CN114002665A - Equivalent far field RCS (radar cross section) testing method applying terahertz scaling measurement - Google Patents

Equivalent far field RCS (radar cross section) testing method applying terahertz scaling measurement Download PDF

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CN114002665A
CN114002665A CN202111649618.7A CN202111649618A CN114002665A CN 114002665 A CN114002665 A CN 114002665A CN 202111649618 A CN202111649618 A CN 202111649618A CN 114002665 A CN114002665 A CN 114002665A
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rcs
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CN114002665B (en
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胡伟东
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Beijing Institute of Technology BIT
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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
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/06—Systems determining position data of a target
    • G01S13/08—Systems for measuring distance only
    • G01S13/32—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
    • G01S13/34—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
    • G01S13/343—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal using sawtooth modulation
    • 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
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/06—Systems determining position data of a target
    • G01S13/08—Systems for measuring distance only
    • G01S13/32—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
    • G01S13/34—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
    • G01S13/345—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal using triangular modulation
    • 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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  • Remote Sensing (AREA)
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Abstract

The embodiment of the disclosure provides an equivalent far-field RCS test method applying terahertz scaling measurement, which comprises the following steps: calculating the classical far-field condition of the target according to the test frequency and the target size; calculating a proper target scaling ratio and a corresponding test frequency under the target scaling ratio by combining the test distance of the test site; processing a target scaling model according to the target scaling proportion; testing the scaling model by using a terahertz ultra-wideband radar to obtain RCS (radar cross section) under the condition of a scaling target far field; and according to the scaling principle, correcting the result to obtain the equivalent far-field target RCS under the actual test frequency. By the processing scheme, the distance measured by the RCS of the large target is remarkably reduced, and therefore cost is saved.

Description

Equivalent far field RCS (radar cross section) testing method applying terahertz scaling measurement
Technical Field
The invention belongs to the field of microwave measurement, and particularly relates to an equivalent far-field radar scattering cross section RCS (radar cross section) testing method applying a scaling principle.
Background
Radar detection becomes an indispensable detection means in modern society, and has wide application in military, navigation, weather, search and rescue and other fields. The physical quantity characterizing the echo intensity of a target under radar illumination is the Radar Cross Section (RCS). How to effectively evaluate the scattering cross section of the target radar is an important research direction in recent years, especially in the fields of stealth design and reverse stealth.
The radar electromagnetic scattering characteristic measurement technology mainly used for obtaining the radar scattering cross section has important reference value for stealth technology development. The electromagnetic scattering property measurement technique can be classified into a long-range technique and a short-range technique according to the measurement modeField measurements, near field measurements, and compact field measurements. Far field measurement (test distance needs to satisfy classical far field conditions
Figure 477495DEST_PATH_IMAGE001
D is the maximum size of the target, λ is the test wavelength) is performed outdoors or in a large darkroom, and the target RCS can be directly obtained, but the test distance requirement becomes too far away to be satisfied as the frequency increases or the target to be tested becomes larger. Near field measurements and compact field measurements in a microwave anechoic chamber are easier to meet test conditions since there are no specific requirements on the test distance. However, compact yards tend to be expensive, expensive to build, and the area for placing the test object (called the quiet zone) is small, making testing of large-sized objects impossible. The radar echo signal directly obtained by near-field full-scale test is not RCS concerned in engineering, a near-far field transformation technology is required, and corresponding transformation errors can be brought by various approximations of the algorithm in the process of using the algorithm.
There is therefore a need to develop methods that are short in test distance and easy to implement and that are capable of accurately testing a variety of targets. The scaling measurement principle is of great interest because of its easy implementation and the ability to accurately measure the radar cross-sectional area of the target.
The research on the scaling principle is started earlier internationally, and a mature scaling test theory is available at present. The scaling principle arises mainly due to the previously mentioned compact range test requirements. Due to the size limitation of the dead space, large targets up to tens of meters cannot be placed directly in the test area for scattering property testing, and the size of the targets needs to be scaled down to an acceptable level for testing. If this is done, the frequency of the test needs to be increased accordingly, which is the fundamental theory of the scaling principle. For the test with a large scale (usually more than 10 times), the actual emission frequency inevitably reaches the terahertz (electromagnetic field frequency is between 0.1THz and 10 THz) frequency band.
Disclosure of Invention
In view of the above, the invention provides an equivalent terahertz far-field testing method based on a scaling principle and an ultra-wideband testing device thereof, which can effectively reduce the field limitation of the traditional far-field testing method, simultaneously avoid using a compact field reflecting surface, and avoid errors caused by a near-far field transformation algorithm.
In a first aspect, the invention provides an equivalent far-field RCS testing method using terahertz scaling measurement, which includes:
calculating the classical far-field condition of the target according to the test frequency and the target size;
calculating a proper target scaling ratio and a corresponding test frequency under the target scaling ratio by combining the test distance of the test site;
processing a target scaling model according to the target scaling proportion;
testing the scaling model by using a terahertz ultra-wideband radar to obtain RCS (radar cross section) under the condition of a scaling target far field; and
and according to a scaling principle, correcting the result to obtain the equivalent far-field target RCS under the actual test frequency.
According to a specific implementation manner of the embodiment of the invention, the terahertz ultra-wideband radar is an ultra-wideband chirp continuous wave measurement radar which adopts sawtooth wave modulation or triangular wave modulation.
According to a specific implementation manner of the embodiment of the invention, the terahertz ultra-wideband radar comprises:
the device comprises a transmitting link and a receiving link, wherein the transmitting link and the receiving link adopt the same sweep frequency signal after power division; wherein
In the transmitting link, the frequency sweep signal is transmitted out by an antenna through a power amplification module after being subjected to 2n frequency multiplication;
in the receiving link, the frequency sweep signal is subjected to n frequency multiplication and then serves as local oscillator input of a second harmonic mixer, a signal reflected by a target serves as radio frequency input of the second harmonic mixer, two paths of signals generate a normalized intermediate frequency signal after mixing, and n is an integer.
According to a specific implementation manner of the embodiment of the invention, the method comprises the following steps:
the transmission chain transmits a continuous wave signal with a frequency linearly increasing with time:
Figure 198326DEST_PATH_IMAGE002
wherein
Figure 629307DEST_PATH_IMAGE003
Is the starting frequency of the sweep frequency signal, T is the sweep frequency repetition period,
Figure 929839DEST_PATH_IMAGE004
for the initial phase, k represents the chirp rate of the swept frequency signal, which is equal to the swept frequency bandwidth divided by the swept frequency repetition period:
Figure 28245DEST_PATH_IMAGE005
；
signal reflected back through target at distance R
Figure 123240DEST_PATH_IMAGE006
Can be expressed as:
Figure 41517DEST_PATH_IMAGE007
wherein
Figure 208056DEST_PATH_IMAGE008
The delay of the echo signal caused for the target,
Figure 131275DEST_PATH_IMAGE009
；
normalized intermediate frequency signal generated in the receiving chain
Figure 662751DEST_PATH_IMAGE010
：
Figure 68324DEST_PATH_IMAGE011
According to a specific implementation of an embodiment of the invention, the target specifies the frequencyf 1The following RCS response sampling instants are:
Figure 772975DEST_PATH_IMAGE012
whereinR 0The distance between the target center and the test radar, c the speed of light,
Figure 518077DEST_PATH_IMAGE013
in order to start the frequency of the frequency sweep signal,kis the slope of the swept frequency signal.
According to a specific implementation manner of the embodiment of the invention, the terahertz ultra-wideband radar is a frequency stepping radar and a vector network analyzer combined with a frequency doubling module.
According to a specific implementation manner of the embodiment of the present invention, after the step of testing the scaling model by using the terahertz ultra-wideband radar to obtain the RCS under the scaling target far-field condition, the method further includes: scaling the scaled data, comprising:
placing the calibration ball at the target position to obtain the calibration ball echo signal record under the same test parametersE r (t)；
Obtaining an echo signal of a targetE t (t)The RCS calculated by the calibration sphere is
Figure 282771DEST_PATH_IMAGE014
Then the calibration process is:
Figure 910061DEST_PATH_IMAGE015
wherein
Figure 356086DEST_PATH_IMAGE016
The scaled terahertz scaling RCS is obtained.
According to a specific implementation of the embodiment of the present invention, the target RCS is obtained by the following formula:
Figure 18012DEST_PATH_IMAGE017
wherein the content of the first and second substances,sis a scaling factor.
In a second aspect, the present invention provides an equivalent far-field RCS testing apparatus using terahertz scaling measurement, including:
the classical far-field condition calculation module is used for calculating the classical far-field condition of the target according to the test frequency and the target size;
the test frequency calculation module is used for calculating a proper target scale ratio and a corresponding test frequency under the target scale ratio by combining the test distance of a test site;
the target scaling model processing module is used for processing a target scaling model according to the target scaling proportion;
the RCS calculation module is used for testing the scaling model by utilizing the terahertz ultra-wideband radar under the scaling target far-field condition to obtain the RCS under the scaling target far-field condition; and
and the equivalent far-field target RCS calculation module is used for correcting the result according to the scaling principle to obtain the equivalent far-field target RCS under the actual test frequency.
In a third aspect, the present invention provides a computer-readable storage medium, which stores a computer program, which when executed on a processor implements the method for testing an equivalent far-field RCS using a terahertz scaling measurement according to any one of the first aspect and the specific implementation manner thereof.
Advantageous effects
1. The invention is a new concept of RCS test method for equivalent far field test under near field condition, and the large scale scaled model test is carried out by improving the frequency, so that the distance of large target RCS measurement can be obviously reduced, and the site cost is saved.
2. The test radar can adopt an ultra wide band linear frequency modulation continuous wave radar in design, can also adopt a step frequency continuous wave measuring device based on a double frequency module of a vector network analyzer, and has strong realizability.
3. The terahertz wave quasi-optical transmission device can utilize the quasi-optical transmission characteristic of terahertz waves and the characteristic of larger loss in space transmission, and in the field arrangement process, wave-absorbing materials do not need to be laid on all fields, only the part with larger scattering needs to be locally processed, and the test cost is further saved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings needed to be used in the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present disclosure, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a flow chart of the present invention;
FIG. 2 illustrates the difference between spherical waves and plane waves illuminating a target;
FIG. 3 is a schematic view of a test scene placement;
FIG. 4 is a diagram of an ultra-wideband frequency modulated continuous wave radar architecture;
FIG. 5 shows a signal pattern for testing scattering characteristics of an ultra-wideband frequency modulated continuous wave radar.
Detailed Description
The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.
The embodiments of the present disclosure are described below with specific examples, and other advantages and effects of the present disclosure will be readily apparent to those skilled in the art from the disclosure in the specification. It is to be understood that the described embodiments are merely illustrative of some, and not restrictive, of the embodiments of the disclosure. The disclosure may be embodied or carried out in various other specific embodiments, and various modifications and changes may be made in the details within the description without departing from the spirit of the disclosure. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict. All other embodiments, which can be derived by a person skilled in the art from the embodiments disclosed herein without making any creative effort, shall fall within the protection scope of the present disclosure.
It is noted that various aspects of the embodiments are described below within the scope of the appended claims. It should be apparent that the aspects described herein may be embodied in a wide variety of forms and that any specific structure and/or function described herein is merely illustrative. Based on the disclosure, one skilled in the art should appreciate that one aspect described herein may be implemented independently of any other aspects and that two or more of these aspects may be combined in various ways. For example, an apparatus may be implemented and/or a method practiced using any number of the aspects set forth herein. Additionally, such an apparatus may be implemented and/or such a method may be practiced using other structure and/or functionality in addition to one or more of the aspects set forth herein.
It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present disclosure, and the drawings only show the components related to the present disclosure rather than the number, shape and size of the components in actual implementation, and the type, amount and ratio of the components in actual implementation may be changed arbitrarily, and the layout of the components may be more complicated.
In addition, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the aspects may be practiced without these specific details.
The invention aims at different targets to be tested, respectively uses different scaling models and test radar frequency, and the method mainly comprises the following steps:
step one, calculating a classic far-field condition of a target according to a test frequency and a target size;
step two, calculating a proper target scaling ratio and a corresponding test frequency under the ratio by combining the test distance of the test site;
step three, processing a target scaling model according to the scaling proportion;
step four, testing the scaling model by utilizing a terahertz ultra-wideband radar to obtain RCS (radar cross section) under the condition of a scaling target far field;
and step five, correcting the result according to a scaling principle to obtain the equivalent far-field target RCS under the actual test frequency.
Further, the test site should meet the requirements of open site and low background scattering, and a target supporting device and a two-dimensional turntable need to be equipped.
Furthermore, the terahertz ultra-wideband radar can adopt an ultra-wideband chirp continuous wave radar and also can adopt a frequency stepping continuous wave radar.
The invention provides an equivalent far-field RCS testing method applying a scaling principle and a testing device matched with the method and having a frequency reaching a terahertz waveband. The core idea is to reduce the size of a test target in an equal proportion by a scaling principle, so that the classical far-field condition required by measurement is reduced, further the far-field test of the scaling target is realized at a closer test distance, and further the far-field test is equivalent to the far-field test of the original target to be tested. The specific flow of the process for realizing the conversion from the near-field test to the far-field test is shown in fig. 1.
In the definition of a radar scattering cross section, it is required that the target is at infinity from the radar, i.e., the target is under planar electromagnetic wave incidence conditions. The equiphase plane of the electromagnetic field is a plane perpendicular to the incident direction, but in practical situations, due to the limited test field and the limited antenna aperture of the test equipment, the electromagnetic wave actually emitted into the space is spherical. The pair of near field and far field illumination of the same object is shown in fig. 2.
Under the irradiation of spherical wave, the center point of the targetOPhase difference between it and its farthest position a perpendicular to the incident directionΔφCan be expressed askhThis is because the point A is farther from the transmitting antenna than the transmitting antennaOPoint and therefore phase lag behindOAnd (4) point. Whereas under ideal plane wave illumination this value is 0. This is also the most dominant source of near-field and far-field errors. By using the geometric relationship and combining Taylor series expansion, the following can be obtained:
Figure 688027DEST_PATH_IMAGE018
when the target maximum size is satisfieddFar less than twice the test distance2RIn the case of (2), the higher order terms in the taylor series can be approximately ignored, and the maximum phase difference can be expressed as:
Figure 5876DEST_PATH_IMAGE019
in the international test standard, it is customary to express the maximum phase difference allowed by the test as a fraction of π/4, i.e., π/4pWhen the specified maximum phase error is less than or equal to pi/8 (22.5 degrees), the difference between the target scattering characteristic data obtained by testing under the near-field condition and the RCS under the defined medium plane wave irradiation is smaller than 1dB in value. At this timep=2, there is a so-called "classical far field condition" which is widely accepted by the general public:
Figure 786750DEST_PATH_IMAGE020
it can be seen from the above equation that the classical far field condition of the target is inversely proportional to the test wavelength and directly proportional to the square of the target size.
According to the scaling principle, when the length l of an ideal conductive full-size target is reduced to be one-half of the original length s, if an RCS measurement curve with the same change trend as that before reduction is acquired, the test frequency is correspondingly increasedsMultiple times when the RCS tested thereby decreases in magnitude to the original 1 ≦ based ons 2 The fluctuation law is the same as the original RCS curve.
Further, according to the classical far field condition, the maximum size of the target to be measureddIs reduced tod/sAnd its test wavelength becomessλTherefore, according to the derivation process, the classical far-field condition required for testing is reduced to the original distancesOne of the results is that the effect of carrying out equivalent far field test in a shorter distance is achieved.
More specifically, the present invention is divided into the following steps:
step one, calculating the classic far-field condition of the target according to the test frequency and the target size:
measuring the maximum size of the target, and obtaining the transverse and longitudinal maximum size parameters of the target to be measured and recording the parameters asd. And calculating the classical far-field condition of the target in combination with the maximum frequency of the testR min . Specific examples are given in this specification: assume a target maximum dimension of 2.5 meters. And if the test frequency is 10GHz, the test distance required by the actual test is 416 m, and at the moment, if the scaling test or the near field test is not carried out, only a large test external field can be selected for testing.
Step two, calculating a proper scaling ratio and a corresponding test frequency under the scaling ratio by combining the test distance of the test site;
the length of the test microwave darkroom or open experimental field is L, and the test microwave darkroom or open experimental field is utilizedL/R min Estimating the minimum scaling factor required for the measurements min At this time, the measurement site is laid as shown in fig. 3. Assuming, by way of example in this specification, that the maximum test field length is limited to 20 meters, the scaling factor is a minimum of 20.8 times. And selecting the scaling factor of 21, and correspondingly increasing the test frequency to 210 GHz.
Step three, processing a target scaling metal model according to the scaling proportion;
since the target is often small, the processing cost can be controlled in a low range. And for the machining scaling model, the geometric model is not changed in shape and structural design and only changed in size, so that the model is relatively simple to construct. For the above example, a reduction target with a maximum dimension of 11.9 cm needs to be processed.
And step four, testing the scaling model by using the terahertz ultra-wideband radar to obtain the RCS under the terahertz frequency of the scaling target.
The invention designs the corresponding ultra wide band linear frequency modulation continuous wave measuring radar aiming at the problem of higher test frequency, and the method has the advantages of easy control of cost and capability of generating signals with ultrahigh bandwidth.
The modulation mode of the Linear Frequency Modulation Continuous Wave (LFMCW) radar mainly comprises sawtooth wave modulation and triangular wave modulation. The triangular wave can also obtain the target speed relative to the sawtooth wave modulation mode. In order to obtain the RCS of the target, the system has no radial relative speed between the object to be tested and the test system and no speed test requirement, so that a sawtooth wave modulation mode is adopted.
The main structure of the system is shown in fig. 4, the same microwave frequency sweeping source after power division is adopted by the transmitting link and the receiving link, so that the transmitting signal and the receiving signal keep coherent relation (have the same initial phase term), and coherent detection of the intermediate frequency signal can be realized. The frequency sweeping signal in the transmitting link is transmitted out by an antenna through a power amplification module after being subjected to 2n frequency multiplication; the same frequency sweeping signal in the receiving link is subjected to n frequency multiplication and then serves as a Local Oscillator (LO) input end of a second harmonic mixer, a signal reflected by a target serves as a Radio Frequency (RF) input end of the harmonic mixer, two paths of signals generate a Zero intermediate frequency (Zero-IF) signal after frequency mixing, and the Zero intermediate frequency (Zero-IF) signal is filtered, amplified and collected as an original signal to be processed.
The frequency sweep source and the frequency multiplication times n in the system can be selected according to actual test requirements and hardware cost, for example, assuming that the frequency required by the test is 130 GHz-220 GHz, n =6 is selected, and the bandwidth of the local oscillation frequency sweep source is 11.5 GHz-18.5 GHz. The system is designed and set up in such a way that the test requirements can be met.
The principle of RCS measurement by a linear frequency modulation continuous wave radar is as follows:
the system transmits a continuous wave signal with a frequency that increases linearly with time:
Figure 70226DEST_PATH_IMAGE002
wherein
Figure 114406DEST_PATH_IMAGE021
Is the starting frequency of the sweep frequency signal, T is the sweep frequency repetition period,
Figure 716288DEST_PATH_IMAGE022
for the initial phase, k represents the chirp rate of the swept frequency signal, which is equal to the swept frequency bandwidth divided by the swept frequency repetition period:
Figure 566433DEST_PATH_IMAGE005
。
echo signal reflected by target at distance R
Figure 140634DEST_PATH_IMAGE023
Can be expressed as:
Figure 152452DEST_PATH_IMAGE024
wherein
Figure 241631DEST_PATH_IMAGE025
The delay of the echo signal caused for the target,
Figure 833149DEST_PATH_IMAGE026
。
thereby obtaining a normalized intermediate frequency signal after mixing the target echo signal and the transmitting signal
Figure 58594DEST_PATH_IMAGE027
：
Figure 506893DEST_PATH_IMAGE028
It can be seen that the phase of the intermediate frequency signal is related to both the delay τ and the frequency.
Therefore, a high pitch slope (noted ask) The RCS test of fixed frequency point is realized, and the main principle is as shown in fig. 5. Assuming that the target center-to-center distance is the distance of the test radarR 0 According to
Figure 286630DEST_PATH_IMAGE029
Target echo time delay can be obtainedτWhereincIs the speed of light, and has a value of299792458 m/s. And (4) sampling by delaying tau after the emission signal starts to be emitted, wherein the sampled data is the electromagnetic scattering echo information of the target. Since the target itself is of negligible size compared to the test distance, as shown by the red dotted cluster in fig. 5. Meanwhile, the frequency modulation slope of the transmitted signal is very high, so that the second time delay is carried out after the time delay taut’The intermediate frequency data of the echo is sampled to obtainf 1=f 0+kt’RCS response of frequency bins.
Likewise, the target position to be measured can be utilizedR 0 And frequency point to be measuredf 1The sampling time is deduced reverselyt smp =τ+ t’. Which has the formula of
Figure 478577DEST_PATH_IMAGE030
And the RCS response under the target specified frequency can be obtained by sampling at the moment.
Besides the ultra-wideband linear frequency modulation continuous wave radar, the high-frequency terahertz RCS can be tested by adopting a frequency stepping radar and a vector network analyzer in combination with a frequency doubling module, and the cost is slightly increased.
And step five, scaling the scaling data.
The amplitude correspondence of the target under different frequencies can be obtained through the process, and the test result needs to be calibrated at the moment. The calibration method is a relative calibration method, after the target is tested, the metal calibration ball is placed at the target position, and the calibration ball echo data under the same test parameters are obtained. In the terahertz band, the RCS of a metal calibration sphere can be equivalent to the RCS of its optical zone:πr 2 whereinrIs the radius of the metal ball.
The echo signal of the metal ball is recordedE r (t)The echo signal of the target isE t (t)The RCS calculated for the metal ball is
Figure 71712DEST_PATH_IMAGE031
Then the calibration process is:
Figure 690912DEST_PATH_IMAGE032
wherein
Figure 692366DEST_PATH_IMAGE033
The scaled terahertz scaling RCS is obtained.
And step six, correcting the result according to a scaling principle to obtain the far-field target RCS under the actual test frequency.
After calibration, the accurate scaling RCS is obtainedσ’And obtaining the RCS of the target by using a scaling principle as follows:
Figure 688004DEST_PATH_IMAGE034
wherein the content of the first and second substances,sthe RCS unit at this time is dBsm for the scaling factor.
In addition, the invention also provides an equivalent far-field RCS testing device applying terahertz scaling measurement, which comprises:
the classical far-field condition calculation module is used for calculating the classical far-field condition of the target according to the test frequency and the target size;
the test frequency calculation module is used for calculating a proper target scale ratio and a corresponding test frequency under the target scale ratio by combining the test distance of a test site;
the target scaling model processing module is used for processing a target scaling model according to the target scaling proportion;
the RCS calculation module is used for testing the scaling model by utilizing the terahertz ultra-wideband radar under the scaling target far-field condition to obtain the RCS under the scaling target far-field condition; and
and the equivalent far-field target RCS calculation module is used for correcting the result according to the scaling principle to obtain the equivalent far-field target RCS under the actual test frequency.
The equivalent far-field RCS testing apparatus using terahertz scaling measurement corresponds to the method described above with reference to fig. 1 to 5, and is not described herein again.
In addition, the flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of apparatus, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
In addition, each functional module or unit in each embodiment of the present invention may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.
The functions, if implemented in the form of software functional modules and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention or a part of the technical solution that contributes to the prior art in essence can be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a smart phone, a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
The above description is only for the specific embodiments of the present disclosure, but the scope of the present disclosure is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present disclosure should be covered within the scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims.

Claims (10)

1. An equivalent far-field RCS test method applying terahertz scaling measurement is characterized by comprising the following steps:
calculating the classical far-field condition of the target according to the test frequency and the target size;
calculating a proper target scaling ratio and a corresponding test frequency under the target scaling ratio by combining the test distance of the test site;
processing a target scaling model according to the target scaling proportion;
testing the scaling model by using a terahertz ultra-wideband radar to obtain RCS (radar cross section) under the condition of a scaling target far field; and
and according to a scaling principle, correcting the result to obtain the equivalent far-field target RCS under the actual test frequency.
2. The equivalent far-field RCS testing method applying terahertz scaling measurement according to claim 1, characterized in that the terahertz ultra-wideband radar is an ultra-wideband chirp continuous wave measurement radar which adopts sawtooth wave modulation or triangular wave modulation.
3. The equivalent far-field RCS test method applying terahertz scaling measurement according to claim 1, wherein the terahertz ultra-wideband radar comprises:
the device comprises a transmitting link and a receiving link, wherein the transmitting link and the receiving link adopt the same sweep frequency signal after power division; wherein
In the transmitting link, the frequency sweep signal is transmitted out by an antenna through a power amplification module after being subjected to 2n frequency multiplication;
in the receiving link, the frequency sweep signal is subjected to n frequency multiplication and then serves as local oscillator input of a second harmonic mixer, a signal reflected by a target serves as radio frequency input of the second harmonic mixer, two paths of signals generate a normalized intermediate frequency signal after mixing, and n is an integer.
4. The equivalent far-field RCS test method applying terahertz scaling measurement according to claim 3, characterized in that the method comprises:
the transmission chain transmits a continuous wave signal with a frequency linearly increasing with time:
Figure 291560DEST_PATH_IMAGE001
wherein
Figure 81661DEST_PATH_IMAGE002
Is the starting frequency of the sweep frequency signal, T is the sweep frequency repetition period,
Figure 570412DEST_PATH_IMAGE003
for the initial phase, k represents the chirp rate of the swept frequency signal, which is equal to the swept frequency bandwidth divided by the swept frequency repetition period:
Figure 838582DEST_PATH_IMAGE004
；
signal reflected back through target at distance R
Figure 158705DEST_PATH_IMAGE005
Can be expressed as:
Figure 322970DEST_PATH_IMAGE006
wherein
Figure 319921DEST_PATH_IMAGE007
The delay of the echo signal caused for the target,
Figure 391782DEST_PATH_IMAGE008
；
normalized intermediate frequency signal generated in the receiving chain
Figure 566411DEST_PATH_IMAGE009
：
Figure 698315DEST_PATH_IMAGE010
。
5. The equivalent far-field RCS test method using terahertz scaling measurement as claimed in claim 4, wherein the target specifies frequencyf 1The following RCS response sampling instants are:
Figure 161658DEST_PATH_IMAGE011
whereinR 0The distance between the target center and the test radar, c the speed of light,
Figure 37210DEST_PATH_IMAGE012
in order to start the frequency of the frequency sweep signal,kis the slope of the swept frequency signal.
6. The equivalent far-field RCS testing method applying terahertz scaling measurement according to claim 1, wherein the terahertz ultra-wideband radar is a frequency stepping radar and a vector network analyzer combined with a frequency doubling module.
7. The equivalent far-field RCS testing method using terahertz scaling measurement according to claim 1, wherein after the step of testing the scaling model using the terahertz ultra-wideband radar to obtain RCS under the scaling target far-field condition, the method further comprises: scaling the scaled data, comprising:
placing the calibration ball at the target position to obtain the calibration ball echo signal record under the same test parametersE r (t)；
Obtaining an echo signal of a targetE t (t)The RCS calculated by the calibration sphere is
Figure 269608DEST_PATH_IMAGE013
Then the calibration process is:
Figure 306834DEST_PATH_IMAGE014
wherein
Figure 319789DEST_PATH_IMAGE015
The scaled terahertz scaling RCS is obtained.
8. The equivalent far-field RCS testing method using terahertz scaling measurement according to claim 7, wherein the RCS of the target is obtained by:
Figure 936716DEST_PATH_IMAGE016
wherein the content of the first and second substances,sis a scaling factor.
9. An equivalent far-field RCS testing device applying terahertz scaling measurement is characterized by comprising:
the classical far-field condition calculation module is used for calculating the classical far-field condition of the target according to the test frequency and the target size;
the test frequency calculation module is used for calculating a proper target scale ratio and a corresponding test frequency under the target scale ratio by combining the test distance of a test site;
the target scaling model processing module is used for processing a target scaling model according to the target scaling proportion;
the RCS calculation module is used for testing the scaling model by utilizing the terahertz ultra-wideband radar under the scaling target far-field condition to obtain the RCS under the scaling target far-field condition; and
and the equivalent far-field target RCS calculation module is used for correcting the result according to the scaling principle to obtain the equivalent far-field target RCS under the actual test frequency.
10. A computer-readable storage medium, characterized in that it stores a computer program which, when executed on a processor, implements the equivalent far-field RCS test method applying terahertz scaling measurements of any one of claims 1 to 8.
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115586542A (en) * 2022-11-28 2023-01-10 中国人民解放军国防科技大学 Remote terahertz single photon radar imaging method and device based on scaling training
CN117630511A (en) * 2024-01-25 2024-03-01 北京理工大学 Equivalent far-field RCS measurement method and system based on Longber lens antenna

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102608591A (en) * 2012-03-30 2012-07-25 西北工业大学 RCS (revision control system) extrapolation method based on phase correction
WO2017216942A1 (en) * 2016-06-17 2017-12-21 株式会社日立製作所 Terahertz wave measuring device
CN111474554A (en) * 2020-04-13 2020-07-31 中国人民解放军国防科技大学 Terahertz frequency band single photon radar system and target detection method thereof
CN112083413A (en) * 2019-06-13 2020-12-15 北京测威科技有限公司 Radar wave stealth weapon equipment maintenance test method

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102608591A (en) * 2012-03-30 2012-07-25 西北工业大学 RCS (revision control system) extrapolation method based on phase correction
WO2017216942A1 (en) * 2016-06-17 2017-12-21 株式会社日立製作所 Terahertz wave measuring device
CN112083413A (en) * 2019-06-13 2020-12-15 北京测威科技有限公司 Radar wave stealth weapon equipment maintenance test method
CN111474554A (en) * 2020-04-13 2020-07-31 中国人民解放军国防科技大学 Terahertz frequency band single photon radar system and target detection method thereof

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
钟晓语: "太赫兹雷达目标特征及杂波特征研究", 《万方学术期刊数据库》 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115586542A (en) * 2022-11-28 2023-01-10 中国人民解放军国防科技大学 Remote terahertz single photon radar imaging method and device based on scaling training
CN115586542B (en) * 2022-11-28 2023-03-03 中国人民解放军国防科技大学 Remote terahertz single photon radar imaging method and device based on scaling training
CN117630511A (en) * 2024-01-25 2024-03-01 北京理工大学 Equivalent far-field RCS measurement method and system based on Longber lens antenna
CN117630511B (en) * 2024-01-25 2024-04-05 北京理工大学 Equivalent far-field RCS measurement method and system based on Longber lens antenna

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