Inter-pulse parameter agility-based in-pulse stepping LFM signal design and anti-intermittent sampling and forwarding interference processing method

Abstract

The invention discloses an inter-pulse parameter agility-based intra-pulse stepping LFM (Linear Frequency Modulation) signal design and intermittent sampling and forwarding interference resisting processing method, which comprises the following steps of: generating an inter-pulse parameter agility intra-pulse stepping LFM signal, dividing a pulse signal in each pulse repetition interval into M linear frequency modulation sub-pulse signals, the center frequency of each sub-pulse signal has a frequency interval delta f, and the frequency interval delta f among N PRIs in one coherent processing time is agile; a receiving end receives the echo signal subjected to intermittent forwarding interference, and performs down-conversion to convert the echo signal into a baseband signal; the N PRI echo signals are subjected to segmented pulse compression of sub-pulses, the sub-pulses of the interfered frequency band are found out according to the pulse compression result, and the interfered frequency band is filtered and removed; carrying out whole-section pulse compression on the echo signal after interference elimination again; and finally, performing inter-pulse coherent accumulation on the pulse pressure results of the N PRIs. The method solves the problem that the waveform design is relatively single.

Description

Technical Field

[0001] The present invention belongs to the technical field of radar signal processing, and in particular relates to an intra-pulse stepped LFM signal design based on inter-pulse parameter agility and an anti-intermittent sampling forwarding interference processing method. Background Art

[0002] Intermittent sampling and forwarding jamming is a new type of coherent jamming method based on digital radio frequency memory (DRFM). Compared with traditional suppression jamming and deceptive jamming, it has the characteristics of high efficiency, fast response speed, and no need to receive the full-duration signal. This method can form a series of realistic coherent false target groups by performing low-rate intermittent sampling and forwarding of radar echoes, and the sampling and forwarding working mode greatly improves the jamming response speed and jamming efficiency. Due to the good jamming performance shown by intermittent sampling and forwarding jamming, in order to improve and strengthen its own defense capabilities, its corresponding anti-jamming measures - jamming identification and jamming suppression and corresponding waveform design also need further development.

[0003] Regarding the technology of anti-intermittent sampling and forwarding interference, in terms of interference identification and suppression, the current research mainly focuses on linear frequency modulation radar systems, which is relatively simple. In terms of waveform design, it is usually achieved by encoding 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-interference.

[0004] In general, with the continuous development of radar interference methods and forms in electronic warfare, intermittent sampling and forwarding interference has gradually become an effective and difficult-to-counter interference method. There are two major problems with current anti-interference technology. One is that interference identification and the selection of anti-interference measures often require manual judgment, and the level of intelligence of anti-interference needs to be improved; the other is that most radars still use the traditional single, deterministic transmission waveform, and the waveform design for anti-intermittent sampling and forwarding interference is relatively simple. Summary of the invention

[0005] In order to solve the problems of low anti-interference intelligence level and relatively single anti-interference waveform in the existing anti-interference technology of intermittent sampling and forwarding, the present invention provides a pulse-stepped LFM signal design based on inter-pulse parameter agility and an anti-intermittent sampling and forwarding interference processing method.

[0006] The technical solution to achieve the purpose of the present invention is: a pulse-by-pulse step LFM signal design based on pulse-by-pulse parameter agility and an anti-intermittent sampling forwarding interference processing method, the method comprising:

[0007] Step 1: At the transmitting end, generate an intra-pulse step LFM signal with agile inter-pulse parameters; divide the pulse signal in each pulse repetition interval into M linear frequency modulation sub-pulse signals, the center frequency of each sub-pulse signal has a frequency interval Δf, and Δf is constant within the same PRI and is agile between N PRIs in a coherent processing time;

[0008] Step 2: The receiving end receives the echo signal after the intermittent forwarding interference, and down-converts it into a baseband signal;

[0009] Step 3, performing segmented pulse compression of sub-pulses on the echo signals of N PRIs within a CPI;

[0010] Step 4: The sub-pulse pulse pressure result is detected by an adaptive threshold, and the sub-pulse of the interfered frequency band is found according to the pulse pressure result, and the interfered frequency band is filtered out;

[0011] Step 5, re-performing pulse compression on the entire segment of the N PRI echo signals after eliminating interference;

[0012] Step 6: Perform inter-pulse coherent accumulation on the entire pulse pressure results of N PRIs to obtain an anti-interference signal processing result.

[0013] Furthermore, the pulse width of the intra-pulse step LFM signal with inter-pulse parameter agility in step 1 is:

[0014] T=Mt sub (1)

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

[0016] The signal bandwidth of the mth PRI of the intra-pulse step LFM signal with inter-pulse parameter agility is:

[0017] B m =B sub +(M-1)Δf (2)

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

[0019] The sub-pulse frequency modulation slope of the intra-pulse step LFM signal with inter-pulse parameter agility is:

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

[0021] The intra-pulse step LFM signal of the inter-pulse parameter agility is:

[0022]

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

[0024] Furthermore, 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] Among them, 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 forwarding interference signal of the nth PRI, and n(t) is the noise signal;

[0027] X isrj_n (t) Take intermittent sampling and directly forward the interference signal as:

[0028]

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

[0030] Furthermore, 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] Among them, x pc_n_m (t) is the output signal of the nth PRI echo signal passing through the mth sub-matched filter of the nth matched filter group, h n_m (t) is the matching function of the m-th sub-pulse matched filter of the n-th PRI, and * represents the convolution calculation.

[0033] Furthermore, step 4 includes:

[0034] The mean of the variance of the pulse pressure results of each sub-pulse is taken as the adaptive threshold for threshold detection. The sub-pulse that exceeds the threshold is the interfered sub-pulse and needs to be removed by filtering. The echo signal after interference removal is:

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

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

[0037] Furthermore, step 5 includes:

[0038] After removing the interference, the echo signals of N PRIs are pulse compressed again, and the pulse compression results are:

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

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

[0041] Furthermore, step 6 includes: performing inter-pulse coherent accumulation on the entire pulse compression results of the N PRIs to obtain an anti-interference signal processing result.

[0042] A computer device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the steps of the above method are implemented when the processor executes the program.

[0043] A computer-readable storage medium stores a computer program, which implements the steps of the above method when executed by a processor.

[0044] A computer program product comprises a computer program, which implements the steps of the above method when executed by a processor.

[0045] Compared with the prior art, the significant advantages of the present invention are as follows: the present invention can actively perform intermittent sampling forwarding interference detection, thereby solving the problem of low intelligent level of anti-interference; the present invention proposes an intra-pulse stepped LFM signal with agile inter-pulse parameters, thereby solving the problem of relatively single waveform design; the present invention improves the ability to detect interfered sub-pulses and distinguish true and false pulses through sub-pulse segmented pulse pressure and adaptive threshold detection, thereby realizing effective detection and removal of intermittent forwarding sampling interference under low signal-to-interference ratio conditions; the present invention can solve the problem of distance resolution loss caused by the accumulation of traditional segmented pulse pressure between pulses by performing whole-segment re-pulse pressure on the de-interference echo signal; the present invention can solve the problem of grating lobe caused by intra-pulse stepped LFM pulse compression through parameter agility of inter-pulse frequency interval and coherent accumulation of inter-pulse pulse pressure signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a flow chart of a method for designing an intra-pulse stepped LFM signal based on inter-pulse parameter agility and resisting intermittent sampling and forwarding interference processing provided by the present invention.

[0047] FIG2(a) is a time-frequency relationship diagram of an intra-pulse stepped LFM signal with agile inter-pulse parameters provided by the present invention, and FIG2(b) is a schematic diagram of the inter-pulse agility of the intra-pulse step frequency Δf.

[0048] FIG. 3( a ) and FIG. 3( b ) are a time domain real part diagram and a spectrum diagram of an intra-pulse stepped LFM signal with agile inter-pulse parameters provided by the present invention.

[0049] FIG. 4( a ) and FIG. 4( b ) are time domain real parts and frequency spectrum diagrams of echo data including a target and interference provided by the present invention.

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

[0051] Figure 6(a)-Figure 6(g) It is a result diagram of echo data provided by the present invention being pulse compressed by sub-pulse matching filters respectively;

[0052] Figure 7 This is a diagram of echo data interference removal signal processing results provided by the present invention. DETAILED DESCRIPTION

[0053] In order to more clearly illustrate the technical means and anti-interference effect of the present invention, further description will be given below in conjunction with the accompanying drawings and specific implementation methods.

[0054] See also Figure 1 , Figure 1The present invention provides a method for designing an intra-pulse step LFM signal based on inter-pulse parameter agility and resisting intermittent sampling and forwarding interference. The present invention provides a method for designing an intra-pulse step LFM signal based on inter-pulse parameter agility and resisting intermittent sampling and forwarding interference, including:

[0055] Step 1: At the transmitting end, a method for generating an intra-pulse stepped LFM signal with agile inter-pulse parameters is to divide the pulse signal in each pulse repetition interval (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 between N PRIs in a coherent processing interval (Coherent Processing Interval, CPI);

[0056] According to the principle of intermittent sampling and forwarding 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 forwarded; after the forwarding is completed, the alternating sampling and forwarding process is repeated.

[0057] Specifically, let the pulse width of the intra-pulse step LFM signal with inter-pulse parameter agility be T, and the signal bandwidth of the mth PRI be B m , the sub-pulse frequency modulation slope is K, and its size is:

[0058] T=Mt sub (10)

[0059] Among them, t sub is the pulse width of the sub-pulse;

[0060] B m =B sub +(M-1)Δf (11)

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

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

[0063] Please refer to Figure 2 for the time-frequency relationship diagram of the intra-pulse step LFM signal with agile inter-pulse parameter changes and the schematic diagram of the inter-pulse agility of the intra-pulse step frequency Δf.

[0064] Then the intra-pulse step LFM signal with inter-pulse parameter agility can be written as:

[0065]

[0066] Among them, xn (t) is the intra-pulse step 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 transmitter, the frequency modulation slope, starting frequency and number of pulse segments M of the sub-pulse can be arbitrarily planned. The more the number of pulse segments M, the better the signal's anti-intermittent sampling and forwarding interference performance, but the corresponding signal processing process occupies more hardware resources.

[0068] Step 2: The receiving end receives the echo signal after the intermittent forwarding interference, and down-converts it into 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, and the down-converted echo signal is low-pass filtered to obtain a baseband signal for subsequent signal processing.

[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] Among them, 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 forwarding interference signal of the nth PRI, and n(t) is the noise signal;

[0073] X isrj_n (t) Take intermittent sampling and directly forward the interference signal as:

[0074]

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

[0076] Step 3, performing segmented pulse compression of sub-pulses on the echo signals of N PRIs within a CPI;

[0077] Specifically, a corresponding sub-pulse matched filter group is designed according to the transmission waveform, and segmented pulse compression is performed on the baseband echo signal after down-conversion.

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

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

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

[0081] Step 4: The sub-pulse pulse pressure result is detected by an adaptive threshold, and the sub-pulse of the interfered frequency band is found according to the pulse pressure result, and the interfered frequency band is filtered out;

[0082] Specifically, since the signal power of the intermittent forwarding sampling interference is much greater than the real echo signal, the peak power of the interference signal after pulse compression will be much greater than the real signal, so the interfered sub-pulse can be detected by the power threshold. The specific process is to take the mean of the variance of the pulse compression results of each sub-pulse as the adaptive threshold, perform signal threshold detection after sub-pulse pulse compression, and regard the sub-pulse that passes the threshold as the interfered sub-pulse, and the interfered frequency band needs to be removed by filtering.

[0083] The echo signal after interference removal is:

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

[0085] Among them, y(t) is the echo signal x after interference removal f (t) is the interference removal filter corresponding to the interference frequency band.

[0086] Step 5, re-performing pulse compression on the entire segment of the N PRI echo signals after eliminating interference;

[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 the problem of loss of distance resolution compared with the whole pulse compression signal of the original signal. Therefore, the present invention continues to perform whole pulse compression on the echo signal after interference removal, and the pulse compression result is:

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

[0089] Among them, x pc_n(t) is the output signal of the nth PRI interference-removing signal passing through the matched filter corresponding to the nth PRI echo signal, h n (t) is the matching function of the matched filter corresponding to the nth PRI echo signal.

[0090] Step 6: Perform inter-pulse coherent accumulation on the entire pulse pressure results of N PRIs.

[0091] Specifically, the entire pulse pressure of the intra-pulse stepped LFM signal has a grating lobe problem due to rectangular windowing. The transmitting signal used in the present invention has an agile frequency interval within the pulse, and the grating lobe of each PRI is non-coherent. Therefore, the present invention performs coherent accumulation between pulses on the entire pulse pressure results of N PRIs to obtain an interference-resistant signal processing result.

[0092] The invention provides an intra-pulse stepped LFM signal design based on inter-pulse parameter agility and an anti-intermittent sampling and forwarding interference processing method, which can be used to suppress intermittent sampling and forwarding interference.

[0093] The effect of the present invention is further described below in conjunction with simulation experiments, and the simulation parameters are shown in Table 1.

[0094] Table 1 Simulation parameters

[0095]

[0096] Figure 3(a)-Figure 3(b) It is the time domain real part image and frequency domain image of the intra-pulse step LFM signal with inter-pulse parameter agility. After observation, it can be seen that the intra-pulse step LFM signal with inter-pulse parameter agility designed by the simulation of the present invention is divided into 7 segments in the time domain, and each sub-pulse frequency band is separated in the frequency domain, with a certain frequency interval, and the sub-pulses are orthogonal, which is conducive to the mutual cover between the sub-pulses.

[0097] Figure 4(a)-Figure 4(b) The real part image and frequency domain image of the echo signal interfered by intermittent sampling forwarding are shown in Figure 2. After observation, it can be seen that the echo signal contains the target echo signal, forwarding interference signal and noise signal at the same time. The 2nd, 4th and 6th sub-pulses of the transmitted signal are interfered by forwarding, while the 1st, 3rd, 5th and 7th sub-pulses are not sampled by the jammer. The energy of the interfered sub-pulse frequency band is greater than that of the non-interfered frequency band.

[0098] Figure 5The figure is the direct pulse compression result of the interfered echo data. After observation, it can be seen that there are two target peaks 1.5km apart in the result of pulse compression. The pulse pressure peak at 1.5km is the real target, and the pulse pressure peak at 3km is the interference target. The power of the pulse pressure result of the interference signal is about 13dB greater than the real target, which will make it impossible to distinguish between the real signal and the interference signal, and then interfere with the signal processing result. At the same time, based on the characteristic that the power of the interference signal is much greater than that of the real target, the interfered sub-pulse frequency band can be detected through power threshold detection.

[0099] Figure 6(a)-Figure 6(g) The result diagram of pulse compression of echo data provided by the present invention through sub-pulse matching filters. After observation, it can be seen that since the 2nd, 4th, and 6th sub-pulses are interfered by intermittent sampling and forwarding, there are high-power interference targets and relatively small-power real targets in the segmented pulse compression results. At the same time, the 1st, 3rd, 5th, and 7th sub-pulses are not interfered, so there is only one real target. The interfered sub-pulses can be detected by adaptive thresholds to further complete interference elimination.

[0100] Figure 7 The figure is a signal processing result diagram of interference removal by a pulse-step LFM signal design based on inter-pulse parameter agility and an anti-intermittent sampling forwarding interference processing method proposed by the present invention. After observation, it can be seen that the target echo distance of the signal processing obtained by the pulse-step LFM signal design based on inter-pulse parameter agility and an anti-intermittent sampling forwarding interference processing method proposed by the present invention is 1.5km, which is consistent with the set value, and there is no interference target in the signal processing. It can be concluded that a pulse-step LFM signal design based on inter-pulse parameter agility and an anti-intermittent sampling forwarding interference processing method can effectively detect and suppress intermittent sampling forwarding interference signals.

[0101] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A pulse-step LFM signal design based on pulse-to-pulse parameter agility and an anti-intermittent sampling forwarding interference processing method, characterized in that: The steps include: Step 1: At the transmitting end, generate an intra-pulse step LFM signal with agile inter-pulse parameters; divide the pulse signal in each pulse repetition interval into M linear frequency modulation sub-pulse signals, the center frequency of each sub-pulse signal has a frequency interval Δf, and Δf is constant within the same PRI and is agile between N PRIs in a coherent processing time; Step 2: The receiving end receives the echo signal after the intermittent forwarding interference, and down-converts it into a baseband signal; Step 3, performing segmented pulse compression of sub-pulses on the echo signals of N PRIs within a CPI; Step 4: The sub-pulse pulse pressure result is detected by an adaptive threshold, and the sub-pulse of the interfered frequency band is found according to the pulse pressure result, and the interfered frequency band is filtered out; Step 5, re-performing pulse compression on the entire segment of the N PRI echo signals after eliminating interference; Step 6: Perform inter-pulse coherent accumulation on the entire pulse pressure results of N PRIs to obtain an anti-interference signal processing result.

2. The intra-pulse step LFM signal design based on inter-pulse parameter agility and anti-intermittent sampling forwarding interference processing method according to claim 1 is characterized in that: In step 1, the pulse width of the intra-pulse step LFM signal with inter-pulse parameter agility is: T=Mt sub (1) Among them, t sub is the pulse width of the sub-pulse; The signal bandwidth of the mth PRI of the intra-pulse step LFM signal with inter-pulse parameter agility is: B m =B sub +(M-1)Δf (2) Among them, B sub is the sub-pulse bandwidth; Δf is the frequency interval between sub-pulses; The sub-pulse frequency modulation slope of the intra-pulse step LFM signal with inter-pulse parameter agility is: K=B sub / t sub (3) 3. The intra-pulse step LFM signal design based on inter-pulse parameter agility and anti-intermittent sampling forwarding interference processing method according to claim 2 is characterized in that: The intra-pulse step LFM signal of the inter-pulse parameter agility is: Among them, x n (t) is the intra-pulse step LFM signal of the nth PRI; Δf n is the sub-pulse frequency interval of the nth PRI.

4. The intra-pulse step LFM signal design based on inter-pulse parameter agility and anti-intermittent sampling forwarding interference processing method according to claim 3 is characterized in that: The echo signal is: x r_isrj_n (t)=x r_n (t)+x isrj_n (t)+n(t) (5) Among them, 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 forwarding interference signal of the nth PRI, and n(t) is the noise signal; X isrj_n (t) Take intermittent sampling and directly forward the interference signal as: Where τ is the sampling pulse width, t s is the sampling repetition period, δ(t) represents the impulse function, x n (t) is the intra-pulse step LFM signal of the nth PRI.

5. The intra-pulse step LFM signal design based on inter-pulse parameter agility and anti-intermittent sampling forwarding interference processing method according to claim 1 is characterized in that: 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: x pc_n_m (t)=x r_n *h n_m (7) Among them, x pc_n_m (t) is the output signal of the nth PRI echo signal passing through the mth sub-matched filter of the nth matched filter group, h n_m (t) is the matching function of the m-th sub-pulse matched filter of the n-th PRI, and * represents the convolution calculation.

6. The intra-pulse step LFM signal design based on inter-pulse parameter agility and anti-intermittent sampling forwarding interference processing method according to claim 1 is characterized in that: The step 4 comprises: The mean of the variance of the pulse pressure results of each sub-pulse is taken as the adaptive threshold for threshold detection. The sub-pulse that exceeds the threshold is the interfered sub-pulse and needs to be removed by filtering. The echo signal after interference removal is: y(t)=x isrj_n (t)*x f (t) (8) Among them, y(t) is the echo signal x after interference removal f (t) is the interference removal filter corresponding to the interference frequency band.

7. The intra-pulse step LFM signal design based on inter-pulse parameter agility and anti-intermittent sampling forwarding interference processing method according to claim 1 is characterized in that: The step 5 includes: re-compressing the whole pulse of the N PRI echo signals after eliminating interference, and the pulse compression result is: x pc_n (t)=x r_n *h n (9) Among them, x pc_n (t) is the output signal of the nth PRI interference-removing signal passing through the matched filter corresponding to the nth PRI echo signal, h n (t) is the matching 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, the steps of the method according to any one of claims 1 to 7 are implemented.

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

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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