CN106093898A - A kind of MIMO array calibration steps of subregion formula - Google Patents

Abstract

The invention discloses the MIMO array calibration steps of a kind of subregion formula, process: according to the layout scenarios of MIMO array, set up three-dimensional system of coordinate, determine each transmitting antenna and the coordinate position of reception antenna；According to bistatic radar equivalent theory and each transmitting antenna and the coordinate position of reception antenna, determine the corresponding relation between every its corresponding displaced phase center of a pair dual-mode antenna, obtain displaced phase center array and displaced phase center array co-ordinates position；With distance R and the dual-mode antenna beam angle of displaced phase center array plane, displaced phase center array is carried out region division with the corresponding relation of dual-mode antenna, metal calibration ball according to displaced phase center array；Respectively the displaced phase center array of regional is carried out phase calibration process.By array is carried out multidomain treat-ment, repeatedly calibrate, it is possible in the case of near field antenna wave beam is narrower, complete array calibration work, it is achieved high-quality array image-forming.

Description

A kind of MIMO array calibration steps of subregion formula

Technical field

The present invention relates to the MIMO array calibration steps of a kind of subregion formula.

Background technology

MIMO array imaging technique has important using value at aspects such as safety check, nondestructive inspection and geology detectings.Battle array Before being listed in imaging processing, it is necessary first to each passage is carried out phase alignment, calibration main cause be each passage hardware, Cable, antenna performance equiphase are inconsistent, and channel phases calibration is the key of array image-forming, the most typically uses metal cylinder Or metal ball once can obtain calibration data as calibrating device, test, this method is applicable to far field calibration, at near-field array During imaging (especially under dark room conditions, region is less), if antenna beam is narrower, dual-mode antenna overlay area is limited, is difficult to Ensure that all dual-mode antennas all can cover calibration target, and therefore the method has limitation in disposable calibration test process.

MIMO array imaging technique has a high potential in terms of imaging, and it is usually by multiple transmitter units and receives unit structure Become, use the working forms of on-off control, have and only a pair dual-mode antenna work, therefore, it is possible to effectively suppress antenna every time Between coupling, produce the virtual array unit far more than actual antennas number, thus greatly save the hardware of array Cost and construction difficulty.Range migration algorithm (RMA) is a kind of more accurate scattering imaging algorithm, can apply to Multi probe Array is scattering into picture.The principle of lower surface analysis list station equivalence.

As it is shown in figure 1, bistatic radar equivalent theory: transmitting antenna and the reception antenna with setpoint distance are equivalent to transmitting-receiving The list station situation of antenna center between the transmit antennas and the receive antennas；

If being carved with a pair dual-mode antenna work time a certain, the target of irradiation is p, and transmitter unit launches electromagnetic wave route viaArrive target p, the route via again of the scatter echo after pReceived unit to receive；

According to single station equivalent theory, displaced phase center is at transmitter unit and the straight line receiving unit placeOn；

Transmitter unit, reception unit and target p constitute a triangle, and displaced phase center is simultaneously at this triangle angle On the angular bisector of p, the most described angular bisector withIntersection point be required displaced phase center；

If displaced phase center vector isAccording to triangle geometry corresponding relation, thenWithBetween just like ShiShimonoseki System

$p\stackrel{\→}{o}s=\frac{\stackrel{\→}{p}c}{(\frac{\left|r\stackrel{\→}{r}x\right|}{\left|r\stackrel{\→}{t}x\right|}+1)}---\left(1\right).$

In actual application, displaced phase center is considered in transmitter unit and the center receiving unit, i.e. When target range Transmit-Receive Unit farther out time, formula (1) approximation is set up, and near field when displaced phase center error is bigger, then Need to carry out phase calibration process；Definition displaced phase center error is

$err=\left|p\stackrel{\→}{o}s\right|-\frac{\left|\stackrel{\→}{p}c\right|}{2}---\left(2\right).$

In actual application, MIMO array, in addition to there is above-mentioned displaced phase center error, there is also because of microwave device, opens Close, antenna inconsistent and the hardware phase error that causes, if these errors were not removed before array image-forming is tested Calibration process, it will the target phase information making array received is disorderly, thus causes image normally to focus on.

The calibration steps document of the most domestic MIMO array about near-field scattering imaging is less.When Multi probe array is answered With during with Near-Field Radar Imaging, domestic and international researcher typically uses the following two kinds measure:

One is reduction displaced phase center error from the design of array, and suitable antenna array layout can also effectively drop The displaced phase center error of low array, improves image quality.As realized same virtual equivalent unit, the equivalence of rectangular array Phase center error just little than cross array.This method shortcoming is to require a high expenditure of energy in array design, and And reasonably array design also can only reduce equivalent phase error to a certain extent, hardware phase error then must be by material object Test is calibrated.

Two is to use metal cylinder or the calibration steps of metal ball, dead ahead one spacing of the heart the most in an array Place thin cylinder or the tinsel of a metal from place, its schematic diagram is as shown in Figure 2.

In actual application, first measure metal cylinder or tinsel corresponding array received echo, be designated as E_pole, for one For dimension array image-forming, imaging plane is xz face, and therefore metal cylinder or tinsel are considered as an ideal point target, its phase The displaced phase center array received echo answered can calculate by the way of Theoretical Calculation, is designated as E_theory.Then compensate Matrix can be expressed as E_theory/E_pole, this matrix is relevant with frequency and displaced phase center position.

The greatest problem that the method exists is: be not suitable for near-field array calibration under particular case.Under the conditions of near-field test, If antenna beam is narrower, the antenna of array edges will be difficult to receive the useful signal of calibration target, thus causes sky, edge Line to channel error be not calibrated removal, have impact on imaging effect.

Summary of the invention

The purpose of the present invention is contemplated to solve the problem that conventional calibration method exists under near-field test environment, it is provided that one Plant the MIMO array calibration steps of subregion formula, by array is carried out multidomain treat-ment, repeatedly calibration operation, it is possible in sky, near field Array calibration work is completed, it is achieved high-quality array image-forming in the case of line wave beam is narrower.

To achieve these goals, the present invention adopts the following technical scheme that

A kind of MIMO array calibration steps of subregion formula, process is as follows:

Step (1): according to the layout scenarios of MIMO array, set up three-dimensional system of coordinate, determines each transmitting antenna and reception The coordinate position of antenna；

Step (2): according to bistatic radar equivalent theory and each transmitting antenna and the coordinate position of reception antenna, determines every Corresponding relation between a pair its corresponding displaced phase center of dual-mode antenna, obtains displaced phase center array and equivalence phase Position center array coordinate position；A metal calibration is placed at distance R at the center of displaced phase center array place plane Ball；

Step (3): according to displaced phase center array and the corresponding relation of dual-mode antenna, metal calibration ball and equivalent phase Distance R and the dual-mode antenna beam angle of center array plane carry out region division to displaced phase center array；

Step (4): respectively the displaced phase center array of regional is carried out phase calibration process.

Described step (2) metal calibration ball is perpendicular to equivalence with the line at the center of displaced phase center array place plane Phase center array place plane.

Described step (4) comprises the steps:

Step (4-1): when using displaced phase center array to carry out data acquisition, for ith zone the l equivalence The test echo-signal that the corresponding reception antenna of phase center unit (x (il), y (il), 0) receives is designated as S_measure(il,k)；

The span of i is 1-m, and wherein, m represents the number to the region that displaced phase center array divides；

The span of l is 1-n, and wherein, n represents the number of the displaced phase center unit inside each region；

Step (4-2): calculate the l displaced phase center unit of ith zone (x (il), y (il), 0) and receive accordingly Theoretical echo-signal S that antenna receives_{mo_sta}(il,k)；

Step (4-3): according to test echo-signal S of step (4-1)_measure(il, k) theory with step (4-2) is returned Ripple signal S_{mo_sta}(il, k), calculate displaced phase center array the l displaced phase center unit of ith zone (x (il), Y (il), 0) corresponding phase compensation matrix F actor (il, k)；

Step (4-4): the corresponding reception antenna of the l displaced phase center unit of ith zone (x (il), y (il), 0) The test echo-signal received is designated as S_measure(il k) is multiplied by the l displaced phase center list of ith zone of step (4-3) (il k), obtains in the l equivalent phase of ith zone corresponding phase compensation matrix F actor of unit (x (il), y (il), 0) Echo data after heart unit (x (il), y (il), 0) phase alignment, completes the l displaced phase center unit in the i-th region (x (l), y (l), 0) phase alignment；

Repeat step (4-1)-step (4-4), until completing the phase to displaced phase center unit all of in the i-th region Position calibration；

In like manner, the calibration process to all regions is completed.

The layout scenarios of the MIMO array of described step (1) including: cross battle array, rectangle battle array, circle or other forms Irregular array.

The principle that the region of described step (3) divides is:

When metal calibration ball distance displaced phase center array plane is R, change X-direction and the Y side of metal calibration ball To coordinate position, make wave beam can cover metal calibration ball dual-mode antenna number meet set threshold value, then can cover with wave beam The region at the dual-mode antenna correspondence displaced phase center array place of lid metal calibration ball is first area, in like manner finds next district Territory, until all displaced phase center arrays are divided.

In the case of region is the biggest, ensure that the main beam of the dual-mode antenna in each region all can cover metal calibration Ball, obtains some regions.

The step of described step (4-1) is:

Displaced phase center array center position according to ith zone determines metal calibration ball position coordinates (x_i,y_i, R)；Carry out the actual alignment test of metal calibration ball, obtain ith zone the l displaced phase center unit (x (il), y (il), 0) the test echo-signal that corresponding reception antenna receives, is designated as S_measure(il,k)。

The step of described step (4-2) is:

According to formula (3) calculate displaced phase center array singly stand equivalence imaging time, reception antenna receive theory return Ripple signal S_{mo_sta}(il,k)；

$S_{mo\_sta}(il,k)=e^{-j\·2k\·\sqrt{{\left(x\right(l)-x_i)}^2+{\left(y\right(l)-y_i)}^2+R^2}}---\left(3\right)$

Wherein k=2 π f/c is for launching signal wave number, and f represents that operating frequency, c represent electromagnetic wave propagation speed in a vacuum Degree.

The step of described step (4-3) is:

Make theoretical echo-signal S that the reception antenna of step (4-2) receives_{mo_sta}(il, k) reception than upper step (4-1) Test echo-signal S that antenna receives_measure(il k), obtains phase compensation matrix F actor of displaced phase center array (il,k)。

The formula of described step (4-3) is:

$Factor(il,k)=\frac{S_{mo\_sta}(il,k)}{S_{measure}(il,k)}---\left(4\right).$

Beneficial effects of the present invention:

The array calibration method of 1 present invention is applicable to ultra broadband, narrow beam, near field, far field MIMO imaging；

2 present invention need according to dual-mode antenna position, displaced phase center array, antenna beamwidth, calibration ball position Array is carried out subarea processing.

3 present invention have huge advantage at aspects such as high-resolution imaging and saving hardware resource costs, use the present invention to enter The MIMO array of row calibration effectively can carry out one-dimensional, two-dimentional or three-dimensional imaging to target.

Accompanying drawing explanation

Fig. 1 is displaced phase center schematic diagram；

Fig. 2 is the phase compensation schematic diagram of tradition Multi probe array image-forming；

Fig. 3 is cross MIMO array；

Fig. 4 is territory, array partition schematic diagram；

Fig. 5 is equivalent unit and dual-mode antenna corresponding relation schematic diagram；

Fig. 6 is that calibration ball puts schematic diagram；

Fig. 7 is the MIMO array calibration flow chart of subregion formula.

Detailed description of the invention

The invention will be further described with embodiment below in conjunction with the accompanying drawings.

First according to MIMO array distribution form, its displaced phase center cell array is determined, for vivider explanation The calibrating principle of the present invention, as a example by simple cross MIMO array, its array layout form is as it is shown on figure 3, adjacent transmission The interval of antenna and reception antenna is 2 Δs, and Δ is generally the half of array operation wavelength.It is corresponding that Fig. 4 gives this array Displaced phase center array, it is assumed that under the conditions of Near-Field Radar Imaging, the beam angle of antenna is limited, such as equivalent unit pair in region 1 The dual-mode antenna wave beam answered can not cover the target to be measured maybe can not being completely covered in region 2,3,4, it is assumed that according to antenna beam Width is divided into 4 parts displaced phase center array.

As a example by region 1, find out its equivalent unit and dual-mode antenna corresponding relation, as it is shown in figure 5, equivalent unit is positioned at receipts Send out the midpoint of antenna, it is seen that equivalent unit is spaced apart Δ.The center position coordinates of displaced phase center array in zoning (x₀,y₀) (this example being (-4 Δs, 4 Δs)), if calibration ball is positioned at displaced phase center array center, front distance R (typically takes 0.5 Between 1.0m) place, under three-dimensional system of coordinate, the position coordinates of calibration ball is (x₀,y₀, R) (this example is (-4 Δs, 4 Δs, R), As shown in Figure 6.

When using displaced phase center array shown in Fig. 2 to carry out data acquisition, for the n-th displaced phase center unit (x (n), y (n), 0) its corresponding reception antenna receives echo-signal (not considering amplitude) and is designated as S_measure(n, k), this equivalence phase Theoretical echo corresponding to center, position is approximately

$S_{mo\_sta}(n,k)=e^{-j\·2k\·\sqrt{{\left(x\right(n)-x_0)}^2+{\left(y\right(n)-y_0)}^2+R^2}}---\left(3\right)$

Wherein k=2 π f/c is for launching signal wave number, and f represents that operating frequency, c represent electromagnetic wave propagation speed in a vacuum Degree.

If calibration matrix is that (n k), defines Factor

$Factor(n,k)=\frac{S_{mo\_sta}(n,k)}{S_{measure}(n,k)}---\left(4\right)$

(n, k) can be complete only the target echo data that equivalent phase unit each in region 1 is corresponding need to be multiplied by Factor Become phase alignment in region 1.In like manner, in other regions, calibration ball position coordinates need to be redefined, according in equivalent phase The corresponding relation of the heart and dual-mode antenna, completes phase alignment in remaining area according to (4) formula calibration factor.

As it is shown in fig. 7, the MIMO array calibration steps of a kind of subregion formula, process is as follows:

Step (1): first, according to the layout scenarios of MIMO, sets up coordinate system and determines each transmitting antenna and reception antenna Coordinate position；

Step (2): according to bistatic radar equivalent theory and the result of step (1), determine every a pair dual-mode antenna and phase thereof The corresponding relation of the displaced phase center answered, obtains displaced phase center array and coordinate position thereof；As shown in Figure 1；

Step (3): according to displaced phase center array and the corresponding relation of dual-mode antenna, metal calibration ball and equivalent phase Distance R of center array plane and antenna beamwidth carry out region division to displaced phase center array, and it is former that region divides It is then that the main beam ensureing the dual-mode antenna in each region in the case of region is as far as possible big all can cover metal ball, if obtaining Dry region；

Step (4): respectively the displaced phase center array of regional is carried out phase calibration process.According in region 1 Displaced phase center array center position determines calibration ball position coordinates (x₀,y₀, R).Carry out actual test, obtain the n-th equivalence The corresponding reception antenna echo-signal (not considering amplitude) of phase center unit (x (n), y (n), 0), is designated as S_measure(n,k)；

Step (5): according to formula (3) calculate MIMO array singly stand equivalence imaging time, reception antenna receive theory return Ripple signal S_{mo_sta}(n,k)；

Step (6): make echo-signal S of step (5)_{mo_sta}(n, k) than echo-signal S of upper step (4)_measure(n, K), i.e. according to formula (4) calculate MIMO phase compensation matrix F actor (n, k)；

Step (7): the phase compensation matrix in MIMO array region 1 has solved complete, uses range migration algorithm to reality Before border target carries out imaging processing, the sampled signal in region 1 is multiplied by the result compensation matrix of step (6), completes in region 1 Array phase is calibrated；

Step (8): according to same principle, respectively to remaining the array calibration process that all regions are similar to.

Although the detailed description of the invention of the present invention is described by the above-mentioned accompanying drawing that combines, but not the present invention is protected model The restriction enclosed, one of ordinary skill in the art should be understood that on the basis of technical scheme, and those skilled in the art are not Need to pay various amendments or deformation that creative work can make still within protection scope of the present invention.

Claims (9)

1. a MIMO array calibration steps for subregion formula, is characterized in that, process is as follows:

Step (1): according to the layout scenarios of MIMO array, set up three-dimensional system of coordinate, determines each transmitting antenna and reception antenna Coordinate position；

Step (2): according to bistatic radar equivalent theory and each transmitting antenna and the coordinate position of reception antenna, determine every a pair Corresponding relation between its corresponding displaced phase center of dual-mode antenna, obtains in displaced phase center array and equivalent phase Heart array co-ordinates position；A metal calibration ball is placed at distance R at the center of displaced phase center array place plane；

Step (3): according to displaced phase center array and the corresponding relation of dual-mode antenna, metal calibration ball and displaced phase center Distance R and the dual-mode antenna beam angle of array plane carry out region division to displaced phase center array；

Step (4): respectively the displaced phase center array of regional is carried out phase calibration process.

The MIMO array calibration steps of a kind of subregion the most as claimed in claim 1 formula, is characterized in that, described step (2) gold The line at the center belonging to calibration ball and displaced phase center array place plane is perpendicular to displaced phase center array place plane.

The MIMO array calibration steps of a kind of subregion the most as claimed in claim 1 formula, is characterized in that, described step (4) is wrapped Include following steps:

Step (4-1): when using displaced phase center array to carry out data acquisition, for the l equivalent phase of ith zone The test echo-signal that the corresponding reception antenna of center cell (x (il), y (il), 0) receives is designated as S_measure(il,k)；

The span of i is 1-m, and wherein, m represents the number to the region that displaced phase center array divides；

The span of l is 1-n, and wherein, n represents the number of the displaced phase center unit inside each region；

Step (4-2): calculate the corresponding reception antenna of the l displaced phase center unit of ith zone (x (il), y (il), 0) Theoretical echo-signal S received_{mo_sta}(il,k)；

Step (4-3): according to test echo-signal S of step (4-1)_measure(il, k) and the theoretical echo-signal of step (4-2) S_{mo_sta}(il, k), calculate displaced phase center array the l displaced phase center unit of ith zone (x (il), y (il), 0) corresponding phase compensation matrix F actor (il, k)；

Step (4-4): the corresponding reception antenna of the l displaced phase center unit of ith zone (x (il), y (il), 0) receives Test echo-signal be designated as S_measure(il k) is multiplied by the l displaced phase center unit (x of ith zone of step (4-3) (il), y (il), 0) (il k), obtains the l displaced phase center list of ith zone to corresponding phase compensation matrix F actor Echo data after unit's (x (il), y (il), 0) phase alignment, completes the l displaced phase center unit (x in the i-th region (l), y (l), 0) phase alignment；

Repeat step (4-1)-step (4-4), until completing the phase place school to displaced phase center unit all of in the i-th region Accurate；

In like manner, the calibration process to all regions is completed.

The MIMO array calibration steps of a kind of subregion the most as claimed in claim 1 formula, is characterized in that, described step (1) The layout scenarios of MIMO array includes: cross battle array, rectangle battle array, circle or the irregular array of other forms.

The MIMO array calibration steps of a kind of subregion the most as claimed in claim 1 formula, is characterized in that, described step (3) The principle that region divides is:

When metal calibration ball distance displaced phase center array plane is R, change the X-direction of metal calibration ball and Y-direction Coordinate position, make wave beam can cover metal calibration ball dual-mode antenna number meet set threshold value, then can cover gold with wave beam The region at the dual-mode antenna correspondence displaced phase center array place belonging to calibration ball is first area, in like manner finds next region, Until all displaced phase center arrays are divided.

The MIMO array calibration steps of a kind of subregion the most as claimed in claim 3 formula, is characterized in that, described step (4-1) Step be:

Displaced phase center array center position according to ith zone determines metal calibration ball position coordinates (x_i,y_i, R)；Enter The actual alignment test of row metal calibration ball, obtains the l displaced phase center unit of ith zone (x (il), y (il), 0) The test echo-signal that corresponding reception antenna receives, is designated as S_measure(il,k)。

The MIMO array calibration steps of a kind of subregion the most as claimed in claim 3 formula, is characterized in that, described step (4-2) Step be:

According to formula (3) calculate displaced phase center array singly stand equivalence imaging time, reception antenna receive theoretical echo letter Number S_{mo_sta}(il,k)；

$S_{mo\_sta}(il,k)=e^{-j\·2k\·\sqrt{{\left(x\right(l)-x_i)}^2+{\left(y\right(l)-y_i)}^2+R^2}}---\left(3\right)$

Wherein k=2 π f/c is for launching signal wave number, and f represents that operating frequency, c represent electromagnetic wave spread speed in a vacuum.

The MIMO array calibration steps of a kind of subregion the most as claimed in claim 3 formula, is characterized in that, described step (4-3) Step be: make theoretical echo-signal S that the reception antenna of step (4-2) receives_{mo_sta}(il, k) connecing than upper step (4-1) Receive test echo-signal S that antenna receives_measure(il k), obtains phase compensation matrix F actor of displaced phase center array (il,k)。

The MIMO array calibration steps of a kind of subregion the most as claimed in claim 3 formula, is characterized in that, described step (4-3) Formula be:

$Factor(il,k)=\frac{S_{mo\_sta}(il,k)}{S_{measure}(il,k)}---\left(4\right).$