An intermittent sampling composite interference method and system based on non-uniform frequency shift modulation

Abstract

The present invention discloses an intermittent sampling composite jamming method and system based on non-uniform frequency shift modulation, which relates to the technical field of radar electronic countermeasures. The method includes performing intermittent sampling on an enemy radar signal to obtain an intermittent sampling signal; setting a periodic non-uniform frequency shift amount function and constructing a frequency shift modulation function; using the frequency shift modulation function to perform multiple delay and forwarding operations on the intermittent sampling signal to obtain an intermittent sampling frequency shift jamming signal; performing matched filtering processing on all the intermittent sampling frequency shift jamming signals and then superimposing them to obtain a superimposed intermittent sampling frequency shift jamming signal; adjusting the frequency shift amount of the superimposed intermittent sampling frequency shift jamming signal to obtain an intermittent sampling composite jamming signal for jamming the enemy radar. By adjusting the frequency shift amount, the present invention controls the amplitude and position of false targets, forms a leading strong false target and a false target near the real target, destroys the time-frequency distribution of the intermittent sampling jamming, and is not easily recognized.

Description

Technical Field

[0001] The present invention relates to the technical field of radar electronic countermeasures, and more specifically, to an intermittent sampling composite jamming method and system based on non-uniform frequency shift modulation. Background Art

[0002] After the linear frequency modulation (LFM) signal is matched filtered, a high coherent processing gain can be obtained, and it can effectively counter interference signals that do not match the radar waveform. Therefore, the research on interference technologies for LFM pulse compression radars has received extensive attention. Currently, it mainly includes smart noise interference, frequency shift interference, dense false target interference, etc. Based on the digital radio frequency memory (DRFM) technology, as Figure 1 shown, the interrupted-sampling repeater jamming (ISRJ) is based on the "undersampling" technology to perform periodic cyclic slicing and forwarding on the radar signal. It has the advantages of fast response speed, high isolation degree, and easy engineering implementation, and has both deception and suppression interference effects. However, due to the influence of its own fixed forwarding pulse width and fixed intermittent sampling period, the current intermittent sampling interference still has the following problems: The distribution law of the false targets formed after the ISRJ is matched filtered is strong. The amplitude of the false target is proportional to the intermittent sampling pulse width and inversely proportional to the intermittent sampling period; The time interval between the peak amplitudes of the adjacent two-order false targets generated by each delay forwarding is inversely proportional to the intermittent sampling period; The strong false target generated by the ISRJ lags behind the real target, and the lag amount is at least one intermittent sampling pulse width. Under the limited power of the jammer, the leading false target may not be able to effectively interfere; To solve these problems, the research on the modulation method and forwarding strategy of the intermittent sampling interference is a hot topic among scholars. The frequency shift modulation for the LFM signal can control the distribution of the false targets and obtain leading false target interference. Based on the traditional intermittent sampling frequency shift interference, non-uniform repeated forwarding interferences such as stepped frequency shift modulation, random frequency shift modulation, sinusoidal weighted frequency modulation, SSC (spectrum spread and compression, SSC) blind frequency shift, and stepped frequency shift modulation segmented by the intermittent sampling period have been proposed successively. However, the currently proposed improved algorithms for the ISRJ frequency shift modulation generally perform segmented modulation with the intermittent sampling period, as Figure 2 shown; The lagging strong false target can be shifted forward by frequency shift. Although the problems of strong false target distribution law and lagging strong false target can be solved, in the case of limited interference power, a stronger leading false target still cannot be formed, and thus an effective interference cannot be formed. Therefore, the research on the frequency shift modulation of the ISRJ urgently needs to solve how to set the frequency shift amount so that the generated false targets accumulate at the same position and time, generating a stronger leading false target.

[0003] The prior art discloses a non-uniform intermittent sampling random forwarding interference method for space-time adaptive processing, including: performing non-uniform intermittent sampling on the enemy radar signal st(t) to obtain a non-uniform intermittent sampling forwarding interference signal js(t); performing delay superposition on the non-uniform intermittent sampling forwarding interference signal js(t) to obtain a non-uniform intermittent sampling random forwarding interference signal jsc(t); and the jammer transmitting the non-uniform intermittent sampling random forwarding interference signal jsc(t) to interfere with the radar equipped with space-time adaptive processing. This application uses the methods of non-uniform intermittent sampling and indefinite repeated forwarding, which solves the problem of strong regularity of interference distribution to a certain extent, but there are still defects that the strong false targets generated lag behind the real target with a large lag amount, and the leading false targets cannot play an effective interference role. Summary of the Invention

[0004] To overcome the defects of the above prior art that under the limited power of the jammer, the amplitude of the false target is low and the distribution is regular, the present invention provides an intermittent sampling composite interference method and system based on non-uniform frequency shift modulation. Without the loss of mismatch in matched filtering, by adjusting the frequency shift amount, the amplitude and position of the false target are controlled to form leading strong false targets and false targets near the real target, which destroys the time-frequency distribution of the intermittent sampling interference and is not easily recognized.

[0005] To solve the above technical problems, the technical solution of the present invention is as follows:

[0006] The present invention provides an intermittent sampling composite interference method based on non-uniform frequency shift modulation, including:

[0007] S1: Performing intermittent sampling on the enemy radar signal to obtain an intermittent sampling signal;

[0008] S2: Setting a periodic non-uniform frequency shift amount function and constructing a frequency shift modulation function according to the periodic non-uniform frequency shift amount function;

[0009] S3: Using the frequency shift modulation function to perform multiple delay forwarding on the intermittent sampling signal to obtain an intermittent sampling frequency shift interference signal;

[0010] S4: Performing matched filtering processing on all intermittent sampling frequency shift interference signals to obtain a filtered intermittent sampling frequency shift interference signal;

[0011] S5: Superposing all filtered intermittent sampling frequency shift interference signals to obtain a superposed intermittent sampling frequency shift interference signal;

[0012] S6: Adjusting the frequency shift amount of the superposed intermittent sampling frequency shift interference signal to obtain an intermittent sampling composite interference signal;

[0013] S7: Using the intermittent sampling composite interference signal to interfere with the enemy radar.

[0014] Preferably, in the step S1, the specific method for obtaining the intermittent sampling signal is as follows:

[0015] S1.1: Intercept the enemy radar signal and analyze the parameters of the enemy radar signal;

[0016] S1.2: Construct an intermittent sampling and forwarding pulse according to the parameters of the enemy radar signal;

[0017] S1.3: Construct an intermittent sampling signal according to the enemy radar signal and the intermittent sampling and forwarding pulse.

[0018] Preferably, the specific method for constructing the intermittent sampling and forwarding pulse according to the parameters of the enemy radar signal is as follows:

[0019] The intercepted enemy radar signal is denoted as x(t), and the parameters include the bandwidth B, the pulse width T p , the frequency modulation slope k f and the jam-to-signal ratio JSR; set the intermittent sampling period of the intermittent sampling and forwarding pulse to T s , the number of intermittent sampling periods to N J , the intermittent sampling pulse width to τ, and T s ≥2τ, and the duty cycle is tao = τ / T s ; the intermittent sampling and forwarding pulse is:

[0020]

[0021] where p(t) represents the intermittent sampling and forwarding pulse at time t, rect(·) represents a rectangular pulse, δ(·) represents an impulse function, and * represents convolution calculation; N represents the repetition period label and is an integer.

[0022] Preferably, the specific method for constructing the intermittent sampling signal according to the enemy radar signal and the intermittent sampling and forwarding pulse is as follows:

[0023] Multiply the enemy radar signal by the intermittent sampling and forwarding pulse to obtain the intermittent sampling signal:

[0024] s J (t) = (t)·(t)

[0025] where s J (t) represents the intermittent sampling signal at time t.

[0026] Preferably, the specific method for the step S2 is as follows:

[0027] Set a periodic non-uniform frequency shift function:

[0028]

[0029] where f m(t) represents the periodic non-uniform frequency shift amount function during the m-th delayed forwarding, λ m represents the frequency shift width during the m-th delayed forwarding, f m,i represents the frequency shift amount in the i-th intermittent sampling period during the m-th delayed forwarding;

[0030] Construct a frequency shift modulation function according to the periodic non-uniform frequency shift amount function:

[0031]

[0032] In the formula, ξ m (t) represents the frequency shift modulation function during the m-th delayed forwarding.

[0033] Preferably, the specific method of step S3 is:

[0034] Use the frequency shift modulation function to perform delayed forwarding on the intermittent sampling signal, and set the maximum number of times of delayed forwarding of intermittent sampling to be Then the intermittent sampling interference signal is:

[0035] s JS,m (t) = J (t)· m (t) = (t)·(t)· m (t)

[0036] In the formula, s JS, (t) represents the intermittent sampling interference signal during the m-th delayed forwarding.

[0037] Preferably, the specific method of step S4 is:

[0038] Record the intermittent sampling signal forwarded for the m-th time as s J,m (t), and its spectrum is S J,m 9f), then the interference bandwidth of the i-th intermittent sampling period of the intermittent sampling signal forwarded for the m-th time is B m,i = (f3) i - (f1) i = k f τ, that is Among them, (f1) i , (f3) i respectively represent the lower sideband and upper sideband of the sub-pulse bandwidth in the i-th intermittent sampling period;

[0039] The intermittent sampling interference signal during the m-th delayed forwarding is s JS,m (t), and its spectrum is S JS,m (f), then the interference bandwidth B' of the i-th intermittent sampling period of the intermittent sampling interference signal during the m-th delayed forwarding m,i = (f2) i - (f1) i= k f λ m , that is where (f2) i represents that the frequency shift width of the i-th intermittent sampling period is λ m of the upper sideband; then:

[0040]

[0041] When (f2) i + f m,i ≤ B / 2, there is no mismatching loss in the matched filtering; then the matched filtering output of the intermittent sampling frequency shift interference signal after filtering in the m-th delay-forwarding i-th intermittent sampling period is:

[0042]

[0043] Set the output peak value of the matched filter to A x , H(f) represents the spectrum of the matched filter, and f represents the frequency of the integral calculation. Then, the m-th delay-forwarding i-th intermittent sampling period frequency shift modulation f m,i generates a leading false target, and the interference peak value is:

[0044]

[0045] In the formula, is the interference peak value of the intermittent sampling frequency shift interference signal after filtering in the m-th delay-forwarding i-th intermittent sampling period;

[0046] Then, the intermittent sampling frequency shift interference signal after filtering is:

[0047]

[0048] In the formula, y JS,m (t) represents the intermittent sampling interference signal after filtering in the m-th delay-forwarding, and H(f) represents.

[0049] Preferably, the specific method of the step S5 is:

[0050] The delay time of the m-th forwarding is mτ. Stack M J filtered intermittent sampling frequency shift interference signals to obtain a stacked intermittent sampling frequency shift interference signal:

[0051]

[0052]

[0053] The peak position moment of the 0th-order false target formed by the m-th delay-forwarding frequency shift modulation is:

[0054]

[0055] where y JS (t) represents the superimposed intermittent sampling frequency-shifted interference signal at time t, and f s represents the frequency of the intermittent sampling and retransmission pulse, y fn, (t) represents the interference signal that is retransmitted with a delay of mτ and frequency-shifted for the m-th time and generates N J sub false targets with frequency shifts of f m,i respectively, and the weighting coefficient is t0 represents the initial time of the target position; n represents the order of the Sa(*) function.

[0056] Preferably, the specific method of step S6 is:

[0057] In the case of no mismatch loss in the matched filtering, set the frequency shifts of the first N J -1 and the Nth J intermittent sampling periods to form a leading strong false target and a false target near the real target;

[0058] The first N J -1 intermittent sampling periods generate a leading strong false target, and the frequency shift within each intermittent sampling period decreases with the number of retransmissions M J ,…,2,1 by k f τ, that is:

[0059]

[0060] where represents the frequency shift of the β-th intermittent sampling period for the M J -th delay retransmission, represents the frequency shift of the β-th intermittent sampling period for the M J -th delay retransmission; β = 1, 2, … N J -1, α < M J and is an integer;

[0061] The Nth J intermittent sampling period generates a false target near the real target, and the frequency shift is:

[0062]

[0063] where represents the frequency shift of the Nth J intermittent sampling period for the m-th delay retransmission;

[0064] The first N J- The peak of the leading strong false target interference formed by multiple delays and forwarding within one intermittent sampling period accumulates at , and the peak of the false target interference near the real target formed by multiple delays and forwarding within the N J th intermittent sampling period accumulates at t0, forming an intermittent sampling composite interference signal.

[0065] The present invention also provides an intermittent sampling composite interference system based on non-uniform frequency shift modulation, including:

[0066] An intermittent sampling module, configured to perform intermittent sampling on the enemy radar signal to obtain an intermittent sampling signal;

[0067] A frequency shift modulation function construction module, configured to set a periodic non-uniform frequency shift amount function and construct a frequency shift modulation function according to the periodic non-uniform frequency shift amount function;

[0068] A frequency shift modulation and forwarding module, which uses the frequency shift modulation function to perform multiple delays and forwarding on the intermittent sampling signal to obtain an intermittent sampling frequency shift interference signal;

[0069] A matched filtering module, configured to perform matched filtering processing on all intermittent sampling frequency shift interference signals to obtain a filtered intermittent sampling frequency shift interference signal;

[0070] A signal superposition module, configured to superpose all filtered intermittent sampling frequency shift interference signals to obtain a superposed intermittent sampling frequency shift interference signal;

[0071] A frequency shift amount adjustment module, configured to adjust the frequency shift amount of the superposed intermittent sampling frequency shift interference signal to obtain an intermittent sampling composite interference signal;

[0072] An interference transmitting module, which uses the intermittent sampling composite interference signal to interfere with the enemy radar.

[0073] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0074] This application first performs intermittent sampling on the enemy radar signal to obtain an intermittent sampling signal; constructs a frequency shift modulation function by setting a periodic non-uniform frequency shift amount function; then uses the frequency shift modulation function to perform multiple delays and forwarding on the intermittent sampling signal to obtain an intermittent sampling frequency shift interference signal; then performs matched filtering processing on all intermittent sampling frequency shift interference signals and superposes them to obtain a superposed intermittent sampling frequency shift interference signal; finally, adjusts the frequency shift amount of the superposed intermittent sampling frequency shift interference signal to obtain an intermittent sampling composite interference signal to interfere with the enemy radar. By adjusting the frequency shift amount, this application controls the amplitude and position of the false target, forms a leading strong false target and a false target near the real target, destroys the time-frequency distribution of the intermittent sampling interference, and is not easily recognized. Description of the Drawings

[0075] Figure 1 It is the schematic diagram of the intermittent sampling and forwarding interference described in the background technology.

[0076] Figure 2 It is the schematic diagram of the intermittent sampling, segmented frequency shift, and non-uniform forwarding interference described in the background technology.

[0077] Figure 3 It is the flowchart of the intermittent sampling composite interference method based on non-uniform frequency shift modulation described in Embodiment 1.

[0078] Figure 4 It is the schematic diagram of the intermittent sampling composite interference method based on non-uniform frequency shift modulation described in Embodiment 2.

[0079] Figure 5 It is the schematic diagram of the spectral correspondence between the matched filtering and the intermittent sampling interference signal of the m-th delayed forwarding described in Embodiment 2.

[0080] Figure 6 It is the time-frequency diagram of the interference signal generated by the intermittent sampling composite interference method based on non-uniform frequency shift modulation described in Embodiment 2.

[0081] Figure 7 It is the schematic diagram of the pulse compression result of the interference signal of the traditional intermittent sampling and repeated forwarding interference method described in Embodiment 2.

[0082] Figure 8 It is the schematic diagram of the pulse compression result of the interference signal of the traditional intermittent sampling and frequency shift non-uniform forwarding interference method described in Embodiment 2.

[0083] Figure 9 It is for the frequency shift amount f 1.i = 5MHZ, f 2.i = 7MHZ, f 3.i = 9MHZ, it is the schematic diagram of the pulse compression result of the interference signal of the method provided in this embodiment.

[0084] Figure 10 It is for the frequency shift amount f 1.i = 15.625MHZ, f 2.1 = 18.75MHZ, f 3.1 = 21.875MHZ, it is the schematic diagram of the pulse compression result of the interference signal of the method provided in this embodiment.

[0085] Figure 11 It is for the frequency shift amount f 1.1 = f 1.2 = f 1.3 = 15.625MHZ, f 2.1 = f 2.2 = f 2.3 = 18.75MHZ, f3.1 = f 3.2 = f 3.3 = 21.875 MHZ, f 1.4 = 3.125 MHZ, f 2.4 = 6.25 MHZ, f 3.4 = 9.375 MHZ, frequency shift pulse width λ1 = 2 us, λ2 = 2.5 us, λ3 = 1.5 us, schematic diagram of the pulse compression result of the interference signal of the method provided by this embodiment.

[0086] Figure 12 For the frequency shift amount f described in Embodiment 2 1.1 = f 1.2 = f 1.3 = 15.625 MHZ, f 2.1 = f 2.2 = f 2.3 = 18.75 MHZ, f 3.1 = f 3.2 = f 3.3 = 21.875 MHZ, f 1.4 = 3.125 MHZ, f 2.4 = 6.25 MHZ, f 3.4 = 9.375 MHZ, frequency shift pulse width λ1 = λ2 = λ3 = 2.5 us, schematic diagram of the pulse compression result of the interference signal of the method provided by this embodiment.

[0087] Figure 13 Schematic diagram of the structure of the intermittent sampling composite interference system based on non-uniform frequency shift modulation described in Embodiment 3. Detailed implementation mode

[0088] The attached drawings are only for illustrative purposes and should not be construed as a limitation of this patent;

[0089] For better illustration of this embodiment, some components in the attached drawings are omitted, enlarged or reduced, which do not represent the size of the actual product;

[0090] For those skilled in the art, it is understandable that some well-known structures and their descriptions in the attached drawings may be omitted.

[0091] The technical solution of the present invention will be further described below with reference to the attached drawings and embodiments.

[0092] Embodiment 1

[0093] This embodiment provides a method for intermittent sampling composite interference based on non-uniform frequency shift modulation, as Figure 3 shown, including:

[0094] S1: Intermittently sample the enemy radar signal to obtain an intermittent sampling signal;

[0095] S2: Set a periodic non-uniform frequency shift amount function, and construct a frequency shift modulation function according to the periodic non-uniform frequency shift amount function;

[0096] S3: Use the frequency shift modulation function to perform multiple delay and forwarding operations on the intermittent sampling signal to obtain an intermittent sampling frequency shift interference signal;

[0097] S4: Perform matched filtering processing on all intermittent sampling frequency shift interference signals to obtain a filtered intermittent sampling frequency shift interference signal;

[0098] S5: Superimpose all the filtered intermittent sampling frequency shift interference signals to obtain a superimposed intermittent sampling frequency shift interference signal;

[0099] S6: Adjust the frequency shift amount of the superimposed intermittent sampling frequency shift interference signal to obtain an intermittent sampling composite interference signal;

[0100] S7: Use the intermittent sampling composite interference signal to interfere with the enemy radar.

[0101] In the specific implementation process, in this embodiment, the enemy radar signal is first intermittently sampled to obtain an intermittent sampling signal; by setting a periodic non-uniform frequency shift amount function, a frequency shift modulation function is constructed; then, the frequency shift modulation function is used to perform multiple delay and forwarding operations on the intermittent sampling signal to obtain an intermittent sampling frequency shift interference signal; then, all the intermittent sampling frequency shift interference signals are subjected to matched filtering processing and then superimposed to obtain a superimposed intermittent sampling frequency shift interference signal; finally, the frequency shift amount of the superimposed intermittent sampling frequency shift interference signal is adjusted to obtain an intermittent sampling composite interference signal to interfere with the enemy radar. In this embodiment, by adjusting the frequency shift amount, the amplitude and position of the false target are controlled to form a leading strong false target and a false target near the real target, which destroys the time-frequency distribution of the intermittent sampling interference and is not easily recognized.

[0102] Embodiment 2

[0103] This embodiment provides an intermittent sampling composite interference method based on non-uniform frequency shift modulation, as Figure 4 shown, including:

[0104] S1: Intermittently sample the enemy radar signal to obtain an intermittent sampling signal; the specific method is:

[0105] S1.1: Intercept the enemy radar signal and analyze the parameters of the enemy radar signal;

[0106] S1.2: Construct an intermittent sampling forwarding pulse according to the parameters of the enemy radar signal;

[0107] The intercepted enemy radar signal is denoted as x(t), and the parameters include the bandwidth B, the pulse width T p , and the frequency modulation slope k fCompare with Ganxin and JSR; set the intermittent sampling period of the intermittent sampling and forwarding pulse as T s and the number of intermittent sampling periods as N J , the intermittent sampling pulse width is τ, and T s ≥2τ, and the duty cycle is tao = τ / T s ; the intermittent sampling and forwarding pulse is:

[0108]

[0109] In the formula, p(t) represents the intermittent sampling and forwarding pulse at time t, rect(·) represents the rectangular pulse, δ(·) represents the impulse function, and * represents the convolution calculation; N represents the repetition period label and is an integer.

[0110] S1.3: Construct the intermittent sampling signal according to the enemy radar signal and the intermittent sampling and forwarding pulse.

[0111] Multiply the enemy radar signal by the intermittent sampling and forwarding pulse to obtain the intermittent sampling signal:

[0112] s J (t) = (t)·(t)

[0113] In the formula, s J (t) represents the intermittent sampling signal at time t.

[0114] S2: Set the periodic non-uniform frequency shift amount function and construct the frequency shift modulation function according to the periodic non-uniform frequency shift amount function; the specific method is:

[0115] Periodic non-uniform frequency shift amount function:

[0116]

[0117] In the formula, f m (t) represents the periodic non-uniform frequency shift amount function at the mth delayed forwarding, λ m represents the frequency shift width at the mth delayed forwarding, f m,i represents the frequency shift amount of the ith intermittent sampling period in the mth delayed forwarding;

[0118] Frequency shift modulation function:

[0119]

[0120] In the formula, ξ m (t) represents the frequency shift modulation function at the mth delayed forwarding.

[0121] S3: Use the frequency shift modulation function to perform multiple delayed forwardings on the intermittent sampling signal to obtain the intermittent sampling frequency shift interference signal; the specific method is:

[0122] The intermittent sampling signal is delayed and forwarded using the frequency shift modulation function, and the maximum number of forwarding times for intermittent sampling is set to Then the intermittent sampling interference signal is:

[0123] s JS,m (t) = J (t)· m (t) = (t)·(t)· m (t)

[0124] In the formula, s JS, (t) represents the intermittent sampling interference signal of the m-th delay and forward.

[0125] S4: Perform matched filtering on all intermittent sampling frequency shift interference signals to obtain the filtered intermittent sampling frequency shift interference signals; the specific method is:

[0126] As Figure 5 shown, the intermittent sampling signal of the m-th forward is denoted as s J,m (t), and the spectrum is S J,m (f), then the interference bandwidth of the i-th intermittent sampling period of the intermittent sampling signal of the m-th forward is B m,i = (f3) i - (f1) i = f τ, that is, where, (f1) i , (f3) i respectively represent the lower sideband and upper sideband of the sub-pulse bandwidth of the i-th intermittent sampling period;

[0127] The intermittent sampling interference signal of the m-th delay and forward is s JS, (t), and the spectrum is S JS, (f), then the interference bandwidth B ′ m,i = (f2) i - (f1) i = f λ m , that is, B ′ m,1 = ′ m,2 = … = ′ m,NJ , where, (f2) i represents the upper sideband with the frequency shift width of λ m for the i-th intermittent sampling period; then:

[0128]

[0129] When (f1)i + m,i When it is less than or equal to B / 2, there is no mismatch loss in the matched filtering; then the matched filtering output of the interleaved sampling frequency shift interference signal after filtering in the m-th delayed forwarding and the i-th interleaved sampling period is:

[0130]

[0131] Set the output peak value of the matched filter as A x , H(f) represents the spectrum of the matched filter, f represents the frequency for integral calculation, then the m-th delayed forwarding and the i-th interleaved sampling period frequency shift modulation f m,i Generates a leading false target, and the interference peak value is:

[0132]

[0133] In the formula, is the interference peak value of the interleaved sampling frequency shift interference signal after filtering in the m-th delayed forwarding and the i-th interleaved sampling period; the interference peak value is proportional to the frequency shift width, and increasing the frequency shift width can enhance the interference power.

[0134] Then the interleaved sampling frequency shift interference signal after filtering is:

[0135]

[0136] In the formula, y JS, (t) represents the interleaved sampling interference signal after filtering in the m-th delayed forwarding, and H(f) represents.

[0137] S5: Superimpose all the interleaved sampling frequency shift interference signals after filtering to obtain the superimposed interleaved sampling frequency shift interference signal; the specific method is:

[0138] The delay time of the m-th forwarding is mτ, and M J interleaved sampling frequency shift interference signals after filtering are superimposed to obtain the superimposed interleaved sampling frequency shift interference signal:

[0139]

[0140] If the enemy radar signal is:

[0141]

[0142] Then the interference output after y fn, (t) passes through the matched filter is:

[0143]

[0144] The peak position moment of the 0th-order false target formed by the m-th delayed forwarding frequency shift modulation is:

[0145]

[0146] where y JS (t) represents the superposition intermittent sampling frequency shift interference signal at time t, and f s represents the frequency of the intermittent sampling and forwarding pulse, y fn, (t) represents the interference signal that is delayed by mτ and frequency-shifted for the m-th time and frequency-shifted, generating N J sub false targets with frequency shifts of f m,i respectively, and the weighting coefficient is t0 represents the initial time of the target position; n represents the order of the Sa(*) function.

[0147] The peak position time of the 0th-order false target is determined by the frequency shift f m,i , and when f m,i >0, the 0th-order false target moves forward; when f m,i <0, the 0th-order false target moves backward; and when f m,1 = m,2 =... f m,NJ at the same position time, they are accumulated to enhance the interference power;

[0148] S6: Adjust the frequency shift of the superposition intermittent sampling frequency shift interference signal to obtain an intermittent sampling composite interference signal; the specific method is:

[0149] As Figure 6 shown, in the case of no mismatch loss of the matched filter, set the frequency shifts of the first N J -1 and the Nth J intermittent sampling periods to form a leading strong false target and a false target near the real target;

[0150] The first N J -1 intermittent sampling periods generate a leading strong false target, and the frequency shift within each intermittent sampling period decreases with the number of forwarding times M J ,…,2,1 by k f τ, that is:

[0151]

[0152] where represents the frequency shift of the β-th intermittent sampling period for the M J -th delayed forwarding, represents the frequency shift of the β-th intermittent sampling period for the M J -th delayed forwarding; β = 1,2,…N J -1, α < M J and is an integer;

[0153] The Nth J intermittent sampling period generates false targets near the real target, and the frequency shift amount is:

[0154]

[0155] In the formula, represents the frequency shift amount of the mth delayed forwarding in the Nth J intermittent sampling period;

[0156] The interference peaks of the leading strong false targets formed by multiple delayed forwardings in the previous N J -1 intermittent sampling periods are accumulated at , and the interference peaks of the false targets near the real target formed by multiple delayed forwardings in the Nth J intermittent sampling period are accumulated at t0, forming an intermittent sampling composite interference signal.

[0157] S7: Use the intermittent sampling composite interference signal to interfere with the enemy radar.

[0158] In the specific implementation process, simulation experiments are used to prove the interference effect of the method provided in this embodiment; the simulation platform is the windows10 operating system, and MATLAB2017a software is used; the pulse width T p of the simulated enemy radar signal is 40 us, the bandwidth B = 50 MHz, the carrier frequency f0 = 3 GHz, and the jamming-to-signal ratio JSR = 20 dB; when there is no frequency shift modulation, the sampling frequency f s of the intermittent sampling and forwarding pulse is 200 MHz, the pulse repetition interval PRI = 200 us, the number N J of the intermittent sampling periods is 4, the intermittent sampling period T s = 10 us, the intermittent sampling pulse width τ = 2.5 us, the maximum number M J of intermittent sampling forwardings is 3, and the duty cycle tao = 0.25; the duty cycle of each segment of frequency shift modulation interference is changed by the frequency shift width λ m ; set a comparative simulation experiment:

[0159] (1) In the traditional intermittent sampling frequency shift non-uniform forwarding interference algorithm, the frequency shift pulse widths of the 3 times of delayed quasi-forwarding are λ1 = λ2 = λ3 = 2.5 us, and the frequency shift amounts are ξ1 = 5 MHZ, ξ2 = 7 MHZ, ξ3 = 9 MHZ, ξ4 = 15 MHZ, and the non-uniform forwarding pulse widths are 2 us, 2.5 us, and 2 us respectively;

[0160] (2) In the method provided in this embodiment, the frequency shift pulse widths of the 3 times of delayed quasi-forwarding are λ1 = 2 us, λ2 = 2.5 us, and λ3 = 1.5 us, and the frequency shift amounts are set in three cases: ① f 1.1 = f 1.2 = f1.3 = f 1.4 = 5 MHZ, f 2.1 = f 2.2 = f 2.3 = f 2.4 = 7 MHZ, f 3.1 = f 3.2 = f 3.3 = f 3.4 = 9 MHZ; ② f 1.1 = f 1.2 = f 1.3 = f 1.4 = 15.625 MHZ, f 2.1 = 18.75 MHZ, f 3.1 = 21.875 MHZ; ③ f 1.1 = f 1.2 = f 1.3 = 15.625 MHZ, f 1.4 = 3.125 MHZ; f 2.1 = f 2.2 = f 2.3 = 18.75 MHZ, f 2.4 = 6.25 MHZ; f 3.1 = f 3.2 = f 3.3 = 21.875 MHZ, f 3.4 = 9.375 MHZ.

[0161] (3) The method provided in this embodiment, the shift frequency pulse widths of the three-time delayed quasi-transmission are λ1 = λ2 = λ3 = 2.5 us, and the shift frequency amount is set to f 1.1 = f 1.2 = f 1.3 = 15.625 MHZ, f 1.4 = 3.125 MHZ; f 2.1 = f 2.2 = f 2.3 = 18.75 MHZ, f 2.4 = 6.25 MHZ; f 3.1 = f 3.2 = f 3.3 = 21.875 MHZ, f 3.4 = 9.375 MHZ.

[0162] As Figure 7 and Figure 8 shown, they are respectively the interference signal pulse compression result schematic diagrams of the traditional intermittent sampling repeated forwarding interference method and the intermittent sampling shift frequency non-uniform forwarding interference method; the intermittent sampling interference forms three false target strings after three-time forwarding, and the interference peak values of the false target strings are the same, which is 4 dB; from Figure 8It can be seen that by setting different forwarding pulse widths of 2 us, 2.5 us, and 2 us, due to the addition of the Doppler frequency, the true target is submerged in the false target group, achieving the effect of suppressing interference with multiple false targets. However, due to different frequency shift amounts for each forwarding, ξ1 = 5 MHz, ξ2 = 7 MHz, ξ3 = 9 MHz, ξ4 = 15 MHz, the amplitude of the leading false target drops sharply, with a maximum of only -1.3 dB. To effectively interfere with the real target, it is necessary to increase the transmitting power of the jammer.

[0163] As Figure 9 shown, it is a schematic diagram of the pulse compression result of the interference signal when the method provided in this embodiment is in case ①. It can be seen from the figure that not only can leading false targets be generated, but also the problem of the regular distribution of traditional intermittent sampling interference is destroyed. Since the same frequency shift amount is applied for each delayed forwarding, that is, f 1.1 = f 1.2 = f 1.3 = f 1.4 = 5 MHz, f 2.1 = f 2.2 = f 2.3 = f 2.4 = 7 MHz, f 3.1 = f 3.2 = f 3.3 = f 3.4 = 9 MHz; for each forwarding, the sub-pulses of multiple intermittent sampling periods are accumulated at the same position to obtain a maximum interference peak value of 4 dB. At the same time, because there is a situation where the frequency shift pulse width is less than the forwarding pulse width, that is, λ1 and λ3 are less than τ, the signal without the applied frequency shift amount does not move in position, resulting in a 3 dB drop in the interference peak value.

[0164] As Figure 10 shown, it is a schematic diagram of the pulse compression result of the interference signal when the method provided in this embodiment is in case ②. It can be seen from the figure that for the first forwarding, the same frequency shift amount is applied and the frequency modulation amount within the first intermittent sampling period changes arithmetically at an interval of k f τ = 3.125 MHz, that is, f 1.1 = f 1.2 = f 1.3 = f 1.4 = 15.625 MHz, f 2.1 = 18.75 MHz, f 3.1 = 21.875 MHz, resulting in the superposition of the 4 intermittent sampling periods of the first forwarding and all the sub-pulses of the first intermittent sampling period at the same position, obtaining a group of false targets with irregular distribution, and the interference peak value is 2.9 dB. By increasing the transmitting power of the jammer, the interference peak value can be increased, but the setting of this frequency shift modulation makes there be no false targets near the real target, making it easy for the enemy radar to detect the real target.

[0165] AsFigure 11 As shown, it is a schematic diagram of the interference signal pulse compression result when the method provided in this embodiment is in case ③; it can be seen from the figure that the frequency shift amount applied for each forwarding in the first 3 intermittent sampling periods changes in steps of 3.125 MHz, so that the frequency shift amount applied for each forwarding in the 4th intermittent period also changes in steps of 3.125 MHz, that is, f 1.1 = f 1.2 = f 1.3 = 15.625 MHZ; f 2.1 = f 2.2 = f 2.3 = 18.75 MHZ; f 3.1 = f 3.2 = f 3.3 = 21.875 MHZ; f 1.4 = 3.125 MHZ, f 2.4 = 6.25 MHZ, f 3.4 = 9.375 MHZ; since the pulse widths of the three frequency shifts are different, λ1 = 2 us, λ2 = 2.5 us, λ3 = 1.5 us, the interference peak of the leading strong false target formed is 5 dB, and the interference peak of the false target near the real target is 1 dB.

[0166] As Figure 12 shown, it is a schematic diagram of the interference signal pulse compression result when the method provided in this embodiment is in simulation experiment (3); it can be seen from the figure that the frequency shift amount applied for each forwarding in the first 3 intermittent sampling periods changes in steps of 3.125 MHz, so that the frequency shift amount applied for each forwarding in the 4th intermittent period also changes in steps of 3.125 MHz, that is, f 1.1 = f 1.2 = f 1.3 = 15.625 MHZ; f 2.1 = f 2.2 = f 2.3 = 18.75 MHZ; f 3.1 = f 3.2 = f 3.3 = 21.875 MHZ; f 1.4 = 3.125 MHZ, f 2.4 = 6.25 MHZ, f 3.4 = 9.375 MHZ; since the pulse widths of the three frequency shifts are the same, λ1 = λ2 = λ3 = 2.5 us, all the forwarded interference signals participate in the frequency shift modulation, and the leading strong false target formed has the maximum interference peak, up to 6 dB, and the interference peak of the false target near the real target is 1.6 dB.

[0167] Embodiment 3

[0168] This embodiment provides an intermittent sampling composite interference system based on non-uniform frequency shift modulation, as Figure 13As shown in the figure, it includes:

[0169] An intermittent sampling module, which is used to perform intermittent sampling on the enemy radar signal to obtain an intermittent sampling signal;

[0170] A frequency shift modulation function construction module, which is used to set a periodic non-uniform frequency shift amount function and construct a frequency shift modulation function according to the periodic non-uniform frequency shift amount function;

[0171] A frequency shift modulation and forwarding module, which uses the frequency shift modulation function to perform multiple delay forwarding on the intermittent sampling signal to obtain an intermittent sampling frequency shift interference signal;

[0172] A matched filtering module, which is used to perform matched filtering processing on all intermittent sampling frequency shift interference signals to obtain a filtered intermittent sampling frequency shift interference signal;

[0173] A signal superposition module, which is used to superpose all filtered intermittent sampling frequency shift interference signals to obtain a superposed intermittent sampling frequency shift interference signal;

[0174] A frequency shift amount adjustment module, which is used to adjust the frequency shift amount of the superposed intermittent sampling frequency shift interference signal to obtain an intermittent sampling composite interference signal;

[0175] An interference emission module, which uses the intermittent sampling composite interference signal to interfere with the enemy radar.

[0176] The same or similar reference numerals correspond to the same or similar components;

[0177] The terms describing the positional relationship in the drawings are only for illustrative purposes and should not be construed as a limitation of this patent;

[0178] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. An intermittent sampling composite interference method based on non-uniform frequency shift modulation, characterized in that Including: S1: Intermittently sample the enemy radar signal to obtain an intermittently sampled signal; S2: Set a periodic non-uniform frequency shift amount function and construct a frequency shift modulation function according to the periodic non-uniform frequency shift amount function; S3: Use the frequency shift modulation function to perform multiple delay-and-forward operations on the intermittently sampled signal to obtain an intermittently sampled frequency shift interference signal; S4: Perform matched filtering on all intermittently sampled frequency shift interference signals to obtain a filtered intermittently sampled frequency shift interference signal; S5: Superimpose all the filtered intermittently sampled frequency shift interference signals to obtain a superimposed intermittently sampled frequency shift interference signal; S6: Adjust the frequency shift amount of the superimposed intermittently sampled frequency shift interference signal to obtain an intermittently sampled composite interference signal; S7: Use the intermittently sampled composite interference signal to interfere with the enemy radar.

2. The intermittent sampling composite interference method based on non-uniform frequency shift modulation according to claim 1, wherein In the step S1, the specific method for obtaining the intermittently sampled signal is as follows: S1.1: Intercept the enemy radar signal and analyze the parameters of the enemy radar signal; S1.2: Construct an intermittently sampled and forwarded pulse according to the parameters of the enemy radar signal; S1.3: Construct an intermittently sampled signal according to the enemy radar signal and the intermittently sampled and forwarded pulse.

3. The intermittent sampling composite interference method based on non-uniform frequency shift modulation according to claim 2, wherein The specific method for constructing the intermittently sampled and forwarded pulse according to the parameters of the enemy radar signal is as follows: The intercepted enemy radar signal is denoted as x(t), and the parameters include the bandwidth B, the pulse width T p , the frequency modulation slope k f , and the jam-to-signal ratio JSR; the intermittent sampling period of the intermittent sampling and forwarding pulse is set as T s , the number of intermittent sampling periods is N J , the intermittent sampling pulse width is τ, and T s ≥2τ, and the duty cycle is tao = τ / T s ; the intermittent sampling and forwarding pulse is as follows: In the formula, p(t) represents the intermittently sampled and forwarded pulse at time t, rect(·) represents a rectangular pulse, δ(·) represents an impulse function, * represents convolution calculation; N represents the repetition period label and is an integer.

4. The intermittent sampling composite interference method based on non-uniform frequency shift modulation according to claim 3, characterized in that The specific method for constructing the intermittently sampled signal according to the enemy radar signal and the intermittently sampled and forwarded pulse is as follows: Multiply the enemy radar signal by the intermittently sampled and forwarded pulse to obtain an intermittently sampled signal: s J (t) = x(t) · p(t) where s J (t) represents the intermittent sampling signal at time t.

5. The intermittent sampling composite interference method based on non-uniform frequency shift modulation according to claim 4, characterized in that The specific method of the step S2 is Set a periodic non-uniform frequency shift amount function: where f m (t) represents the periodic non-uniform frequency shift function during the m-th delayed forwarding, λ m represents the frequency shift width of the m-th delayed forwarding, f m,i represents the frequency shift amount of the i-th intermittent sampling period during the m-th delayed forwarding; Construct a frequency shift modulation function according to the periodic non-uniform frequency shift amount function: where ξ m (t) represents the frequency shift modulation function at the m-th delayed forwarding.

6. The intermittent sampling composite interference method based on non-uniform frequency shift modulation according to claim 5, characterized in that, The specific method of the step S3 is as follows: The intermittent sampling signal is delayed and forwarded using the frequency shift modulation function, and the maximum number of forwarding times for intermittent sampling is set to Then the intermittent sampling interference signal is s JS,m (t) = s J (t)·ξ m (t) = x(t)·p(t)·ξ m (t) where s JS,m (t) represents the intermittent sampling interference signal of the m-th delayed forwarding.

7. The intermittent sampling composite interference method based on non-uniform frequency shift modulation according to claim 6, characterized in that The specific method of the step S4 is as follows: Denote the intermittent sampling signal of the m-th retransmission as s J,m (t), and its spectrum as S J,m (f). Then, the interference bandwidth of the i-th intermittent sampling period of the intermittent sampling signal of the m-th retransmission is B m,i =(f3) i -(f1) i =k f τ, that is where, (f1) i ,(f3) i represent the lower sideband and the upper sideband of the sub-pulse bandwidth of the i-th intermittent sampling period respectively; The intermittent sampling interference signal of the m-th delayed forwarding is s JS,m (t), and its spectrum is S Js,m (f). Then, the interference bandwidth B' of the i-th intermittent sampling period of the intermittent sampling interference signal of the m-th delayed forwarding m,i =(f2) i -(f1) i =k f λ m , that is where (f2) i represents the upper sideband with a frequency shift width of λ m in the i-th intermittent sampling period; then: When (f2) i +f m,i ≤ B / 2, there is no mismatched filtering loss; then the matched filtering output of the intermitted sampling frequency shift interference signal after filtering in the i-th intermitted sampling period of the m-th delay and forwarding is: Set the output peak of the matched filter to A x , where H(f) represents the spectrum of the matched filter and f represents the frequency of the integral calculation. Then, for the m-th delay and the i-th intermittent sampling period, the frequency shift modulation is f m,i Generate a leading false target, and the interference peak is: Where, (A JS,m ) i is the interference peak value of the intermittent sampling frequency shift interference signal filtered by the m-th delayed forwarding of the i-th intermittent sampling period; Then the filtered intermittently sampled frequency shift interference signal is: where y JS, (t) represents the filtered intermittent sampling interference signal after the m-th delayed forwarding.

8. The intermittent sampling composite interference method based on non-uniform frequency shift modulation according to claim 7, characterized in that, The specific method of the step S5 is as follows: The delay time of the m-th forwarding is mτ, and M J filtered intermittent sampling frequency shift interference signals are superimposed to obtain a superimposed intermittent sampling frequency shift interference signal: The peak position time of the 0th-order false target formed by the mth delay-and-forward frequency shift modulation is: where y JS (t) represents the superimposed intermittent sampling frequency shift interference signal at time t, f s represents the frequency of the intermittent sampling and forwarding pulse, y fn, (t) represents the interference signal that is delayed by mτ for the m-th time, frequency-shifted, and N J sub false targets with frequency shifts of f m,i respectively are generated, and the weighting coefficient is t0 represents the initial time of the target position; n represents the order of the Sa(*) function.

9. The intermittent sampling composite interference method based on non-uniform frequency shift modulation according to claim 8, wherein The specific method of the step S6 is as follows: In the case of no mismatching loss of matched filtering, set the frequency shift amounts of the first N J -1 and the N J intermittent sampling periods to form leading strong false targets and false targets near the real target; First N J - One leading strong false target is generated in each intermittent sampling period, and the frequency shift amount in each intermittent sampling period decreases with the number of forwarding times M J ,…, 2, 1 in k f τ decreases, that is: In the formula, represents the frequency shift amount of the M J -α times delayed forwarding in the β-th intermittent sampling period, represents the frequency shift amount of the M J -th delayed forwarding in the β-th intermittent sampling period; β = 1, 2, … N J -1, α < M J and is an integer; The Nth J false targets are generated near the real target during each intermittent sampling period, and the frequency shift amount is: wherein, represents the frequency shift amount of the m-th delayed forwarding in the N-th intermittent sampling period; J ​ First N J - The interference peak of the leading strong false target formed by multiple delayed transmissions in the previous N intermittent sampling periods accumulates at , and the interference peak of the false target near the real target formed by multiple delayed transmissions in the Nth J intermittent sampling period accumulates at t0, forming an intermittent sampling composite interference signal.

10. An intermittent sampling composite interference system based on non-uniform frequency shift modulation, characterized in that, Including: An intermittently sampling module, which is used to intermittently sample the enemy radar signal to obtain an intermittently sampled signal; A frequency shift modulation function construction module, which is used to set a periodic non-uniform frequency shift amount function and construct a frequency shift modulation function according to the periodic non-uniform frequency shift amount function; A frequency shift modulation and forwarding module, which uses the frequency shift modulation function to perform multiple delay-and-forward operations on the intermittently sampled signal to obtain an intermittently sampled frequency shift interference signal; A matched filtering module, which is used to perform matched filtering on all intermittently sampled frequency shift interference signals to obtain a filtered intermittently sampled frequency shift interference signal; A signal superposition module, which is used to superimpose all the filtered intermittently sampled frequency shift interference signals to obtain a superimposed intermittently sampled frequency shift interference signal; A frequency shift amount adjustment module, which is used to adjust the frequency shift amount of the superimposed intermittently sampled frequency shift interference signal to obtain an intermittently sampled composite interference signal; An interference transmitting module, which uses the intermittently sampled composite interference signal to interfere with the enemy radar.

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