CN110146859B - Method and device for radar scattering cross section RCS calibration - Google Patents
Method and device for radar scattering cross section RCS calibration Download PDFInfo
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- CN110146859B CN110146859B CN201910455642.3A CN201910455642A CN110146859B CN 110146859 B CN110146859 B CN 110146859B CN 201910455642 A CN201910455642 A CN 201910455642A CN 110146859 B CN110146859 B CN 110146859B
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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
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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
- G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
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Abstract
The invention provides a method and a device for radar scattering cross section RCS calibration, wherein the method comprises the following steps: performing RCS measurements on a satellite having an incompletely regular profile formed by loading radar reflector loads having a regular geometric profile on a satellite platform to form an RCS two-dimensional data table, and calibrating RCS measurement K values using radar equations in conjunction with the RCS two-dimensional data table. By utilizing the technical scheme of the invention, a space-based RCS calibration standard can be provided for the ground multi-band pulse radar, and compared with the traditional ball-playing calibration mode, the method has obvious economic effect.
Description
Technical Field
The present invention relates generally to the field of radar measurement technology. More particularly, the present invention relates to Radar scattering Cross Section ("RCS") calibration and systematic error calibration techniques.
Background
The RCS of the target reflects the scattering ability of the target on the radar irradiation electromagnetic wave and is an important parameter of the target characteristic. The target RCS is measured by a ground reflection radar, and the precision of a measuring result is closely related to the calibration precision of radar equipment. The target RCS measurement is a process of converting the echo power of a radar receiver by using a radar equation, and is generally divided into an absolute calibration method and a relative calibration method, and the relative calibration method is generally adopted at present. The method comprises the basic process that the relation between the echo power of a target to be detected and the echo power of a reference target is established through calibrating an accurate RCS reference target, and the RCS of the target to be detected is calculated.
To reduce the RCS error value of the reference target, the reference target currently generally employs a metal reflector with a regular geometric shape, most typically a spherical shape, to ensure that the target RCS is independent of the observation attitude. The prior method for calibrating RCS (Rich research institute of air force and Equipment), published in 12.2011, volume 5, phase 6, pages 11 to 13, discloses a method for calibrating RCS (Rich concrete System) by using regular geometric bodies in the world at present, wherein the most typical method is an LCS (Long service Scale) series calibration satellite which is a hollow aluminum ball with the thickness of about 3.2mm and the diameter of 1.12m, and the optical reflection section of the satellite is constant to pi R no matter what attitude angle is observed2=1m2. The calibration satellite has the characteristics that the satellite does not have a conventional satellite platform, the calibration body is the satellite, and the attitude and the orbit of the calibration body are not controllable. However, if a conventional satellite platform is added for operation and control, the calibration body is damagedThe original target characteristic, the traditional RCS calibration method is not applicable any more.
Disclosure of Invention
The invention mainly overcomes the defect that a calibration body is added with a satellite platform, and provides a radar RCS calibration method by using an incomplete regular shape satellite.
In one aspect, the present invention provides a method for radar scattering cross-section RCS calibration, comprising: performing RCS measurements on a satellite to form an RCS two-dimensional data table, wherein the satellite has an incompletely regular profile formed by loading a radar reflector load having a regular geometric profile onto a satellite platform; and calibrating the RCS measurement K value by using a radar equation and combining an RCS two-dimensional data table.
In one embodiment, wherein RCS measurements are performed on a satellite based on measurement signals comprising a combination of at least frequency and polarization and measurement attitude, the measurement attitude is sampled over a range of calibration angles available from the radar reflector load, the attitude angles including azimuth and elevation dimensions.
In one embodiment, the K value is scaled using the following equation (1):
Ps: radar echo power;
Pr: radar transmission power:
r: the distance between the radar and the calibration body;
g: gain of the radar antenna;
σ: the reflection section of the whole satellite of the satellite;
θ, φ: the azimuth angle and the pitch angle of the satellite under the radar observation coordinate system are respectively.
The values of sigma (theta, phi) are obtained from a look-up table, G, PrIs a constant value, PsR is acquired by radar.
In another embodiment, the K value is averaged using the following equation (2):
wherein i represents the ith sample, and when i is more than 100, the arithmetic mean value is taken as the final result.
In one embodiment, the satellite platform has a symmetrical, regular shape.
In yet another aspect, the present invention provides an apparatus for radar scattering cross-section RCS calibration, comprising: radar reflector loads having a regular geometric shape; a satellite platform for carrying the radar reflector load and forming an incomplete regular shape when the radar reflector load is carried on the satellite platform, wherein the radar reflector load is configured to receive illuminating electromagnetic waves from a ground radar to assist in calibrating the RCS measurement K-values, wherein calibrating comprises calibrating the RCS measurement K-values using radar equations and in conjunction with a RCS two-dimensional data table obtained by performing RCS measurements on a satellite.
After the work is finished, the K value or the average value of K after multiple measurements can be bound into the radar and used as the parameter after calibration.
The traditional calibration mode is ball placement or airplane calibration, the ball placement is influenced by weather, the airplane calibration organization is difficult to implement, the economic cost is high, and the timeliness is not strong. Through the satellite calibration mode, have full weather, the real-time characteristics of being available, compare traditional mode, economy, high efficiency.
Drawings
The invention and its advantages will be better understood by reading the following description, provided by way of example only, and made with reference to the accompanying drawings, in which:
FIG. 1 is a schematic diagram of a satellite of a less than perfect regular shape according to an embodiment of the present invention;
FIG. 2 is a schematic illustration of attitude angles according to an embodiment of the invention; and
fig. 3 is a flow chart of a method for radar cross section RCS calibration according to an embodiment of the present invention.
Detailed Description
The invention mainly overcomes the defect that a calibration body is loaded on a satellite platform, and provides a scheme for carrying out radar RCS calibration by using an incomplete regular shape satellite. Specifically, the technical scheme adopted by the invention relates to the establishment of the accurate corresponding relation between the signal form, the target attitude and the calibration body RCS through the precision calibration of the ground in advance, and the influence caused by the fact that the reflection characteristic of the calibration body is damaged by a satellite platform is overcome. When the radar reaches the standard, the RCS of the calibration body is not a constant value any more, but a variable which changes along with the attitude, and the accurate RCS of the target is determined by utilizing the corresponding relation between the attitude of the target and the RCS, so that the calibration is completed. Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of a satellite of a less than perfect regular shape according to an embodiment of the present invention. As shown in fig. 1, the incomplete regular-profile satellite 100 includes a satellite platform 101 and a calibration body (i.e., radar reflector load) 102. In one embodiment, the satellite platform may be a cylinder, a cube (as shown in fig. 1), or the like with a symmetrical and regular shape to have a symmetrical shape as much as possible, so as to reduce the workload of ground calibration. Meanwhile, the overall dimension of the satellite platform should be as small as possible so as to reduce the damage to the calibration body RCS. In one embodiment, the calibration body 102 may be a calibration sphere with the largest diameter as possible on the premise that the launch vehicle can be carried, thereby reducing the influence of the satellite platform on the whole-satellite RCS.
FIG. 2 is a schematic illustration of attitude angles according to an embodiment of the invention. As shown in fig. 2, (the origin of coordinates is at the center of mass of the satellite, the x-axis is consistent with the direction of the satellite velocity, the y-axis is directed to the ground, the z-axis is consistent with the right-hand coordinate system, the theta angle is the angle between the incident direction of the radar and the projection on the xy plane and the x-axis,the angle is the angle between the radar incident direction and the xy plane).
Fig. 3 is a flow chart of a method 300 for radar scattering cross-section RCS calibration according to an embodiment of the present invention. As shown in fig. 3, at step 301, RCS measurements are performed on satellites having a non-fully regular profile formed by loading radar reflector loads having a regular geometric profile onto a satellite platform to form a RCS two-dimensional data table. At step 302, the RCS measurement K value is calibrated using radar equations in conjunction with the RCS two-dimensional data table.
In one embodiment, accurate RCS measurement is performed on the whole satellite in a ground microwave darkroom, and accurate RCS values of different signal forms and postures are obtained. During measurement, the signal form of a test signal transmitted by the simulated radar of the microwave darkroom test system is selected according to needs, the signal form comprises the working frequency and the polarization mode (horizontal polarization, vertical polarization, left-hand circular polarization and right-hand circular polarization) of the transmitted signal, and the attitude can comprise two dimensions of azimuth and pitching. In the test process, when the selection of the azimuth angle or the pitch angle cannot be continuous, an interval sampling mode can be adopted. The specific sampling interval and azimuth direction can mainly consider the symmetry of the reflection characteristic of the platform, and the pitch direction can mainly consider the angle precision of ground test equipment (a two-dimensional turntable for placing a satellite, and different postures of the satellite in flight can be simulated through the rotation of the two-dimensional turntable).
Wherein:
Ps: radar echo power;
Pr: radar transmission power:
r: the distance between the radar and the calibration body;
g: gain of the radar antenna;
σ: the reflection section of the whole satellite of the satellite;
θ, φ: the azimuth angle and the pitch angle of the satellite under the radar observation coordinate system are respectively.
The values of sigma (theta, phi) are obtained from a look-up table, G, PrIs a constant value, PsR is acquired by radar.
Further, the air conditioner is provided with a fan,i represents the ith sample, and when i is sufficiently large (i > 100), the arithmetic mean is taken as the final result.
After the calibration operation is completed, the obtained final K can be corrected0The values are bound into a radar and used as the calibrated parameters.
In another embodiment, the accurate RCS measurement is carried out on the whole satellite within the calibration angle range provided by the satellite, the measurement signal needs to be subjected to the combination of frequency point and polarization, the measurement attitude is sampled and covered within the calibration angle range provided by the load, and the attitude angle comprises two dimensions of azimuth and elevation. After accurate measurement, for each polarization and point-frequency combination, a two-dimensional data table of accurate RCS is formed at different observation angles.
Calculating the attitude and distance of the satellite relative to the radar by using the satellite orbit and the satellite flight attitude provided by the measurement and control system;
in the calibration process, the calibration calculation formula can be usedAnd obtaining a plurality of K value samples after a plurality of observations are carried out. The RCS values of the satellite under different attitudes are obtained by using accurate RCS measurement values in a ground microwave darkroom and by adopting a table look-up mode.
For example using modified calculation formulasTo obtain i sample values. In the technical scheme of the invention, the continuous sampling number i is required to be not less than 100, so that the method and the device can be utilizedTo obtain the arithmetic mean value K0。
Although the present invention is described in the above embodiments, the description is only for the convenience of understanding the present invention, and is not intended to limit the scope and application of the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (7)
1. A method for radar cross section RCS calibration, comprising:
performing RCS measurements on a satellite to form an RCS two-dimensional data table, wherein the satellite has an incompletely regular profile formed by loading a radar reflector load having a regular geometric profile onto a satellite platform; and
calibrating the RCS measurement K value by using a radar equation and combining an RCS two-dimensional data table;
wherein the K value is calibrated by the following formula (1):
Ps: radar echo power;
Pr: radar transmission power:
r: the distance between the radar and the calibration body;
g: gain of the radar antenna;
σ: the reflection section of the whole satellite of the satellite;
respectively is the azimuth angle and the pitch angle of the satellite under a radar observation coordinate system;
2. The method of claim 1, wherein the RCS measurements are performed on the satellite based on measurement signals comprising a combination of at least frequency and polarization and measurement attitude, the measurement attitude being sampled over a range of calibration angles available from the radar reflector load, the attitude angles including azimuth and elevation dimensions.
4. The method of claim 1, wherein the satellite platform has a symmetrical, regular shape.
5. An apparatus for radar cross section RCS calibration, comprising:
radar reflector loads having a regular geometric shape;
a satellite platform for carrying the radar reflector load and forming a non-perfect regular shape when the radar reflector load is carried on the satellite platform,
wherein the radar reflector load is configured to receive impinging electromagnetic waves from a ground radar to assist in calibrating the RCS measurement K value,
the calibration comprises the steps of calibrating an RCS measurement K value by utilizing a radar equation and combining an RCS two-dimensional data table obtained by performing RCS measurement on a satellite;
wherein the K value is calibrated by the following formula (1):
Ps: radar echo power;
Pr: radar transmission power:
r: the distance between the radar and the calibration body;
g: gain of the radar antenna;
σ: the reflection section of the whole satellite of the satellite;
respectively an azimuth angle and a pitch angle of the satellite under a radar observation coordinate system,
6. The apparatus of claim 5, wherein the RCS measurements are performed on the satellite based on measurement signals comprising a combination of at least frequency and polarization and measurement attitude, the measurement attitude being sampled over a range of calibration angles available from the radar reflector payload, the attitude angles including both azimuth and elevation dimensions.
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JP2013036969A (en) * | 2011-08-09 | 2013-02-21 | Keycom Corp | Radar cross section (rcs) measurement system |
DE102014110079B3 (en) * | 2014-07-17 | 2015-07-09 | Deutsches Zentrum für Luft- und Raumfahrt e.V. | Method for absolute radiometric calibration of the radar backscatter cross section of radar targets |
CN106093892B (en) * | 2016-05-23 | 2018-12-18 | 中国人民解放军63921部队 | Carry out Radar RCS calibration and exterior measuring calibration system simultaneously based on calibration satellite |
EP3364212A1 (en) * | 2017-02-15 | 2018-08-22 | Deutsches Zentrum für Luft- und Raumfahrt e.V. | A method and an apparatus for computer-assisted processing of sar raw data |
CN109752696B (en) * | 2017-11-06 | 2020-03-10 | 中国人民解放军61646部队 | RCS correction method for corner reflector in high-resolution synthetic aperture radar satellite image |
RU2674432C1 (en) * | 2018-02-08 | 2018-12-10 | Акционерное общество "Корпорация космических систем специального назначения "Комета" | Radar station with the active phased antenna array calibration method |
CN108717181B (en) * | 2018-06-27 | 2022-05-06 | 成都飞机工业(集团)有限责任公司 | Novel outdoor field static RCS preposed linkage calibration test method |
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