Inter-pulse parameter agile intra-pulse stepped LFM signal design and anti-intermittent sampling repeater jamming processing method

Abstract

The application discloses a pulse-in-step LFM signal design based on pulse parameter agility and an intermittent sampling and forwarding interference processing method, and the method comprises the following steps: pulse-in-step LFM signal generation based on pulse parameter agility, the pulse signal in each pulse repetition interval is divided into M linear frequency modulation sub-pulse signals, the center frequency of each sub-pulse signal has a frequency interval Δf, and the frequency interval Δf of N PRIs in one coherent processing time is agile; the echo signal after intermittent forwarding interference is received at the receiving end, and is converted into a baseband signal through frequency down conversion; the echo signals of N PRIs are subjected to sub-pulse segmentation pulse compression respectively, the interference frequency band sub-pulse is found out according to the pulse compression result, and the interference frequency band is filtered and removed; the echo signal after interference removal is subjected to whole-section pulse compression again; finally, the pulse compression results of N PRIs are subjected to pulse interconnection coherent accumulation. The method solves the problem of single waveform design.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of radar signal processing, and particularly relates to a pulse-in step LFM signal design based on pulse-to-pulse parameter agility and an anti-intermittent sampling and forwarding jamming processing method. BACKGROUND

[0002] Intermittent sampling and forwarding jamming is a new coherent jamming mode based on digital radio frequency memory (DRFM), which has the characteristics of high efficiency, fast response speed, and no need to receive all the signal duration compared with traditional suppressive jamming and deceptive jamming. This mode can form a series of realistic coherent false target groups by intermittently sampling and forwarding the radar echo at a low rate, and the working mode of sampling and forwarding at the same time greatly improves the response speed and jamming efficiency of the jamming. Due to the good jamming performance of intermittent sampling and forwarding jamming, the corresponding anti-jamming measures, i.e. jamming recognition and jamming suppression, and the corresponding waveform design also need further development in order to improve and enhance the defense capability.

[0003] In terms of jamming recognition and suppression, the current research mainly focuses on linear frequency modulation radar systems, which is relatively single. In terms of waveform design, the current method is to encode within the pulse to improve the orthogonality of the waveform, and a large number of complex algorithms are used to achieve the purpose of anti-jamming.

[0004] In summary, with the continuous development of radar jamming methods and forms in electronic warfare, intermittent sampling and forwarding jamming has gradually become an effective and difficult-to-counter jamming method. There are two main problems in the current anti-jamming technology. One is that the selection of jamming recognition and anti-jamming measures often needs to rely on artificial judgment, and the intelligent level of anti-jamming needs to be improved. The other is that most radars still use traditional single and determined transmission waveforms, and the anti-intermittent sampling and forwarding jamming waveform design is relatively single. SUMMARY

[0005] In order to solve the problems of low anti-jamming intelligent level and single anti-jamming waveform in the existing anti-intermittent sampling and forwarding jamming technology, the present application provides a pulse-in step LFM signal design based on pulse-to-pulse parameter agility and an anti-intermittent sampling and forwarding jamming processing method.

[0006] The technical solution for achieving the purpose of the present application is: a pulse-in step LFM signal design based on pulse-to-pulse parameter agility and an anti-intermittent sampling and forwarding jamming processing method, which comprises:

[0007] Step 1, at the transmitting end, a pulse-to-pulse parameter agile intra-pulse stepped LFM signal is generated; the pulse signal in each pulse repetition interval (PRI) is divided into M linear frequency modulation (LFM) sub-pulse signals, the center frequency of each sub-pulse signal has a frequency interval Δf, and the Δf is constant in the same PRI and is agile in N PRIs in a coherent processing time;

[0008] Step 2, the receiving end receives the echo signal after intermittent retransmission interference, and converts the echo signal into a baseband signal through down-conversion;

[0009] Step 3, the echo signals of N PRIs in a coherent processing interval (CPI) are respectively subjected to sub-pulse segmentation and pulse compression;

[0010] Step 4, the sub-pulse pulse compression results are detected through an adaptive threshold, the interference frequency band sub-pulse is found out according to the pulse compression results, and the interference frequency band is filtered out;

[0011] Step 5, the echo signals of N PRIs after interference elimination are subjected to whole-section pulse compression again;

[0012] Step 6, the whole-section pulse compression results of N PRIs are subjected to pulse-to-pulse coherent accumulation to obtain an anti-interference signal processing result.

[0013] Further, the pulse width of the pulse-to-pulse parameter agile intra-pulse stepped LFM signal in step 1 is:

[0014] T=Mt sub (1)

[0015] Wherein, t sub is the pulse width of the sub-pulse;

[0016] The signal bandwidth of the mth PRI of the pulse-to-pulse parameter agile intra-pulse stepped LFM signal is:

[0017] B m =B sub +(M-1)Δf (2)

[0018] Wherein, B sub is the sub-pulse bandwidth; Δf is the frequency interval between the sub-pulses;

[0019] The frequency modulation slope of the sub-pulse of the pulse-to-pulse parameter agile intra-pulse stepped LFM signal is:

[0020] K=B sub / t sub (3)

[0021] The pulse-to-pulse parameter agile intra-pulse stepped LFM signal is:

[0022]

[0023] wherein x n (t) is the intra-pulse stepped LFM signal of the nth PRI; Δf n is the sub-pulse frequency interval of the nth PRI.

[0024] Further, the echo signal is:

[0025] K = B sub / t sub x r_isrj_n (t) = x r_n (t) + x isrj_n (t) + n(t) (5)

[0026] wherein x r_isrj_n (t) is the jammed echo signal of the nth PRI, x r_n (t) is the echo signal of the nth PRI, x isrj_n (t) is the intermittent retransmission jamming signal of the nth PRI, and n(t) is the noise signal.

[0027] X isrj_n (t) is the intermittent sampling direct retransmission jamming signal:

[0028]

[0029] wherein τ is the sampling pulse width, t s is the sampling repetition period, δ(t) represents the impulse function, and x n (t) is the intra-pulse stepped LFM signal of the nth PRI.

[0030] Further, the output signal of the echo signal of the nth PRI in step 3 through the mth sub-matched filter of the nth matched filter group is:

[0031] x pc_n_m (t) = x r_n *h n_m (7)

[0032] wherein x pc_n_m (t) is the output signal of the echo signal of the nth PRI through the mth sub-matched filter of the nth matched filter group, h n_m (t) is the matching function of the mth sub-pulse matched filter of the nth PRI, and * represents convolution calculation.

[0033] Further, step 4 comprises:

[0034] The mean of the variance of each sub-pulse pulse pressure result is taken as an adaptive threshold for threshold detection, and the sub-pulse exceeding the threshold is the disturbed sub-pulse, which needs to be removed by filtering, and the echo signal after interference removal is:

[0035] y(t)=x isrj_n (t)*x f (t) (8)

[0036] Wherein, y(t) is the echo signal after interference removal x f (t) is the interference frequency band corresponding to the anti-interference filter.

[0037] Further, step 5 includes:

[0038] The echo signal of N PRI after interference rejection is re-pulse compressed in the whole section, and the pulse compression result is:

[0039] x pc_n (t)=x r_n *h n (9)

[0040] Wherein, x pc_n (t) is the output signal of the nth PRI anti-interference signal through the matching filter corresponding to the nth PRI echo signal, h n (t) is the matching function of the matching filter corresponding to the nth PRI echo signal.

[0041] Further, step 6 includes: the pulse compression results of N PRI are subjected to inter-pulse coherent accumulation to obtain the anti-interference signal processing result.

[0042] A computer device includes a memory, a processor, and a computer program stored on the memory and executable on the processor, and the processor executes the program to realize the steps of the above method.

[0043] A computer readable storage medium, which stores a computer program, the program is executed by the processor to realize the steps of the above method.

[0044] A computer program product, comprising a computer program, which is executed by the processor to realize the steps of the above method.

[0045] Compared with the prior art, the present application has the following advantages: the present application can actively carry out intermittent sampling and forwarding interference detection, and solves the problem of low intelligent level of anti-interference; the present application proposes a pulse-to-pulse parameter agile intra-pulse stepped LFM signal, and solves the problem of single waveform design; the present application improves the ability of detecting the disturbed sub-pulse and distinguishing true and false pulses through sub-pulse segmentation and pulse compression and adaptive threshold detection, and can effectively detect and remove the intermittent sampling and forwarding interference under low signal-to-interference ratio; the present application can solve the problem of distance resolution loss caused by pulse-to-pulse accumulation through whole-segment re-pulse compression of the de-interference echo signal; the present application can solve the grating lobe problem caused by intra-pulse stepped LFM pulse compression through pulse-to-pulse frequency interval parameter agility and pulse-to-pulse coherent accumulation of the pulse compression signal. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is a flowchart of a pulse-to-pulse parameter agile intra-pulse stepped LFM signal design and anti-intermittent sampling and forwarding interference processing method provided by the present application.

[0047] Fig. 2(a) is a time-frequency relationship diagram of a pulse-to-pulse parameter agile intra-pulse stepped LFM signal provided by the present application, and Fig. 2(b) is a pulse-to-pulse agility diagram of intra-pulse stepped frequency Δf.

[0048] Fig. 3(a) and Fig. 3(b) are a time-domain real part diagram and a frequency spectrum diagram of a pulse-to-pulse parameter agile intra-pulse stepped LFM signal provided by the present application.

[0049] Fig. 4(a) and Fig. 4(b) are a time-domain real part diagram and a frequency spectrum diagram of echo data containing a target and interference provided by the present application.

[0050] Figure 5 is a direct pulse compression result diagram of disturbed echo data provided by the present application;

[0051] Figures 6(a)-6(g) is a pulse compression result diagram of echo data through sub-pulse matched filters provided by the present application;

[0052] Figure 7 is a de-interference signal processing result diagram of echo data provided by the present application. DETAILED DESCRIPTION

[0053] In order to more clearly illustrate the technical means and anti-interference effect of the present application, the following will be further described in combination with the drawings and specific embodiments.

[0054] Please refer to Figure 1 , Figure 1A flowchart of a pulse-to-pulse parameter agile intra-pulse stepped LFM signal design and intermittent sampling retransmission interference processing method is provided. The application provides a pulse-to-pulse parameter agile intra-pulse stepped LFM signal design and intermittent sampling retransmission interference processing method, which comprises the following steps.

[0055] Step 1, at the transmitting end, the generation method of the pulse-to-pulse parameter agile intra-pulse stepped LFM signal is to divide the pulse signal in each pulse repetition interval (PRI) into M linear frequency modulation sub-pulse signals, the center frequency of each sub-pulse signal has a certain frequency interval Δf, and Δf is constant in the same PRI, and is agile in N PRIs in a coherent processing interval (CPI).

[0056] According to the principle of intermittent sampling retransmission interference, the specific process of interference generation is that the DRFM of the jammer collects radar signals of a predetermined length; after the collection is completed, the collected signals are retransmitted; after the retransmission is completed, the sampling and retransmission process is repeatedly alternated.

[0057] Specifically, the pulse-to-pulse parameter agile intra-pulse stepped LFM signal has a pulse width of T, the signal bandwidth of the mth PRI is B m , and the sub-pulse frequency modulation slope K is:

[0058] T=Mt sub (10)

[0059] Where t sub is the pulse width of the sub-pulse;

[0060] B m =B sub +(M-1)Δf (11)

[0061] Where B sub is the sub-pulse bandwidth; Δf is the frequency interval between sub-pulses;

[0062] K=B sub / t sub (12)

[0063] The time-frequency relationship diagram of the pulse-to-pulse parameter agile intra-pulse stepped LFM signal and the pulse-to-pulse agile intra-pulse stepped frequency Δf are shown in FIG. 2.

[0064] Then the pulse-to-pulse parameter agile intra-pulse stepped LFM signal can be written as:

[0065]

[0066] Where xn (t) is the intra-pulse stepped LFM signal of the nth PRI; Δf n is the sub-pulse frequency interval of the nth PRI.

[0067] When designing the waveform at the transmitting end, the frequency modulation slope, the starting frequency, and the pulse segmentation number M of the sub-pulse can be arbitrarily planned. The more the pulse segmentation number M is, the better the signal anti-intermittent sampling retransmission interference performance is, but the more the hardware resource occupation of the signal processing procedure is.

[0068] Step 2, the receiving end receives the echo signal interfered by intermittent retransmission, and performs down-conversion to a baseband signal;

[0069] Specifically, a low-pass filter is designed according to the waveform design of the transmitting end, the echo signal is down-converted at the receiving end, the down-converted echo signal is low-pass filtered, and a baseband signal for subsequent signal processing is obtained.

[0070] The time-domain expression of the baseband echo signal is:

[0071] x r_isrj_n (t) = x r_n (t) + x isrj_n (t) + n(t) (14)

[0072] Wherein, x r_isrj_n (t) is the interfered echo signal of the nth PRI, x r_n (t) is the echo signal of the nth PRI, x isrj_n (t) is the intermittent retransmission interference signal of the nth PRI, and n(t) is a noise signal.

[0073] X isrj_n (t) takes the intermittent sampling direct retransmission interference signal as:

[0074]

[0075] Wherein, τ is the sampling pulse width, t s is the sampling repetition period, δ(t) represents an impulse function, and x n (t) is the intra-pulse stepped LFM signal of the nth PRI.

[0076] Step 3, the echo signals of N PRIs in a CPI are respectively segmented and pulse-inverted by sub-pulses.

[0077] Specifically, a corresponding sub-pulse matched filter group is designed according to the transmitting waveform, and the down-converted baseband echo signal is segmented and pulse-inverted.

[0078] The echo signal of the nth PRI passes through the output signal of the mth sub-matched filter of the nth matched filter group:

[0079] x pc_n_m (t)=x r_n *h n_m (16)

[0080] Wherein, x pc_n_m (t) is the output signal of the mth sub-matched filter of the nth matched filter group of the echo signal of the nth PRI, h n_m (t) is the matching function of the mth sub-pulse matched filter of the nth PRI, and * represents convolution calculation.

[0081] Step 4, the sub-pulse pulse compression result is detected by an adaptive threshold, and the sub-pulse of the disturbed frequency band is found out according to the pulse compression result, and the disturbed frequency band is filtered and removed;

[0082] Specifically, since the signal power of the intermittent forwarding sampling interference is much larger than the real echo signal, the peak power of the interference signal after pulse compression will be much larger than the real signal, so the disturbed sub-pulse can be detected by power threshold. The specific process is that the mean value of the variance of each sub-pulse pulse compression result is taken as an adaptive threshold, and the signal threshold detection after sub-pulse pulse compression is performed, and the sub-pulse exceeding the threshold is regarded as a disturbed sub-pulse, which needs to be removed by filtering the disturbed frequency band.

[0083] The echo signal after interference removal is:

[0084] y(t)=x isrj_n (t)*x f (t) (17)

[0085] Wherein, y(t) is the echo signal x f (t) after interference removal, and h pc_n (t) is the anti-interference filter corresponding to the interference frequency band.

[0086] Step 5, the echo signal of the N PRI after removing the interference is re-pulse compressed in the whole segment;

[0087] Specifically, since the pulse compression frequency band of the sub-pulse is 1 / M of the original signal frequency band, the segmented pulse compression result has a problem of distance resolution loss compared with the whole segment pulse compression signal of the original signal, therefore, the whole segment pulse compression is continued on the echo signal after removing the interference, and the pulse compression result is:

[0088] x pc_n (t)=x r_n (t)*h n (t) (18)

[0089] Wherein, x pc_n(t) is the output signal of the nth PRI echo signal through the matched filter corresponding to the nth PRI. n (t) is the matched function of the matched filter corresponding to the nth PRI echo signal.

[0090] Step 6, the pulse-to-pulse coherent accumulation is performed on the whole pulse compression results of N PRIs.

[0091] Specifically, the whole pulse compression of the intra-pulse stepped LFM signal exists the grating lobe problem caused by the rectangular windowing, the transmitting signal adopted by the present application is the intra-pulse frequency interval agile, the grating lobe of each PRI is non-coherent, therefore, the pulse-to-pulse coherent accumulation is performed on the whole pulse compression results of N PRIs to obtain the anti-interference signal processing result.

[0092] The present application provides a kind of intra-pulse stepped LFM signal design and anti-intermittent sampling retransmission interference processing method based on pulse-to-pulse parameter agile, which can be used to realize the inhibition to intermittent sampling retransmission interference.

[0093] The effect of the present application will be further described below in combination with simulation experiment, and its simulation parameters are shown in Table 1.

[0094] Table 1 simulation parameters

[0095]

[0096] Figures 3(a)-3(b) It is the time domain real part image and frequency domain image of the intra-pulse stepped LFM signal based on pulse-to-pulse parameter agile. After observation, it can be known that the intra-pulse stepped LFM signal based on pulse-to-pulse parameter agile designed by the simulation of the present application is divided into 7 segments in time domain, the frequency bands of each sub-pulse are jumped in frequency domain, there is a certain frequency interval, and the sub-pulses have orthogonality, which is helpful for mutual cover between sub-pulses.

[0097] Figures 4(a)-4(b) It is the time domain real part image and frequency domain image of the echo signal of intermittent sampling retransmission interference. After observation, it can be known that the echo signal contains target echo signal, retransmission interference signal and noise signal at the same time, the 2nd, 4th and 6th sub-pulses of transmitting signal are interfered by retransmission interference, while the 1st, 3rd, 5th and 7th sub-pulses are not sampled by interference machine, and the energy of the interfered sub-pulse frequency band is greater than that of the uninterfered frequency band.

[0098] Figure 5It is a direct pulse compression result figure of the echo data interfered. It can be observed that there are two target peaks with a distance of 1.5 km after pulse compression, wherein the pulse compression peak at 1.5 km is a real target, and the pulse compression peak at 3 km is an interference target. The power of the pulse compression result of the interference signal is about 13 dB greater than that of the real target, which will lead to the failure to distinguish the real signal and the interference signal, and further interfere with the signal processing result. Meanwhile, based on the characteristics that the power of the interference signal is much greater than that of the real target, the sub-pulse frequency band interfered can be detected by power threshold detection.

[0099] Figures 6(a)-6(g) It is a result figure of the echo data processed by the sub-pulse matched filter for pulse compression. It can be observed that, since the sub-pulses in the 2nd, 4th and 6th segments are interfered by the intermittent sampling and forwarding, there are a high-power interference target and a relatively small-power real target in the segmented pulse compression result. Meanwhile, the sub-pulses in the 1st, 3rd, 5th and 7th segments are not interfered, so there is only one real target. The interfered sub-pulses can be detected by the adaptive threshold, and further interference elimination is completed.

[0100] Figure 7 It is a signal processing result figure of the signal processed by the pulse interval parameter agile pulse internal stepped LFM signal design and intermittent sampling and forwarding interference processing method. It can be observed that, by using the pulse interval parameter agile pulse internal stepped LFM signal design and intermittent sampling and forwarding interference processing method, the target echo distance of the signal processing is 1.5 km, which is consistent with the set value, and there is no interference target in the signal processing. It can be concluded that the pulse interval parameter agile pulse internal stepped LFM signal design and intermittent sampling and forwarding interference processing method can effectively detect and suppress the intermittent sampling and forwarding interference signal.

[0101] The above is a further detailed description of the present application in combination with the specific preferred embodiments, and the specific implementation of the present application cannot be limited to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, some simple deductions or substitutions can be made without departing from the concept of the present application, and all of them shall be regarded as falling within the protection scope of the present application.

Claims

1. A method for designing intra-pulse stepped LFM signals based on inter-pulse parameter agility and for handling interference from intermittent sampling and forwarding, characterized in that, Includes the following steps: Step 1: At the transmitting end, generate an intra-pulse stepping LFM signal with pulse parameter agility; divide the pulse signal within each pulse repetition interval into M linear frequency modulated sub-pulse signals, the center frequency of each sub-pulse signal has a frequency interval Δf, and Δf is constant within the same PRI, but agile between N PRIs in one coherent processing time; Step 2: The receiving end receives the echo signal after intermittent forwarding interference and performs down-conversion to convert it into a baseband signal; Step 3: Perform segmented pulse compression on the echo signals of N PRIs within a CPI. Step 4: The sub-pulse compression results are detected by adaptive threshold detection. The sub-pulses in the interference frequency band are identified based on the pulse compression results, and the interference frequency bands are filtered out. Step 5: Re-compress the entire pulse segment of the echo signal of N PRI after removing interference; Step 6: Perform inter-pulse coherent accumulation on the pulse compression results of N PRIs to obtain the anti-interference signal processing results.

2. The method for designing intra-pulse stepped LFM signals based on inter-pulse parameter agility and processing interference against intermittent sampling and forwarding as described in claim 1, is characterized in that, In step 1, the pulse width of the intra-pulse stepping LFM signal with inter-pulse parameter agility is: T=Mt sub (1) Among them, t sub The pulse width of the sub-pulse; The signal bandwidth of the m-th PRI of the pulse parameter agile intra-pulse stepping LFM signal is: B m =B sub +(M-1)Δf (2) Among them, B sub Δf is the sub-pulse bandwidth; Δf is the frequency interval between sub-pulses. The sub-pulse frequency modulation slope of the inter-pulse parameter agile intra-pulse stepped LFM signal is: K=B sub / t sub (3) 3. The method for designing intra-pulse stepped LFM signals based on inter-pulse parameter agility and processing interference against intermittent sampling and forwarding as described in claim 2, is characterized in that, The inter-pulse parameter agile intra-pulse stepping LFM signal is: Where, x n (t) represents the intra-pulse stepping LFM signal of the nth PRI; Δf n The sub-pulse frequency interval of the nth PRI.

4. The method for designing intra-pulse stepped LFM signals based on inter-pulse parameter agility and processing intermittent sampling and forwarding interference according to claim 3, characterized in that, The echo signal is: x r_isrj_n (t)=x r_n (t)+x isrj_n (t)+n(t) (5) Where, x r_isrj_n (t) represents the interfered echo signal of the nth PRI, x r_n (t) represents the echo signal of the nth PRI, x isrj_n (t) represents the intermittent relay interference signal of the nth PRI, and n(t) represents the noise signal; X isrj_n (t) Take the intermittent sampling and direct forwarding interference signal as: Where τ is the sampling pulse width, t s Let δ(t) represent the sampling repetition period, and x be the impulse function. n (t) represents the intra-pulse stepping LFM signal of the nth PRI.

5. The method for designing intra-pulse stepped LFM signals based on inter-pulse parameter agility and processing interference against intermittent sampling and forwarding, as described in claim 4, is characterized in that... The output signal of the echo signal of the nth PRI in step 3, after passing through the mth sub-matched filter of the nth matched filter bank, is: x pc_n_m (t)=x r_n (t)*h n_m (t) (7) Where, x pc_n_m (t) represents the output signal of the echo signal of the nth PRI passing through the mth sub-matched filter of the nth matched filter bank, h. n_m (t) is the matching function of the m-th sub-pulse matched filter of the n-th PRI, and * indicates convolution calculation.

6. The method for designing intra-pulse stepped LFM signals based on inter-pulse parameter agility and processing interference against intermittent sampling and forwarding, as described in claim 5, is characterized in that... Step 4 includes: The mean of the variance of each sub-pulse compression result is taken as the adaptive threshold for threshold detection. Sub-pulses that exceed the threshold are considered interfered sub-pulses and need to be filtered out. The echo signal after interference removal is as follows: y(t)=x isrj_n (t)*x f (t) (8) Where y(t) is the echo signal x after interference removal. f (t) represents the interference removal filter corresponding to the interference frequency band.

7. The method for designing and processing intermittent sampling and forwarding interference based on inter-pulse parameter agility of intra-pulse stepped LFM signal according to claim 6, characterized in that, Step 5 includes: re-compressing the entire pulse segment of the echo signals of the N PRIs after interference removal, and the pulse compression result is: x pc_n (t)=x r_n (t)*h n (t) (9) Where, x pc_n (t) represents the output signal of the matched filter corresponding to the echo signal of the nth PRI after the interference removal signal of the nth PRI, h n (t) is the matched function of the matched filter corresponding to the nth PRI echo signal.

8. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps of any of the methods described in claims 1-7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the program implements the steps of the method described in any one of claims 1-7.

10. A computer program product, comprising a computer program, characterized in that, When executed by a processor, the computer program implements the steps of the method described in any one of claims 1-7.

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