Method for testing electromagnetic characteristics of large vacuum dark chamber plasma environment

Abstract

This invention discloses an electromagnetic characteristic testing method for a large-scale vacuum anechoic chamber plasma environment, belonging to the field of microwave testing technology. The method includes: setting up an antenna movement device, an antenna protective cover, and a transmitting antenna in a large anechoic chamber; evacuating the large anechoic chamber to a vacuum and providing a stable plasma environment through a plasma source inlet within the chamber; connecting the transmitting and receiving antennas to a vector network analyzer; connecting the vector network analyzer to a computer; and using the computer to control the vector network analyzer to acquire antenna data in the large-scale vacuum anechoic chamber plasma environment, calculating the gain pattern and transmittance. This invention provides a stable large-scale anechoic chamber plasma environment, ensuring the repeatability of electromagnetic characteristic testing. The antenna movement device ensures that the movement state of the receiving antenna at every angle can be obtained, enabling rapid and large-scale acquisition of stable plasma antenna data.

Description

Technical Field

[0001] This invention belongs to the field of microwave testing technology, specifically relating to a method for testing electromagnetic properties in a large vacuum anechoic chamber plasma environment. Background Technology

[0002] In rapidly evolving plasmas, electromagnetic wave propagation and plasma interaction are important research areas, especially the "blackout" phenomenon during spacecraft reentry. The plasma sheath that forms on the spacecraft surface can shield signals, leading to navigation and telemetry interruptions. Therefore, solving the problem of information transmission under the plasma sheath has become a hot topic in aerospace.

[0003] Currently, there are three main types of environments commonly used for experiments on the transmission and radiation of electromagnetic waves in plasma: The first type is the shock tube based on the principle of high-speed aerodynamics. However, the transmission and radiation of electromagnetic waves in plasma places great demands on the stability, continuity, and dynamic range of the plasma. Moreover, the plasma generated by the shock tube has a limited duration, and the arc wind tunnel cannot quickly generate dynamic plasma. In addition, the electron temperature is too high, which is not conducive to the experiment. The second type is the arc wind tunnel, which forms a plasma beam by heating the gas to the ionization temperature. However, the existing experimental devices are small in scale and do not have the conditions for far-field testing at low frequencies. The third type is glow discharge plasma generated in a low-pressure non-equilibrium environment. However, the electron density of glow discharge plasma is too small.

[0004] In recent years, a series of studies on antenna, propagation, and suppression technologies under plasma sheathing have been carried out using novel cold plasma sources, mainly focusing on miniaturization, controllability, and applicability to general laboratory environments. However, plasma-generating devices or instruments for moving antennas are usually bulky, difficult to operate, and have high difficulty in repeatability experiments, which brings significant challenges to the testing of radiation patterns. Moreover, existing conventional testing methods often cannot take into account the testing conditions of a good anechoic chamber, 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 combines high accuracy, good repeatability, and sufficient flexibility to adapt to diverse testing environments. Summary of the Invention

[0006] In view of the above-mentioned shortcomings in the prior art, the electromagnetic characteristic testing method for large vacuum anechoic chamber plasma environment provided by the present invention solves the problems that the plasma environment is difficult to maintain and the electromagnetic characteristic testing conditions are not met.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by this invention is: an electromagnetic characteristic testing method for large-scale vacuum anechoic chamber plasma environments, comprising the following steps:

[0008] S1: Set up an antenna movement device and an antenna protective cover in a large anechoic chamber, and install a receiving antenna on the antenna movement device and a transmitting antenna inside the antenna protective cover;

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

[0010] S3: Evacuate the large anechoic chamber to a vacuum and provide a stable plasma environment through the plasma source inlet in the large anechoic chamber to obtain the plasma environment of the large vacuum anechoic chamber;

[0011] S4: Using a computer to control a vector network analyzer to acquire antenna data in a large vacuum anechoic chamber plasma environment;

[0012] S5: Based on the antenna data, the gain and transmittance of the electromagnetic wave are calculated using the relative method, and the electromagnetic characteristics of the plasma environment in the large vacuum anechoic chamber are tested.

[0013] The beneficial effects of this invention are as follows: This invention can provide a stable large-scale anechoic chamber plasma environment, ensuring the repeatability of electromagnetic characteristic tests, and can adjust the plasma parameters to achieve electromagnetic tests at different electron density levels; at the same time, this invention proposes two wiring methods to address the problem of large-scale environments, enabling the acquisition of high-quality S-parameter data; this invention also directly connects the computer to a vector network analyzer to quickly collect large amounts of data and process the data to obtain highly accurate data; in addition, this invention also collects three states of sweep angle S21 parameters, and through the antenna motion device, it can ensure that the motion state of the receiving antenna at each angle can be accurately obtained, and the relative method is used to obtain the antenna radiation pattern and the transmittance of electromagnetic waves in the plasma.

[0014] Furthermore: the transmitting antenna and the receiving antenna are directly opposite each other;

[0015] Both the receiving antenna and the transmitting antenna are ultra-wideband transceiver antennas.

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

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

[0018] The beneficial effects of the above-mentioned further scheme are: by using a receiving antenna, a transmitting antenna, an antenna moving device, and an antenna protective cover, electromagnetic testing can be performed under three conditions: no plasma and no cover, no plasma and cover, and plasma and cover.

[0019] Furthermore: the specific connection methods for connecting both the transmitting antenna and the receiving antenna to the vector network analyzer include:

[0020] The transmitting antenna is connected to the second port of the vector network analyzer via the lower through-cabin flange.

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

[0022] The beneficial effects of the above-mentioned further solution are as follows: connecting the antenna to the vector network analyzer through the lower and upper through-flanges can reduce the impact of long cables on the test results of the vector network analyzer and ensure data accuracy.

[0023] Furthermore: the specific connection steps for connecting the vector network analyzer to the computer include:

[0024] Find the IP address of the vector network analyzer and connect it to the computer using a network cable;

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

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

[0027] The beneficial effects of the above-mentioned further solutions are as follows: by controlling the vector network analyzer by computer, the vector network analyzer can be remotely controlled to acquire antenna data and the acquisition can be automated, thereby improving the efficiency of antenna data acquisition, shortening the test time, and reducing human error.

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

[0029] S301: Seal a large darkroom and pump the air pressure in the large darkroom to the load-bearing ultimate vacuum to obtain a large vacuum darkroom;

[0030] S302: Stable plasma is ejected through the plasma source inlet in the large anechoic chamber until the large vacuum anechoic chamber reaches the set 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 anechoic chamber plasma environment.

[0032] The beneficial effects of the above-mentioned further scheme are: by ejecting stable plasma through the plasma source inlet, a stable plasma environment can be provided for the large vacuum anechoic chamber, ensuring the stability of the test data.

[0033] Furthermore, a stable plasma environment is obtained as follows:

[0034] A1: A plasma with a fixed electron density is ejected through the plasma source inlet, and the curve of the plasma's electron density changing over time is measured.

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

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

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

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

[0039] Furthermore, the expressions for the gain and transmittance are as follows:

[0040]

[0041]

[0042] Where G1 is the antenna gain with a radome and no plasma, G2 is the antenna gain with a radome and with plasma, and T is the transmittance of electromagnetic waves in the plasma. The sweep angle S21 parameter for the receiving antenna. The sweep angle S21 parameter for the receiving antenna with an added antenna cover. The sweep angle S21 parameter is the receiving antenna with an added antenna radome and plasma, and G′ is the calibration gain of the pure antenna.

[0043] The beneficial effects of the above-mentioned further scheme are: 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 electromagnetic waves in the plasma can be obtained. Attached Figure Description

[0044] Figure 1 A flowchart of an electromagnetic property testing method for large-scale vacuum anechoic chamber plasma environments;

[0045] Figure 2 This is a schematic diagram of the plasma environment in the large vacuum anechoic chamber of the present invention. Detailed Implementation

[0046] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0047] In this invention, the following terms are used to describe:

[0048] S11 parameter: In the field of radio frequency, S11 refers to the reflection coefficient, which is used to describe the ability of a device or system port to reflect incident signals. It is generally used to measure the input impedance matching of antennas, radio frequency devices or circuits. When the value of S11 is close to 0, it means that 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 input to output.

[0050] Radiation pattern: A radiation pattern, also known as a radiation pattern or antenna radiation pattern, is a spatial distribution map that shows the antenna's radiation capability. It usually displays the antenna's relative gain or radiation intensity in different directions.

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

[0052] like Figure 1 As shown, a method for testing electromagnetic properties in a large vacuum anechoic chamber plasma environment includes the following steps:

[0053] S1: Set up an antenna movement device and an antenna protective cover in a large anechoic chamber, and install a receiving antenna on the antenna movement device and a transmitting antenna inside the antenna protective cover;

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

[0055] S3: Evacuate the large anechoic chamber to a vacuum and provide a stable plasma environment through the plasma source inlet in the large anechoic chamber to obtain the plasma environment of the large vacuum anechoic chamber;

[0056] S4: Using a computer to control a vector network analyzer to acquire antenna data in a large vacuum anechoic chamber plasma environment;

[0057] S5: Based on the antenna data, the gain and transmittance of the electromagnetic wave are calculated using the relative method, and the electromagnetic characteristics of the plasma environment in the large vacuum anechoic chamber are tested.

[0058] In one embodiment of the invention, the antenna protective cover has good wave transmission and heat insulation properties, enabling it to withstand extreme high temperatures during testing. A suitable antenna clamping device is used to mount the transmitting antenna inside the antenna protective cover, protecting it. The antenna protective cover is then installed in a large vacuum anechoic chamber using a protective cover fixing device. An antenna moving device and the antenna protective cover are set up in the large anechoic chamber, and a receiving antenna is mounted on the antenna moving device, ensuring the transmitting and receiving antennas are aligned. Both the transmitting and receiving antennas are ultra-wideband transceiver antennas. By controlling the antenna moving device, the receiving antenna can be positioned at different angles to receive antenna signals at different incident angles. Furthermore, the antenna protective cover can be disassembled and added to accommodate different electromagnetic testing conditions, allowing for electromagnetic testing with and without the cover.

[0059] In S2, both the transmitting and receiving antennas are connected to the vector network analyzer. Considering the large volume of the large vacuum anechoic chamber and the long required wiring cables, the specific connection method of this invention includes:

[0060] The transmitting antenna is connected to the second port of the vector network analyzer via the lower through-flange, which enables the measurement of the antenna's S11 parameters, reduces the impact of long cables on the measurement results of the vector network analyzer, and allows for the calibration of the vector network analyzer after connection.

[0061] The transmitting antenna is connected to the first port of the vector network analyzer via the lower through-cabin flange, and the receiving antenna is connected to the second port of the vector network analyzer via the upper through-cabin flange. This allows for the measurement of the antenna's S21 parameters, reduces the impact of long cables on the measurement results of the vector network analyzer, and enables the calibration of the vector network analyzer after connection.

[0062] In S2, the vector network analyzer is connected to the computer. This invention directly connects the vector network analyzer to the computer, which can improve the acquisition speed, reduce the number of plasma discharges, and enable rapid acquisition and storage of 5 frames of data via the computer. The specific connection steps of this invention include:

[0063] Find the IP address of the vector network analyzer and connect it to the computer using a network cable;

[0064] Locate the Ethernet network on your computer and change the IP address in Internet Protocol version 4 over Ethernet to connect the vector network analyzer to the computer.

[0065] Open the control software corresponding to the vector network analyzer on the computer, and connect the computer to the vector network analyzer through the control software. At this time, you can control the vector network analyzer by inputting the set data format and type on the computer; perform automated acquisition, improve antenna data acquisition efficiency, shorten test time, and reduce human error.

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

[0067] Before officially starting the electromagnetic test, it is necessary to ensure that a stable plasma environment is emitted from the plasma source inlet. The method for obtaining this environment is as follows:

[0068] A1: A plasma with a fixed electron density is ejected through the plasma source inlet, and the curve of the plasma's electron density changing over time is measured.

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

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

[0071] A4: Based on the overlapping electron density stabilization time period, a stable plasma environment is obtained. When testing the electromagnetic properties of plasma, selecting this overlapping electron density stabilization time period for data acquisition can yield data under a stable plasma environment.

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

[0073] S301: Seal a large darkroom and pump the air pressure in the large darkroom to the load-bearing ultimate vacuum to obtain a large vacuum darkroom;

[0074] S302: Stable plasma is ejected through the plasma source inlet in the large anechoic chamber until the large vacuum anechoic chamber reaches the set 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 anechoic chamber plasma environment.

[0076] In S4, a computer is used to control a vector network analyzer to acquire antenna data in a large vacuum anechoic chamber plasma environment.

[0077] In one embodiment of the invention, the antenna protective cover can be disassembled and installed, and the plasma source inlet can be opened and closed, thereby enabling electromagnetic testing under three conditions: no plasma and no cover, no plasma and cover, and plasma and cover. Before conducting formal electromagnetic characteristic testing, the probe is controlled by an antenna movement device to obtain the electron density profile of the experimental area, and then the probe is removed to avoid affecting the electromagnetic test. The electron density data collected by the vector network analyzer can be used for numerical modeling to find the source of error and reduce the uncertainty of the test results. During radiation characteristic testing, the transmitting antenna is fixed and the radiation is transmitted through the antenna. The motion device moves and rotates the receiving antenna. Simultaneously, the coordinates and attitude angles corresponding to each angle of the receiving antenna are calculated in advance and directly input into the control system of the antenna motion device. Within a limited time, the S21 parameters within the set angle range, such as the S21 parameters within the range of -13° to 13°, are obtained quickly and accurately. The test is repeated, and five frames of data are quickly acquired by a vector network analyzer controlled by a computer to obtain multiple sets of antenna data. Data with large differences are removed, and the average value of the remaining data is taken as the final S11 and S21 parameters, which further improves the data quality and reduces the impact of plasma temporal instability on the test results.

[0078] In one embodiment of the present invention, such as Figure 2 The diagram shown is a schematic of the plasma environment in the large vacuum anechoic chamber of the present invention. The diagnostic area is a plasma environment, and the antenna moving device is a slide rail moving device. Other antenna moving devices can also be selected. By moving the device, the receiving angle of the receiving antenna can be changed, so that the receiving antenna can receive antenna signals at different incident angles and obtain antenna data.

[0079] The antenna data includes: S11 parameters of the transmitting antenna and S21 parameters of the receiving antenna. It also allows for the disassembly and installation of the antenna protective cover, the opening and closing of the plasma source inlet, and the control of the antenna moving device to adjust the angle and state of the receiving antenna. This yields the S21 parameters of the receiving antenna, the S21 parameters of the receiving antenna with the antenna protective cover, and the S21 parameters of the receiving antenna with both the antenna protective cover and plasma. Based on the antenna data, the antenna gain and transmittance are calculated. The expressions for gain and transmittance are as follows:

[0080]

[0081] Where G1 is the antenna gain with a radome and no plasma, G2 is the antenna gain with a radome and with plasma, and T is the transmittance of electromagnetic waves in the plasma. The sweep angle S21 parameter for the receiving antenna. The sweep angle S21 parameter for the receiving antenna with an added antenna cover. The sweep angle S21 parameter of the receiving antenna with added antenna cover and plasma is given, and G′ is the calibration gain of the pure antenna. 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. Based on the calculated antenna gain and transmittance, the radiation pattern of the antenna and the transmittance of electromagnetic waves in the plasma are further obtained, thus completing the electromagnetic characteristic test of the plasma environment in the large vacuum anechoic chamber.

[0082] The beneficial effects of this invention are as follows: This invention can provide a stable large-scale anechoic chamber plasma environment, ensuring the repeatability of electromagnetic characteristic tests, and can adjust the plasma parameters to achieve electromagnetic tests at different electron density levels; at the same time, this invention proposes two wiring methods to address the problem of large-scale environments, enabling the acquisition of high-quality S-parameter data; this invention also directly connects the computer to a vector network analyzer to quickly collect large amounts of data and process the data to obtain highly accurate data; in addition, this invention also collects three states of sweep angle S21 parameters, and through the antenna motion device, it can ensure that the motion state of the receiving antenna at each angle can be accurately obtained, and the relative method is used to obtain the antenna radiation pattern and the transmittance of electromagnetic waves in the plasma.

Claims

1. A method for testing electromagnetic properties in a large-scale vacuum anechoic chamber plasma environment, characterized in that, Includes the following steps: S1: Set up an antenna movement device and an antenna protective cover in a large anechoic chamber, and install a receiving antenna on the antenna movement device and a transmitting antenna inside the antenna protective cover; S2: Connect both the transmitting and receiving antennas to the vector network analyzer, and connect the vector network analyzer to the computer; S3: Evacuate the large anechoic chamber to a vacuum and provide a stable plasma environment through the plasma source inlet in the large anechoic chamber to obtain the plasma environment of the large vacuum anechoic chamber; S4: Using a computer to control a vector network analyzer to acquire antenna data in a large vacuum anechoic chamber plasma environment; S5: Based on the antenna data, the gain and transmittance of the electromagnetic wave are calculated using the relative method, and the electromagnetic characteristics test of the plasma environment in the large vacuum anechoic chamber is completed. The specific steps of S3 are as follows: S301: Seal a large darkroom and pump the air pressure in the large darkroom to the load-bearing ultimate vacuum to obtain a large vacuum darkroom; S302: Stable plasma is ejected through the plasma source inlet in the large anechoic chamber until the large vacuum anechoic chamber reaches the set 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 anechoic chamber plasma environment. The stable plasma environment is obtained as follows: A1: A plasma with a fixed electron density is ejected through the plasma source inlet, and the curve of the plasma's electron density changing over time is measured. A2: On the curve of plasma electron density changing with time, select a smooth curve and mark it to obtain the stable time period of plasma electron density. A3: Repeat A1 to A2 several times to obtain several stable plasma electron density time periods, and select the overlapping stable electron density time periods. A4: A stable plasma environment is obtained based on the stable time period of the overlapping electron density; The expressions for the gain and transmittance are as follows: in, For the gain of a plasma-free antenna with a radome, For the gain of a plasma-covered antenna, The transmissivity of electromagnetic waves in plasma. The sweep angle S21 parameter for the receiving antenna. The sweep angle S21 parameter for the receiving antenna with an added antenna cover. The sweep angle S21 parameter of the receiving antenna with added antenna cover and plasma. This is the calibration gain of the antenna alone.

2. The electromagnetic property testing method for large-scale vacuum anechoic chamber plasma environments according to claim 1, characterized in that, The transmitting antenna and the receiving antenna are facing each other; Both the receiving antenna and the transmitting antenna are ultra-wideband transceiver antennas. The antenna movement device is used to control the receiving antenna to be in different angle states; The antenna protective cover is used to protect the transmitting antenna.

3. The electromagnetic characteristic testing method for large-scale vacuum anechoic chamber plasma environments according to claim 2, characterized in that, The specific connection methods for connecting both the transmitting and receiving antennas to the vector network analyzer include: The transmitting antenna is connected to the second port of the vector network analyzer via the lower through-cabin flange. The transmitting antenna is connected to the first port of the vector network analyzer via the lower through-cabin flange, and the receiving antenna is connected to the second port of the vector network analyzer via the upper through-cabin flange.

4. The electromagnetic property testing method for large-scale vacuum anechoic chamber plasma environments according to claim 1, characterized in that, The specific steps for connecting the vector network analyzer to the computer include: Find the IP address of the vector network analyzer and connect it to the computer using a network cable; Check the Ethernet on the computer and change the IP address via Ethernet to connect the vector network analyzer to the computer network; Open the control software on your computer and use it to connect the computer to the vector network analyzer.

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