MIMO array millimeter wave three-dimensional imaging method and device based on sub-band synthesis

Abstract

The invention relates to an MIMO array millimeter wave three-dimensional imaging method and device based on sub-band synthesis, and the method comprises the steps: transmitting and receiving a signal, so as to carry out the echo data processing of N paths of echo signals; sub-band synthesis echo data processing is carried out at least through the modes of slope removal, phase compensation, data time shifting and data superposition; and based on the measured back scattering data, three-dimensional image reconstruction is realized by obtaining a three-dimensional radar reflectivity graph. According to the embodiment of the invention, a simultaneous transmitting channel is added, so that the data acquisition efficiency is greatly improved.

Description

Technical Field

[0001] The present disclosure relates to the field of millimeter wave three-dimensional imaging, and in particular to a MIMO array millimeter wave three-dimensional imaging method and device based on sub-band synthesis. Background Art

[0002] In the prior art, the millimeter wave radar imaging system based on MIMO array still adopts the SIMO array transceiver mechanism, that is, the array transmitting antenna transmits signals one by one in time-sharing mode, which takes a long time to collect data and has low efficiency. In addition, it is not feasible to only increase the receiving channel due to the fixed scattering angle of the target point. Summary of the invention

[0003] The present disclosure intends to provide a MIMO array millimeter wave three-dimensional imaging method and device based on sub-band synthesis, which increases the simultaneous transmission channels and thus greatly improves the data acquisition efficiency.

[0004] According to one of the solutions of the present disclosure, a MIMO array millimeter wave three-dimensional imaging method based on sub-band synthesis is provided, comprising:

[0005] Signal transmission and reception to process echo data of N echo signals;

[0006] Performing sub-band synthetic echo data processing at least by means of deslope, phase compensation, data time shift, and data superposition;

[0007] Based on the measured backscatter data, three-dimensional image reconstruction is achieved by obtaining a three-dimensional radar reflectivity map.

[0008] In some embodiments, signal transmission and reception include:

[0009] Outputting periodic linear frequency modulation signals of N channels, the initial frequencies of the output sub-band signals of each channel are different and are distributed at equal intervals;

[0010] In one sub-cycle, the frequency band of the output signal of each channel remains unchanged, and in the next sub-cycle, the frequency bands of the output signals of all channels are rotated;

[0011] The transmit signal of each channel is processed by frequency doubling and divided into two signals. One signal is transmitted to the transmit antenna array, and the other signal is mixed with the receive signal of the receive antenna array.

[0012] The N received signals are mixed and processed to output N echo signals.

[0013] In some embodiments, the sub-band synthesized echo data processing is performed, including:

[0014] The received signals of different frequency bands received in N cycles are mixed with the transmitted signals in their respective cycles to obtain the backscattered data without slope.

[0015] The de-slanted backscatter data are multiplied by the phase compensation factor respectively to eliminate the residual video phase term interfering with the echo signal, thereby obtaining the phase-compensated backscatter data;

[0016] The phase-compensated backscattered data are time-shifted and data-superimposed to obtain sub-band synthetic echo data before three-dimensional imaging.

[0017] In some embodiments, the measured backscatter data is constructed based on the reflectivity of the point scatterer and the distance from the measurement point to the point scatterer.

[0018] In some embodiments, the three-dimensional image reconstruction is achieved by obtaining a three-dimensional radar reflectivity map, including:

[0019] The complete three-dimensional backscattering data s(x a ,y a ,k r ) Perform a two-dimensional Fourier transform from the azimuth and altitude directions to obtain S(k x ,k y ,k r );

[0020] S(k x ,k y ,k r ) is multiplied by the phase compensation factor to convert the phase of the backscattered data to the closest distance z=R between the target point and the antenna array along the radial axis. 0 The phase of F(k x ,k y ,k r );

[0021] Interpolate the phase-compensated data to make the frequency wave number variable k r Replace with k z , we get F(k x ,k y ,k z );

[0022] The wave number domain data of the target reflection coefficient are subjected to a three-dimensional inverse Fourier transform to obtain a three-dimensional radar reflectivity map f(x, y, z).

[0023] According to one of the solutions of the present disclosure, a MIMO array millimeter wave three-dimensional imaging device based on sub-band synthesis is provided, comprising: a digital controller, a frequency multiplier, a coupler, a mixer, and a transmitting antenna array and a receiving antenna array connected in sequence; wherein:

[0024] The digital controller outputs periodic linear frequency modulation signals of N channels and receives N echo signals;

[0025] The frequency multiplier performs frequency multiplication processing on the transmission signal of each channel after N sub-period rotation;

[0026] The coupler divides the frequency-multiplied signal into two signals, and transmits one signal to the transmitting antenna array;

[0027] The mixer performs mixing processing on one of the signals and the reception signal of the reception antenna array.

[0028] In some embodiments, a coordinate system is established based on the positions of the antenna array and the target in space, and the transmitting antenna and the receiving antenna are configured such that the equivalent sampling point is located at z=R 0 The xoy plane at a ,y a ,R 0 ), the point scatterer is located at (x,y,z).

[0029] In some embodiments, the sampling points are spaced Δx in the horizontal and vertical directions. a and Δy a The rectangular grid at each antenna position is synthesized with a frequency bandwidth of B, so that the backscatter data s(x a ,y a ,f) is a function of two spatial coordinates and operating frequency.

[0030] In some embodiments, the digital controller, frequency multiplier, coupler, and mixer are configured as follows:

[0031] The controller simultaneously outputs two linear frequency modulation signals with initial frequencies of 937.5MHz and 1062.5MHz respectively. After 32 times of frequency multiplication by the frequency multiplier, the coupler outputs a sub-band signal with a frequency band of 30GHz-36GHz and a sub-band signal with a frequency band of 34GHz-40GHz, which are respectively sent out simultaneously by two transmitting channels and transmitted in rotation after a cycle. In each receiving channel, a broadband signal with a frequency band of 30GHz-40GHz is synthesized through sub-band synthesis technology; the mixer mixes one of the sub-band signals with the receiving signal of the receiving antenna array.

[0032] In some embodiments, each pair of transmit antenna and receive antenna is located approximately at the same position of the antenna plane.

[0033] The various embodiments of the present disclosure are based on the MIMO array millimeter wave three-dimensional imaging method and device based on sub-band synthesis, at least through signal transmission and reception, to perform echo data processing on N echo signals; at least through the method of removing slope, phase compensation, data time shift, and data superposition, to perform sub-band synthesis echo data processing; based on the measured backscattering data, by obtaining a three-dimensional radar reflectivity map to achieve three-dimensional image reconstruction, so as to decompose the broadband signal into N sub-band signals through the sub-band synthesis technology, independently process each sub-band, and then synthesize the N sub-band signals into the original broadband signal. This process can realize simultaneous multi-channel signal transmission and multi-channel signal reception, and perform imaging processing on the echo data through the RMA algorithm. Compared with the previous TD-MIMO imaging method, the present disclosure adds simultaneous transmission channels, thereby greatly improving the data acquisition efficiency.

[0034] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure, as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In the drawings, which are not necessarily drawn to scale, similar reference numerals in different views may represent similar components. Similar reference numerals with letter suffixes or similar reference numerals with different letter suffixes may represent different instances of similar components. The drawings generally illustrate various embodiments by way of example and not limitation, and together with the description and claims, serve to explain the disclosed embodiments.

[0036] Figure 1 A flow chart of a MIMO array millimeter wave three-dimensional imaging method based on sub-band synthesis according to an embodiment of the present disclosure is shown;

[0037] Figure 2 The transmission timing relationship of each channel in each time period of an embodiment of the present disclosure is shown;

[0038] Figure 3 A schematic diagram showing the positions of an antenna array and a target object in space according to an embodiment of the present disclosure is shown;

[0039] Figure 4 The figure shows the point target three-dimensional image reconstruction result according to an embodiment of the present disclosure;

[0040] Figure 5 A two-dimensional cross-sectional view of a reconstructed image in various directions according to an embodiment of the present disclosure is shown;

[0041] Figure 6 A schematic structural diagram of a MIMO array millimeter wave three-dimensional imaging device based on sub-band synthesis according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0043] Security inspection is a key means to ensure public safety and is widely used in various public places. Traditional security inspection equipment such as metal detectors and X-ray security inspection machines play an important role in the security inspection process, but they also have certain limitations. Metal detectors can detect metal objects carried by the human body, such as knives and guns, but cannot detect non-metallic dangerous goods; X-ray security inspection machines can detect various dangerous goods well through X-ray imaging technology, but because X-rays are ionizing, they are not suitable for human security inspection imaging. Millimeter wave security inspection equipment stands out among many new security inspection equipment with its clothing penetration ability, high-resolution imaging and non-ionizing radiation.

[0044] Millimeter wave imaging systems are mainly divided into two imaging geometric models: plane and cylindrical. Both models require the synthesis of two-dimensional apertures in the height direction and distance direction to achieve three-dimensional imaging. From the perspective of array configuration and imaging mechanism in these two dimensions, there are three imaging methods. The first is two-dimensional single-transmitter single-receiver (2D-SISO), which is to evenly distribute transceivers in the two-dimensional aperture, or use a two-dimensional mechanical scanning method. However, the large number of antennas required by the former method makes the cost too high, and the latter method takes too much time. The second two-dimensional multiple-transmitter multiple-receiver (2D-MIMO) imaging method is that the transmitter and receiver are distributed in the two-dimensional aperture respectively. The MIMO array can receive target signals at multiple angles to synthesize virtual apertures, thereby greatly reducing the number of antennas and reducing costs. In addition, the MIMO array has high efficiency and can achieve "snapshot" imaging. The third one-dimensional multiple-transmitter multiple-receiver one-dimensional scanning (1D-MIMO-1D-Scanning) imaging method can be said to be a compromise between the first two methods. Compared with 2D-MIMO, it requires fewer antenna units and has faster imaging efficiency than 2D-SISO.

[0045] However, MIMO technology essentially uses SIMO antennas to scan point by point to realize MIMO synthetic aperture radar, so the data acquisition efficiency of such a time-division multiple-input multiple-output (TD-MIMO) array transceiver mechanism is not high. And limited by the fixed scattering angle of the target point, if you want to continue to improve the data acquisition efficiency, you can't just increase the receiving channel.

[0046] In combination with the above-mentioned background technology, the present disclosure records the corresponding solutions in the form of embodiments to solve the defects in the prior art, but it is not intended to limit the scope of protection of the patent right claimed by the present disclosure.

[0047] As one of the solutions, Figure 1 A schematic diagram of an implementation flow of a MIMO array millimeter wave three-dimensional imaging method based on sub-band synthesis according to an embodiment of the present disclosure is shown. The embodiment of the present disclosure provides a MIMO array millimeter wave three-dimensional imaging method based on sub-band synthesis, including:

[0048] Signal transmission and reception to process echo data of N echo signals;

[0049] Performing sub-band synthetic echo data processing at least by means of deslope, phase compensation, data time shift, and data superposition;

[0050] Based on the measured backscatter data, three-dimensional image reconstruction is achieved by obtaining a three-dimensional radar reflectivity map.

[0051] In view of the above content, the embodiments of the present disclosure are intended to propose a MIMO array millimeter wave three-dimensional imaging method based on sub-band synthesis. The broadband signal is decomposed into N sub-band signals through sub-band synthesis technology, each sub-band is processed independently, and then the N sub-band signals are synthesized into the original broadband signal. This process can realize simultaneous multi-channel signal transmission and multi-channel signal reception. Compared with the previous TD-MIMO imaging method, the present invention increases the simultaneous transmission channel, thereby greatly improving the data acquisition efficiency. Finally, the echo data is imaged and processed by the RMA algorithm.

[0052] The steps of the embodiment of the present disclosure are exemplary, and the following takes steps S1 to S3 as an example to further illustrate the MIMO array millimeter wave three-dimensional imaging method based on sub-band synthesis of the present disclosure. It can be implemented by a MIMO array millimeter wave three-dimensional imaging device based on sub-band synthesis, and the device includes a digital controller, a frequency multiplier, a coupler, a mixer, and an antenna array connected in sequence.

[0053] In some specific embodiments, the present disclosure may include signal transmission and reception, including:

[0054] Outputting periodic linear frequency modulation signals of N channels, the initial frequencies of the output sub-band signals of each channel are different and are distributed at equal intervals;

[0055] In one sub-cycle, the frequency band of the output signal of each channel remains unchanged, and in the next sub-cycle, the frequency bands of the output signals of all channels are rotated;

[0056] The transmit signal of each channel is processed by frequency doubling and divided into two signals. One signal is transmitted to the transmit antenna array, and the other signal is mixed with the receive signal of the receive antenna array.

[0057] The N received signals are mixed and processed to output N echo signals.

[0058] Step S1: Signal transmission and reception.

[0059] Step S11: The digital controller outputs periodic linear frequency modulation signals of N channels. The initial frequencies of the sub-band signals output by each channel are different and are distributed at equal intervals. The sub-band signals of different frequency bands emitted by each channel in each sub-period are expressed as follows:

[0060]

[0061] Among them, s Tk (n) represents the nth subband signal transmitted by the kth channel, K r is the signal modulation frequency, f n is the initial frequency of each sub-band signal, satisfying f n =f+(n-1)B n , f is the initial frequency of the full bandwidth signal, B n is the bandwidth of each channel sub-band signal.

[0062] Step S12: In one sub-period, the frequency band of the output signal of each channel remains unchanged. In the next sub-period, the frequency bands of the output signals of all channels are rotated. After N sub-periods, each channel traverses all the sub-band signals of N frequency bands. The rotation method is shown in the matrix in formula (2):

[0063]

[0064] Among them, the number of rows of the matrix represents N transmission channels, and the number of columns of the matrix represents N sub-periods; f 1 ,f 2 ,f 3 …f N Indicates N initial frequency points that are equally spaced. The timing relationship between the transmission and reception of each channel is as follows: Figure 2 The transmission timing relationship of each channel in each time period of an embodiment of the present disclosure is shown.

[0065] Step S13: The transmission signal of each channel is multiplied by the frequency multiplier, and then divided into two signals in each channel by the coupler, one of which is transmitted to the transmitting antenna array, and the other is transmitted to the mixer for mixing with the receiving signal of the receiving antenna array. The expression of the sub-band signal of different frequency bands received by each channel in each sub-period is:

[0066]

[0067] Where τ = 2R / c represents the time it takes for the transmitted signal to return to the receiving array element after reaching the target point, R is the distance from the antenna array element to the target point, and c is the propagation speed of the electromagnetic wave. After N sub-periods, each transmitting channel transmits sub-band signals of N frequency bands, and the expression is as follows:

[0068] s Tk =[s Tk (1),s Tk (2),…,s Tk (n),…,s Tk (N)] (4)

[0069] Each receiving channel receives sub-band signals of N frequency bands, and the expression is as follows:

[0070] s Rk =[s Rk (1),s Rk (2),…,s Rk (n),…,s Rk (N)] (5)

[0071] Finally, after N cycles, the N received signals are processed by the mixer to output N echo signals which are transmitted back to the digital controller to prepare for echo data processing.

[0072] In some specific embodiments, the present disclosure may be to perform sub-band synthetic echo data processing, including:

[0073] The received signals of different frequency bands received in N cycles are mixed with the transmitted signals in their respective cycles to obtain the backscattered data without slope.

[0074] The de-slanted backscatter data are multiplied by the phase compensation factor respectively to eliminate the residual video phase term interfering with the echo signal, thereby obtaining the phase-compensated backscatter data;

[0075] The phase-compensated backscattered data are time-shifted and data-superimposed to obtain sub-band synthetic echo data before three-dimensional imaging.

[0076] The embodiment of the present disclosure may further include step S2 based on the above step S1.

[0077] Step S2: Sub-band synthesis.

[0078] Step S21: Remove the slope, and mix the received signals of different frequency bands received in N cycles with the transmitted signals in their respective cycles:

[0079]

[0080] Get the deslope backscatter data:

[0081] s dechirp k =[s dechirp k (1),s dechirp k (2),…,s dechirp k (n),…,s dechirp k (N)] (7)

[0082] Step S22: Phase compensation, the backscattered data after de-skewing are respectively compared with the phase compensation factor s c =-jπK r τ 2 Multiply to eliminate the residual video phase term of the interfering echo signal

[0083] s ek (n) = s dechirp k (n)·s c =exp[-j2π(K r τt+f n τ)] (8)

[0084] Get phase-compensated backscatter data:

[0085] s ek =[s ek (1),s ek (2),…,s ek (n),…,s ek (N)] (9)

[0086] Step S23: Time-shift the compensated data by Δt n =(n-1)B n / K r :

[0087] s k (n) = exp[-j2π(K r τ(t-Δt n )+f n τ)] (10)

[0088] Get the time-shifted backscattering data:

[0089] s k =[s k (1),s k (2),…,s k (n)…,s k (N)] (11)

[0090] Step S24: superimpose the data obtained in step S13 to obtain superimposed data:

[0091] s=exp[-j2π(K r τt+fτ)] (12)

[0092] The above completes the sub-band synthetic echo data processing part before three-dimensional imaging.

[0093] In some specific embodiments, the present disclosure may be that the measured backscatter data is constructed based on the reflectivity of the point scatterers and the distance from the measurement point to the point scatterers.

[0094] In some specific embodiments, the present disclosure may be to achieve three-dimensional image reconstruction by obtaining a three-dimensional radar reflectivity map, including:

[0095] The complete three-dimensional backscattering data s(x a ,y a ,k r ) Perform a two-dimensional Fourier transform from the azimuth and altitude directions to obtain S(k x ,k y ,k r );

[0096] S(k x ,k y ,k r ) is multiplied by the phase compensation factor to convert the phase of the backscattered data to the closest distance z=R between the target point and the antenna array along the radial axis. 0 The phase of F(k x ,k y ,k r );

[0097] Interpolate the phase-compensated data to make the frequency wave number variable k r Replace with k z , we get F(k x ,k y ,k z );

[0098] The wave number domain data of the target reflection coefficient are subjected to a three-dimensional inverse Fourier transform to obtain a three-dimensional radar reflectivity map f(x, y, z).

[0099] The embodiment of the present disclosure may further include step S3 based on the above step S2.

[0100] Step S3: 3D imaging processing.

[0101] The positions of the antenna array and the target in space are as follows: Figure 3The schematic diagram of the position of the antenna array and the target object in space in one embodiment of the present disclosure is shown, and the equivalent sampling points of the transmitting antenna and the receiving antenna are located at z=R 0 The xoy plane at a ,y a ,R 0 ), the point scatterer is located at (x,y,z), and its reflectivity is f(x,y,z). The sampling points are spaced Δx in the horizontal and vertical directions. a and Δy a The synthetic frequency bandwidth at each antenna position is B. Therefore, the acquired backscatter data s(x a ,y a ,f) is a function of two spatial coordinates and the operating frequency. The frequency variable is related to the frequency wave number k r =2π(f+K r Therefore, the measured data can also be expressed as s(x a ,y a ,k r ). Then the measured backscatter data is:

[0102] s(x a ,y a ,k r )=f(x,y,z)exp(-j2k r R) (13)

[0103] Where R is the distance from the measurement point to the point scatterer, expressed as:

[0104]

[0105] The three-dimensional radar reflectivity map of the distributed target can be expressed as

[0106]

[0107] According to the stationary phase principle, the exponential spherical wave can be decomposed into the superposition of plane wave components:

[0108]

[0109] where k x ,k y ,k r are the components of the spatial wave number in the three coordinate directions respectively. Substituting formula (16) into formula (15), the three-dimensional radar reflectivity map is:

[0110]

[0111] Formula (17) can be simplified as:

[0112]

[0113] Among them, FFT 2D [·]and Respectively represent two-dimensional FFT and three-dimensional IFFT, The wave number domain (k x ,k y ,k r ) is converted to the spatial domain (x, y, z), where Represents the spherical coordinates, indicating k z The sampling of the axes is uneven, and the FFT process is a linear superposition, so interpolation is required to obtain the linear k z axis, the final three-dimensional radar reflectivity map is:

[0114]

[0115] From formula (19), we can know that for the backscattering data s(x a ,y a ,k r ) to obtain the reflection coefficient f(x, y, z) of the target object, thereby realizing 3D image reconstruction. The steps of 3D imaging processing in the MIMO array millimeter wave 3D imaging method based on sub-band synthesis are as follows:

[0116] Step S31: Transverse two-dimensional Fourier transform of the backscattered data, and convert the complete three-dimensional backscattered data s(x a ,y a ,k r ) Perform a two-dimensional Fourier transform from the azimuth and altitude directions to obtain S(k x ,k y ,k r ), the expression is:

[0117] S(k x ,k y ,k r )=FFT 2D [s(x a ,y a ,k r )] (20)

[0118] Step S32: Phase compensation, S(k x ,k y ,k r ) is multiplied by the phase compensation factor to convert the phase of the backscattered data to the closest distance z=R between the target point and the antenna array along the radial axis. 0 The phase of F(k x ,k y ,kr ), the expression is:

[0119] F(k x ,k y ,k r )=S(k x ,k y ,k r )exp(-jk r R 0 ) (twenty one)

[0120] Step S33: interpolation processing. The wavenumber domain backscattering data obtained in the above steps is uniformly distributed in the lateral wavenumber domain, but non-uniformly distributed in the radial wavenumber domain. In order to obtain the radial spatial domain data through FFT later, it is necessary to interpolate the phase-compensated data so that the frequency wavenumber variable k r Replace with k z , we get F(k x ,k y ,k z ), the expression is:

[0121] F(k x ,k y ,k z )=Stolt[F(k x ,k y ,k r )] (twenty two)

[0122] Step S34: three-dimensional inverse Fourier transform, after interpolation processing, the wave number domain data of the target reflection coefficient is subjected to three-dimensional inverse Fourier transform, and finally the three-dimensional radar reflectivity map f(x, y, z) is output, and the expression is:

[0123]

[0124] For example, assume that the digital controller of the device of the present invention simultaneously outputs two linear frequency modulation signals with initial frequencies of 937.5MHz and 1062.5MHz respectively, and after 32 times of frequency multiplication by the frequency multiplier, the output sub-band 1 signal with a frequency band of 30GHz-36GHz and the sub-band 2 signal with a frequency band of 34GHz-40GHz are respectively sent out by two transmitting channels at the same time, and then transmitted in rotation after a cycle. Finally, in each receiving channel, a broadband signal with a frequency band of 30GHz-40GHz is synthesized by sub-band synthesis technology.

[0125] like Figure 3As shown in the figure, 4096 sets of devices are placed in front and behind the target to form two antenna arrays. Each antenna array includes 4096 transmitting antennas and 4096 receiving antennas. The spacing between the transmitting and receiving antennas is 0.0025m, and the aperture size is 0.1575×0.1575m. The positions of each pair of transmitting and receiving antennas are very close and can be approximated to be the same position on the antenna plane. The imaging result of the final point target is shown in the figure below. Figure 4 The 3D image reconstruction result of a point target according to an embodiment of the present disclosure is shown in FIG. Figure 5 Two-dimensional cross-sectional views of reconstructed images in various directions according to an embodiment of the present disclosure are shown.

[0126] As one of the solutions, Figure 6 A schematic diagram of the structure of a MIMO array millimeter wave three-dimensional imaging device based on sub-band synthesis according to an embodiment of the present disclosure is shown. The embodiment of the present disclosure provides a MIMO array millimeter wave three-dimensional imaging device based on sub-band synthesis, including:

[0127] A digital controller, a frequency multiplier, a coupler, a mixer, a transmitting antenna array and a receiving antenna array connected in sequence; wherein:

[0128] The digital controller outputs periodic linear frequency modulation signals of N channels and receives N echo signals;

[0129] The frequency multiplier performs frequency multiplication processing on the transmission signal of each channel after N sub-period rotation;

[0130] The coupler divides the frequency-multiplied signal into two signals, and transmits one signal to the transmitting antenna array;

[0131] The mixer performs mixing processing on one of the signals and the reception signal of the reception antenna array.

[0132] In some specific embodiments, the device of the present disclosure may be, wherein a coordinate system is established based on the positions of the antenna array and the target object in space, and the transmitting antenna and the receiving antenna are configured such that an equivalent sampling point is located at z=R 0 The xoy plane at a ,y a ,R 0 ), the point scatterer is located at (x,y,z).

[0133] In some specific embodiments, the device of the present disclosure may be, wherein the sampling points are spaced apart by Δx in the horizontal and vertical directions. a and Δy a The rectangular grid at each antenna position is synthesized with a frequency bandwidth of B, so that the backscatter data s(x a ,y a,f) is a function of two spatial coordinates and operating frequency.

[0134] In some specific embodiments, the device of the present disclosure may be, wherein the digital controller, the frequency multiplier, the coupler, and the mixer are configured as follows:

[0135] The controller simultaneously outputs two linear frequency modulation signals with initial frequencies of 937.5MHz and 1062.5MHz respectively. After 32 times of frequency multiplication by the frequency multiplier, the coupler outputs a sub-band signal with a frequency band of 30GHz-36GHz and a sub-band signal with a frequency band of 34GHz-40GHz, which are respectively sent out simultaneously by two transmitting channels and transmitted in rotation after a cycle. In each receiving channel, a broadband signal with a frequency band of 30GHz-40GHz is synthesized through sub-band synthesis technology; the mixer mixes one of the sub-band signals with the receiving signal of the receiving antenna array.

[0136] In some specific embodiments, the apparatus of the present disclosure may be wherein each pair of transmitting antenna and receiving antenna is located approximately at the same position of the antenna plane.

[0137] In some specific embodiments, the apparatus of the present disclosure may be configured to implement the methods described in steps S1 to S3 above.

[0138] Specifically, one of the inventive concepts of the present disclosure is the MIMO array millimeter wave three-dimensional imaging method and device based on sub-band synthesis of various embodiments of the present disclosure, at least through signal transmission and reception, to perform echo data processing on N echo signals; at least through the method of removing slope, phase compensation, data time shift, and data superposition, sub-band synthesis echo data processing is performed; based on the measured backscattering data, a three-dimensional radar reflectivity map is obtained to achieve three-dimensional image reconstruction, so that the broadband signal is decomposed into N sub-band signals through sub-band synthesis technology, each sub-band is processed independently, and then the N sub-band signals are synthesized into the original broadband signal. This process can realize simultaneous multi-channel signal transmission and multi-channel signal reception, and the echo data is imaged by the RMA algorithm. Compared with the previous TD-MIMO imaging method, the present disclosure adds a simultaneous transmission channel, thereby greatly improving the data acquisition efficiency. The present disclosure uses a new MIMO millimeter wave three-dimensional imaging mechanism of simultaneous multi-sub-band transmission and reception to realize simultaneous multi-channel signal transmission and multi-channel signal reception, so that the data acquisition efficiency is further improved.

[0139] The present disclosure also provides a computer-readable storage medium having computer executable instructions stored thereon. When the computer executable instructions are executed by a processor, the computer executable instructions mainly implement the above-mentioned MIMO array millimeter wave three-dimensional imaging method based on sub-band synthesis, which at least includes:

[0140] Signal transmission and reception to process echo data of N echo signals;

[0141] Performing sub-band synthetic echo data processing at least by means of deslope, phase compensation, data time shift, and data superposition;

[0142] Based on the measured backscatter data, three-dimensional image reconstruction is achieved by obtaining a three-dimensional radar reflectivity map.

[0143] The above embodiments are only exemplary embodiments of the present disclosure and are not intended to limit the present disclosure. The protection scope of the present disclosure is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present disclosure within the essence and protection scope of the present disclosure, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present disclosure.

Claims

1. A MIMO array millimeter wave three-dimensional imaging method based on sub-band synthesis, comprising: Signal transmission and reception to process echo data of N echo signals; Performing sub-band synthetic echo data processing at least by means of deslope, phase compensation, data time shift, and data superposition; Based on the measured backscatter data, three-dimensional image reconstruction is achieved by obtaining a three-dimensional radar reflectivity map.

2. The method according to claim 1, wherein: Signal transmission and reception, including: Outputting periodic linear frequency modulation signals of N channels, the initial frequencies of the output sub-band signals of each channel are different and are distributed at equal intervals; In one sub-cycle, the frequency band of the output signal of each channel remains unchanged, and in the next sub-cycle, the frequency bands of the output signals of all channels are rotated; The transmit signal of each channel is processed by frequency doubling and divided into two signals. One signal is transmitted to the transmit antenna array, and the other signal is mixed with the receive signal of the receive antenna array. The N received signals are mixed and processed to output N echo signals.

3. The method according to claim 2, wherein: Perform sub-band synthetic echo data processing, including: The received signals of different frequency bands received in N cycles are mixed with the transmitted signals in their respective cycles to obtain the backscattered data without slope. The de-slanted backscatter data are multiplied by the phase compensation factor respectively to eliminate the residual video phase term interfering with the echo signal, thereby obtaining the phase-compensated backscatter data; The phase-compensated backscattered data are time-shifted and data-superimposed to obtain sub-band synthetic echo data before three-dimensional imaging.

4. The method according to claim 3, wherein: The measured backscatter data is constructed based on the reflectivity of the point scatterers and the distance from the measurement point to the point scatterers.

5. The method according to claim 4, wherein: The three-dimensional image reconstruction is achieved by obtaining the three-dimensional radar reflectivity map, including: The complete three-dimensional backscattering data s(x a ,y a ,k r ) Perform a two-dimensional Fourier transform from the azimuth and altitude directions to obtain S(k x ,k y ,k r ); S(k x ,k y ,k r ) is multiplied by the phase compensation factor to convert the phase of the backscattered data to the phase of the closest distance z = R0 between the target point and the antenna array along the radial axis, and the result is F(k x ,k y ,k r ); Interpolate the phase-compensated data to make the frequency wave number variable k r Replace with k z , we get F(k x ,k y ,k z ); The wave number domain data of the target reflection coefficient are subjected to a three-dimensional inverse Fourier transform to obtain a three-dimensional radar reflectivity map f(x, y, z).

6. A MIMO array millimeter wave three-dimensional imaging device based on sub-band synthesis, comprising a digital controller, a frequency multiplier, a coupler, a mixer, and a transmitting antenna array and a receiving antenna array connected in sequence; wherein: The digital controller outputs periodic linear frequency modulation signals of N channels and receives N echo signals; The frequency multiplier performs frequency multiplication processing on the transmission signal of each channel after N sub-period rotation; The coupler divides the frequency-multiplied signal into two signals, and transmits one signal to the transmitting antenna array; The mixer performs mixing processing on one of the signals and the reception signal of the reception antenna array.

7. The device according to claim 6, wherein: The coordinate system is established based on the position of the antenna array and the target in space. The transmitting antenna and the receiving antenna are configured as an equivalent sampling point located in the xoy plane at z = R0. The coordinates are marked as (x a ,y a ,R0), the point scatterer is located at (x,y,z).

8. The device according to claim 7, wherein: The sampling points are spaced Δx in the horizontal and vertical directions. a and Δy a The rectangular grid at each antenna position is synthesized with a frequency bandwidth of B, so that the backscatter data s(x a ,y a ,f) is a function of two spatial coordinates and operating frequency.

9. The device according to claim 8, wherein: The digital controller, frequency multiplier, coupler and mixer are configured as follows: The controller simultaneously outputs two linear frequency modulation signals with initial frequencies of 937.5MHz and 1062.5MHz respectively. After 32 times of frequency multiplication by the frequency multiplier, the coupler outputs a sub-band signal with a frequency band of 30GHz-36GHz and a sub-band signal with a frequency band of 34GHz-40GHz, which are respectively sent out simultaneously by two transmitting channels and transmitted in rotation after a cycle. In each receiving channel, a broadband signal with a frequency band of 30GHz-40GHz is synthesized through sub-band synthesis technology; the mixer mixes one of the sub-band signals with the receiving signal of the receiving antenna array.

10. The device according to claim 9, wherein: Each pair of transmitting antenna and receiving antenna is located at approximately the same position on the antenna plane.

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