Fast imaging method based on MIMO array equivalent phase center data reconstruction

Abstract

The invention discloses a rapid imaging method based on MIMO array equivalent phase center data reconstruction. The method comprises the following steps: receiving a broadband signal, and carrying out target scattering to obtain an original scattering echo signal; performing spatial domain division on an imaging space according to a criterion of high-precision reconstruction from multi-station data to single-station data in a spatial domain; completing reconstruction from multi-station data to single-station data according to a high-precision reconstruction criterion; performing spatial domain division according to a reconstruction criterion, and completing high-precision reconstruction from multi-station data to single-station data in each subspace; converting the reconstructed scattering echo signal into spatial frequency domains corresponding to an array direction and a synthetic aperture direction in each spatial domain, and determining an original spatial spectrum; interpolating the original spatial spectrum in a wavenumber domain according to a spatial frequency domain coordinate relation to determine a final spatial spectrum; determining a target imaging function of each sub-airspace according to the final spatial spectrum; and cutting and splicing the target imaging function of each sub-airspace according to the divided airspace to obtain a final target imaging function.

Description

Technical Field

[0001] The invention relates to an intelligent comprehensive recognition technology, in particular to a fast imaging method based on MIMO array equivalent phase center data reconstruction. Background Art

[0002] The most common method for radar three-dimensional real-time imaging devices is to use a two-dimensional array to achieve rapid focusing in azimuth and a broadband signal to achieve focusing in distance. However, in application scenarios with relatively high frequency bands, such as the millimeter wave terahertz band, the two-dimensional array has a large number of array elements, which, under existing conditions, adds a lot of costs to the system, especially the relatively high cost of the current millimeter wave terahertz device itself. Although only a single array element is used for point-by-point two-dimensional scanning, a three-dimensional focused image can also be obtained in combination with a broadband signal, but the data acquisition time is too long to achieve real-time imaging. Combining MIMO arrays with synthetic aperture technology can reduce the number of array elements and reduce system costs. However, the imaging algorithms based on MIMO arrays and synthetic aperture technology, such as the BP algorithm and the MIMO-RMA algorithm, generally have low imaging efficiency to ensure imaging quality and accuracy. The BP algorithm cannot meet the real-time requirements because it needs to perform phase compensation in each dimension before superposition. The MIMO-RMA algorithm is considered to be an imaging algorithm with relatively high computational efficiency. However, before transforming the azimuth dimension to the spatial frequency dimension, it needs to perform zero padding operations on the receiving and transmitting dimensions respectively, which will significantly increase the number of interpolation operations, thereby affecting the computational efficiency. Summary of the invention

[0003] In view of the problems existing in the prior art, the present invention provides a fast imaging method based on MIMO array equivalent phase center data reconstruction, which can achieve real-time imaging and high calculation rate.

[0004] The purpose of the present invention is achieved through the following technical solutions.

[0005] A fast imaging method based on MIMO array equivalent phase center data reconstruction, comprising the following steps:

[0006] A criterion for high-precision reconstruction of multi-station data into single-station data in the spatial domain is defined;

[0007] The received broadband signal is scattered by the target to obtain the original scattered echo signal;

[0008] According to the criterion of high-precision reconstruction of multi-station data into single-station data in the spatial domain, the imaging space is spatially divided;

[0009] In the divided subspace, the reconstruction of multi-station data into single-station data is completed according to the high-precision reconstruction criterion;

[0010] The spatial domain is divided according to the reconstruction criteria, and high-precision reconstruction of multi-station data into single-station data in each subspace is completed;

[0011] The reconstructed scattered echo signal is transformed into the spatial frequency domain corresponding to the array direction and the synthetic aperture direction in each spatial domain to determine the original spatial spectrum;

[0012] The original spatial spectrum is interpolated in the wave number domain according to the spatial frequency domain coordinate relationship to determine the final spatial spectrum;

[0013] Determine the target imaging function of each sub-spatial domain according to the final spatial spectrum;

[0014] According to the divided airspace, the target imaging function of each sub-airspace is trimmed and spliced ​​to obtain the final target imaging function.

[0015] The original scattered echo signal is:

[0016] ;

[0017] The transmit antennas of the MIMO array are located The receiving antenna is located at Department, is the wave number corresponding to the different transmission frequencies of the broadband signal, the distance direction of the plane where the MIMO array synthetic aperture is located is located at z; the coordinate position of the center point of the imaging space is defined as , the position is located at the geometric center of the imaging space.

[0018] The criteria for high-precision reconstruction of multi-station data into single-station data in the defined spatial domain are as follows:

[0019] ;

[0020] in is the equivalent center of the transmitting and receiving antennas,

[0021]

[0022] are the distances between the transmitting and receiving antennas and the center point of the imaging space;

[0023]

[0024] is the distance between the equivalent center of the transmitting and receiving antennas and the center point of the imaging space;

[0025] The prerequisites for high-precision reconstruction of multi-station data into single-station data are as follows:

[0026]

[0027] in, ,

[0028] ,

[0029] , respectively representing the distance between the transmitting and receiving antennas After subspace division and reconstruction of multi-station data into single-station data, the reconstructed subspace data is further processed by imaging algorithms, including transforming the reconstructed scattered echo signal to the spatial frequency domain corresponding to the array direction and the synthetic aperture direction in each spatial domain to determine the original spatial spectrum; interpolating the original spatial spectrum in the wavenumber domain according to the spatial frequency domain coordinate relationship to determine the final spatial spectrum; and determining the target imaging function of each sub-spatial domain based on the final spatial spectrum:

[0030] .

[0031] According to the divided airspace, the target imaging function of each sub-airspace is trimmed and spliced ​​to obtain the final target imaging function.

[0032] Compared with the prior art, the advantages of the present invention are:

[0033] 1. Compared with the classic BP algorithm that can be used for any array form, the imaging speed has been improved.

[0034] 2. Compared with the MIMO-RMA algorithm that requires zero-padding operations, which significantly increases the number of interpolation operations and thus affects the computational efficiency, the imaging efficiency is significantly improved. Moreover, since the phase error is controlled within a reasonable range during the reconstruction of multi-station data into single-station data, the imaging efficiency is improved without reducing the imaging quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the steps of a fast imaging method based on MIMO array equivalent phase center data reconstruction according to an embodiment of the present invention.

[0036] Figure 2 It is a structural schematic diagram of a fast imaging method and device based on MIMO array equivalent phase center data reconstruction according to an embodiment of the present invention.

[0037] Figure 3 Schematic diagram of a MIMO linear array example. DETAILED DESCRIPTION

[0038] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0039] Figure 1 FIG. 4 is a schematic diagram of the steps of a fast imaging method based on MIMO array equivalent phase center data reconstruction according to an embodiment of the present invention. Figure 1As shown, the method comprises the following steps:

[0040] S1: The original scattered echo signal obtained after the received broadband signal is scattered by the target.

[0041] The broadband signal is transmitted by the transmitting array element of the MIMO array, and the receiving array element of the MIMO array receives the original scattered echo signal.

[0042] In the embodiment of the present invention, the MIMO array selects a linear array in the form of a transmitter at both ends of a receiver array. It can be understood that other forms of MIMO arrays may also be selected in other embodiments. Figure 2 Schematic diagram of a MIMO linear array synthetic aperture simulation scenario according to an embodiment of the present invention. Figure 3 FIG. 1 is a schematic diagram of an example of a MIMO linear array according to an embodiment of the present invention. Figure 2 and Figure 3 As shown, in this MIMO linear array, the receiving array elements are spaced at a distance d. R Arranged, at both ends of the first and last receiving array elements, there are transmitting array elements with a spacing of d T arrangement.

[0043] The original scattered echo signal is:

[0044] ;

[0045] The transmit antennas of the MIMO array are located The receiving antenna is located at Department, is the wave number corresponding to the different transmission frequencies of the broadband signal, the distance direction of the plane where the MIMO array synthetic aperture is located is located at z; the coordinate position of the center point of the imaging space is defined as , the position is located at the geometric center of the imaging space.

[0046] S2, dividing the imaging space into spatial domains according to the criterion of high-precision reconstruction of multi-station data into single-station data in the spatial domain;

[0047] The subspace partitioning must meet the following conditions:

[0048]

[0049] in, ,

[0050] ,

[0051] , respectively representing the distance between the transmitting and receiving antennas distance to the target;

[0052]

[0053]

[0054] are the distances between the transmitting and receiving antennas and the center point of the imaging space.

[0055]

[0056] is the distance from the equivalent center of the transmitting and receiving antennas to the center point of the imaging space.

[0057] S3. In the divided subspace, the reconstruction of multi-station data into single-station data is completed according to the high-precision reconstruction criteria:

[0058]

[0059] in is the equivalent center of the transmitting and receiving antennas,

[0060]

[0061]

[0062] are the distances between the transmitting and receiving antennas and the center point of the imaging space.

[0063]

[0064] is the distance from the equivalent center of the transmitting and receiving antennas to the center point of the imaging space.

[0065] S4, transforming the reconstructed scattered echo signal into the spatial frequency domain corresponding to the array direction and the synthetic aperture direction in each spatial domain, and determining the original spatial spectrum;

[0066] S5, interpolating the original spatial spectrum in the wavenumber domain according to the spatial frequency domain coordinate relationship to determine the final spatial spectrum;

[0067] S6, determining a target imaging function of each sub-spatial domain according to the final spatial spectrum;

[0068] The calculation formulas for S4 to S6 are as follows:

[0069]

[0070] According to the divided airspace, the target imaging function of each sub-airspace is trimmed and spliced ​​to obtain the final target imaging function.

[0071] It can be seen that the fast imaging method based on MIMO array equivalent phase center data reconstruction of the present invention avoids the numerous zero-filling operations in spatial dimensions by defining a high-precision reconstruction criterion for multi-station data to single-station data, further reduces the interpolation calculation, and thus shortens the imaging time; since the phase error is controlled within a reasonable range during the reconstruction of multi-station data to single-station data, it can be ensured that the imaging quality is not reduced.

[0072] In summary, the fast imaging method and device based on MIMO array equivalent phase center data reconstruction of the present invention has improved imaging speed compared with the classic BP algorithm that can be used for any array form; compared with the MIMO-RMA algorithm that requires zero-padding operations, which causes a significant increase in the number of interpolation operations and thus affects the calculation efficiency, the imaging efficiency is significantly improved, and because the phase error is controlled within a reasonable range during the reconstruction of multi-station data into single-station data, the imaging efficiency is improved without reducing the imaging quality.

Claims

1. A fast imaging method based on MIMO array equivalent phase center data reconstruction, characterized by the steps of include: A criterion for high-precision reconstruction of multi-station data into single-station data in the spatial domain is defined; The received broadband signal is scattered by the target to obtain the original scattered echo signal; According to the criterion of high-precision reconstruction of multi-station data into single-station data in the spatial domain, the imaging space is spatially divided; In the divided subspace, the reconstruction of multi-station data into single-station data is completed according to the high-precision reconstruction criterion; The spatial domain is divided according to the reconstruction criteria, and high-precision reconstruction of multi-station data into single-station data in each subspace is completed; The reconstructed scattered echo signal is transformed into the spatial frequency domain corresponding to the array direction and the synthetic aperture direction in each spatial domain to determine the original spatial spectrum; The original spatial spectrum is interpolated in the wave number domain according to the spatial frequency domain coordinate relationship to determine the final spatial spectrum; Determine the target imaging function of each sub-spatial domain according to the final spatial spectrum; According to the divided airspace, the target imaging function of each sub-airspace is trimmed and spliced ​​to obtain the final target imaging function.

2. A fast imaging method based on MIMO array equivalent phase center data reconstruction according to claim 1, characterized in that The original scattered echo signal is: ； The transmit antennas of the MIMO array are located The receiving antenna is located at Department, is the wave number corresponding to the different transmission frequencies of the broadband signal, the distance direction of the plane where the MIMO array synthetic aperture is located is located at z; the coordinate position of the center point of the imaging space is defined as , the position is located at the geometric center of the imaging space.

3. The fast imaging method based on MIMO array equivalent phase center data reconstruction according to claim 1, characterized in that The criteria for high-precision reconstruction of multi-station data into single-station data in the defined spatial domain are as follows: ； in is the equivalent center of the transmitting and receiving antennas, ; ； are the distances between the transmitting and receiving antennas and the center point of the imaging space; ； is the distance between the equivalent center of the transmitting and receiving antennas and the center point of the imaging space; The prerequisites for high-precision reconstruction of multi-station data into single-station data are as follows: ； in, , ， , respectively representing the distance between the transmitting and receiving antennas The distance to the target.

4. A fast imaging method based on MIMO array equivalent phase center data reconstruction according to claim 3, characterized in that After subspace division and reconstruction of multi-station data into single-station data, the reconstructed subspace data is further processed by imaging algorithms, including transforming the reconstructed scattered echo signal to the spatial frequency domain corresponding to the array direction and the synthetic aperture direction in each spatial domain to determine the original spatial spectrum; interpolating the original spatial spectrum in the wavenumber domain according to the spatial frequency domain coordinate relationship to determine the final spatial spectrum; and determining the target imaging function of each sub-spatial domain according to the final spatial spectrum: 。 5. A fast imaging method based on MIMO array equivalent phase center data reconstruction according to claim 4, characterized in that According to the divided airspace, the target imaging function of each sub-airspace is trimmed and spliced ​​to obtain the final target imaging function.

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