Rail train approach alarm device and method

Abstract

The invention discloses a rail train approach alarm device and method, and relates to the technical field of rail train detection. The device comprises ground end equipment and vehicle-mounted end equipment, the ground end equipment and the vehicle-mounted end equipment can measure the distance between a ground construction area and a traveling train in real time, and the distance measurement limit is not less than 3.5 km; and when the distance measured by the ground end equipment and the vehicle-mounted end equipment is smaller than or equal to the early warning distance, respective alarms are started to give an alarm, so that a train driver is reminded to control the train to slow down in time, and constructors on the road get off the road to avoid danger. According to the method, positioning beacons do not need to be additionally laid, a train operation monitoring system does not need to be matched, cost is reduced, meanwhile, train-ground distance measurement is achieved through radar secondary inquiry, and measurement inaccuracy caused by environmental interference is avoided.

Description

Technical Field

[0001] The present application relates to the technical field of rail train detection, and in particular to a rail train approach alarm device and method. Background Art

[0002] Railways need to be inspected regularly. When a section needs maintenance, the construction team has to stay at the current railway for a long time. However, when the train is operating normally, heavy-loaded trains will pass by at irregular intervals. This problem will not only affect the normal operation of the train, but also have a serious impact on the life safety of railway staff and train drivers.

[0003] In order to solve the above problems, there are existing technologies such as beacon positioning technology, train operation monitoring technology, map matching positioning technology, satellite positioning technology, etc. Although they can also ensure railway safety to a certain extent, they all have disadvantages that cannot be ignored. Among them, although the beacon positioning technology can accurately locate the current position of the train, it is necessary to lay a large number of positioning beacons in advance on the road section, which is not only expensive, but also increases the time that the staff stay in the maintenance area, which invisibly increases the safety hazards; the train operation monitoring technology requires a matching train operation monitoring system, which is also expensive, and is not applicable because the staff's residence area is highly random; map matching positioning technology needs to rely on high-precision maps; satellite positioning technology relies on satellite signals and is greatly affected by the environment. At the same time, the above technologies have a common disadvantage, that is, they can only provide warnings in one direction, and cannot enable train drivers and railway construction personnel to intuitively and clearly feel the danger information, so that train drivers can slow down in advance and construction personnel on the road can get off the road in advance to avoid danger. Summary of the invention

[0004] In order to solve the problems of high cost, poor applicability and only one-way warning in the existing technology, the present application proposes a rail train approach alarm device and method. In the present application, both the vehicle and the ground can measure the distance between the ground construction area and the moving train in real time. At the same time, when the distance reaches the warning distance, the alarm will be activated to promptly remind the train driver to control the train to slow down and the construction workers on the road to get off the road to avoid danger.

[0005] This application is implemented through the following technical solutions:

[0006] A rail train approach alarm device, the device comprising a ground terminal device and a vehicle terminal device;

[0007] The ground terminal equipment and the vehicle terminal equipment can both measure the distance between the ground construction area and the moving train in real time, and the distance measurement limit is not less than 3.5km;

[0008] When the measured distance is less than or equal to the warning distance, the ground-end equipment and the vehicle-mounted equipment will activate their respective alarms to promptly remind the train driver to control the train to slow down and the construction workers on the road to get off the road to avoid danger.

[0009] In some embodiments, the ground terminal device and the vehicle terminal device both include a positioning module, a communication module, a power module, a radio frequency module and a signal processing board;

[0010] Wherein, the power supply module supplies power to the signal processing board and other modules;

[0011] The communication module, the positioning module, the radio frequency module and the signal processing board are communicatively connected.

[0012] In some embodiments, the power module of the vehicle-mounted terminal device uses a 110V DC power input, and the power module performs DC-DC step-down conversion on the input power to output 12V DC, 5V DC, 3.3V DC and 1.8V DC to power the signal processing board and other modules of the vehicle-mounted terminal device;

[0013] The power module of the ground terminal device uses a 24V DC lithium battery input. The power module performs DC-DC step-down conversion on the input power supply and outputs 12V DC, 5V DC, 3.3V DC and 1.8V DC to power the signal processing board and other modules of the ground terminal device.

[0014] In some embodiments, the positioning module integrates a baseband and a radio frequency integrated chip;

[0015] The positioning module supports active antennas or passive antennas, and is used to receive satellite signals in the air and send them to the internal integrated RF chip. The signal received by the RF chip is amplified by an internal low-noise amplifier, mixed and sent to the intermediate frequency filter, and then converted into a digital intermediate frequency signal by an analog-to-digital converter and sent to the baseband chip. The baseband chip tracks and locates the digital intermediate frequency signal, outputs NMEA data and gives a 1PPS signal to the signal processing board.

[0016] In some implementations, the communication module has multiple communication interfaces and transmits the distance measurement results and warning information through a communication network.

[0017] In some embodiments, the radio frequency module of the vehicle-mounted device is used to transmit an inquiry signal to the ground-end device and receive a response signal returned by the ground-end device;

[0018] The radio frequency module of the ground terminal device is used to receive the inquiry signal transmitted by the vehicle-mounted terminal device and transmit a response signal to the vehicle-mounted terminal device, and also receive a response signal from the vehicle-mounted terminal device to the response signal.

[0019] In some embodiments, the signal processing board includes a power detection module, a signal processing module, a distance measurement module, and an alarm module;

[0020] The power detection module calculates the difference between the average power in a window and the preset power according to the real-time received signal and transmits the feedback gain coefficient to the RF module through the SPI bus, so that weak signals can be correctly detected below a fixed threshold, thereby ensuring that the device communication and ranging distance limit is above 3.5km;

[0021] The ranging module converts the distance information according to the time difference between the transmitted signal and the received signal, and controls the vehicle-mounted terminal device or the ground-mounted terminal device to return a response signal after receiving the signal in the same clock cycle without timing synchronization through the relationship between the address of the signal in the memory and the current processing address, thereby ensuring that the ranging error is within 60m;

[0022] The signal processing module is used to restore the information carried by the received signal, and after obtaining the correct information, report it together with the obtained distance information;

[0023] The alarm module compares the obtained distance information with the warning distance, and activates an alarm to sound an alarm if the distance information is less than or equal to the warning distance.

[0024] In some embodiments, the alarm is an audible and visual alarm.

[0025] In the second aspect, the present application also proposes a distance measurement method based on the above-mentioned rail train approach alarm device, wherein the distance measurement method includes distance measurement by a vehicle-mounted terminal device, and the specific process includes:

[0026] Actively initiate an inquiry signal and start counting;

[0027] When receiving the response signal returned by the ground terminal device, it is decoded, the corresponding signal is obtained for response and counting is stopped, and the vehicle-ground distance is calculated based on the starting count difference and the clock signal;

[0028] The obtained vehicle-to-ground distance and decoded information are reported.

[0029] In the third aspect, the present application also proposes a ranging method based on the above-mentioned rail train approach alarm device, wherein the ranging method includes ranging by ground-end equipment, and the specific process includes:

[0030] After receiving the inquiry signal initiated by the vehicle-mounted device and decoding it, it starts counting after obtaining the corresponding signal and returns the response signal at the preset time;

[0031] When receiving the response signal returned by the vehicle-mounted terminal device, decoding is performed, and counting is stopped after obtaining the corresponding signal;

[0032] The vehicle-ground distance is obtained by converting the starting count difference and the clock signal;

[0033] The decoded information and the obtained vehicle-ground distance are reported.

[0034] The present application proposes a rail train approach alarm device and method, which are based on satellite positioning technology, use the superior equipment to send the position information of both parties, and combine with the inquiry working mechanism of the secondary radar. Both the vehicle and the ground can measure the vehicle-ground distance in real time, and the distance measurement limit is not less than 3.5km, and some other useful information can be obtained; at the same time, both the vehicle-mounted device and the ground-end device can display the measured distance information and other useful information obtained; in addition, when the distance measured in real time reaches the warning distance, the alarm will be activated to alarm, and the train driver will be promptly reminded to control the train to slow down and the construction workers on the road to get off the road to avoid danger.

[0035] The present application proposes a rail train approach alarm device and method, which does not require additional positioning beacons or a matching train operation monitoring system, thereby reducing costs. At the same time, radar secondary inquiry is used to achieve vehicle-to-ground distance measurement, thereby avoiding inaccurate measurements caused by environmental interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The drawings described herein are used to provide a further understanding of the embodiments of the present application, constitute a part of the present application, and do not constitute a limitation on the embodiments of the present application. In the drawings:

[0037] Figure 1 A schematic diagram of the device architecture proposed in an embodiment of the present application;

[0038] Figure 2 A schematic diagram of the architecture of a ground terminal device or a vehicle-mounted terminal device proposed in an embodiment of the present application;

[0039] Figure 3 This is a schematic diagram of the signal processing board architecture proposed in the embodiment of the present application;

[0040] Figure 4 A schematic diagram of power control according to an embodiment of the present application;

[0041] Figure 5 A schematic diagram of multi-branch correlation peak calculation in an embodiment of the present application;

[0042] Figure 6 A schematic diagram of data entering the cache and cache address changes in an embodiment of the present application;

[0043] Figure 7This is a schematic diagram of the signal flow and ranging function implementation of the device according to an embodiment of the present application. DETAILED DESCRIPTION

[0044] Hereinafter, the term "include" or "may include" used in various embodiments of the present application indicates the presence of the invented function, operation or element, and does not limit the addition of one or more functions, operations or elements. In addition, as used in various embodiments of the present application, the terms "include", "have" and their cognates are intended only to indicate specific features, numbers, steps, operations, elements, components or a combination of the foregoing items, and should not be understood as first excluding the presence of one or more other features, numbers, steps, operations, elements, components or a combination of the foregoing items or the possibility of adding one or more features, numbers, steps, operations, elements, components or a combination of the foregoing items.

[0045] In various embodiments of the present application, the expression "or" or "at least one of A or / and B" includes any combination or all combinations of the words listed at the same time. For example, the expression "A or B" or "at least one of A or / and B" may include A, may include B, or may include both A and B.

[0046] The expressions (such as "first", "second", etc.) used in the various embodiments of the present application may modify the various constituent elements in the various embodiments, but may not limit the corresponding constituent elements. For example, the above expressions do not limit the order and / or importance of the elements. The above expressions are only used for the purpose of distinguishing one element from other elements. For example, the first user device and the second user device indicate different user devices, although both are user devices. For example, without departing from the scope of the various embodiments of the present application, the first element may be referred to as the second element, and similarly, the second element may also be referred to as the first element.

[0047] It should be noted that if it is described that one component element is “connected” to another component element, the first component element may be directly connected to the second component element, and a third component element may be “connected” between the first component element and the second component element. Conversely, when one component element is “directly connected” to another component element, it can be understood that there is no third component element between the first component element and the second component element.

[0048] The terms used in the various embodiments of the application are only used to describe the purpose of specific embodiments and are not intended to limit the various embodiments of the application. As used herein, the singular form is intended to also include the plural form, unless the context clearly indicates otherwise. Unless otherwise limited, all terms used here (including technical terms and scientific terms) have the same meaning as the meanings commonly understood by ordinary technicians in the field of the various embodiments of the application. The terms (such as the terms defined in the dictionary generally used) will be interpreted as having the same meaning as the contextual meaning in the relevant technical field and will not be interpreted as having an idealized meaning or an overly formal meaning, unless clearly defined in the various embodiments of the application.

[0049] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with examples and drawings. The illustrative implementation scheme of the present application and its description are only used to explain the present application and are not intended to limit the present application.

[0050] Example:

[0051] The existing technology has the problems of high cost, poor applicability, easy to be affected by the environment, and only one-way warning. In view of this, this embodiment proposes a rail train approach alarm device and method. This application is based on satellite positioning technology, uses the upper device to send the location information of both parties, and combines the inquiry working mechanism of the secondary radar. Both the vehicle and the ground can measure the distance between the ground construction area and the moving train in real time, and the distance measurement limit is not less than 3.5km. Some other useful information can also be obtained. For example, the vehicle-mounted equipment can obtain the kilometer mark of the current location of the ground equipment, and the ground equipment can obtain information such as the speed of the approaching vehicle. At the same time, both the vehicle-mounted equipment and the ground equipment can display the distance information and the obtained useful information on the screen. If the warning distance (for example, 3km) is reached, the alarm will be activated (the sound and light alarm can be used) to promptly remind the train driver to control the train to slow down and the construction personnel on the road to avoid danger.

[0052] like Figure 1-Figure 2 As shown, the device proposed in this embodiment includes:

[0053] Vehicle-mounted equipment and ground-end equipment;

[0054] Both the vehicle-mounted equipment and the ground-end equipment include a positioning module, a communication module, a power module, a radio frequency module and a signal processing board. The power module supplies power to the signal processing board and other modules. The positioning module, communication module and radio frequency module are all communicatively connected to the signal processing board.

[0055] Among them, the power module of the vehicle-mounted equipment uses a 110V DC power input, and the power module performs DC-DC step-down conversion on the input power, and outputs 12V DC, 5V DC, 3.3V DC, 1.8V DC and other voltages to supply the signal processing board and other modules. The power module of the ground-end equipment uses a 24V DC lithium battery input, and the power module performs DC-DC step-down conversion on the input power, and outputs 12V DC, 5V DC, 3.3V DC, 1.8V DC and other voltages to supply the signal processing board and other modules.

[0056] The positioning module provides GNSS positioning data, supports BDS B1 / GPS L1 dual-mode, and integrates baseband + RF integrated chip internally, with high sensitivity, low power consumption and low cost. The positioning module supports active or passive antennas. The antenna receives satellite signals in the air and sends them to the RF chip. The signals received by the RF chip are amplified and mixed by the internal LNA (low noise amplifier) ​​and sent to the intermediate frequency filter. They are then converted into digital intermediate frequency signals through AD and sent to the baseband chip. The baseband chip receives the digital intermediate frequency signals sent by the RF chip, and after capture, tracking, positioning and solving, etc., it outputs NMEA data through the serial port and gives 1PPS signals to the signal processing board.

[0057] The communication module can adopt 4G communication network and can have multiple communication interfaces, supporting network card mode, routing mode, serial port AT control, data transparent transmission and other functions, and transmitting ranging results and warning information through the communication network.

[0058] like Figure 3 As shown, the signal processing board mainly uses FPGA chips for data modulation and demodulation. The signal processing board mainly includes a power detection module, a signal processing module, a ranging module and an alarm module. Among them, the power detection module calculates the difference between the average power in a window and the preset power according to the real-time received signal, and transmits the feedback gain coefficient to the RF module through the SPI bus, so that weak signals can also be correctly detected below a fixed threshold. The processing of the power detection module ensures that the equipment communication and ranging distance are above 3.5km. Specifically, the power detection module can set the window length to 1024, and feedback a gain control coefficient (gain value) to the 0x109 address of AD9361 through the SPI bus every 1250 clock cycles. The gain control coefficient ranges from 0 to 76. The average amplitude (db) in the window is calculated as follows: AD9361 outputs two data channels i and q, and calculates After accumulating 1024 results, take the average value and convert the value into db. Figure 4For example, if the gain coefficient in the current address 0x109 is 12, and the average amplitude (db) in the window is calculated to be 34, then there is still a shortfall of 24db from the preset value of 58db, so the gain control coefficient to be fed back is 12+24=36.

[0059] The ranging module not only converts the distance information based on the time difference between the transmitted signal and the received signal, but also controls the vehicle-mounted device or the ground-mounted device to return the response signal after the same clock cycle after receiving the signal through the relationship between the address of the signal in the memory and the current processing address without timing synchronization. This module is the key module to ensure that the system ranging error is within 60m.

[0060] The signal processing module is used to restore the information carried by the received signal, and use the improved RIFE transform to analyze the spectrum of the signal, so that the estimated frequency deviation error can be less than 30Hz under the low-resolution (2k) spectrum. After compensating the frequency deviation, the error caused by the residual frequency deviation is corrected according to the quadratic linear interpolation algorithm and signal interleaving theory (information analysis + frequency deviation unit). After obtaining the correct information, it is reported together with the obtained distance information (data reporting unit). In addition, the correlator peak search unit: the correlator adopts a multi-branch parallel processing method, which has a fast processing speed and greatly reduces the pressure on the data cache. There are 80 related branches in the correlator, that is, it can search for 80 phase points at the same time. The cycle required to search a ram is 1280 / 80=16, and each phase point needs to accumulate 1250 clocks to obtain the correlation peak. The input of the cache ram is 10M, and the output in this unit is 200M. According to the calculation, the time required to write a full section is 1280 / 10M=0.128ms, and the time to process a section of data is (1250+80)*16 / 200M=0.1064ms, which is less than the time required to write a full section, so no data will be lost. Figure 5 As shown. Starting from the first correlation peak output, a counter is used to count, and the counting range is 1 to 3840, corresponding to the position in the cache Ram where the signal starting point is located. The address is the counter minus 1. There will be 80 correlation peaks output continuously in one cycle. It is necessary to first find the maximum value of the 80 continuously output correlation peaks, and then use the maximum value to compare with the threshold. If it is greater than the threshold, it is determined that the signal starting position is found, and the enable and signal position information of the analysis unit are output. If it is less than the threshold, it is determined that the signal is not found. When the signal is found, the correlator peak finding unit will give the address in the cache ram corresponding to the starting position of the signal to the downsampling cache ram.

[0061] 10M downsampling cache RAM unit: It is not only used to cache data, but also a key module for controlling processing time. Due to the randomness of the signal entry time, it is difficult to ensure that the time from signal entry to completion of processing is consistent every time. The general processing method is to perform timing synchronization, that is, to use the timestamp given by the satellite to generate a second pulse and continuously correct it, and use the second pulse to record the processing time. This method is too complicated and depends on the satellite communication module. This unit uses a simpler and more direct method to solve the above problems in disguise. Because the signal will be cached in the RAM after entering, and the correlator will find this position before the signal is overwritten, and the cache depth is certain, the data entry speed is continuous and certain, so after obtaining the signal position, wait until the cache RAM address is in the first 6 addresses of the signal address, and start processing the signal. In this way, the data will not be overwritten, and the consistency of the data processing time is guaranteed. Such as Figure 6 As shown, if the signal starting position is now stored in address 6 corresponding to ①, and the correlator finds the signal starting position corresponding to ② when the address is written to x, then when the address jumps to 0, the enable signal of the subsequent unit is generated, corresponding to ③ and ④.

[0062] The alarm module compares the distance information obtained by the distance measuring module with the warning distance. If the distance information obtained is less than or equal to the warning distance, the sound and light alarm is activated to sound an alarm.

[0063] The RF module of the vehicle-mounted device is used to transmit an inquiry signal to the ground-end device and receive a response signal returned by the ground-end device;

[0064] The radio frequency module of the ground terminal device is used to receive the inquiry signal transmitted by the vehicle terminal device and transmit a response signal to the vehicle terminal device, and also receive a response signal from the vehicle terminal device to the response signal.

[0065] Optionally, the ground-end device and the vehicle-mounted device also include a display module for displaying distance information and other useful information obtained.

[0066] The device proposed in this embodiment can enable both the ground-end equipment and the vehicle-mounted equipment to measure the distance between the ground construction area and the moving train in real time, and the distance limit is not less than 3.5km. At the same time, it can also alarm when the warning distance is reached, and promptly remind the train driver to control the train to slow down and the construction workers on the road to get off the road to avoid danger.

[0067] The distance measurement is performed based on the above device proposed in this embodiment. The specific distance measurement process is as follows: Figure 7 shown.

[0068] For the vehicle-mounted device, the ranging process includes:

[0069] Actively initiate an inquiry signal and start counting. When receiving the response signal returned by the ground device, decode it, respond and stop counting after obtaining the corresponding signal. The vehicle-ground distance is calculated based on the starting count difference and the clock signal. The process takes no more than 150ms to complete, and the ranging error is within 60m. At the same time, the decoded information and the vehicle-ground distance information are reported.

[0070] For ground-side equipment, the ranging process includes:

[0071] After receiving the inquiry signal initiated by the vehicle-mounted terminal device and decoding it, it starts counting after obtaining the corresponding signal, and returns the response signal at the preset time. When receiving the response signal returned by the vehicle-mounted terminal device, it decodes it and stops counting after obtaining the corresponding signal. The vehicle-ground distance is converted according to the starting count difference and the clock signal. The completion time of this process does not exceed 150ms, and the ranging error is within 60m. At the same time, the decoded information and the obtained vehicle-ground distance information are also reported.

[0072] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0073] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0074] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1A function specified in one or more boxes.

[0075] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0076] The specific implementation methods described above further illustrate the purpose, technical solutions and beneficial effects of the present application in detail. It should be understood that the above description is only the specific implementation method of the present application and is not intended to limit the scope of protection of the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A rail train approach alarm device, characterized in that: The device comprises a ground terminal device and a vehicle terminal device; The ground terminal equipment and the vehicle terminal equipment can both measure the distance between the ground construction area and the moving train in real time, and the distance measurement limit is not less than 3.5km; When the measured distance is less than or equal to the warning distance, the ground-end equipment and the vehicle-mounted equipment will activate their respective alarms to promptly remind the train driver to control the train to slow down and the construction workers on the road to get off the road to avoid danger.

2. A rail train approach alarm device according to claim 1, characterized in that: The ground terminal device and the vehicle terminal device both include a positioning module, a communication module, a power module, a radio frequency module and a signal processing board; Wherein, the power supply module supplies power to the signal processing board and other modules; The communication module, the positioning module, the radio frequency module and the signal processing board are communicatively connected.

3. A rail train approach alarm device according to claim 2, characterized in that: The power module of the vehicle-mounted terminal device uses a 110V DC power input, and the power module performs DC-DC step-down conversion on the input power to output 12VDC, 5V DC, 3.3V DC and 1.8V DC to power the signal processing board and other modules of the vehicle-mounted terminal device; The power module of the ground terminal device uses a 24V DC lithium battery input. The power module performs DC-DC step-down conversion on the input power supply and outputs 12V DC, 5V DC, 3.3V DC and 1.8V DC to power the signal processing board and other modules of the ground terminal device.

4. A rail train approach alarm device according to claim 2, characterized in that: The positioning module integrates a baseband and radio frequency integrated chip; The positioning module supports active antennas or passive antennas, and is used to receive satellite signals in the air and send them to the internal integrated RF chip. The signal received by the RF chip is amplified by an internal low-noise amplifier, mixed and sent to the intermediate frequency filter, and then converted into a digital intermediate frequency signal by an analog-to-digital converter and sent to the baseband chip. The baseband chip tracks and locates the digital intermediate frequency signal, outputs NMEA data and gives a 1PPS signal to the signal processing board.

5. A rail train approach alarm device according to claim 2, characterized in that: The communication module has multiple communication interfaces and transmits distance measurement results and warning information through a communication network.

6. A rail train approach alarm device according to claim 2, characterized in that: The radio frequency module of the vehicle-mounted terminal device is used to transmit an inquiry signal to the ground-end device and receive a response signal returned by the ground-end device; The radio frequency module of the ground terminal device is used to receive the inquiry signal transmitted by the vehicle-mounted terminal device and transmit a response signal to the vehicle-mounted terminal device, and also receive a response signal from the vehicle-mounted terminal device to the response signal.

7. A rail train approach alarm device according to any one of claims 2 to 6, characterized in that: The signal processing board includes a power detection module, a signal processing module, a distance measurement module and an alarm module; The power detection module calculates the difference between the average power in a window and the preset power according to the real-time received signal and transmits the feedback gain coefficient to the RF module through the SPI bus, so that weak signals can be correctly detected below a fixed threshold, thereby ensuring that the device communication and ranging distance limit is above 3.5km; The ranging module converts the distance information according to the time difference between the transmitted signal and the received signal, and controls the vehicle-mounted terminal device or the ground-mounted terminal device to return a response signal after receiving the signal in the same clock cycle without timing synchronization through the relationship between the address of the signal in the memory and the current processing address, thereby ensuring that the ranging error is within 60m; The signal processing module is used to restore the information carried by the received signal, and after obtaining the correct information, report it together with the obtained distance information; The alarm module compares the obtained distance information with the warning distance, and activates an alarm to sound an alarm if the distance information is less than or equal to the warning distance.

8. A rail train approach alarm device according to claim 7, characterized in that: The alarm device adopts an audible and visual alarm device.

9. A distance measurement method for a railway train approaching alarm device according to any one of claims 1 to 8, characterized in that: The distance measurement method includes distance measurement by a vehicle-mounted device, and the specific process includes: Actively initiate an inquiry signal and start counting; When receiving the response signal returned by the ground terminal device, it is decoded, the corresponding signal is obtained for response and counting is stopped, and the vehicle-ground distance is calculated based on the starting count difference and the clock signal; The obtained vehicle-to-ground distance and decoded information are reported.

10. A distance measurement method for a railway train approaching alarm device according to any one of claims 1 to 8, characterized in that: The distance measurement method includes distance measurement by ground-end equipment, and the specific process includes: After receiving the inquiry signal initiated by the vehicle-mounted device and decoding it, it starts counting after obtaining the corresponding signal and returns the response signal at the preset time; When receiving the response signal returned by the vehicle-mounted terminal device, decoding is performed, and counting is stopped after obtaining the corresponding signal; The vehicle-ground distance is obtained by converting the starting count difference and the clock signal; The decoded information and the obtained vehicle-ground distance are reported.

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