A near-field positioning system and method for radiation disturbance sources of multiple unit trains

Abstract

The present invention discloses a near-field positioning system and method for a radiation interference source of a multiple unit train, including: an electric field probe, a magnetic field probe, a preamplifier, and a portable radiation analyzer. By using the electric field probe and the magnetic field probe to collect the electromagnetic field information of the target area in real time, the present invention can expand the low-frequency bandwidth of the electromagnetic field probe through the corresponding preamplifier without sacrificing the spatial resolution of the probe. The lowest cut-off frequency reaches 500 KHz, meeting the detection requirements of the low-frequency radiation interference source of the multiple unit train in the range of 1 MHz - 30 MHz. Through the positioning method, the near-field tracking of the radiation interference source of the multiple unit train is gradually carried out to achieve the near-field positioning of the interference source.

Description

Technical Field

[0001] The present invention belongs to the technical field of rail transit, and particularly relates to a near-field positioning system and method for radiation disturbance sources of multiple unit trains. Background Art

[0002] As an important part of China's railway transportation system, multiple unit trains have become the backbone of railway passenger transport with their relatively high speeds. However, the relatively high speeds have also led to a continuous increase in the traction current in the multiple unit trains. Compared with the large amount of high-frequency disturbance caused by phase separation, the traction disturbance caused by the continuous increase in the traction current of the traction equipment is mostly low-frequency signals below 30 MHz. Compared with high-frequency signals, the generated low-frequency interference signals often have a serious impact on the CTCS communication system of multiple unit trains.

[0003] Among them, the most typical one is the train communication device BTM. The BTM activates the balise installed on the railway by sending a 27 MHz downlink signal. After the balise is activated, it sends relevant information such as the train operation line to the BTM through a 4.23 MHz uplink signal, and is demodulated and decoded by the BTM device, and the data is sent to the ATP to assist the normal operation of the train.

[0004] In addition to the traction equipment, line crosstalk and rail return current will also generate low-frequency disturbances, which will have a serious impact on the communication of the BTM device. In order to be able to detect these low-frequency disturbances in a timely manner, a system and its supporting positioning method are required to quickly locate the radiation disturbance sources of multiple unit trains, and at the same time provide data support for electromagnetic protection. Summary of the Invention

[0005] The technical problem to be solved by the present invention is how to quickly and accurately locate the radiation disturbance sources of multiple unit trains, and provide a near-field positioning system and method for radiation disturbance sources of multiple unit trains.

[0006] The present invention is realized as follows. A near-field positioning system for radiation disturbance sources of multiple unit trains, the positioning system includes: an electric field probe, a magnetic field probe, a preamplifier, and a portable radiation analyzer. Among them,

[0007] The electric field probe is made of a flexible coaxial cable. Part of the shielding layer is peeled off, and an equivalent capacitance is formed between the bare conductor and the outer shielding layer to sense the change of the electric field and generate a corresponding induced current;

[0008] The magnetic field probe is made of a flexible coaxial cable. The cable is bent to form a ring structure, and at the same time, the shielding layer of the magnetic field cable is cut off at the top of the magnetic field probe;

[0009] The preamplifier includes a low-input-impedance amplifier and a high-input-impedance amplifier. The high-impedance gain amplifier is used to expand the low-frequency characteristics of the electric field probe and is installed at the output end of the electric field probe. The low-impedance gain amplifier is used to expand the low-frequency characteristics of the magnetic field probe and is installed at the output end of the magnetic field probe.

[0010] The portable radiation analyzer collects the output signals of the preamplifier and performs real-time FFT / DFT spectral analysis on the collected signals, combines the electromagnetic field probes to find the radiation interference source, and completes the positioning of the radiation interference source.

[0011] Furthermore, the size and resolution of the electric field probe are changed by the length of the exposed conductor; the size and resolution of the magnetic field probe are changed according to the cross-sectional area of the cable.

[0012] Furthermore, the portable radiation analyzer performs discrete Fourier transform or fast discrete Fourier transform on the data measured by the electric field probe or the magnetic field probe to obtain the frequency-domain curve of the collected voltage signal, and finds the maximum point in the frequency domain of the voltage signal. This point corresponds to the strongest electric field point or the strongest magnetic field point of the measured item.

[0013] A positioning method for a near-field positioning system of a radiation interference source using a positioning system, the method includes the following steps:

[0014] Calibration of the low-frequency near-field probe, the low-frequency near-field probe includes an electric field probe and a magnetic field probe, and the antenna coefficient factor AF of the low-frequency near-field probe at 500KHz - 30MHz is obtained.

[0015] Select a large-size electric field probe to capture and determine the approximate area of the interference source, and then use a small-size electric field probe to determine the exact position of the interference source and find the area with the maximum electric field radiation intensity of the measured equipment.

[0016] Select a large-size magnetic field probe to capture and determine the approximate area of the interference source, and then use a small-size magnetic field probe to determine the exact position of the interference source and find the area with the maximum magnetic field intensity of the measured equipment using the magnetic field probe.

[0017] Among them, by performing discrete Fourier transform or fast discrete Fourier transform on the data measured by the electric field probe and the magnetic field probe using the portable radiation analyzer, the frequency-domain relationship of the voltage signal at each point is obtained. As the measurement range moves, a frequency-domain curve of the collected voltage signal is formed. According to the frequency-domain curve, the maximum point in the frequency domain of the voltage signal is found. This point corresponds to the strongest electric field point or the strongest magnetic field point of the measured item.

[0018] Furthermore, the antenna coefficient factor AF satisfies that within the target frequency range of 500KHz - 30MHz, as the test frequency increases, the obtained antenna coefficient factor basically shows a flat change and AF remains basically unchanged. Among them, V is the voltage and E is the electromagnetic field strength.

[0019] Furthermore, the portable radiation analyzer calculates the true electric field value or magnetic field value corresponding to the strongest electric field point or the strongest magnetic field point by using the antenna coefficient factor obtained through calibration.

[0020] Furthermore, during detection, the electric field probe and the magnetic field probe are attached to the surface of the device under test for detection. Compared with the prior art, the advantages of the present invention are as follows:

[0021] The present invention can not only accurately locate the radiation interference source of the multiple unit train, but also the whole set of system abandons traditional devices such as spectrum analyzers, greatly reducing the volume of the system. It can detect blind spots such as device gaps that are inconvenient to detect by traditional positioning devices in the past, realize a comprehensive investigation of the train radiation harassment source, and quickly and accurately locate the radiation harassment source of the multiple unit train. Description of the Drawings

[0022] Figure 1 is the system structure block diagram provided by the embodiment of the present invention;

[0023] Figure 2 is the structural schematic diagram of the magnetic field probe provided by the embodiment of the present invention;

[0024] Figure 3 is the structural schematic diagram of the electric field probe provided by the embodiment of the present invention. Detailed Embodiments

[0025] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] Refer to Figure 1 As shown, the present invention provides a near-field positioning system for the radiation harassment source of a multiple unit train. The test system includes: an electric field probe 1, a magnetic field probe 2, a preamplifier 3, and a portable radiation analyzer 4.

[0027] The electric field probe is made of a flexible coaxial cable. Part of the shielding layer is peeled off, and an equivalent capacitance is formed between the exposed conductor and the outer shielding layer to sense the change of the electric field and generate a corresponding induced current;

[0028] The magnetic field probe is made of a flexible coaxial cable. The cable is bent to form a ring structure, and at the same time, the shielding layer of the magnetic field cable is cut off at the top of the magnetic field probe;

[0029] The preamplifier includes a low input impedance amplifier and a high input impedance amplifier. The high impedance gain amplifier is used to extend the low frequency characteristics of the electric field probe and is installed at the output end of the electric field probe. The low impedance gain amplifier is used to extend the low frequency characteristics of the magnetic field probe and is installed at the output end of the magnetic field probe.

[0030] The portable radiation analyzer collects the output signal of the preamplifier and performs real-time FFT / DFT spectrum analysis on the collected signal. It combines with the electromagnetic field probe to find the radiation interference source and complete the positioning of the radiation interference source.

[0031] See also Figure 3 As shown, the electric field probe is made of a flexible coaxial cable. The outer layer of the coaxial cable 11 of the electric field probe is an insulating layer 14. A portion of the shield 12 is stripped off, and an equivalent capacitor is formed with the outer shield layer through the exposed conductor 13, which senses the change of the electric field and generates a corresponding induced current.

[0032] The cable model selected in this embodiment is RG-58 coaxial cable. After stripping off part of the shielding layer, the bare conductor forms an equivalent capacitance with the outer shielding layer, inducing the change of the electric field and generating a corresponding induced current.

[0033] In this embodiment, for the electric field probe,

[0034]

[0035] The size of C is related to the length of the exposed conductor. The longer the length, the larger C, which means the electric field probe has greater sensitivity (because, for a fixed Ez, the larger C and the larger i, the easier it is to detect anomalies). Sensitivity is also inversely proportional to resolution: higher sensitivity means lower resolution. Therefore, the smaller the electric field probe, the smaller C, the lower the sensitivity, but the higher the resolution. In this embodiment, the terms "large size" and "small size" mean that the length of the large exposed conductor is at least approximately twice the length of the small exposed conductor.

[0036] See also Figure 2 As shown, the magnetic field probe is also made of flexible coaxial cable, using a flexible coaxial cable 21 with an outer rubber insulation layer 22. The coaxial cable is bent into a ring structure, and the shielding layer of the magnetic field cable is cut at the top of the magnetic field probe, forming an exposed arc segment 23. In this embodiment, RG-58 cable is selected for ease of material selection, the same material as the electric field probe. The cable is bent into a ring structure, and the shielding layer is cut at the top of the probe to ensure that the probe is shielded from the effects of the electric field.

[0037] In order to find the source of magnetic field signal interference conveniently and accurately, this embodiment designs multiple sets of magnetic field probes of different sizes, with the probe ring diameter ranging from 1cm to 30cm, to meet the needs of the system positioning method.

[0038]

[0039] Where S is the loop area. The larger S is, the larger V is. At this time, the magnetic field probe has high sensitivity but low resolution. In this embodiment, the large size is at least more than twice the loop diameter of the small size.

[0040] The preamplifiers in this embodiment are divided into two types, namely the low-input impedance amplifier and the high-input impedance amplifier. Among them, the high-impedance gain amplifier is an in-phase proportional amplification circuit, and the circuit design is implemented using the OPA656 chip. The low-impedance gain amplifier is a transimpedance amplification circuit, and the circuit design is implemented using the AD8015 chip. Through the design of the preamplifier, the cut-off frequency of the near-field probe is effectively reduced, and at the same time, the sensitivity of the probe is improved, ensuring the accurate detection of low-frequency signals.

[0041] The portable radiation analyzer collects the low-frequency output signal of the amplifier and performs real-time FFT / DFT spectral analysis on the collected signal, combines with the electromagnetic field probe to find the radiation harassment source, and completes the positioning of the radiation harassment source.

[0042] The test method for detecting and positioning tests using this system is given:

[0043] Calibration of the low-frequency near-field probe. The low-frequency near-field probe includes an electric field probe and a magnetic field probe to obtain the antenna coefficient factor AF of the low-frequency near-field probe from 500KHz to 30MHz.

[0044] Select a large-size electric field probe to capture and determine the approximate area of the harassment source, and then use a small-size electric field probe to determine the accurate position of the harassment source and find the area with the maximum electric field radiation intensity of the equipment under test.

[0045] Select a large-size magnetic field probe to capture and determine the approximate area of the harassment source, and then use a small-size magnetic field probe to determine the accurate position of the harassment source, and use the magnetic field probe to find the area with the maximum magnetic field intensity of the equipment under test.

[0046] Among them, by using the portable radiation analyzer, the frequency-domain relationship of the voltage signal at each point is obtained through discrete Fourier transform or fast discrete Fourier transform of the data measured by the electric field probe and the magnetic field probe. As the measurement range moves, a frequency-domain curve of the collected voltage signal is formed. According to the frequency-domain curve, the maximum point of the voltage signal frequency domain is found, and this point corresponds to the strongest electric field point or the strongest magnetic field point of the item under test.

[0047] Among them, calibration of the low-frequency near-field probe is performed; referring to the electromagnetic compatibility standard, the antenna coefficient factor AF of the low-frequency near-field probe from 500KHz to 30MHz is obtained through testing with a 50Ω microstrip line, and the corresponding relationship between the obtained voltage V and the electromagnetic field strength E(H) is determined.

[0048] It is required that within the target frequency range of 500 KHz - 30 MHz, as the test frequency increases, the obtained antenna coefficient factor basically shows a flat change, and the AF basically remains unchanged. It basically meets the linear change between the input electromagnetic field intensity and the output voltage of the test probe within the target frequency, ensuring the accuracy and reliability of the subsequent test results.

[0049] When conducting actual detection, first select a near-field probe with a larger size and higher sensitivity to perform EMI testing, capture and determine the approximate area of the interference source, and then use a probe with a smaller size but higher resolution to determine the exact position of the interference source. In order to reduce the influence of the detection effect by the distance, when conducting detection, it is required that the probe be in contact with the surface of the device under test for detection.

[0050] Among them, the real-time data analysis using a portable radiation analyzer includes: obtaining the frequency-domain curve of the collected voltage signal through DFT (Discrete Fourier Transform) or FFT (Fast Fourier Transform), and finding the maximum point in the frequency domain of the voltage signal. This point corresponds to the strongest electric field point (magnetic field point) of the item under test. At the same time, the true electric field (magnetic field) value at this point can be calculated through the antenna coefficient factor obtained from the previous calibration.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A positioning method for a near-field positioning system of a radiation disturbance source by a positioning system, characterized in that, The adopted positioning system is a near-field positioning system for radiated interference sources, including: an electric field probe, a magnetic field probe, a preamplifier, and a portable radiation analyzer. Among them, The electric field probe is made of a flexible coaxial cable. After stripping part of the shielding layer, an equivalent capacitance is formed between the bare conductor and the outer shielding layer to sense the change of the electric field and generate a corresponding induced current. The magnetic field probe is made of a flexible coaxial cable. The cable is bent into a ring structure, and at the same time, the shielding layer of the magnetic field cable is cut off at the top of the magnetic field probe. The preamplifier includes a low-input impedance amplifier and a high-input impedance amplifier. Among them, the high-impedance gain amplifier is used to expand the low-frequency characteristics of the electric field probe and is installed at the output end of the electric field probe. The low-impedance gain amplifier is used to expand the low-frequency characteristics of the magnetic field probe and is installed at the output end of the magnetic field probe. The portable radiation analyzer collects the output signals of the preamplifier, performs real-time FFT / DFT spectral analysis on the collected signals, combines the electromagnetic field probes to find the radiated interference source, and completes the positioning of the radiated interference source. The method includes the following steps: Calibration of the low-frequency near-field probe. The low-frequency near-field probe includes an electric field probe and a magnetic field probe to obtain the antenna coefficient factor AF of the low-frequency near-field probe from 500KHz to 30MHz. Select a large-size electric field probe to capture and determine the approximate area of the interference source, and then use a small-size electric field probe to determine the accurate position of the interference source and find the area with the maximum electric field radiation intensity of the equipment under test. Select a large-size magnetic field probe to capture and determine the approximate area of the interference source, and then use a small-size magnetic field probe to determine the accurate position of the interference source and find the area with the maximum magnetic field intensity of the equipment under test by using the magnetic field probe. Among them, the portable radiation analyzer obtains the frequency-domain relationship of the voltage signal at each point by performing discrete Fourier transform or fast discrete Fourier transform on the data measured by the electric field probe and the magnetic field probe. As the measurement range moves, a frequency-domain curve of the collected voltage signal is formed. According to the frequency-domain curve, the maximum point of the voltage signal in the frequency domain is found, and this point corresponds to the strongest electric field point or the strongest magnetic field point of the measured item.

2. The positioning method according to claim 1, wherein The antenna coefficient factor AF satisfies that within the target frequency range of 500KHz - 30MHz, as the test frequency increases, the obtained antenna coefficient factor basically shows a flat change, and AF remains basically unchanged. Where V is the voltage and E is the electromagnetic field strength.

3. The positioning method according to claim 1, wherein The portable radiation analyzer calculates the true electric field value or magnetic field value corresponding to the strongest electric field point or the strongest magnetic field point by using the calibrated antenna coefficient factor.

4. The positioning method according to claim 1, characterized in that, During detection, the electric field probe and the magnetic field probe are attached to the surface of the equipment under test for detection.

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