An intermittent sampling interference method and system based on pseudo-random sequence frequency shift modulation

Abstract

The present invention discloses an intermittent sampling interference method and system based on pseudo-random sequence frequency shift modulation, which relates to the technical field of radar electronic countermeasures, including intermittent sampling of enemy radar signals to obtain intermittent sampling signals; setting a pseudo-random sequence and a frequency shift amount, constructing a frequency shift amount function and a frequency shift modulation function; using the frequency shift modulation function to modulate and forward the intermittent sampling signal to obtain a frequency shift modulation interference signal; then performing matched filtering processing, parsing the filtered interference signal to obtain an optimal frequency shift amount matrix; substituting the optimal frequency shift amount matrix into the filtered interference signal to obtain an optimal interference signal, and implementing interference on the enemy radar. The present invention causes false targets to randomly superimpose around the real target, forming strong false targets with random distributions of leading, nearby, and lagging; not only adjusting the amplitude and position distribution of the strong false targets, but also destroying the time-frequency distribution and spatial distribution characteristics of the intermittent sampling interference, having both suppression and deception interference effects.

Description

Technical Field

[0001] The present invention relates to the technical field of radar electronic countermeasures, and more particularly to an intermittent sampling interference method and system based on pseudo-random sequence frequency shift modulation. Background Art

[0002] In the increasingly complex electronic battlefield, anti-interference and jamming technology has become a research hotspot in the field of electronic countermeasures. With the rapid development and widespread application of radio frequency memory (DRFM), direct digital synthesizer (DDS) high-speed digital circuits and signal processing technology, it has become an important means to counter coherent radar. Figure 1 As shown in the figure, the interrupted-sampling repeater jamming (ISRJ) proposed based on DRFM technology first samples a small segment of the signal and stores it in DRFM, then amplifies and forwards it, then receives and samples it, and then forwards it again, repeating the cycle. ISRJ solves the problem of antenna isolation, has a fast response speed, is easy to implement in engineering, and has both deception and suppression jamming effects. However, due to the limitations of its inherent structural characteristics, ISRJ has the following problems: (1) Timing discontinuity and strong regularity in time-frequency distribution. ISRJ implements periodic cyclic slice forwarding, resulting in multiple identical slices being forwarded continuously in each intermittent sampling period. The time-frequency distribution is clear at a glance and is very easy to identify; (2) The false targets formed by ISRJ after matched filtering have strong spatial distribution regularity. The false target amplitude is proportional to the intermittent sampling pulse width and inversely proportional to the intermittent sampling period; the time interval between the peak amplitudes of two adjacent false targets generated by each delayed forwarding is inversely proportional to the intermittent sampling period; (3) The strong false target generated by ISRJ lags behind the real target, and the lag is at least one intermittent sampling pulse width. Under limited jammer power, the leading false target may not be able to effectively interfere.

[0003] In order to solve the above-mentioned problems of ISRJ and improve its interference effect, many researchers have started from two aspects: the modulation method and forwarding strategy of ISRJ. In order to solve the problems of time-frequency distribution and spatial distribution regularity, phase modulation, convolution modulation, multi-waveform modulation and other methods are often used to generate dense noise and dense false targets to cover the real target, effectively protecting the real target. Generally, the amplitude of the false target is increased and the number of false targets is increased by controlling the modulation parameters. The disadvantages are that it is impossible to form a strong false target ahead of the guide, the interference power is reduced, and the amount of calculation is large; in order to solve the problem that the strong false target lags behind the real target, due to the strong coupling of the frequency and distance of the linear frequency modulation signal, the frequency shift modulation of the LFM signal is used to control the position distribution characteristics of the false target to obtain a strong false target ahead of the guide. For intermittent sampling interference frequency shift modulation, improved algorithms such as step wave frequency shift, random frequency shift, sinusoidal weighted frequency shift, SSC (spectrum spread and compression, SSC) blind frequency shift, segmented random frequency shift and non-uniform forwarding joint modulation have been proposed successively. However, the improved algorithms currently proposed generally perform segmented frequency shift modulation based on intermittent sampling periods, such as Figure 2 As shown in the figure, by shifting the lagging strong false target forward through frequency shift modulation, although it can solve the problem of strong false target distribution regularity and strong false target lag, it is still ineffective for the situation where the strong false target ahead of the leader is ineffective under limited interference power, and it still cannot form a stronger false target ahead of the leader to form effective interference. Moreover, because the frequency shift modulation segment width is the same, its time-frequency distribution often has a strong regularity. Therefore, the research on frequency shift modulation of ISRJ urgently needs to solve two problems: (1) How to set the frequency shift amount so that the false targets generated are accumulated at the same position and time to produce a stronger false target ahead of the leader; (2) How to set the frequency shift modulation width to greatly destroy the time-frequency distribution characteristics of the intermittent sampling interference signal.

[0004] The prior art discloses a method for non-uniform intermittent sampling random forwarding interference with space-time adaptive processing, comprising: performing non-uniform intermittent sampling on an enemy radar signal st(t) to obtain a non-uniform intermittent sampling forwarding interference signal js(t); delaying and superimposing the non-uniform intermittent sampling forwarding interference signal js(t) to obtain a non-uniform intermittent sampling random forwarding interference signal jsc(t); and transmitting the non-uniform intermittent sampling random forwarding interference signal jsc(t) from a jammer to interfere with a radar equipped with space-time adaptive processing. This application employs non-uniform intermittent sampling and variable repeated forwarding, which to some extent solves the problem of strong regularity in interference distribution. However, there is still a drawback in that the generated strong false targets lag behind the real targets by a large amount, making it impossible for the leading false targets to effectively interfere. Summary of the Invention

[0005] In order to overcome the defects of the above-mentioned prior art in that strong false targets are generated that lag behind real targets, interfere with the time-frequency distribution law, and the spatial characteristic distribution law of false targets, the present invention provides an intermittent sampling interference method and system based on pseudo-random sequence frequency shift modulation, which applies a random pseudo-random sequence and frequency shift amount to the enemy radar signal, so that false targets are randomly superimposed around the target, forming strong false targets with random distribution in front, near, and behind; not only the amplitude and position distribution of the strong false targets are adjusted, but also the time-frequency distribution and spatial distribution characteristics of the intermittent sampling interference are destroyed, thereby having both suppression and deception interference effects.

[0006] In order to solve the above technical problems, the technical solutions of the present invention are as follows:

[0007] The present invention provides an intermittent sampling interference method based on pseudo-random sequence frequency shift modulation, comprising:

[0008] S1: intermittently sample the enemy radar signal to obtain an intermittent sampling signal;

[0009] S2: Set the pseudo-random sequence and frequency shift amount, construct a frequency shift amount function, and construct a frequency shift modulation function based on the frequency shift amount function;

[0010] S3: Use the frequency shift modulation function to modulate and forward the intermittent sampling signal to obtain a frequency shift modulation interference signal;

[0011] S4: performing matched filtering on the frequency shift modulated interference signal to obtain a filtered interference signal;

[0012] S5: Analyze the filtered interference signal to obtain the optimal frequency shift matrix;

[0013] S6: Substitute the optimal frequency shift matrix into the filtered interference signal to obtain the optimal interference signal; use the optimal interference signal to interfere with the enemy radar.

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

[0015] S1.1: Intercept enemy radar signals and analyze their parameters;

[0016] S1.2: Construct intermittent sampling forwarding pulses based on the parameters of the enemy radar signal;

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

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

[0019] The intercepted enemy radar signal is recorded as x(t), and its parameters include signal bandwidth B, pulse width T p, FM slope k f and signal-to-noise ratio JSR; based on the pulse width T of the enemy radar signal p , set the intermittent sampling period of the intermittent sampling forwarding pulse to T s , the number of intermittent sampling periods is The intermittent sampling pulse width is τ, and T s ≥2τ; intermittent sampling forwarding pulse is:

[0020]

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

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

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

[0024] s J (t) = x(t)·p(t)

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

[0026] Preferably, the specific method of step S2 is:

[0027] [(i-1)T s ,iT s ] is recorded as the i-th intermittent sampling period, and the pseudo-random sequence c is set i,k and frequency shift ξ i,k , the width of the pseudo-random sequence is T c , where c i,k represents the kth pseudo-random sequence value in the i-th intermittent sampling period, ξ i,k It represents the frequency shift amount controlled by the kth pseudo-random sequence width in the i-th intermittent sampling period, The pseudo-random sequence values ​​from 0 to n-1 in the i-th intermittent sampling period are denoted as c i,0 to c i,n-1 , the corresponding frequency shift amount from 0 to n-1 in the i-th intermittent sampling period is recorded as ξ i,0 To i,n-1 , construct the frequency shift function:

[0028]

[0029] Where f(t) represents the frequency shift function at time t;

[0030] Construct the frequency shift modulation function based on the frequency shift amount function:

[0031] u(t)= j2π·f(t)·

[0032] Where u(t) represents the frequency shift modulation function at time t.

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

[0034] Use the frequency shift modulation function to modulate and forward the intermittent sampling signal, and set the maximum forwarding times of intermittent sampling to Where tao represents the duty cycle, tao = τ / Y s ; The delay time of the mth forwarding is mτ, then the frequency shift modulation interference signal is:

[0035]

[0036] Where s JC (t) represents the frequency shift modulation interference signal at time t.

[0037] Preferably, in step S4, the filtered interference signal is specifically:

[0038]

[0039] Where y JC (t) represents the filtered interference signal at time t, f s Indicates the frequency of intermittent sampling forwarding pulses, n represents the order of the Sa(*) function, which is an integer.

[0040] Preferably, in step S5, the specific method for analyzing the filtered interference signal is:

[0041] Let y m (t)=h(t)*(t-mτ), the interference signal y after filtering JC (t) is divided into two parts; the first part is the interference signal after the 0-order false target is filtered, which is used to generate the 0-order false target, specifically:

[0042]

[0043] Where, represents the interference signal after filtering of the 0th order false target at time t;

[0044] The second part is the interference signal after filtering of the secondary false target group, which is used to generate the secondary false target group. Specifically:

[0045]

[0046] Where, shows the interference signal after filtering of the secondary false target group at time t;

[0047] The amplitude of the 0th order false target is determined by the intermittent sampling pulse width τ and the intermittent sampling period T s and frequency shift modulation function e j2π·f(t)·t It is jointly determined by the intermittent sampling pulse width and inversely proportional to the intermittent sampling period; the secondary false target group is composed of and frequency shift modulation function e j2π·f(t)·t Modulation generation;

[0048] Set the interference bandwidth of the intermittent sampling signal in each intermittent sampling period to B0 = k f τ, the interference bandwidth of the precise interference signal modulated by pseudo-random sequence frequency shift is B′0=k f T c ; A spectrum with bandwidth B′0 passes through ξ i,k Modulation produces a false target, and the interference peak of the interference signal after filtering is:

[0049]

[0050] The position of the interference peak of the interference signal after filtering is:

[0051]

[0052] Where, (A JC ) i,k A represents the interference peak value of the filtered interference signal modulated by the kth frequency shift amount in the i-th intermittent sampling period, x represents the amplitude of the real target, JSR represents the interference-to-signal ratio of the enemy radar signal; t i,k k represents the position time of the interference peak of the filtered interference signal modulated by the kth frequency shift amount in the i-th intermittent sampling period, f Represents the frequency modulation slope of the enemy radar signal; when ξ i,k >0, the false target moves forward; when ξ i,k When <0, the false target generated moves backward;

[0053] The position times of the interference peaks of any two filtered interference signals are:

[0054]

[0055] To achieve interference superposition, the two frequency shift amounts must satisfy:

[0056] when When , the two frequency shift amounts must satisfy:

[0057]

[0058] when When α and β are both integers, and 0≤α<β≤M J , then the two frequency shift amounts must satisfy:

[0059]

[0060] Set Nth J The last frequency shift amount in an intermittent sampling period is the maximum frequency shift amount, so the maximum frequency shift amount is:

[0061]

[0062] Where, Indicates the maximum frequency shift amount.

[0063] Preferably, the optimal frequency shift matrix is:

[0064] ξ opt =k f τ,2k f τ,…,M J · f τ]

[0065] Where, ξ opt Represents the optimal frequency shift matrix.

[0066] The present invention also provides an intermittent sampling interference system based on pseudo-random sequence frequency shift modulation, comprising:

[0067] An intermittent sampling module is used to intermittently sample enemy radar signals to obtain intermittent sampling signals;

[0068] A frequency shift modulation function construction module is used to set a pseudo-random sequence and a frequency shift amount, construct a frequency shift amount function, and construct a frequency shift modulation function based on the frequency shift amount function;

[0069] The frequency shift modulation forwarding module uses the frequency shift modulation function to modulate and forward the intermittent sampling signal to obtain the frequency shift modulation interference signal;

[0070] A matched filtering module is used to perform matched filtering on the frequency shift modulation interference signal to obtain a filtered interference signal;

[0071] The signal analysis module is used to analyze the interference signal after filtering to obtain the optimal frequency shift matrix;

[0072] The jamming signal construction transmitting module is used to substitute the optimal frequency shift matrix into the filtered jamming signal to obtain the optimal jamming signal; and use the optimal jamming signal to jam the enemy radar.

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

[0074] The present application first performs intermittent sampling on the enemy radar signal to obtain an intermittent sampling signal; by setting a pseudo-random sequence and a frequency shift amount, a frequency shift amount function and a frequency shift modulation function are constructed; then the intermittent sampling signal is modulated and forwarded using the frequency shift modulation function to obtain a frequency shift modulation interference signal; the frequency shift modulation interference signal is then subjected to matched filtering, and the obtained filtered interference signal is analyzed to obtain an optimal frequency shift amount matrix; finally, the optimal frequency shift amount matrix is ​​substituted into the filtered interference signal to obtain an optimal interference signal, and the optimal interference signal is used to interfere with the enemy radar. The present application causes false targets to be randomly superimposed around the target, forming strong false targets that are randomly distributed in front, near, and behind; not only the amplitude and position distribution of the strong false targets are adjusted, but also the time-frequency distribution and spatial distribution characteristics of the intermittent sampling interference are destroyed, with both suppression and deception interference effects. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0076] Figure 2 This is a schematic diagram of the principle of intermittent sampling segmented frequency shifting non-uniform forwarding interference described in the background technology.

[0077] Figure 3 This is a flow chart of the intermittent sampling interference method based on pseudo-random sequence frequency shift modulation described in Example 1.

[0078] Figure 4 This is a schematic diagram of the intermittent sampling interference method based on pseudo-random sequence frequency shift modulation described in Example 2.

[0079] Figure 5 This is a timing diagram of the interference signal generated by the intermittent sampling interference method based on pseudo-random sequence frequency shift modulation described in Example 2.

[0080] Figure 6 Schematic diagram of the intermittent sampling period of the pseudo-random sequence described in Example 2.

[0081] Figure 7 This is a time-frequency distribution diagram of the traditional intermittent sampling and forwarding interference described in Example 2.

[0082] Figure 8 This is a schematic diagram of the interference output after interference matching filtering processing by the traditional intermittent sampling forwarding method described in Example 2.

[0083] Figure 9This is a time-frequency distribution diagram of the traditional intermittent sampling segmented frequency shift non-uniform forwarding interference when the frequency shift amounts ξ1=10MHZ, ξ2=12MHZ, ξ3=15MHZ, and ξ4=10MHZ as described in Example 2.

[0084] Figure 10 This is a schematic diagram of interference output after interference matching filtering processing using conventional intermittent sampling segmented frequency shifting and non-uniform forwarding when the frequency shift amounts ξ1 = 10 MHZ, ξ2 = 12 MHZ, ξ3 = 15 MHZ, and ξ4 = 10 MHZ as described in Example 2.

[0085] Figure 11 For the frequency shift amount ξ1=8MHZ,ξ2=12MHZ,ξ3=15MHZ,ξ4=

[0086] 18MHZ, pseudo-random sequence width T c =2, the time-frequency distribution diagram of the method proposed in this embodiment.

[0087] Figure 12 For the frequency shift amount ξ1=8MHZ,ξ2=12MHZ,ξ3=15MHZ,ξ4=

[0088] 18MHZ, pseudo-random sequence width T c =2, a schematic diagram of the interference output after matched filtering processing by the method proposed in this embodiment.

[0089] Figure 13 The pseudo-random sequence width T described in Example 2 c =2, the frequency shift amount satisfies the optimal frequency shift amount matrix ξ opt =[5MHZ, 10MHZ, 15MHZ, 20MHZ], time-frequency distribution diagram of the method proposed in this embodiment. Figure 14 The pseudo-random sequence width T described in Example 2 c =2, the frequency shift amount satisfies the optimal frequency shift amount matrix ξ opt =[5MHZ, 10MHZ, 15MHZ, 20MHZ], a schematic diagram of the interference output after matched filtering processing by the method proposed in this embodiment.

[0090] Figure 15 The pseudo-random sequence width T described in Example 2 c =1, the frequency shift amount satisfies the optimal frequency shift amount matrix ξ opt =[5MHZ, 10MHZ, 15MHZ, 20MHZ], time-frequency distribution diagram of the method proposed in this embodiment. Figure 16 The pseudo-random sequence width T described in Example 2 c =1, the frequency shift amount satisfies the optimal frequency shift amount matrix ξ opt=[5MHZ, 10MHZ, 15MHZ, 20MHZ], a schematic diagram of the interference output after matched filtering processing by the method proposed in this embodiment.

[0091] Figure 17 This is a structural diagram of the intermittent sampling interference system based on pseudo-random sequence frequency shift modulation described in Example 3. DETAILED DESCRIPTION

[0092] The accompanying drawings are for illustrative purposes only and are not to be construed as limiting this patent;

[0093] In order to better illustrate this embodiment, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product size;

[0094] It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0095] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0096] Example 1

[0097] This embodiment provides an intermittent sampling interference method based on pseudo-random sequence frequency shift modulation, such as Figure 3 Shown, including:

[0098] S1: intermittently sample the enemy radar signal to obtain an intermittent sampling signal;

[0099] S2: Set the pseudo-random sequence and frequency shift amount, construct a frequency shift amount function, and construct a frequency shift modulation function based on the frequency shift amount function;

[0100] S3: Use the frequency shift modulation function to modulate and forward the intermittent sampling signal to obtain a frequency shift modulation interference signal;

[0101] S4: performing matched filtering on the frequency shift modulated interference signal to obtain a filtered interference signal;

[0102] S5: Analyze the filtered interference signal to obtain the optimal frequency shift matrix;

[0103] S6: Substitute the optimal frequency shift matrix into the filtered interference signal to obtain the optimal interference signal; use the optimal interference signal to interfere with the enemy radar.

[0104] In the specific implementation process, this embodiment first performs intermittent sampling on the enemy radar signal to obtain an intermittent sampling signal; by setting a pseudo-random sequence and a frequency shift amount, a frequency shift amount function and a frequency shift modulation function are constructed; then the intermittent sampling signal is modulated and forwarded using the frequency shift modulation function to obtain a frequency shift modulation interference signal; then the frequency shift modulation interference signal is subjected to matched filtering, and the obtained filtered interference signal is analyzed to obtain an optimal frequency shift amount matrix; finally, the optimal frequency shift amount matrix is ​​substituted into the filtered interference signal to obtain an optimal interference signal, and the optimal interference signal is used to interfere with the enemy radar. This application causes false targets to be randomly superimposed around the target, forming strong false targets that are randomly distributed in front, near, and behind; not only the amplitude and position distribution of the strong false targets are adjusted, but also the time-frequency distribution and spatial distribution characteristics of the intermittent sampling interference are destroyed, achieving both suppression and deception interference effects.

[0105] Example 2

[0106] This embodiment provides an intermittent sampling interference method based on pseudo-random sequence frequency shift modulation, such as Figure 4 and Figure 5 As shown, including:

[0107] S1: Intermittently sample the enemy radar signal to obtain an intermittent sampling signal; the specific method is:

[0108] S1.1: Intercept enemy radar signals and analyze their parameters;

[0109] S1.2: Construct intermittent sampling forwarding pulses based on the parameters of the enemy radar signal;

[0110] The intercepted enemy radar signal is recorded as x(t), and its parameters include signal bandwidth B, pulse width T p , FM slope k f and signal-to-interference ratio JSR; based on the pulse width T of the enemy radar signal p , set the intermittent sampling period of the intermittent sampling forwarding pulse to T s , the number of intermittent sampling periods is The intermittent sampling pulse width is τ, and T s ≥2τ; intermittent sampling forwarding pulse is:

[0111]

[0112] Where p(t) represents the intermittent sampling forwarding pulse at time t, rect(·) represents the rectangular pulse, δ(·) represents the impulse function, * represents the convolution calculation, and N represents the repetition period index, which is an integer.

[0113] S1.3: Construct an intermittent sampling signal based on the enemy radar signal and the intermittent sampling forwarding pulse;

[0114] Multiply the enemy radar signal with the intermittent sampling forwarding pulse to obtain the intermittent sampling signal:

[0115] s J (t)=(t)·(t)

[0116] Where s J (t) represents the intermittent sampling signal at time t.

[0117] S2: Set the pseudo-random sequence and frequency shift amount, build a frequency shift amount function, and build a frequency shift modulation function based on the frequency shift amount function; the specific method is:

[0118] like Figure 6 As shown, [(i-1)T s ,T s ] is recorded as the i-th intermittent sampling period, and the pseudo-random sequence c is set i,k and frequency shift ξ i,k , the width of the pseudo-random sequence is T c , where c i,k represents the kth pseudo-random sequence value in the i-th intermittent sampling period, ξ i,k It represents the frequency shift amount controlled by the kth pseudo-random sequence width in the i-th intermittent sampling period, The pseudo-random sequence values ​​from 0 to n-1 in the i-th intermittent sampling period are denoted as c i,0 to c i,n-1 , the corresponding frequency shift amount from 0 to n-1 in the i-th intermittent sampling period is recorded as ξ i,0 To i,n-1 , construct the frequency shift function:

[0119]

[0120] Where f(t) represents the frequency shift function at time t;

[0121] Construct the frequency shift modulation function based on the frequency shift amount function:

[0122] u(t)= j2π·f(t)·

[0123] Where u(t) represents the frequency shift modulation function at time t.

[0124] S3: Use the frequency shift modulation function to modulate and forward the intermittent sampling signal to obtain a frequency shift modulation interference signal; the specific method is:

[0125] Use the frequency shift modulation function to modulate and forward the intermittent sampling signal, and set the maximum forwarding times of intermittent sampling to Where tao represents the duty cycle, tao = τ / T s ; The delay time of the mth forwarding is t d,m=mτ, then the frequency shift modulation interference signal is:

[0126]

[0127] Where s JC (t) represents the frequency shift modulation interference signal at time t.

[0128] S4: performing matched filtering on the frequency shift modulated interference signal to obtain a filtered interference signal;

[0129] The filtered interference signal is specifically:

[0130]

[0131] Where y JC (t) represents the filtered interference signal at time t, f s Indicates the frequency of intermittent sampling forwarding pulses, n represents the order of the Sa(*) function, which is an integer.

[0132] S5: Analyze the filtered interference signal to obtain the optimal frequency shift matrix; the specific method is:

[0133] Let y m (t) = g(t)*x(t-mτ), the interference signal y after filtering JC (t) is divided into two parts; the first part is the interference signal after the 0-order false target is filtered, which is used to generate the 0-order false target, specifically:

[0134]

[0135] Where, represents the interference signal after filtering of the 0th order false target at time t;

[0136] The second part is the interference signal after filtering of the secondary false target group, which is used to generate the secondary false target group. Specifically:

[0137]

[0138] Where, shows the interference signal after filtering of the secondary false target group at time t;

[0139] The amplitude of the 0th order false target is determined by the intermittent sampling pulse width τ and the intermittent sampling period T s and frequency shift modulation function e j2π·f(t)·t It is jointly determined by the intermittent sampling pulse width and inversely proportional to the intermittent sampling period; the secondary false target group is composed of and frequency shift modulation function e j2π·f(t)· Modulation generation;

[0140] Set the interference bandwidth of the intermittent sampling signal in each intermittent sampling period to B0 = f τ, the interference bandwidth of the precise interference signal modulated by pseudo-random sequence frequency shift is B′0= f T c ; A spectrum with bandwidth B′0 passes through ξ i,k Modulation produces a false target, and the interference peak of the interference signal after filtering is:

[0141]

[0142] The position of the interference peak of the interference signal after filtering is:

[0143]

[0144] Where, (A JC ) i,k A represents the interference peak value of the filtered interference signal modulated by the kth frequency shift amount in the i-th intermittent sampling period, x represents the amplitude of the real target, JSR represents the interference-to-signal ratio of the enemy radar signal; t i,k k represents the position time of the interference peak of the filtered interference signal modulated by the kth frequency shift amount in the i-th intermittent sampling period, f Represents the frequency modulation slope of the enemy radar signal; when ξ i,k >0, the false target moves forward; when ξ i,k When <0, the false target generated moves backward;

[0145] The position times of the interference peaks of any two filtered interference signals are:

[0146]

[0147] To achieve interference superposition, the two frequency shift amounts must satisfy:

[0148] when When , the two frequency shift amounts must satisfy:

[0149]

[0150] when When α and β are both integers, and 0≤α<β≤M J , then the two frequency shift amounts must satisfy:

[0151]

[0152] Set Nth J The last frequency shift amount in an intermittent sampling period is the maximum frequency shift amount, so the maximum frequency shift amount is:

[0153]

[0154] Where, Indicates the maximum frequency shift amount.

[0155] Then the optimal frequency shift matrix is:

[0156] ξ opt =k f τ,2k f τ,…,M J · f τ]

[0157] S6: Substitute the optimal frequency shift matrix into the filtered interference signal to obtain the optimal interference signal; use the optimal interference signal to interfere with the enemy radar.

[0158] In the specific implementation process, the interference effect of the method provided by this embodiment is demonstrated by simulation experiments; the simulation platform is windows10 operating system, and MATLAB2017a software is used to simulate the pulse width T of the enemy radar signal. p =40, bandwidth B = 50MHz, carrier frequency f0 = 3GHz, interference-to-signal ratio JSR = 20dB; sampling frequency f of intermittent sampling forwarding pulse s =200MHz, pulse repetition period PRI = 200us, number of intermittent sampling periods N J =2, intermittent sampling period T s =20, intermittent sampling pulse width τ = 4, intermittent sampling maximum forwarding times M J =4, duty cycle tao=0.2;

[0159] like Figure 7 and Figure 8 As shown in the figure, the time-frequency distribution diagram of the traditional intermittent sampling forwarding interference and the schematic diagram of the interference output after matched filtering processing are respectively; it can be seen from the figure that each delayed forwarding of the intermittent sampling interference forms a group of false target strings, and after 4 forwardings, 4 false target strings are formed. The false target string closest to the real target lags behind by at least one intermittent sampling pulse length; the maximum amplitude of the formed false target strings is the same, both The time-frequency distribution is periodic segmented and repeatedly forwarded, and the false target amplitude, position distribution and time-frequency distribution have strong regularity;

[0160] like Figure 9 and Figure 10The figure shows the time-frequency distribution of the traditional intermittent sampling segmented frequency shifted non-uniform forwarding interference and the interference output after matched filtering when the frequency shift amounts ξ1 = 10 MHz, ξ2 = 12 MHz, ξ3 = 15 MHz, and ξ4 = 10 MHz. As can be seen from the figure, while maintaining the interference signal power, compared to the intermittent sampling interference, the false target string, due to the different frequency shift amounts and non-uniform forwarding, forms a leading false target with different forward distances and amplitudes. The maximum interference amplitude remains 3 dB, which to some extent disrupts the position and amplitude distribution of the interference signal, improving the interference effect. Although non-uniform forwarding changes the maximum amplitude distribution characteristics of the false target string, it also reduces the power of some interference signals. The false target amplitude distribution characteristics and time-frequency distribution characteristics still have a strong regularity.

[0161] like Figure 11 and Figure 12 As shown, the frequency shift amount ξ1=8MHZ,ξ2=12MHZ,ξ3=15MHZ,ξ4=18MHZ, the pseudo-random sequence width T c = 2, the time-frequency distribution diagram of the method proposed in this embodiment and the schematic diagram of the interference output after matched filtering processing; It can be seen from the figure that the time-frequency distribution of the interference signal and the spatial distribution of the false target no longer have a strong regularity; Since the frequency shift amount does not meet the optimal frequency shift amount matrix, Figure 12 It can be seen that the maximum amplitude of the interference signal is 1.76dB, which is mainly caused by the superposition of interference signals with a frequency shift of 0 in the interference signal formed by the fourth delayed forwarding of intermittent sampling; since the difference between any two frequency shifts does not meet This makes it difficult for multiple false targets formed by the width shift frequency modulation of the pseudo-random sequence to superimpose and form a strong false target.

[0162] like Figure 13 and Figure 14 As shown, it is a pseudo-random sequence with width T c =2, the frequency shift amount satisfies the optimal frequency shift amount matrix ξ opt =[5MHZ, 10MHZ, 15MHZ, 20MHZ], the time-frequency distribution diagram of the method proposed in this embodiment and the schematic diagram of the interference output after matched filtering processing; it can be seen from the figure that it can not only generate a leading false target and enhance the interference amplitude, but also destroy the time-frequency distribution characteristics of intermittent sampling interference, and has both deception and suppression interference effects. Figure 13 It can be seen that the time-frequency distribution of intermittent sampling interference modulated by pseudo-random sequence frequency shift is very different from that of traditional intermittent sampling interference. The width and position of the forwarded slices are randomly distributed around the real target. opt=[5MHz, 10MHz, 15MHz, 20MHz], the pseudo-random sequence width signals are superimposed at the same position after frequency shifting. The superposition of the five sequence width signals forms a false target interference amplitude of up to 4dB, and the interference distribution after superposition does not conform to the time-frequency and amplitude distribution characteristics of traditional intermittent sampling interference.

[0163] like Figure 15 and Figure 16 As shown, it is a pseudo-random sequence with width T c =1, the frequency shift amount satisfies the optimal frequency shift amount matrix ξ opt =[5MHZ, 10MHZ, 15MHZ, 20MHZ], a schematic diagram of the time-frequency distribution of the interference signal generated by the method proposed in this embodiment and the interference output after matched filtering processing; and Figure 13 and Figure 14 In comparison, the smaller pseudo-random sequence width leads to worse regularity in the time-frequency distribution and the interference amplitude distribution. While ensuring a higher interference power, the interference formed is mostly suppressive interference, which is not easy to be identified by enemy radar.

[0164] Example 3

[0165] This embodiment provides an intermittent sampling interference system based on pseudo-random sequence frequency shift modulation, such as Figure 17 As shown, including:

[0166] An intermittent sampling module is used to intermittently sample enemy radar signals to obtain intermittent sampling signals;

[0167] A frequency shift modulation function construction module is used to set a pseudo-random sequence and a frequency shift amount, construct a frequency shift amount function, and construct a frequency shift modulation function based on the frequency shift amount function;

[0168] The frequency shift modulation forwarding module uses the frequency shift modulation function to modulate and forward the intermittent sampling signal to obtain the frequency shift modulation interference signal;

[0169] A matched filtering module is used to perform matched filtering on the frequency shift modulation interference signal to obtain a filtered interference signal;

[0170] The signal analysis module is used to analyze the interference signal after filtering to obtain the optimal frequency shift matrix;

[0171] The jamming signal construction transmitting module is used to substitute the optimal frequency shift matrix into the filtered jamming signal to obtain the optimal jamming signal; and use the optimal jamming signal to jam the enemy radar.

[0172] The same or similar reference numerals correspond to the same or similar components;

[0173] The terms used in the drawings to describe positional relationships are for illustrative purposes only and should not be construed as limiting this patent;

[0174] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. An intermittent sampling interference method based on pseudo-random sequence frequency shift modulation, characterized in that: include: S1: intermittently sample the enemy radar signal to obtain an intermittent sampling signal; S2: Set the pseudo-random sequence and frequency shift amount, construct a frequency shift amount function, and construct a frequency shift modulation function based on the frequency shift amount function; S3: Use the frequency shift modulation function to modulate and forward the intermittent sampling signal to obtain a frequency shift modulation interference signal; S4: Perform matched filtering on the frequency shift modulation interference signal to obtain a filtered interference signal, specifically: Where y JC (t) represents the filtered interference signal at time t, f s Indicates the frequency of intermittent sampling forwarding pulses, n represents the order of Sa(*) function, which is an integer; s JC (t) represents the frequency shift modulation interference signal at time t, M J represents the maximum number of intermittent sampling forwarding times, τ represents the intermittent sampling pulse width, x(t) represents the intercepted enemy radar signal, and f(t) represents the frequency shift function at time t; S5: Analyze the filtered interference signal to obtain the optimal frequency shift matrix; S6: Substitute the optimal frequency shift matrix into the filtered interference signal to obtain the optimal interference signal; use the optimal interference signal to interfere with the enemy radar.

2. The intermittent sampling interference method based on pseudo-random sequence frequency shift modulation according to claim 1 is characterized in that: In step S1, the specific method for obtaining the intermittent sampling signal is: S1.1: Intercept enemy radar signals and analyze their parameters; S1.2: Construct intermittent sampling forwarding pulses based on the parameters of the enemy radar signal; S1.3: Construct an intermittent sampling signal based on the enemy radar signal and the intermittent sampling forwarding pulse.

3. The intermittent sampling interference method based on pseudo-random sequence frequency shift modulation according to claim 2 is characterized in that: The specific method of constructing intermittent sampling forwarding pulses according to the parameters of the enemy radar signal is as follows: The intercepted enemy radar signal is recorded as x(t), and its parameters include signal bandwidth B, pulse width T p , FM slope k f and signal-to-noise ratio JSR; based on the pulse width T of the enemy radar signal p , set the intermittent sampling period of the intermittent sampling forwarding pulse to T s , the number of intermittent sampling periods is The intermittent sampling pulse width is τ, and T s ≥2τ; intermittent sampling forwarding pulse is: Where p(t) represents the intermittent sampling forwarding pulse at time t, rect(·) represents the rectangular pulse, δ(·) represents the impulse function, * represents the convolution calculation, and N represents the repetition period index, which is an integer.

4. The intermittent sampling interference method based on pseudo-random sequence frequency shift modulation according to claim 3 is characterized in that: According to the enemy radar signal and intermittent sampling N represented as the repetition period index, the specific method of constructing the intermittent sampling signal for the integer forwarding pulse is: Multiply the enemy radar signal with the intermittent sampling forwarding pulse to obtain the intermittent sampling signal: s J (t)=x(t)·p(t) Where s J (t) represents the intermittent sampling signal at time t.

5. The intermittent sampling interference method based on pseudo-random sequence frequency shift modulation according to claim 3 is characterized in that: The specific method of step S2 is: [(i-1)T s ,iT s ] is recorded as the i-th intermittent sampling period, and the pseudo-random sequence c is set i,k and frequency shift ξ i,k , the width of the pseudo-random sequence is T c , where c i,k represents the kth pseudo-random sequence value in the i-th intermittent sampling period, ξ i,k It represents the frequency shift amount controlled by the kth pseudo-random sequence width in the i-th intermittent sampling period, The pseudo-random sequence values ​​from 0 to n-1 in the i-th intermittent sampling period are denoted as c i,0 to c i,n-1 , the corresponding frequency shift amount from 0 to n-1 in the i-th intermittent sampling period is recorded as ξ i,0 To i,n-1 , construct the frequency shift function: Where f(t) represents the frequency shift function at time t; Construct the frequency shift modulation function based on the frequency shift amount function: u(t)=e j2π·f(t)·t Where u(t) represents the frequency shift modulation function at time t.

6. The intermittent sampling interference method based on pseudo-random sequence frequency shift modulation according to claim 4 or 5, characterized in that: The specific method of step S3 is: Use the frequency shift modulation function to modulate and forward the intermittent sampling signal, and set the maximum forwarding times of intermittent sampling to Where tao represents the duty cycle, tao = τ / T s ; The delay time of the mth forwarding is mτ, then the frequency shift modulation interference signal is: Where s JC (t) represents the frequency shift modulated interference signal at time t.

7. The intermittent sampling interference method based on pseudo-random sequence frequency shift modulation according to claim 6, characterized in that: In step S5, the specific method for analyzing the filtered interference signal is: Let y m (t) = h(t)*x(t-mτ), the interference signal y after filtering JC (t) is divided into two parts; the first part is the interference signal after the 0-order false target is filtered, which is used to generate the 0-order false target, specifically: Where, represents the interference signal after filtering of the 0th order false target at time t; The second part is the interference signal after filtering of the secondary false target group, which is used to generate the secondary false target group. Specifically: Where, shows the interference signal after filtering of the secondary false target group at time t; The amplitude of the 0th order false target is determined by the intermittent sampling pulse width τ and the intermittent sampling period T s and frequency shift modulation function e j2π·f(t)·t It is jointly determined by the intermittent sampling pulse width and inversely proportional to the intermittent sampling period; the secondary false target group is composed of and frequency shift modulation function e j2π·f(t)·t Modulation generation; Set the interference bandwidth of the intermittent sampling signal in each intermittent sampling period to B0 = k f τ, the interference bandwidth of the precise interference signal modulated by pseudo-random sequence frequency shift is B′0=k f T c ; A spectrum with bandwidth B′0 passes through ξ i,k Modulation produces a false target, and the interference peak of the interference signal after filtering is: The position of the interference peak of the interference signal after filtering is: Where, (A JC ) i,k A represents the interference peak value of the filtered interference signal modulated by the kth frequency shift amount in the i-th intermittent sampling period, x represents the amplitude of the real target, and JSR represents the interference-to-signal ratio of the enemy radar signal; t i,k k represents the position time of the interference peak of the filtered interference signal modulated by the kth frequency shift amount in the i-th intermittent sampling period, f Represents the frequency modulation slope of the enemy radar signal; when ξ i,k >0, the false target moves forward; when ξ i,k When <0, the false target generated moves backward; The position times of the interference peaks of any two filtered interference signals are: To achieve interference superposition, the two frequency shift amounts must satisfy: when When , the two frequency shift amounts must satisfy: when When α and β are both integers, and 0≤α<β≤M J , then the two frequency shift amounts must satisfy: Set Nth J The last frequency shift amount in an intermittent sampling period is the maximum frequency shift amount, so the maximum frequency shift amount is: Where, Indicates the maximum frequency shift amount.

8. The intermittent sampling interference method based on pseudo-random sequence frequency shift modulation according to claim 6, characterized in that: The optimal frequency shift matrix is: x opt =[k f t,2k f τ,…,M J ·k f [t] Where, ξ opt Represents the optimal frequency shift matrix.

9. An intermittent sampling interference system based on pseudo-random sequence frequency shift modulation, characterized in that: include: An intermittent sampling module is used to intermittently sample enemy radar signals to obtain intermittent sampling signals; A frequency shift modulation function construction module is used to set a pseudo-random sequence and a frequency shift amount, construct a frequency shift amount function, and construct a frequency shift modulation function based on the frequency shift amount function; The frequency shift modulation forwarding module uses the frequency shift modulation function to modulate and forward the intermittent sampling signal to obtain the frequency shift modulation interference signal; The matched filter module is used to perform matched filtering on the frequency shift modulation interference signal to obtain the filtered interference signal, specifically: Where y JC (t) represents the filtered interference signal at time t, f s Indicates the frequency of intermittent sampling forwarding pulses, n represents the order of Sa(*) function, which is an integer; s JC (t) represents the frequency shift modulation interference signal at time t, M J represents the maximum number of intermittent sampling forwarding times, τ represents the intermittent sampling pulse width, x(t) represents the intercepted enemy radar signal, and f(t) represents the frequency shift function at time t; The signal analysis module is used to analyze the interference signal after filtering to obtain the optimal frequency shift matrix; The jamming signal construction transmitting module is used to substitute the optimal frequency shift matrix into the filtered jamming signal to obtain the optimal jamming signal; and use the optimal jamming signal to jam the enemy radar.

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