CN110687510B - High-temperature target RCS test calibration method - Google Patents
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- 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
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Abstract
The invention relates to a high-temperature target RCS test calibration method, one embodiment of the method comprises the following steps: collecting echo level data of a calibration body in a normal temperature state, and collecting echo level data of an empty room in the normal temperature state; heating a target to be detected to a specified temperature, and acquiring echo level data of the target to be detected; and calculating RCS data of the target to be detected according to the calibration body echo level data, the empty room echo level data, the echo level data of the target to be detected and predetermined calibration body theoretical RCS data. The embodiment can realize the rapid test calibration of the high-temperature target RCS.
Description
Technical Field
The invention relates to the technical field of RCS (Radar Cross section) tests, in particular to a high-temperature target RCS test calibration method.
Background
Temperature changes of different degrees can occur in certain parts of the aircraft during flight, such as the head part, the air inlet channel, the tail nozzle and the like of the high-speed aircraft. With the requirement for stealth performance becoming higher and higher, it becomes more and more important to obtain the change of stealth performance of a target in a high temperature state. For the stealth performance test of the target in a high-temperature state, domestic unit researches basically focus on the aspects of high-temperature material parameter and reflectivity tests, the high-temperature RCS test research of the stealth target is started, and a standard test calibration method does not exist. According to the calibration method of the target RCS test under the normal temperature state, the test under the high temperature state generally comprises the steps of calibrating and cooling a high temperature standard body, and then heating the target test. The disadvantage of this approach is that the high temperature standard body calibration heating time is long resulting in low test efficiency.
Disclosure of Invention
The technical problem to be solved by the invention is how to test the radar scattering Cross section RCS (radar Cross section) of the high-temperature target.
In order to solve the technical problem, the invention provides a high-temperature target RCS test calibration method.
The high-temperature target RCS test calibration method provided by the invention comprises the following steps: collecting echo level data of a calibration body in a normal temperature state, and collecting echo level data of an empty room in the normal temperature state; heating a target to be detected to a specified temperature, and acquiring echo level data of the target to be detected; and calculating RCS data of the target to be detected according to the calibration body echo level data, the empty room echo level data, the echo level data of the target to be detected and predetermined calibration body theoretical RCS data.
Optionally, calculating RCS data of the target to be measured according to the calibration body echo level data, the empty room echo level data, the echo level data of the target to be measured, and predetermined calibration body theoretical RCS data, including: the RCS data of the object to be measured is calculated using the following formula:
x＝x0(U2-U0)/(U1-U0)
wherein x is RCS data of the target to be detected, x0For the calibration volume theoretical RCS data, U0For the room echo level data, U1For the calibration volume echo level data, U2And the echo level data of the target to be detected is obtained.
Optionally, the method further comprises: after the echo level data of the target to be detected is acquired, background cancellation and time domain gating based on a predetermined first time domain gate function are performed on the echo level data of the target to be detected.
Optionally, the method further comprises: after the echo level data of the calibration body in the normal temperature state are collected and the echo level data of the empty room in the normal temperature state are collected, the echo level data of the calibration body in the normal temperature state are obtained to calculate the RCS of the calibration body, and the calculated RCS of the calibration body is compared with the theoretical RCS of the calibration body so as to verify the precision of the test system.
Optionally, the method further comprises: after echo level data for calculating the calibration volume RCS is acquired, background cancellation and time domain gating based on a predetermined second time domain gate function are performed on the echo level data.
Optionally, the method further comprises: after the precision of the test system is verified to pass the preset requirement, acquiring room echo level data in a normal temperature state, and executing background cancellation and time domain gating based on a predetermined third time domain gate function on the room echo level data to obtain equivalent background level data; and when the equivalent background level data meet the preset condition, executing the step of heating the target to be measured.
Optionally, the preset requirement is: the difference between the calculated target RCS and the target theoretical RCS is less than 0.5 dB.
Optionally, the precondition is: the difference between the calibration volume echo level data and the equivalent background level data is greater than 20 dB.
Optionally, the first time domain gate function, the second time domain gate function, and the third time domain gate function are all rectangular gate functions subjected to smoothing processing.
Optionally, the calibration body is a metal ball, a metal cylinder or a metal cube.
The invention discloses a test calibration method for RCS of a high-temperature target, which solves the problem of accurate calibration of RCS test of the target in a high-temperature state. The metal ball, the metal cylinder, the metal cube and the like have accurate theoretical values and are usually used as standard bodies to perform a calibration function in a target RCS test, so the test precision of the metal ball, the metal cylinder, the metal cube and the like is directly related to the accuracy of target test data. The research on the RCS testing technology of domestic high-temperature targets is just started, a standard testing and calibrating method is not available, and the heating time is long and the efficiency is low by adopting the existing high-temperature standard body calibrating mode. The invention can adopt a method for calibrating a standard metal ball with the diameter of 200mm in a normal temperature state, firstly, the analysis of the temperature field of a high-temperature target finds that the amplitude-phase distribution of a surrounding electromagnetic field can change after the target is heated, then echo data of the standard metal ball in the normal temperature state is obtained through a test and is used as calibration data, then the echo data is used as the target to select a plurality of temperature points in the process of heating the target from the room temperature to 800 ℃ for RCS test, the high-temperature RCS data of the standard body is obtained, and the result analysis can find that the RCS change of the metal ball with the diameter of 200mm in the process of temperature change is only within 0.5 dB. Therefore, the influence of the temperature within 800 ℃ on the test of the standard body is small, and a method for calibrating the target at normal temperature can be adopted during the high-temperature RCS test of the target, so that the efficiency of the high-temperature RCS test of the target can be effectively improved. Finally, the invention collects the echo level data of the calibration body and the echo level data of the empty room in the normal temperature state as the calibration data to calibrate the obtained echo level data of the high-temperature target, thereby quickly calculating the RCS of the target and overcoming the defect of lower efficiency caused by heating the calibration body in the prior art.
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FIG. 1 is a schematic diagram of the main steps of the high temperature target RCS test calibration method according to the embodiment of the present invention;
FIG. 2 is a schematic diagram of a comparison curve between a normal temperature test value and a theoretical value of a calibration body RCS;
FIG. 3 is a graph showing the comparison between the normal temperature and the high temperature of the background RCS;
FIG. 4 is a schematic representation of the RCS versus temperature curve for the calibration body at different temperature conditions;
fig. 5 is a schematic diagram of specific implementation steps of the high-temperature target RCS test calibration method according to the embodiment of the present invention.
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.
The present invention is directed to testing RCS data for high temperature targets. In an actual scene, a temperature field around a high-temperature target is obviously different from a normal temperature, and according to a thermal diffusion equation, the air temperature of different positions in a space caused by the high-temperature target can be determined, so that the air distribution of different space positions can be calculated. Since the air in a real test field is a mixture of various gases and impurities, this non-uniform distribution can be equated to a sphere of media with different electromagnetic parameters, only related to spatial distance. The electromagnetic field is transmitted in a series of layered media to generate refraction and reflection, so that the amplitude and phase of the electromagnetic wave can be changed when the electromagnetic wave passes through different temperature layers, and the air layers at different temperatures cause scattering background noise, and the background noise inevitably affects the test of a high-temperature target.
Fig. 1 is a schematic diagram of main steps of a high-temperature target RCS test calibration method according to an embodiment of the present invention. As shown in fig. 1, the high temperature target RCS test calibration method according to the embodiment of the present invention may be executed according to the following steps:
step S101: and acquiring echo level data of the calibration body in a normal temperature state, and acquiring echo level data of the empty room in the normal temperature state.
In the embodiment of the invention, the frequency sweep test can be carried out in the frequency range of 2GHz to 18 GHz. The calibration body may be a metal ball, a metal cylinder or a metal cube. In the following description, a metal ball having a diameter of 200mm will be described as an example. In this step, echo level data (for example, echo voltage data) of the calibration body in the normal temperature state may be collected first, and then the calibration body is taken off from the support to collect echo level data of the empty room (the support may be set in the empty room) in the normal temperature state, and these two kinds of echo data will be used as calibration data for the subsequent calculation of the RCS of the target to be measured.
As a preferred scheme, after step S101, the echo level data of the calibration body in the normal temperature state may be acquired to calculate the calibration body RCS, and the calculated calibration body RCS is compared with the calibration body theoretical RCS to verify the accuracy of the test system. In practical application, if the calculated difference value between the calibration body RCS and the calibration body theory RCS is less than 0.5dB, the test system has better precision, and the subsequent steps can be executed; and if the calculated difference value between the calibration body RCS and the calibration body theory RCS is not less than 0.5dB, the accuracy of the test system cannot meet the requirement, and the subsequent steps need to be stopped. Preferably, after the volume echo level data is scaled, background cancellation (i.e., removal of background signals in the echo level data) and time domain gating based on a predetermined second time domain gate function may be performed on the echo level data to eliminate clutter effects outside the target region. It can be understood that, when performing time domain gating, the echo level signal may be first transformed to the time domain, then the transformed time domain signal is multiplied by the second time domain gate function, and finally the result of the multiplication is transformed to the frequency domain, i.e. time domain gating is completed.
Fig. 2 is a schematic diagram of a comparison curve between the normal temperature test value and the theoretical value of the calibration body RCS, in fig. 2, the curve with higher gray scale is the test value of the calibration body RCS, and the curve with lower gray scale is the theoretical value. As can be seen in FIG. 2, the difference is less than 0.5dB (i.e., dBsm, which represents dB square meters, which represents a system accuracy of 0.5dB)
In some embodiments, after the accuracy of the test system is verified to meet the preset requirement, room echo level data in a normal temperature state may be obtained, and background cancellation and time domain gating based on a predetermined third time domain gate function (the first time domain gate function, the second time domain gate function, and the third time domain gate function may all be rectangular gate functions that are subjected to smoothing) may be performed on the room echo level data, so as to obtain equivalent background level data. If the equivalent background level data meets the preset condition (for example, the difference value between the calibration body echo level data and the equivalent background level data is more than 20 dB.), the subsequent steps can be executed, and if the equivalent background level data does not meet the condition, the subsequent steps are stopped.
In the embodiment of the invention, the air in the target area can be heated to 500 ℃ at the moment, and the equivalent background level data under various high-temperature conditions can be obtained by adopting the test method which is the same as the normal temperature for many times. FIG. 3 is a graph showing a comparison curve between a normal temperature state and a high temperature state of background RCS, wherein a plurality of curves having a lower gray level and a larger RCS (i.e., curves having RCS greater than-60 dBsm at 9 GHz) correspond to the high temperature state, and a plurality of curves having a higher gray level and a smaller RCS (i.e., curves having RCS less than-60 dBsm at 9 GHz) correspond to the low temperature state. It can be seen that the background equivalent RCS increases significantly after the target zone air is heated.
As a preferred option, the change of the calibration body RCS under different temperature conditions can be tested at this time. Specifically, a metal ball with a diameter of 200mm can be heated to 300 ℃, 400 ℃, 500 ℃ and 800 ℃ respectively to test the RCS value, and a background cancellation and time domain gating method can be adopted after calibration, so that the RCS under different temperature conditions can be obtained finally. Fig. 4 is a schematic diagram of RCS contrast curves of the calibration body under different temperature conditions, and in fig. 4, curves of different gray scales represent RCS under different temperature conditions. It can be seen that the RCS is basically unchanged under different temperature conditions, with a maximum deviation of 0.3dBsm, since the background cancellation and software gating method is used to suppress the clutter effect caused by high temperature gas outside the target area. Therefore, the high temperature basically has no influence on the RCS test of the standard metal ball, so that the calibration of the high-temperature target RCS test can adopt the calibration data in the normal temperature state.
Step S102: and after the target to be measured is heated to the specified temperature, acquiring echo level data of the target to be measured.
The specified temperature may be any temperature higher than room temperature. In this step, echo level data of the high temperature target may be acquired for RCS calculation. After the echo level data is acquired, background cancellation and time domain gating based on a predetermined first time domain gate function can be performed on the echo level data of the target to be detected to suppress background clutter.
Step S103: and calculating RCS data of the target to be detected according to the calibration body echo level data, the empty room echo level data, the echo level data of the target to be detected and predetermined calibration body theoretical RCS data.
In this step, the RCS data of the target to be measured may be calculated using the following formula:
x＝x0(U2-U0)/(U1-U0)
wherein x is RCS data of the target to be detected, x0For the calibration volume theoretical RCS data, U0For the room echo level data, U1For the calibration volume echo level data, U2And the echo level data of the target to be detected is obtained.
Fig. 5 is a schematic diagram of specific implementation steps of the high-temperature target RCS test calibration method according to the embodiment of the present invention, and shows a detailed flow of the method according to the present invention in an actual scene. Wherein, the determining whether the signal-to-noise ratio is satisfied may be determining whether a difference between the calibration volume echo level data and the equivalent background level data is greater than 20 dB.
Through the arrangement, the rapid test calibration of the high-temperature target RCS can be realized.
In summary, in the embodiment of the present invention, the echo level data of the calibration object at the normal temperature and the echo level data of the empty room are collected as calibration data to calibrate the echo level data of the obtained high-temperature target, so as to quickly calculate the target RCS, and overcome the defect of low efficiency caused by the need of heating the calibration object in the prior art. In addition, the influence of background on eliminating the echo level data outside the target area can be eliminated by adopting a background pair elimination software gate technology, so that the testing efficiency can be effectively improved.
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 (3)
1. A high-temperature target RCS test calibration method is characterized by comprising the following steps:
collecting echo level data of a calibration body in a normal temperature state, and collecting echo level data of an empty room in the normal temperature state;
obtaining echo level data of a calibration body in a normal temperature state to calculate a calibration body RCS, and comparing the calculated calibration body RCS with a calibration body theory RCS so as to verify the precision of the test system; after echo level data used for calculating a calibration body RCS is obtained, background cancellation and time domain gating based on a second predetermined time domain gate function are carried out on the echo level data;
after the precision of the test system is verified to pass the preset requirement, acquiring room echo level data in a normal temperature state, and executing background cancellation and time domain gating based on a predetermined third time domain gate function on the room echo level data to obtain equivalent background level data; the preset requirements are as follows: the difference value between the calculated calibration body RCS and the calibration body theory RCS is less than 0.5 dB;
when the equivalent background level data meet the preset condition, executing the step of heating the target to be measured; the pre-conditions are as follows: the difference value between the echo level data of the calibration body and the equivalent background level data is more than 20 dB;
heating a target to be detected to a specified temperature, acquiring echo level data of the target to be detected, and executing background cancellation and time domain gating based on a predetermined first time domain gate function on the echo level data of the target to be detected;
calculating RCS data of the target to be measured according to the calibration body echo level data, the empty room echo level data, the echo level data of the target to be measured and predetermined calibration body theoretical RCS data, wherein the RCS data comprises the following steps:
the RCS data of the object to be measured is calculated using the following formula:
x＝x0(U2-U0)/(U1-U0)
wherein x is RCS data of the target to be detected, x0For the calibration volume theoretical RCS data, U0For the room echo level data, U1For the calibration volume echo level data, U2And the echo level data of the target to be detected is obtained.
2. The method of claim 1, wherein the first time domain gate function, the second time domain gate function, and the third time domain gate function are smoothed rectangular gate functions.
3. The method of any of claims 1-2, wherein the calibration body is a metal sphere, a metal cylinder, or a metal cube.
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| JP3319242B2 (en) * | 1995-09-18 | 2002-08-26 | 三菱電機株式会社 | Radar equipment |
| CN102998665B (en) * | 2012-11-23 | 2014-08-27 | 北京航空航天大学 | Target radar cross section measuring and calibrating processing method |
| CN104635222B (en) * | 2015-03-05 | 2017-03-01 | 北京航空航天大学 | A kind of background extracting in low detectable target rcs measurement and cancellation processing method |
| CN105044729A (en) * | 2015-06-30 | 2015-11-11 | 北京师范大学 | Raman scattering laser radar used for aircraft detection |
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| CN105242250B (en) * | 2015-11-25 | 2017-11-24 | 北京机电工程研究所 | A kind of robot scaling equipment towards extremely low RCS target measurements |
| CN105891795B (en) * | 2016-05-23 | 2018-01-16 | 北京环境特性研究所 | A kind of dual station rcs measurement calibrating method |
| CN106154240A (en) * | 2016-06-20 | 2016-11-23 | 西北工业大学 | A kind of polarization scattering matrix Fast measurement system and method |
| CN107153179B (en) * | 2017-05-26 | 2019-11-22 | 中国电子科技集团公司第四十一研究所 | A kind of radar target RCS and scattering center synchronous detecting method |
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