CN112162251A - Double-scaling antenna radio frequency channel calibration method for millimeter wave security inspection imaging - Google Patents
Double-scaling antenna radio frequency channel calibration method for millimeter wave security inspection imaging Download PDFInfo
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Abstract
The invention relates to the technical field of radio frequency channel calibration, and discloses a double-calibration antenna radio frequency channel calibration method for millimeter wave security check imaging. According to the calibration method for the radio frequency channel of the double calibration antenna for millimeter wave security check imaging, the position coordinates of the calibration antenna do not need to be directly measured, but the position of the calibration antenna is accurately obtained through data statistics and analysis, so that the positioning precision is high, and the requirement of the imaging quality of a corresponding system radio frequency receiving/transmitting channel calibration result can be met.
Description
Technical Field
The invention relates to the technical field of radio frequency channel calibration, in particular to a calibration method of a double-calibration antenna radio frequency channel for millimeter wave security inspection imaging.
Background
An active millimeter wave security imager usually adopts a multi-channel MIMO working mode, as shown in fig. 1, so as to reduce the hardware cost of the system and improve the imaging speed of the system. In order to improve the imaging performance of the system, the amplitude-frequency characteristic, the phase-frequency characteristic and the electrical length among the radio frequency receiving/transmitting channels need to be calibrated before imaging. In addition, according to the requirements related to the imaging algorithm, the phase center of any transmitting and receiving antenna in the antenna array should be used as a zero phase reference point for the detection signal of the target to be detected. As shown in fig. 2, the calibration horn antenna is placed in the far field of the rf receiving/transmitting antenna array, or a sufficient distance is ensured so that the calibration horn antenna is located in the main lobe beam irradiation range of all the rf receiving/transmitting antennas, calibration data of all channels can be quickly obtained through one-time calibration measurement, calibration efficiency is improved, and mass production of products is facilitated.
However, the method needs to accurately measure the position coordinates of the calibration horn antenna relative to the radio frequency receiving/transmitting antenna array, and for the millimeter wave band, the millimeter positioning error will have a great influence on the system calibration precision, thereby affecting the imaging effect.
Therefore, it is desirable to provide a new technical solution to solve the above problems.
Disclosure of Invention
The invention aims to overcome the problem of poor imaging effect of radio frequency channel calibration in the prior art, and provides a calibration method of a double-calibration antenna radio frequency channel for millimeter wave security inspection imaging.
In order to achieve the above object, the present invention provides a calibration method for a dual-calibration antenna radio frequency channel for millimeter wave security inspection imaging, which specifically includes the following steps: s1, providing two external calibration antennas, specifically a first calibration antenna and a second calibration antenna, and respectively obtaining corresponding calibration test values, namely receiving calibration signals of all receiving antennas relative to the first calibration antenna and the second calibration antenna; s2, carrying out mutual calibration and correlation analysis processing on the two groups of calibration test values to obtain true values of coordinates of two external calibration antennas; and S3, calibrating the radio frequency channel by using the truth values of the two external calibration antenna coordinates.
Preferably, the test values of the receiving calibration of the first calibration antenna and the second calibration antenna in S1 are respectively:
wherein, L1rlScaling the length of the transmission path, L, for a first scaled antennarefIs the length of the reference path, LRx(nr)For the length of each receive channel, L1Rx(nr),calIs the true value of the spatial distance from the first antenna to each receiving antenna, S1Rx(nr,f)A phase relative value of "first calibration antenna + nth receiving antenna path" with respect to the reference path; l2rlScaling the length of the transmission path, L, for a second scaled antennarefIs the length of the reference path, LRx(nr)For the length of each receive channel, L2Rx(nr),calTrue values of the spatial distances from the second calibration antenna to the respective receiving antennas, S2Rx(nr,f)A phase relative value of "second scaling antenna + nth receiving antenna path" with respect to the reference path; λ is the wavelength corresponding to the working frequency point, and j is the complex imaginary part indicator.
Preferably, the S2 specifically includes the following steps: s21, acquiring coordinate ranges of the first calibration antenna and the second calibration antenna, respectively taking a point in the coordinate ranges of the first calibration antenna and the second calibration antenna, and calculating the distance from the point to each receiving antenna;
s22, combining the points taken on the first calibration antenna and the second calibration antenna, pre-calibrating the receiving calibration signals in the formulas (1) and (2) to obtain receiving pre-calibration signals; and
s23, performing mathematical operation on the received pre-calibration signals corresponding to the points taken by the first calibration antenna and the second calibration antenna to obtain true values of the coordinates of the first calibration antenna and the second calibration antenna.
Preferably, the coordinate ranges of the first calibration antenna and the second calibration antenna in S21 are obtained through visual measurement or ruler measurement, and the coordinates of the two external calibration antennas and the distances from the point selected in the coordinate ranges to the receiving antennas are specifically:
first calibration antenna: x1cal∈(X11,X1Nx1)Y1cal∈(Y11,Y1Ny1)Z1cal∈(Z11,Z1Nz1)
A second scaling antenna: x2cal∈(X21,X2Nx2)Y2cal∈(Y21,Y2Ny2)Z2cal∈(Z21,Z2Nz2) Wherein, (X1)cal,Y1cal,Z1cal) I.e. the true value of the coordinates of the first calibration antenna, (X2)cal,Y2cal,Z2cal) The true value of the coordinate of the second calibration antenna is obtained; the coordinate of the point selected on the first calibration antenna is marked as (X1)nx1,Y1ny1,Z1nz1) The coordinate of the point selected on the second scaled antenna is marked as (X2)nx2,Y2ny2,Z2nz2) Then the distance from the selected point on the first calibration antenna to each receiving antenna is L1Rx(nr),(X1nx1,Y1ny1,Z1nz1)The distance from the selected point on the second scaling antenna to each receiving antenna is L2Rx(nr),(X2nx2,Y2ny2,Z2nz2)。
Preferably, the distances L1 from the selected point on the first calibration antenna to the receiving antennas are used for the points on the first calibration antenna and the second calibration antenna in S22Rx(nr),(X1nx1,Y1ny1,Z1nz1)Distance L2 from the selected point on the second scaled antenna to each of the receiving antennasRx(nr),(X2nx2,Y2ny2,Z2nz2)，Pre-calibrating the receiving calibration signals in the formula (1) and the formula (2), and obtaining receiving pre-calibration signals respectively as follows:
preferably, in S23, the phase difference of the received pre-calibration signal obtained by using the points respectively taken by the first calibration antenna and the second calibration antenna through mathematical operation is specifically:
wherein,
has a phase value of
Show to make
Summing absolute values of all receiving antennas and all test frequency points;
traverse first scaled antenna position (X1)nx1,Y1ny1,Z1nz1) And a second scaled antenna position (X2)nx2,Y2ny2,Z2nz2) To make
Taking the minimum value (X1)nx1,Y1ny1,Z1nz1) And (X2)nx2,Y2ny2,Z2nz2) I.e. (X1)cal,Y1cal,Z1cal) And (X2)cal,Y2cal,Z2cal) True value of (1).
Preferably, the S3 specifically includes the following steps: s31, obtaining the relative phase value of the link from each receiving antenna to the reference path and the relative phase value of the link from each transmitting antenna to the calibration receiving to the reference path; s32, measuring scattering measurement values of all the transmitting-receiving antenna pairs relative to a target point, and completing pre-calibration of a phase value of a link in practical application and a phase value in measurement; s33, obtaining the phase residual quantity in S32 by using background calibration; and S34, supplementing the phase residual quantity to realize the final calibration of the radio frequency channel.
Preferably, in S31, the scaling the relative phase value of the link to the reference path transmitted to each receiving antenna and the relative phase value of the link to the scaled receiving antenna to the reference path specifically include:
wherein L isrlFor calibrating the length of the transmission path (including external calibration cable and calibration antenna), LrefIs the length of the reference path, LRx(nr)For the length of each receiving channel, LRx(nr),calFor scaling the spatial distance of the antenna to each receiving antenna, SRx(nr,f)To scale the relative phase values of the links transmitted to each receive antenna with respect to a reference path; l istlFor scaling the length of the receiving path (including external scaling cable and scaling antenna), LTx(nt)For the length of each transmit channel, LTx(nt),calFor scaling the spatial distance of the antenna to each transmitting antenna, STx(nt,f)The relative phase values of the received links with respect to the reference path are scaled for each transmit antenna.
Preferably, the scatter measurements for all pairs of transmit and receive antennas relative to the target point are:
wherein, (Xn, Yn, Zn) is the coordinates of the target point.
Preferably, the signal of formula (8) is determined by formula (6), formula (7) and the determined quantity L obtained by S21\ S22\ S23Rx(nr),calAnd LTx(nt),calAnd carrying out pre-calibration to obtain a pre-calibration signal:
wherein,
is an effective phase value S in practical applicationTx(nt),Rx(nr),f,(XnYnZn)(afterCal)，
Is the phase residual after pre-calibration.
Preferably, in S33, the phase residue in S32 is calculated by obtaining a mutual coupling test signal of a certain transceiver antenna pair and processing the value of the mutual coupling test signal by using background calibration
Preferably, the pre-calibrated value S obtained in S32Tx(nt),Rx(nr),f,(XnYnZn)(Pre-calibration) with the phase residue obtained in S33
Multiplying to obtain phase data required in practical application:
according to the technical scheme, the invention provides the calibration method of the radio frequency channel of the double calibration antenna for millimeter wave security check imaging, the calibration method of the radio frequency channel of the double calibration antenna for millimeter wave security check imaging respectively obtains calibration test data by using two external calibration antennas only needing to roughly estimate positions, and position coordinates of the two calibration antennas are accurately calculated through mutual calibration and related analysis processing between two sets of calibration test data, so that calibration of a radio frequency receiving/transmitting channel is completed. According to the calibration method for the radio frequency channel of the double calibration antenna for millimeter wave security check imaging, the position coordinates of the calibration antenna do not need to be directly measured, but the position of the calibration antenna is accurately obtained through data statistics and analysis, so that the positioning precision is high, and the requirement of the imaging quality of a corresponding system radio frequency receiving/transmitting channel calibration result can be met.
Drawings
FIG. 1 is a schematic diagram of a millimeter wave human body security inspection imager calibration system;
FIG. 2 is a schematic diagram of a single-scale radio frequency channel antenna calibration method;
FIG. 3 is a schematic structural diagram of a specific implementation process of the calibration method for the RF channel of the dual-calibration antenna for millimeter wave security inspection imaging according to the present invention;
FIG. 4 is a schematic flowchart illustrating steps of a calibration method for a dual-calibration antenna RF channel for millimeter wave security imaging according to the present invention;
FIG. 5 is a schematic view of a point target test;
FIG. 6 is a schematic diagram of background calibration of a dual-calibration antenna RF channel calibration method for millimeter wave security inspection imaging according to the present invention;
fig. 7 is a diagram of the actual imaging effect of the system.
Description of the reference numerals
1. A receiving antenna; 2. a transmitting antenna; 3. a reference path; 4. calibrating a receiving/transmitting path; 5. calibrating the antenna; 51. a first targeting antenna; 52. a second scaled antenna.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
In the description of the present application, the terms "first", "second" are used for descriptive purposes only and are not to be construed as indicating relative importance or as implicitly indicating the number of technical features indicated. Thus, unless otherwise specified, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; "plurality" means two or more. The terms "comprises" and "comprising," and any variations thereof, are intended to cover a non-exclusive inclusion, such that one or more other features, integers, steps, operations, elements, components, and/or combinations thereof may be present or added.
Further, terms of orientation or positional relationship indicated by "center", "lateral", "upper", "lower", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, are described based on the orientation or relative positional relationship shown in the drawings, are simply for convenience of description of the present application, and do not indicate that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present application.
Furthermore, unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly and may include, for example, fixed connections, removable connections, and integral connections; can be mechanically or electrically connected; either directly or indirectly through intervening media, or through both elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.
Referring to fig. 3-4, the present invention provides a calibration method S10 for a dual-calibration antenna radio frequency channel for millimeter wave security inspection imaging, where the calibration method S10 for a dual-calibration antenna radio frequency channel for millimeter wave security inspection imaging is applicable to a millimeter wave security inspection imager, and specifically includes the following steps:
s1, providing two external calibration antennas, specifically a first calibration antenna and a second calibration antenna, and respectively obtaining corresponding calibration test values, namely receiving calibration signals of all receiving antennas relative to the first calibration antenna and the second calibration antenna;
s2, carrying out mutual calibration and correlation analysis processing on the two groups of calibration test values to obtain true values of coordinates of two external calibration antennas;
and S3, calibrating the radio frequency channel by using the truth values of the two external calibration antenna coordinates.
According to the calibration method for the double-calibration antenna radio frequency channel for millimeter wave security check imaging, the position coordinates of the calibration antenna do not need to be directly measured, but the true value of the position of the calibration antenna is obtained through data statistics analysis, so that calibration of the radio frequency transceiving channel is accurately achieved, and the imaging effect of the millimeter wave security check imager is better.
Specifically, the test values of the receiving calibration of the first calibration antenna and the second calibration antenna in S1 are respectively:
wherein, L1rlScaling the length of the transmission path, L, for a first scaled antennarefIs the length of the reference path, LRx(nr)For the length of each receive channel, L1Rx(nr),calIs the true value of the spatial distance from the first antenna to each receiving antenna, S1Rx(nr,f)A phase relative value of "first calibration antenna + nth receiving antenna path" with respect to the reference path; l2rlScaling the length of the transmission path, L, for a second scaled antennarefIs the length of the reference path, LRx(nr)For the length of each receive channel, L2Rx(nr),calTrue values of the spatial distances from the second calibration antenna to the respective receiving antennas, S2Rx(nr,f)For the relative reference path of the 'second scaling antenna + the' nth receiving antenna pathThe relative value of the phase of (c); λ is the wavelength corresponding to the working frequency point, and j is the complex imaginary part indicator.
Here, S1Rx(nr,f)、S2Rx(nr,f)Is a measurement value that can be automatically obtained by two scaling antenna reception scaling, L1Rx(nr),cal、L2Rx(nr),calIs a definite value which exists objectively, but only under the premise that (X1cal, Y1cal, Z1cal), (X2cal, Y2cal, Z2cal) is accurately positioned, L1Rx(nr),cal、L2Rx(nr),calCan participate in the associated scaling operation as an accurate known quantity.
According to the double-calibration antenna radio frequency channel calibration method for millimeter wave security inspection imaging, under the condition that the positions (X1cal, Y1cal and Z1cal) and (X2cal, Y2cal and Z2cal) of two calibration antennas are unknown, the true values of (X1cal, Y1cal and Z1cal) and (X2cal, Y2cal and Z2cal) are obtained through corresponding tests and algorithm analysis, and then calibration accuracy is improved, so that consistency calibration of radio frequency channels can be achieved.
Further, the S2 specifically includes the following steps:
s21, acquiring coordinate ranges of the first calibration antenna and the second calibration antenna, respectively taking a point in the coordinate ranges of the first calibration antenna and the second calibration antenna, and calculating the distance from the point to each receiving antenna;
s22, combining the points taken on the first calibration antenna and the second calibration antenna, pre-calibrating the receiving calibration signals in the formulas (1) and (2) to obtain receiving pre-calibration signals; and
s23, performing mathematical operation on the received pre-calibration signals corresponding to the points taken by the first calibration antenna and the second calibration antenna to obtain true values of the coordinates of the first calibration antenna and the second calibration antenna.
Furthermore, the coordinate ranges of the first calibration antenna and the second calibration antenna in S21 are obtained by visual measurement or size measurement, and only needs to be accurate to a decimeter level. The coordinates of the two external calibration antennas and the distances from the point to each receiving antenna selected in the coordinate range are as follows:
first calibration antenna: x1cal∈(X11,X1Nx1)Y1cal∈(Y11,Y1Ny1)Z1cal∈(Z11,Z1Nz1)
A second scaling antenna: x2cal∈(X21,X2Nx2)Y2cal∈(Y21,Y2Ny2)Z2cal∈(Z21,Z2Nz2)
A point is respectively taken from the coordinate ranges of the first scaling antenna and the second scaling antenna and respectively marked as (X1)nx1,Y1ny1,Z1nz1) And (X2)nx2,Y2ny2,Z2nz2) Then the distance from the selected point on the first calibration antenna to each receiving antenna is L1Rx(nr),(X1nx1,Y1ny1,Z1nz1)The distance from the selected point on the second scaling antenna to each receiving antenna is L2Rx(nr),(X2nx2,Y2ny2,Z2nz2)。
Here, it is to be noted that (X1)cal,Y1cal,Z1cal) I.e. the true value of the coordinates of the first calibration antenna, (X2)cal,Y2cal,Z2cal) Which is the true value of the coordinates of the second scaled antenna.
The distances L1 from the selected point on the first calibration antenna to each receiving antenna are used for the points on the first calibration antenna and the second calibration antenna in S22Rx(nr),(X1nx1,Y1ny1,Z1nz1)Distance L2 from the selected point on the second scaled antenna to each of the receiving antennasRx(nr),(X2nx2,Y2ny2,Z2nz2)，Pre-calibrating the receiving calibration signals in the formula (1) and the formula (2), and obtaining receiving pre-calibration signals respectively as follows:
in the two calibration test processes of the first calibration antenna and the second calibration antenna, the same connecting cable is limited to be used, and then: l1rl＝L2rl. Of course, the use of the same connecting cable is not necessary, but different connecting cables may be used in order to simplify the process.
Multiplying the conjugate of equation (3) by equation (4) eliminates the unknown reference path length LrefLength L of RF receiving channelRx(nr)And a scaled path length L1rlAnd L2rlThe phase difference values of the received pre-calibration signals obtained by mathematical operation in S23 and using the points respectively taken on the first calibration antenna and the second calibration antenna may be specifically:
wherein,
has a phase value of
Show to make
Summing absolute values of all receiving antennas and all test frequency points;
traverse first scaled antenna position (X1)nx1,Y1ny1,Z1nz1) And a second scaled antenna position (X2)nx2,Y2ny2,Z2nz2) To make
Taking the minimum value (X1)nx1,Y1ny1,Z1nz1) And (X2)nx2,Y2ny2,Z2nz2) I.e. (X1)cal,Y1cal,Z1cal) And (X2)cal,Y2cal,Z2cal) True value of (1).
Through the double-antenna calibration test and data analysis, the calibration antenna position is obtainedDevice (X1)cal,Y1cal,Z1cal) And (X2)cal,Y2cal,Z2cal) The method has high enough precision (true value), so that the method can lay a foundation for realizing the precise calibration of the radio frequency receiving/transmitting channel of the millimeter wave security inspection imager and meet the imaging requirement of the system.
In the present invention, the S3 specifically includes the following steps:
s31, obtaining the relative phase value of the link from each receiving antenna to the reference path and the relative phase value of the link from each transmitting antenna to the calibration receiving to the reference path;
s32, measuring scattering measurement values of all the transmitting-receiving antenna pairs relative to a target point, and completing pre-calibration of a phase value of a link in practical application and a phase value in measurement;
s33, obtaining the phase residual quantity in S32 by using background calibration;
and S34, supplementing the phase residual quantity to realize the final calibration of the radio frequency channel.
Specifically, the radio frequency calibration process of the millimeter wave security inspection imager is divided into three steps, namely receiving calibration, transmitting calibration and background calibration, for calibration antenna position coordinates (Xcal, Ycal, Zcal) which are accurately obtained, wherein the calibration refers to the consistency correction of each transmitting/receiving antenna channel in the phased array antenna system and is a calibration process.
Further, in S31, the scaling the relative phase value of the link transmitted to each receiving antenna with respect to the reference path is:
wherein L isrlFor calibrating the length of the transmission path (including external calibration cable and calibration antenna), LrefIs the length of the reference path, LRx(nr)For each receive channel length (the amount that needs to be calibrated), LRx(nr),calFor scaling the spatial distance of the antenna to each receiving antenna, SRx(nr,f)For scaling the relative reference of the chains transmitted to each receiving antennaThe relative phase value of the path is a known quantity measured. Equation (6) is a receiving calibration process, and is obtained by conjugate multiplication of the link acquisition signal transmitted to each receiving antenna and the reference path acquisition signal.
The phase relative value of the link from each transmitting antenna to the calibration receiving in S31 with respect to the reference path specifically is:
wherein L istlFor scaling the length of the receiving path (including external scaling cable and scaling antenna), LTx(nt)For each transmit channel length (the amount that needs to be calibrated), LTx(nt),calFor scaling the spatial distance of the antenna to each transmitting antenna, STx(nt,f)The relative phase values of the links to the reference path for each transmit antenna to the scaled receive are measured known quantities. Equation (7) is a transmission calibration process, and is obtained by conjugate multiplication of a link acquisition signal received from a transmitting antenna to calibration and a reference path acquisition signal.
In S32, obtaining scattering measurement values of all transceiver antenna pairs relative to the target point specifically includes:
where, (Xn, Yn, Zn) is the target point coordinate, as shown in fig. 5.
Then, the determination amount L is determined by using the formula (6), the formula (7) and the results of S21\ S22\ S23Rx(nr),calAnd LTx(nt),calPre-calibrating equation (8) to obtain a pre-calibration signal:
wherein,
for practical applicationEffective phase value of, STx(nt),Rx(nr),f,(XnYnZn)(afterCal)，
Is the phase residual after pre-calibration.
Further, in S33, the phase residue in S32 is calculated by obtaining the mutual coupling test signal of a certain transceiver antenna pair by using background calibration and processing the value thereof
Specifically, as shown in fig. 6, the background calibration is obtained by obtaining the mutual coupling test signal of the transmitting antenna 4 and the receiving antenna 1 (the antenna pair with the strongest mutual coupling signal), and performing conjugate multiplication with the reference path acquisition signal, and the calibration test value is:
wherein L is4-1The spatial distance from the horn mouth of the transmitting antenna 4 to the horn mouth of the receiving antenna 1 is a known quantity, LrefIs the length of the reference path, S4-1，fThe phase relative value of the antenna pair formed by the transmitting antenna 4 and the receiving antenna 1 relative to the reference path.
Using formula (6), formula (7), and formula (8.1), nr equals 1 for formula (6) and nt equals 4 for formula (7), it is possible to obtain:
namely:
the right hand ends of equation (8.2) are all quantities or known quantities obtained by three sets of calibration tests, then the quantities to the left of equation (8.2)
The phase residual amount can be simply obtained as the phase residual amount required in S32.
Precalibrated value S obtained in S32Tx(nt),Rx(nr),f,(XnYnZn)(Pre-calibration) with the phase residue obtained in S33
Multiplying to obtain phase data required in practical application:
in S32, equation (8) is calibrated by equation (6), equation (7), and equation (8.2), and finally the link phase value required in practical application is obtained:
the specific calibration procedure of equation (9) is:
wherein S isTx(nt),Rx(nr),f,(XnYnZn)、SRx(nr,f)、STx(nt,f)Are all the data that have been measured and,
and (3) for the calculated quantity, obtaining an equation (9), wherein the equation (9) is calibrated test data of each transceiving channel required by the relevant imaging algorithm, and the data simultaneously calibrates a zero phase reference point of an antenna transceiving channel to the antenna phase center.
The final formula (9) is effective test data required by the millimeter wave security inspection imager in practical application, the actual imaging effect is as shown in fig. 7, and of course, the calibration process in practical application is automatically completed through program control.
According to the technical scheme, the invention provides the calibration method of the radio frequency channel of the double calibration antenna for millimeter wave security check imaging, the calibration method of the radio frequency channel of the double calibration antenna for millimeter wave security check imaging respectively obtains calibration test data by using two external calibration antennas only needing to roughly estimate positions, and position coordinates of the two calibration antennas are accurately calculated through mutual calibration and related analysis processing between two sets of calibration test data, so that calibration of a radio frequency receiving/transmitting channel is completed. According to the calibration method for the radio frequency channel of the double calibration antenna for millimeter wave security check imaging, the position coordinates of the calibration antenna do not need to be directly measured, but the position of the calibration antenna is accurately obtained through data statistics and analysis, so that the positioning precision is high, and the requirement of the imaging quality of a corresponding system radio frequency receiving/transmitting channel calibration result can be met.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (12)
1. A double-scaling antenna radio frequency channel calibration method for millimeter wave security check imaging is characterized by comprising the following steps:
s1, providing two external calibration antennas, specifically a first calibration antenna and a second calibration antenna, and respectively obtaining corresponding calibration test values, namely receiving calibration signals of all receiving antennas relative to the first calibration antenna and the second calibration antenna;
s2, carrying out mutual calibration and correlation analysis processing on the two groups of calibration test values to obtain true values of coordinates of two external calibration antennas;
and S3, calibrating the radio frequency channel by using the truth values of the two external calibration antenna coordinates.
2. The calibration method for the rf channel of the dual-calibration antenna for millimeter wave security inspection imaging according to claim 1, wherein the test values of the receiving calibration of the first calibration antenna and the second calibration antenna in S1 are respectively:
wherein, L1r1Scaling the length of the transmission path, L, for a first scaled antennarefIs the length of the reference path, LRx(nr)For the length of each receive channel, L1Rx(nr)，calIs the true value of the spatial distance from the first antenna to each receiving antenna, S1Rx(nr，f)A phase relative value of "first calibration antenna + nth receiving antenna path" with respect to the reference path; l2r1Scaling the length of the transmission path, L, for a second scaled antennarefIs the length of the reference path, LRx(nr)For the length of each receive channel, L2Rx(nr)，calTrue values of the spatial distances from the second calibration antenna to the respective receiving antennas, S2Rx(nr，f)A phase relative value of "second scaling antenna + nth receiving antenna path" with respect to the reference path; λ is the wavelength corresponding to the working frequency point, and j is the complex imaginary part indicator.
3. The calibration method for the rf channel of the dual-scaled antenna used for millimeter wave security inspection imaging according to claim 1, wherein the step S2 specifically includes the following steps:
s21, acquiring coordinate ranges of the first calibration antenna and the second calibration antenna, respectively taking a point in the coordinate ranges of the first calibration antenna and the second calibration antenna, and calculating the distance from the point to each receiving antenna;
s22, combining the points taken on the first calibration antenna and the second calibration antenna, pre-calibrating the receiving calibration signals in the formulas (1) and (2) to obtain receiving pre-calibration signals; and
s23, performing mathematical operation on the received pre-calibration signals corresponding to the points taken by the first calibration antenna and the second calibration antenna to obtain true values of the coordinates of the first calibration antenna and the second calibration antenna.
4. The method for calibrating the radio frequency channel of the dual-calibration antenna for millimeter wave security inspection imaging according to claim 3, wherein the coordinate ranges of the first calibration antenna and the second calibration antenna in S21 are obtained by visual observation or measurement, and the coordinates of the two external calibration antennas and the distances from the point selected in the coordinate ranges to the receiving antennas are specifically as follows:
first calibration antenna: x1cal∈(X11，X1Nx1)Y1cal∈(Y11，Y1Ny1)Z1cal∈(Z11，Z1Nz1)
A second scaling antenna: x2cal∈(X21，X2Nx2)Y2cal∈(Y21，Y2Ny2)Z2cal∈(Z21，Z2Nz2)
Wherein, (X1)cal，Y1cal，Z1cal) I.e. the true value of the coordinates of the first calibration antenna, (X2)cal，Y2cal，Z2cal) The true value of the coordinate of the second calibration antenna is obtained; the coordinate of the point selected on the first calibration antenna is marked as (X1)nx1，Y1ny1，Z1nz1) The coordinate of the point selected on the second scaled antenna is marked as (X2)nx2，Y2ny2，Z2nz2) Then the distance from the selected point on the first calibration antenna to each receiving antenna is L1Rx(nr)，(X1nx1，Y1ny1，Z1nz1)The distance from the selected point on the second scaling antenna to each receiving antenna is L2Rx(nr)，(X2nx2，Y2ny2，Z2nz2)。
5. The method for calibrating the RF channel of the dual-calibration antenna for millimeter wave security inspection imaging according to claim 4, wherein the first calibration antenna and the second calibration antenna in S22The distance L1 between the selected point on the first antenna and each receiving antennaRx(nr)，(X1nx1，Y1ny1，Z1nz1)Distance L2 from the selected point on the second scaled antenna to each of the receiving antennasRx(nr)，(X2nx2，Y2ny2，Z2nz2)Pre-calibrating the receiving calibration signals in the formula (1) and the formula (2), and obtaining receiving pre-calibration signals respectively as follows:
6. the method for calibrating a radio frequency channel of a dual-calibration antenna for millimeter wave security inspection imaging according to claim 5, wherein the phase difference value of the received pre-calibration signal obtained by using the points respectively taken on the first calibration antenna and the second calibration antenna through mathematical operation in S23 is specifically:
wherein,
has a phase value of
traverse first scaled antenna position (X1)nx1，Y1ny1，Z1nz1) And a second scaled antenna position (X2)nx2，Y2ny2，Z2nz2) To make
Taking the minimum value (X1)nx1，Y1ny1，Z1nz1) And (X2)nx2，Y2ny2，Z2nz2) I.e. (X1)cal，Y1cal，Z1cal) And (X2)cal，Y2cal，Z2cal) True value of (1).
7. The calibration method for the rf channel of the dual-scaled antenna used for millimeter wave security inspection imaging according to claim 1, wherein the step S3 specifically includes the following steps:
s31, obtaining the relative phase value of the link from each receiving antenna to the reference path and the relative phase value of the link from each transmitting antenna to the calibration receiving to the reference path;
s32, measuring scattering measurement values of all the transmitting-receiving antenna pairs relative to a target point, and completing pre-calibration of a phase value of a link in practical application and a phase value in measurement;
s33, obtaining the phase residual quantity in S32 by using background calibration;
and S34, supplementing the phase residual quantity to realize the final calibration of the radio frequency channel.
8. The method according to claim 7, wherein the step S31 is to calibrate the relative phase values of the link from the reference path to the receiving antennas and the relative phase values of the link from the transmitting antennas to the reference path to the calibration receiving antennas specifically include:
wherein L isr1For calibrating the length of the transmission path (including external calibration cable and calibration antenna), LrefIs the length of the reference path, LRx(nr)For the length of each receiving channel, LRx(nr)，calFor scaling the spatial distance of the antenna to each receiving antenna, SRx(nr，f)To scale the relative phase values of the links transmitted to each receive antenna with respect to a reference path; l ist1For scaling the length of the receiving path (including external scaling cable and scaling antenna), LTx(nt)For the length of each transmit channel, LTx(nt)，calFor scaling the spatial distance of the antenna to each transmitting antenna, STx(nt，f)The relative phase values of the received links with respect to the reference path are scaled for each transmit antenna.
9. The dual-scaled antenna radio frequency channel calibration method for millimeter wave security imaging according to claim 8, wherein the scattering measurements for all pairs of transmit and receive antennas with respect to the target point are:
wherein, (Xn, Yn, Zn) is the coordinates of the target point.
10. The calibration method for the RF channel of the dual-calibration antenna for millimeter wave security inspection imaging according to claim 9, wherein the signal of formula (8) is determined by using formula (6), formula (7) and the determination quantity L obtained through S21\ S22\ S23Rx(nr)，calAnd LTx(nt)，calAnd carrying out pre-calibration to obtain a pre-calibration signal:
wherein,
is an effective phase value S in practical applicationTx(nt)，Rx(nr)，f，(XnYnZn)(afterCal)，
Is the phase residual after pre-calibration.
11. The method of claim 7, wherein the phase residue in S32 is calculated by obtaining the mutual coupling test signal of a certain transceiver antenna pair and processing the value thereof using background calibration in S33
12. The calibration method for the RF channel of the dual-scaled antenna used for millimeter wave security inspection imaging according to claims 10 and 11, wherein the pre-calibrated value S obtained in S32 is STx(nt)，Rx(nr)，f，(XnYnZn)(Pre-calibration) with the phase residue obtained in S33
Multiplying to obtain phase data required in practical application:
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