A method for suppressing background clutter in through-wall radar using MIMO antennas

Abstract

The present invention provides a background clutter suppression method for an FMCW through-wall radar with a MIMO antenna. The method reorders original echo data according to antenna numbers, performs principal component analysis according to a preset frame length to estimate background clutter, and updates the background clutter estimation result in real time through continuous iterative calculations. The contribution of the current frame to the background estimation result is strengthened to achieve maximum background clutter suppression, thereby improving the radar's target positioning and imaging effect. Combined with hardware design, the background estimation frame length can be selected to achieve a better background clutter suppression effect.

Description

Technical Field

[0001] The present invention belongs to the field of radar imaging technology, and in particular relates to a method for suppressing background clutter of a through-wall radar of a MIMO antenna. Background Art

[0002] Unlike radars used in free space, through-wall radars must penetrate thick walls to accurately detect and image human targets behind them. However, the echo intensity from walls and other indoor obstacles is often higher than that of the human target, making target positioning extremely difficult. Therefore, background clutter must be minimized before locating the target.

[0003] Currently common clutter suppression methods include frame difference method, cumulative average cancellation method and exponential weighted cancellation method. The frame difference method can often only observe targets with relatively large motion amplitudes. When the target displacement is small, it will cause the target to be lost and cannot be detected; the cumulative average cancellation method uses the same weight when accumulating multiple frames, which makes the current frame data contribute less to the entire background estimation; although the exponential weighted method introduces different weights to enhance the contribution of the current frame to background estimation, the algorithm performance is highly coupled with the target motion form. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a method for suppressing background clutter in a through-wall radar of a MIMO antenna, which can effectively suppress background clutter and thus improve the effect of radar on target positioning and imaging.

[0005] A method for suppressing background clutter of a FMCW through-wall radar with a MIMO antenna, comprising:

[0006] Step 1: After receiving the echo data from the FMCW through-wall radar, reorder the echo data according to the antenna number to obtain the echo matrix of each antenna Where L is the frame length and n is the number of antennas used;

[0007] Step 2: Echo matrix of each antenna Perform fast Fourier operation on each row to obtain a one-dimensional distance image matrix Where NFFT is the number of FFT points;

[0008] Distance image matrix Perform principal component analysis to obtain the principal component coefficient matrix C L×L and principal component score matrix S NFFT×L , select the first and second principal components, and obtain the single antenna echo reconstruction matrix through the following formula:

[0009]

[0010] Where T represents the matrix transpose operation;

[0011] The antenna background estimation array is obtained by averaging the reconstructed matrix column by column.

[0012] Step 3: Arrange the background estimation arrays of each antenna in order to obtain the background estimation matrix B n×NFFT :

[0013]

[0014] Step 4: Calculate the average of the background estimation matrix of the current frame and the background estimation matrix of the previous frame as the final background estimation result corresponding to the current frame; and use the final background estimation result as the background estimation matrix of the previous frame for the next background estimation.

[0015] Preferably, the frame length is determined according to hardware parameters of the FMCW through-wall radar.

[0016] Preferably, the frame length is determined according to a transmission speed of radar echo data.

[0017] The present invention has the following beneficial effects:

[0018] The present invention provides a background clutter suppression method for an FMCW through-wall radar with a MIMO antenna. The method estimates background clutter by reordering original echo data according to antenna numbers, performing principal component analysis according to a preset frame length, and updating the background clutter estimation result in real time through continuous iterative calculations. The method strengthens the contribution of the current frame to the background estimation result, thereby maximizing background clutter suppression and improving the radar's target positioning and imaging performance. Combined with hardware design, the background estimation frame length can be selected to achieve better background clutter suppression. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a flow chart of the background clutter suppression method of the FMCW through-wall radar of the present invention;

[0020] Figure 2 This is the block diagram of the FMCW through-wall radar system;

[0021] Figure 3 2 is a schematic diagram of a virtual receiving array of a MIMO antenna array according to an embodiment of the present invention;

[0022] Figure 4 Schematic diagram of an FMCW through-wall radar experimental scenario in an embodiment of the present invention;

[0023] Figure 5 1 is a schematic diagram of a one-dimensional range image of antenna No. 1 obtained in an embodiment of the present invention;

[0024] Figure 61 is a schematic diagram comparing the background estimation result of antenna No. 1 and the measured background result in an embodiment of the present invention;

[0025] Figure 7(a) and 7(b) 3 is a schematic diagram comparing the effects before and after background clutter suppression using the method of the present invention in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0027] A background clutter suppression method for FMCW through-wall radar with MIMO antennas, the processing flow is as follows Figure 1 As shown, the following steps are included:

[0028] Step 1: Process the raw echo data.

[0029] First, determine the system parameters and the frame length used for background estimation. After receiving the echo data, reorder the echo data according to the antenna number to obtain the echo matrix of each antenna. Where L is the frame length, that is, each frame includes sampling point data at multiple moments, usually 30; N is the number of echo snapshots at each moment, and n is the number of antennas used;

[0030] Step 2: Principal component analysis of single antenna echo

[0031] For each antenna echo matrix Perform a fast Fourier transform (FFT) operation on each row of to obtain a one-dimensional distance image matrix Where NFFT is the number of FFT points. Perform principal component analysis to obtain the principal component coefficient matrix C L×L and principal component score matrix S NFFT×L , select the first and second principal components, and obtain the single antenna echo reconstruction matrix through the following formula:

[0032]

[0033] Where T represents the matrix transpose operation.

[0034] The antenna background estimation array is obtained by averaging the reconstructed matrix column by column.

[0035] Step 3: Background clutter estimation

[0036] Arrange the background estimation arrays of each antenna in order to obtain the background estimation matrix B n×NFFT

[0037]

[0038] Step 4: Background clutter update

[0039] In order to update the estimated background clutter components in real time, the current frame length background estimation matrix is ​​recorded as The background estimation matrix of the previous frame length is recorded as The average of the two background estimation data is taken as the final background estimation result of the current frame length, and the estimation result is stored in As the new background estimation matrix of the previous frame length. Each time a new background estimation matrix of a frame length is obtained, the background estimation matrix of the frame length and the updated background estimation matrix of the previous frame length are compared. Take the mean and update Used as the next background estimate.

[0040] Optionally, the frame length used for estimating the background is determined according to the hardware parameters of the FMCW through-wall radar, wherein the frame length can be selected according to the radar echo data transmission speed.

[0041] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for suppressing background clutter in a FMCW through-wall radar with a MIMO antenna, characterized in that: include: Step 1: After receiving the echo data from the FMCW through-wall radar, reorder the echo data according to the antenna number to obtain the echo matrix of each antenna Where L is the frame length, N is the number of echo snapshots at each moment, and n is the number of antennas used; Step 2: Echo matrix of each antenna Perform fast Fourier operation on each row to obtain a one-dimensional distance image matrix Where NFFT is the number of FFT points; Distance image matrix Perform principal component analysis to obtain the principal component coefficient matrix C L×L and principal component score matrix S NFFT ×L , select the first and second principal components, and obtain the reconstruction matrix of a single antenna by the following formula: Where T represents the matrix transpose operation; The single antenna background estimation array is obtained by averaging the reconstructed matrix column by column Step 3: Arrange the background estimation arrays of each antenna in order to obtain the background estimation matrix B. n×NFFT : Step 4: Calculate the average of the background estimation matrix of the current frame and the background estimation matrix of the previous frame as the final background estimation result corresponding to the current frame.

2. The background clutter suppression method of the FMCW through-wall radar with a MIMO antenna according to claim 1, characterized in that: In step 4, the final background estimation result corresponding to the current frame is used as the background estimation matrix of the previous frame in the next background estimation.

3. The background clutter suppression method for a FMCW through-wall radar with a MIMO antenna according to claim 1, characterized in that: The frame length is determined according to the hardware parameters of the FMCW through-wall radar.

4. The method for suppressing background clutter of a FMCW through-wall radar with a MIMO antenna according to claim 3, wherein: The frame length is determined according to the radar echo data transmission speed.

5. The method for suppressing background clutter of a FMCW through-wall radar with a MIMO antenna according to claim 1, wherein: The frame length is 30.

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