A main lobe deception jamming suppression method based on waveform diversity and subspace projection

Abstract

The application discloses a main lobe deception jamming suppression method based on waveform diversity and subspace projection, which can effectively suppress the main lobe deception jamming in the form of intermittent sampling and forwarding. The specific steps are as follows: step 1, a waveform of a transmission signal is designed as an inter-pulse agile waveform according to jamming parameters, and a received echo is obtained after the transmission signal is transmitted by a radar. Step 2, a reconstruction submodule is used to perform reconstruction processing on the jamming signal in the received echo, and a reconstruction result of the jamming signal is obtained. Step 3, the reconstruction submodule is used to perform reconstruction processing on the target signal in the received echo after the cancellation of the jamming signal, and a reconstruction result of the target signal is obtained. Step 4, the reconstruction result of the target signal is cancelled from the received echo, and the jamming signal in the updated received echo is taken as the input of step 2, and steps 2-3 are executed in cycles until iteration is completed, and the main lobe deception jamming in the form of intermittent sampling and forwarding can be effectively suppressed after multiple iterations.

Description

Technical Field

[0001] This invention belongs to the field of anti-interference technology, specifically relating to a main lobe deception interference suppression method based on waveform diversity and subspace projection. Background Technology

[0002] As one of the most important jamming methods, radar main lobe deception jamming generates high-fidelity echo signals by simulating them, confusing enemy radar and affecting its detection and tracking of real targets. Currently, the most widely used radar jamming equipment is the Digital Radio Frequency Memory (DRFM). DRFM stores radar signal samples, and then copies and modulates these samples to generate various types of jamming signals.

[0003] Currently, the most effective main lobe deception jamming style based on DRFM is intermittent sampling and forwarding jamming. This type of jamming repeatedly intercepts and forwards the radar transmitted signal, making the jamming signal partially coherent with the radar transmitted signal. This allows for some processing gain in subsequent pulse compression and coherent accumulation, reducing the demand on transmit power. Simultaneously, due to its intermittent sampling and forwarding mode, the jamming signal forms multiple false target groups after pulse compression. By designing the sampling time and the number of forwards, both suppression and deception jamming effects can be achieved. Most common methods for countering intermittent sampling and forwarding jamming use a Linear Frequency Modulation (LFM) signal as the transmitted signal. They extract interference-free target echo segments from the received echo to construct a bandpass filter, and then apply bandpass filtering to the de-skewed received echo to achieve interference suppression. Alternatively, they directly reconstruct the target echo by sparse recovery of the extracted target echo segments after de-skewing. However, these methods require a high signal-to-noise ratio and target echo segments that are not completely obscured by the jamming, which is difficult to achieve in practical electronic warfare scenarios.

[0004] Currently, main lobe deception jamming, which is mainly characterized by intermittent sampling and forwarding, has become a major threat to modern radar. Existing methods have limitations in suppressing intermittent sampling and forwarding jamming. Therefore, there is an urgent need for a method that can effectively suppress main lobe deception jamming in the form of intermittent sampling and forwarding. Summary of the Invention

[0005] In view of this, the present invention provides a main lobe spoofing interference suppression method based on waveform diversity and subspace projection, which can effectively suppress main lobe spoofing interference in the form of intermittent sampling and forwarding.

[0006] To achieve the above objectives, the technical solution of the present invention includes the following steps:

[0007] Step 1: Design the waveform of the transmitted signal as an inter-pulse agile waveform according to the interference parameters. After the transmitted signal is transmitted by the radar, the received echo (Echo) is obtained.

[0008] Step 2: Use the reconstruction submodule to reconstruct the interference signal in the received signal, and obtain the reconstruction result R of the interference signal. J .

[0009] Step 3: Use the refactored submodule to cancel R J The target signal in the received echo is then reconstructed to obtain the reconstructed target signal R. T .

[0010] Step 4: Reconstruct the target signal R from the received echo after cancellation. T The interference signal in the updated received echo is used as input to step 2. The process returns to step 2 and repeats steps 2-3 until the set number of iterations is reached, or the reconstruction result R of the target signal from the previous iteration is obtained. T The reconstruction result R of the target signal in this iteration T If the difference is less than the set threshold, the target result after interference reconstruction cancellation is obtained.

[0011] Furthermore, based on the interference parameters, the waveform of the transmitted signal is designed as an inter-pulse agile waveform, specifically: the interference intermittent sampling width T is estimated using interference sensing technology. j =[T j1 ,T j2 ,...,T jM and intermittent sampling period T s =[T s1 ,T s2 ,...,T sM ], where m is the interference intermittent sampling sequence number and M is the number of interference intermittent samplings; construct the envelope U of the interference intermittent samplings in the transmitted signal. J (t) and the envelope U that was not sampled by interference T (t), ;by U J (t) and U T (t) Construct the nth transmitted signal u n (t), and N pulse signals are sequentially designed to generate inter-pulse agile waveforms.

[0012] Furthermore, the envelope U of the intermittent sampling is interfering. J (t) is,

[0013]

[0014] in t represents the time axis.

[0015] Uninterrupted sampling of the envelope U in the transmitted signalT (t) is represented as:

[0016]

[0017] Where T p This represents the pulse width of the transmitted signal.

[0018] Suppose the transmitted signal has N pulses, and the signal modulated within each pulse is s(t); the interference intermittent sampling portion of the nth transmitted signal modulates the initial phase. Uninterrupted sampling of the partial modulation initial phase Then the nth transmitted signal u n (t) is represented as:

[0019]

[0020] Furthermore, the reconstruction submodule includes the following processing steps: inter-pulse phase compensation, fast-time matched filtering, subspace projection, fast-time inverse matched filtering, and inter-pulse phase recovery.

[0021] Inter-pulse phase compensation specifically refers to compensating the inter-pulse modulation phase of each pulse of the input signal to obtain the compensated signal.

[0022] The fast-time matched filtering process is as follows: a reference signal is set along the fast time dimension, and the compensated signal is subjected to matched filtering to obtain E1.

[0023] Subspace projection is specifically as follows: pulse Doppler (PD) processing is performed on E1 along the slow time dimension, the Doppler frequencies corresponding to the peak points in the PD processing results are extracted, a subspace projection matrix is ​​constructed using the Doppler frequencies corresponding to the peak points, and E1' is obtained by subspace projection using the subspace projection matrix.

[0024] The fast-time inverse matched filtering process is as follows: perform inverse matched filtering on E1' along the fast-time dimension to obtain the inverse matched filtering result.

[0025] To restore the inter-pulse phase, specifically, the inter-pulse modulation phase of each pulse is added to the inverse matched filtering result to obtain the reconstructed result.

[0026] Furthermore, a reconstruction submodule is used to reconstruct the interference signal in the received echo. The input signal of the reconstruction submodule is the received echo minus the reconstruction result of the target signal from the previous iteration. The initial value of the reconstruction result of the target signal is set to 0.

[0027] The specific reconstruction process for interference signals is as follows:

[0028] First, the interference modulation phase of each pulse in the echo compensation is adjusted. And along the fast time dimension to interfere with the sampling part UJ E1 is obtained by performing matched filtering on Echo using the reference signal s(t)·s(t). Then, PD processing is performed on E1 along the slow time dimension, and the Doppler frequency corresponding to the peak point in the PD processing result is extracted and denoted as F. j =[f j (1),f j (2),...,f j [(K1)], where K1 is the number of different Doppler channels where the peak point is located, and the interference subspace projection matrix P is constructed according to equation (4). J :

[0029]

[0030] in,(·) H This indicates the complex conjugate transpose, (·). -1 Represents the inverse of a matrix. Let q represent the Kronecker product, where q = [0, 1, ..., N-1]. T .

[0031] Subspace projection of E1 yields E'1.

[0032] E'1=P J E1 (5)

[0033] Then, inverse matched filtering is performed on E1' along the fast time dimension, and interference modulation phases for each pulse are added. The reconstruction result R of the interference is obtained. J .

[0034] Furthermore, a reconstruction submodule is used to reconstruct the target signal in the received echo. At this time, the input signal of the reconstruction submodule is the received echo minus the interference reconstruction result.

[0035] The specific reconstruction process for the target signal is as follows:

[0036] First, the interference R reconstructed from the received echo is cancelled. J Then compensate for the target modulation phase of each pulse. And along the fast time dimension to interfere with the unsampled portion U T (t)·s(t) is the reference signal pair (Echo-R) J Perform matched filtering to obtain E2, then perform PD processing along the slow time dimension, and extract the Doppler frequency corresponding to the peak point in the PD processing result, denoted as F. t =[f t (1),f t (2),...,f t [(K2)], where K2 is the number of different Doppler channels where the peak point is located, and the target subspace projection matrix is ​​constructed according to Equation (6).

[0037]

[0038] And by subspace projection of E2, we obtain E'2.

[0039] E'2=P T E2 (7)

[0040] Then, inverse matched filtering is performed on E'2 along the fast time dimension, and the target modulation phase of each pulse is added. The reconstruction result R of the target is obtained. T .

[0041] Beneficial effects:

[0042] This invention proposes a main lobe spoofing interference suppression method based on waveform diversity and subspace projection. This method utilizes the difference between the intermittently sampled forwarding interference signal and the target echo signal in the echo domain. By designing an inter-pulse agile waveform, the interference and target are decorrelated in the range-Doppler domain. Then, the subspace projection method is used to reconstruct the anti-interference signal from the received echo while retaining the target echo signal. After multiple iterations, this method can effectively suppress main lobe spoofing interference in the form of intermittent sampling forwarding. This method has many advantages, including good interference suppression effect, low computational complexity, and good robustness. Attached Figure Description

[0043] Figure 1 This is a flowchart of the method proposed in this invention;

[0044] Figure 2(a) is a three-dimensional view of the PD processing result of the simulated echo after matched filtering;

[0045] Figure 2(b) shows the distance-amplitude projection of the simulated echo after PD processing via matched filtering;

[0046] Figure 3(a) is a three-dimensional view of the PD processing result after the simulated echo is processed by the method proposed in this invention;

[0047] Figure 3(b) is a distance-amplitude projection diagram of the PD processing result after the simulated echo is processed by the method proposed in this invention;

[0048] Figure 4(a) is a three-dimensional view of the PD processing result of the simulated echo after matched filtering when the interference parameter estimation is inaccurate;

[0049] Figure 4(b) shows the distance-amplitude projection of the simulated echo after matched filtering and PD processing when the interference parameter estimation is inaccurate.

[0050] Figure 5(a) is a three-dimensional view of the PD processing result of the simulated echo when the interference parameter estimation is inaccurate after processing by the method proposed in this invention;

[0051] Figure 5(b) shows the distance-amplitude projection of the PD processing result after the simulated echo with inaccurate interference parameter estimation is processed by the method proposed in this invention; Detailed Implementation

[0052] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0053] Currently, most search radars transmit LFM signals because they offer a large time-bandwidth product while also providing good Doppler tolerance. However, LFM signals, due to their simple modulation method and fixed parameters, are easily detected and intercepted by enemy jammers, leading to interference and affecting friendly radar operation. Pulse-agile waveforms, by utilizing the agility of signal parameters between waveforms, can fully leverage the degrees of freedom in the waveform domain, thus offering a significant advantage over LFM signals in anti-jamming. This invention employs a waveform grouping system and combines the differences between intermittent sampling and forwarding jamming signals and target echo signals in the echo domain. By designing intermittent sampling and forwarding waveforms, the interference is decorrelated with the target in the range-Doppler domain. Subspace projection is then used to reconstruct the canceled interference signal from the received echo while retaining the target echo signal. Through multiple iterative processes, this effectively suppresses main lobe deception interference in intermittent sampling and forwarding.

[0054] like Figure 1 As shown, the main lobe deception interference suppression method based on waveform diversity and subspace projection of the present invention specifically includes the following steps:

[0055] Step 1: Design inter-pulse agile waveforms based on interference parameters. Estimate the interference intermittent sampling width T using interference sensing technology. j =[T j1 ,T j2 ,...,T jM and intermittent sampling period T s =[T s1 ,T s2 ,...,T sM ], where m is the intermittent sampling sequence number and M is the number of intermittent samplings. Then the envelope U of the intermittent sampling is... J (t) is,

[0056]

[0057] in t represents the time axis. The envelope U of the transmitted signal that was not sampled due to interference... T (t) can be represented as,

[0058]

[0059] Where T pThis represents the pulse width of the transmitted signal. Since the interference signal does not include the portion of the transmitted signal that was not sampled during interference, this portion can be considered as the target signal to be detected.

[0060] Suppose the transmitted signal has N pulses, and the signal modulated within each pulse is s(t). The interference of the nth transmitted signal is intermittently sampled to modulate the initial phase. Uninterrupted sampling of the partial modulation initial phase Then the nth transmitted signal u n (t) is represented as,

[0061]

[0062] j is the imaginary unit. Using equation (3), N pulses are sequentially designed to generate inter-pulse agile waveforms.

[0063] Step 2: Use the reconstruction submodule to reconstruct the interference signal. First, connect to the echo compensation to compensate for the interference modulation phase of each pulse. And along the fast time dimension to interfere with the sampling part U J E1 is obtained by performing matched filtering on Echo using the reference signal s(t)·s(t). Then, PD processing is performed on E1 along the slow time dimension, and the Doppler frequency corresponding to the peak point in the PD processing result is extracted and denoted as F. j =[f j (1),f j (2),...,f j [(K1)], where K1 is the number of different Doppler channels where the peak point is located. The interference subspace projection matrix is ​​constructed according to equation (4).

[0064]

[0065] Subspace projection of E1 yields E'1.

[0066] E'1=P J E1 (5)

[0067] Then, inverse matched filtering is performed on E1' along the fast time dimension, and interference modulation phases for each pulse are added. The reconstruction result R of the interference is obtained. J .

[0068] Step 3: Reconstruct the target signal using the reconstruction submodule. First, cancel the reconstructed interference R from the received echo. J Then compensate for the target modulation phase of each pulse. And along the fast time dimension to interfere with the unsampled portion U T (t)·s(t) is the reference signal pair (Echo-R) JPerform matched filtering to obtain E2, then perform PD processing along the slow time dimension, and extract the Doppler frequency corresponding to the peak point in the PD processing result, denoted as F. t =[f t (1),f t (2),...,f t [(K2)], where K2 is the number of different Doppler channels where the peak point is located. The target subspace projection matrix is ​​constructed according to equation (6).

[0069]

[0070] And by subspace projection of E2, we obtain E'2.

[0071] E'2=P T E2 (7)

[0072] Then, inverse matched filtering is performed on E'2 along the fast time dimension, and the target modulation phase of each pulse is added. The reconstruction result R of the target is obtained. T .

[0073] Step 4: Iterate until the algorithm converges, obtaining the target result after interference reconstruction and cancellation. The target R reconstructed from the received echo is then determined through this process. T As input to step 3, and repeat steps 2-3 until the set number of iterations is reached, or R... T The algorithm terminates when the difference between the previous reconstruction result and the current reconstruction result is less than the set threshold.

[0074] The method proposed in this invention performs both interference and target reconstruction in Doppler mode. When the interference parameters are inaccurately estimated, it is only necessary to ensure that the true intermittent sampling portion of the interference is included in the designed U. J In (t)·s(t), only the interference distance dimension matched filtering result will be distorted, but the Doppler dimension will not be distorted. Therefore, it will not affect the final interference suppression effect, thus verifying the robustness of the proposed algorithm.

[0075] The beneficial effects of the invention will be verified and explained:

[0076] To verify the interference suppression effect of the proposed method, a comprehensive simulation test was conducted on a main lobe deception interference scenario using intermittent sampling and forwarding. The simulation set the distances and velocities of the false targets generated by the intermittent sampling and forwarding interference echo signals to be 102 km and 100 m / s; 101.85 km and 99 m / s; and 102.15 km and 101 m / s, respectively, while the target distances and velocities were 102 km and 100 m / s. The interference-to-signal ratio (ISR) was approximately 25 dB, and the signal-to-noise ratio (SNR) was approximately 15 dB. Figure 2(a) shows the PD processing result of the simulated echo after matched filtering. As shown in Figure 2(b), the false targets generated by the interference signal obscured the real target, severely affecting the detection of the real target. Figure 3(a) shows the PD processing result of the simulated echo after processing using the method proposed in this invention. As shown in Figure 3(b), the interference was effectively suppressed, and the processed ISR was less than -15 dB, demonstrating the effectiveness of the proposed method in suppressing main lobe deception interference in the intermittent sampling and forwarding format. Furthermore, to verify the robustness of the proposed algorithm, keeping the above simulation parameters unchanged, the actual interference sampling width was set to be smaller than the designed T. j Specifically, the interference's actual sampling width is 2μs, and the designed T j The duration is 2.5 μs. Figure 4(a) shows the PD processing result of the simulated echo after matched filtering when the interference parameter estimation is inaccurate. As can be seen from Figure 4(b), because the designed T j The mismatch between the actual sampling width and the interference causes the range dimension matched filtering result to differ from that in Figure 2(b). However, the generated false targets will still obscure the real targets. Figures 5(a) and 5(b) show the PD processing results of the simulated echo after processing by the method proposed in this invention when the interference parameters are not accurately estimated. As can be seen from the figures, when the interference parameters are not accurately estimated, the interference-to-signal ratio of the simulated echo after processing by the method proposed in this invention is still less than -15dB, thus verifying the robustness of the method proposed in this invention.

[0077] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for suppressing main lobe deception interference based on waveform diversity and subspace projection, characterized in that, Includes the following steps: Step 1: Design the waveform of the transmitted signal as an inter-pulse agile waveform according to the interference parameters. After the transmitted signal is transmitted by the radar, the received echo is obtained. Step 2: Use the reconstruction submodule to reconstruct the interference signal in the received signal to obtain the reconstruction result of the interference signal. ; Step 3: Use refactored submodules for cancellation The target signal in the received echo is then reconstructed to obtain the reconstructed target signal. ; Step 4: Reconstruct the target signal from the received echo after cancellation The interference signal in the updated received echo is used as input for step 2. The process returns to step 2 and repeats steps 2-3 until the set number of iterations is reached, or the reconstruction result of the target signal from the previous iteration is obtained. Reconstruction results of the target signal in this iteration If the difference is less than the set threshold, the target result after interference reconstruction cancellation is obtained.

2. The main lobe deception interference suppression method based on waveform diversity and subspace projection as described in claim 1, characterized in that, The waveform of the transmitted signal designed according to the interference parameters is a pulse-agile waveform, specifically: Estimating the sampling width of interference intervals using interference sensing techniques and intermittent sampling period ,in This is the intermittent sampling sequence number for interference. The number of intermittent samplings to prevent interference; Construct the envelope of the intermittent sampling of interference in the transmitted signal and the envelope sampled without interference ,;Depend on and Construct the first One transmitted signal The N pulse signals emitted in sequence are designed to generate inter-pulse agile waveforms.

3. The main lobe deception interference suppression method based on waveform diversity and subspace projection as described in claim 2, characterized in that, The envelope of the intermittent sampling interference for, （1） in , For time axis; Uninterrupted sampling envelope of the transmitted signal Represented as: （2） in The pulse width of the transmitted signal; Assume there are a total of Each pulse, the signal modulated within the pulse is ; for the first Interference sampling of the transmitted signal modulates the initial phase. The initial phase of the modulation that was not disturbed during sampling Then the first One transmitted signal Represented as: （3）。 4. The main lobe deception interference suppression method based on waveform diversity and subspace projection as described in claim 3, characterized in that, The reconstruction submodule performs the following processing steps: inter-pulse phase compensation, fast-time matched filtering, subspace projection, fast-time inverse matched filtering, and inter-pulse phase recovery. The inter-pulse phase compensation specifically refers to: compensating the inter-pulse modulation phase of each pulse of the input signal to obtain the compensated signal; The fast-time matched filtering process specifically involves: setting a reference signal along the fast time dimension and performing matched filtering on the compensated signal to obtain... ; The subspace projection specifically refers to: [the projection onto the subspace]. Pulse Doppler (PD) processing is performed along the slow time dimension. The Doppler frequencies corresponding to the peak points in the PD processing results are extracted. A subspace projection matrix is ​​constructed using the Doppler frequencies corresponding to the peak points. Subspace projection is then performed using the subspace projection matrix to obtain... ; The fast-time inverse matched filtering process specifically involves: [The text abruptly ends here, likely due to an incomplete sentence or a formatting error.] Perform inverse matched filtering along the fast time dimension to obtain the inverse matched filtering result; The recovery of inter-pulse phase specifically involves adding the inter-pulse modulation phase of each pulse to the inverse matched filtering result to obtain the reconstruction result.

5. The main lobe deception interference suppression method based on waveform diversity and subspace projection as described in claim 4, characterized in that, The method employs a reconstruction submodule to reconstruct the interference signal in the received echo. The input signal of the reconstruction submodule is the received echo minus the reconstruction result of the target signal from the previous iteration. The initial value of the reconstruction result of the target signal is set to 0. The specific reconstruction process for interference signals is as follows: First, connect to the received wave. Compensation for interference modulation phase of each pulse And along the fast time dimension to interfere with the sampling part For reference signal pair Perform matched filtering to obtain Then to Perform PD processing along the slow time dimension, and extract the Doppler frequencies corresponding to the peak points in the PD processing results, denoted as . , For different Doppler channel numbers at the peak point, the interference subspace projection matrix is ​​constructed according to equation (4). : （4） in, This indicates the complex conjugate transpose. Represents the inverse of a matrix. Indicates the Kronecker product. ; right Subspace projection is obtained , （5） Then to Inverse matched filtering is performed along the fast time dimension, and interference modulation phases are added to each pulse. The reconstruction results of the interference were obtained. .

6. The main lobe deception interference suppression method based on waveform diversity and subspace projection as described in claim 5, characterized in that, The reconstruction submodule is used to reconstruct the target signal in the received echo. At this time, the input signal of the reconstruction submodule is the received echo minus the interference reconstruction result. The specific reconstruction process for the target signal is as follows: First, let's start with receiving the echo. The interference reconstructed by the middle can be eliminated Then compensate for the target modulation phase of each pulse. And along the fast time dimension to interfere with the unsampled portion For reference signal pair Perform matched filtering to obtain Then, perform PD processing along the slow time dimension, and extract the Doppler frequencies corresponding to the peak points in the PD results, denoted as . , Given the different Doppler channel numbers at the peak points, the target subspace projection matrix is ​​constructed according to equation (6). （6） And on Subspace projection is obtained , （7） Then to Inverse matched filtering is performed along the fast time dimension, and the target modulation phase of each pulse is added. The reconstruction result of the target is obtained. .

Images