CN113552549A - Method and device for airborne downward-looking measurement calibration by using active calibration equipment - Google Patents

Method and device for airborne downward-looking measurement calibration by using active calibration equipment Download PDF

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CN113552549A
CN113552549A CN202110854612.7A CN202110854612A CN113552549A CN 113552549 A CN113552549 A CN 113552549A CN 202110854612 A CN202110854612 A CN 202110854612A CN 113552549 A CN113552549 A CN 113552549A
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CN113552549B (en
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卢永革
徐志明
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Beijing Institute of Environmental Features
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    • G—PHYSICS
    • G01—MEASURING; TESTING
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Abstract

The invention relates to a method and a device for airborne downward-looking measurement calibration by using active calibration equipment, wherein the method comprises the following steps: analyzing a calibration working scene of the measuring system and corresponding indexes of the measuring system; determining the receiving power range, the link gain and the equipment delay time of the active calibration equipment; determining a conversion relation between the link gain of the active calibration equipment and the RCS value of the passive standard body according to a radar equation; the RCS of the measurement data is determined using a relative comparison method according to the radar equation. The method of the invention inhibits the background clutter during calibration, thus improving the accuracy of airborne downward-looking measurement data, and the same active calibration equipment can replace passive standard bodies with various specifications, and the external field application is flexible and has important engineering application value.

Description

Method and device for airborne downward-looking measurement calibration by using active calibration equipment
Technical Field
The invention relates to the technical field of radar measurement calibration, in particular to a calibration method and a calibration device for airborne downward-looking measurement by using active calibration equipment.
Background
The airborne downward-looking measurement can acquire targets on the ground or the sea surface, electromagnetic scattering characteristic data in different directions, and the measurement method is also suitable for conditions of large ground-rubbing angles, so that the measurement method is more and more widely concerned; the large number of applications of ground-to-sea precision percussion weapons has made airborne downward-looking measurements increasingly prominent in the research of characteristics of targets in the sea.
Calibration is an essential step in airborne downward-looking measurement, and the precision of the calibration is directly related to the precision of measurement target data. At present, a plurality of passive standard bodies are mostly adopted for calibrating airborne downward-looking measurement and are seriously interfered by background clutter, the accuracy of downward-looking measurement data is required to be higher and higher by the deep research of target characteristics, and the accuracy requirement of downward-looking measurement on calibration data cannot be met by the passive standard body calibration method interfered by the background clutter.
Therefore, in order to overcome the above disadvantages, it is necessary to provide a calibration method and device for airborne downward-looking measurement by using active calibration equipment, so as to solve the problem of background clutter interference caused by using a passive standard body in the conventional airborne downward-looking measurement calibration.
Disclosure of Invention
The invention aims to solve the technical problem of background clutter interference caused by a passive standard body adopted by airborne downward-looking measurement calibration, and provides a calibration method and a calibration device for airborne downward-looking measurement by utilizing active calibration equipment aiming at the defects in the prior art.
In order to solve the technical problem, the invention provides a calibration method for airborne downward-looking measurement by using active calibration equipment, which comprises the following steps: analyzing a calibration working scene of the measuring system and corresponding indexes of the measuring system; determining the receiving power range, the link gain and the equipment delay time of the active calibration equipment; determining a conversion relation between the link gain of the active calibration equipment and the RCS value of the passive standard body according to a radar equation; the RCS of the measurement data is determined using a relative comparison method according to the radar equation.
Preferably, the analyzing and measuring system calibrates the working scene and the corresponding index of the measuring system, and comprises the following steps: the method comprises the steps of measuring the flying height of an airplane, the flying speed, the beam width of an airborne radar antenna, the included angle between the beam direction of the radar antenna and the ground, radar working parameters, transmitting power, antenna gain and the main lobe and side lobe ratio of the antenna.
Preferably, the determining the active calibration device received power range, the link gain and the device delay time comprises the following steps: calculating the farthest distance and the nearest distance of a main lobe of a measuring radar reaching active calibration equipment according to an airborne downward-looking measuring calibration working scene, and calculating the receiving power range of the active calibration equipment; determining the link gain of the active calibration equipment according to the received power index and the equivalent passive standard magnitude of the equipment; and determining delay time according to the clutter echo length in the mainlobe in the calibration working scene of the measuring radar.
Preferably, the method for determining the conversion relation between the link gain of the active calibration equipment and the RCS value of the passive standard body according to the radar equation comprises the following steps: the transmitting power of the airborne radar is PtAntenna transmission gain of GtThe effective receiving area of the antenna is AeIf RCS of the passive standard body is sigma, the distance from the radar antenna to the target is R, and the radar transmitting signal irradiates the passive standard body and is reflected back, then the radar receiving power Pr1Comprises the following steps:
Figure BDA0003183649860000021
replacing a passive standard body with an active calibration device, the radar wavelength being lambda and the antenna gain being GdThe effective receiving area of the antenna of the active calibration equipment is Ad：
Figure BDA0003183649860000022
Actual link overall gain of GnWhen the radar emission signal irradiates the active calibration equipment to reflect the echo, the radar receives power Pr2Comprises the following steps:
Figure BDA0003183649860000031
let Pr1＝Pr2Then, there are:
Figure BDA0003183649860000032
further obtaining:
Figure BDA0003183649860000033
carrying out logarithm operation to obtain:
(σ)dBsm＝(Gn)dB+20log(λ)-10log(4π)。
preferably, the RCS of the measurement data is determined using a relative comparison method according to the radar equation, comprising the steps of: according to the radar equation, the radar receiving target echo power can be expressed as a function of a plurality of parameters of a target RCS, a transmitting coefficient, a receiving system and a propagation path, and the backscattering RCS is defined as follows when the airborne downward-looking measurement is carried out:
Figure BDA0003183649860000034
wherein p isrIs the received radar target echo power, ptIs the radar transmit power, G is the antenna gain in the target direction, λ is the radar wavelength, LtIs the transmission system loss factor, LrIs the loss factor, L, of the receiving systempIs the polarization loss factor, LmIs the loss factor on the propagation path, R is the distance from the radar antenna to the target; order:
Figure BDA0003183649860000035
then one can get:
Figure BDA0003183649860000036
using RCS of (sigma)dBsmThe active calibration device of (2) calibrates the airborne measurement system, order (sigma)dBsm＝σ0Then, there are:
Figure BDA0003183649860000041
in the formula, k0For active calibration of the constants k, p of the devicer0Calibrating the echo power of the device for reception; r0As a radarDistance of the antenna to the active calibration device; l ism0Is the loss factor on the then-current propagation path; the RCS of the measured object is calculated by the following formula:
Figure BDA0003183649860000042
expressed as the receiver output voltage:
Figure BDA0003183649860000043
preferably, the analyzing and measuring system calibrates the working scene and the corresponding index of the measuring system, and specifically includes: the method comprises the steps of distinguishing a main lobe signal and a side lobe signal aiming at a measurement radar transmitting signal, transmitting a calibration signal when the main lobe signal irradiates, and closing the functional requirement of an output channel at other moments.
Preferably, the analyzing and measuring system calibrates the working scene and the corresponding index of the measuring system, and specifically includes: in a receiving link of the active calibration equipment, power detection is added, and judgment is carried out according to the detection result; if the input threshold signal is larger than the input threshold signal, the received main lobe signal is considered, and the equipment works normally; if the side lobe of the radar is smaller than the input threshold signal and is considered to irradiate the equipment, the power amplification module is closed through the control module, and meanwhile, the switches of the receiving link and the transmitting link are closed.
Preferably, determining the receiving power range, the link gain and the device delay time of the active calibration device specifically includes: and (3) combing and measuring the working time sequence of the radar, analyzing the length of clutter echoes in a main lobe of the radar system, and enabling the delay time to be larger than the sum of the pulse width of the radar and clutter broadening.
In another aspect, the present invention provides an apparatus for airborne downward-looking measurement calibration using an active calibration device, including: the analysis and measurement module is used for analyzing a calibration working scene of the measurement system and corresponding indexes of the measurement system; the determining module is used for determining the receiving power range, the link gain and the equipment delay time of the active calibration equipment; the conversion module is used for determining the conversion relation between the link gain of the active calibration equipment and the RCS value of the passive standard body according to a radar equation; and the conversion module is used for determining the RCS of the measured data by applying a relative comparison method according to a radar equation.
Preferably, the analysis and measurement module is used for distinguishing a main lobe signal from a side lobe signal aiming at a measurement radar emission signal, emitting a calibration signal when the main lobe signal irradiates, and closing the functional requirement of an output channel at other moments; the determining module is used for combing and measuring the working time sequence of the radar, analyzing the length of clutter echoes in a main lobe of the radar system, and the delay time is longer than the sum of the pulse width and clutter broadening of the radar.
The method and the device for airborne downward-looking measurement calibration by using the active calibration equipment have the following beneficial effects that: the invention designs the active calibration equipment to replace the passive standard body by analyzing the calibration working scene of the airborne downward-looking measuring system and the corresponding indexes of the measuring system, thereby defining the specific indexes of the active calibration equipment and the corresponding relation between the link gain and the RCS value of the passive standard body, inhibiting the background clutter during calibration, improving the precision of airborne downward-looking measuring data, replacing the passive standard bodies with various specifications by the same active calibration equipment, having flexible external field application and important engineering application value.
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FIG. 1 is a schematic view of an airborne downward-looking measurement calibration;
FIG. 2 is a flow chart of a method of the present invention for airborne downward-looking measurement calibration using an active calibration device.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
FIG. 1 is a schematic view of an airborne downward-looking measurement calibration; FIG. 2 is a flow chart of a method of the present invention for airborne downward-looking measurement calibration using an active calibration device. As shown in fig. 1 and 2, one embodiment of the calibration method for airborne downward-looking measurement using an active calibration device of the present invention comprises the following steps:
step S01: analyzing a calibration working scene of the measuring system and corresponding indexes of the measuring system;
step S02: determining the receiving power range, the link gain and the equipment delay time of the active calibration equipment;
step S03: determining a conversion relation between the link gain of the active calibration equipment and the RCS value of the passive standard body according to a radar equation;
step S04: the RCS of the measurement data is determined using a relative comparison method according to the radar equation.
Determining that the active calibration equipment reflects an echo in a main lobe of a measuring radar, and preventing a measuring radar side lobe from detecting a target to cause a measuring error; the echo and the clutter of the active calibration equipment in the radar main lobe can be effectively distinguished in distance and power, so that the clutter is inhibited, and the calibration precision is improved.
In the embodiment of the calibration method for airborne downward-looking measurement by using active calibration equipment, the calibration working scene of the measurement system and the corresponding indexes of the measurement system are analyzed, and the method comprises the following steps: the method comprises the steps of measuring the flying height of an airplane, the flying speed, the beam width of an airborne radar antenna, the included angle between the beam direction of the radar antenna and the ground, radar working parameters, transmitting power, antenna gain and the main lobe and side lobe ratio of the antenna.
In the embodiment of the calibration method for airborne downward-looking measurement by using the active calibration equipment, the method for determining the receiving power range, the link gain and the equipment delay time of the active calibration equipment comprises the following steps: calculating the farthest distance and the nearest distance of a main lobe of a measuring radar reaching active calibration equipment according to an airborne downward-looking measuring calibration working scene, and calculating the receiving power range of the active calibration equipment; determining the link gain of the active calibration equipment according to the received power index and the equivalent passive standard magnitude of the equipment; and determining delay time according to the clutter echo length in the mainlobe in the calibration working scene of the measuring radar.
Receiving power of active calibration equipment and transmitting power P of measuring radartThe gain G of the transmitting antenna and the spatial transmission loss Los,
Los＝32.44+20*log(D)+20*log(F)；
wherein: d is the transmission distance in m; f is the working frequency in GHz; according to an airborne downward-looking measurement calibration working scene, the farthest and closest distances D of a main lobe of a measurement radar reaching active calibration equipment are calculated, and therefore the range of the receiving power Pin of the active calibration equipment is calculated: p ═ Pint+ G-Los. And determining the link gain of the active calibration equipment according to the receiving power index of the active calibration equipment and the RCS value of the equivalent passive standard body. And determining the signal delay time according to the clutter echo length in the mainlobe in the radar calibration working scene.
In the embodiment of the invention, the active calibration equipment is used for carrying out the calibration method of airborne downward-looking measurement, the conversion relation between the link gain of the active calibration equipment and the RCS value of the passive standard body is determined according to the radar equation, and the method comprises the following steps: the transmitting power of the airborne radar is PtAntenna transmission gain of GtThe effective receiving area of the antenna is AeIf RCS of the passive standard body is sigma, the distance from the radar antenna to the target is R, and the radar transmitting signal irradiates the passive standard body and is reflected back, then the radar receiving power Pr1Comprises the following steps:
Figure BDA0003183649860000071
replacing a passive standard body with an active calibration device, the radar wavelength being lambda and the antenna gain being GdThe effective receiving area of the antenna of the active calibration equipment is Ad：
Figure BDA0003183649860000072
Actual link overall gain of GnRadar emitting signal lightThe echo is reflected when the radar strikes the active calibration equipment, and then the power P is received by the radarr2Comprises the following steps:
Figure BDA0003183649860000073
let Pr1＝Pr2Then, there are:
Figure BDA0003183649860000074
further obtaining:
Figure BDA0003183649860000075
carrying out logarithm operation to obtain:
(σ)dBsm＝(Gn)dB+20log(λ)-10log(4π)；
to this end, the technical index of the active calibration device is determined. Because the active calibration equipment and the passive standard body have the same working scene, the transmitting signal of the airborne radar can be irradiated on the passive standard body, the reflected echo power is the same as the echo power irradiated on the active calibration equipment, and the RCS value (sigma) of the active calibration equipment is obtained by calculationdBsmAnd device link gain (G)n)dBAnd the relationship between the wavelengths lambda.
In the embodiment of the calibration method for airborne downward-looking measurement by using active calibration equipment, the RCS of the measured data is determined by using a relative comparison method according to a radar equation, and the method comprises the following steps: according to the radar equation, the radar receiving target echo power can be expressed as a function of a plurality of parameters of a target RCS, a transmitting coefficient, a receiving system and a propagation path, and the backscattering RCS is defined as follows when the airborne downward-looking measurement is carried out:
Figure BDA0003183649860000081
wherein p isrIs connected toReceived radar target echo power, ptIs the radar transmit power, G is the antenna gain in the target direction, λ is the radar wavelength, LtIs the transmission system loss factor, LrIs the loss factor, L, of the receiving systempIs the polarization loss factor, LmIs the loss factor on the propagation path, R is the distance from the radar antenna to the target; order:
Figure BDA0003183649860000082
then one can get:
Figure BDA0003183649860000083
calibration measurements using RCS of (sigma)dBsmThe active calibration device of (2) calibrates the airborne measurement system, order (sigma)dBsm＝σ0Then, there are:
Figure BDA0003183649860000084
in the formula, k0For active calibration of the constants k, p of the devicer0Calibrating the echo power of the device for reception; r0The distance from the radar antenna to the active calibration device; l ism0Is the loss factor on the then-current propagation path; when the airborne measurement radar is stable, the constant k can be considered to be k over a period of time0While atmospheric propagation during this time is considered relatively stable, i.e. Lm＝Lm0At this time, the RCS of the object to be measured is calculated by the following equation:
Figure BDA0003183649860000091
expressed as the receiver output voltage:
Figure BDA0003183649860000092
thus, a calibration method for airborne downward-looking measurements using active calibration equipment has been determined. According to a radar equation, by using a relative comparison method, the RCS of the measurement target is calculated through the output voltage value of the receiver when the airborne radar measures the target, the output voltage value of the receiver when the active calibration equipment is measured, the distance between the airborne radar and the measurement target and the distance between the airborne radar and the active calibration equipment when the airborne radar measures the target.
In the embodiment of the calibration method for airborne downward-looking measurement by using active calibration equipment, the calibration working scene of the measurement system and the corresponding indexes of the measurement system are analyzed, and the method specifically comprises the following steps: the method comprises the steps of distinguishing a main lobe signal and a side lobe signal aiming at a measurement radar transmitting signal, transmitting a calibration signal when the main lobe signal irradiates, and closing the functional requirement of an output channel at other moments.
In the embodiment of the calibration method for airborne downward-looking measurement by using active calibration equipment, the calibration working scene of the measurement system and the corresponding indexes of the measurement system are analyzed, and the method specifically comprises the following steps: in a receiving link of the active calibration equipment, power detection is added, and judgment is carried out according to the detection result; if the input threshold signal is larger than the input threshold signal, the received main lobe signal is considered, and the equipment works normally; if the side lobe of the radar is smaller than the input threshold signal and is considered to irradiate the equipment, the power amplification module is closed through the control module, and meanwhile, the switches of the receiving link and the transmitting link are closed.
In the embodiment of the calibration method for airborne downward-looking measurement by using active calibration equipment, the method for determining the receiving power range, the link gain and the equipment delay time of the active calibration equipment specifically comprises the following steps: and (3) combing and measuring the working time sequence of the radar, analyzing the length of clutter echoes in a main lobe of the radar system, and enabling the delay time to be larger than the sum of the pulse width of the radar and clutter broadening.
The embodiment of the invention also provides a device for airborne downward-looking measurement calibration by using the active calibration equipment, which comprises: the analysis and measurement module is used for analyzing a calibration working scene of the measurement system and corresponding indexes of the measurement system; the determining module is used for determining the receiving power range, the link gain and the equipment delay time of the active calibration equipment; the conversion module is used for determining the conversion relation between the link gain of the active calibration equipment and the RCS value of the passive standard body according to a radar equation; and the conversion module is used for determining the RCS of the measured data by applying a relative comparison method according to a radar equation. In the apparatus for performing airborne downward-looking measurement calibration by using active calibration equipment provided by this embodiment, the operations specifically executed by the analysis measurement module, the determination module, the conversion module, and the RCS determination module correspond to the steps in the method for performing airborne downward-looking measurement calibration by using active calibration equipment; for example, the analysis and measurement module is used for measuring the flying height of the airplane, the flying speed, the beam width of the airborne radar antenna, the included angle between the beam direction of the radar antenna and the ground, the radar working parameters, the transmitting power, the antenna gain and the main-lobe and side-lobe ratio of the antenna; for another example, the determining module is used for calculating the farthest distance and the nearest distance of a main lobe of the measuring radar reaching the active calibration equipment according to an airborne downward-looking measuring calibration working scene, calculating the receiving power range of the active calibration equipment, determining the link gain of the active calibration equipment according to the receiving power index and the equipment equivalent passive standard magnitude, and determining the delay time according to the clutter echo length in the main lobe in the measuring radar calibration working scene.
In the embodiment of the calibration device for airborne downward-looking measurement by using active calibration equipment, the analysis and measurement module is used for distinguishing the main lobe signal and the side lobe signal aiming at the signal transmitted by the measurement radar, transmitting the calibration signal when the main lobe signal irradiates, and closing the functional requirement of the output channel at other moments; the determining module is used for combing and measuring the working time sequence of the radar, analyzing the length of clutter echoes in a main lobe of the radar system, and the delay time is longer than the sum of the pulse width and clutter broadening of the radar.
The method and the device for airborne downward-looking measurement calibration by using the active calibration equipment have the following beneficial effects that: the invention designs the active calibration equipment to replace the passive standard body by analyzing the calibration working scene of the airborne downward-looking measuring system and the corresponding indexes of the measuring system, thereby defining the specific indexes of the active calibration equipment and the corresponding relation between the link gain and the RCS value of the passive standard body, inhibiting the background clutter during calibration, improving the precision of airborne downward-looking measuring data, replacing the passive standard bodies with various specifications by the same active calibration equipment, having flexible external field application and important engineering application value.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (10)

1. A method for airborne downward-looking measurement calibration using active calibration equipment, comprising the steps of:
analyzing a calibration working scene of the measuring system and corresponding indexes of the measuring system;
determining the receiving power range, the link gain and the equipment delay time of the active calibration equipment;
determining a conversion relation between the link gain of the active calibration equipment and the RCS value of the passive standard body according to a radar equation;
the RCS of the measurement data is determined using a relative comparison method according to the radar equation.
2. The method for airborne downward-looking measurement calibration by using active calibration equipment according to claim 1, wherein the analyzing of the calibration working scene of the measurement system and the corresponding indicators of the measurement system comprises the following steps:
the method comprises the steps of measuring the flying height of an airplane, the flying speed, the beam width of an airborne radar antenna, the included angle between the beam direction of the radar antenna and the ground, radar working parameters, transmitting power, antenna gain and the main lobe and side lobe ratio of the antenna.
3. The method of claim 1, wherein determining the active calibration device receive power range, link gain, and device delay time comprises:
calculating the farthest distance and the nearest distance of a main lobe of a measuring radar reaching active calibration equipment according to an airborne downward-looking measuring calibration working scene, and calculating the receiving power range of the active calibration equipment; determining the link gain of the active calibration equipment according to the received power index and the equivalent passive standard magnitude of the equipment; and determining delay time according to the clutter echo length in the mainlobe in the calibration working scene of the measuring radar.
4. The method of claim 1, wherein determining a scaling relationship between the link gain of the active calibration device and the RCS value of the passive standard according to radar equations comprises:
the transmitting power of the airborne radar is PtAntenna transmission gain of GtThe effective receiving area of the antenna is AeIf RCS of the passive standard body is sigma, the distance from the radar antenna to the target is R, and the radar transmitting signal irradiates the passive standard body and is reflected back, then the radar receiving power Pr1Comprises the following steps:
Figure FDA0003183649850000021
replacing a passive standard body with an active calibration device, the radar wavelength being lambda and the antenna gain being GdThe effective receiving area of the antenna of the active calibration equipment is Ad：
Figure FDA0003183649850000022
Actual link overall gain of GnThe radar transmits signals to the active calibration equipment to reflect echoes, and then the radar is connectedReceived power Pr2Comprises the following steps:
Figure FDA0003183649850000023
let Pr1＝Pr2Then, there are:
Figure FDA0003183649850000024
further obtaining:
Figure FDA0003183649850000025
carrying out logarithm operation to obtain:
(σ)dBsm＝(Gn)dB+20log(λ)-10log(4π)。
5. the method of claim 1 for airborne downward-looking measurement calibration using an active calibration device, wherein the determining the RCS of measurement data using a relative comparison method according to radar equations comprises the steps of:
according to the radar equation, the radar receiving target echo power can be expressed as a function of a plurality of parameters of a target RCS, a transmitting coefficient, a receiving system and a propagation path, and the backscattering RCS is defined as follows when the airborne downward-looking measurement is carried out:
Figure FDA0003183649850000026
wherein p isrIs the received radar target echo power, ptIs the radar transmit power, G is the antenna gain in the target direction, λ is the radar wavelength, LtIs the transmission system loss factor, LrIs the loss factor, L, of the receiving systempIs the polarization loss factor, LmIs a loss factor in the propagation path, R is thunderThe distance to the target from the antenna; order:
Figure FDA0003183649850000031
then one can get:
Figure FDA0003183649850000032
using RCS of (sigma)dBsmThe active calibration device of (2) calibrates the airborne measurement system, order (sigma)dBsm＝σ0Then, there are:
Figure FDA0003183649850000033
in the formula, k0For active calibration of the constants k, p of the devicer0Calibrating the echo power of the device for reception; r0The distance from the radar antenna to the active calibration device; l ism0Is the loss factor on the then-current propagation path; the RCS of the measured object is calculated by the following formula:
Figure FDA0003183649850000034
expressed as the receiver output voltage:
Figure FDA0003183649850000035
6. the method for airborne downward-looking measurement calibration by using active calibration equipment according to any one of claims 1-5, wherein analyzing the calibration working scene of the measurement system and the corresponding indexes of the measurement system specifically comprises:
the method comprises the steps of distinguishing a main lobe signal and a side lobe signal aiming at a measurement radar transmitting signal, transmitting a calibration signal when the main lobe signal irradiates, and closing the functional requirement of an output channel at other moments.
7. The method for airborne downward-looking measurement calibration by using active calibration equipment according to claim 6, wherein analyzing the calibration working scene of the measurement system and the corresponding indexes of the measurement system specifically comprises:
in a receiving link of the active calibration equipment, power detection is added, and judgment is carried out according to the detection result; if the input threshold signal is larger than the input threshold signal, the received main lobe signal is considered, and the equipment works normally; if the side lobe of the radar is smaller than the input threshold signal and is considered to irradiate the equipment, the power amplification module is closed through the control module, and meanwhile, the switches of the receiving link and the transmitting link are closed.
8. The method of claim 7, wherein the determining the active calibration device receive power range, link gain, and device delay time specifically comprises:
and (3) combing and measuring the working time sequence of the radar, analyzing the length of clutter echoes in a main lobe of the radar system, and enabling the delay time to be larger than the sum of the pulse width of the radar and clutter broadening.
9. An apparatus for airborne downward-looking measurement calibration using an active calibration device, comprising:
the analysis and measurement module is used for analyzing a calibration working scene of the measurement system and corresponding indexes of the measurement system;
the device comprises a determining module, a judging module and a control module, wherein the determining module is used for determining the receiving power range, the link gain and the device delay time of the active calibration device;
the conversion module is used for determining the conversion relation between the link gain of the active calibration equipment and the RCS value of the passive standard body according to a radar equation;
and the conversion module is used for determining the RCS of the measurement data by applying a relative comparison method according to a radar equation.
10. The apparatus of claim 9, wherein the analysis and measurement module is configured to distinguish a main lobe signal from a side lobe signal for a measurement radar emission signal, and to emit a calibration signal when the main lobe signal is illuminated, and to turn off an output channel function requirement at other times; the determining module is used for combing and measuring the working time sequence of the radar, analyzing the length of clutter echoes in a main lobe of the radar system, and the delay time is longer than the sum of the pulse width and clutter broadening of the radar.
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