CN112114311B - Nondestructive detection method based on terahertz vortex electromagnetic waves - Google Patents

Nondestructive detection method based on terahertz vortex electromagnetic waves Download PDF

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CN112114311B
CN112114311B CN202010850700.5A CN202010850700A CN112114311B CN 112114311 B CN112114311 B CN 112114311B CN 202010850700 A CN202010850700 A CN 202010850700A CN 112114311 B CN112114311 B CN 112114311B
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李财品
段崇棣
李升远
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Xian Institute of Space Radio Technology
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    • 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 discloses a nondestructive detection method based on terahertz vortex electromagnetic waves, which can break through the traditional real aperture imaging resolution under the condition of small transverse relative motion between a radar and a target, improve the angle resolution of the radar to a certain extent and solve the problem of low resolution of the conventional real aperture radar equipment. The method comprises the following implementation steps: 1. and selecting a terahertz frequency band as a frequency band of a nondestructive testing technology. 2. And generating a terahertz microwave signal. 3. And determining the vortex electromagnetic wave emission mode and the number of the antennas. 4. An annular array configuration is determined. 5. And calculating different mode modulation excitation phases of the antenna to generate vortex electromagnetic waves. 6. And irradiating the detected object by utilizing the terahertz vortex electromagnetic wave. 7. And receiving the echo signal of the detected object. 8. And performing data inversion and imaging according to the detection requirement.

Description

Nondestructive detection method based on terahertz vortex electromagnetic waves
Technical Field
The invention belongs to the technical field of radars, and further relates to a nondestructive detection method based on terahertz vortex electromagnetic waves, which can break through the traditional real-aperture imaging resolution under the condition that the transverse relative motion between a radar and a target is very small or the target is relatively static, improve the angle resolution of the radar to a certain extent, and solve the problem that the existing real-aperture radar is not high in resolution.
Background
The terahertz vortex electromagnetic wave nondestructive testing technology is derived from a fund project in the field of equipment development department, and the terahertz frequency band and the electromagnetic wave are combined to have an important application scene in the material nondestructive testing technology, so that the problems of damage to target detection and low resolution caused by a conventional radar are hopefully solved.
The conventional radar frequency band such as L \ S \ C \ X \ Ku \ Ka and other frequency bands easily cause damage to dielectric materials and semiconductor materials, so that the conventional radar frequency band is not suitable for being used as the frequency band for nondestructive detection of the vortex electromagnetic wave radar. The terahertz wave is utilized to have good penetrating capability on most dry, non-metal and non-polar materials (such as foam, ceramic, glass, resin, paint, rubber, composites and the like), and various imaging technologies are combined to detect defects in the materials. Nondestructive testing is becoming one of the major applications of terahertz technology. As a novel sub-surface quantitative detection technology, terahertz nondestructive detection is widely applied to detection of various materials and structures such as a heat-proof material of an external fuel tank of a space plane, a foam sandwich radar antenna housing plate and the like. The vortex electromagnetic wave is an electromagnetic wave carrying orbital angular momentum and having a vortex-shaped phase plane. Since the vortex electromagnetic wave has a unique distribution in space, when it is irradiated onto a target, it is incident from a plurality of angles equivalent to a conventional plane wave, and thus has a unique advantage in spatial information collection. Because the equiphase surface of the radar system is changed along with the number of the modes, multidimensional space sampling can be realized in a short time by traversing the number of the modes, and the radar system has more advantages in the aspect of space information collection compared with the existing radar system. The completely new information dimension and the specific propagation mode provided by the orbital angular momentum can enable people to obtain more information about the target, and the completely new possibility is provided for the breakthrough of the future radar detection and imaging field.
Under the irradiation of vortex electromagnetic waves, signals in a detection area have remarkable spatial fluctuation characteristics, electromagnetic excitation with difference distribution is formed at different targets with the same distance in a wave beam, and therefore decoupling and super-resolution processing of information can be performed. Therefore, the vortex electromagnetic wave radar can break through the traditional real aperture imaging resolution under the condition that the transverse relative motion between the radar and the target is very small, improve the angle resolution of the radar to a certain extent and solve the problem that the existing real aperture radar is not high in resolution. In addition, for the vortex electromagnetic wave radar, the vortex electromagnetic wave radar has the capability of three-dimensional imaging due to the fact that the vortex electromagnetic wave radar carries orbital angular momentum and has a coupling relation with a target. Therefore, the method has an important application scene in the nondestructive testing of aerospace composite materials. At present, no public report is found for the research of the nondestructive testing technology based on the terahertz vortex electromagnetic wave.
Disclosure of Invention
The invention solves the problems that: the method overcomes the defects of the prior art, and provides a nondestructive detection method based on terahertz vortex electromagnetic waves, which can break through the traditional real aperture imaging resolution under the condition that the transverse relative motion between a radar and a target is very small or is relatively static, improve the angle resolution of the radar to a certain extent, and solve the problem that the existing real aperture radar is not high in resolution.
The technical scheme of the invention is as follows: a nondestructive detection method based on terahertz vortex electromagnetic waves comprises the following steps:
step 1, selecting a terahertz frequency band as a frequency band of a nondestructive testing technology;
step 2, generating a baseband signal by a signal source, and outputting a radio frequency signal of a terahertz frequency band in a specified frequency band range after the transmitter performs quadrature modulation, frequency multiplication and filtering amplification on the baseband signal; the power amplifier pre-amplifies the power of the radio frequency signal output by the transmitter to obtain an amplified radio frequency signal;
step 3, determining the emission mode l of vortex electromagnetic waves1,l2,…,lMWherein M is the number of modes; according to the determined emission mode, the maximum mode number | l is calculated according to the absolute valuem|maxDetermining the number N of the loop array antennas as a reference;
step 4, arranging the annular array antennas according to the annular array radius a;
step 5, obtaining the system emission mode l according to the step 31,l2,…,lMRange, corresponding phase weighting of the antenna, calculating the l-th of the n-th loop array antennamModally modulated excitation phase wn,m；
Step 6, exciting by utilizing the phase modulation obtained in the step 5 and the amplified radio frequency signal obtained in the step 2, and detecting the detected object by the terahertz vortex electromagnetic waves sequentially generated by the array of the annular array antenna;
7, receiving echo signals of the detected object by the array of the annular array antenna, carrying out amplitude limiting and amplification by low-noise amplification, and then receiving all the emission mode signals by a receiver;
and 8, performing data inversion and imaging according to the detection requirement to finish the nondestructive detection of the object.
The frequency band selected in the step 1 is in the range of 0.1THz to 10THz, and the corresponding wavelength is in the range of 3mm to 30 um.
In the step 3, the number N expression of the loop array antennas is N-4 · | lm|max。
Radius of circular array in said step 4
Figure BDA0002644631750000031
Where λ is the wavelength of the emitted electromagnetic wave.
The l < th > of the n < th > loop array antenna in the step 5mModally modulated excitation phase wn,mExpressed as:
wn,m＝2π(n-1)lm/N。
l in said step 7mThe modal received signal is
Figure BDA0002644631750000032
Where t is the time variable, t' is the array reference point delay, f0K is 2 pi/lambda, s (t) is a transmitting signal, r is a target distance, theta is a target pitch angle, phi is a target vortex azimuth angle, sigma (r, theta, phi) is a target scattering coefficient, J is a target central frequency, k is 2 pi/lambda, s (t) is a transmitting signal, r is a target distance, theta is a target pitch angle, phi is a target vortex azimuth angle, sigma (r, theta, phi) is a target scattering coefficient, andl(x) Is the first-order Bessel function.
The frequency band specified in the step 2 is 0.1THz to 10 THz.
Compared with the prior art, the invention has the beneficial effects that:
the existing frequency band for detecting an object by utilizing a radar means usually adopts L \ S \ C \ X \ Ku \ Ka and other frequency bands, so that the object is easily damaged.
For a conventional terahertz nondestructive testing technology, the terahertz technology based on vortex electromagnetic waves is adopted, and multi-dimensional spatial sampling can be realized in a short time through traversing mode numbers, so that more information about a target can be obtained, the radar imaging resolution is improved, and the nondestructive testing capability is improved.
Compared with the limitation that the traditional electromagnetic vortex wave cannot generate multiple modes simultaneously, the method has the advantages that the antenna arrays arranged in concentric circles are adopted for amplitude-phase excitation respectively, and the method that each circular array generates one mode can generate multiple modes simultaneously. To reduce the complexity of the radar system, planar microstrip array antennas are employed. The microstrip antenna units are uniformly arranged around the central shaft in the circumferential direction, so that the system can obtain high-mode high resolution and low-mode high antenna radiation gain at the same time.
Drawings
FIG. 1 is a process flow of the method of the present invention.
FIG. 2 is a block diagram of a vortex electromagnetic wave radar system.
Fig. 3 shows phase wavefront distributions under different topological charge numbers of the terahertz frequency band, where (a) - (i) are phase wavefront distributions under different topological charge numbers of 0-11 mode numbers of the terahertz frequency band, respectively.
Fig. 4 shows intensity distributions of radiation fields in the terahertz frequency band under different topological charges, where (a) - (i) are intensity distributions of radiation fields in the terahertz frequency band under different topological charges from 0 to 11 modal numbers, respectively.
Detailed Description
The following is a more detailed description of the practice and effects of the present invention.
The use scene of the invention is as follows: the invention can be applied to nondestructive detection of aerospace composite materials, can break through the traditional real aperture imaging resolution under the condition of small transverse relative motion between the radar and the target by combining terahertz and vortex electromagnetic waves for nondestructive detection, improves the angle resolution of the radar to a certain extent, and solves the problem of low resolution of the existing real aperture radar equipment. As shown in fig. 1, the specific implementation steps are as follows:
step 1, selecting a terahertz frequency band as a frequency band of a nondestructive testing technology. The conventional radar frequency band such as L \ S \ C \ X \ Ku \ Ka and other frequency bands easily cause damage to dielectric materials and semiconductor materials, so that the conventional radar frequency band is not suitable for being used as the frequency band for nondestructive detection of the vortex electromagnetic wave radar. And the terahertz waves (the frequency is in the range of 0.1THz to 10THz, and the corresponding electromagnetic radiation with the wavelength in the range of 3mm to 30 um) are utilized to have better penetrating capability on most dry, non-metal and non-polar materials (such as foam, ceramic, glass, resin, paint, rubber, composites and the like), and the defects in the materials can be detected by combining various imaging technologies.
Step 2, after the terahertz frequency band is selected in step 1, terahertz signals need to be generated, and the main process is as follows: a signal source generates a baseband signal, and a transmitter outputs a radio frequency signal of a terahertz frequency band in a specified frequency band range after the baseband signal is subjected to quadrature modulation, frequency multiplication and filtering amplification; the power amplifier pre-amplifies the power of the radio frequency signal output by the transmitter to obtain an amplified radio frequency signal;
compared with the traditional radar, the vortex electromagnetic wave radar mainly shows that the emitted wave form is not a plane wave or a spherical wave any more, but a vortex wave, so that certain difference is mainly realized in the aspect of generation of antenna electromagnetic waves. The system of the vortex electromagnetic wave radar mainly comprises a signal source, a transmitter, a pre-amplifier, a power amplifier, an array antenna, a power distribution network, a beam control network, a combiner network, a low-noise amplifier, a receiver, a frequency source, a signal processor (including a collector, a data processing unit, a memory and the like), a server, a power distributor, a system controller and the like, as shown in fig. 2.
Step 3, the generation method of the microwave frequency range vortex electromagnetic wave can be summarized into three main categories: the first type of method is a quasi-optical method; the second method is a high-order die attach method; the third method, namely the annular array method, is based on the consideration of engineering realizability, the invention adopts the annular array antenna, the mode number of the vortex electromagnetic wave is related to the number of the antennas in the array, and therefore the emission mode l of the given vortex electromagnetic wave is required1,l2,…,lM(where M is the number of modes) selecting the maximum absolute mode number | lm|maxTaking the numerical value of 4 times and the number as the number N of the loop array antennas;
and 4, after the number of the antennas is determined in the step 3, the circumferential length of the circular array needs to be considered due to the limitation of the size of the antenna unit, so that the radius of the circular array needs to be designed. At the moment, the radius a of the annular array under the half-wavelength arrangement should satisfy
Figure BDA0002644631750000051
Where λ is the wavelength of the emitted electromagnetic wave. After the radius is obtained, the array antenna arrangement can be completed according to the value;
step 5 to realize the respective emission modes l in step 31,l2,…,lMFor loop array antennasEach unit is correspondingly weighted in phase, wherein, the l < th > of the n < th > loop array antennamModally modulated excitation phase wn,m(ii) a Is wn,m＝2π(n-1)lmand/N. And obtaining a complete excitation phase table of each antenna in different modes through traversal calculation.
Step 6, the terahertz vortex wave detection system sequentially generates terahertz vortex electromagnetic waves to detect the detected object by utilizing the terahertz signals generated in the step 2 through the annular array antenna designed in the steps 3 and 4, wherein the annular array controls the mode of transmitting vortex waves through the phase modulation excitation obtained in the step 5;
7, receiving the echo signal of the detected object by the annular array antenna in the same excitation phase as the transmission phase, carrying out amplitude limiting and amplification through low-noise amplification, and then receiving signals of all transmission modes by a receiver, wherein the l < th > signalmThe modal received signal is
Figure BDA0002644631750000061
Where t is the time variable, t' is the array reference point delay, f0K is 2 pi/lambda, s (t) is a transmitting signal, r is a target distance, theta is a target pitch angle, phi is a target vortex azimuth angle, sigma (r, theta, phi) is a target scattering coefficient, J is a target central frequency, k is 2 pi/lambda, s (t) is a transmitting signal, r is a target distance, theta is a target pitch angle, phi is a target vortex azimuth angle, sigma (r, theta, phi) is a target scattering coefficient, andl(x) Is the first-order Bessel function.
And 8, performing corresponding data inversion and imaging according to specific detection requirements such as angle measurement, distance measurement, two-dimensional imaging and the like to finish the nondestructive detection of the object.
The effect of the present invention is further explained by simulation experiments as follows:
the simulation parameters are set as follows:
in order to verify the effectiveness of the proposed algorithm, 11 modal eddy electromagnetic waves are simulated below according to the principle that the array antenna generates eddy electromagnetic waves. In simulation experiments, the radar operating frequency is set to be 200GHz, the array radius is sequentially λ,2 λ,3 λ,4 λ,5 λ,6 λ,7 λ, 8 λ, 9 λ, 10 λ and 11 λ, and the number of array elements is set to be N ═ 8,15,22,29,36,43,50,57,64,71 and 78. To reduce the computation time of the simulation, simulation analysis was performed using MATLAB software.
Fig. 3 shows phase wavefront distributions under different topological charge numbers of the terahertz frequency band. Fig. 4 shows the intensity distribution of the radiation field in the terahertz frequency band under different topological charges. In fig. 3, it can be seen that when l ≠ 0, the array synthesized signal is a plane wave, the wavefront phase thereof is distributed annularly, and when l ≠ 0, the array synthesized vortex electromagnetic wave has a spiral phase wavefront structure, the "branch number" of the phase change takes the absolute value | l | corresponding to the topological charge number, and the number of orbital angular momentum modes that the array can generate satisfies the relationship: -N/2< l < N/2. For a pair of topological charge numbers with positive and negative values, the topological charge numbers respectively correspond to the right-handed vortex electromagnetic waves and the left-handed vortex electromagnetic waves.
And (4) simulation conclusion: simulation results show that the terahertz electromagnetic vortex wave transmitting and receiving technology can be realized.

Claims (1)

1. A nondestructive detection method based on terahertz vortex electromagnetic waves is characterized by comprising the following steps:
step 1, selecting a terahertz frequency band as a frequency band of a nondestructive testing technology;
step 2, generating a baseband signal by a signal source, and outputting a radio frequency signal of a terahertz frequency band in a specified frequency band range after the transmitter performs quadrature modulation, frequency multiplication and filtering amplification on the baseband signal; the power amplifier pre-amplifies the power of the radio frequency signal output by the transmitter to obtain an amplified radio frequency signal;
step 3, determining the emission mode l of vortex electromagnetic waves1,l2,...,lMWherein M is the number of modes; according to the determined emission mode, the maximum mode number | l is calculated according to the absolute valuem|maxDetermining the number N of the loop array antennas as a reference;
step 4, arranging the annular array antennas according to the annular array radius a;
step 5, obtaining the system emission mode l according to the step 31,l2,...,lMRange, corresponding phase weighting of the antenna, calculating the l-th of the n-th loop array antennamModally modulated excitation phase wn,m；
Step 6, exciting by utilizing the phase modulation obtained in the step 5 and the amplified radio frequency signal obtained in the step 2, and detecting the detected object by the terahertz vortex electromagnetic waves sequentially generated by the array of the annular array antenna;
7, receiving echo signals of the detected object by the array of the annular array antenna, carrying out amplitude limiting and amplification by low-noise amplification, and then receiving all the emission mode signals by a receiver;
step 8, performing data inversion and imaging according to the detection requirement to finish nondestructive detection on the object;
the frequency band selected in the step 1 is in the range of 0.1THz to 10THz, and the corresponding wavelength is in the range of 3mm to 30 um;
in the step 3, the number N expression of the loop array antennas is N-4 · | lm|max；
Radius of circular array in said step 4
Figure FDA0003354924570000011
Wherein λ is the wavelength of the emitted electromagnetic wave;
the l < th > of the n < th > loop array antenna in the step 5mModally modulated excitation phase wn,mExpressed as:
wn,m＝2π(n-1)lm/N；
l in said step 7mThe modal received signal is
Figure FDA0003354924570000021
Where t is the time variable, t' is the array reference point delay, f0K is 2 pi/lambda, s (t) is a transmitting signal, r is a target distance, theta is a target pitch angle, phi is a target vortex azimuth angle, sigma (r, theta, phi) is a target scattering coefficient, J is a target central frequency, k is 2 pi/lambda, s (t) is a transmitting signal, r is a target distance, theta is a target pitch angle, phi is a target vortex azimuth angle, sigma (r, theta, phi) is a target scattering coefficient, andl(x) Is a first order Bessel function;
the frequency band specified in the step 2 is 0.1THz to 10 THz.
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106130654A (en) * 2016-06-30 2016-11-16 中国科学院上海微系统与信息技术研究所 A kind of vortex electromagnetic wave generator and method
CN106707270A (en) * 2017-03-06 2017-05-24 中国人民解放军国防科学技术大学 Spinning object detection method based on vortex electromagnetic wave

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110426707B (en) * 2019-08-12 2021-05-07 中国人民解放军国防科技大学 Vortex SAR imaging method and system based on orbital angular momentum
CN110501707B (en) * 2019-08-27 2021-07-02 中国人民解放军国防科技大学 Electromagnetic vortex imaging method based on orbital angular momentum bimodal multiplexing

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106130654A (en) * 2016-06-30 2016-11-16 中国科学院上海微系统与信息技术研究所 A kind of vortex electromagnetic wave generator and method
CN106707270A (en) * 2017-03-06 2017-05-24 中国人民解放军国防科学技术大学 Spinning object detection method based on vortex electromagnetic wave

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
基于轨道角动量的多模态OAM涡旋电磁波;李强;《万方学位论文》;20170228;参见第13、14、25-43页 *
太赫兹特殊光束的研究与应用;李鹤婷 等;《中国激光》;20190630;第46卷(第6期);第1-15页 *

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