshold, the radar bandwidth is increased and the radar resolution is improved.

[0010] If the number of targets remains unchanged, it is determined that false targets have not been removed, and the spacing between false targets in both frequency bands is consistent.

[0011] Check and confirm that the frequency modulation slopes of the two frequency bands are inconsistent; if multiple jamming aircraft are using different jamming parameters to jam radars on different frequency bands, calculate the jammer parameters according to the distance between the false targets, adjust the radar signal parameters, and re-detect. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of scene modeling.

[0013] Figure 2 This is a flowchart of the anti-interference processing procedure.

[0014] Figure 3 This is a waveform diagram of radar echo pulse compression without interference.

[0015] Figure 4 This is a waveform diagram of the radar echo pulse compression caused by interference.

[0016] Figure 5 This is a comparison chart of detection results for frequency band 1 and frequency band 2.

[0017] Figure 6 It is a removal rate curve from multiple experiments. Detailed Implementation

[0018] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0019] Scene modeling, such as Figure 1As shown, the jamming aircraft flies alongside the target aircraft, maintaining a straight line between the target aircraft and the radar. The jamming aircraft intercepts the radar's transmitted signals, generates intermittent sampling jamming, suppresses and deceives radar detection, and protects the target aircraft from detection.

[0020] Since the spacing between false targets is proportional to the frequency modulation of the radar transmitted signal, the time-domain collaborative detection and union method can effectively remove false targets and counteract main lobe slice relay interference for targets within the same detection range threshold, and provide corresponding strategies for different detection results.

[0021] Dual-band radar transmits signals simultaneously using different frequency modulation slopes, and the location of false targets created by slice-based relay interference is... ,in K It is a positive integer. k This is the frequency modulation slope, which is the ratio of the transmitted signal pulse width to the bandwidth. Tu To interfere with the sampling interval of the aircraft, for the same interfering aircraft, the positions of the false targets will be different when the tuning frequency is different, but the positions of the real targets will be the same.

[0022] By comparing the detection results of different frequency bands, if the target is detected simultaneously by both frequency bands within the same distance range, it is considered a real target; otherwise, it is considered a false target.

[0023] Check the number of remaining false targets, and adjust the transmission signal parameters based on the effectiveness of interference removal, such as... Figure 2 As shown.

[0024] If all false targets are removed, the interference is considered to have been effectively suppressed.

[0025] If the remaining targets are not found, it is determined that the false targets overlap within multiple range thresholds. There are two reasons for this: one is that the common multiple of the distance between false targets in different frequency bands is small, and they overlap at the common multiple distance; the other is that the radar resolution is insufficient, and it judges the false targets that are close to each other to be within the same range threshold.

[0026] If the false targets overlap at a position that is a common multiple of their spacing, then adjust the dual-band transmission signal parameters according to the spacing of the false targets detected in different frequency bands, increase the common multiple of the spacing of the false targets in different bands, and separate the false targets detected in different bands.

[0027] If dual-band radar determines that close false targets fall within the same distance threshold, then increasing the radar bandwidth and improving radar resolution will separate the false targets.

[0028] If the number of targets remains unchanged, it is determined that the false targets have not been removed. The spacing between the false targets in both frequency bands is consistent, and the interference cannot be removed. This could be because the frequency modulation slopes of both frequency bands are consistent, or it could be because multiple jamming aircraft are using different jamming parameters to jam radars in different frequency bands.

[0029] Check and confirm whether the frequency modulation slopes of the two frequency bands are consistent. If they are consistent, change the radar signal parameters to make the frequency modulation slopes different. If multiple jamming aircraft use different jamming parameters to jam radars of different frequency bands, resulting in the same distance between false targets, calculate the jamming aircraft parameters according to the distance between the false targets, adjust the radar signal parameters, and re-detect.

[0030] The jamming aircraft was positioned 120km away, and intermittent sampling jamming was implemented with a sampling interval of 10μs and an interference-to-noise ratio of 20dB. The target aircraft was positioned 121km away, and the radar operated in dual frequency bands, transmitting and receiving signals simultaneously.

[0031] The transmit signal pulse width of band 1 is 500μs, bandwidth is 2MHz, pulse repetition period is 2000μs, and signal-to-noise ratio is 10dB; the transmit signal pulse width of band 2 is 700μs, bandwidth is 1.5MHz, pulse repetition period is 2000μs, and signal-to-noise ratio is 10dB.

[0032] Uninterrupted radar echo pulse compression, such as Figure 3 As shown, the radar detected an interfering aircraft at 120km and a target aircraft at 121km. The actual target locations were the same across different frequency bands.

[0033] Radar echo pulse compression affected by dense decoys, such as Figure 4 As shown, the radar cannot correctly detect the real target.

[0034] Comparing the detection results of frequency band 1 and frequency band 2, targets with identical detection results in both bands within the same distance threshold are retained, while those with different detection results are identified as false targets. Figure 5 As shown, the jamming aircraft is at 120km, and the main false target generated by intermittent sampling jamming is at 121.5km.

[0035] Multiple experiments were conducted using different signal parameters, and the removal rate was as follows: Figure 6 As shown, the average interference removal rate is over 96% after 100 trials. By adopting a specified strategy to transmit signal parameters, the interference suppression effect is improved, effectively suppressing main lobe interference.

[0036] The above are embodiments of the present invention and do not limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention are included within the protection scope of the present invention.

Claims

1. A dual-frequency cooperative anti-main lobe interference method based on dual-band radar joint detection, characterized in that, include: Dual-band radar transmits signals simultaneously using different frequency modulation slopes. Different frequency modulation slopes result in different positions for false targets, while the positions for true targets are the same. By comparing the detection results of different frequency bands, if both frequency bands detect a target simultaneously within the same range, it is considered a true target; otherwise, it is considered a false target. The number of remaining false targets is checked, and the transmission signal parameters are adjusted based on the effectiveness of interference removal.

2. The dual-frequency cooperative anti-main lobe interference method based on dual-band radar joint detection according to claim 1, characterized in that, The process of checking the number of remaining false targets includes: if all false targets are removed, the interference is considered to be effectively suppressed; if some targets remain, the false targets are considered to overlap within multiple distance thresholds; if the number of targets remains unchanged, the false targets are considered not to have been removed and the spacing between false targets in both frequency bands is consistent.

3. The dual-frequency cooperative anti-main lobe interference method based on dual-band radar joint detection according to claim 2, characterized in that, The false targets overlap within multiple range thresholds, including: if the false targets overlap at a position that is a common multiple of their distance, then adjust the dual-band transmission signal parameters to increase the common multiple of the distance between false targets in different bands; if the dual-band determines that the false targets that are close to each other are within the same range threshold, then increase the radar bandwidth and improve the radar resolution.

4. The dual-frequency cooperative anti-main lobe interference method based on dual-band radar joint detection according to claim 2, characterized in that, The consistency of the false target spacing between the two frequency bands includes: checking and confirming that the frequency modulation slopes of the two frequency bands are inconsistent; if multiple jamming aircraft use different jamming parameters to jam radars of different frequency bands respectively, the jamming aircraft parameters are calculated according to the false target spacing, and the radar signal parameters are adjusted to re-detect.

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