CN113126084A - Multiple-sending multiple-receiving antenna array arrangement for active millimeter wave security inspection imaging, human body security inspection equipment and method - Google Patents
Multiple-sending multiple-receiving antenna array arrangement for active millimeter wave security inspection imaging, human body security inspection equipment and method Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/887—Radar or analogous systems specially adapted for specific applications for detection of concealed objects, e.g. contraband or weapons
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/03—Details of HF subsystems specially adapted therefor, e.g. common to transmitter and receiver
- G01S7/032—Constructional details for solid-state radar subsystems
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V8/00—Prospecting or detecting by optical means
- G01V8/005—Prospecting or detecting by optical means operating with millimetre waves, e.g. measuring the black losey radiation
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Abstract
The embodiment of the disclosure discloses a sparse multi-transmitting multi-receiving array arrangement for active millimeter wave security inspection imaging, which comprises a plurality of transmitting antennas and a plurality of receiving antennas; the plurality of transmitting antennas and the plurality of receiving antennas are arranged in two groups of antennas arranged in a first direction; the two groups of antennas are divided into a plurality of chips arranged along a first direction, each chip includes N1 transmitting antennas arranged in a first row along the first direction and N2 receiving antennas arranged in a second row along the first direction, and N1 transmitting antennas and N2 receiving antennas are spaced apart along a second direction perpendicular to the first direction, wherein N1 and N2 are positive integers greater than or equal to 2, and N1 < N2. In each of the two groups of antennas, combinations of N1 transmit antennas and combinations of N2 receive antennas are alternately arranged in the first direction such that in each group of antennas, N1 transmit antennas are located between the combinations of two N2 receive antennas.
Description
Technical Field
The disclosed embodiments relate to the field of human body security inspection, and in particular, to a multiple-transmit multiple-receive antenna array arrangement for millimeter wave security inspection imaging, a human body security inspection apparatus including the multiple-transmit multiple-receive antenna array arrangement, and a human body security inspection method performed using the apparatus.
Background
At present, the following two modes are mainly used for imaging and security inspection of public human bodies at home and abroad.
The first human body imaging security inspection technology is based on a Passive millimeter wave terahertz human body imaging technology (L.Yujiri., "Passive millimeter wave imaging", IEEE MII-S int.Microw.Sym.dig, pp.98-101,2006). The method has the greatest advantages that the millimeter wave terahertz wave radiation of the detection target is imaged without active radiation, but has the greatest defects of poor imaging quality and easiness in influence of the environment.
The second human body imaging security inspection technology is based on an active millimeter wave terahertz human body imaging technology. The technical working principle is that equipment firstly radiates millimeter waves to a human body, then receives the millimeter waves scattered by the human body or suspicious objects through a detector, and images the human body through a reconstruction algorithm. Representative of these are the Provision products [ Security & protection Systems "," Advanced personal screening "," 2016, [ Online ] from L3.
Available:http://www.sds.l-3com.com/products/advanced imagingtech.htm】。
At present, the one-dimensional single-transmitting single-receiving or quasi-single-transmitting single-receiving line array synthetic aperture imaging principle is generally adopted. The antenna array technology utilizing fast switch switching can be divided into two forms shown in figures 1 and 2 according to the fact whether receiving and transmitting antennas are integrated or not, the basic principle is the same, actual receiving and transmitting antenna units are arranged at equal intervals on the length of an aperture required by imaging according to the principle of half-wavelength spacing, the rear ends of the receiving and transmitting antennas are connected with receiving and transmitting equipment through a high-speed switch, a first group of receiving and transmitting antennas are combined with the receiving and transmitting equipment through a switch to complete one-time data acquisition, the switch is switched, a second group of receiving and transmitting antennas are controlled to be combined with the receiving and transmitting equipment through the switch to complete one-time data acquisition, the switch is sequentially controlled to be switched from a channel 1 to a channel N, N groups of data.
The one-dimensional array imaging mode of the receiving-transmitting integrated (receiving-transmitting split/quasi-single station) antenna has the defects that a large amount of antenna resources are needed, in order to realize the sampling of N equivalent units, the receiving-transmitting integrated antenna array needs N antenna units, the receiving-transmitting split antenna array needs 2N antenna units, and the utilization rate of the receiving-transmitting antenna is very low; in addition, as the number of antenna units is large for realizing the antenna array, and the distance between the antenna units needs to meet the requirement of the half-wavelength distance, when the working frequency is low, the physical realization difficulty is not large, but the realization difficulty is gradually increased along with the improvement of the working frequency.
In order to solve the above problems, documents [ IEEE transmissions ON geographic information AND REMOTE SENSING, vol.49, No.10, AND OCTOBER 2011 ] propose a sparsely distributed multi-input multi-output antenna layout scheme, as shown in fig. 3. Although the number of the antennas can be reduced by the antenna layout mode, due to the fact that the distance between the equivalent phase center and the receiving and transmitting antennas is large, only a back projection algorithm can be adopted, the calculation speed of the back projection algorithm is low, and the image reconstruction time is long.
Disclosure of Invention
According to an aspect of the present disclosure, there is provided a sparse multiple-input multiple-output array arrangement for active millimeter wave security inspection imaging, comprising a plurality of transmitting antennas for transmitting millimeter waves with a wavelength in the millimeter order and a plurality of receiving antennas for receiving millimeter waves with a wavelength in the millimeter order reflected by a human body and transmitted by the plurality of transmitting antennas; the plurality of transmitting antennas and the plurality of receiving antennas are arranged in two groups of antennas arranged in a first direction; the two groups of antennas are divided into a plurality of chips arranged along a first direction, each chip comprises N1 transmitting antennas arranged along the first direction in a first row and N2 receiving antennas arranged along the first direction in a second row, and N1 transmitting antennas and N2 receiving antennas are spaced apart along a second direction perpendicular to the first direction, wherein N1 and N2 are positive integers greater than or equal to 2, and N1 < N2; arranging, in each chip, at least one receiving antenna within an equal length range of a second row corresponding to a length of a space between two adjacent transmitting antennas arranged along the first row such that the number of transmitting antennas is less than the number of receiving antennas in each chip; and in each of the two groups of antennas, the combinations of N1 transmit antennas and the combinations of N2 receive antennas are alternately arranged in the first direction such that in each group of antennas, the N1 transmit antennas are located between the combinations of two N2 receive antennas.
According to one embodiment of the present disclosure, in each chip, N1 transmit antennas are spaced apart by a distance of an integer multiple of the wavelength of the millimeter wave, and N2 receive antennas are spaced apart by a distance of one time the wavelength of the millimeter wave.
According to one embodiment of the present disclosure, a last receiving antenna in the nth chip is spaced from a first transmitting antenna in the (N + 1) th chip by half of a millimeter wave wavelength in the first direction.
According to one embodiment of the present disclosure, the interval between the last receiving antenna in the nth chip and the first transmitting antenna in the (N + 1) th chip in the second direction is zero, so that all antennas in each of the two groups of antennas are arranged along a straight line.
According to one embodiment of the present disclosure, a distance between the last receiving antenna in the nth chip and the first transmitting antenna in the N +1 th chip in the second direction is not zero.
According to one embodiment of the present disclosure, the plurality of chips operate independently of each other, the receiving antenna in each chip does not receive the millimeter waves transmitted from the transmitting antenna of any chip in the vicinity, and the transmitting antenna in each chip does not transmit the millimeter waves to any chip in the vicinity.
According to one embodiment of the present disclosure, frequencies of millimeter waves emitted by the plurality of chips are different from each other.
According to one embodiment of the present disclosure, a spacer is disposed between adjacent chips.
According to one embodiment of the present disclosure, in each chip, at least one transmitting antenna is aligned with at least one receiving antenna such that a line therebetween is perpendicular to a first direction; or the connecting line of any transmitting antenna and any receiving antenna is not vertical to the first direction.
According to one embodiment of the present disclosure, in each chip, a midpoint of a connecting line of one transmitting antenna and one receiving antenna is regarded as virtual equivalent phase centers of the pair of transmitting antenna-receiving antenna, and a distance between adjacent equivalent phase centers is 0.3 to 0.7 times a wavelength of a millimeter wave.
According to one embodiment of the present disclosure, a distance between adjacent equivalent phase centers is 0.5 times a wavelength of the millimeter wave
According to one embodiment of the present disclosure, the two sets of antennas are spaced apart by a distance that is less than 10% of the imaging distance.
According to one embodiment of the present disclosure, the sparse multi-transmit multi-receive array arrangement further comprises a control switch for controlling the plurality of chips such that the plurality of chips transmit the millimeter waves in sequence.
According to an aspect of the present disclosure, there is provided a human body security inspection apparatus comprising one or more of the above-described sparse multi-transmit multi-receive array arrangements.
According to one embodiment of the present disclosure, a human body security inspection apparatus includes a first sparse multiple-transmit multiple-receive array arrangement and a second sparse multiple-transmit multiple-receive array arrangement, the first sparse multiple-transmit multiple-receive array arrangement and the second sparse multiple-transmit multiple-receive array arrangement being oppositely arranged so as to define an inspection space therebetween in which human body security inspection is performed, the first sparse multiple-transmit multiple-receive array arrangement and the second sparse multiple-transmit multiple-receive array arrangement each including one or more of the above sparse multiple-transmit multiple-receive array arrangements.
According to an embodiment of the present disclosure, the first sparse multiple-transmit multiple-receive array arrangement and the second sparse multiple-transmit multiple-receive array arrangement each include a plurality of the above sparse multiple-transmit multiple-receive array arrangements, the plurality of sparse multiple-transmit multiple-receive array arrangements are arranged in sequence along the second direction, or the plurality of sparse multiple-transmit multiple-receive array arrangements are arranged in sequence in a segmented manner along the first direction.
According to an embodiment of the present disclosure, the first sparse multiple-transmit-multiple-receive array arrangement and the second sparse multiple-transmit-multiple-receive array arrangement are translatable in a second direction, and the first direction is a horizontal direction and the second direction is a vertical direction, or the first direction is a vertical direction and the second direction is a horizontal direction; or the human body to be detected can stand in parallel to the first direction in the limited checking space and can rotate at any angle, and the first direction is a vertical direction and the second direction is a horizontal direction.
According to one embodiment of the disclosure, the plurality of rarefaction multiple-wrap array arrangements are arranged in three stages in sequence along the first direction, and the second section of rarefaction multiple-wrap array arrangement is connected at both ends to the first section of rarefaction multiple-wrap array arrangement and the third section of rarefaction multiple-wrap array arrangement to form a fold line, wherein an angle between the second section of rarefaction multiple-wrap array arrangement and the first section of rarefaction multiple-wrap array arrangement is in a range of 90 ° to 170 °, and an angle between the second section of rarefaction multiple-wrap array arrangement and the third section of rarefaction multiple-wrap array arrangement is in a range of 90 ° to 170 °.
According to an embodiment of the present disclosure, the first sparse multiple-transmit-multiple-receive array arrangement transmits millimeter waves from lowest frequency to highest frequency, and the second sparse multiple-transmit-multiple-receive array arrangement transmits millimeter waves from highest frequency to lowest frequency, or the second sparse multiple-transmit-multiple-receive array arrangement transmits millimeter waves from lowest frequency to highest frequency, and the first sparse multiple-transmit-multiple-receive array arrangement transmits millimeter waves from highest frequency to lowest frequency.
According to another aspect of the present disclosure, there is provided a human body security inspection method implemented using the human body security inspection apparatus described above.
The sparse multi-transmitting multi-receiving array arrangement scheme can greatly improve the data acquisition speed and the utilization rate of antenna units through a multi-transmitting multi-receiving array sparse design and control technology; the electric scanning is completely realized along the array direction (namely, the antennas are controlled to work one by one through a switch or the antennas are controlled to use frequency scanning one by one through the switch), the mechanical scanning is not needed, the rapid scanning can be realized, and the imaging speed is improved; moreover, a reconstruction algorithm based on fast Fourier change can be adopted, so that the reconstruction speed is obviously improved; meanwhile, the complexity of hardware is reduced, and the realizability of engineering is improved.
Drawings
Fig. 1 is a schematic diagram of a conventional one-dimensional single-transmit single-receive antenna array;
fig. 2 is a schematic diagram of a conventional one-dimensional mimo antenna array;
fig. 3 is a schematic diagram of a conventional one-dimensional mimo antenna array;
FIG. 4 illustrates a multi-transmit antenna-multi-receive antenna operating schematic;
fig. 5 shows a schematic diagram of a sparse multiple-input multiple-output array arrangement of one embodiment of the present disclosure, where the spacing between transmit antennas is 3 λ and the number of transmit antennas in each chip is 2;
fig. 6 shows a schematic diagram of a sparse multiple-input multiple-output array arrangement of one embodiment of the present disclosure, where the spacing between transmit antennas is 4 λ and the number of transmit antennas in each chip is 2;
fig. 7 shows a schematic diagram of a sparse multiple-input multiple-output array arrangement of one embodiment of the present disclosure, where the spacing between transmit antennas is 4 λ and the number of transmit antennas in each chip is 3;
figure 8 shows a schematic diagram of a sparse multiple-input multiple-output array arrangement of one embodiment of the present disclosure, where the spacing between transmit antennas is 4 λ, where the spacing between all receive antennas is equal to the spacing between all transmit antennas;
fig. 9 shows a schematic diagram of a sparse multiple-input multiple-output array arrangement of one embodiment of the present disclosure, where the spacing between transmit antennas is 6 λ and the number of transmit antennas in each chip is 2;
fig. 10 shows a schematic diagram of a sparse multiple-input multiple-output array arrangement of one embodiment of the present disclosure, wherein the spacing between the transmit antennas is 4 λ, and the spacing between the transmit antennas and the receive antennas of adjacent chips in the second direction is not zero;
fig. 11 shows a schematic diagram of a sparse multiple-input multiple-output array arrangement of one embodiment of the present disclosure, wherein the spacing between the transmit antennas is 6 λ, and the spacing between the transmit antennas and the receive antennas of adjacent chips in the second direction is not zero;
FIG. 12 illustrates a human body security check device of one embodiment of the present disclosure;
FIG. 13 illustrates a human body security device of one embodiment of the present disclosure;
FIG. 14 illustrates a human body security check device of one embodiment of the present disclosure;
FIG. 15 shows a top view of the human body screening device shown in FIG. 14;
FIG. 16 shows a schematic diagram of a sparse multiple-input multiple-output array arrangement of the human body security device as described in FIG. 14;
FIG. 17 illustrates a human body security device of one embodiment of the present disclosure;
figure 18 shows a broadband swept frequency modulated continuous wave SFCW mode of operation; and
figure 19 shows the frequency-fed continuous wave FMCW mode of operation with a broadband frequency sweep.
Detailed Description
While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the disclosure to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims. The figures are for illustration and are not drawn to scale.
The use of the terms "upper," "lower," "left," "right," and the like in this specification is not intended to limit the absolute orientation of the elements, but rather to describe relative positions of the elements in the figures to aid understanding; in this specification, "top side" and "bottom side" are orientations of upper and lower sides with respect to an object standing upright in general; "first," "second," and the like are also not intended to distinguish one element from another, but rather to distinguish one element from another.
Some basic knowledge of millimeter wave human body security for embodiments of the present disclosure is introduced.
The nyquist theorem means that the number of samples required along the aperture is determined by several factors, including wavelength, aperture size, target size, and distance to the target. The nyquist theorem is satisfied if the phase shift from one sample point to the next is less than pi. The worst case would be that the target is very close to the aperture and the sampling point is close to the edge of the aperture. For a spatial sampling interval Δ x, the worst case would be a phase shift of no more than 2k Δ x. Thus, the sampling rule can be expressed as:
Δx<(λ/4)
where λ 2 pi/k is the wavelength.
This result is more stringent than usual because the target (e.g., a human body) is typically closer to the aperture and the antenna beam width is typically less than 180 degrees. For this reason, applied imaging systems typically employ sampling intervals on the order of λ/2.
Taking the working frequencies of 24-30GHz and 70-80GHz as examples for comparison, if the corresponding wavelengths are 10mm and 4mm respectively, and the conventional one-dimensional arrays shown in fig. 1 and 2 are to be implemented, the spacing between the transmitting and receiving antennas is required to be 5mm and 2mm respectively, and assuming that the antenna aperture length is 1m, the transmitting and receiving integrated antenna array needs 200 and 500 antenna units respectively, and the transmitting and receiving split antenna array needs 400 and 1000 antenna units respectively. It can be seen that the number of antennas required increases dramatically as the antenna spacing becomes smaller with increasing frequency. The antenna spacing becomes smaller, which makes the design of the antenna unit and the array layout very difficult, and also limits the performance of the transmitting and receiving antenna. The increase of the number of the antennas not only increases the hardware cost and the complexity of the system, but also increases the data volume and changes the acquisition time. Therefore, the feasibility of the application and implementation of the one-dimensional array shown in fig. 1 and 2 in the aspect of high-frequency millimeter wave (50GHz-300GHz) human body imaging security inspection is not high, and the one-dimensional array does not have engineering implementation value.
Fig. 3 shows a conventional sparsely distributed mimo antenna layout, where T denotes a transmitting antenna and R denotes a receiving antenna, which can reduce the number of antennas, but has the following disadvantages: for example, because the distance between the equivalent phase center and the transmitting and receiving antenna is large, only a backward projection algorithm can be adopted, and the calculation speed of the backward projection algorithm is low, and the image reconstruction time is long. Backprojection originated from computed tomography technology, an accurate imaging algorithm based on time-domain signal processing. The basic idea is that for each imaging point in the imaging area, the time delay between the point to the receiving antenna and the transmitting antenna is calculated, and the contributions of all the echoes to the point are coherently superposed to obtain the corresponding pixel value of the point in the image, so that the coherent superposition processing is performed on the whole imaging area point by point, and the image of the imaging area can be obtained. The biggest defect of the algorithm is that each point in the whole imaging interval needs to be reconstructed, the reconstruction speed is low, and the time consumption is long; in addition, the receiving antennas at the two ends are densely distributed, and the spacing needs to satisfy the Nyquist theorem. Such as the 170GHz-260 GHz band, a typical transmit and receive antenna aperture is 10.8mm, while the center frequency corresponds to a half wavelength of 1.36 mm. Obviously, this antenna arrangement is not suitable. One solution is to sparsely receive antennas, so that the center-to-center spacing of the equivalent phase is larger than a half-wave, but insufficient antenna sampling can cause severe artifacts in the reconstructed image.
In order to solve the above defects, the present disclosure provides a sparse multi-transmit multi-receive array arrangement scheme, which can greatly improve the data acquisition speed and the utilization rate of the antenna unit through a multi-transmit multi-receive array sparse design and control technology; the electric scanning is completely realized along the array direction (namely, the antennas are controlled to work one by one through a switch or the antennas are controlled to use frequency scanning one by one through the switch), the mechanical scanning is not needed, the rapid scanning can be realized, and the imaging speed is improved; moreover, a reconstruction algorithm based on fast Fourier change can be adopted, so that the reconstruction speed is obviously improved; meanwhile, the complexity of hardware is reduced, and the realizability of engineering is improved.
According to the embodiment of the disclosure, a one-dimensional sparse multi-transmitting and multi-receiving array arrangement for active millimeter wave imaging is provided, after the sparse multi-transmitting and multi-receiving array is subjected to single-station equivalence and electric switch control, the sparse multi-transmitting and multi-receiving array finally forms an equivalent unit, the maximum distance between equivalent units is slightly larger than or equal to half of the wavelength corresponding to the working frequency, and the equivalent units are equivalent phase centers.
For convenience of explanation, referring to fig. 4, a multiple-transmission multiple-reception system is shown, which constructs an X-Y coordinate system, sets a sparse on the X-axis for transmission and reception combination, and uses at(xt，yt) And Ar(xr，yr) Respectively representing a pair of transmitting antennas and receiving antennas of the transceiving combination and the position coordinates of the transmitting antennas and the receiving antennas.
For a point object within the object region, I denotes the location of I (x)n，yn) Point target of scattering, definition I and transmitting antenna AtA distance of Rt，nI and a receiving antenna ArAt a distance of Rr，n，R0Is the vertical distance between the center of the target area and the linear array, i.e., the imaging distance.
The echo signal after scattering by the point target can be represented as Sn(xt，yt；xr，yr；Kω)＝σ(xn，yn)exp[-jKω(Rt，n+Rr，n)]
Where σ (x, y) is the scattering coefficient of the human body, KωJ is the spatial frequency of the frequency stepped signal and is in units of imaginary numbers.
For a transceiving combination AtArThe echo signals received from the target area are:
where D is the imaging area.
The equivalent position of the transmit and receive signals can be represented by the phase center of the antenna, which is the physical center of two separate antennas or apertures. In a multiple-input multiple-output system, where a transmitting antenna corresponds to multiple receiving antennas, and where the receiving antenna elements and the transmitting antenna elements are not co-located, this spatially separated system of transmitting and receiving antennas can be simulated using a virtual system in which a virtual location is added between each set of transmitting and receiving antennas, this location being referred to as the equivalent phase center. The echo data collected by the receiving and transmitting antenna combination can be equivalent to the echo collected by the self-receiving antenna at the position of the equivalent phase center Ae (xe, ye).
For the transmit-receive combination, the relationship of the physical coordinates between the antennas can be expressed as:
using the principle of equivalent phase centers, the equivalent echo signal can be expressed as:
fig. 5 shows a schematic diagram of a sparse multiple-input multiple-output array arrangement according to an embodiment of the present disclosure, according to the above-described sparse multiple-input multiple-output array arrangement principle of active millimeter wave imaging of the present disclosure. The sparse multi-transmit multi-receive array arrangement of fig. 5 may be constructed specifically by:
firstly, determining the number N and the spacing d of required equivalent units (the maximum is slightly larger than or equal to half of the wavelength corresponding to the working frequency, and the equivalent units are equivalent phase centers) according to the requirements of imaging index parameters such as the working frequency (wavelength lambda), the antenna array length Lap and the like;
then, actual antenna units are arranged in a transceiving split mode, transmitting antennas/receiving antennas are distributed according to two parallel straight lines respectively, the interval is dtr, and an antenna array formed by the transmitting antennas and the receiving antennas is distributed along the two straight lines and can be divided into a plurality of chips;
then, designing the arrangement of transmitting antenna units, wherein the total number Nt of transmitting antennas is any positive integer and is determined by the aperture Lap of the antenna array; the distance between adjacent transmitting antennas is M lambda, (M is a positive integer, M is more than or equal to 2), and N1 transmitting antennas are arranged in each chip; assuming that there are only two transmit antennas per chip, then the antenna array aperture that constitutes Lap requires Nc-Nt/2 chips.
Next, the layout of the receiving antenna units is designed, the total number of the receiving antennas is any positive integer, the receiving antennas are distributed at equal intervals, the interval is λ, and there are N2 receiving antennas in each chip.
The distance dtr between the transmitting antenna and the receiving antenna in each chip can be any value, on one hand, the lower transceiving antenna array can be placed, the mutual coupling is small, on the other hand, 2dtr/z0 is required to be less than 10%, and z0 is required to be the imaging distance.
The sparse multiple-input multiple-output array arrangement constructed according to the above steps includes a plurality of transmitting antennas for transmitting millimeter waves having a wavelength on the order of millimeters and a plurality of receiving antennas for receiving millimeter waves having a wavelength on the order of millimeters reflected by a human body transmitted by the plurality of transmitting antennas; the plurality of transmitting antennas and the plurality of receiving antennas are arranged into two groups of antennas arranged in a first direction D1; the two groups of antennas are divided into a plurality of chips arranged along a first direction D1, each chip comprises N1 transmitting antennas arranged in a first row along the first direction D1 and N2 receiving antennas arranged in a second row along the first direction D1, and the N1 transmitting antennas and the N2 receiving antennas are spaced along a second direction D2 perpendicular to the first direction D1, wherein N1 and N2 are positive integers greater than or equal to 2, and N1 < N2; in each chip, at least one receiving antenna is arranged within an equal length range of a second row corresponding to a length of a space between two adjacent transmitting antennas arranged along a first row such that the number of transmitting antennas is less than the number of receiving antennas in each chip. In the present disclosure, in each of the two groups of antennas, combinations of N1 transmit antennas and combinations of N2 receive antennas are alternately arranged in the first direction D1 such that, in each group of antennas, N1 transmit antennas are located between the combinations of two N2 receive antennas.
In the present disclosure, in the embodiment shown in FIG. 5, each chip includes 2 transmit antennas, 5 receive antennas, and in the first row, 2 transmit antennas t3-t4 are located between the first set of 5 receive antennas r1-r5 and the second set of receive antennas r11-r 15; in each chip, the number of transmitting antennas is 2 and less than the number of receiving antennas. In the embodiment shown in FIG. 6, each chip includes 2 transmit antennas, 4 receive antennas, and in the first row, 2 transmit antennas t3-t4 are located between the first set of 4 receive antennas r1-r4 and the second set of receive antennas r9-r 12; in each chip, the number of transmitting antennas is 2 and less than the number of receiving antennas. In the present disclosure, the number of the transmitting antennas may also be an odd number, for example, 3, in each chip, as shown in fig. 7, each chip includes 3 transmitting antennas and 8 transmitting antennas, so that the number of the transmitting antennas is 3 and less than the number of the receiving antennas in each chip. In the embodiments shown in fig. 8-11, the number of transmit antennas is also less than the number of receive antennas in each chip.
Therefore, in the sparse multi-transmit multi-receive array arrangement according to the present disclosure, the number of receiving antennas can be reduced while image clarity is ensured, the number of transmitting antennas is less than the number of receiving antennas in each chip, thereby reducing the total number of elements, and thus reducing manufacturing difficulty and cost.
The equivalent phase center will be described in detail below. The midpoint of the line connecting one transmitting antenna and one receiving antenna in each chip is taken as the virtual equivalent phase center of the pair of transmitting antenna-receiving antenna. In order to reduce the number of transmitting antennas and receiving antennas and generally avoid overlapping of equivalent phase centers, a distance between adjacent equivalent phase centers of about half the wavelength of the millimeter wave may suffice to finally constitute a clear image, for example, a distance between adjacent equivalent phase centers of 0.3 to 0.7 times the wavelength of the millimeter wave. In other words, when the distance between the adjacent equivalent phase centers is too much larger than half the wavelength of the millimeter wave, the image may not be clear. Therefore, the pitch of the equivalent phase centers formed in each chip is required to be 0.3 to 0.7 times the wavelength of the millimeter wave, and preferably, the pitch is 0.5 λ.
In one embodiment, in each chip, N1 transmit antennas are spaced apart by a distance (M λ) that is an integer multiple of the wavelength of the millimeter wave, and N2 receive antennas are spaced apart by a distance that is one multiple of the wavelength λ of the millimeter wave. In the present embodiment, in the transmitting antenna and the receiving antenna formed at this interval, the interval between the adjacent equivalent phase centers of the plurality of equivalent phase centers that they form is half the interval between the adjacent receiving antennas, that is, 0.5 λ. As shown in fig. 5, in each chip, adjacent transmitting antennas are spaced at intervals of 3 λ, receiving antennas are spaced at intervals of λ, and the formed equivalent phase centers are spaced at intervals of 0.5 λ. As shown in fig. 6, 7, 8, and 10, in each chip, adjacent transmitting antennas are spaced at intervals of 4 λ, receiving antennas are spaced at intervals of λ, and the formed equivalent phase centers are spaced at intervals of 0.5 λ. As shown in fig. 9 and 11, in each chip, adjacent transmitting antennas are spaced at intervals of 6 λ, receiving antennas are spaced at intervals of λ, and the resulting equivalent phase centers are spaced at intervals of 0.5 λ. The above figures show only exemplary spacings and those skilled in the art will appreciate that the transmit antennas can be spaced apart at other distances, such as spacings of 5 λ, 7 λ, 8 λ, etc., as long as the spacing is more than 2 wavelengths apart.
In order to ensure that the interval between the last equivalent phase center in the previous chip and the first equivalent phase center in the subsequent chip is also 0.5 λ between the adjacent chips. In one embodiment, the last receiving antenna in the nth chip is spaced from the first transmitting antenna in the (N + 1) th chip by half the millimeter wave wavelength in the first direction D1. For example, as shown in fig. 5, the receiving antenna r5 and the transmitting antenna t3 are spaced apart by 0.5 λ in the first direction D1. As shown in fig. 6, the receiving antenna r4 and the transmitting antenna t3 are spaced apart by 0.5 λ in the first direction D1. As shown in fig. 7, the receiving antenna r8 and the transmitting antenna t4 are spaced apart by 0.5 λ in the first direction D1. As shown in fig. 8, the receiving antenna r5 and the transmitting antenna t3 are spaced apart by 0.5 λ in the first direction D1. As shown in fig. 9, the receiving antenna r6 and the transmitting antenna t3 are spaced apart by 0.5 λ in the first direction D1.
In some embodiments of the present disclosure, as shown in fig. 5-9, the last receiving antenna in the nth chip is spaced from the first transmitting antenna in the (N + 1) th chip by zero in the second direction D2, such that all antennas in each of the two groups of antennas are aligned along a straight line. In these embodiments, the structures of adjacent chips are substantially similar, so that the manufacturing process of the chips is more simplified.
In some cases, when λ is relatively small, for example, λ is 3 to 4mm, the channel isolation between adjacent chips is relatively poor. To solve this problem, the longitudinal dimension of one of the chips may be increased. In the embodiment shown in fig. 10 and 11, the spacing between the last receiving antenna in the nth chip and the first transmitting antenna in the (N + 1) th chip in the second direction D2 is not zero. In the embodiment shown in fig. 10, the interval between r4 and t3 in the first direction D1 is 0.5 λ, and the interval in the second direction D2 is not 0. In the embodiment shown in fig. 11, the interval between r6 and t3 in the first direction D1 is 0.5 λ, and the interval in the second direction D2 is not 0. By such an arrangement, the channel isolation between adjacent chips can be optimized.
In one embodiment of the present disclosure, the plurality of chips operate independently of each other, the receiving antenna in each chip does not receive the millimeter waves transmitted from the transmitting antenna of any chip in the vicinity, and the transmitting antenna in each chip does not transmit the millimeter waves to any chip in the vicinity. In the embodiments shown in fig. 5-11, the transmitting antenna in each chip transmits only the millimeter waves to the receiving antennas in the chip, and the receiving antennas only receive the millimeter waves transmitted by the transmitting antenna in the chip. Through the arrangement, the chips do not need to be interacted, namely, the receiving and sending of each chip are independent, and the chips beside the chips do not need to receive. The array integration is more convenient, a certain chip is broken, and other chips are irrelevant; secondly, one chip transmits a certain frequency, and the chips beside the chip transmit other frequencies, namely, the frequencies are orthogonalized, so that real-time performance can be provided, and the number of electric switches is reduced; and thirdly, a spacer can be added between adjacent chips to reduce the crosstalk.
In some embodiments of the present disclosure, in each chip, at least one transmit antenna is aligned with at least one receive antenna such that a line between the two is perpendicular to the first direction, for example as shown in fig. 5 and 8. In other embodiments of the present disclosure, the line connecting any transmitting antenna and any receiving antenna is not perpendicular to the first direction, for example, as shown in fig. 6-7 and 9-11, in these embodiments, the first transmitting antenna and the first receiving antenna in each chip may be misaligned, and the distance of the misalignment may be arbitrarily selected according to the size requirement of the chip design, for example, in the range of 0 to λ. The offset distance is preferably 0.5 λ.
The sparse array arrangement method provided by the disclosure is based on a single-station equivalent principle, namely after the array is designed to be subjected to single-station equivalent and electric switch control, the finally formed equivalent phase center (called equivalent unit in the disclosure) meets the Nyquist sampling law, namely the distance between the finally formed equivalent units of the array is slightly larger than or equal to half of the wavelength corresponding to the working frequency. According to the principle, the short wavelength of millimeter waves in a high-frequency band is considered, and in order to take engineering realizability into consideration, an array sparsity design and an array switch control technology are adopted, and finally the requirement of distribution of half-wavelength-distance equivalent units is met.
In the following, taking the interval M λ between the transmitting antennas to be 4 λ as an example, and when the array length is 1M, the design process of forming an array by calculating the transmitting antennas Nt to be 84 transmitting antennas and the receiving antennas Nr to be 168 receiving antennas is taken as an example, to describe the one-dimensional sparse array arrangement method disclosed in the present disclosure, and a person skilled in the art can perform the one-dimensional sparse array arrangement according to the teachings of the present disclosure.
Firstly, the number and the interval of the required equivalent units are determined according to the requirements of imaging index parameters, such as imaging resolution, sidelobe level and the like, namely the distribution of the equivalent virtual array is determined. The spacing of the equivalent array elements needs to be at most slightly greater than or equal to half the operating wavelength.
Then, the actual antenna units are arranged in a transceiving split mode, the two groups of antennas are distributed according to two parallel straight lines, the distance between the straight lines can be any value, but is as small as possible (can be lambda, 1.5 lambda, 2 lambda, 3 lambda, 4 lambda and the like), the size of the antenna unit and the size of the array are reasonably selected according to the actual design requirement, and the size of the array is designed to be 1 m.
Next, as shown in fig. 6, the arrangement of the transmitting antenna units is designed, and the total number of the transmitting antennas is 84 (the number can be expanded to any other number, and the specific number is determined by factors such as imaging resolution, imaging range, etc.).
Next, the arrangement of the receiving antenna units is designed, and the total number of the receiving antennas is 168 (the number can be expanded to any other number, the specific number is determined by factors such as imaging resolution, imaging range, and the like, and the distance between each receiving antenna is λ.
In operation, a first transmitting antenna in a first chip corresponds to 4 receiving antennas; the second transmitting antenna in the first chip corresponds to 4 receiving antennas. The second chip to the Nth chip operate in the same manner as the first chip. The multiple chips sequentially transmit millimeter waves to obtain equivalent unit distribution with equal interval of 0.5 lambda, and finally obtain equivalent element distribution meeting the requirement of the Nyquist sampling law; and sequentially switching the transmitting antennas to complete one-time data acquisition through electric switch control. Then, synthetic aperture scanning is carried out in the orthogonal direction of the array, and the scanning of the two-dimensional aperture is completed. And finally, combining a synthetic aperture holographic algorithm based on fast Fourier change to realize fast reconstruction and finish imaging test. The working frequency is preferably 76-81GHz, 81-86GHz and 10-40GHz, and can also be a single frequency point, and the wavelength lambda is selected as the wavelength corresponding to the central frequency or the highest frequency.
The so-called synthetic aperture technique is that the object is stationary, and the transmit-receive array module mechanically scans along the direction orthogonal to the array, thereby completing the scanning of the object. In an alternative embodiment, the transmit-receive array may be stationary, and the object may be moved in a direction orthogonal to the array to complete scanning of the object. When the detected person enters the detected space, the transmitting antennas in the MIMO line array sequentially transmit and the corresponding receiving antennas receive. And then, mechanically scanning in the orthogonal direction of the array, wherein the scanning step length is equal to or slightly larger than half of the central wavelength until the whole area array scanning is completed, and obtaining all scattering data of the detected person in different viewing angles. Namely, the synthetic aperture technology is used for imaging the detected object. The length of the mechanical scan was taken to be (0.8m-2.5 m).
If the millimeter wave transceiving link is single-frequency millimeter waves, scattering signals at different distances form interference on a scanning plane, and finally a reconstructed image has a serious speckle effect. In order to realize three-dimensional holographic imaging, a millimeter wave transceiving link needs to be broadband, and the broadband frequency sweep is mainly divided into two modes of frequency modulation continuous wave FMCW and frequency advance continuous wave SFCW.
The SFCW mode of operation is shown in fig. 18. The working mode of the step frequency continuous wave SFCW is that after one frequency point is scanned, the next frequency point is continued. SFCW is easy to synthesize signals of arbitrary bandwidth.
The FMCW mode of operation is shown in fig. 19. The FMCW mode of operation emits a chirped signal whose frequency varies linearly with time, which is reflected back by the object after a certain distance, and at this time has a certain frequency difference from the reference signal, which is proportional to the distance traveled.
The sparse multi-transmit multi-receive array arrangement is configured to complete scanning of a group of transmitting antennas by sequentially transmitting millimeter waves by the plurality of chips arrayed in the first direction, and to perform scanning in the second direction D2 by movement of the sparse multi-transmit multi-receive array arrangement in the second direction D2 relative to the human body to be examined. In one example, the relative motion may be immobilization of the subject, and the sparse multiple input multiple output array arrangement is translated along the second direction D2 for scanning along the second direction D2, thereby enabling two-dimensional scanning of the subject. For example, the sparse multiple-input multiple-output array arrangement scans in a second direction D2 with a step size of 0.5 λ, as shown in fig. 12, 13, 14. In another example, the relative motion may be a rotation of the human subject relative to the sparse multi-transmit multi-receive array arrangement, as shown in fig. 17, while the sparse multi-transmit multi-receive array arrangement is stationary.
In one embodiment, the sparse multi-transmit multi-receive array arrangement is configured as a fourier transform based synthetic aperture holographic algorithm, completing image reconstruction on the correct imaging area at a time, the imaging formula being:
where σ (x, y) is the scattering coefficient of the human body, R0Is the imaging distance, FT2DIn order to perform a two-dimensional fourier transform,
is two-dimensional inverse Fourier transform, j is an imaginary unit, k is a propagation constant, kx、kyAre the spatial propagation constants, respectively;
receiving echo signals of a human body for a pair of transmitting antenna-receiving antenna combination; kωIs the spatial frequency of the frequency stepped signal.
And when all transmitting antennas in all the chips transmit in sequence, completing one-time transverse data acquisition. According to the principle of equivalent phase center, the echo data can be equivalent to the echo data acquired by the phase center. The interval between these equivalent phases is 0.5 λ, and the distribution of equivalent elements satisfies the nyquist sampling law. Then, synthetic aperture scanning, i.e. mechanical scanning, is performed in the direction orthogonal to the array, i.e. the second direction D2, to complete the scanning of the two-dimensional aperture, and the step size of the scanning also needs to satisfy the theorem, i.e. half wavelength of 0.5 λ.
After completing the two-dimensional aperture scan, the acquired echo data may be represented as 5 (x)t，yt；xr，yr；Kω。
And finally, combining a synthetic aperture holographic algorithm based on fast Fourier change to realize fast reconstruction and finish imaging.
The imaging algorithm aims to invert an image of a target from an echo expression, namely a scattering coefficient sigma (x, y) of the target, and is a synthetic aperture holographic algorithm based on Fourier transform, so that the point-by-point reconstruction of the whole imaging region is not needed like a subsequent projection algorithm, and the reconstruction of a correct imaging region is completed at one time by using the advantage of fast Fourier transform. The imaging formula is:
where R0 is the imaging distance.
In an embodiment of the present disclosure, there is also provided a human body security inspection apparatus comprising one or more of the above-described sparse multi-transmit multi-receive array arrangements.
In one embodiment, as shown in fig. 12, the human body security inspection apparatus comprises a first sparse multiple-transmit multiple-receive array arrangement 100 and a second sparse multiple-transmit multiple-receive array arrangement 200, wherein the first sparse multiple-transmit multiple-receive array arrangement and the second sparse multiple-transmit multiple-receive array arrangement are oppositely arranged so as to define an inspection space S therebetween in which human body security inspection is conducted. The first and second sparse multiple-transmit-multiple-receive array arrangements 100 and 200 respectively comprise one or more of the above-described sparse multiple-transmit-multiple-receive array arrangements,
in one embodiment, in the case of including a plurality of sparse multi-transmission multi-reception array arrangements, the plurality of sparse multi-transmission multi-reception array arrangements are sequentially arranged along the second direction D2, the second direction D2 can be a vertical direction as shown in fig. 12, and the arrangement direction of the transmission antenna and the reception antenna (i.e., the first direction D1) can be a horizontal direction. Further, the second direction D2 may also be a horizontal direction as shown in fig. 13 and 17, and the arrangement direction of the transmitting antenna and the receiving antenna (i.e., the first direction D1) may be a vertical direction.
In another embodiment, in the case of including a plurality of sparse multi-transmit multi-receive array arrangements, the plurality of sparse multi-transmit multi-receive array arrangements are sequentially arranged in a stepwise manner along the first direction D1, as shown in fig. 14. In the embodiment shown in fig. 14-16, the plurality of sparse multiple access array arrangements are arranged in three sequential stages along the first direction D1, with the second stage sparse multiple access array arrangement 2 being connected at both ends to the first stage 1 sparse multiple access array arrangement and the third stage sparse multiple access array arrangement 3 to form a fold line. As shown in fig. 15 and 16, the angle between the second stage of the rarefaction multiple-input multiple-output array arrangement 2 and the first stage of the rarefaction multiple-input multiple-output array arrangement 1 is in the range of 90 ° to 170 °, and the angle between the second stage of the rarefaction multiple-input multiple-output array arrangement 2 and the third stage of the rarefaction multiple-output array arrangement 3 is in the range of 90 ° to 170 °. The embodiment shown in fig. 14 provides a millimeter wave three-dimensional holographic scanning imaging device, which comprises at least 6 transceiving arrays, and forms a top view shown in fig. 15. The first, second and third sections of the sparse multiple input multiple output array arrangement 1,2 and 3 all employ multiple input multiple output array arrangements. The length range of the three arrays is 0.3m-0.8m, namely a normal person can stand in the radius of the area defined by the three arrays. And the six transceiving arrays perform mechanical scanning in the vertical direction, and the step length of the mechanical scanning is selected to be the half wavelength of the working wavelength. And after the whole human body is scanned, complete scattered field data are obtained and then transmitted to the data processing unit, and the data are reconstructed by utilizing a holographic algorithm to form a detected human body image. Finally, the image is transmitted to a display unit.
To enable two-dimensional scanning of the sparse multi-transmit multi-receive array arrangement, in one embodiment, the first and second sparse multi-transmit multi-receive array arrangements 100, 200 are translatable in a second direction D2. As shown in fig. 12, the first direction D1 is a horizontal direction and the second direction D2 is a vertical direction, or as shown in fig. 13, the first direction D1 is a vertical direction and the second direction D2 is a horizontal direction.
In one embodiment, to avoid interference of the millimeter waves transmitted by the first and second sparse multiple-transmission-multiple- reception array arrangements 100, 200, it is preferable to have the first and second sparse multiple-transmission-multiple- reception array arrangements 100, 200 spatially separated while scanning. For example, in the embodiment shown in fig. 12, the first sparse multiple-emission multiple-reception array arrangement 100 is scanned from top to bottom in the vertical plane in which it is located, and the second sparse multiple-emission multiple-reception array arrangement 200 is scanned from bottom to top in the vertical plane in which it is located, respectively; in the embodiment shown in fig. 13, the first sparse, multiple-transmission, multiple-reception array arrangement 100 is scanned from left to right in its vertical plane, and the second sparse, multiple-transmission, multiple-reception array arrangement 200 is scanned from right to left in its vertical plane, respectively.
In another embodiment, in order to realize the two-dimensional scanning of the rarefaction multi-transmit multi-receive array arrangement, the rarefaction multi-transmit multi-receive array arrangement does not perform a translational motion, but as shown in fig. 17, the human body to be examined can stand parallel to the first direction D1 and can rotate at any angle in the defined examination space, and the first direction D1 is a vertical direction and the second direction D2 is a horizontal direction. The rotation angle is preferably 360 °.
In the whole process of scanning the object to be measured by the first sparse multiple-emission multiple-reception array arrangement 100 and the second sparse multiple-emission multiple-reception array arrangement 200 together, the frequencies of millimeter waves emitted by the first sparse multiple-emission multiple-reception array arrangement 100 and the second sparse multiple-emission multiple-reception array arrangement 200 cannot interfere with each other. In one embodiment, when scanning is started, the transmitting antennas of the first sparse multiple-transmit-multiple-receive array arrangement 100 sequentially transmit millimeter wave signals by controlling the switch, and the transmitting antennas of the second sparse multiple-transmit-multiple-receive array arrangement 200 sequentially transmit millimeter wave signals after all transmitting antennas of the first sparse multiple-transmit-multiple-receive array arrangement 100 have transmitted millimeter wave signals, so that the first and second sparse multiple-transmit-multiple-receive array arrangements 100 and 200 transmit signals time-divisionally and therefore do not interfere with each other. In another embodiment, when starting the scan, the first sparse multiple-transmit-multiple-receive array arrangement 100 transmits millimeter waves from lowest frequency to highest frequency, while the second sparse multiple-transmit-multiple-receive array arrangement 200 transmits millimeter waves from highest frequency to lowest frequency, by controlling the switches; alternatively, the second sparse multiple-transmit-multiple-receive array arrangement 200 goes from lowest frequency to highest frequency, while the first sparse multiple-transmit-multiple-receive array arrangement 100 goes from highest frequency to lowest frequency. Thus, at the same time, the frequencies transmitted by the first and second sparse multiple-transmission-multiple- reception array arrangements 100 and 200 are different and thus do not interfere with each other.
In the present embodiment, the first and second sparse multiple input multiple output array arrangements 100 and 200 may be scanned separately, with the scanning signals of both being used to form an image of the human body.
When the human body security check equipment disclosed by the invention is used for carrying out security check on a human body such as a passenger, the human body only needs to stay in the human body security check equipment, namely, the first sparse multiple-input multiple-output array arrangement 100 and the second sparse multiple-input multiple-output array arrangement 200 are arranged between the first sparse multiple-input multiple-output array arrangement 100 and the second sparse multiple-input multiple-output array arrangement 200, the first sparse multiple-input multiple-output array arrangement 100 and the second sparse multiple-output array arrangement 200 scan or scan one side of the human body at different times simultaneously, then signals obtained by scanning are sent to a processor or a controller, image processing is carried out through the processor or the controller to form.
In one embodiment of the present disclosure, there is also provided a method of performing detection on a human body using a sparse multi-transmit multi-receive array arrangement as described above.
Although a few embodiments of the present general patent concept have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general patent concept, the scope of which is defined in the claims and their equivalents.
Claims (20)
1. A sparse multiple-input multiple-output array arrangement for active millimeter wave security inspection imaging comprises a plurality of transmitting antennas and a plurality of receiving antennas, wherein the transmitting antennas are used for transmitting millimeter waves with millimeter-scale wavelengths, and the receiving antennas are used for receiving millimeter waves with millimeter-scale wavelengths reflected by a human body and transmitted by the transmitting antennas;
the plurality of transmitting antennas and the plurality of receiving antennas are arranged in two groups of antennas arranged in a first direction;
the two groups of antennas are divided into a plurality of chips arranged along a first direction, each chip comprises N1 transmitting antennas arranged in a first row along the first direction and N2 receiving antennas arranged in a second row along the first direction, and N1 transmitting antennas and N2 receiving antennas are spaced apart along a second direction perpendicular to the first direction, wherein N1 and N2 are positive integers greater than or equal to 2, and N1 < N2;
arranging, in each chip, at least one receiving antenna within an equal length range of a second row corresponding to a length of a space between two adjacent transmitting antennas arranged along the first row such that the number of transmitting antennas is less than the number of receiving antennas in each chip; and
in each of the two groups of antennas, combinations of N1 transmit antennas and combinations of N2 receive antennas are alternately arranged in the first direction such that in each group of antennas, N1 transmit antennas are located between the combinations of two N2 receive antennas.
2. The sparse multi-transmit multi-receive array arrangement of claim 1, wherein in each chip, the N1 transmit antennas are spaced apart by a distance that is an integer multiple of a wavelength of the millimeter waves and the N2 receive antennas are spaced apart by a distance that is one time a wavelength of the millimeter waves.
3. The sparse multi-transmit multi-receive array arrangement of claim 2, wherein a last receive antenna in an nth chip is spaced from a first transmit antenna in an N +1 th chip by half a millimeter wave wavelength in the first direction.
4. The sparse multiple transmit multiple receive array arrangement of claim 3, wherein a last receive antenna in an Nth chip is spaced from a first transmit antenna in an N +1 th chip by zero in the second direction such that all antennas in each of the two groups of antennas are aligned along a straight line.
5. The sparse multiple transmit multiple receive array arrangement of claim 3, wherein a spacing in the second direction of a last receive antenna in an Nth chip from a first transmit antenna in an N +1 th chip is non-zero.
6. The sparse multiple-transmit multiple-receive array arrangement of claim 3, wherein the plurality of chips operate independently of one another, the receive antenna in each chip does not receive millimeter waves transmitted from the transmit antenna of any chip in the vicinity, nor does the transmit antenna in each chip transmit millimeter waves to any chip in the vicinity.
7. The sparse multiple-transmit-multiple-receive array arrangement of claim 3, wherein frequencies of millimeter waves emitted by the plurality of chips are different from one another.
8. The sparse multiple transmit multiple receive array arrangement of claim 3, wherein spacers are provided between adjacent chips.
9. The sparse multi-transmit multi-receive array arrangement of claim 1, wherein in each chip at least one transmit antenna is aligned with at least one receive antenna such that a line between them is perpendicular to a first direction; or
The connecting line of any transmitting antenna and any receiving antenna is not vertical to the first direction.
10. The sparse multi-transmit multi-receive array arrangement of claim 1, wherein in each chip, a midpoint of a connecting line of one transmit antenna and one receive antenna is regarded as a virtual equivalent phase center of the pair of transmit antenna-receive antenna, and a distance between adjacent equivalent phase centers is 0.3 to 0.7 times a wavelength of the millimeter wave.
11. The sparse multiple transmit receive array arrangement of claim 10, wherein a distance between adjacent equivalent phase centers is 0.5 times a wavelength of a millimeter wave.
12. The sparse multi-transmit multi-receive array arrangement of claim 1, wherein two groups of antennas are spaced apart by a distance less than 10% of an imaging distance.
13. The sparse multi-transmit multi-receive array arrangement of claim 1, further comprising a control switch for controlling the plurality of chips such that the plurality of chips transmit millimeter waves in sequence.
14. A human security device comprising one or more sparse multi-transmit multi-receive array arrangements according to any one of claims 1-13.
15. The human security inspection apparatus of claim 14 comprising a first and a second sparse multiple-transmit-multiple-receive array arrangement, the first and second sparse multiple-transmit-multiple-receive array arrangements being oppositely arranged so as to define an inspection space therebetween in which human security inspection is conducted,
the first and second sparse multiple-transmit-multiple-receive array arrangements respectively comprising one or more sparse multiple-transmit-multiple-receive array arrangements according to any one of claims 1-13.
16. The human security inspection device of claim 15, wherein the first and second sparse multiple-transmit multiple-receive array arrangements each comprise a plurality of sparse multiple-transmit multiple-receive array arrangements according to any one of claims 1 to 12, the plurality of sparse multiple-transmit multiple-receive array arrangements being arranged sequentially along the second direction, or the plurality of sparse multiple-transmit multiple-receive array arrangements being arranged sequentially in a segmented manner along the first direction.
17. The human security device of claim 15, wherein the first and second sparse multiple-input multiple-output array arrangements are translatable in a second direction, and the first direction is a horizontal direction and the second direction is a vertical direction, or the first direction is a vertical direction and the second direction is a horizontal direction; or
The human body to be detected can stand in parallel to the first direction in the limited checking space and can rotate at any angle, the first direction is a vertical direction, and the second direction is a horizontal direction.
18. The human security device of claim 15, wherein the plurality of rarefaction multiple entry array arrangements are arranged in three stages in sequence along the first direction, the second stage of rarefaction multiple entry array arrangement being connected at both ends to the first stage of rarefaction multiple entry array arrangement and the third stage of rarefaction multiple entry array arrangement to form a fold line,
wherein an angle between the second stage of the rarefaction multiple-input multiple-output array arrangement and the first stage of the rarefaction multiple-input multiple-output array arrangement is in a range of 90 DEG to 170 DEG, an
The included angle between the second and third sections of the rarefaction multiple-input multiple-output array arrangement is in the range of 90-170 degrees.
19. The human body security inspection device of claim 15, wherein the first sparse multiple-transmit-multiple-receive array arrangement transmits millimeter waves from lowest frequency to highest frequency and the second sparse multiple-transmit-multiple-receive array arrangement transmits millimeter waves from highest frequency to lowest frequency, or the second sparse multiple-transmit-multiple-receive array arrangement transmits millimeter waves from lowest frequency to highest frequency and the first sparse multiple-transmit-multiple-receive array arrangement transmits millimeter waves from highest frequency to lowest frequency.
20. A human security method implemented using the human security device of any one of claims 14-19.
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| CN114460659A (en) * | 2021-12-31 | 2022-05-10 | 清华大学 | Security equipment |
| CN116047509A (en) * | 2022-12-05 | 2023-05-02 | 重庆邮电大学 | Equivalent Half-Wavelength Uniform Sampling Millimeter-Wave MIMO Array Scanning and Imaging Method |
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