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CN-116755044-B - Method for canceling frequency domain sliding expansion of external radiation source radar

CN116755044BCN 116755044 BCN116755044 BCN 116755044BCN-116755044-B

Abstract

The invention discloses a method for canceling frequency domain sliding expansion of an external radiation source radar, and belongs to the field of digital signal processing. The method comprises the steps of carrying out overlapped segmentation on a monitoring signal and a reference signal, carrying out fast Fourier transformation, utilizing the strong correlation between the reference signal and multipath clutter on the same frequency point to inhibit static clutter on frequency points in a bandwidth, converting a frequency domain signal subjected to static clutter inhibition to a time domain, removing an overlapped part to obtain a complete time domain signal subjected to clutter inhibition, carrying out distance-Doppler two-dimensional matched filtering, detecting moving clutter interference, and carrying out step-by-step inhibition on moving clutter of different Doppler frequency shifts, so that the order of a filter is always first, the operation amount of an algorithm is obviously reduced, and the memory occupation amount is reduced. The invention utilizes the principle of the radar signal of the external radiation source, can effectively inhibit the interference of braking and static noise waves, is easier to realize the real-time processing of the signal, is not limited to the radiation source signal with a specific structure, and has universality.

Inventors

  • SHAN TAO
  • SUN QUANDE
  • HE SICONG

Assignees

  • 北京理工大学

Dates

Publication Date
20260508
Application Date
20230506

Claims (8)

  1. 1. The method for canceling the frequency domain sliding expansion of the external radiation source radar is characterized by comprising the following steps of, Step one, carrying out quadrature demodulation and digital down-conversion processing on a monitoring signal and a reference signal to obtain a time domain monitoring signal And a time domain reference signal ; Step two, the monitoring signal obtained in the step one is subjected to Reference signal Performing overlapping segmentation treatment; step three, the segmented monitoring signals obtained in the step two are subjected to Performing fast Fourier transform FFT on the segmented reference signal obtained in the step two Performing FFT; step four, utilizing the frequency domain monitoring signal and the frequency domain reference signal obtained in the step three to inhibit clutter on frequency points one by one in the bandwidth, and setting zero for coefficients of noise frequency points to obtain a frequency domain signal after clutter inhibition; Fifthly, performing Inverse Fast Fourier Transform (IFFT) on the frequency domain signal after static clutter suppression obtained in the fourth step, and removing the overlapping part to obtain a complete time domain signal after static clutter suppression; step six, utilizing the time domain monitoring signal obtained in the step five And the time domain reference signal obtained in the step one Performing distance-Doppler two-dimensional matched filtering to obtain a matched filtering result; Step seven, detecting whether the dynamic clutter interference exists or not by using the matched filtering result obtained in the step six, ending cancellation if the dynamic clutter interference does not exist, storing dynamic clutter Doppler information if the dynamic clutter interference exists, and executing the steps eight, nine and ten; Step eight, utilizing the static clutter subspace matrix obtained in the step four and the dynamic clutter Doppler information obtained in the step seven, and utilizing the strong correlation of the clutter with the same Doppler frequency shift on the same frequency point to establish a dynamic clutter subspace corresponding to the Doppler frequency shift; step nine, utilizing the frequency domain signal after static clutter suppression obtained in the step four And step eight, obtaining a dynamic clutter subspace Wherein , For one-by-one moving clutter subspace Clutter cancellation processing is carried out, so that the order of the filter is always the first order; And step ten, performing IFFT by using the frequency domain signals after the dynamic clutter suppression obtained in the step nine, and removing the overlapped part to obtain complete time domain signals after the dynamic clutter suppression, thereby realizing effective suppression of the dynamic clutter and the static clutter.
  2. 2. The method of claim 1, wherein in the first step, the time domain reference signal is expressed as (1) In the formula, The direct wave has much higher intensity than noise, so the influence of the noise is ignored; the time domain monitoring signal is expressed as (2) In the formula, Is the amount of static clutter; And Respectively the first Amplitude and time delay of the static clutter; is the number of moving clutter; 、 、 Respectively the first Amplitude, delay, doppler frequency of the individual moving clutter; Is the target number; 、 、 Respectively the first Amplitude, delay, doppler frequency of the individual targets; is the sampling rate; To monitor channel noise.
  3. 3. The method for canceling frequency domain sliding expansion of an external source radar according to claim 2, wherein in step two, The first segment after segmentation The segment signal is expressed as: (3) in the formula, , For the step length of each segment, For the length of each segment, where , For a target maximum time delay of the time delay, When (when) In the time-course of which the first and second contact surfaces, 1, Otherwise 0.
  4. 4. The method for canceling the frequency domain sliding expansion of the external radiation source radar according to claim 3, wherein the third implementation method comprises the following steps, Step 3.1 for the segmented reference signals FFT is carried out to obtain corresponding frequency domain reference signals The expression of which is shown below, (4) In the formula, , Is the first The direct wave of the segment is transmitted, Is the first The data after the segment direct wave FFT, , Representing the frequency domain Sampling points, the interval between the frequency domain sampling points is ; Step 3.2 for the segmented monitoring signals FFT is carried out to obtain corresponding frequency domain monitoring signals The expression of which is shown below, (5) In the formula, , Is the first Monitoring noise of the signal in a segment frequency domain; For the first The FFT of the static clutter is represented as follows, (6) For the first The FFT of the individual dynamic clutter is represented as follows, (7) In the frequency domain, the interval between sampling points Doppler frequencies greater than the target or clutter, i.e Therefore, the formula (7) is expressed as follows, (8) In the same way, to the first The FFT of the individual target echoes is represented as follows, (9) Substituting formulas (6), (8) and (9) into (5), (10)。
  5. 5. The method for canceling frequency domain sliding expansion of an external radiation source radar of claim 4 wherein said step four is implemented by, Step 4.1, extracting effective frequency points in the frequency domain signals; The frequency points within the signal bandwidth are called effective frequency points, the frequency points outside the signal bandwidth are called noise frequency points, the number of the effective frequency points of the signal is set as The index set corresponding to the effective frequency point is: (11) Reference signal at the first The expression of the frequency points is: (12) in the formula, , Is the first of the direct wave An expression of the frequency points; Monitoring signal at the first The expression of the frequency points is: (13) in the formula, , , And then the preparation method is carried out, And (3) with And Has very little correlation, if Then And (3) with Hardly correlated and noise And (3) with 、 And None of which are related; Step 4.2 will be The reference signal and the monitoring signal at each frequency point are divided into A block, wherein Each block has the length of And based on this, each block of reference signals and monitoring signals is taken back and forth The points are used as sliding windows; First, the The monitoring signals of the block are: (14) First, the The reference signals for the block are: (15) ; Step 4.3, constructing a static clutter subspace matrix; (16) step 4.4, filtering each monitoring signal respectively Block monitoring signal Projected to and from Orthogonal subspaces, resulting in a canceled signal ; (17) In the formula, , Is that Is a conjugate transpose of (2); Step 4.5, after clutter on the effective frequency points are eliminated, the coefficient of the noise frequency points is set to zero, and a frequency domain signal after static clutter suppression is obtained ; (18)。
  6. 6. The method for canceling the frequency domain sliding expansion of an external radiation source radar according to claim 5, wherein the fifth implementation method comprises the steps of, Step 5.1, performing IFFT on the frequency domain signal after static clutter suppression; the frequency domain signal after static clutter suppression is: (19) For the first The segment signal is used to determine the segment, Namely the first in the formula (19) The row vectors are subjected to IFFT, and the expression is as follows: (20) Step 5.2, removing the overlapped part and obtaining a complete time domain signal after static clutter suppression; (21)。
  7. 7. The method of claim 6, wherein in step six, the moving clutter subspace is: (22) in the formula, Is the first The frequency points of the frequency spectrum are selected, , As the doppler frequency of the moving clutter, , For different numbers of doppler frequencies.
  8. 8. The method for canceling frequency domain sliding expansion of an external source radar of claim 7 wherein step nine is performed by, Step 9.1 order By combining frequency domain signals Projected to and from Orthogonal subspaces, resulting in a canceled signal ; (23) In the formula, ; Step 9.2 if Then If not, the first part of the first part is connected with the second part, By combining frequency domain signals Projected to and from Orthogonal subspaces, obtaining new canceled signals ; (24) Step 9.3 if The procedure returns to step 9.2, otherwise, 。

Description

Method for canceling frequency domain sliding expansion of external radiation source radar Technical Field The invention relates to a method for canceling frequency domain sliding expansion of an external radiation source radar, belonging to the field of digital signal processing. Background External source radar is a radar system that utilizes non-cooperative illumination sources (e.g., digital television broadcast signals) for target detection and tracking. Because of the advantages of wide coverage, good concealment, low cost, environmental protection, no pollution and the like, the method has attracted extensive attention of researchers in the past decades. The monitoring channel signal received by the external radiation source radar not only contains target echoes, but also strong direct waves and multipath clutter. The target echo signal in the monitoring channel signal is often 60-100dB lower than the clutter signal, which causes the target echo to be submerged in the echo spectrum. Clutter suppression is therefore the most important problem faced by external source radars. At present, the external radiation source radar clutter suppression method is mainly divided into a space domain clutter suppression method and a time domain clutter suppression method. The airspace clutter suppression has a good suppression effect on the sidelobe clutter by a method of suppressing the sidelobe and forming the null, but has no suppression capability on the clutter in the main lobe. The common time domain methods include Venus algorithm, recursive least square algorithm, normalized least mean square algorithm, expansion cancellation algorithm, batch expansion cancellation algorithm and sliding expansion cancellation algorithm. These methods are often faced with computationally intensive problems, especially for high sample rate signals, which are difficult to apply in real-time signal processing. Aiming at the problems, clark uses fast Fourier transform in a block least mean square algorithm, and a frequency domain block self-adaptive filter is provided, so that the algorithm operation speed is greatly improved. Zhuo proposes a clutter suppression method based on a subband wiener filter, which reduces the dimension of the wiener filter in the subband, thereby reducing the computational complexity. In recent years, researchers have proposed carrier domain cancellation methods based on the waveform characteristics of orthogonal frequency division multiplexing signals. These methods have the advantages of small calculation amount and small occupied memory. However, the carrier domain algorithm relies on demodulation and modulation of the orthogonal frequency division multiplexed signal, and has some limitations. Disclosure of Invention The invention mainly aims to provide a method for canceling the sliding expansion of an external radiation source radar frequency domain, which utilizes the principle of the external radiation source radar and the digital signal processing technology to realize the effective suppression of dynamic and static clutter based on a sliding expansion cancellation algorithm. The invention has the advantages of less operation, small occupied memory, good universality and the like. The aim of the invention is achieved by the following technical scheme. The invention discloses an external radiation source radar frequency domain sliding expansion cancellation method, which comprises the steps of carrying out overlapped segmentation on a monitoring signal and a reference signal, carrying out fast Fourier transformation, utilizing the strong correlation between the reference signal on the same frequency point and multipath clutter, inhibiting static clutter on frequency points in a bandwidth, converting a frequency domain signal after static clutter inhibition into a time domain, removing an overlapped part to obtain a complete time domain signal after clutter inhibition, carrying out distance-Doppler two-dimensional matched filtering, detecting moving clutter interference, and carrying out step-by-step inhibition on moving clutter with different Doppler frequency shifts. The invention can effectively inhibit the interference of braking and static noise waves, has the advantages of less operation amount and small occupied memory, is easier to realize the real-time processing of signals, is not limited to radiation source signals with specific structures, and has universality. The invention discloses a method for canceling frequency domain sliding expansion of an external radiation source radar, which comprises the following steps: And step one, carrying out quadrature demodulation and digital down-conversion processing on the monitoring signal and the reference signal to obtain a time domain monitoring signal s (n) and a time domain reference signal r (n). The time domain reference signal is expressed as r(n)=d(n) (1) Wherein d (n) is a direct wave. Since the intensity of the direct wave is much hig