CN113514804B - FMCW-based security radar angle measurement correction method - Google Patents
FMCW-based security radar angle measurement correction method Download PDFInfo
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- CN113514804B CN113514804B CN202110729921.1A CN202110729921A CN113514804B CN 113514804 B CN113514804 B CN 113514804B CN 202110729921 A CN202110729921 A CN 202110729921A CN 113514804 B CN113514804 B CN 113514804B
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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
- G01S7/40—Means for monitoring or calibrating
- G01S7/4052—Means for monitoring or calibrating by simulation of echoes
- G01S7/4056—Means for monitoring or calibrating by simulation of echoes specially adapted to FMCW
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
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Abstract
The invention provides an FMCW-based security radar angle measurement correction method, which comprises the following steps: step 1: installing short-range FMCW security radar, and measuring 10m and theta in the normal direction of the distance radar 1 Position-placed doppler simulator as calibration target =0; step 2: receiving the target echo signal in the step 1, and performing FFT processing on the target echo signal to obtain phase information phi 1 The method comprises the steps of carrying out a first treatment on the surface of the Step 3: then the Doppler simulators are used as calibration targets to be respectively placed at 10m of the normal direction of the range radar and related to theta 1 Two symmetrical positions=0, collecting target echo data by short-range FMCW safe radar, and processing the target echo signal to obtain phase information phi 2 And phi 3 The method comprises the steps of carrying out a first treatment on the surface of the Step 4: by phase information phi 1 、φ 2 And phi 3 Obtaining a phase deviation factorCell pitch deviation factor Δd Repair tool The method comprises the steps of carrying out a first treatment on the surface of the The method ensures the radar angle measurement precision, is efficient and easy to implement, can simulate targets with different positions and speeds to calibrate the radar angle measurement, and improves the calibration efficiency.
Description
Technical Field
The invention relates to the technical field of radars, in particular to an FMCW-based safety radar angle measurement correction method.
Background
Millimeter wave radar is a high-precision sensor for measuring the relative distance, relative speed and direction of a measured object, and along with development and progress of radar technology, in recent years, millimeter wave radar is widely applied to the field of automobiles, and by transmitting millimeter waves outwards and receiving target reflected signals, physical environment information around the automobile body of an automobile, such as the relative distance, relative speed, angle, movement direction and the like, can be quickly and accurately obtained after processing.
With the continuous development of electronic technology, radar technology is widely applied in the civil field, wherein the radar based on short-range FMCW safety protection radar also has a brand-new angle in different application scenes, the radar belongs to system engineering, and the radar based on short-range FMCW safety protection radar needs angle measurement calibration in practical application in consideration of engineering errors. At present, a general angle measurement calibration method is to calibrate an angle reflector for a microwave darkroom, but the construction, use and maintenance costs of the microwave darkroom are high, and in addition, a method for calibrating the angle reflector for an external field is also provided, so that the radar cannot efficiently detect an angle reflector target due to the influence of ground clutter on the radar, and in view of the above method, a more efficient radar angle measurement calibration method is needed.
Disclosure of Invention
The invention aims to overcome the existing defects, and provides an angle measurement calibration method based on FMCW security, which aims to solve the defects that the radar cannot efficiently detect an angle reflector target due to the influence of ground clutter on the radar because the angle reflector is high in construction, use and maintenance cost of a microwave darkroom and the method for directly calibrating the angle reflector in an external field.
In order to achieve the above purpose, the present invention provides the following technical solutions: an FMCW-based security radar angle measurement correction method comprises the following steps:
step 1: installing short-range FMCW security radar, and measuring 10m and theta in the normal direction of the distance radar 1 A Doppler simulator is placed at the position of the (0) as a calibration target, and target echo data are acquired through the short-range FMCW security radar;
step 2: receiving the target echo signal in the step 1, and performing FFT processing on the target echo signal to obtain phase information phi 1 ;
Step 3: then the Doppler simulators are used as calibration targets to be respectively placed at 10m of the normal direction of the range radar and related to theta 1 Two symmetrical positions=0, collecting target echo data by the short-range FMCW safe radar, and processing the target echo signal to obtain phase information phi 2 And phi 3 ;
Step 4: by phase information phi 1 、φ 2 And phi 3 Obtaining a phase deviation factorCell pitch deviation factor Δd Repair tool 。
Preferably, in the step 2, the target echoes received by the receiving antenna are respectively subjected to two-dimensional FFT processing by the signal processor to obtain phase information of each path of target echoes, where the phase information is phi 1 =[φ 11 ,φ 12 ]。
Preferably, in the step 3, the radar normal direction θ is deviated 2 =α° and θ 3 Respectively placing Doppler simulators at the 10m positions of the= -alpha degrees and the distance short-range FMCW security radar as calibration targets, collecting target echo data through FMCW security radar, respectively performing two-dimensional FFT processing on target echoes received by a receiving antenna through a signal processor, and obtaining theta 2 =α° and θ 3 Two phase information of each path obtained in two states of = -alpha degrees, wherein the phase information is phi respectively 2 =[φ 21 ,φ 22 ]And phi 3 =[φ 31 ,φ 32 ]。
Preferably, in the step 4, according to a radar angle measurement formulaWherein->d=λ represents the spacing of the two receiving antennas, +.>Representing wave number, lambda representing radar working wavelength, and according to phase information phi in step 2 1 =[φ 11 ,φ 12 ]Obtaining a phase deviation factor->
Preferably, according to the phase information phi at step 3 2 =[φ 21 ,φ 22 ]Doppler simulation in step 3In a direction theta deviating from the normal of the radar 2 At =α°, according to the radar angle measurement formulaWherein-> The wave number and lambda are shown as the radar working wavelength, and d=lambda is theoretically calculated without considering the space error of the receiving channel, but the space error of the radar receiving channel in actual engineering needs to be corrected, and the phase information phi in the step 3 is firstly used for 2 =[φ 21 ,φ 22 ]Obtain channel phase difference->For->Normalization processing is performed if Since the target azimuth is known in step 3, the unit distance of the two paths of receiving antennas is calculated>
Preferably, according to the phase information phi at step 3 3 =[φ 31 ,φ 32 ]In step 3, the Doppler simulator deviates from the normal direction theta of the radar 3 At = - α°According to the radar angle measurement formulaWherein-> The wave number and lambda are shown as the radar working wavelength, and d=lambda is theoretically calculated without considering the space error of the receiving channel, but the space error of the radar receiving channel in actual engineering needs to be corrected, and the phase information phi in the step 3 is firstly used for 3 =[φ 31 ,φ 32 ]Obtain channel phase difference->For->Normalization processing is performed if-> Since the target azimuth is known in step 3, the unit distance of the two paths of receiving antennas is calculated>
Preferably, the unit receiving antenna unit distance d calculated in the step 3 is calculated 2 、d 3 Calculating a cell pitch deviation factor Deltad Repair tool Taking into account the symmetry of the two sets of correction sources and the accuracy of the angle measurementThe method comprises the steps of obtaining the data,calculation formula for confirming target angle ∈ ->
Compared with the prior art, the invention provides an FMCW-based security radar angle measurement correction method, which has the following beneficial effects:
the radar angle measurement method can effectively calibrate the radar angle based on short-range FMCW, ensures the radar angle measurement precision, is efficient and easy to implement, can simulate targets with different positions and speeds to calibrate the radar angle measurement, has no rigid requirement on a calibration site, and can improve the calibration efficiency.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate and together with the embodiments of the invention and do not constitute a limitation to the invention, and in which:
fig. 1 is a schematic diagram of a radar system structure based on an FMCW security radar angle measurement correction method according to the present invention.
Fig. 2 is a schematic diagram of an antenna structure according to the present invention.
FIG. 3 is a schematic diagram of the angular calibration method of the present invention.
Detailed Description
In order that the manner in which the above recited features, objects and advantages of the present invention are attained and can be readily understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings, but which are appended drawings. Based on the examples in the embodiments, those skilled in the art can obtain other examples without making any inventive effort, which fall within the scope of the invention.
As shown in fig. 1, the short-range FMCW-based security radar comprises a transmitting subsystem, a receiving subsystem, a signal processing subsystem, a data processing subsystem, a display control terminal subsystem and a power supply subsystem;
as shown in fig. 2, a short-range FMCW-based security radar antenna includes a transmit antenna and a receive antenna;
as shown in fig. 3, an FMCW-based short-range security radar angle measurement calibration method is characterized by comprising the following steps:
step 1: installing short-range FMCW security radar, and measuring 10m and theta in the normal direction of the distance radar 1 A Doppler simulator is placed at the position of the (0) as a calibration target, and target echo data are acquired through short-range FMCW security radar;
step 2: receiving the target echo signal in the step 1, and performing FFT processing on the target echo signal to obtain phase information phi 1 The method comprises the steps of carrying out a first treatment on the surface of the The target echoes received by the receiving antenna are respectively subjected to two-dimensional FFT processing through the signal processor to obtain phase information of each path of target echo, wherein the phase information is phi 1 =[φ 11 ,φ 12 ]。
Step 3: then the Doppler simulators are used as calibration targets to be respectively placed at 10m of the normal direction of the range radar and related to theta 1 Two symmetrical positions=0, collecting target echo data by short-range FMCW safe radar, and processing the target echo signal to obtain phase information phi 2 And phi 3 The method comprises the steps of carrying out a first treatment on the surface of the In a direction theta away from the normal of the radar 2 =α° and θ 3 Respectively placing Doppler simulators at the 10m positions of the= -alpha degrees and the distance short-range FMCW security radar as calibration targets, collecting target echo data through FMCW security radar, respectively performing two-dimensional FFT processing on target echoes received by a receiving antenna through a signal processor, and obtaining theta 2 =α° and θ 3 Two phase information of each path obtained in two states of = -alpha degrees, wherein the phase information is phi respectively 2 =[φ 21 ,φ 22 ]And phi 3 =[φ 31 ,φ 32 ]The method comprises the steps of carrying out a first treatment on the surface of the According to the phase information phi in the step 3 2 =[φ 21 ,φ 22 ]In step 3, the Doppler simulator deviates from the normal direction theta of the radar 2 At =α°, according to the radar angle measurement formulaWherein-> The wave number and lambda are shown as the radar working wavelength, and d=lambda is theoretically calculated without considering the space error of the receiving channel, but the space error of the radar receiving channel in actual engineering needs to be corrected, and the phase information phi in the step 3 is firstly used for 2 =[φ 21 ,φ 22 ]Obtain channel phase difference->For->Normalization processing is performed if-> Since the target azimuth is known in step 3, the unit distance of the two paths of receiving antennas is calculated>According to the phase information phi in the step 3 3 =[φ 31 ,φ 32 ]In step 3, the Doppler simulator deviates from the normal direction theta of the radar 3 At = - α°, according to the radar angle measurement formula +.>Wherein the method comprises the steps of The wave number and lambda are shown as the radar working wavelength, and d=lambda is theoretically calculated without considering the space error of the receiving channel, but the space error of the radar receiving channel in actual engineering needs to be corrected, and the phase information phi in the step 3 is firstly used for 3 =[φ 31 ,φ 32 ]Obtain channel phase difference->For->Normalization processing is performed if-> Since the target azimuth is known in step 3, the unit distance of the two paths of receiving antennas is calculated>According to the unit receiving antenna unit distance d calculated in the step 3 2 、d 3 Calculating a cell pitch deviation factor Deltad Repair tool Considering the symmetry of the two sets of correction sources and the requirements of angular accuracy, +.>Calculation formula for confirming target angle ∈ ->
Step 4: by phase information phi 1 、φ 2 And phi 3 Obtaining a phase deviation factorCell pitch deviation factor Δd Repair tool The method comprises the steps of carrying out a first treatment on the surface of the According to the radar angle measurement formula->Wherein->d=λ represents the spacing of the two receiving antennas, +.>Representing wave number, lambda representing radar working wavelength, and according to phase information phi in step 2 1 =[φ 11 ,φ 12 ]Obtaining a phase deviation factor->The radar angle measurement is calibrated by simulating targets with different positions and speeds, and the calibration method has no rigid requirement on a calibration site, so that the calibration efficiency can be improved.
The foregoing has shown and described the basic principles, principal features and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiments, and that the above-described embodiments and descriptions are only preferred embodiments of the present invention, and are not intended to limit the invention, and that various changes and modifications may be made therein without departing from the spirit and scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (7)
1. An FMCW-based security radar angle measurement correction method is characterized by comprising the following steps:
step 1: installing short-range FMCW security radar, and measuring 10m and theta in the normal direction of the distance radar 1 A Doppler simulator is placed at the position of the (0) as a calibration target, and target echo data are acquired through the short-range FMCW security radar;
step 2: receiving the target echo signal in the step 1, and performing FFT processing on the target echo signal to obtain phase information phi 1 ;
Step 3: then the Doppler simulators are used as calibration targets to be respectively placed at 10m of the normal direction of the range radar and related to theta 1 Two symmetrical positions=0, collecting target echo data by the short-range FMCW safe radar, and processing the target echo signal to obtain phase information phi 2 And phi 3 ;
2. The FMCW-based safety radar angle correcting method according to claim 1, wherein: in the step 2, two-dimensional FFT processing is performed on the target echoes received by the receiving antenna through the signal processor, so as to obtain phase information of each path of target echoes, wherein the phase information is phi 1 =[φ 11 ,φ 12 ]。
3. The FMCW-based safety radar angle correcting method according to claim 1, wherein: in the step 3, the radar normal direction theta is deviated 2 =α° and θ 3 Respectively placing Doppler simulators at the 10m positions of the= -alpha degrees and the distance short-range FMCW security radar as calibration targets, collecting target echo data through FMCW security radar, respectively performing two-dimensional FFT processing on target echoes received by a receiving antenna through a signal processor, and obtaining theta 2 =α° and θ 3 Two paths obtained in two states of = -alpha °Seed phase information, the phase information is phi respectively 2 =[φ 21 ,φ 22 ]And phi 3 =[φ 31 ,φ 32 ]。
4. The FMCW-based safety radar angle correcting method according to claim 2, wherein: in the step 4, according to the radar angle measurement formulaWherein->d=λ represents the distance between two receiving antennas,Representing wave number, lambda representing radar working wavelength, and according to phase information phi in step 2 1 =[φ 11 ,φ 12 ]Obtaining a phase deviation factor->
5. A FMCW-based safety radar angle correcting method according to claim 3, wherein: according to the phase information phi in the step 3 2 =[φ 21 ,φ 22 ]In step 3, the Doppler simulator deviates from the normal direction theta of the radar 2 At =α°, according to the radar angle measurement formulaWherein->The wave number and lambda represent the radar working wavelength, and in theory, d=lambda is not considered in the condition of receiving channel spacing error, but in actual engineering, the radar receiving channel spacing deviation needs to be corrected, firstly, according to the step 3Phase information phi 2 =[φ 21 ,φ 22 ]Obtain channel phase difference->For a pair ofNormalization processing is performed if->Since the target azimuth is known in step 3, the unit distance of the two paths of receiving antennas is calculated>
6. The FMCW-based safety radar angle correcting method according to claim 5, wherein: according to the phase information phi in the step 3 3 =[φ 31 ,φ 32 ]In step 3, the Doppler simulator deviates from the normal direction theta of the radar 3 At = - α°, according to the radar angle measurement formulaWherein->The wave number and lambda are shown as the radar working wavelength, and d=lambda is theoretically calculated without considering the space error of the receiving channel, but the space error of the radar receiving channel in actual engineering needs to be corrected, and the phase information phi in the step 3 is firstly used for 3 =[φ 31 ,φ 32 ]Obtaining the channel phase differenceFor->Normalization processing is performed ifSince the target azimuth is known in step 3, the unit distance of the two paths of receiving antennas is calculated>
7. The FMCW-based safety radar angle correcting method according to claim 6, wherein: according to the unit receiving antenna unit distance d calculated in the step 3 2 、d 3 Calculating a cell pitch deviation factor Deltad Repair tool Considering the symmetry of the two sets of correction sources and the requirement of angular accuracy,calculation formula for confirming target angle
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Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6121919A (en) * | 1999-07-23 | 2000-09-19 | Eaton-Vorad Technologies, L.L.C. | Method and apparatus for range correction in a radar system |
JP2016161409A (en) * | 2015-03-02 | 2016-09-05 | 株式会社東芝 | Radar system and radar signal processing method of the same |
CN110554366A (en) * | 2019-09-02 | 2019-12-10 | 北京电子工程总体研究所 | Method and device for automatically calibrating amplitude-phase consistency of seeker |
CN111537966A (en) * | 2020-04-28 | 2020-08-14 | 东南大学 | Array antenna error correction method suitable for millimeter wave vehicle-mounted radar field |
CN112578358A (en) * | 2020-12-29 | 2021-03-30 | 深圳承泰科技有限公司 | Calibration method and device for millimeter wave radar |
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Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6121919A (en) * | 1999-07-23 | 2000-09-19 | Eaton-Vorad Technologies, L.L.C. | Method and apparatus for range correction in a radar system |
JP2016161409A (en) * | 2015-03-02 | 2016-09-05 | 株式会社東芝 | Radar system and radar signal processing method of the same |
CN110554366A (en) * | 2019-09-02 | 2019-12-10 | 北京电子工程总体研究所 | Method and device for automatically calibrating amplitude-phase consistency of seeker |
CN111537966A (en) * | 2020-04-28 | 2020-08-14 | 东南大学 | Array antenna error correction method suitable for millimeter wave vehicle-mounted radar field |
CN112578358A (en) * | 2020-12-29 | 2021-03-30 | 深圳承泰科技有限公司 | Calibration method and device for millimeter wave radar |
Non-Patent Citations (1)
Title |
---|
主动防护雷达的角度标校;马可;张远安;王仁涛;王毅;李慧敏;;电子测量技术(01);全文 * |
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