Intermittent sampling retransmission interference suppression method based on intra-pulse waveform cognitive optimization design

Abstract

This invention discloses an intermittent sampling and forwarding interference suppression method based on intra-pulse waveform cognitive optimization design. The radar station first transmits an intra-pulse linear frequency modulated (LFM) – inter-pulse frequency agile signal as a detection signal. Inter-pulse synthesis technology of the frequency agile waveform is used to obtain finer range resolution. Combined with the one-dimensional range profile features after compression and coherent processing of intermittent sampling direct forwarding or repetitive forwarding interference pulses, high-precision estimation of interference parameters is achieved. Based on the interference parameter estimation, the intra-pulse waveform is optimized using a close-fitting shielding waveform design strategy in radio frequency shielding. Interference suppression is achieved through post-processing of the optimized waveform. Simultaneously, considering the possibility of interference parameter variations, the second-order statistical measure of the working segment of the optimized waveform is used as the evaluation criterion to adaptively adjust the waveform transmission and processing strategies. This allows for dynamic adjustment of interference and waveform parameters, forming an adaptive closed-loop system for intermittent sampling and forwarding interference parameter interference and suppression.

Description

Technical Field

[0001] This invention belongs to the field of radar active jamming countermeasures technology, specifically relating to an intermittent sampling and forwarding jamming suppression method based on intra-pulse waveform cognitive optimization design. Background Technology

[0002] Radar operates in a constant state of adversarial warfare. Compared to jammers, radar's greatest advantage lies in its preemptive strike capability. Active radar anti-jamming technology, through rapid changes in waveform parameters such as frequency, repetition rate, and modulation scheme, prevents jammers from keeping up with the radar waveform's changes, thus rendering their radar parameter information outdated and unable to effectively interfere with the current radar waveform. Therefore, pulse-agile radar can cope with most electromagnetic countermeasures environments.

[0003] With the rapid development of digital radio frequency memory (DRFM) technology, the resulting jamming patterns have become more complex. To counter inter-pulse agile radar systems, intermittent sampling-relay jammers have been deployed on the battlefield. Their operation is characterized by extremely high sensitivity, capable of "intercepting-delaying-relaying" radar signals within a single pulse, thus disabling inter-pulse agile systems. This process generates coherent jamming, achieving a certain gain in radar signal processing and significantly reducing the power requirements of the jammer, thus providing a foundation for miniaturization and weight reduction. Therefore, such jammers can be mounted on small platforms such as UAVs, employing swarm tactics to create mainlobe jamming and multi-point source jamming, increasing the difficulty of radar countermeasures. Simultaneously, utilizing the digital processing capabilities of DRFM, ISRJ jammers can easily adjust jamming parameters to form different jamming strategies, posing a significant threat to radar.

[0004] Countermeasures against intermittent sampling-forwarding (ISBN) jamming primarily consider two dimensions: jamming parameter identification and waveform design. Estimation of jamming parameters mainly includes the number of slices, slice width, and forwarding frequency. Currently, ISBN jamming parameter estimation mainly involves time-frequency analysis of the jamming signal. For example, time-frequency analysis of the ISBN jamming pulse compression results yields the number of slices, and then deconvolution is used to estimate the slice width; or short-time fractional Fourier transform is used to obtain the jamming time-frequency distribution map, and binarization is used to estimate the jamming parameters. However, this method is computationally intensive, susceptible to noise, and the accuracy of parameter estimation needs improvement. Regarding waveform design for ISBN jamming countermeasures, orthogonal waveform design schemes with intra-pulse frequency coding are often used, suppressing jamming by eliminating the affected segments. However, due to the discrete sampling and truncation effects during signal processing, the segments are not perfectly orthogonal, leading to energy overflow in the affected segments. This significantly increases the pulse compression energy of the unaffected segments, resulting in a deterioration in the segment elimination effect and greatly increasing the complexity of jamming countermeasures. Furthermore, most interference suppression methods for intermittent sampling forwarding interference are based on the premise that the interference parameters are known. Currently, there is a lack of research on parameter estimation for intermittent sampling forwarding interference and related cognitive adversarial systems for interference suppression. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, this invention provides an intermittent sampling and forwarding interference suppression method based on intra-pulse waveform cognitive optimization design. The technical problem to be solved by this invention is achieved through the following technical solution:

[0006] This invention provides an intermittent sampling and forwarding interference suppression method based on intrapulse waveform cognitive optimization design, the method comprising:

[0007] Step 1: Within one coherent processing time, the radar transmits a detection signal targeting the target using a preset waveform transmission method, and performs pulse compression, inter-pulse range synthesis, and range image stitching on the received interfered signal to obtain a one-dimensional high-resolution range image; wherein, the preset waveform transmission method includes an intra-pulse linear frequency modulation-inter-pulse frequency agility waveform transmission method.

[0008] Step 2: Perform peak extraction on the obtained one-dimensional high-resolution distance image to obtain the amplitude and distance information of all peak points;

[0009] Step 3: Based on the primary and secondary false target feature information formed by intermittent sampling and forwarding interference, feature false targets are extracted from all detected peak points, and then interference parameter information including the number of slices, slice width and forwarding number is estimated.

[0010] Step 4: Using the estimated interference parameter information, based on the preset intra-pulse waveform scheme, transmit the cover segment signal during the interference interception period and the working segment signal during the interference forwarding period, while setting a frequency isolation zone between the cover segment and the working segment; wherein, the preset intra-pulse waveform scheme is optimized based on the radio frequency protection concept, including the intra-pulse waveform scheme of intra-pulse linear frequency modulation-close-fit radio frequency protection Costas frequency coding;

[0011] Step 5: After receiving the echo of the waveform after the pulse optimization design, the shield segment signal is not processed, and the working segment signal is subjected to segment pulse compression and segment decoupling to obtain the segment pulse compression result after segment decoupling. Then, the modulus-square mean square operation is performed on each segment in the segment pulse compression result to obtain the second-order statistics of each working segment of each pulse.

[0012] Step 6: Using the minimum value of the second-order statistic as a benchmark, perform threshold discrimination on the statistics of each working segment to obtain the threshold discrimination results;

[0013] Step 7: If the threshold discrimination result meets certain conditions, design the corresponding waveform processing scheme to obtain the real target information; otherwise, return to step 1 to update the interference parameters and waveform parameters.

[0014] The beneficial effects of this invention are:

[0015] (1) In view of the shortcomings of low accuracy of time-frequency analysis parameter estimation and susceptibility to noise, this invention proposes to use the "intra-pulse linear frequency modulation-inter-pulse frequency agility" waveform as the detection waveform. On the one hand, the coherent characteristics of intermittent sampling forwarding interference are utilized to improve the interference-to-noise ratio of the received waveform through coherent processing to obtain better parameter estimation accuracy. On the other hand, due to the inter-pulse synthesis of frequency agility signal, the range resolution is significantly improved. The range profile distribution characteristics of intermittent sampling forwarding interference can be used to improve the estimation accuracy of interference parameters.

[0016] (2) In view of the fact that the frequency-coded waveform in the pulse is easily affected by the discrete effect and truncation effect in the signal processing process, which causes the energy of the interfered segment to overflow into the uninterrupted segment and significantly reduces the anti-interference effect, this invention proposes an intra-pulse waveform optimization design method based on the radio frequency shielding concept. The intra-pulse waveform is optimized by using a close-fitting shielding waveform design strategy. A high-frequency shielding signal is transmitted during the interference sampling time and a low-frequency working signal is transmitted during the interference forwarding time. At the same time, a frequency isolation zone is set between the shielding segment and the working segment to ensure that the shielding segment and the working segment have good orthogonality and eliminate the influence of the discrete effect and truncation effect in the signal processing process on the working segment.

[0017] (3) Given the limited research on parameter estimation and cognitive countermeasure systems for intermittent sampling and forwarding jamming, this invention proposes an adaptive closed-loop system of "jamming parameter estimation - radar waveform design - jamming suppression," providing a feasible approach for the systematic countermeasure against intermittent sampling and forwarding jamming. By transmitting "intra-pulse linear frequency modulation - inter-pulse frequency agility" signals, high-precision estimation of jamming parameters is achieved. Based on this estimation, the intra-pulse waveform is optimized using the concept of radio frequency cover, and the processing results of the intra-pulse waveform are used as evaluation indicators to determine the processing strategy of the given cognitive countermeasure system, thus forming an adaptive cognitive countermeasure closed-loop system for intermittent sampling and forwarding jamming. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating an intermittent sampling and forwarding interference suppression method based on intra-pulse waveform cognitive optimization design provided by an embodiment of the present invention;

[0019] Figure 2 This is a flowchart illustrating the implementation of an intermittent sampling and forwarding interference suppression method based on intra-pulse waveform cognitive optimization design, as provided in an embodiment of the present invention.

[0020] Figure 3 This is a waveform diagram of "intra-pulse linear frequency modulation - inter-pulse frequency agility" provided in an embodiment of the present invention;

[0021] Figure 4(a) is a schematic diagram of the optimized waveform provided by an embodiment of the present invention to deal with intermittent sampling direct forwarding interference;

[0022] Figure 4(b) is a schematic diagram of the optimized waveform provided by an embodiment of the present invention to cope with intermittent sampling and repeated forwarding interference;

[0023] Figure 5(a) is a schematic diagram of the intermittent sampling direct forwarding interference signal pulse compression output result provided in the embodiment of the present invention;

[0024] Figure 5(b) is a schematic diagram of the inter-pulse distance synthesis result of the intermittent sampling direct forwarding interference signal provided in the embodiment of the present invention;

[0025] Figure 6(a) is a schematic diagram of the pulse compression output result of the intermittent sampling and repeated forwarding interference signal provided in the embodiment of the present invention;

[0026] Figure 6(b) is a schematic diagram of the inter-pulse distance synthesis result of the intermittent sampling and repeated forwarding interference signal provided in the embodiment of the present invention;

[0027] Figure 7(a) is a time-frequency diagram of the optimized waveform echo signal under intermittent sampling direct forwarding interference provided in an embodiment of the present invention;

[0028] Figure 7(b) is a schematic diagram of the pulse compression output result of the optimized waveform under intermittent sampling direct forwarding interference provided in the embodiment of the present invention;

[0029] Figure 8(a) is a time-frequency diagram of the optimized waveform echo signal under intermittent sampling and repeated forwarding interference provided in an embodiment of the present invention;

[0030] Figure 8(b) is a schematic diagram of the pulse compression output result of the optimized waveform under intermittent sampling and repeated forwarding interference provided in the embodiment of the present invention;

[0031] Figure 9(a) is a schematic diagram of the amplitude curve of the second-order statistical quantity of segmented pulse compression when each working segment is undisturbed, according to the embodiment of the present invention.

[0032] Figure 9(b) is a schematic diagram of the amplitude curve of the second-order statistic of segmented pulse compression when a few working segments are disturbed, according to an embodiment of the present invention.

[0033] Figure 9(c) is a schematic diagram of the amplitude curve of the second-order statistic of segmented pulse compression when most working segments are disturbed, according to the embodiment of the present invention. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Currently, countermeasures against intermittent sampling and forwarding interference are mainly considered from two dimensions: interference parameter estimation and waveform design.

[0036] Extensive research has been conducted on parameter estimation for intermittent sampling-forwarding interference. Zhou Chao et al. analyzed the pulse compression characteristics of this interference and proposed the interference slice width using the idea of ​​deconvolution. Yang Xiaopeng et al. proposed an estimation method based on short-time fractional Fourier transform, which can estimate interference parameters such as the number of slices, slice width, and frequency modulation slope. Zhou Chang et al. analyzed the mutual ambiguity characteristics after matched filtering of the interference and proposed a parameter estimation method based on Radon transform and least squares. Shang Dongdong et al. constructed a nonlinear optimization model of the interference and the receiving window function, and proposed an interference parameter estimation method based on the alternating direction multiplier method to extract the slice width and number.

[0037] In the design of orthogonal waveforms to counter intermittent sampling and forwarding interference, Zhou Chao et al. designed intra-pulse orthogonal phase-coded signals using radar signals not intercepted by jammers. During waveform design, they employed an immune genetic algorithm based on DNA encoding to achieve low autocorrelation sidelobes and cross-correlation peaks in the orthogonal waveforms. Zhou Chang et al., addressing the frequency domain characteristics of intermittent sampling and forwarding interference, designed intra-pulse orthogonal linear frequency modulation-phase-coded waveforms using a hybrid search algorithm based on genetic algorithms and simulated annealing. These waveforms simultaneously possess the advantages of Doppler insensitivity and low sidelobes. Dong Shuxian et al., addressing the time-domain discontinuity of intermittent sampling and forwarding interference, proposed a waveform design scheme involving intra-pulse linear frequency modulation-random frequency coding and inter-pulse frequency agility. Intra-pulse frequency coding enables mutual masking between different sub-pulses, while random inter-pulse carrier frequency transitions achieve mutual masking between different pulses.

[0038] However, existing research has the following problems: 1) The time-frequency analysis parameter estimation accuracy is low and it is easily affected by noise; 2) The intra-pulse frequency coding waveform is easily affected by the discrete effect and truncation effect during signal processing, which causes the energy of the interfered segment to overflow into the uninterrupted segment, resulting in a significant reduction in the anti-interference effect; 3) There is a lack of research on parameter estimation and interference suppression cognitive countermeasure system for intermittent sampling forwarding interference, that is, few scholars have studied the adaptive closed-loop system of "interference parameter estimation-radar waveform design-interference suppression".

[0039] To address the issues of parameter estimation, waveform countermeasures, and cognitive countermeasures against intermittent sampling forwarding interference (ISBN), this invention provides an ISBN suppression method based on intra-pulse waveform cognitive optimization design.

[0040] Please see Figure 1 and Figure 2 , Figure 1 This is a flowchart illustrating an intermittent sampling and forwarding interference suppression method based on intrapulse waveform cognitive optimization design provided by an embodiment of the present invention. Figure 2 This is a flowchart illustrating the implementation of an intermittent sampling and forwarding interference suppression method based on intra-pulse waveform recognition and optimization design, as provided in this embodiment of the invention. The intermittent sampling and forwarding interference suppression method based on intra-pulse waveform recognition and optimization design provided in this embodiment of the invention may include the following steps 1 to 7:

[0041] Step 1: Within one coherent processing time, the radar transmits a detection signal targeting the target using a preset waveform transmission method, and performs pulse compression, inter-pulse range synthesis, and range image stitching on the received, interfered signal to obtain a one-dimensional high-resolution range image; wherein, the preset waveform transmission method includes an intra-pulse linear frequency modulation-inter-pulse frequency agility waveform transmission method.

[0042] Specifically, the following description uses the preset waveform transmission method of intra-pulse linear frequency modulation-inter-pulse frequency agility as an example. However, the preset waveform transmission method in this embodiment is not limited to this. That is, the radar detection signal can adopt other waveform schemes, such as intra-pulse linear frequency modulation-inter-pulse frequency repetition frequency joint agility, etc. The goal of using linear frequency modulation signals within the pulse is to make full use of the pulse compression range profile distribution characteristics of intermittent sampling and forwarding interference. The waveform scheme between pulses can be arbitrarily set without affecting the parameter estimation to obtain better anti-interference and low intercept performance.

[0043] Specifically, step 1 may include the following steps:

[0044] Step 1.1: Within one coherent processing time, the radar transmits the detection signal S according to the waveform transmission mode of intra-pulse linear frequency modulation-inter-pulse frequency agility. t (i,t);

[0045]

[0046] Among them, S t (i,t) represents the i-th pulse signal transmitted by the radar, where the pulse signal is the detection signal i = 0, 1, ..., N-1, and N ≥ 1; rect(·) is the rectangular window function, t is the pulse fast time, and T p For pulse width, μ = B p / T p For the frequency modulation slope, B p f is the signal bandwidth. c The initial carrier frequency of the pulse is n, Δf is the frequency step value, and n is the frequency step value. i ∈{0,1,…,M-1} represents the i-th frequency modulation code, where M is the number of selectable frequency points.

[0047] Step 1.2: The radar performs down-conversion and low-pass filtering on the received interference-affected echo signal to obtain the baseband echo signal S. r (i,t) is subjected to pulse compression processing to obtain the pulse compression frequency domain response S. r-pc (i,f);

[0048] Step 1.2 may include:

[0049] Step 1.2.1: Based on the interference-affected echo signal received by the radar, which includes the target echo signal and the interference signal, the baseband target echo signal S of the i-th pulse is... tar (i,t) is represented as:

[0050]

[0051] in, R is the radial distance between the radar and the target. tarThe introduced delay, V r Let t be the radial velocity of the target relative to the radar. i =iT r is the interpulse slow time, and c is the speed of light;

[0052] Step 1.2.2: When the target's self-defense jammer adopts the intermittent sampling direct relay mode, the baseband jamming echo signal S of the i-th pulse is... J1 (i,t) is represented as:

[0053]

[0054] Where, N J T is the number of jammer slices for the target. J To determine the width of the interference slice, τ J The delay τ introduced by the radial distance between the radar and the jammer, in the case of a self-defense jammer. J =τ tar ;

[0055] Step 1.2.3: When the self-defense jammer adopts the intermittent sampling and repetitive forwarding mode, the baseband interference echo signal S of the i-th pulse is... J (i,t) is represented as:

[0056]

[0057] Among them, M J T represents the number of slice forwardings. u =(M J +1)T J The time interval for the jammer to intercept signals;

[0058] Step 1.2.4: Determine the echo signal model when M... J When the value is 1, the two interference modes are equivalent and exist. The baseband interference echo signal is uniformly represented by S. J (i,t) represents the baseband echo signal S. r The expression for (i,t) is:

[0059] S r (i,t)=S tar (i,t)+S J (i,t)+w(t);

[0060] Where w(t) is the variance of Complex Gaussian white noise;

[0061] Step 1.2.5: Set the frequency domain response of the compressed baseband echo signal pulse to S. r-pc(i,f), and expressed as:

[0062] S r-pc (i,f)=S tar-pc (i,f)+S J-pc (i,f)+w(f);

[0063] Where f is the fast time frequency, w(f) is the noise spectrum, and S is the frequency domain response of the target echo signal after pulse compression. tar-pc (i,f) is represented as:

[0064]

[0065] Frequency domain response S after pulse compression of interference signal J-pc (i,f) is represented as:

[0066]

[0067] Step 1.3, construct the velocity compensation function H(i,f; V) r ), for the frequency domain pulse compression response S r-pc (i,f) performs frequency domain velocity compensation;

[0068] Specifically, step 1.3 includes:

[0069] Step 1.3.1, assume the target radial velocity V r Provided by the system tracking module, the constructed velocity compensation function is as follows:

[0070]

[0071] Step 1.3.2, using H(i,f; V) r Multiply by S r-pc (i,f) performs frequency domain velocity phase compensation, and the compensation result is then subjected to IFFT to obtain the velocity-compensated time-domain pulse compression output result S. pc (i,t) represents the coarse-resolved range image, expressed by the formula:

[0072] S pc (i,t)=S tar-pc (i,t)+S J-pc (i,t)+w(t);

[0073] Among them, S tar-pc (i,t) represents the pulse compression output response of the target signal, expressed as:

[0074]

[0075] Among them, S J-pc (i,t) represents the pulse compression output response of the interference signal, expressed as:

[0076]

[0077] Wherein, according to sinc(μT) J (tm J T J )) item, M J Repeated forwarding will form M J There are several false target groups, and the time width of each group is 1 / μT. J In the formula A term at t = k / μT u +m J T J , An extreme value is formed at this point, indicating a false target, and the time interval between each false target is 1 / μT. u =1 / μ(M J +1)T J The amplitude is determined by the main lobe width being 1 / NμT. u The sinc function modulation results in a spurious target group containing 2M spurious targets. J +1. Subsequent steps will utilize the aforementioned feature information to extract feature pseudo-targets.

[0078] Step 1.4: Perform inter-pulse distance synthesis and range image stitching on the frequency domain velocity-compensated pulse compression output to obtain a one-dimensional high-resolution range image S. hrrp (e).

[0079] Specifically, step 1.4 includes:

[0080] Step 1.4.1, in this embodiment of the invention, the unambiguous distance range [0, 2π) is divided into M high-resolution distance units to obtain the distance discrete parameter q. r = 2πr / M, where r = 0, 1, ..., M-1; M ≥ 1;

[0081] Step 1.4.2, define the distance matched filter matrix as follows: in The matched filter for the r-th high-resolution range cell is represented as:

[0082]

[0083] Step 1.4.3, using the distance matched filter matrix Φ and the echo signal pulse compression output result S pc Multiplying by the transpose of (i,t) yields the inter-pulse coherent synthesis result S. coh (t,r), after performing range image stitching on the result, a one-dimensional high-resolution range image S with improved detail is obtained. hrrp(e), where e is the range gate sequence of the high-resolution range profile and there is Δt = 1 / B p is the sampling time interval, denotes the floor operator, then S hrrp (e) is expressed as:

[0084]

[0085] where, is the constant phase term, and mod(·) is the remainder operation.

[0086] Step 2: Perform peak extraction on the obtained one-dimensional high-resolution range profile to obtain the amplitude information and range information of all peak points;

[0087] Specifically, Step 2 includes: [[ID=2)]]

[0088] Step 2.1: Set half of the peak amplitude of the one-dimensional high-resolution range profile S hrrp (e) as the detection threshold K1, and use the detection threshold K1 to detect and discriminate the amplitudes A hrrp (e) corresponding to all high-resolution range cells;

[0089] Step 2.2: If A hrrp (e) ≥ K1, it is determined that there is a target on the e-th high-resolution range cell, and record its amplitude information A(i tar ) and range information R(i tar ), where i tar = 1, …, N tar ; N tar is the number of detected peak points;

[0090] Step 2.3: If A hrrp (e) < K1, it is determined that no target is detected on the e-th high-resolution range cell, and its relevant information is discarded;

[0091] Step 2.4: Finally, obtain the amplitude information A(1), A(2), …, A(N tar ) and range information R(1), R(2), …, R(N tar ).

[0092] Step 3: According to the primary and secondary false target characteristic information formed by the intermittent sampling and repeater jamming, extract the characteristic false targets of all detected peak points, and then estimate the interference parameter information including the slicing times, slicing width, and repeater times;

[0093] Specifically, for the intermittent sampling and direct repeater jamming, its pulse compression result shows a group of false targets, and there are 3 false targets in the group, and the time interval between each false target is 1 / μTu The two secondary false targets and the primary false target are equally spaced; the characteristics of intermittent sampling and repeated forwarding interference are related to the number of forwardings, M J Repeated forwarding will form M J There are several false target groups, and the time width of one group is 1 / μT. J The time interval between the main false targets in each false target group is 1 / μT. u =1 / μ(M J +1)T J They are evenly spaced.

[0094] Step 3 includes:

[0095] Step 3.1, take the set {A(1), A(2), ..., A(N)} tar )} , calculate the maximum value A(λ) in the distance difference ΔR(i) tar )=R(i tar )-R(λ), where λ is the target index corresponding to the maximum value, i tar =1,2,…,N tar ;

[0096] Step 3.2, if any parameter η satisfies the preset condition |ΔR(η)+ΔR(i) tar )| <R tol , then λ, i tar The target corresponding to η is a feature pseudo-target, and its corresponding target index is recorded; if no parameter η satisfies the preset condition, then let A(λ) = 0 and return to step 3.1; where η∈(1,2,…,N) tar ), R tol This is the distance tolerance error;

[0097] Step 3.3: Based on the target index and amplitude information of the characteristic pseudo-target, determine its forwarding type and forwarding count M. J ′;

[0098] The specific judgment rules are as follows: If the target index number is 3, and the amplitude of the secondary false target is approximately equal to the amplitude of the primary false target... The number of forwards is determined to be M. J =1, the interference type is intermittent sampling direct forwarding interference; for intermittent sampling repeated forwarding interference, if the amplitude of the main false target in each false target group is approximately equal and the target index number exceeds 3, then the forwarding number M is determined to be... J ′ equals the target index number of the main dummy target, and the interference type is intermittent sampling repeated forwarding interference;

[0099] Step 3.4, calculate the distance R of the feature false target. false =mean(|R(η)-R(λ)|+|R(i tar)-R(λ)|), and then estimate the slice width T. J ′, where mean(·) is the average operation;

[0100] Specifically, if it is intermittent sampling and direct forwarding interference, then let The estimated value T of the slice width is obtained. J If it is intermittent sampling and repeated forwarding interference, then let The estimated value T of the slice width is obtained. J ′.

[0101] Step 3.5, based on the calculated number of forwards M J ′ and slice width T J The estimated value of ′ is based on the number of slices N. J ′ and the number of forwards M J ′、Slice width estimate T J The relationship between ′ and pulse width is used to calculate an estimate N of the number of slices. J ′.

[0102] Wherein, the number of slices N J ′ and the number of forwards M J ′、Slice width estimate T J The relationship between ′ and pulse width is:

[0103]

[0104] Step 4: Using the estimated interference parameter information, based on the preset intra-pulse waveform scheme, transmit the cover segment signal during the interference interception period and the working segment signal during the interference forwarding period, while setting up a frequency isolation zone between the cover segment and the working segment; wherein, the preset intra-pulse waveform scheme is optimized based on the radio frequency protection concept, including the intra-pulse waveform scheme of intra-pulse linear frequency modulation-close-fit radio frequency protection Costas frequency coding;

[0105] Specifically, the following description uses the preset intra-pulse waveform scheme of intra-pulse linear frequency modulation-close-fit RF shielding Costas frequency encoding as an example. However, the preset intra-pulse waveform scheme in the embodiments of the present invention is not limited to this. For example, an intra-pulse alternating Costas encoding scheme can be adopted. The aim is to make the interference unable to intercept the working signal through the design of the intra-pulse waveform. At the same time, in order to reduce the influence of discrete effects and truncation effects in the signal processing process, a certain frequency isolation is achieved between the interfered segment and the uninterrupted segment.

[0106] Since the intrapulse waveform is continuous in the time domain, the intrapulse waveform is optimized using the close-fitting shield waveform design strategy in radio frequency shielding. Because the intermittent sampling jammer operates in an instant-slice mode, the estimated number of interference slices N can be used as a reference. J′、Slice width T J ′ and number of forwards M J The parameters are: during the jammer's sampling time, a high-frequency cover signal is transmitted; during the jammer's forwarding time, a low-frequency working signal is transmitted.

[0107] Specifically, step 4 includes:

[0108] Step 4.1: Based on the intra-pulse waveform scheme of intra-pulse linear frequency modulation-close-fitting RF shielding Costas frequency encoding, the intra-pulse waveform uses a frequency-encoded signal optimized based on RF shielding principles, while the inter-pulse waveform uses a frequency-agile signal with randomly varying frequency points. The total duration of a single pulse is determined to be T. p =N J ′×(M J ′+1)T J ′, the bandwidth of a single pulse is B p ;

[0109] The intra-pulse uses a frequency-encoded signal optimized based on the concept of radio frequency shielding, while the inter-pulse uses a frequency-agile signal with randomly changing frequency points to ensure that the designed waveform has good anti-interference and low interception performance.

[0110] Step 4.2, let the frequency offset of the cover segment relative to zero frequency be f. ass The signal expression for determining the masking segment of the i-th pulse is:

[0111]

[0112] Among them, T sub =T J ′ represents the time width of the intrapulse cover segment and the working segment, T u ′=(M J ′+1)T J ′ represents the time interval between each cover segment, μ = B sub / T sub B represents the frequency modulation slope of each segment. sub =B p / (N J ′×M J ′) represents the bandwidth of each segment;

[0113] Step 4.3, determine the signal expression for the working segment of the i-th pulse as follows:

[0114]

[0115] Where, α i (i sub ′)∈{0,1,…,N J ′×M J ′-1} represents the i-th pulse.sub ′(i sub ′=1,2,N J ′×M J Frequency modulation coding of ′) working segments, i sub ′=(m-1)(M J ′+1)+1+i sub , Δf sub =B sub The interval for segmented frequency steps;

[0116] In this embodiment of the invention, the working segment waveform design has the following characteristics: (1) the frequency code of each pulse is generated independently and randomly to ensure low interception performance; (2) the segments do not overlap in frequency, that is, the segments are theoretically orthogonal; (3) the working segment of a single pulse covers the entire frequency band, that is, it occupies a continuous frequency band.

[0117] Step 4.4: To ensure the orthogonality of the cover segment and the working segment, a frequency isolation zone is set between the cover segment and the working segment, satisfying f ass ≈1.5(N J ′×M J ′-1)Δf sub .

[0118] Step 5: After receiving the echo of the waveform after the pulse optimization design, the shield segment signal is not processed, and the working segment signal is subjected to segment pulse compression and segment decoupling to obtain the segment pulse compression result after segment decoupling. Then, the modulus-square mean square operation is performed on each segment in the segment pulse compression result to obtain the second-order statistics of each working segment of each pulse.

[0119] Specifically, based on the "stop-and-go" assumption, the target is at time t′ = iT r +(m-1)T u ′+i sub 'T sub The radial distance relative to the radar can be written as r = R tar -V r If t′, then the working signal of the i-th pulse echo signal can be written as:

[0120]

[0121] Step 5 of this embodiment of the invention may include:

[0122] Step 5.1: Perform down-conversion processing on the working segment signal to obtain the down-conversion processing result. in,

[0123]

[0124] In the echo signal processing, multiple down-conversions are required; that is, each segment being processed is down-converted to the fundamental frequency. The i-th pulse is then down-converted... sub The above equation is obtained after the working segments are reduced to the fundamental frequency.

[0125] The last term in the above equation is exp(j2π[(α) i (i sub ")-α i (i sub ′))Δf sub ]t) represents the remaining information after the pulse is down-converted between meridians and then down-converted to the other segments within the meridian;

[0126] Step 5.2, construct the piecewise matched filter s sub (t) Segmented pulse compression processing is performed to obtain the segmented pulse compressed frequency domain response. Step 5.2 includes:

[0127] Step 5.2.1, construct the piecewise matched filter s sub (t), represented as:

[0128]

[0129] Step 5.2.2, after performing FFT and frequency domain pulse compression on the working segment of the target baseband echo signal, the following is obtained:

[0130]

[0131] The above formula takes into account the orthogonality between the segmented signal that has not been reduced to the fundamental frequency and the matched filter, where the output of these segments in the matched filter is 0.

[0132] Step 5.3, Construct the range-coupled phase correction function eliminate The segmented distance coupling phenomenon exists in the pulse compression, and the segmented pulse compression result after distance coupling correction is obtained. Then, modulus-square operation is performed on the pulse compression output of each segment to obtain the second-order statistic E(i,i) of each pulse segment. sub ');include:

[0133] Step 5.3.1, Construct the range-coupled phase correction function The result of performing segmented distance coupling correction in the frequency domain is expressed as follows:

[0134]

[0135] Step 5.3.2, after IFFT, the fast-time signal obtained after pulse compression is the signal that has completed segmented pulse compression and segmented coupling correction, and it is represented as:

[0136]

[0137] Step 5.3.3: Perform modulo-mean-square calculation on the segmented pulse compression results to obtain the second-order statistics E(i,i) of each segment of each pulse. sub ′), represented as:

[0138]

[0139] Here, mean(·) is the mean operation, sum(·) is the sum operation, and |·| is the modulo operation.

[0140] Step 6: Using the minimum value of the second-order statistic as a benchmark, perform threshold discrimination on the statistics of each working segment to obtain the threshold discrimination results;

[0141] Specifically, step 6 includes:

[0142] Step 6.1, find the minimum value of each segment statistic:

[0143]

[0144] Where min(·) is the minimum value operation;

[0145] Step 6.2, with E min Based on this, the threshold is set as K2 = E. min +3dB, threshold discrimination is performed on the statistics of each segment of each pulse to obtain the threshold discrimination result P(i,i sub The result exceeding the threshold is recorded as 1, and the result not exceeding the threshold is recorded as 0.

[0146] Step 7: If the threshold discrimination result meets certain conditions, design the corresponding waveform processing scheme to obtain the real target information; otherwise, return to step 1 to update the interference parameters and waveform parameters.

[0147] Specifically, step 7 includes:

[0148] Step 7.1, if the threshold discrimination result P(i,i) sub If all of the above are 0, then the inter-segment synthesized signal y(i,t″) is processed by inter-pulse coherent synthesis to obtain a one-dimensional high-resolution range profile HRRP, thereby obtaining real target information;

[0149] Specifically, using the threshold discrimination result P(i,i) sub′) Determine if the working segment is affected by interference. If the statistics of each pulse segment do not exceed the set threshold K2, it means that the working segment is almost unaffected by interference. Then, the segment pulse compression results can be processed by inter-segment synthesis and inter-pulse coherent synthesis to obtain the true target information.

[0150] In one embodiment of the present invention, the inter-segment synthesis and inter-pulse coherent synthesis processes are as follows:

[0151] After downsampling, the i-th pulse is obtained. sub The segmented pulse compression results for each segment are as follows:

[0152]

[0153] Where t ds This is the fast time series after downsampling.

[0154] Assuming velocity V r Provided by the tracking module, construct the intrapulse velocity phase term compensation function H. sub (i sub ′), which can be represented as:

[0155]

[0156] Using the above formula to compensate for the intrapulse velocity phase term, the compensated segmented pulse compression result is as follows:

[0157]

[0158] Based on the waveform parameters of the intrapulse modulation, the unambiguous range for the distance dimension search is [0, c / 2Δf]. sub The search interval satisfies Δr sub ≤c / 2N sub Δf sub The unambiguous distance range is divided into G high-resolution distance units using this search interval, and r sub (g)=gΔr sub Let g = 0, 1, ..., G-1, and let Φ be the intrapulse distance composition matrix. sub =[ψ(r sub (0)),ψ(r sub (1)),…,ψ(r sub (G-1))], where:

[0159]

[0160] Using the above formula to synthesize the inter-segment distances, we obtain the synthesis result y(i,t″), which can be expressed as:

[0161]

[0162] After performing distance image stitching on the inter-segment synthesis results, the coherent processing of a single pulse can be completed.

[0163] After intra-pulse coherence processing, the fast time result of the i-th pulse is as follows:

[0164]

[0165] Where t″ is the distance-time variable after intrapulse processing, and Ω(t″) represents the output envelope after intrapulse coherent processing. Performing an FFT on the above equation yields:

[0166]

[0167] Construct distance travel compensation function H envelope (i,f), can be represented as:

[0168]

[0169] The time-domain echo signal of the frequency-agile radar after range migration correction and IFFT transformation is:

[0170]

[0171] Converting the above results into matrix form, we obtain the slow-time sampling vector at fast time t' as follows:

[0172] y(t″)=[y com (0,t″ r ),y com (1,t″ r ),…,y com (N-1,t″ r )];

[0173] The unambiguous range synthesis range of frequency-agile radar is It is divided into Q high-resolution range cells to obtain a range-resolution grid. Since the radar range resolution is Δr = c / 2MΔf, Q ≥ M is required here to ensure... Define the corresponding center velocity as V r The distance matching matrix of the Doppler channel is

[0174]

[0175] The final interpulse synthesis high-resolution range image HRRP result is as follows:

[0176] HRRP=y(t″)Ψ(V r );

[0177] Then, the true information of the target is obtained through CFAR detection.

[0178] Step 7.2, if the threshold discrimination result P(i,i) sub If less than half of the values ​​of ') are 1, then that part is segmented and removed, and then inter-pulse coherent synthesis is performed to obtain the true target information.

[0179] Specifically, if the statistics of a few segments in each working segment of each pulse exceed the set threshold K2, it indicates that some segments are affected by interference. These segments can be removed during the intra-pulse segmentation process. That is, the synthesis process of these segments is discarded in the intra-pulse segmentation synthesis process, so as to obtain a larger signal-to-interference ratio gain with a smaller signal-to-noise ratio loss.

[0180] Step 7.3, if the threshold discrimination result P(i,i) sub If more than half of the values ​​of ') are 1, then repeat steps 1 to 5 to update the interference parameters and waveform parameters.

[0181] If the statistics of most segments in each working segment of each pulse exceed the set threshold K2, it indicates that the interference parameters may need to be adjusted. If the inter-pulse synthesis operation is still performed by removing the interfered segments, it will lead to increased sparsity of the intra-pulse spectrum, which will seriously affect the detection performance of the waveform. At this time, the waveform parameters need to be updated, that is, the operation of steps 1 to 5 is repeated.

[0182] Among them, the threshold discrimination results corresponding to steps 7.1 and 7.2 meet certain conditions, while the threshold discrimination results corresponding to step 7.3 do not meet these certain conditions.

[0183] In one optional implementation, the processing step 7 where multiple segments exceed the threshold can also be handled as follows: if only a few pulses have multiple segments exceeding the threshold, the corresponding pulses can be removed, and inter-pulse synthesis can be performed on the remaining pulses; if multiple segments of most pulses exceed the threshold, the interference parameters can be re-estimated. Specific details are not provided here.

[0184] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0185] 1. This invention uses an "intra-pulse linear frequency modulation-inter-pulse frequency agility" waveform to estimate interference parameters. It can utilize the inter-pulse synthesis of frequency agility waveforms with large bandwidth to obtain more refined range resolution. Combined with the one-dimensional range profile features after intermittent sampling direct forwarding or repeated forwarding interference pulse compression and coherent processing, high-precision estimation of interference parameters can be achieved.

[0186] 2. Based on interference parameter estimation, this invention optimizes the intra-pulse waveform using a close-fitting shielding waveform design strategy in radio frequency (RF) shielding. A high-frequency shielding signal is transmitted during the jammer's sampling time, and a low-frequency operating signal is transmitted during the jammer's forwarding time. To ensure the designed waveform has good anti-interference performance, the intra-pulse waveform uses a frequency-encoded signal optimized based on RF shielding principles. Each pulse's frequency code is randomly generated, non-overlapping, and covers the entire frequency band. Inter-pulse waveforms use frequency-agile signals with randomly varying frequency points.

[0187] 3. This invention provides an intermittent sampling forwarding interference suppression method based on intra-pulse waveform cognitive optimization design. Based on interference parameter estimation, it utilizes an optimized waveform processing scheme for interference suppression. Simultaneously considering the possibility of interference parameter changes, it uses the working segment energy of the optimized waveform as the evaluation criterion, adaptively adjusting the waveform transmission and processing strategies. This enables dynamic adjustment of both interference and waveform parameters, forming an adaptive closed-loop system for intermittent sampling forwarding interference parameter interference and suppression.

[0188] To demonstrate the effectiveness of this invention, the following simulation experiments are conducted for further illustration.

[0189] (1) Simulation conditions:

[0190] like Figure 3 As shown, the radar transmits a waveform of "intra-pulse linear frequency modulation - inter-pulse frequency agility", with an initial carrier frequency f. c =10GHz, pulse duration T p =80μs, pulse bandwidth B p =20MHz, pulse repetition period T r =160μs, frequency step interval Δf = 10MHz, number of pulses in one CPI is N = 20, number of selectable frequency points is M = 20, frequency code is n0,n1,…,n N-1 The receiver noise follows a discrete, independent, and identically distributed pattern on {0,1,…,M-1}, and its variance is... The complex Gaussian distribution has a signal-to-noise ratio (SNR) of 0 dB.

[0191] Radial distance R of the jammer relative to the radar tar =2100m, the radial velocity of the jammer relative to the radar is V r = 40m / s. The intermittent sampling jammer in direct forwarding mode has a slice width T. J =0.05T p Number of forwards M J =1, number of slices N J =10; In repetitive forwarding mode, the slice width T of the intermittent sampling jammer is... J =0.08T p Number of forwards MJ =4, number of slices N J =3, the interference noise ratio is JNR=20dB in both modes.

[0192] Based on the estimation of interference type and interference parameters, the intra-pulse waveform is optimized using the close-fitting shielding waveform design strategy in radio frequency shielding. The optimized waveform for intermittent sampling direct forwarding interference is shown in Figure 4(a); the optimized waveform for intermittent sampling repeated forwarding interference is shown in Figure 4(b).

[0193] (2) Simulation content and results:

[0194] Simulation 1: Under the intermittent sampling and direct forwarding interference, the coarse-resolution range image after pulse compression and the high-resolution range image after inter-pulse range synthesis of the "intra-pulse linear frequency modulation-inter-pulse frequency agility" signal pulse are simulated. The results are shown in Figure 5(a) and Figure 5(b), respectively. It can be seen from the two figures that (1) due to the synthesis of inter-pulse bandwidth, the range resolution is significantly improved, which can improve the range resolution of the primary and secondary false targets by 1 / 2 μT. J The estimation accuracy, thereby improving the accuracy of T J (2) JNR is significantly improved, which improves the accuracy of the above parameter estimation.

[0195] Simulation 2: Under the intermittent sampling and repeated forwarding interference, the coarse-resolution range image after pulse compression and the high-resolution range image after inter-pulse range synthesis of the "intra-pulse linear frequency modulation-inter-pulse frequency agility" signal pulse are shown in Figure 6(a) and Figure 6(b), respectively. It can be seen from the two figures that (1) the inter-pulse range synthesis has a suppressive effect on multiple secondary false targets near the peak of the main false target formation, that is, the peak of the main false target formation can be detected more clearly, and the number of forwardings N can be obtained. J (2) Due to the synthesis of inter-pulse bandwidth, the distance resolution is significantly improved, which can improve the estimation of parameter T. J (3) JNR is significantly improved, which improves the accuracy of the above parameter estimation.

[0196] Simulation 3: The time-frequency diagram of the echo signal of the pulse-optimized design waveform under the simulation of intermittent sampling direct forwarding interference is shown in Figure 7(a). This figure shows that the intermittent sampling forwarding interference signal is concentrated in the cover segment and has a certain degree of orthogonality with the working segment. Processing only the working segment is sufficient to directly suppress the intermittent sampling direct forwarding interference at the receiver. The coherent processing result of the working segment is shown in Figure 7(b). This figure shows that the interference signal is suppressed and the real target is revealed.

[0197] Simulation 4. The time-frequency diagram of the echo signal of the pulse optimization design waveform under the simulation of intermittent sampling and repeated forwarding interference is shown in Figure 8(a). It can be seen from the figure that the intermittent sampling and repeated forwarding interference signal is concentrated in the cover segment. Only the working segment needs to be processed to directly suppress the intermittent sampling and repeated forwarding interference at the receiving end. The coherent processing result of the working segment is shown in Figure 8(b).

[0198] Simulation 5: After segmenting and pulse compression of each working segment, the second-order statistical amplitude curves of each segment are simulated. The second-order statistical amplitude curves of each working segment without interference are shown in Figure 9(a). At this time, inter-segment synthesis and inter-pulse synthesis processing can be directly performed on the working segments. The second-order statistical amplitude curves of a few working segments with interference are shown in Figure 9(b). At this time, the interfering working segments can be removed before inter-segment synthesis and inter-pulse synthesis processing can be performed. The second-order statistical amplitude curves of most working segments with interference are shown in Figure 9(c). At this time, parameter estimation needs to be performed again.

[0199] The above description is merely a preferred embodiment of the present invention and is 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 are included within the scope of protection of the present invention.

Claims

1. An intermittent sampling and forwarding interference mitigation method based on intra-pulse waveform cognitive optimization design, characterized in that, include: Step 1: Within one coherent processing time, the radar transmits a detection signal targeting the target using a preset waveform transmission method, and performs pulse compression, inter-pulse range synthesis, and range image stitching on the received interfered signal to obtain a one-dimensional high-resolution range image; wherein, the preset waveform transmission method includes an intra-pulse linear frequency modulation-inter-pulse frequency agility waveform transmission method. Step 2: Perform peak extraction on the obtained one-dimensional high-resolution distance image to obtain the amplitude and distance information of all peak points; Step 3: Based on the primary and secondary false target feature information formed by intermittent sampling and forwarding interference, feature false targets are extracted from all detected peak points, and then interference parameter information including the number of slices, slice width and forwarding number is estimated. Step 4: Using the estimated interference parameter information, based on the preset intra-pulse waveform scheme, transmit the cover segment signal during the interference interception period and the working segment signal during the interference forwarding period, while setting a frequency isolation zone between the cover segment and the working segment; wherein, the preset intra-pulse waveform scheme is optimized based on the radio frequency protection concept, including the intra-pulse waveform scheme of intra-pulse linear frequency modulation-close-fit radio frequency protection Costas frequency coding; Step 5: After receiving the echo of the waveform after the pulse optimization design, the shield segment signal is not processed, and the working segment signal is subjected to segment pulse compression and segment decoupling to obtain the segment pulse compression result after segment decoupling. Then, the modulus-square mean square operation is performed on each segment in the segment pulse compression result to obtain the second-order statistics of each working segment of each pulse. Step 6: Using the minimum value of the second-order statistic as a benchmark, perform threshold discrimination on the statistics of each working segment to obtain the threshold discrimination results; Step 7: If the threshold discrimination result meets certain conditions, design the corresponding waveform processing scheme to obtain the real target information; otherwise, return to step 1 to update the interference parameters and waveform parameters.

2. The intra-pulse waveform-aware cognitive optimization design based intermittent sampling and forwarding interference mitigation method of claim 1, wherein, Step 1 includes: Step 1.1, within a coherent processing interval, the radar transmits a probing signal according to a waveform transmitting mode of intra-pulse linear frequency modulation-inter-pulse frequency agility ; ； in, For the radar transmission of the first A pulse signal, the pulse signal is the detection signal. , ; For rectangular window functions, For rapid intravascular coagulation, The pulse width. For frequency modulation slope, For signal bandwidth, The initial carrier frequency of the pulse. This is the frequency step value. For the first One frequency modulation code, Number of selectable frequency points ; Step 1.2: The radar performs down-conversion and low-pass filtering on the received interference-affected echo signal to obtain the baseband echo signal. The pulse compression frequency domain response is obtained by performing pulse compression processing on it. ; Step 1.3, Construct the velocity compensation function For frequency domain pulse compression response Frequency domain velocity compensation is performed; among which, For fast time frequency; The radial velocity of the target relative to the radar; Step 1.4: Perform inter-pulse distance synthesis and range image stitching on the frequency domain velocity-compensated pulse compression output to obtain a one-dimensional high-resolution range image. ;in, This is a range gate sequence for high-resolution range images.

3. The method of claim 2, wherein, Step 1.2 includes: Step 1.2.1: Based on the interference-affected echo signal received by the radar, which includes the target echo signal and the interference signal, the first... Baseband target echo signal of one pulse Represented as: ； in, Radial distance between radar and target The introduced delay, The radial velocity of the target relative to the radar. The slow pulse duration, At the speed of light, The pulse repetition period; Step 1.2.2: When the target's self-defense jammer adopts the intermittent sampling direct relay mode, the first... Baseband interference echo signal of one pulse Represented as: ； in, The number of times the jammer is sliced ​​for the target. To interfere with slice width, The delay introduced by the radial distance between the radar and the jammer, in the case of a self-defense jammer. ; Step 1.2.3: When the self-defense jammer adopts the intermittent sampling and repeated forwarding mode, the first... Baseband interference echo signal of one pulse Represented as: ； wherein, is the number of slice forwarding, is the time interval for signal interception by the jammer; Step 1.2.4, determine the echo signal model of intermittent sampling direct forwarding interference and intermittent sampling repeated forwarding interference when... The two interference modes are equivalent and exist. The baseband interference echo signal is unified using This indicates that the baseband echo signal was obtained. The expression is: ； in, The variance is Complex Gaussian white noise; Step 1.2.5, set the frequency domain response of the baseband echo signal after pulse compression as and is expressed as: ； wherein is the fast time frequency, is the noise spectrum, the frequency domain response of the target echo signal after pulse compression is represented as: ； Frequency domain response of the interference signal after pulse compression is represented as: 。 4. The method of claim 3, wherein, Step 1.3 includes: Step 1.3.1, assuming target radial velocity Given by the system tracking module, the velocity compensation function is constructed as: ； Step 1.3.2, using Multiply Frequency-domain velocity-phase compensation is performed, and the compensation result is then subjected to IFFT to obtain the velocity-compensated time-domain pulse compression output. , representing the coarse-resolved range image, is expressed by the formula: ； wherein The pulse pressure output response of the target signal is denoted as: ； wherein The impulse output response for the interference signal is denoted as ； Among them, according to item, Repeated forwarding will form There are several false target groups, and the time width of each group is... In the formula A , An extreme value is formed at a certain point, which is a false target, and the time interval between each false target is... The amplitude is from the width of the main lobe to of Function modulation, a group of false targets contains a number of false targets. .

5. The intermittent sampling and forwarding interference suppression method based on intra-pulse waveform cognitive optimization design according to claim 4, characterized in that, Step 1.4 includes: Step 1.4.1, define the unambiguous distance range. Divided into A high-resolution range cell is used to obtain the range discretization parameters. ,in, ; Step 1.4.2, define the distance matched filter matrix as follows: ,in , Indicates the first A matched filter with a high-resolution range cell is represented as: ； Step 1.4.3, using the distance matched filter matrix Echo signal pulse compression output results Multiplying by the transpose yields the result of inter-pulse coherent synthesis. After performing range image stitching on the result, a one-dimensional high-resolution range image with improved detail is obtained. ,in For high-resolution range images, the range gate sequence has , The sampling time interval, The floor operator indicates the rounding down operator. Represented as: ； wherein is a constant phase term, is a modulo operation.

6. The method of claim 5, wherein, Step 2 includes: Step 2.1, convert the one-dimensional high-resolution range image The detection threshold is set to half of the peak amplitude. To detect threshold Amplitude corresponding to all high-resolution range cells Perform detection and judgment; Step 2.2, if Then determine the first A target exists within a high-resolution range cell; its amplitude information is recorded. and distance information ,in ; The number of peak points detected; Step 2.3, if Then determine the first If no target is detected in a high-resolution range cell, its relevant information is discarded. Step 2.4: Finally, obtain the amplitude information of all threshold points. and distance information .

7. The method of claim 6, wherein, Step 3 includes: Step 3.1, retrieve the set The maximum value in Calculate the distance difference ,in, The target index corresponding to the maximum value. ; Step 3.2, if there are parameters Meets preset conditions ,but , and The corresponding target is the feature pseudo-target, and its corresponding target index is recorded; if there are no parameters... If the preset conditions are met, then let Return to step 3.1; where, , This is the distance tolerance error; Step 3.3: Based on the target index and amplitude information of the characteristic pseudo-target, determine its forwarding type and forwarding count. ; Step 3.4, compute feature false target distance , and then estimate slice width where, is an averaging operation; Step 3.5, based on the calculated number of forwards... and slice width The estimated value is based on the number of slices. With the number of reposts Slice width estimate The relationship between pulse width and the estimated number of slices is calculated. .

8. The method of claim 7, wherein, Step 4 includes: Step 4.1: Based on the intra-pulse waveform scheme of intra-pulse linear frequency modulation-close-fitting RF shielding Costas frequency coding, the intra-pulse waveform uses a frequency-coded signal optimized based on RF shielding principles, while the inter-pulse waveform uses a frequency-agile signal with randomly varying frequency points. The total duration of a single pulse is determined to be... The bandwidth of a single pulse is ; Step 4.2, let the frequency offset of the cover segment relative to zero frequency be... Determine the first The signal expression for the masking segment of each pulse is: ； wherein, is the time width of the overhand section and the working section, is the time interval between the overhand sections, is the frequency modulation slope of each section, is the bandwidth of each section; Step 4.3, determining the signal expression of the working section of the the nth pulse is: ； in, Indicates the first The pulse number Frequency modulation coding of each working segment , The interval for segmented frequency steps; Step 4.4, set frequency isolation zone between shelter segment and working segment, meet .

9. The intra-pulse waveform cognizant optimal design based intermittent sampling and forwarding interference mitigation method of claim 8, wherein, Step 5 includes: Step 5.1, down-conversion processing is performed on the work segmentation signal to obtain a down-conversion processing result of the work segmentation signal ; wherein, ； Among them, the last term of the above formula This indicates the remaining information after the pulse is down-converted between meridians and then down-converted to the other segments within the meridian; Step 5.2, Construct a piecewise matched filter right Segmented pulse compression processing is performed to obtain the segmented pulse compressed frequency domain response. ;include: Step 5.2.1, constructing a segment matched filter is represented as: ； Step 5.2.2, after performing FFT and frequency domain pulse compression on the working segment of the target baseband echo signal, the following is obtained: ； Step 5.3, Construct the range-coupled phase correction function ,eliminate The segmented distance coupling phenomenon exists in the pulse compression, and the segmented pulse compression result after distance coupling correction is obtained. The second-order statistics of each pulse segment are obtained by performing modulo-square operation on the pulse compression output of each segment. ;include: Step 5.3.1, constructing the distance-coupling phase correction function The frequency domain segmented distance-coupling correction is performed, the result of which is represented as: ； Step 5.3.2, after IFFT, the fast-time signal obtained after pulse compression is the signal that has completed segmented pulse compression and segmented coupling correction, and it is represented as: ； Step 5.3.

3. Perform the module square operation on the segmented pulse pressure results to obtain the second order statistics of each segment of each pulse is expressed as: ； wherein, is a mean operation, is a sum operation, is a modulo operation.

10. The method of claim 9, wherein, Step 6 includes: Step 6.1, find the minimum value of each segment statistic: ； wherein min operation; Step 6.2, with Based on this, the threshold is set as follows: Threshold discrimination is performed on the statistics of each segment of each pulse to obtain the threshold discrimination results. Results exceeding the threshold are recorded as 1, and results not exceeding the threshold are recorded as 0. Accordingly, step 7 includes: Step 7.1, if the threshold discrimination result If all are 0, then the signal after inter-segment synthesis... One-dimensional high-resolution range image is obtained by performing inter-pulse coherent synthesis. In order to obtain the true target information; Step 7.2, if the threshold discrimination result If less than half of the values ​​are 1, then that segment is removed and inter-pulse coherent synthesis is performed to obtain the true target information. Step 7.3, if the threshold decision result is more than half of 1, then the operation of steps 1 to 5 is repeated, and the interference parameter and the waveform parameter are updated.

Images