阅读说明：本技术 一种圆柱孔径mimo阵列天线、成像方法及补偿方法 (Cylindrical aperture MIMO array antenna, imaging method and compensation method ) 是由 李世勇 王硕光 孙厚军 敬汉丹 王泽昊 邢光楠 于 2020-05-25 设计创作，主要内容包括：本发明公开了一种圆柱孔径MIMO阵列天线、成像方法及补偿方法,MIMO多子阵成像体制可以节省阵元数,加工方便,柱面阵列可以取得更好的成像效果；与本发明提出的补偿方案相结合,可以较好地补偿通道实际收发位置与等效位置之间的波程差,从而取得很好的三维成像效果,适合于毫米波人体安检成像；当阵列口面较大时,按照本发明提供的方案对每个子阵进行补偿,每一个子阵的累积误差都较小,从而实现较好的成像效果；同时本发明提出的补偿方案可以解决以下问题：由于收发通道天线方向图的影响,某一对特定的收发通道仅能作用于有限的区域,仅需保证子阵中的天线能作用于补偿点附近的区域即可实现较好的补偿效果。(The invention discloses a cylindrical aperture MIMO array antenna, an imaging method and a compensation method, wherein an MIMO multi-sub-array imaging system can save array elements, is convenient to process, and a cylindrical array can obtain a better imaging effect; by combining with the compensation scheme provided by the invention, the wave path difference between the actual transceiving position and the equivalent position of the channel can be well compensated, so that a good three-dimensional imaging effect is obtained, and the method is suitable for millimeter wave human body security inspection imaging; when the array aperture is large, each subarray is compensated according to the scheme provided by the invention, and the accumulated error of each subarray is small, so that a good imaging effect is realized; meanwhile, the compensation scheme provided by the invention can solve the following problems: due to the influence of the antenna directional diagram of the transmitting-receiving channel, a certain pair of specific transmitting-receiving channels can only act on a limited area, and the good compensation effect can be realized only by ensuring that the antennas in the subarray can act on the area near the compensation point.)

1. A cylindrical aperture multi-subarray MIMO array antenna, wherein transmit antennas TX and receive antennas RX are distributed over a cylindrical arc, wherein: the transmitting antennas TX are uniformly distributed on the arc lines of the cylindrical arc surface at equal angular intervals; the receiving antennas RX are uniformly distributed on the equally spaced bus of the cylindrical cambered surface; the receiving antennas RX on two adjacent bus bars and the transmitting antennas TX on two adjacent arc lines between the two bus bars form an antenna subarray; when the MIMO array antenna works, each subarray scans and images a target in sequence in a time-sharing mode.

2. An imaging method of the cylindrical aperture multi-subarray MIMO array antenna of claim 1, wherein for each antenna subarray, all transmit antennas TX transmit radio frequency signals of a certain frequency band, and all receive antennas RX receive echo signals reflected by a target at the same time; any transmitting antenna TX and a receiving antenna RX in the sub-array form a receiverA pair of transmit antennas; in a standard cylindrical coordinate system, the position of a transmitting antenna TX in a transmitting-receiving antenna pair is expressed as (R, theta)_T,z_T) The RX position of the receiving antenna is represented as (R, θ)_R,z_R) Then its equivalent phase center position EX is expressed as:

if the radius of the cylinder where the arc surface of the cylinder is located is R, the coordinate of the cylinder is expressed as follows under a rectangular coordinate system:

(x_c,y_c,z_c)＝(Rcosθ_c,Rsinθ_c,z_c)；

and equivalently considering the plane where the equivalent phase centers of all the transceiving antenna pairs in the antenna subarray are located as a plane array antenna, and performing imaging calculation by using a plane array antenna imaging algorithm.

3. The method for imaging a cylindrical aperture multi-subarray MIMO array antenna of claim 2, wherein the imaging algorithm is an ω k three-dimensional imaging algorithm.

4. A method of compensating for a method of imaging a multiple-subarray MIMO array antenna with cylindrical aperture according to claim 2, wherein for any transmit-receive antenna pair in each antenna subarray at the operating frequency f_iThe phases to be compensated are:

wherein R is_com＝R₁+R₂-2R₃；R₁Representing the distance from the transmitting antenna to the focal point of the antenna subarray; r₂Representing the distance from the focusing point to the receiving antenna; r₃And the distance from the focus point to the position of the equivalent phase center array element corresponding to the transmitting and receiving antenna is represented.

Technical Field

The invention belongs to the technical field of security inspection, and particularly relates to a cylindrical aperture MIMO array antenna, an imaging method and a compensation method.

Background

The security inspection problem in public places also brings about wide attention to the society and academia, and higher requirements are also put forward on the characteristics of accuracy, instantaneity, intellectualization and the like of a security inspection system.

Human body security inspection has been faced with some technical difficulties, for example, traditional security inspection devices, such as metal detectors and X-ray imaging devices. The metal detector can detect metal prohibited articles carried by a human body, but can not detect nonmetal prohibited articles such as a ceramic knife, a plastic bomb, a powder bomb and the like, and can not distinguish the types of the prohibited articles step by step and realize accurate positioning; although the X-ray imaging device can perform high-resolution imaging on the human body carrying hidden objects, the X-ray has ionization property and is not suitable for rapid high-resolution human body security inspection imaging.

The millimeter wave is used for security inspection imaging, which is a novel security inspection technology appearing in recent years, and has the advantages of high safety, good reliability, difference in electromagnetic scattering characteristics of different materials and the like, and the millimeter wave security inspection imaging method becomes the mainstream development direction of the human body security inspection technology at present.

At present, some millimeter wave security inspection imaging systems mainstream in the world still have problems to be solved urgently: such as the Provision series platform of the U.S. L3 company, which requires mechanical scanning, the imaging speed is slow; the QPS system of the German Rohde & Schwarz company has higher cost and long signal processing time; eqo of Smith company needs to be detected to rotate for a circle in front of an imaging system, has low imaging speed and is difficult to meet the domestic requirement for high-throughput quick security inspection.

Disclosure of Invention

In view of the above, the present invention provides a cylindrical aperture MIMO array antenna, an imaging method and a compensation method, which can save the number of array elements and facilitate processing; the compensation method can compensate the accumulated error of each subarray, thereby realizing better imaging effect.

A cylindrical aperture multi-subarray MIMO array antenna, the transmit antennas TX and receive antennas RX being distributed over a cylindrical arc, wherein: the transmitting antennas TX are uniformly distributed on the arc lines of the cylindrical arc surface at equal angular intervals; the receiving antennas RX are uniformly distributed on the equally spaced bus of the cylindrical cambered surface; the receiving antennas RX on two adjacent bus bars and the transmitting antennas TX on two adjacent arc lines between the two bus bars form an antenna subarray; when the MIMO array antenna works, each subarray scans and images a target in sequence in a time-sharing mode.

An imaging method of a cylindrical aperture multi-subarray MIMO array antenna is characterized in that for each antenna subarray, all transmitting antennas TX transmit radio frequency signals of a certain specific frequency band, and all receiving antennas RX receive echo signals reflected by a target at the same time; any one transmitting antenna TX and one receiving antenna RX in the subarray form a transmitting-receiving antenna pair; in a standard cylindrical coordinate system, the position of a transmitting antenna TX in a transmitting-receiving antenna pair is expressed as (R, theta)_T,z_T) The RX position of the receiving antenna is represented as (R, θ)_R,z_R) Then its equivalent phase center position EX is expressed as:

if the radius of the cylinder where the arc surface of the cylinder is located is R, the coordinate of the cylinder is expressed as follows under a rectangular coordinate system:

(x_c,y_c,z_c)＝(Rcosθ_c,Rsinθ_c,z_c)；

and equivalently considering the plane where the equivalent phase centers of all the transceiving antenna pairs in the antenna subarray are located as a plane array antenna, and performing imaging calculation by using a plane array antenna imaging algorithm.

Preferably, the imaging algorithm is an ω k three-dimensional imaging algorithm.

A compensation method of an imaging method of a cylindrical aperture multi-subarray MIMO array antenna aims at any transmitting-receiving antenna pair in each antenna subarray and is at a working frequency f_iThe phases to be compensated are:

wherein R is_com＝R₁+R₂-2R₃；R₁Representing the distance from the transmitting antenna to the focal point of the antenna subarray; r₂Representing the distance from the focusing point to the receiving antenna; r₃And the distance from the focus point to the position of the equivalent phase center array element corresponding to the transmitting and receiving antenna is represented.

The invention has the following beneficial effects:

the MIMO multi-subarray imaging system provided by the invention can save array elements, is convenient to process, and can obtain a better imaging effect by the cylindrical surface array; the compensation scheme provided by the invention is combined, the wave path difference between the actual receiving and sending positions of the channels and the equivalent positions can be well compensated, so that a good three-dimensional imaging effect is obtained, and the method is suitable for millimeter wave human body security inspection imaging.

The compensation scheme provided by the invention aims at the problem that when the array aperture surface is large, the accumulated error of non-compensation points is large. When the array aperture is large, each subarray is compensated according to the scheme provided by the invention, the accumulated error of each subarray is small, and therefore, a good imaging effect is achieved.

Meanwhile, the compensation scheme provided by the invention can solve the following problems: a particular transceiver channel pair can only operate in a limited area due to the effects of the transceiver channel antenna pattern. And a better compensation effect can be realized only by ensuring that the antenna in the subarray can act on an area near the compensation point.

After the cylindrical aperture MIMO near-field imaging system, the array compensation scheme and the rapid imaging algorithm are combined, the advantages of high distance, azimuth direction and altitude direction resolution can be achieved, the arrangement is easy, the applicability of the application environment is high, rapid human body security inspection can be realized, and the system and the method can be applied to human body security inspection in the environments of airports, high-flux subways, railway stations and the like.

Drawings

FIG. 1 is a schematic block diagram of a multi-subarray near field compensation method of a cylindrical aperture MIMO array according to the present invention;

fig. 2 is a schematic diagram of an overall structure of a cylindrical aperture MIMO array multi-subarray system according to an embodiment of the present invention;

FIG. 3 is a schematic diagram for explaining the phase accumulated error of the present invention;

fig. 4(a) is a schematic diagram of an error compared with that of a conventional central compensation, and (b) is a schematic diagram of an error of near-field compensation of multiple sub-arrays of a cylindrical aperture MIMO array in an embodiment of the present invention;

fig. 5(a), (b) and (c) illustrate the influence of the cylindrical aperture MIMO array multi-subarray near field compensation method on the result of the fast imaging algorithm. Wherein, 5(a) is an imaging result obtained by adopting an omega k (wave number domain algorithm) algorithm after adopting a traditional near field compensation method; 5(b) adopting a multi-subarray near field compensation method and then adopting an imaging result of an omega k (wave number domain algorithm) algorithm; and 5(c) is the imaging result of the standard BP algorithm (no compensation is needed).

Detailed Description

The invention is described in detail below by way of example with reference to the accompanying drawings.

As shown in fig. 2, a solid circle represents a transmitting antenna TX, a hollow circle represents a receiving antenna RX, and the transmitting antennas TX are uniformly distributed on an arc line with equal angular intervals in the cylindrical aperture; the receiving antennas RX are uniformly distributed on the equally spaced buses of the cylindrical aperture; the receiving antennas RX on two adjacent bus bars and the transmitting antennas TX on two adjacent arcs between the two bus bars form an antenna sub-array. In this embodiment, each sub-array is composed of 8 transmitting (4 up and 4 down) antennas and 8 receiving (4 up and 4 down) antennas.

When the MIMO array antenna works, each subarray scans the target in sequence in timeLike until all sub-arrays are traversed. For each subarray, all transmitting antennas TX transmit radio-frequency signals of a certain specific frequency band, and all receiving antennas RX in the subarray receive echo signals reflected by a target at the same time as the imaging range belongs to the near field range; any one transmitting antenna TX and one receiving antenna RX in the subarray form a transmitting-receiving antenna pair; the transmitting and receiving process of the transmitting and receiving antenna pair can be equivalent to transmitting and receiving signals from a certain specific position, as shown in the right schematic diagram of fig. 2, and in a standard cylindrical coordinate system, the TX position of a certain transmitting antenna in a certain subarray can be represented as (R, θ)_T,z_T) The RX position of a certain receiving antenna can be expressed as (R, θ)_R,z_R) Then its equivalent phase center position EX can be expressed as:

assuming that the radius of the cylinder is R, the coordinate under the rectangular coordinate system is expressed as:

(x_c,y_c,z_c)＝(Rcosθ_c,Rsinθ_c,z_c)

all antenna pairs in the sub-array can be equivalent to an antenna array of a plane full array, so that in the imaging algorithm, a traditional plane antenna array algorithm, such as a commonly used omega-k three-dimensional imaging algorithm (wave number domain algorithm), can be adopted. The adoption of the arc form can enable the beam direction of the antenna to face the imaging area, and the problem of image quality deterioration caused by gain reduction in the non-line-of-sight direction of the antenna is solved.

However, a phase error exists between a full array equivalent to the MIMO array and an actual array topology, and generally, a central compensation mode is required to compensate the entire array. When the array aperture is large, the accumulated error of the uncompensated points is large, and the imaging quality is seriously influenced. Meanwhile, due to the influence of the antenna pattern of the transceiving channel, a certain pair of specific transceiving channels can only act on a limited area, and the central compensation mode is possibly out of the acting range of the transceiving channel.

The invention therefore also provides a phase compensation method.

The phase position of compensation needed by the cylindrical aperture multi-subarray MIMO array is determined by the following scheme: the phase needing to be compensated is obtained by calculating the wave path difference generated by the transmitting antenna to the sub-array focusing point and then to the receiving antenna and calculating the wave path difference generated by the transmitting and receiving antenna equivalent phase center guide sub-array focusing point, and the difference of the two wave path differences is solved and is used for compensating the baseband signal.

The invention realizes the fast high-resolution imaging of human body by the following steps, and the scheme flow is shown in figure 1:

first, the position (x) of a certain sub-array focus point is determined₀,y₀,z₀) And assuming the position of the transmitting antenna in one of the transmitting and receiving antenna pairs is (x)₁,y₁,z₁) The position of the receiving antenna is (x)₂,y₂,z₂) The position of the corresponding equivalent phase center array element is set as (x)₃,y₃,z₃) Then the lengths of the following segments of the path can be calculated: transmitting antenna-to-focal point distance:

focal point to receive antenna distance:

focusing point to the position of the equivalent phase center array element corresponding to the receiving and transmitting antenna:

the distance to be compensated is then: r_com＝R₁+R₂-2R₃. In order to obtain a certain distance resolution of the imaging result, the system of the invention adopts a broadband radio frequency signal. If the N frequencies corresponding to the receiving and transmitting radio frequency signals of the system form a sequence: f ═ f₁,f₂,…,f_NIf the frequency sequence is an arithmetic sequence, the system bandwidth is B ═ f_N-f₁The light velocity in vacuum is c, the distance resolution is

Taking the equidistant step frequency signal as an example, if the frequency step interval is Δ f, the unambiguous distance from the classical range imaging algorithm is

I.e. the results of classical range-image imaging algorithms only apply in the range of unambiguous distances. Under the condition that the conditions allow, if the resolution is certain (the system bandwidth is certain), it is guaranteed that the larger the number of frequency points is, the better the frequency points are, the larger the non-fuzzy distance is realized, and the compensation result and the imaging effect of the algorithm are guaranteed.

For a certain frequency f in the sequence_iThe phase to be compensated at this frequency is:

it should be noted that the focusing centers of different sub-arrays can be divided in advance, and are generally arranged on the symmetry axis of the cylindrical array. The phase distribution of different subarrays at different focal points and different frequencies can be calculated in advance and stored in corresponding equipment. When applied, the data can be directly read from the corresponding equipment, and not calculated in real time.

Traversing a certain transmitting-receiving antenna pair, transmitting and receiving all frequency signals f in radio frequency signal sequence_iFor all f_iAnd focus point (x)₀,y₀,z₀) And calculating the phase to be compensated at the frequency according to a compensation phase calculation principle.

And traversing all the transmitting and receiving channels in the same subarray to complete the calculation of the compensation phases required by all the channels in the same subarray.

And traversing all different sub-arrays, and completely calculating the compensation phases required by all channels in all the sub-arrays.

And (3) compensating the acquired baseband signal by using the compensation phase, and obtaining a three-dimensional imaging result by using a rapid three-dimensional imaging algorithm (omega-k algorithm), thereby realizing high-resolution three-dimensional imaging of each region in each part of the human body.

Under the near-field security inspection imaging scene, the horizontal dimension and the vertical dimension of three-dimensional imaging can reach higher resolution by ensuring larger aperture of the array surface and more sub-arrays, and higher distance dimension resolution is realized, so that three-dimensional high-resolution imaging of one area of a human body is realized.

In summary, the three-dimensional high-resolution fast imaging of the target scene is realized by combining the near-field compensation algorithm for the cylindrical aperture MIMO array with the ω k algorithm (wave number domain algorithm).

Some embodiments of the present invention will be described in detail below, and the embodiments described by referring to the drawings are only exemplary and are only used for explaining the present invention, and are not to be construed as limiting the present invention.