Electromagnetic wave vector distribution measurement system based on laser ionization of air

Abstract

The application relates to an electromagnetic wave vector distribution measuring system based on laser ionized air. The design generates plasma by laser ionizing air, the generated plasma interacts with the electromagnetic wave to be measured, the spatial position of the laser ionized air is adjusted by using a light source control system, electromagnetic wave signals after the plasma at different positions interacts with the electromagnetic wave to be measured are received, and the measurement of the amplitude and phase distribution of the electromagnetic wave at any position in space is realized. The application can not only realize the rapid measurement of the spatial electromagnetic wave distribution, but also avoid the influence of other fixtures, measuring media and the like on the electromagnetic wave distribution at the measured position, so that the application is a kind of rapid, flexible and accurate measurement means.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave measurement, specifically relating to an electromagnetic wave vector distribution measurement system based on laser ionization of air. Background Technology

[0002] Obtaining the spatial distribution of electromagnetic waves is an important research topic in the field of electromagnetic measurement, with wide applications in antenna measurement, electromagnetic compatibility, and radar imaging. Currently, the most widely used method for measuring the spatial distribution of electromagnetic waves is the use of a near-field measurement probe combined with a mechanical device. The near-field measurement probe is typically an open waveguide, connected to a signal receiving and processing device such as a vector network analyzer. The open waveguide is fixed to a mechanical slide, which is then moved in space to sample and measure the electromagnetic wave distribution in the sampled area. However, due to the metallic structure of the open waveguide, the distribution of electromagnetic waves in the measured area can be affected. Furthermore, the measurement time for scanning using a mechanical slide to control the probe movement is usually very long; when the measured area is large, a single measurement may take tens of minutes or even several hours. The movement of the connecting cables while the probe is being moved by the mechanical slide can also adversely affect the accuracy of the test results.

[0003] To address the problems of near-field probe scanning electromagnetic wave measurement systems, J.R. H. Ichmond published "A Modulated Scattering Technique for Measurement of Field Distributions," IRE Transactions on Microwave Theory and Techniques 3(4), 13-15 (1955), proposing a modulated scattering method to measure electromagnetic wave distribution. This method has a smaller "equivalent probe" size, which effectively improves the measurement resolution and reduces interference with the field under test. At the same time, the scattering principle-based measurement method eliminates the need for connecting cables, avoiding errors caused by the movement of cables during the test. However, this method still cannot avoid dependence on mechanical moving devices and still cannot avoid the problem of long single measurement times. In “Real-time imaging of electromagnetic fields”, Opt. Express 30(12), 20431-20440(2022), Ma Liao et al. proposed using silicon wafers as the measurement medium and utilizing photoconductivity to measure the spatial electromagnetic wave distribution. This measurement method uses laser irradiation on the silicon wafer, and the plasma formed in the irradiated area is regarded as an “equivalent probe”. With the help of an optical path control system, the measurement of the spatial distribution of electromagnetic waves can be realized quickly. However, due to the introduction of silicon wafers, electromagnetic waves at the measurement location will be interfered with, affecting the accuracy of the measurement results.

[0004] When an ultrashort pulse laser is focused at a specific location in space, the field strength at the focal point exceeds the Coulomb field of the internal interactions of atoms. Electrons will break free from the atomic bonds, and the air in the focused region will be excited into plasma. According to the Lorentz-Drude model, the complex permittivity of the plasma generated by the excited air changes, and the response of the electromagnetic wave will change when the electromagnetic wave passes through this plasma region. Based on this phenomenon, this invention proposes using a laser to scan and excite plasma point by point in space, collecting the response of the electromagnetic wave to be measured at different locations, and realizing the measurement of the spatial vector distribution of electromagnetic waves. This measurement method does not require the introduction of any measurement medium, ensuring the accuracy of the test results. The laser can be focused at any location in space through a light source control system to obtain multidimensional electromagnetic wave vector spatial distribution information. Compared with the traditional mechanical slide table that carries the probe movement, the change speed of the beam's spatial focusing position is faster, improving test efficiency. The cable does not need to move during the test, avoiding errors introduced by cable movement. This measurement system can achieve efficient, fast, and accurate measurement of electromagnetic wave vector distribution. Summary of the Invention

[0005] The purpose of this invention is to propose an electromagnetic wave vector distribution measurement system based on laser ionization of air. This measurement system requires no other test medium or measurement probe, thus avoiding interference from electromagnetic waves in the area under test. The test system does not require mechanical slides or other devices, greatly improving test efficiency. The test area can be flexibly set, and combined with the light source control system, it can realize multidimensional electromagnetic wave vector distribution measurement in any spatial location. During testing, the connecting cable does not need to move, avoiding test errors introduced by the test cable.

[0006] To achieve the above objectives, the specific solution of the present invention is as follows: it includes a laser light source; a light source control system; an antenna; a signal receiving and processing device; and a host control system.

[0007] The laser source is used to generate laser light capable of ionizing air;

[0008] The light source control system is used to control the position of the laser ionizing the air in space;

[0009] The antenna is used to receive the signal after the plasma generated by laser ionization of air interacts with the electromagnetic wave to be measured.

[0010] The signal receiving and processing device is connected to the antenna and is used to process the electromagnetic wave signals received by the antenna.

[0011] The upper-level control system is connected to the receiving device and the light source control system, and is used to control the light source control system and the receiving device to work together to realize the vector signal acquisition of the electromagnetic wave to be measured.

[0012] The laser source is a pulsed laser source, and the laser intensity can reach a level that produces a visible plasma flash within the focusing area.

[0013] The light source control system includes a power control module, a focal length control module, and a beam path control module, used to control the laser irradiation power and the spatial position of the focused ionized air.

[0014] The antenna's operating bandwidth covers the frequency of the electromagnetic wave to be measured, and the signal receiving and processing device can receive the signal of the electromagnetic wave frequency to be measured and process the received signal into the corresponding amplitude and phase.

[0015] The upper-level control system can send instructions to the light source control system and signal receiving and processing device to coordinate synchronous measurement and complete the measurement of the amplitude and phase distribution of the electromagnetic wave under test through laser spatial scanning.

[0016] The steps for measuring electromagnetic wave distribution using this system are as follows:

[0017] Step 1: Set the spatial scanning area of ​​the electromagnetic wave to be measured through the host control system;

[0018] Step 2: Set the receiving parameters of the signal receiving and processing device through the upper control system;

[0019] Step 3: The host control system sends a command to the light source control system to control the laser to focus on the first position in the scanning area. The laser ionizes the air at the first position in the scanning area, forming a visible plasma flash.

[0020] Step 4: The laser-ionized plasma interacts with the electromagnetic wave to be measured, and the antenna and signal receiving and processing device receive the electromagnetic wave signal.

[0021] Step 5: The signal receiving and processing device receives the electromagnetic wave signal after the interaction between the electromagnetic wave to be measured and the plasma, and resolves the signal into an amplitude and phase representation.

[0022] Step 6: Repeat steps 3-5. The upper control system controls the laser to focus on the next position in the scanning area until the scanning of the entire space area is completed. Finally, the electromagnetic wave amplitude and phase distribution of the space area can be obtained.

[0023] The beneficial effects of this invention are as follows: Compared with existing measurement technologies, the measurement device of this invention is simple and convenient, requiring no near-field measurement probe or measurement medium, and will not interfere with the electromagnetic wave distribution of the area under test; it eliminates the need for displacement devices such as mechanical sliding tables, greatly improving measurement speed and reducing the measurement time from tens of minutes or even hours to just a few minutes; the measurement area can be flexibly set, and combined with a light source control system, multidimensional electromagnetic wave vector distribution measurement can be achieved in any area of ​​space; since the receiving antenna does not need to move during measurement, there is no inaccuracy in the measurement results due to the movement of connecting cables. This invention is a highly efficient and accurate electromagnetic wave measurement method. Attached Figure Description

[0024] Figure 1 This is the electromagnetic wave vector distribution measurement system based on laser-ionized air according to the first embodiment of the present invention;

[0025] Figure 1 Explanation of reference numerals in the attached figures:

[0026] 1-Laser source; 2-Light source control system; 3-Upper control system; 4-Signal receiving and processing device; 5-Antenna; 6-Laser beam; 7-Plasma formed by laser ionization of air; 8-Electromagnetic wave signal after the interaction between plasma and the electromagnetic wave to be measured; 9-Spatial region to be measured; 10-Laser scanning trajectory; 11-Electromagnetic wave to be measured. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but this is not to limit the scope of the invention to this.

[0028] like Figure 1 As shown, the electromagnetic wave vector distribution measurement system based on laser ionization of air in this embodiment includes: a laser source 1 for generating laser light capable of ionizing air; a source control system 2 for controlling the position of the laser beam and changing its position in the ionized air in space; an antenna 5 for receiving the signal after the plasma generated by laser ionization of air interacts with the electromagnetic wave to be measured; a signal receiving and processing device 4 for processing the electromagnetic wave signal received by the antenna; and a host control system 3 for controlling the source control system and the receiving device to work together to realize the vector signal acquisition of the electromagnetic wave to be measured.

[0029] When the electromagnetic wave vector distribution measurement system based on laser ionization of air is in operation, for the measurement of the electromagnetic wave 11 to be measured, the measurement space region 9 should first be determined. In particular, the measurement space region includes, but is not limited to, the form in this embodiment; in practice, the measurement region can be set to any shape and any position.

[0030] The host control system 3 sends instructions to the light source control device 2 to set the spatial scanning trajectory 7 of the laser beam 6. In particular, the spatial scanning trajectory of the laser beam includes, but is not limited to, the case in this embodiment, and can be set as an arbitrary scanning trajectory within the space to be measured.

[0031] The upper control system 3 sends instructions to the signal receiving and processing device 4 to set parameters such as the operating frequency of the signal receiving and processing device.

[0032] The laser beam 6 is focused at the first position point of the scanning trajectory, ionizing the air to form plasma 7. The plasma 7 interacts with the electromagnetic wave 11 to be measured, and the resulting electromagnetic wave signal 8 is received by the antenna 5. After processing by the signal receiving and processing device 4, the amplitude and phase information of the spatial position are obtained.

[0033] The host control system 3 continues to send commands to the light source control device 2, controlling the focusing position of the laser beam 6 to move along the scanning trajectory 10. Each movement generates plasma 7 in space. The electromagnetic wave signal 8 generated by the interaction between the plasma 7 and the electromagnetic wave 11 to be measured is received by the receiving antenna 5 and the signal receiving and processing device 4. This process is repeated continuously until the measurement and collection of all position signals on the scanning trajectory 10 are completed. Thus, the spatial distribution of the electromagnetic wave amplitude and phase within the measurement area can be obtained.

Claims

1. A system for measuring the electromagnetic wave vector distribution based on laser-ionized air, characterized in that, No mechanical slide, measuring medium, laser source, light source control system, antenna, signal receiving and processing device, or upper control system are required; The laser source is used to generate laser light capable of ionizing air; The light source control system is used to control the position of the laser ionizing the air in space; the light source control system includes a power control module, a focal length control module and a beam path control module, used to control the irradiation power of the laser and the spatial position of the focused ionized air. The antenna is used to receive the signal after the plasma generated by laser ionization of air interacts with the electromagnetic wave to be measured. The signal receiving and processing device is connected to the antenna and is used to process the electromagnetic wave signals received by the antenna. The upper-level control system is connected to the signal receiving and processing device and the light source control system, and is used to control the light source control system and the signal receiving and processing device to work together to realize the vector signal acquisition of the electromagnetic wave to be measured. The method for measuring the electromagnetic wave vector distribution using the system includes the following steps: Step 1: Set the spatial scanning area of ​​the electromagnetic wave to be measured through the host control system; Step 2: Set the receiving parameters of the signal receiving and processing device through the upper control system; Step 3: The host control system sends a command to the light source control system to control the laser to focus on the first position in the scanning area. The laser ionizes the air at the first position in the scanning area, forming a visible plasma flash. Step 4: The laser-ionized plasma interacts with the electromagnetic wave to be measured, and the antenna and signal receiving and processing device receive the electromagnetic wave signal. Step 5: The signal receiving and processing device receives the electromagnetic wave signal after the interaction between the electromagnetic wave to be measured and the plasma, and resolves the signal into an amplitude and phase representation. Step 6: Repeat steps 3-5. The upper control system controls the laser to focus on the next position in the scanning area until the scanning of the entire space area is completed. Finally, the electromagnetic wave amplitude and phase distribution of the space area can be obtained.

2. The electromagnetic wave vector distribution measurement system based on laser-ionized air according to claim 1, characterized in that: The laser source is a pulsed laser source, and the laser intensity can reach a level that produces a visible plasma flash within the focusing area.

3. The electromagnetic wave vector distribution measurement system based on laser-ionized air according to claim 1, characterized in that: The antenna's operating bandwidth covers the frequency of the electromagnetic wave to be measured, and the signal receiving and processing device can receive the signal of the electromagnetic wave frequency to be measured and process the received signal into the corresponding amplitude and phase.

4. The electromagnetic wave vector distribution measurement system based on laser-ionized air according to claim 1, characterized in that: The upper-level control system can send instructions to the light source control system and signal receiving and processing device to coordinate synchronous measurement and complete the measurement of the amplitude and phase distribution of the electromagnetic wave under test through laser spatial scanning.

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