Multi-main-lobe intermittent sampling interference resisting method for time sequence design based on greedy search

Abstract

The invention discloses a greedy search-based time sequence design anti-multi-main-lobe intermittent sampling interference method, which comprises the following steps of: firstly, establishing a mathematical model of an orthogonal shield sub-pulse and detection sub-pulse structure, and then establishing a signal model of a radar receiving waveform in a scene that a plurality of targets and a plurality of interference sources transmit different parameters; and designing a radar waveform value evaluation function based on echo frequency spectrum energy on the basis of the model, carrying out iterative search on a radar survival window under a greedy search strategy by using the value function, designing a radar waveform time sequence under the survival window, and generating orthogonal shield and detection waveforms to carry out anti-interference detection. The method disclosed by the invention is excellent in the aspect of adapting to interference conditions in various different parameter scenes, can adapt to a scene with multiple different parameter intermittent sampling interference superposition and relatively high interference energy, has self-adaptability for scene change, has remarkable feasibility and practicability in engineering implementation, and is suitable for large-scale popularization and application. And the method has high engineering application value.

Description

Technical Field

[0001] The invention belongs to the technical field of signal processing, and in particular relates to a method for resisting multi-main-lobe intermittent sampling interference by timing design based on greedy search. Background Art

[0002] With the advancement of digital radio frequency storage technology, intermittent sampling interference has been proposed, which can intermittently intercept and sample radar signal fragments and forward the sampled fragments according to certain rules. Therefore, this interference has a strong correlation with the radar signal and can obtain partial coherent gain after pulse compression in the radar receiver, resulting in a large number of false targets, which significantly reduces the radar detection performance.

[0003] At present, some research results have been developed to combat intermittent sampling interference, which can be divided into three categories: the first category is to distinguish the interference and target echo in the transform domain and filter out the interference with a filter. The literature "C.Niu, Q.Lin, Y.Ma, M.Duan and H.Zhang, 'An intermittent sampling and forwarding interferencesuppression method based on intra-pulse frequency-time-delay agile waveform, '2023 3rd International Conference on Neural Networks, Information and Communication Engineering, Guangzhou, China, Feb.2023, pp.536-541" uses frequency-time-delay agile waveform to increase the distinction between target echo and interference waveform, uses iterative threshold algorithm to determine echo segments in the time-frequency domain, and uses combined sub-pulse filtering and time domain filtering to filter out interference overlapping with echo segments. However, this method will also lose the target signal. When multiple interferences cover the target echo, this type of method fails. The second type of method is to assume that the precise interference parameters are known, and use the parameters to jointly design the transmission waveform and filter to filter out the interference. The literature "K. Zhou, D. Li, Y. Su and T. Liu, 'Joint design of transmit waveform and mismatch filter in the presence of interrupted sampling repeater jamming, 'IEEE Signal Processing Letters, vol. 27, pp. 1610-1614, Sept. 2020" jointly designs radar waveforms and mismatch filters by using Lagrange multiplier method and alternating direction multiplier method to minimize the integrated sidelobe level of the target echo and the integrated level of the interference signal. However, when multiple interference signals with different parameters are mixed, the precise parameters are difficult to obtain. The third method is to extract the features of the interference and target echoes after their respective signal processing to identify false targets caused by interference.The literature "W.Wu J.Zou J.Chen S.Xu and Z.Chen, 'False-target recognition against interrupted-sampling repeater jamming based on integration decomposition,' IEEE Transactions on Aerospace and Electronic Systems, vol.57, pp.2979-2991, Oct.2021" decomposes the integral of the pulse compression result and identifies the target and false target peaks by the variance difference with the target echo signal caused by the discontinuity of intermittent sampling interference. However, when the interference energy is strong, the interference sidelobe will drown the target peak, making it difficult to obtain target information. Summary of the invention

[0004] To solve the above technical problems, the present invention provides a method for resisting multi-mainlobe intermittent sampling interference by timing design based on greedy search, which has fast online dynamic learning characteristics, does not require precise interference parameter estimation, and is still effective in the case of multiple interferences and high interference energy.

[0005] The technical solution adopted by the present invention is: a method for resisting multi-main lobe intermittent sampling interference based on greedy search timing design, and the specific steps are as follows:

[0006] S1. Construct a mathematical model of the orthogonal shielding sub-pulse and detection sub-pulse structure;

[0007] S2. Based on step S1, a radar receiving waveform model in a multi-target multi-interference scenario is constructed;

[0008] S3. Design radar waveform value evaluation function based on echo spectrum energy;

[0009] S4, based on step S3, using a greedy search framework, searching for the radar survival window and optimizing the launch timing;

[0010] S5. Based on the transmission timing optimized and designed in step S4, a linear frequency modulation waveform orthogonal in the frequency domain is generated for shielding and detection to perform anti-interference detection.

[0011] Furthermore, the step S1 is specifically as follows:

[0012] Radar transmit waveform T (t) is expressed as follows:

[0013]

[0014] Among them, t∈[0,∞) represents the time variable, s(t) represents the detection waveform, and Represents the protection waveform, and the expressions are as follows:

[0015]

[0016] Where rect(·) represents the rectangular window function, {B1,f1} and {B2,f2} represent the bandwidth and carrier frequency of the shielding sub-pulse and the detection sub-pulse respectively, and T s1 ,T d and T s2 Respectively s(t) and The pulse width.

[0017] The frequency difference Δf between the shielding sub-pulse and the detection sub-pulse satisfies the following relationship, which is expressed as follows:

[0018] Δf=|f1-f2|≥(B1+B2) / 2.

[0019] Time series collection of radar waveforms The expression is as follows:

[0020]

[0021] Among them, T p It represents the pulse width of radar transmitting waveform s(t), Td1 and Td2 represent the upper and lower limits of detection pulse width respectively. Cardinality The expression is as follows:

[0022]

[0023] in, f s represents the sampling rate, Indicates a round-down operation. The w distribution is labeled w i ,i=1,2,…,N w .

[0024] Furthermore, the step S2 is specifically as follows:

[0025] Set existence N T targets and N J Interference source, nth T =1,2,…,N T The distance and speed of the target are and No.n J =1,2,…,N J The distance and speed of the interference source are and

[0026] Radar receiving waveform R (t) is composed of target echo, interference and noise, and its expression is as follows:

[0027]

[0028] Among them, λ and c represent the wavelength of the radar transmission waveform and the propagation speed of electromagnetic waves respectively. Respectively represent the nth T The target echo and the nth J The complex amplitude of the interference waveform, represents the complex domain, Indicates the nth J The interference waveform after down conversion, n(t) represents the Gaussian white noise signal.

[0029] The interference in the radar receiving waveform includes three types of intermittent sampling interference: intermittent sampling direct forwarding J D (t), intermittent sampling and repeated forwarding J P (t) and intermittent sampling cyclic forwarding J C (t) interference, the expressions are as follows:

[0030] J D (t) = g1(tT L ),

[0031]

[0032] Among them, T L and T S Respectively represent the sampling duration and sampling interval, Indicates the number of forwarding times. Indicates the number of sampling times. p Indicates the jammer intercepted waveform s I (t) is the pulse width. g1(t) and The expressions are as follows:

[0033]

[0034] Among them, s I (t) = s T (t-T0) represents the radar waveform intercepted by the jammer, T0 represents the start sampling time of the jammer, and the time when the radar waveform is intercepted is taken.

[0035] Furthermore, the step S3 is specifically as follows:

[0036] The value evaluation function v(w) of the time series w is defined as follows:

[0037]

[0038] Where v1(w) and v2(w) represent the anti-interference value and detection energy value respectively, the measurement factor ρ1<0.1, the energy factor ρ2>0, and sgn(·) represents the sign function; E s and E d They represent the frequency band energy of the shielding sub-pulse and the detection sub-pulse respectively, and the expressions are as follows:

[0039]

[0040] in, represents the frequency domain variable, represents the real number domain, S(f) represents the echo s R The spectrum of (t), B s =(f1-Δf / 2,f1+Δf / 2),B d =(f2-Δf / 2,f2+Δf / 2).

[0041] Furthermore, the step S4 is specifically as follows:

[0042] S41, initializing radar survival window;

[0043] First, initialize the interaction cycle number l = 0, the value function V(w) = 0,

[0044] Then generate the time series w according to the ε-greedy strategy l , the expression is as follows:

[0045]

[0046] Among them, ε∈[0,1] is a constant, the random variable ξ obeys the [0,1] uniform distribution, and the probability distribution function P(k=i) of the random variable k is expressed as follows:

[0047]

[0048] S42, the radar transmits the combined shield and detection pulses according to the window, generates the echo signal and calculates the echo spectrum;

[0049] Radar based on w l Generate a transmit waveform and get the echo s R (t), calculate the echo spectrum S(f).

[0050] S43. Calculate the survival window value, i.e., the evaluation value v(wl), abbreviated as v l ;

[0051] S44, value function update;

[0052] Update the value function of the lth iteration, the expression is as follows:

[0053]

[0054] Among them, the discount factor 0<γ<1.

[0055] S45, greedy strategy selects a new window;

[0056] Let l = l + 1, if Convergence, output optimized timing Otherwise return to step S41.

[0057] Beneficial effects of the present invention: The method of the present invention first establishes a mathematical model of the structure of orthogonal cover sub-pulses and detection sub-pulses, then establishes a signal model of radar receiving waveforms in scenarios with multiple targets and multiple interference sources emitting different parameters, and designs a radar waveform value evaluation function based on echo spectrum energy based on the model, and uses the value function to iteratively search for radar survival windows under a greedy search strategy, and designs radar waveform timing under this survival window to generate orthogonal cover and detection waveforms for anti-interference detection. The method of the present invention performs well in adapting to interference situations under a variety of different parameter scenarios, can adapt to scenarios with multiple different parameter intermittent sampling interference superposition and high interference energy, and is adaptive to scene changes, has significant feasibility and practicality in engineering implementation, and has high engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 The present invention provides a flow chart of a method for resisting multi-mainlobe intermittent sampling interference by timing design based on greedy search.

[0059] Figure 2 Schematic diagram of the waveform structure of orthogonal cover and detection sub-pulses in an embodiment of the present invention.

[0060] Figure 3 Schematic diagram of a timing design framework based on greedy search in an embodiment of the present invention.

[0061] Figure 4 Schematic diagram of the neutron pulse width design process in the embodiment of the present invention

[0062] Figure 5 Schematic diagram of anti-interference performance analysis in an embodiment of the present invention. DETAILED DESCRIPTION

[0063] The method of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0064] like Figure 1 As shown, a flow chart of a method for resisting multi-main lobe intermittent sampling interference based on greedy search timing design of the present invention is shown, and the specific steps are as follows:

[0065] S1. Construct a mathematical model of the orthogonal shielding sub-pulse and detection sub-pulse structure;

[0066] S2. Based on step S1, a radar receiving waveform model in a multi-target multi-interference scenario is constructed;

[0067] S3. Design radar waveform value evaluation function based on echo spectrum energy;

[0068] S4, based on step S3, using a greedy search framework, searching for the radar survival window and optimizing the launch timing;

[0069] S5. Based on the transmission timing optimized and designed in step S4, a frequency domain orthogonal linear frequency modulation waveform is generated for cover and detection to perform anti-interference detection (ie, anti-interference detection is performed using orthogonal cover and detection waveforms).

[0070] In this embodiment, the step S1 is specifically as follows:

[0071] The waveform structure of orthogonal cover and detection sub-pulse is as follows Figure 2 As shown, the radar transmits waveform s T (t) is expressed as follows:

[0072]

[0073] Among them, t∈[0,∞) represents the time variable, s(t) represents the detection waveform, and Represents the protection waveform, and the expressions are as follows:

[0074]

[0075] Where rect(·) represents the rectangular window function, {B1,f1} and {B2,f2} represent the bandwidth and carrier frequency of the shielding sub-pulse and the detection sub-pulse respectively, and T s1 ,T d and T s2 Respectively s(t) and In this embodiment, B1 = B2 = 5MHz, f1 = 15MHz, f2 = -15MHz, T s1 +T d +T s2 =10μs.

[0076] In order to ensure the orthogonality of the shielding sub-pulse and the detection sub-pulse, the frequency difference Δf between the shielding sub-pulse and the detection sub-pulse satisfies the following relationship, which is expressed as follows:

[0077] Δf=|f1-f2|≥(B1+B2) / 2.

[0078] Time series collection of radar waveforms The expression is as follows:

[0079]

[0080] Among them, T p represents the pulse width of the radar transmission waveform s(t), T d1 and T d2 Respectively represent the upper and lower limits of the detection pulse width. Cardinality The expression is as follows:

[0081]

[0082] in, f s represents the sampling rate, Indicates a floor operation.

[0083] The w distribution is labeled

[0084] In this embodiment, step S2 is specifically as follows:

[0085] Set existence N T targets and N J Interference source, nth T =1,2,…,N T The distance and speed of the target are and No.n J =1,2,…,N J The distance and speed of the interference source are and

[0086] In this embodiment, there is a target carrying a self-defense jammer, whose distance R and speed v are 200 km and 300 m / s respectively, that is, N T =N J =1, Considering that the radar cross-section of the jammer is small, its echo is ignored. The radar receiving waveform s in this embodiment is R (t) is composed of target echo, interference and noise, and its expression is as follows:

[0087] s R (t) = As T (t-2R / c)exp(j4πvt / λ)+BJ(t)+n(t)

[0088] Among them, λ and c represent the wavelength of radar emission waveform and the propagation speed of electromagnetic wave respectively. They represent the complex amplitudes of the target echo and the interference waveform respectively, J(t) represents the interference waveform after down-conversion, and n(t) represents the Gaussian white noise signal.

[0089] The interference in the radar receiving waveform includes three types of intermittent sampling interference: intermittent sampling direct forwarding J D (t), intermittent sampling and repeated forwarding J P (t) and intermittent sampling cyclic forwarding interference J C (t), the expressions are as follows:

[0090] J D (t) = g1(tT L ),

[0091]

[0092] Among them, T L and T S Respectively represent the sampling duration and sampling interval, Indicates the number of forwarding times. Indicates the number of sampling times. p Indicates the jammer intercepted waveform s I (t) is the pulse width. g1(t) and The expressions are as follows:

[0093]

[0094] Among them, s I (t) = s T (t-T0) represents the radar waveform intercepted by the jammer, T0 represents the start sampling time of the jammer, and the time when the radar waveform is intercepted is taken.

[0095] This embodiment only considers intermittent sampling repeated forwarding interference J P (t), where the sampling time is T L = 1μs and sampling interval T S =4μs, forwarding times Sampling times

[0096] In this embodiment, step S3 is specifically as follows:

[0097] The value evaluation function v(w) of the time series w is defined as follows:

[0098]

[0099] Where v1(w) and v2(w) represent the anti-interference value and detection energy value respectively, the measurement factor ρ1<0.1, the energy factor ρ2>0, and sgn(·) represents the sign function; E s and Ed They represent the frequency band energy of the shielding sub-pulse and the detection sub-pulse respectively, and the expressions are as follows:

[0100]

[0101] in, represents the frequency domain variable, represents the real number domain, S(f) represents the echo s R The spectrum of (t), B s =(f1-Δf / 2,f1+Δf / 2),B d =(f2-Δf / 2,f2+Δf / 2).

[0102] Greedy search based timing design framework such as Figure 3 As shown, in this embodiment, the step S4 is specifically as follows:

[0103] S41, initializing radar survival window;

[0104] First, initialize the interaction cycle number l = 0, the value function V(w) = 0,

[0105] Then generate the time series w according to the ε-greedy strategy l , the expression is as follows:

[0106]

[0107] Among them, ε∈[0,1] is a constant, the random variable ξ obeys the [0,1] uniform distribution, and the probability distribution function P(k=i) of the random variable k is expressed as follows:

[0108]

[0109] S42, the radar transmits the combined shield and detection pulses according to the window, generates the echo signal and calculates the echo spectrum;

[0110] Radar based on w l Generate a transmit waveform and get the echo s R (t), calculate the echo spectrum S(f).

[0111] S43. Calculate the survival window value, i.e., the evaluation value v(wl), abbreviated as v l ;

[0112] S44, value function update;

[0113] Update the value function of the lth iteration, the expression is as follows:

[0114]

[0115] Among them, the discount factor 0<γ<1.

[0116] S45, greedy strategy selects a new window;

[0117] like Figure 3 As shown, let l = l + 1, if Convergence, output optimized timing Otherwise return to step S41.

[0118] In this embodiment, the sub-pulse width design process is as follows: Figure 4 As shown, for intermittent sampling interference, the timing to avoid the detection sub-pulse from being sampled can be successfully searched within a few transmit and receive cycles; in the subsequent stage, after the interference parameters change, the method of the present invention can also re-search the new timing and adapt to its changes in time.

[0119] In this embodiment, step S5 is specifically as follows:

[0120] The transmission timing optimized and designed in step S4 is used to generate a frequency domain orthogonal linear frequency modulation waveform for shielding and detection to perform anti-interference detection.

[0121] The document "S.Du, Z.Liu, Y.Wu, M.Sha, M.Xing, Y.Quan.'Frequency agilitywaveformcombined with time-frequency filter to suppress interrupted samplingrepeater jamming'Systems Engineering and Electronics, Jun.2022" proposes an existing linear frequency modulation method and a time-frequency filtering method. Figure 5 It is a schematic diagram of the anti-interference performance analysis of the method of the present invention and the existing linear frequency modulation method and time-frequency filtering method.

[0122] in, Figure 5 (a), (d), and (g) are the moving target detection (MTD) results of the linear frequency modulation signal, the time-frequency filtering method, and the method of the present invention under the condition of a single target and a single interference scenario and a signal-to-interference ratio of 10dB. Figure 5 (b), (e), and (h) are the MTD results of the three methods under three interference scenarios of a single target and an interference-to-signal ratio of 30 dB. Figure 5(c), (f), and (i) are the MTD results of the three methods under three interference scenarios with three targets and a signal-to-interference ratio of 30 dB. It can be seen that compared with the existing linear frequency modulation method and time-frequency filtering method, the method of the present invention has a lower false alarm probability and a higher detection probability, and can resist the interference scenario where multiple strong energy interferences with different parameters are superimposed.

[0123] In summary, the method of the present invention splices the orthogonal cover waveform and detection waveform into one pulse, designs a special value evaluation function, and dynamically designs the transmission waveform timing pulse by pulse according to the greedy search algorithm, so that the detection signal is prevented from being intercepted by the jammer, and the orthogonality between the cover waveform and the detection waveform is used to resist intermittent sampling interference. The method of the present invention has fast online dynamic learning characteristics, does not require accurate interference parameter estimation, and is still effective in the case of multiple interferences and high interference energy, and performs well in adapting to interference situations under a variety of different parameter scenarios, and can adapt to the scene where multiple different parameter intermittent sampling interferences are superimposed and have high interference energy, and has adaptability to scene changes, and has significant feasibility and practicality in engineering implementation, and has high engineering application value.

[0124] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A method for resisting multi-mainlobe intermittent sampling interference based on greedy search timing design, the specific steps are as follows: S1. Construct a mathematical model of the orthogonal shielding sub-pulse and detection sub-pulse structure; S2. Based on step S1, a radar receiving waveform model in a multi-target multi-interference scenario is constructed; S3. Design radar waveform value evaluation function based on echo spectrum energy; S4, based on step S3, using a greedy search framework, searching for the radar survival window and optimizing the launch timing; S5. Based on the transmission timing optimized and designed in step S4, a linear frequency modulation waveform orthogonal in the frequency domain is generated for shielding and detection to perform anti-interference detection.

2. According to the method of claim 1, a timing design based on greedy search to resist multi-main lobe intermittent sampling interference, It is characterized in that The step S1 is specifically as follows: Radar transmit waveform T (t) is expressed as follows: Among them, t∈[0,∞) represents the time variable, s(t) represents the detection waveform, and Represents the protection waveform, and the expressions are as follows: Among them, rect(·) represents the rectangular window function, {B 1 ,f 1 } and {B 2 ,f 2 } represent the bandwidth and carrier frequency of the shielding sub-pulse and the detection sub-pulse respectively, T s1 ,T d and T s2 denote x(t), s(t) and Pulse width; The frequency difference Δf between the shielding sub-pulse and the detection sub-pulse satisfies the following relationship, which is expressed as follows: Δf=|f 1 -f 2 |≥(B 1 +B 2 ) / 2. Time series collection of radar waveforms The expression is as follows: Among them, T p Indicates the pulse width of the radar transmission waveform s(t), Td 1 and Td 2 Respectively represent the upper and lower limits of the detection pulse width; Cardinality The expression is as follows: in, f s represents the sampling rate, represents the rounding down operation; the w distribution is marked as w i , 3. According to the method of claim 1, a timing design based on greedy search to resist multi-main lobe intermittent sampling interference, It is characterized in that The step S2 is specifically as follows: Set existence N T targets and N J Interference source, nth T =1,2,…,N T The distance and speed of the target are and No.n J =1,2,…,N J The distance and speed of the interference source are and Radar receiving waveform R (t) is composed of target echo, interference and noise, and its expression is as follows: Among them, λ and c represent the wavelength of radar emission waveform and the propagation speed of electromagnetic wave respectively; Respectively represent the nth T The target echo and the nth J The complex amplitude of the interference waveform, represents the complex domain, Indicates the nth J The interference waveform after down-conversion, n(t) represents the Gaussian white noise signal; The interference in the radar receiving waveform includes three types of intermittent sampling interference: intermittent sampling direct forwarding J D (t), intermittent sampling and repeated forwarding J P (t) and intermittent sampling cyclic forwarding J C (t) interference, the expressions are as follows: J D (t)=g 1 (t-T L ), Among them, T L and T S Respectively represent the sampling duration and sampling interval, Indicates the number of forwarding times. Indicates the number of sampling times; T p Indicates the jammer intercepted waveform s I (t) pulse width; g 1 (t) and The expressions are as follows: Among them, s I (t) = s T (tT 0 ) represents the radar waveform intercepted by the jammer, T 0 Indicates the start sampling time of the jammer, which is the time when the radar waveform is intercepted.

4. According to the method of claim 1, a timing design based on greedy search to resist multi-main lobe intermittent sampling interference, It is characterized in that The step S3 is specifically as follows: The value evaluation function v(w) of the time series w is defined as follows: Among them, v 1 (w) and v 2 (w) represent the anti-interference value and detection energy value respectively, and the measurement factor ρ 1 <0.1, energy factor ρ 2 >0, sgn(·) represents the sign function; E s and E d They represent the frequency band energy of the shielding sub-pulse and the detection sub-pulse respectively, and the expressions are as follows: in, represents the frequency domain variable, represents the real number domain, S(f) represents the echo s R The spectrum of (t), B s =(f 1 -Δf / 2,f 1 +Δf / 2), B d =(f 2 -Δf / 2,f 2 +Δf / 2).

5. According to the method of claim 1, a timing design based on greedy search to resist multi-main lobe intermittent sampling interference, It is characterized in that The step S4 is specifically as follows: S41, initializing radar survival window; First, initialize the interaction cycle number l = 0, the value function V(w) = 0, Then generate the time series w according to the ε-greedy strategy l , the expression is as follows: Among them, ε∈[0,1] is a constant, the random variable ξ obeys the [0,1] uniform distribution, and the probability distribution function P(k=i) of the random variable k is expressed as follows: S42, the radar transmits the combined shield and detection pulses according to the window, generates the echo signal and calculates the echo spectrum; Radar according to w l Generate a transmit waveform and get the echo s R (t), calculate the echo spectrum S(f); S43. Calculate the survival window value, i.e., the evaluation value v(wl), abbreviated as v l ; S44, value function update; Update the value function of the lth iteration, the expression is as follows: Among them, the discount factor is 0<γ<1; S45, greedy strategy selects a new window; Let l = l + 1, if Convergence, output optimized timing Otherwise return to step S41.

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