A Radar Co-frequency Asynchronous Interference Suppression Method Based on Slow Time Dimension Interpolation

Abstract

The present invention provides a radar co-frequency asynchronous interference suppression method based on slow-time interpolation, the method comprising: extracting sample data sets X of the same range gate Nr received by the radar in the slow-time dimension. Nr_i The sample data group X Nr_i The process involves filtering to identify pulse period sequence group K containing interference signals. j And the pulse period sequence number group K that does not contain interference signals s The interference signal is restored; slow-time dimension sample interpolation is performed to obtain the processed signal X'. Nr_Kj Improve the performance of the radar.

Description

Technical Field

[0001] This invention belongs to the technical field of radar signal processing, and particularly relates to a method for suppressing radar co-frequency asynchronous interference based on slow time-dimensional interpolation. Background Technology

[0002] During normal radar operation, the filter cannot filter out interference from asynchronous signals from the opposing radar at the same frequency, resulting in the echo signal containing multiple high-amplitude pulse interference signals. The interference signals will cover part of the echo signal and have a significant impact on the target detection results, thus reducing the performance of the radar.

[0003] In view of this, the present invention is hereby proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a radar co-frequency asynchronous interference suppression method based on slow time-dimensional interpolation, solving the technical problem of reduced radar utilization efficiency in existing methods. The technical solution of this invention has many beneficial effects, as described below:

[0005] A radar co-frequency asynchronous interference suppression method based on slow time-dimensional interpolation is provided, the method comprising:

[0006] Extract sample data sets X of the same range gate Nr received by radar in the slow time dimension. Nr_i ;

[0007] The sample data group X Nr_i The process involves filtering to identify pulse period sequence group K containing interference signals. j And the pulse period sequence number group K that does not contain interference signals s ;

[0008] The interference signal is restored;

[0009] Slow-time dimension sample interpolation processing yields the processed signal.

[0010] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0011] Based on the characteristic that the relative distance, azimuth and elevation angles, and relative velocity of the target in the airborne radar coherent signal change little within a certain pulse period, and that the signal has a high correlation in the slow time dimension, the same-frequency asynchronous interference signal is eliminated by judging the magnitude of the sample signal amplitude. The slow time dimension signal is then interpolated to recover the echo signal covered by the same-frequency asynchronous interference signal as much as possible, thereby reducing the interference of the same-frequency asynchronous signal on the echo signal and improving the target detection success rate. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 Slow-time dimension time-domain plot of the echo signal affected by asynchronous interference at the same frequency;

[0014] Figure 2 Frequency domain diagram of the echo signal affected by asynchronous interference at the same frequency;

[0015] Figure 3 Spectrum diagram of echo signal subjected to asynchronous interference at the same frequency;

[0016] Figure 4 Slow-time dimension time-domain plot of the distance gate 23 of the processed echo signal;

[0017] Figure 5 Frequency domain diagram of the processed echo signal from distance gate 23;

[0018] Figure 6 Spectrum diagram of the processed echo signal.

[0019] Figure 7 This is a flowchart of the method of the present invention. Detailed Implementation

[0020] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] The radar co-frequency asynchronous interference suppression method based on slow time-dimensional interpolation of this invention is described in [reference needed]. Figure 7 As shown, the method includes:

[0022] S101: Extract sample data X of the same range gate Nr received by the radar in the slow time dimension. Nr_i Specifically:

[0023] The total signal received by the radar includes: the radar echo signal dimension S. i and radar receive synchronous asynchronous interference signal S j Wherein: radar echo signal S i The expression is:

[0024]

[0025] Where A is the radar signal amplitude, i is the radar pulse number, and f c For carrier frequency, t PRI For the radar pulse period, t PW Where is the radar pulse width, t is the signal reception time, N is the total number of radar pulse cycles, and V is the relative velocity between the radar and the jamming radar.

[0026] Radar receives synchronous and asynchronous interference signal S j The expression is:

[0027]

[0028] Among them, A j For the amplitude of the interference signal, i j f is the sequence number of the interference signal pulse. c For carrier frequency, t PRI_j For the period of the interference signal pulse, t PW_j M represents the pulse width of the interference signal, and M represents the total number of interference pulse cycles.

[0029] When t PRI_j ≠t PRI And A j When the value is >A, the interference signal repeatedly appears within each pulse period, covering part of the radar echo signal and lowering the CFAR threshold of the radar detection area. For example... Figure 1 The figure shows the time-domain amplitude of the echo at the same range gate (slow time dimension) for different pulse periods, with sample data X for the same range gate Nr in each pulse period. Nr_i Represented as:

[0030] X Nr_i =S i (t Nr +(i-1)t PRI )+S j (t Nr +(i-1)t PRI ), 1≤i≤N, 1≤Nr≤Nr max (3)

[0031] Among them, t Nr Nr represents the time delay corresponding to the distance gate. max This represents the total number of distance gates within one pulse cycle.

[0032] S102: Sample Data Set X Nr_i The process involves filtering to identify pulse period sequence group K containing interference signals. j And the pulse period sequence number group K that does not contain interference signals s Under the coherent system of airborne radar, the target's range and relative velocity change relatively smoothly within a certain pulse period, and the slow-time dimension signals have high correlation. Therefore, interpolation processing can be performed on the slow-time dimension signals to recover the covered echo signals as much as possible. Specifically:

[0033] The samples were filtered to identify pulse period sequence group K containing interference signals. j And the pulse period sequence number group K that does not contain interference signals s , where k is the screening coefficient. Identify and mark each data point in each group as an interference signal, satisfying:

[0034]

[0035] Where k is the screening coefficient K Nr_s For the echo signal in sample data X Nr_i The position of K Nr_j For interference signals in sample data X Nr_i The position in the middle.

[0036] S103: The interference signal is restored, specifically:

[0037] The method for restoring interference signals also requires determining whether the data set is worth restoring. For example, if a data set contains 100 values, and only one does not contain interference signals, then the remaining 99 values ​​are not worth restoring and cannot be restored.

[0038] when At that time, the echo sample Interpolation yields the sequence number K. j Processed sample signal Otherwise, no action will be taken. (Interference signals are not processed), k Spline The interpolation threshold coefficient is used to reconstruct the echo signal from the interference signal in this group. When the condition is not met... When the condition is met, it indicates that the group cannot be restored;

[0039] All signals after processing are:

[0040]

[0041] The purpose is: if i = Ks, it means that the signal is an echo signal, that is, the original data, which does not need to be processed; if i = Kj, it means that the signal is an interference signal, which needs to be processed.

[0042] S104: Slow-time dimension sample interpolation processing to obtain the processed signal. Specifically:

[0043] The processed signal is obtained by interpolating the slow-time dimension samples according to equation (5).

[0044] Repeat steps one, two, and three in sequence to obtain the total processed data sample X'. Nr_i Processed signal The expression is:

[0045] ;

[0046] The processed signal is closer to the radar echo signal than the received signal. If the radar echo signal S i and processed signal The variance is less than that of the radar echo signal S i Sum-frequency asynchronous interference signal S j The variance of XS is denoted as D(XS). <D[S-(S+S j If the interference is suppressed, it shows that the method of the present invention is effective.

[0047] The method of this invention utilizes the characteristics that the spatial position of the target changes little within a certain pulse period and the slow-time dimension echo signal has a high correlation. It performs interpolation processing on the slow-time dimension signal to remove as many co-frequency asynchronous interference signals as possible and restore the covered echo signal, thereby reducing the interference of co-frequency asynchronous signals on the reference sample, optimizing the CFAR detection threshold of the radar detection area, and improving the target detection success rate.

[0048] Example

[0049] The high-repetition echo signal has a pulse width of 2µs, a PRI period of 10µs, a pulse count of 1024, a sampling rate of 4MHz, and a frequency of 10GHz. Ground clutter echo signals are present at range gate 23 and frequency gate 135, with a signal strength of 70.84dB; target echo signals are present at range gate 23 and frequency gate 328, with a signal strength of 69.31dB; the entire spectrum is distributed with co-frequency asynchronous interference signals with a signal strength of approximately 80dB, of which the co-frequency asynchronous interference signal strength at range gate 23 and frequency gate 628 is 81.71dB. The slow-time dimension time-domain distribution and frequency domain distribution of the received signal at range gate 23 are respectively... Figure 1 , Figure 2 As shown; the entire received signal spectrum distribution is composed of Figure 3 As shown.

[0050] After processing by the method of the present invention, the processed signal has a time-domain distribution and a frequency-domain distribution in the slow-time dimension of the distance gate 23, respectively, which are determined by... Figure 4 and Figure 5 As shown, the entire received signal spectrum distribution is composed of Figure 6 As shown.

[0051] Combination Figure 1 (Echo signal distance gate 23, time domain data before processing) Figure 4 The comparison shows that the interference signal is basically eliminated in the slow time dimension time domain, combined with Figure 2 (Echo signal distance gate 23, frequency domain data before processing) Figure 3 (Comparison of frequency domain and time domain spectrograms of the echo signal before processing) Figure 5 (Processing of asynchronous signals at the same frequency: before processing, 81.94; after processing, the signal is represented by y (signal strength) and x (frequency gate position). Y = 51.94) Figure 6 (By maximizing the reduction of the entire interference signal while maximizing the preservation of the echo signal) the following phenomenon can be obtained:

[0052] 1. In the frequency domain diagram, it can be seen that the ground clutter signal strength at distance gate 23 and frequency gate 135 is 70.79dB, which is not much different from the ground clutter strength of the unprocessed signal;

[0053] 2. The target echo signal strength at range gate 23 and frequency gate 328 is 68.47 dB, which is not much different from the target echo signal strength of the unprocessed signal.

[0054] 3. The intensity of the synchronous and asynchronous interference signal of distance gate 23 and frequency gate 626 is 51.94dB. The intensity of the synchronous and asynchronous interference signal is significantly reduced compared with the signal before processing, and basically does not exceed 55dB.

[0055] The results show that the co-frequency asynchronous interference signal is effectively suppressed, while the characteristics of the ground clutter signal are preserved, and it does not affect the normal target signal, proving that the method is effective.

[0056] The product provided by this invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to the invention without departing from the principles of the invention, and these improvements and modifications also fall within the protection scope of the invention claims.

Claims

1. A radar co-frequency asynchronous interference suppression method based on slow time-dimensional interpolation, characterized in that, The methods include: extracting a sample data set X of the same range gate Nr in the slow time dimension received by the radar Nr_i ; The sample data set X Nr_i A screening is performed to screen out a pulse period number set K containing an interference signal j And a pulse period number set K not containing an interference signal s ; The interference signal is restored; Slow-time dimension sample interpolation processing yields the processed signal.

2. The radar co-frequency asynchronous interference suppression method according to claim 1, characterized in that, extracting a sample data set X of the same range gate Nr in the slow time dimension received by the radar Nr_i comprising: The total signal received by the radar comprises: the echo signal S i and the co-frequency asynchronous interference signal S j wherein: the echo signal S i is expressed as: where A is the radar signal amplitude, i is the radar pulse number, f c is the carrier frequency, t PRI is the radar pulse period, t PW is the radar pulse width, t is the received signal time, N is the total number of radar pulse periods, and V is the relative velocity of the radar and the jamming radar. Radar receives synchronous and asynchronous interference signal S j The expression is: Among them, A j For the amplitude of the interference signal, i j f is the sequence number of the interference signal pulse. c For carrier frequency, t PRI_j For the period of the interference signal pulse, t PW_j M represents the pulse width of the interference signal, and M represents the total number of interference pulse cycles. When t PRI_j ≠t PRI And A j When >A, the interference signal repeatedly appears within each pulse period, covering the radar echo signal of the covered portion. The sample data X of the same range gate Nr in each pulse period... Nr_i Represented as: X Nr_i =S i (t Nr +(i-1)t PRI )+S j (t Nr +(i-1)t PRI ),1≤i≤N,1≤Nr≤Nr max (3) Among them, t Nr Nr is the time delay corresponding to the distance gate. max This represents the total number of distance gates within one pulse cycle.

3. The radar co-frequency asynchronous interference suppression method according to claim 2, characterized in that, The sample data group X Nr_i The process involves filtering to identify pulse period sequence group K containing interference signals. j And the pulse period sequence number group K that does not contain interference signals s ,include: Identify and mark each data point in each group as an interference signal, satisfying the following conditions: Where K is the screening coefficient, K Nr_s For the echo signal in sample data K Nr_i The position of K Nr_j For interference signals in sample data K Nr_i The position in the middle.

4. The radar co-frequency asynchronous interference suppression method according to claim 3, characterized in that, The interference signal is restored, including: when At that time, the echo sample Interpolation is performed to obtain the sequence number K. j Processed sample signal Otherwise, no action will be taken. Where, k Spline This is the interpolation threshold coefficient.

5. The radar co-frequency asynchronous interference suppression method according to claim 4, characterized in that, Slow-time dimension sample interpolation processing yields the processed signal. include: Processed signal The expression is: If the radar echo signal S i and processed signal The variance is less than that of the radar echo signal S i Sum-frequency asynchronous interference signal S j The variance of the interference can be suppressed.

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