Plasma parameter diagnosis method, system and equipment based on transmission signal wave impedance characteristics and medium

Abstract

The invention discloses a plasma parameter diagnosis method, system and equipment based on transmission signal wave impedance characteristics and a medium. The method comprises the steps of calculating a reciprocal of a plasma equivalent relative dielectric constant and separating a real part and an imaginary part by collecting attenuation and phase shift generated by a uniform plasma, determining the position of a transmission signal wave impedance invariant point, and determining the impedance invariant point of the transmission signal wave by combining the real part and the imaginary part of the reciprocal of the equivalent relative dielectric constant and the positive and negative properties of a first derivative thereof. Correctness verification and screening are carried out on transmission signal wave impedance invariant points, the electron density and the collision frequency of the uniform plasma are diagnosed, and the result has high accuracy and reliability. The system, the equipment and the medium are used for realizing the method. On the premise that the diagnosis precision is not lost, the working frequency of the adopted incident electromagnetic waves is greatly smaller than that of a traditional microwave transmission method, the frequency band data can be fully utilized, and the cost of diagnosis equipment is saved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of plasma diagnosis, and particularly relates to a plasma parameter diagnosis method, system, device and medium based on transmission signal wave impedance characteristics. BACKGROUND

[0002] A layer of plasma sheath will be formed on the surface of a hypersonic vehicle during reentry, which will cause communication signal interruption and form a "blackout" phenomenon. Due to the limitations of measuring the plasma sheath, the communication transmission environment is not well understood, which has long plagued the aerospace industry. With the progress of technology, the plasma diagnosis method has made remarkable development, mainly divided into two categories: invasive diagnosis and non-invasive diagnosis. In the invasive diagnosis, the most representative is the Langmuir probe diagnosis method, which can obtain local plasma parameters with high spatial resolution by inserting the test probe into the plasma. However, the invasiveness will cause disturbance to the plasma flow field and also pollute the plasma, and the probe is easily ablated and damaged in high temperature environment (>3000K), which is difficult to work stably for a long time. In contrast, the non-invasive diagnosis does not directly contact with the plasma, but obtains the information of the plasma radiation or the interaction information of electromagnetic wave and plasma to infer the plasma parameters, so it will not cause physical disturbance to the plasma and has the advantage of fast diagnosis, thus has a wider application range.

[0003] In the non-invasive diagnosis, the microwave transmission method (Mo, S. Plasma characteristics based on microwave transmission system[D]. University of Electronic Science and Technology of China, 2016.) transmits electromagnetic wave through a section of plasma, and then analyzes the amplitude attenuation and phase shift generated by the plasma, so as to diagnose the electron density and collision frequency of the plasma at the same time, and thus is widely used in ground plasma devices. However, when using the microwave transmission method to diagnose the plasma parameters, the frequency of the incident electromagnetic wave must be greater than the characteristic frequency of the plasma, otherwise the electromagnetic wave cannot be transmitted through the plasma, so expensive high-frequency equipment is needed. Usually when using the microwave transmission method for diagnosis in the laboratory, in order to reduce the measurement error, the frequency of the electromagnetic wave selected is as large as possible compared with the characteristic frequency of the plasma, usually in Ka or even higher frequency band. When a higher frequency band is used, a waveguide is usually selected as the transmission network, and the erection and measurement of the waveguide transmission network are very complex and expensive. SUMMARY

[0004] To overcome the shortcomings of the prior art, the present invention aims to provide a plasma parameter diagnosis method, system, device, and medium based on the impedance characteristics of transmitted signals. By collecting the attenuation and phase shift generated by a uniform plasma, the reciprocal of the plasma's equivalent relative permittivity is calculated, and its real and imaginary parts are separated. This allows for the determination of the location of points where the transmitted signal impedance remains constant. Combining the real and imaginary parts of the reciprocal of the equivalent relative permittivity and the sign of its first derivative, the correctness of these points is verified and screened, thereby diagnosing the electron density and collision frequency of the uniform plasma. The present invention, without sacrificing diagnostic accuracy, uses an incident electromagnetic wave with a significantly lower operating frequency than the traditional microwave transmission method, saving on diagnostic equipment costs. Furthermore, the traditional microwave transmission method provides invalid diagnostic data when the electromagnetic wave frequency is lower than the plasma's characteristic frequency; the present invention fully utilizes this frequency band data, solving the technical problem of invalid data in this frequency band.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0006] Plasma parameter diagnosis methods based on transmission signal impedance characteristics include:

[0007] S1: Collect the amplitude attenuation Att and phase shift φ generated when the incident electromagnetic wave propagates in the uniform plasma, as diagnostic data;

[0008] S2: The amplitude attenuation Att and phase shift φ, or the transmission coefficient T = Att·e, are obtained through sampling. jφ The inverse solution ranges for the electron density and collision frequency of the uniform plasma are determined; the equivalent relative permittivity ε of the uniform plasma is calculated based on the collected amplitude attenuation Att and phase shift φ. r The reciprocal of , and separate its real part M(ω,ω) p ,ν e ) and the imaginary part N(ω,ω p ,ν e );

[0009] S3: Find all M(ω,ω) within the inverse solution interval. p ,ν e For points where ω = 1, we obtain M(ω,ω) = 1. p ,ν e The set of invariant points where ) = 1

[0010] S4: Preliminary determination of the point where the transmitted signal wave impedance remains unchanged;

[0011] From the set of invariable points Randomly select a point Will Substitute Solve; if If yes, the point is removed from the invariant point set, and the step S4 is repeated; if no, the step S5 is performed. If yes, the step S5 is performed. If no, the step S6 is performed.

[0012] S5: determining the correctness of the wave impedance invariant point of the transmission signal.

[0013] is substituted into and solved; if yes, the point is removed from the invariant point set, and the step S4 is performed; if no, the step S6 is performed. If yes, the step S5 is performed. If no, the step S6 is performed. S6: calculating the uniform plasma electron density and the collision frequency.

[0014] In the step 1, two wideband sweep antennas and a vector network analyzer are used to measure the amplitude attenuation Att and the phase shift φ generated when the incident electromagnetic wave propagates in the uniform plasma; the working frequency range of the wideband sweep antenna needs to meet the characteristic frequency of the uniform plasma in the working frequency range of the antenna, and the working frequency of the vector network analyzer is adjusted to the working frequency range of the wideband sweep antenna.

[0015] In the step 2, the expression of the reciprocal of the equivalent relative dielectric constant ε r of the uniform plasma is as follows:

[0016]

[0017]

[0018] wherein ω is the angular frequency of the incident electromagnetic wave, c is the speed of light, and d is the thickness of the incident electromagnetic wave transmitted through the uniform plasma.

[0019] In the step 6, the expression of the uniform plasma electron density and the collision frequency is as follows:

[0020]

[0021] wherein ε0 is the dielectric constant in vacuum, and m e is the electron mass.

[0022] The application further provides a plasma parameter diagnosis system based on the wave impedance characteristics of the transmission signal, comprising:

[0023] A data acquisition module is used to acquire the amplitude attenuation Att and the phase shift φ generated when the incident electromagnetic wave propagates in the uniform plasma as diagnosis data.

[0024] A first calculation module is used to calculate the transmission coefficient T=Att·e jφ ​​The inverse solution ranges for the electron density and collision frequency of the uniform plasma are determined; the equivalent relative permittivity ε of the uniform plasma is calculated based on the collected amplitude attenuation Att and phase shift φ. r The reciprocal of , and separate its real part M(ω,ω) p ,ν e ) and the imaginary part N(ω,ω p ,ν e );

[0025] Invariant point set determination module: Find all M(ω,ω) within the inverse solution interval. p ,ν e For points where ω = 1, we obtain M(ω,ω) = 1. p ,ν e The set of invariant points where ) = 1

[0026] First judgment module: used to initially determine the point where the transmitted signal wave impedance remains unchanged;

[0027] From the set of invariable points Randomly select a point Will Substitute Solve; if Then remove this point from the set of invariant points. Remove from the middle, and repeat the judgment in the first judgment module; if Then proceed to the second judgment module;

[0028] The second judgment module is used to determine the correctness of the point where the transmitted signal wave impedance remains unchanged.

[0029] Will Substitute Solve; if Then remove this point from the set of invariant points. Remove the middle part and proceed to the first judgment module to continue the judgment; if Then proceed to the second calculation module;

[0030] Second calculation module: based on the determination of the second judgment module. Calculate the electron density and collision frequency of the uniform plasma.

[0031] This invention also provides a plasma parameter diagnostic device based on the impedance characteristics of transmitted signals, comprising:

[0032] Memory: A computer program used to store the plasma parameter diagnosis method based on the impedance characteristics of the transmitted signal described above, and is a computer-readable device.

[0033] Processor: Used to implement the above-described plasma parameter diagnosis method based on the impedance characteristics of transmitted signals when executing the computer program.

[0034] The application further provides a computer readable storage medium storing a computer program, which can realize the above-mentioned plasma parameter diagnosis method based on transmission signal wave impedance characteristics when executed by a processor.

[0035] Compared with the prior art, the application has the following beneficial effects:

[0036] 1. The application uses the propagation vector of the incident electromagnetic wave in the propagation process of the uniform plasma as the intermediate medium, measures the amplitude attenuation and phase shift of the incident electromagnetic wave in the plasma, or the transmission coefficient, and establishes the mapping relationship between the transmission coefficient and the equivalent relative permittivity of the plasma. Since the equivalent relative permittivity is affected by the parameters such as the electron density and the collision frequency in the plasma, the method can effectively convert the plasma parameter measurement problem into an inversion solving problem of the transmission coefficient, and realize the non-contact measurement of the plasma parameters.

[0037] 2. The application obtains the transmission signal wave impedance invariant point by analyzing the amplitude attenuation and phase shift of the incident electromagnetic wave in the propagation process in the plasma. The position of the transmission signal wave impedance invariant point is determined by calculating the frequency response of the real part of the reciprocal of the equivalent relative permittivity of the plasma; at the same time, the transmission signal wave impedance invariant point is verified and screened for correctness in combination with the positive and negative nature of the real part and the imaginary part of the equivalent relative permittivity and the first derivative thereof, so as to obtain the electron density and the collision frequency of the uniform plasma.

[0038] 3. Compared with the prior art microwave transmission method which requires a working frequency much higher than the characteristic frequency of the plasma, the plasma parameter diagnosis method proposed by the application only requires that the working frequency band covers the characteristic frequency of the plasma, and the diagnosis equipment only needs to be equipped with small diagnosis instruments such as a wideband sweep antenna and a vector network analyzer, without the need for high-frequency components, so that accurate diagnosis can be realized. The method not only has simple equipment and is easy to deploy, but also has strong adaptability to the working environment, greatly reduces the cost of the plasma diagnosis system, and has higher practicability and popularization.

[0039] In summary, the plasma parameter diagnosis method proposed by the application calculates the reciprocal of the equivalent relative permittivity of the plasma by collecting the amplitude attenuation and the phase shift, separates the real part and the imaginary part, preliminarily determines the transmission signal wave impedance invariant point, and performs auxiliary verification in combination with the derivative information of the real part and the imaginary part of the equivalent relative permittivity, so as to effectively improve the reliability of the diagnosis result. The multiple verification algorithm design ensures that the diagnosis result has high accuracy and reliability, avoids the errors or uncertainties that may occur in the traditional method, and further improves the ability to accurately measure the characteristics of the plasma. The method can work stably in various complex environments and has strong adaptability and practicability. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 M(ω,ω p ,ν e ) and N(ω,ω p ,ν e ) curves at different collision frequencies, wherein (a) is the M(ω,ω p ,ν e ) curve, and (b) is the N(ω,ω p ,ν e ) curve.

[0041] Figure 2 First derivative curves of M(ω,ω p ,ν e ) and N(ω,ω p ,ν e ) at different collision frequencies, wherein, Figure 2 (a) is the first derivative curve of M(ω,ω p ,ν e ), Figure 2 (b) is the first derivative curve of N(ω,ω p ,ν e ).

[0042] Figure 3 Schematic diagram of a diagnostic device required for the plasma parameter diagnostic method proposed by the present application.

[0043] Figure 4 Flowchart of the plasma parameter diagnostic method proposed by the present application.

[0044] Figure 5 Transmission coefficient curves of a uniform plasma at different collision frequencies.

[0045] Figure 6 Raw transmission coefficients and denoised transmission coefficients collected in experiments.

[0046] Figure 7 M(ω,ω p ,ν e ) and N(ω,ω p ,ν e ) curves obtained in experiments, wherein, Figure 7 (a) is the M(ω,ω p ,ν e ) curve, Figure 7 (b) is the N(ω,ω p ,ν e ) curve. DETAILED DESCRIPTION

[0047] The technical solutions of the present application will be further described below with reference to the accompanying drawings.

[0048] Plasma is generally considered as a special lossy dispersive medium, when the incident electromagnetic wave propagates in the uniform plasma, the propagation vector k of the incident electromagnetic wave and the equivalent relative permittivity ε of the uniform plasma satisfy the following relationship: r There is the following relationship:

[0049]

[0050] Wherein, ω is the angular frequency of the incident electromagnetic wave, c is the speed of light, k0 is the propagation vector of the incident electromagnetic wave in free space, β is the phase shift constant of the incident electromagnetic wave in the plasma, α is the amplitude attenuation constant of the incident electromagnetic wave in the plasma, φ is the phase shift generated after the incident electromagnetic wave transmits through the uniform plasma, Att is the amplitude attenuation generated after the incident electromagnetic wave transmits through the uniform plasma, and d is the thickness of the incident electromagnetic wave transmitting through the uniform plasma.

[0051] From formula (1), the relationship between the amplitude attenuation constant α and the phase shift constant β of the plasma and the equivalent relative permittivity ε of the uniform plasma is as follows: r

[0052]

[0053] The present application uses the broadband frequency sweeping based microwave transmission method to obtain the equivalent relative permittivity ε of the uniform plasma by formula (2), and further can use the relationship between the equivalent relative permittivity ε and the parameters of the uniform plasma to carry out diagnosis. r r

[0054] The relationship between the equivalent relative permittivity ε of the uniform plasma and the electron density n and the collision frequency v of the uniform plasma is as follows: r e e

[0055]

[0056] Wherein, is the characteristic frequency of the uniform plasma, ε0 is the permittivity in vacuum, m e is the electron mass;

[0057] Taking the reciprocal of ε r and separating the real part and the imaginary part, the following is obtained:

[0058]

[0059] Therefore, the real part curve M(ω,ω p ,ν e ) and the imaginary part curve N(ω,ω​​​​​​p ,ν e The expression for ) is as follows:

[0060]

[0061] When ω=ω p At that time, there were:

[0062]

[0063] That is, the real part curve M(ω,ω) of the reciprocal of the equivalent relative permittivity. p ,ν e ) perpetual (ω) p ,1), this point is called the point where the transmitted signal wave impedance remains constant, and at this point its imaginary part curve N(ω,ω) p ,ν e Heng Guo Therefore, the reciprocal of the equivalent relative permittivity can be used to diagnose the electron density and collision frequency of uniform plasma;

[0064]

[0065] Figure 1 The real part curves M(ω,ω) of the reciprocal of the equivalent relative permittivity of uniform plasma at different collision frequencies, obtained from simulations based on the above principles, are given. p ,ν e ) and its imaginary part curve N(ω,ω p ,ν e The electron density is set to 1×10⁻⁶. 11 cm -3 .from Figure 1 As can be seen in (a) above, at different collision frequencies, M(ω,ω) p ,ν e The curve always passes through (ω) p ,1) point; and from Figure 2 As can be seen from its first derivative, the slope is positive at this point, i.e. At this time, N(ω,ω p ,ν e The curve at ω=ω p When the slope is negative, that is

[0066] Based on the above principles and phenomena, this invention proposes a plasma parameter diagnosis method based on the impedance characteristics of transmitted signals, such as... Figure 3 and Figure 4 As shown, it includes the following steps:

[0067] S1: Collect the amplitude attenuation Att and phase shift φ generated when the incident electromagnetic wave propagates in the uniform plasma, as diagnostic data;

[0068] like Figure 3 As shown, a diagnostic device is installed in a vacuum anechoic chamber, including two broadband swept-frequency antennas for transmitting and receiving electromagnetic waves. The operating frequency band of the broadband swept-frequency antennas must satisfy the requirement that the characteristic frequency of the uniform plasma is within the antenna's operating frequency range. The antennas are connected to a vector network analyzer via a low-loss, phase-stable cable through a vacuum flange to ensure the experimental environment is sealed. The operating frequency of the vector network analyzer is tuned to the operating frequency band of the broadband swept-frequency antennas for measurement. The plasma jet is ejected from the plasma nozzle and discharged from the vacuum anechoic chamber through the exhaust system.

[0069] Measurements were performed in the absence of plasma, and the attenuator and phase shifter of the vector network analyzer were adjusted to compensate for errors caused by environmental factors. Then, plasma was introduced and the attenuation Att and phase shift φ generated by the uniform plasma were measured using the vector network analyzer.

[0070] S2: The amplitude attenuation Att and phase shift φ, or the transmission coefficient T = Att·e, are obtained through sampling. jφ The rising start segment of attenuation is determined from the plotted transmission coefficient curve, and this rising start segment is defined as the inverse solution range of electron density and collision frequency of the uniform plasma; the collected amplitude attenuation Att and phase shift φ are substituted into formula (11) to calculate the equivalent relative permittivity ε of the uniform plasma. r reciprocal And separate the real part M(ω,ω) p ,ν e ) and the imaginary part N(ω,ω p ,ν e );

[0071]

[0072] Figure 5 The attenuation and phase shift of incident electromagnetic waves caused by uniform plasma with the same electron density but different collision frequencies, from Figure 5 As can be seen, there is a clear initial rise in attenuation near the characteristic frequency of the uniform plasma. This initial rise can be used to determine the inversion interval during subsequent diagnostics.

[0073] S3: Find all M(ω,ω) within the inverse solution interval. p ,ν e For points where ω = 1, we obtain M(ω,ω) = 1. p ,ν e The set of invariant points where ) = 1

[0074] S4: Preliminary determination of the point where the transmitted signal wave impedance remains unchanged;

[0075] From the set of invariable points Randomly select a point Will Substitute Solve; if Then remove this point from the set of invariant points. Remove from the middle, repeat S4; if Then switch to S5;

[0076] S5: Determine the correctness of the point where the transmitted signal wave impedance remains constant;

[0077] Will Substitute Solve; if Then remove this point from the set of invariant points. Remove the middle part and switch to S4; if Then proceed to S6;

[0078] S6: Calculate the electron density and collision frequency of a uniform plasma;

[0079]

[0080] This invention also provides a plasma parameter diagnostic system based on the impedance characteristics of transmitted signals, comprising:

[0081] Data acquisition module: used to acquire the amplitude attenuation Att and phase shift φ generated when the incident electromagnetic wave propagates in a uniform plasma, as diagnostic data;

[0082] First calculation module: Calculates the amplitude attenuation Att and phase shift φ, or the transmission coefficient T = Att·e, based on the acquired amplitude attenuation Att and phase shift φ. jφ The inverse solution ranges for the electron density and collision frequency of the uniform plasma are determined; the equivalent relative permittivity ε of the uniform plasma is calculated based on the collected amplitude attenuation Att and phase shift φ. r The reciprocal of , and separate its real part M(ω,ω) p ,ν e ) and the imaginary part N(ω,ω p ,ν e );

[0083] Invariant point set determination module: Find all M(ω,ω) within the inverse solution interval. p ,ν e For points where ω = 1, we obtain M(ω,ω) = 1. p ,ν e The set of invariant points where ) = 1

[0084] First judgment module: used to initially determine the point where the transmitted signal wave impedance remains unchanged;

[0085] From the set of invariable points Randomly select a point Bring in Solve; if The point is removed from the invariant point set In the first judgment module, if The second judgment module is used to determine the correctness of the transmission signal wave impedance invariant point.

[0086] The second judgment module is used to determine the correctness of the transmission signal wave impedance invariant point.

[0087] Bring in Solve; if The point is removed from the invariant point set In the first judgment module, if The second calculation module is used to calculate the uniform plasma electron density and collision frequency according to the determination of the second judgment module. The second calculation module is used to calculate the uniform plasma electron density and collision frequency according to the determination of the second judgment module.

[0088] The application also provides a plasma parameter diagnosis device based on transmission signal wave impedance characteristics, comprising:

[0089] The memory is used for storing the computer program of the above-mentioned plasma parameter diagnosis method based on transmission signal wave impedance characteristics, and is a computer-readable device.

[0090] The processor is used for executing the computer program to realize the above-mentioned plasma parameter diagnosis method based on transmission signal wave impedance characteristics.

[0091] The application also provides a computer-readable storage medium, which stores a computer program, and the computer program can realize the above-mentioned plasma parameter diagnosis method based on transmission signal wave impedance characteristics when executed by a processor.

[0092] In order to verify the accuracy of the plasma parameter diagnosis method provided by the application, a device is built as shown in

[0093] In order to verify the accuracy of the plasma parameter diagnosis method provided by the application, a device is built as shown in Figure 3 ​​The experimental device is shown, the plasma jet adopts a circular Φ220 nozzle, the wideband swept-frequency antenna adopts an ultra-wideband VVD antenna, which can measure a range of 2-9 GHz; the excitation power is set to 5 kV. The wideband swept-frequency antenna is carried on a movable guide rail, the center of the antenna is 190 mm away from the center of the plasma jet, and the center of the antenna is 220 mm away from the plasma nozzle. In order to prevent the plasma jet from damaging the antenna, the antenna is equipped with a water-cooled support, and a layer of heat-insulating and wave-transparent material is added to the surface. The antenna transmission data is measured and collected by a vector network analyzer of Anristu MS4647B type; the vector network analyzer is placed outside the vacuum darkroom, and is connected with the internal antenna through a flange.

[0094] After completing the installation and debugging of the experimental equipment, first measure the data without plasma, the obtained data is used for subsequent calibration work to ensure the accuracy and reliability of the experimental data. Then, close the vacuum darkroom door and start the exhaust system to ensure that the laboratory is in a vacuum environment. In order to maintain the stability of the plasma jet and the constancy of the chemical composition, argon gas is injected into the darkroom during the experiment, and the gas inlet amount is 15 g / s. After completing the above preparation work, the excitation power is turned on to excite the alternating electric field, thereby "igniting" and causing the generation of the plasma jet. After the plasma jet is stable, the Langmuir probe is used to collect data of the plasma, and the corresponding experimental data is saved. At the same time, the transmission data is collected by the antenna and transmitted to the external computer for subsequent data processing and analysis.

[0095] During the experiment, multiple groups of data are collected, and finally the experimental data when the plasma is stable are selected to ensure the representativeness and reliability of the selected data. In order to avoid damage to the equipment caused by long-time operation of the plasma jet system, the duration of the plasma is strictly controlled during the experiment. The excitation power starts from 0 and increases, and when the excitation voltage stabilizes at 5 kV and the plasma jet is stable, the data collection at 5 kV is completed. After the data collection is completed, the power voltage will gradually decrease, and the power will be turned off. The power voltage will gradually decrease, and the exhaust device will be started to discharge the gas in the vacuum darkroom. After the initial conditions of the laboratory are restored, the experiment is ended.

[0096] Figure 6 The original transmission coefficients collected in the experiment and the transmission coefficients after denoising and fitting processing can be judged from Figure 6 that the rising initial segment is 2.2 GHz-3.1 GHz. Using the rising initial segment for diagnosis, the M curve and the N curve are obtained as Figure 7 (a) and Figure 7As shown in (b), the point where the wave impedance remains constant is (2.44, 1), corresponding to the point on the N curve (2.44, 8.71). The algorithm confirms that this constant point is correct, and the plasma electron density calculated from this point is 7.4 × 10⁻⁶. 10 cm -3 The collision frequency was 0.28 GHz. The electron density value obtained from the diagnosis was 7.4 × 10⁻⁶, the same as that obtained under the same conditions as the Langmuir probe. 10 cm -3 The relative error is 0, and the electron density value obtained under the same conditions as the microwave reflection method is 7.7 × 10⁻⁶. 10 cm -3 The relative error is 3.9%, indicating that the diagnostic results obtained by the plasma parameter diagnostic method proposed in this invention are highly accurate.

Claims

1. A method of diagnosing plasma parameters based on wave impedance characteristics of a transmitted signal, characterized by, The method comprises the following steps: S1: collecting amplitude attenuation Att and phase shift φ generated when incident electromagnetic wave propagates in uniform plasma as diagnostic data; S2: determining the inverse solution interval of the electron density and the collision frequency of the uniform plasma by the collected amplitude attenuation Att and phase shift φ or transmission coefficient T = Att e jφ ; calculating the inverse of the equivalent relative dielectric constant ε r of the uniform plasma from the collected amplitude attenuation Att and phase shift φ, and separating the real part M(ω, ω p , v e ) and the imaginary part N(ω, ω p , v e ) thereof; S3: find all M(ω,ω p ,ν e ) = 1 points in the inverse solution interval, get the invariant point set satisfying M(ω,ω p ,ν e ) = 1 S4: preliminarily judging wave impedance invariant point of the transmitted signal; a point is randomly selected from the fixed point set a point is randomly selected from the fixed point set bring in bring in solving; if the point is removed from the fixed point set S4; if go to S5; S5: determining the correctness of the wave impedance invariant point of the transmitted signal; Bring in Take in Solve; if then remove this point from the set of invariants , go to S4; if , go to S6; S6: calculating the electron density and collision frequency of the uniform plasma.

2. The method of diagnosing a plasma parameter based on a wave impedance feature of a transmission signal according to claim 1, wherein: In step 1, two wideband swept-frequency antennas and a vector network analyzer are used to measure the amplitude attenuation Att and phase shift φ generated when incident electromagnetic wave propagates in uniform plasma; the working frequency range of the wideband swept-frequency antenna needs to meet the characteristic frequency of the uniform plasma in the working frequency range of the antenna, and the working frequency of the vector network analyzer is adjusted to the working frequency range of the wideband swept-frequency antenna.

3. The method of diagnosing a plasma parameter based on a wave impedance feature of a transmitted signal according to claim 1, wherein: In step 2, the expression of the inverse of the equivalent relative permittivity ε r of the uniform plasma is as follows: Wherein, ω is the angular frequency of the incident electromagnetic wave, c is the speed of light, and d is the thickness of the incident electromagnetic wave transmitted through the uniform plasma.

4. The method of diagnosing a plasma parameter based on a wave impedance feature of a transmission signal according to claim 1, wherein: In step 6, the expression of the electron density and collision frequency of the uniform plasma is as follows: where ε0is the vacuum permittivity, m e is the electron mass.

5. A plasma parameter diagnostic system based on wave impedance characteristics of a transmitted signal, characterized by, The method comprises the following steps: The data acquisition module is used to collect amplitude attenuation Att and phase shift φ generated when incident electromagnetic wave propagates in uniform plasma as diagnostic data; The first calculation module: through the collected amplitude attenuation Att and phase shift φ or transmission coefficient T=Att·e jφ , determine the inverse solution interval of the electron density and collision frequency of the uniform plasma; calculate the inverse of the equivalent relative dielectric constant ε r of the uniform plasma according to the collected amplitude attenuation Att and phase shift φ, and separate the real part M(ω,ω p ,ν e ) and the imaginary part N(ω,ω p ,ν e ) of the equivalent relative dielectric constant ε Invariant point set determination module: find all points of M(ω,ω p ,ν e ) = 1 in the inverse solution interval, get the invariant point set satisfying M(ω,ω p ,ν e ) = 1 The first judging module is used to preliminarily judge the wave impedance invariant point of the transmitted signal; randomly select a point from the fixed point set bring into solve; if then remove this point from the fixed point set and repeat the judgment in the first judgment module; if then go to the second judgment module​​ The second judging module is used to determine the correctness of the wave impedance invariant point of the transmitted signal; Bring in Take in Solve; if This point is removed from the invariant point set Go to the first judgment module to continue to judge; if Go to the second calculation module; The second calculation module is configured to calculate the uniform plasma electron density and the collision frequency according to the determination of the second judgment module. The uniform plasma electron density and the collision frequency are calculated.

6. A plasma parameter diagnostic device based on wave impedance characteristics of a transmission signal, characterized by The memory is used to store the computer program of the plasma parameter diagnostic method based on the wave impedance characteristics of the transmitted signal according to any one of claims 1-4, which is a computer-readable device; The processor is used to execute the computer program to realize the plasma parameter diagnostic method based on the wave impedance characteristics of the transmitted signal according to any one of claims 1-4. The computer program is stored in the computer-readable storage medium, and the computer program can realize the plasma parameter diagnostic method based on the wave impedance characteristics of the transmitted signal according to any one of claims 1-4 when executed by the processor.

7. A computer-readable storage medium, characterized in that: ​

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