Electromagnetic property testing method for large-scale vacuum darkroom plasma environment

Abstract

The invention discloses an electromagnetic characteristic test method for a large-scale vacuum darkroom plasma environment, and belongs to the technical field of microwave test, and the method comprises the steps: arranging an antenna motion device, an antenna protection cover and a transmitting antenna in a large-scale darkroom, vacuumizing the large-scale darkroom, and carrying out the electromagnetic characteristic test through a plasma source air inlet in the large-scale darkroom, a stable plasma environment is provided; the transmitting antenna and the receiving antenna are connected with the vector network analyzer, the vector network analyzer is connected with the computer, the computer is used for controlling the vector network analyzer to obtain antenna data under the plasma environment of the large vacuum darkroom, and a gain directional diagram and transmissivity are obtained through calculation. According to the invention, a stable large darkroom plasma environment can be provided, the repeatability of an electromagnetic characteristic test is ensured, the motion state of the receiving antenna at each angle can be ensured to be obtained through the antenna motion device, and stable plasma antenna data can be rapidly and massively acquired.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave testing, and in particular relates to an electromagnetic characteristic testing method for a large vacuum darkroom plasma environment. Background Art

[0002] In rapidly evolving plasmas, electromagnetic wave propagation and plasma interaction are important research areas, especially the "blackout" phenomenon when a spacecraft reenters the atmosphere. The plasma sheath formed on the surface of the spacecraft will shield the signal, resulting in interruptions in navigation and telemetry. Therefore, solving the problem of information transmission under the plasma sheath has become a hot issue in aerospace.

[0003] Nowadays, there are three main environments for conducting experiments on the transmission and radiation of electromagnetic waves in plasma: the first is a shock tube based on the principle of high-speed aerodynamics, but the transmission and radiation test of electromagnetic waves in plasma has great requirements on the stability, continuity and dynamic range of the plasma, and the plasma generated by the shock tube has a limited duration, and the arc wind tunnel cannot quickly generate dynamic plasma. At the same time, the electron temperature is too high, which is not conducive to the experiment; the second is the arc wind tunnel, which forms a plasma beam by heating the gas to the ionization temperature, but the existing experimental equipment is small in scale and does not have far-field testing conditions for low frequencies. The third is glow discharge plasma generated in a low-pressure non-equilibrium environment, but the electron density range of the glow discharge plasma is too small.

[0004] In recent years, a series of studies on antennas, propagation, and suppression technologies under plasma sheaths have been carried out using new cold plasma sources, focusing on miniaturization, controllability, and suitability for general laboratory environments. However, the equipment that generates plasma or the instruments that move antennas are usually large and difficult to operate, and repeatability experiments are difficult, which brings significant difficulties to the testing of radiation patterns. In addition, the existing conventional testing methods often cannot take into account the testing conditions of a good darkroom, and can only add absorbing materials in some areas, resulting in inaccurate test results.

[0005] Therefore, there is an urgent need for a testing method that has high precision, good repeatability, and sufficient mobility to adapt to diverse testing environments. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, the electromagnetic characteristics testing method for a large vacuum darkroom plasma environment provided by the present invention solves the problem that the plasma environment is difficult to maintain and the electromagnetic characteristics testing conditions do not meet the requirements.

[0007] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is: a method for testing electromagnetic characteristics of a large vacuum darkroom plasma environment, comprising the following steps:

[0008] S1: Set up an antenna moving device and an antenna protective cover in a large darkroom, install a receiving antenna on the antenna moving device, and install a transmitting antenna in the antenna protective cover;

[0009] S2: Connect the transmitting antenna and the receiving antenna to the vector network analyzer, and connect the vector network analyzer to the computer;

[0010] S3: evacuating the large dark chamber to a vacuum, and providing a stable plasma environment through a plasma source gas inlet in the large dark chamber to obtain a large vacuum dark chamber plasma environment;

[0011] S4: Use a computer to control a vector network analyzer to obtain antenna data in a large vacuum darkroom plasma environment;

[0012] S5: Based on the antenna data, the relative method is used to calculate the gain and transmittance of the electromagnetic wave, and the electromagnetic characteristics test of the large vacuum darkroom plasma environment is completed.

[0013] The beneficial effects of the present invention are as follows: the present invention can provide a stable large-scale darkroom plasma environment, ensure the repeatability of electromagnetic characteristic testing, and can adjust the parameters of the plasma to achieve electromagnetic testing of different electron density levels; at the same time, the present invention proposes two wiring methods to obtain high-quality S parameter data in view of the problem of large environmental size; the present invention also directly connects a computer to a vector network analyzer to quickly collect a large amount of data, and obtains data with high accuracy through data processing; in addition, the present invention also collects three state scanning angle S21 parameters, and can ensure that the motion state of the receiving antenna at each angle can be accurately obtained through the antenna motion device, and adopts the relative method to obtain the radiation pattern of the antenna and the transmittance of the electromagnetic wave in the plasma.

[0014] Further: the transmitting antenna and the receiving antenna are facing each other;

[0015] The receiving antenna and the transmitting antenna are both ultra-wideband transceiver antennas;

[0016] The antenna movement device is used to control the receiving antenna to be in different angles;

[0017] The antenna protection cover is used to protect the transmitting antenna.

[0018] The beneficial effect of the above further scheme is that through the receiving antenna, the transmitting antenna, the antenna motion device and the antenna protection cover, electromagnetic testing can be satisfied under three conditions: no plasma and no cover, no plasma and with cover, and with plasma and with cover.

[0019] Further: the transmitting antenna and the receiving antenna are both connected to the vector network analyzer, and the specific connection method includes:

[0020] The transmitting antenna is connected to the second port of the vector network analyzer through the lower end through-bin flange;

[0021] The transmitting antenna is connected to the first port of the vector network analyzer through the lower end through-bin flange, and the receiving antenna is connected to the second port of the vector network analyzer through the upper end through-bin flange.

[0022] The beneficial effect of the above further scheme is: connecting the antenna to the vector network analyzer through the lower end through-bin flange and the upper end through-bin flange can reduce the influence of the long cable on the test results of the vector network analyzer and ensure the accuracy of the data.

[0023] Furthermore, the step of connecting the vector network analyzer to the computer includes:

[0024] Query the IP address of the vector network analyzer and connect the vector network analyzer to the computer using an Ethernet cable;

[0025] Check the Ethernet on the computer and change the IP address through Ethernet to connect the vector network analyzer to the computer network;

[0026] Open the control software on the computer and connect the computer to the vector network analyzer through the control software.

[0027] The beneficial effect of the above further scheme is: by controlling the vector network analyzer through a computer, the vector network analyzer can be remotely controlled to collect antenna data and perform automatic collection, thereby improving the efficiency of antenna data collection, shortening the test time, and reducing human errors.

[0028] Further: the specific steps of S3 are as follows:

[0029] S301: closing the large darkroom, and pumping the air pressure in the large darkroom to the load limit vacuum, thereby obtaining a large vacuum darkroom;

[0030] S302: Stable plasma is ejected through the plasma source air inlet in the large dark chamber until the large vacuum dark chamber reaches a set air pressure to obtain a stable plasma environment;

[0031] S303: In a stable plasma environment, the cooling water, control cabinet and DC excitation source of the plasma source system are turned on in sequence to obtain a large vacuum darkroom plasma environment.

[0032] The beneficial effect of the above further scheme is that stable plasma is ejected through the plasma source air inlet, which can provide a stable plasma environment for a large vacuum darkroom and ensure the stability of the test data.

[0033] Further: A stable plasma environment is obtained as follows:

[0034] A1: eject plasma with a fixed electron density value through the plasma source inlet, and test the curve of the electron density of the plasma changing with time;

[0035] A2: On the curve of the plasma electron density changing with time, select the smooth curve and mark it to obtain the stable time period of the plasma electron density;

[0036] A3: Repeat A1 to A2 several times to obtain several plasma electron density stable time periods, and select overlapping electron density stable time periods;

[0037] A4: A stable plasma environment is obtained based on the overlapping electron density stabilization time periods.

[0038] The beneficial effect of the above further scheme is: by monitoring the plasma ejected from the plasma source air inlet, the stable time period of the ejected plasma can be obtained, and it is ensured that the plasma ejected from the plasma source air inlet each time has a fixed electron density value, ensuring that a stable plasma environment can be obtained during the test.

[0039] Further: the expressions of gain and transmittance are as follows:

[0040]

[0041]

[0042] Among them, G1 is the antenna gain with a cover but no plasma, G2 is the antenna gain with a cover and plasma, T is the transmittance of electromagnetic waves in plasma, is the scanning angle S21 parameter of the receiving antenna, is the scanning angle S21 parameter of the receiving antenna with antenna protection cover, is the scanning angle S21 parameter of the receiving antenna with antenna protection cover and plasma, and G′ is the calibration gain of the pure antenna.

[0043] The beneficial effect of the above further scheme is that by calculating the gain and transmittance, the electromagnetic characteristics of the antenna can be analyzed, and the radiation pattern of the antenna and the transmittance of the electromagnetic wave in the plasma can be further obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a flow chart of an electromagnetic characteristics testing method for a large vacuum darkroom plasma environment;

[0045] Figure 2 It is a schematic diagram of the plasma environment of a large vacuum dark chamber of the present invention. DETAILED DESCRIPTION

[0046] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0047] In the present invention, the following terms are used for description:

[0048] S11 parameter: In the RF field, S11 refers to the reflection coefficient, which is used to describe the reflection ability of a device or system port to the incident signal. It is generally used to measure the input impedance matching of antennas, RF devices or circuits. When the S11 value is close to 0, it means there is almost no reflection and the matching is good.

[0049] S21 parameter: S21 is the transmission coefficient, which describes the signal radiation efficiency from port 1 to port 2. In the measurement of filters or amplifiers, S21 represents the signal gain or loss from the input to the output.

[0050] Radiation pattern: Radiation pattern, also known as radiation mode or antenna radiation pattern, is a spatial distribution diagram of the antenna's radiation capability, usually showing the relative gain or radiation intensity of the antenna in different directions.

[0051] Plasma: Plasma is a collection of charged particles composed of free electrons, ions and neutral particles, often referred to as the fourth state of matter. Its behavior is governed by electromagnetic fields and has many special physical properties.

[0052] like Figure 1 As shown, a method for testing electromagnetic characteristics of a large vacuum darkroom plasma environment includes the following steps:

[0053] S1: Set up an antenna moving device and an antenna protective cover in a large darkroom, install a receiving antenna on the antenna moving device, and install a transmitting antenna in the antenna protective cover;

[0054] S2: Connect the transmitting antenna and the receiving antenna to the vector network analyzer, and connect the vector network analyzer to the computer;

[0055] S3: evacuating the large dark chamber to a vacuum, and providing a stable plasma environment through a plasma source gas inlet in the large dark chamber to obtain a large vacuum dark chamber plasma environment;

[0056] S4: Use a computer to control a vector network analyzer to obtain antenna data in a large vacuum darkroom plasma environment;

[0057] S5: Based on the antenna data, the relative method is used to calculate the gain and transmittance of the electromagnetic wave, and the electromagnetic characteristics test of the large vacuum darkroom plasma environment is completed.

[0058] In one embodiment of the present invention, the antenna protection cover has good wave permeability and heat insulation, and can cope with the extreme high temperature during the test. The transmitting antenna is installed in the antenna protection cover through a suitable antenna clamping device, which can protect the transmitting antenna. The antenna protection cover is installed in a large vacuum darkroom through a protective cover fixing device; an antenna movement device and an antenna protection cover are set in the large darkroom, and a receiving antenna is installed on the antenna movement device to keep the transmitting antenna and the receiving antenna facing each other, wherein the receiving antenna and the transmitting antenna are both ultra-wideband transceiver antennas, and by controlling the antenna movement device, the receiving antenna can be controlled to be in different angles and receive antenna signals at different incident angles. At the same time, the antenna protection cover can be disassembled and added according to different electromagnetic test conditions, and electromagnetic tests with and without covers can be performed.

[0059] In S2, both the transmitting antenna and the receiving antenna are connected to the vector network analyzer. Considering the large volume of the large vacuum darkroom and the long line cables required, the specific connection method of the present invention includes:

[0060] The transmitting antenna is connected to the second port of the vector network analyzer through the lower end flange, which can measure the S11 parameters of the antenna, reduce the influence of the long cable on the measurement results of the vector network analyzer, and calibrate the vector network analyzer after connection;

[0061] The transmitting antenna is connected to the first port of the vector network analyzer through the lower through-bay flange, and the receiving antenna is connected to the second port of the vector network analyzer through the upper through-bay flange. The S21 parameters of the antenna can be measured, reducing the impact of long cables on the measurement results of the vector network analyzer, and the vector network analyzer can be calibrated after connection.

[0062] In S2, the vector network analyzer is connected to the computer. The present invention directly connects the vector network analyzer to the computer, which can improve the acquisition speed, reduce the number of plasma discharges, and quickly acquire 5 frames of data through the computer and save them. The specific connection steps of the present invention include:

[0063] Query the IP address of the vector network analyzer and connect the vector network analyzer to the computer using an Ethernet cable;

[0064] Query the Ethernet on the computer and change the IP address in Internet Protocol Version 4 over Ethernet to connect the vector network analyzer to the computer through the network;

[0065] Open the control software corresponding to the vector network analyzer on the computer, and control the connection between the computer and the vector network analyzer through the control software; at this time, the vector network analyzer can be controlled by inputting the set data format and type on the computer; automatic collection can be performed to improve the antenna data collection efficiency, shorten the test time, and reduce human errors.

[0066] In S3, the large dark chamber is evacuated to a vacuum, and a stable plasma environment is provided through a plasma source air inlet in the large dark chamber to obtain a large vacuum dark chamber plasma environment;

[0067] Before officially starting the electromagnetic test, it is necessary to ensure that the plasma source inlet sprays a stable plasma environment, which can be obtained as follows:

[0068] A1: eject plasma with a fixed electron density value through the plasma source inlet, and test the curve of the electron density of the plasma changing with time;

[0069] A2: On the curve of the plasma electron density changing with time, select the smooth curve and mark it to obtain the stable time period of the plasma electron density;

[0070] A3: Repeat A1 to A2 several times to obtain several plasma electron density stable time periods, and select overlapping electron density stable time periods; in the process of repeating A1 to A2 several times, it is necessary to keep the electron density value of the plasma ejected each time fixed, but in the actual process, the electron density value will change due to various factors. Therefore, the electron density value variation range can be set, within which the plasma can remain stable, ensuring the repeatability of the electromagnetic property test;

[0071] A4: A stable plasma environment is obtained based on the overlapping electron density stable time periods. When testing the electromagnetic properties of plasma, the overlapping electron density stable time periods are selected for data collection, so that data in a stable plasma environment can be obtained.

[0072] The specific steps of S3 are as follows:

[0073] S301: closing the large darkroom, and pumping the air pressure in the large darkroom to the load limit vacuum, thereby obtaining a large vacuum darkroom;

[0074] S302: Stable plasma is ejected through the plasma source air inlet in the large dark chamber until the large vacuum dark chamber reaches a set air pressure to obtain a stable plasma environment;

[0075] S303: In a stable plasma environment, the cooling water, control cabinet and DC excitation source of the plasma source system are turned on in sequence to obtain a large vacuum darkroom plasma environment.

[0076] In S4, a computer was used to control a vector network analyzer to obtain antenna data in a large vacuum darkroom plasma environment;

[0077] In one embodiment of the present invention, the antenna protection cover can be disassembled and installed, and the plasma source air inlet can be opened and closed, so as to perform electromagnetic tests under three conditions: no plasma and no cover, no plasma and with a cover, and with plasma and with a cover. Before performing a formal electromagnetic characteristic test, the probe is controlled by an antenna motion device to obtain the electron density profile of the experimental area, and then the probe is moved away to avoid affecting the electromagnetic test. The electron density data collected by the vector network analyzer can be numerically modeled to find the source of error and reduce the uncertainty of the test results. During the radiation characteristic test, the transmitting antenna is fixed and the antenna is used to control the electron density profile of the experimental area. The motion device moves and turns the receiving antenna, and at the same time calculates the coordinates and attitude angles corresponding to each angle of the receiving antenna in advance, and directly inputs them into the control system of the antenna motion device, so as to quickly and accurately obtain the S21 parameters within the set angle range within a limited time, such as the S21 parameters within the range of -13° to 13°; repeat the test, and quickly collect 5 frames of data through a computer-controlled vector network analyzer to obtain multiple groups of antenna data, eliminate data with large differences, and take the average of the remaining data as the final S11 parameters and S21 parameters, so as to further improve the data quality and reduce the influence of the temporal instability of the plasma on the test results.

[0078] In one embodiment of the present invention, Figure 2 As shown, it is a schematic diagram of the plasma environment of a large vacuum darkroom of the present invention, wherein the diagnostic area is a plasma environment, the antenna moving device is a slide rail moving device, and other antenna moving devices can also be selected. The receiving angle of the receiving antenna can be changed by moving, so that the receiving antenna can receive antenna signals with different incident angles and obtain antenna data.

[0079] The antenna data includes: the S11 parameter of the transmitting antenna, the S21 parameter of the scanning angle of the receiving antenna. At the same time, the antenna protection cover can be disassembled and installed, the plasma source inlet can be opened and closed, and the antenna moving device can be controlled to move the angle and state of the receiving antenna, so as to obtain the S21 parameter of the scanning angle of the receiving antenna, the S21 parameter of the receiving antenna with the antenna protection cover, and the S21 parameter of the receiving antenna with the antenna protection cover and plasma. The gain and transmittance of the antenna are calculated according to the antenna data. The expressions of the gain and transmittance are as follows:

[0080]

[0081] Among them, G1 is the antenna gain with a cover but no plasma, G2 is the antenna gain with a cover and plasma, T is the transmittance of electromagnetic waves in plasma, is the scanning angle S21 parameter of the receiving antenna, is the scanning angle S21 parameter of the receiving antenna with antenna protection cover, is the scanning angle S21 parameter of the receiving antenna with antenna protection cover and plasma, G′ is the calibration gain of the pure antenna, wherein the calibration gain of the pure antenna is the gain without plasma and cover, which can be directly measured in advance without additional calculation and measurement; the gain and transmittance of the antenna are obtained according to the calculation, and the radiation pattern of the antenna and the transmittance of the electromagnetic wave in the plasma are further obtained to complete the electromagnetic characteristics test of the large vacuum darkroom plasma environment.

[0082] The beneficial effects of the present invention are as follows: the present invention can provide a stable large-scale darkroom plasma environment, ensure the repeatability of electromagnetic characteristic testing, and can adjust the parameters of the plasma to achieve electromagnetic testing of different electron density levels; at the same time, the present invention proposes two wiring methods to obtain high-quality S parameter data in view of the problem of large environmental size; the present invention also directly connects a computer to a vector network analyzer to quickly collect a large amount of data, and obtains data with high accuracy through data processing; in addition, the present invention also collects three state scanning angle S21 parameters, and can ensure that the motion state of the receiving antenna at each angle can be accurately obtained through the antenna motion device, and adopts the relative method to obtain the radiation pattern of the antenna and the transmittance of the electromagnetic wave in the plasma.

Claims

1. A method for testing electromagnetic properties of a large vacuum darkroom plasma environment, characterized in that: The following steps are involved: S1: Set up an antenna moving device and an antenna protective cover in a large darkroom, install a receiving antenna on the antenna moving device, and install a transmitting antenna in the antenna protective cover; S2: Connect the transmitting antenna and the receiving antenna to the vector network analyzer, and connect the vector network analyzer to the computer; S3: evacuating the large dark chamber to a vacuum, and providing a stable plasma environment through a plasma source gas inlet in the large dark chamber to obtain a large vacuum dark chamber plasma environment; S4: Use a computer to control a vector network analyzer to obtain antenna data in a large vacuum darkroom plasma environment; S5: Based on the antenna data, the relative method is used to calculate the gain and transmittance of the electromagnetic wave, and the electromagnetic characteristics test of the large vacuum darkroom plasma environment is completed.

2. The electromagnetic characteristics testing method for a large vacuum darkroom plasma environment according to claim 1, characterized in that: The transmitting antenna and the receiving antenna are facing each other; The receiving antenna and the transmitting antenna are both ultra-wideband transceiver antennas; The antenna movement device is used to control the receiving antenna to be in different angles; The antenna protection cover is used to protect the transmitting antenna.

3. The electromagnetic characteristics testing method for a large vacuum darkroom plasma environment according to claim 2, characterized in that: The transmitting antenna and the receiving antenna are both connected to the vector network analyzer, and the specific connection method includes: The transmitting antenna is connected to the second port of the vector network analyzer through the lower end through-bin flange; The transmitting antenna is connected to the first port of the vector network analyzer through the lower end through-bin flange, and the receiving antenna is connected to the second port of the vector network analyzer through the upper end through-bin flange.

4. The electromagnetic characteristics testing method for a large vacuum darkroom plasma environment according to claim 1, characterized in that: The specific connection steps of connecting the vector network analyzer to the computer include: Query the IP address of the vector network analyzer and connect the vector network analyzer to the computer using an Ethernet cable; Check the Ethernet on the computer and change the IP address through Ethernet to connect the vector network analyzer to the computer network; Open the control software on the computer and connect the computer to the vector network analyzer through the control software.

5. The electromagnetic characteristics testing method for a large vacuum darkroom plasma environment according to claim 1, characterized in that: The specific steps of S3 are as follows: S301: closing the large darkroom, and pumping the air pressure in the large darkroom to the load limit vacuum, thereby obtaining a large vacuum darkroom; S302: Stable plasma is ejected through the plasma source air inlet in the large dark chamber until the large vacuum dark chamber reaches a set air pressure to obtain a stable plasma environment; S303: In a stable plasma environment, the cooling water, control cabinet and DC excitation source of the plasma source system are turned on in sequence to obtain a large vacuum darkroom plasma environment.

6. The electromagnetic characteristics testing method for a large vacuum darkroom plasma environment according to claim 5, characterized in that: The stable plasma environment is obtained as follows: A1: eject plasma with a fixed electron density value through the plasma source inlet, and test the curve of the electron density of the plasma changing with time; A2: On the curve of the plasma electron density changing with time, select the smooth curve and mark it to obtain the stable time period of the plasma electron density; A3: Repeat A1 to A2 several times to obtain several plasma electron density stable time periods, and select overlapping electron density stable time periods; A4: A stable plasma environment is obtained based on the overlapping electron density stabilization time periods.

7. The electromagnetic characteristics testing method for a large vacuum darkroom plasma environment according to claim 1, characterized in that: The expressions of gain and transmittance are as follows: Among them, G1 is the antenna gain with a cover but no plasma, G2 is the antenna gain with a cover and plasma, T is the transmittance of electromagnetic waves in plasma, is the scanning angle S21 parameter of the receiving antenna, is the scanning angle S21 parameter of the receiving antenna with antenna protection cover, is the scanning angle S21 parameter of the receiving antenna with antenna protection cover and plasma, and G′ is the calibration gain of the pure antenna.

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