Urban rail transit vehicle-mounted antenna gain test method and test system

Abstract

The invention relates to an urban rail transit vehicle-mounted antenna gain test method and test system, and the method comprises the steps: arranging test equipment at a set test point, transmitting a radio frequency signal generated by a signal generator to a vehicle-mounted antenna installed at a train through a radio frequency jumper wire, and transmitting the radio frequency signal to the test equipment; after being received by a test antenna arranged at a test point position, the signal is transmitted to a spectrum analyzer through a radio frequency feeder line to record the received power, and parameters required for calculating the gain of the vehicle-mounted antenna are obtained; and comparing the calculated value of the gain of the vehicle-mounted antenna with the theoretical value, and determining whether the installation of the vehicle-mounted antenna meets the requirements or not. The test method is simple and high in operability, and a test result can directly feed back whether antenna installation meets performance requirements or not so as to ensure that a good communication effect can be obtained between a train and a radio system beside a track after the antenna is installed.

Description

Technical Field

[0001] The present invention relates to the field of rail transit, and in particular to a method and a system for testing the gain of an onboard antenna of an urban rail transit vehicle. Background Art

[0002] The on-board antenna and the trackside antenna based on free wireless transmission form a continuous wireless communication system, providing a reliable data communication connection between the on-board signal equipment and the trackside signal equipment. During the vehicle interface negotiation, each professional will put forward installation requirements, such as radiation angle, metal-free area, cable bending radius, antenna installation direction, spacing between other wireless systems, antenna installation position for easy maintenance, etc. After the first train is installed, an installation inspection is carried out. Due to the limited space on the vehicle, the theoretical installation requirements may not be fully met. In addition, the feeder bending radius requirements and the metal-free area around the antenna are not easily visible to the naked eye, so a measurement method is needed to check the antenna installation quality to confirm that the actual installation position of the antenna meets the functional requirements of the signal system.

[0003] Currently, there is a lack of actual gain testing after the vehicle-mounted flat panel antenna is installed, which may lead to the following problems:

[0004] 1. The metal-free area required by the antenna is difficult to inspect with the naked eye. For example, the body parts and some insulation layers of the body contain tin foil, which will cause loss of wireless signals but is difficult to detect.

[0005] 2. Antenna installation requires that there are no other antennas within a 1-meter range, but the actual vehicle space is limited and it is difficult to fully meet this requirement. When not all conditions fully meet the installation requirements of antenna products, a feasible method is needed to determine whether the installation can meet business needs.

[0006] 3. If you wait until the end of the project when the wireless quality is poor to conduct an in-depth inspection of the antenna installation problem, it may involve multiple professional rectifications of the vehicle, which is time-consuming and laborious. Therefore, an effective detection method that can be implemented during the early installation is needed.

[0007] 4. Differences in the installation of vehicle-mounted antennas for different projects will lead to differences in the receiving field strength. After interconnection, there will be a high probability of communication interruption when trains on Line 1 are running on Line 2. At this time, the installation and adjustment of the vehicle-mounted antennas will require a lot of work. Summary of the invention

[0008] The purpose of the present invention is to overcome the defects of the prior art and provide a method and system for testing the gain of an on-board antenna for urban rail transit, so as to determine whether the installation of the on-board antenna of the train meets the performance requirements and ensure that good communication effect can be obtained between the train and the trackside radio system after the antenna is installed.

[0009] In order to achieve the above object, the present invention provides a vehicle-mounted antenna gain test method. When the vehicle-mounted antenna gain test is performed at a set test point, the radio frequency signal generated by the signal generator is transmitted to the vehicle-mounted antenna installed at the train via a radio frequency jumper to be emitted outward, and is received by the test antenna set at the test point and transmitted to the spectrum analyzer via a radio frequency feeder to record the received power.

[0010] Calculate the calculated value G of the vehicle antenna gain according to the first formula Train :

[0011] G Train =P r -P t -L Feeder -G Trackside -L FS

[0012] P t is the actual transmission power of the signal generator; the actual transmission power of the signal generator is obtained by subtracting the cable loss of the RF jumper from the transmission power set by the signal generator;

[0013] P r The received power recorded by the spectrum analyzer;

[0014] L Feeder is the feeder loss;

[0015] G Trackside To test the front lobe gain of the antenna;

[0016] L FS is the free space loss;

[0017] The calculated value of the vehicle-mounted antenna gain is compared with the theoretical value of the vehicle-mounted antenna gain, and whether the vehicle-mounted antenna installation meets the requirements is determined according to the comparison result.

[0018] Optionally, when comparing the calculated value of the vehicle-mounted antenna gain with the theoretical value of the vehicle-mounted antenna gain, further calculating a difference between the calculated value and the theoretical value, and determining whether the difference is within a threshold range;

[0019] If the difference is within the threshold range, it is determined that the vehicle-mounted antenna installation meets the requirements;

[0020] If the difference is not within the threshold range, it is determined that the vehicle-mounted antenna installation does not meet the requirements.

[0021] Optionally, when the difference between the test value and the theoretical value of the vehicle-mounted antenna gain does not exceed ±1 dB, it is considered that the vehicle-mounted antenna installation meets the requirements.

[0022] Optionally, the free space loss L is calculated according to the second formula:FS :

[0023]

[0024] Where λ is the wavelength and d is the distance between the vehicle antenna and the test antenna.

[0025] Optionally, before performing a gain test on a vehicle-mounted antenna, perform the following checks:

[0026] Checking the installation position of the vehicle-mounted antenna; after the installation position check is completed, the train is powered on and all wireless systems on the train are turned on; and,

[0027] Perform standing wave measurement to check whether the standing wave ratio of the vehicle-mounted antenna is normal.

[0028] Optionally, the vehicle-mounted antenna is a flat-panel antenna;

[0029] The test points include a position located directly in front of the vehicle antenna and at a set distance from the vehicle antenna, and a position located 30 degrees in front of the vehicle antenna and at a set distance from the vehicle antenna;

[0030] Performing a gain test on each operating frequency point selected by the flat antenna at each test point;

[0031] The test antenna is a trackside antenna arranged at a test point, and the height of the test antenna is the same as that of the vehicle-mounted antenna.

[0032] Optionally, the flat panel antenna includes a left antenna and a right antenna; before performing a gain test on the vehicle-mounted antenna, the installation position of the flat panel antenna is also checked to determine that the left antenna and the right antenna are respectively installed on both sides above the driving cab inside the train.

[0033] Optionally, checking the installation position of the flat panel antenna further includes confirming whether the following requirements are met:

[0034] The flat panel antenna is installed vertically, with its front side facing the front of the train head, so that the polarization direction of the flat panel antenna is consistent with that of the trackside antenna;

[0035] The flat panel antenna is fixed on a bracket having a conductive surface;

[0036] The flat antenna and its bracket are considered as a whole, and a clearance of at least 5 to 10 cm is required around them;

[0037] There is no metal area within 30 degrees in front of the flat antenna.

[0038] Optionally, the test points corresponding to the right antenna include:

[0039] A first position directly in front of the right antenna, with a distance of 3L from the right antenna;

[0040] A second position on the right side of the first position and spaced apart from the first position by a distance L;

[0041] Among them, L is the set unit distance;

[0042] The second position corresponds to 30 degrees to the right front of the right antenna; when performing a gain test at the second position, the orientation of the right antenna is adjusted to be directly opposite the test antenna at the second position, and the result of the gain test at the second position is used to analyze the metal condition within 30 degrees of the right antenna.

[0043] Optionally, the test points corresponding to the left antenna include:

[0044] A third position directly in front of the left antenna and with a distance of 3L from the left antenna;

[0045] A fourth position on the left side of the third position and spaced apart from the third position by a distance L;

[0046] The fourth position corresponds to 30 degrees to the left front of the left antenna; when performing a gain test at the fourth position, the orientation of the left antenna is adjusted to be directly opposite the test antenna at the fourth position, and the gain test result at the fourth position is used to further analyze the metal situation within 30 degrees of the left antenna.

[0047] Optionally, the test point corresponding to the right antenna further includes:

[0048] A fifth position directly in front of the right antenna and spaced L from the right antenna;

[0049] The sixth position is directly in front of the right antenna and is 2L away from the right antenna.

[0050] Optionally, the test point corresponding to the left antenna further includes:

[0051] The seventh position is directly in front of the left antenna and is spaced L from the left antenna;

[0052] The eighth position is directly in front of the left antenna and is 2L away from the left antenna.

[0053] Optionally, the vehicle-mounted antenna is a roof shark fin antenna or a vehicle body outer side antenna; the measurement point is a position where a trackside leaky cable or a trackside antenna installation point is directly opposite to the vehicle-mounted antenna; and the test antenna height is the antenna height within the actual limit.

[0054] Optionally, the vehicle-mounted antenna gain test method is applicable to urban rail transit vehicle-mounted antennas and is implemented when a vehicle factory performs installation inspection on the first train.

[0055] Another technical solution of the present invention is to provide a vehicle-mounted antenna gain test system, which is used for any one of the above-mentioned vehicle-mounted antenna gain test methods, and the vehicle-mounted antenna gain test system comprises:

[0056] A signal generator, used for generating a radio frequency signal;

[0057] A radio frequency jumper, connecting the signal generator to the vehicle-mounted antenna, and used to transmit the radio frequency signal to the vehicle-mounted antenna;

[0058] A test antenna, located at a set test point, for receiving the radio frequency signal emitted by the vehicle-mounted antenna;

[0059] A radio frequency feeder, connecting the test antenna to a spectrum analyzer and used to transmit the radio frequency signal to the spectrum analyzer;

[0060] The spectrum analyzer is used to record the received power;

[0061] A processor, configured to receive the input parameters and calculate the calculated value G of the vehicle-mounted antenna gain according to the first formula Train :

[0062] G Train =P r -P t -L Feeder -G Trackside -L FS

[0063] The parameters include:

[0064] The spectrum analyzer records the received power P r ;

[0065] Feeder loss L Feeder ;

[0066] Test the front lobe gain G of the antenna Trackside ;

[0067] Free space loss L FS ;

[0068] The processor is used to subtract the cable loss of the RF jumper from the transmission power set by the signal generator to obtain the actual transmission power P of the signal generator. t ;

[0069] The processor is also used to receive a theoretical value of the vehicle-mounted antenna gain, and compare the calculated value of the vehicle-mounted antenna gain with the theoretical value, and determine whether the vehicle-mounted antenna installation meets the requirements according to the comparison result.

[0070] Optionally, the test antenna is installed via an antenna pole, and the test antenna is set to the same height as the vehicle-mounted antenna.

[0071] Optionally, the processor is further used to calculate a difference between a calculated value and a theoretical value of the vehicle-mounted antenna gain, and determine whether the difference is within a threshold range;

[0072] If the difference is within the threshold range, it is determined that the vehicle-mounted antenna installation meets the requirements;

[0073] If the difference is not within the threshold range, it is determined that the vehicle-mounted antenna installation does not meet the requirements.

[0074] Optionally, the processor is further configured to receive the wavelength λ, the distance d between the vehicle-mounted antenna and the test antenna, and calculate the free space loss L according to the second formula: FS :

[0075]

[0076] The processor then converts the obtained free space loss L FS A calculated value used to calculate the gain of the vehicle-mounted antenna.

[0077] The vehicle-mounted antenna gain testing method of the present invention has at least the following beneficial effects:

[0078] The present invention provides an effective installation inspection method for a vehicle-mounted antenna, which can preliminarily grasp the wireless environment in which the antenna is installed, ensure good communication between the train and the trackside radio system, and eliminate problems with the installation position or environment that may affect the transmission performance of the antenna.

[0079] The present invention can be implemented on-site during the installation inspection of the first train, so that it can be known in advance whether the installation of the vehicle-mounted antenna meets the performance requirements, thereby avoiding the problem of a huge workload for rectification after the subsequent vehicle installation.

[0080] The testing method of the present invention is simple and highly operable, provides clear inspection steps, and can avoid omissions in inspections of various installation requirements.

[0081] For situations that do not meet antenna installation requirements, such as multiple RF systems being closely spaced, or the vehicle-mounted antenna installation distance not meeting 1.2 meters, the test method of the present invention can also be used to determine a feasible antenna installation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Figure 1 It is a flow chart of the vehicle-mounted antenna gain testing method of the present invention.

[0083] Figure 2 It is a schematic diagram of the test points of the vehicle-mounted antenna gain test method described in the present invention.

[0084] Figure 3 It is a schematic diagram of the layout of the test equipment of the vehicle-mounted antenna gain test method of the present invention. DETAILED DESCRIPTION

[0085] The present invention provides a method and system for testing the gain of an on-board antenna for urban rail transit, which can be directly implemented on site during the antenna installation phase. After the antenna is installed on the first train, a simulated transmission signal is used to test the antenna gain to ensure that the train antenna is well installed, and that good communication is ensured between the train and the trackside radio system, and that there are no problems with the installation position or environment that may affect the transmission performance of the antenna.

[0086] like Figure 1 As shown, the vehicle-mounted antenna gain testing method of the present invention comprises the following steps:

[0087] S1. Check the installation status of the vehicle antenna;

[0088] S2. Perform standing wave measurement to check the standing wave ratio of the vehicle-mounted antenna;

[0089] S3. Test at various test points to obtain various parameters required for calculating antenna gain;

[0090] S4. Calculate antenna gain;

[0091] S5. Compare the calculated value of the antenna gain with the theoretical value, and determine whether the vehicle-mounted antenna installation meets the requirements based on whether the difference between the two is within a threshold range.

[0092] In step S1, the installation status needs to be checked before the test begins to ensure that the vehicle-mounted antenna is installed in the optimal position. Taking the flat-panel antenna as an example, the flat-panel antenna needs to be installed above the driver, inside the train and on both sides of the train; the flat-panel antenna should be fixed vertically on a bracket with a conductive surface; the flat-panel antenna and the antenna bracket are considered as a whole, and a gap of at least 5 to 10 cm must be maintained around them; there must be no metal area within 30° in front of the flat-panel antenna. After completing the inspection of the above installation position of the flat-panel antenna, the train needs to be powered on and all wireless systems on the train need to be turned on.

[0093] In step S2, in order to ensure that the vehicle-mounted antenna is not interfered by the close-range environment, a standing wave measurement is required to confirm that the standing wave ratio of the antenna is normal. For example, the standing wave ratio of a common flat-panel antenna in the 2.4 GHz frequency band must be less than 1.5.

[0094] Before executing step S3, relevant test equipment is arranged in the test environment. Figure 2 , Figure 3As shown, the test environment includes an area 3L long and 2L wide in front of the train head (L is a set unit distance); for example, when the first train is installed and inspected at a vehicle factory, a relevant area is designated in the vehicle factory for testing. Multiple test points are set up in the area, including a position located directly in front of the vehicle antenna, at distances of L, 2L, and 3L from the vehicle antenna, respectively, and a position located to the side of the front of the vehicle antenna (such as a position at a distance of 3L in front and at a distance of L to the left or right).

[0095] In this example, the vehicle-mounted antennas are the left antenna and the right antenna on both sides above the cab in the train; the unit distance L is 10 meters; an area 30 meters long and 20 meters wide is set in front of the train head 10, and 8 test points are set, including: the positions 10 meters, 20 meters, and 30 meters in front of the right antenna ( Figure 2 The positions 10m, 20m, and 30m on the y-axis shown in the figure are set as test points P1, P2, and P3, and the positions 10m, 20m, and 30m in front of the left antenna (10m, 20m, and 30m on the y-axis) are set as test points P4, P5, and P6. The position 10m to the left of point P6 (-10m on the x-axis) is set as test point P7, which is used to test the metal condition within a 30-degree range of the left antenna. The position 10m to the right of point P3 (+10m on the x-axis) is set as test point P8, which is used to test the metal condition within a 30-degree range of the right antenna.

[0096] The present invention provides a vehicle-mounted antenna gain test system, which includes the following test equipment: a spectrum analyzer 60, a signal generator 40, a test antenna 30, a radio frequency jumper 50, and a radio frequency feeder 70. Set the actual wireless working frequency band to perform standing wave ratio and antenna gain tests. The signal generator 40 is connected to the vehicle-mounted antenna 20 by the radio frequency jumper 50, and the spectrum analyzer 60 is connected to the test antenna 30 by the radio frequency feeder 70. The test antenna 30 is set to the same height as the vehicle-mounted antenna 30 (such as 1 / 4"). Figure 3 The height H1 of the vehicle-mounted antenna 30 and the height H2 of the test antenna 30 are both 4.2 meters).

[0097] The test antenna 30 in this example is a trackside antenna for testing. During the test, the test antenna 30 and the spectrum analyzer 60 connected to it through the RF feeder 70 are moved to various test points to perform antenna gain testing.

[0098] In step S3, when the antenna gain test is performed at each test point, the signal generated by the signal generator 40 is transmitted to the vehicle-mounted antenna 20 via the RF jumper 50 to be emitted outward, received by the test antenna 30 at the test point, and transmitted to the spectrum analyzer 60 via the RF feeder 70, and the received power is recorded by the spectrum analyzer 60.

[0099] In step S4, the antenna gain is calculated according to the following formula:

[0100] G Train =P r -P t -L Feeder -G Trackside -L FS

[0101] P t is the actual transmission power of the signal generator (determined by subtracting the loss of the RF jumper from the transmission power value adjusted by the signal generator during measurement);

[0102] P r It is the received power of the spectrum analyzer, which is recorded during the actual test;

[0103] L Feeder is the feeder loss, measured;

[0104] G Trackside is the front lobe gain of the trackside antenna, which is the product parameter of the trackside antenna used for testing;

[0105] L FS is the free space loss, calculated according to the following formula:

[0106]

[0107] Where λ is the wavelength (in meters) and d is the distance between the vehicle antenna and the test antenna (in meters).

[0108] G Train The gain of the train's onboard antenna is a measured value calculated based on the aforementioned parameters. It will be compared with the theoretical gain of the onboard antenna to determine its rationality.

[0109] In step S5, the calculated value of the gain of the train onboard antenna (i.e., G Train ) and compare it with the theoretical value of the antenna product gain parameter to determine whether the vehicle-mounted antenna is installed reasonably.

[0110] Among them, since it is not a perfect free field, for example, because the test is carried out in a vehicle factory, the train is very close, or there is an unknown WIFI environment, etc., the accuracy may be affected. Therefore, in this example, it is assumed that the accuracy of the numerical measurement directly in front is ±1dB, that is, the error in the facing direction is ±1dB.

[0111] Therefore, in step S5, if the difference between the test value and the theoretical value of the vehicle antenna gain is within ±1dB, it is considered that the vehicle antenna installation meets the requirements; otherwise, it is considered that the vehicle antenna installation does not meet the requirements, and a detailed inspection is required for the reasons that may affect the antenna gain.

[0112] The vehicle-mounted antenna gain test system of the present invention is also provided with a processor for receiving the relevant parameters in step S4 and calculating the free space loss L FS and the gain of the train antenna G Train The processor also calculates the gain G of the train's onboard antenna Train Compare with the theoretical value, calculate the difference between the two, and determine whether the difference is within the threshold range (±1dB), so as to determine whether the vehicle antenna installation meets the requirements.

[0113] The following is a specific embodiment of performing gain testing on a flat panel antenna according to the above method of the present invention.

[0114] In step S1, the installation position of the flat panel antenna is checked to confirm whether it meets the following requirements:

[0115] S1.1 The flat panel antenna is installed vertically with the front facing the front of the train, ensuring that the polarization direction of the flat panel antenna is consistent with that of the trackside antenna;

[0116] S1.2 The flat antenna is fixed on a bracket with a conductive surface. The bracket uses a mechanical bracket and should have good electrical contact to achieve the purpose of grounding;

[0117] The S1.3 flat panel antenna is installed on both sides above the cab. There is no metal shielding within 30° in the four directions of up, down, left, and right in front of the flat panel antenna to prevent metal materials from affecting the wireless signal.

[0118] S1.4 Treat the flat panel antenna and its bracket as a whole, and keep at least 5 to 10 cm of clearance around them for easy maintenance;

[0119] S1.5 The surface of the flat antenna must be kept clean;

[0120] S1.6 Actually observe whether there are other wireless systems within 1 meter.

[0121] It should be noted that S1.1 to S1.6 do not limit the order of inspection of the antenna installation position, and the specific inspection items and order can be adjusted according to actual conditions.

[0122] In step S2, in order to ensure that the flat panel antenna is not interfered by the close environment, it is necessary to perform standing wave measurement; for example, when the standing wave ratio of the flat panel antenna in the 2.4 GHz frequency band is measured to be less than 1.5, the standing wave ratio of the antenna is considered normal, and the subsequent detection steps can be continued. Table 1 is an example of standing wave measurement results.

[0123]

[0124] Table 1

[0125] In step S3, Figure 2 The eight test points are P1 to P8, according to Figure 3 The test equipment is arranged in a way to conduct gain test; among them, P1~P3 points are at different distances in front of the right antenna, P4~P6 points are at different distances in front of the left antenna, and each flat antenna faces the front of the vehicle; P7 and P8 points are set to measure the metal situation within 30 degrees of the antenna, and the direction of the on-board flat antenna needs to be appropriately adjusted to make it face the test antenna on the trackside. Table 2 shows the measurement points corresponding to each antenna.

[0126] Right antenna, gain test P1,P2,P3,P8 Left antenna, gain test P4,P5,P6,P7

[0127] Table 2

[0128] It should be noted that, according to actual conditions, gain testing can be performed on each of the eight points; or a portion of the eight points can be selected for testing (for example, only testing on P3, P6, P7, and P8 points, and optional testing on other points).

[0129] All working frequencies selected by the flat panel antenna need to be tested. For example, if 2417MHz and 2472MHz are selected for 2.4GHz, measurements need to be performed in both the 2417MHz and 2472MHz frequency bands.

[0130] In this example, the front lobe gain G of the test antenna beside the test track is Trackside (dBi) is 14dBi.

[0131] First, measure the cable loss of the RF jumper and RF feeder, and calculate the actual transmission power of the signal generator, as shown in Table 3:

[0132]

[0133] Table 3

[0134] Among them, the cable loss of RF jumpers and RF feeders will vary according to the test material parameters of the cables selected during the test of each project. The corresponding cable loss can be measured by a spectrum analyzer.

[0135] Table 4 and Table 5 are statistical examples of the gain test results of the right antenna and the left antenna at various points.

[0136] Right Antenna:

[0137]

[0138] Table 4

[0139] Left Antenna:

[0140]

[0141] Table 5

[0142] The test goal is to ensure that the gains of the left and right antennas are around the theoretical values ​​(for example, the gain of the selected vehicle-mounted flat panel antenna is 8dBi).

[0143] Under this accuracy, the gain of the flat panel antenna directly in front is 8dBi±1dB. The vehicle antenna gain G calculated for the left and right antennas in Tables 4 and 5 is Train If the test results do not meet the requirements (the difference between the measured vehicle antenna gain and the theoretical gain is greater than ±1dB), a deep installation inspection is required, such as checking whether there is metal obstruction or other wireless interference.

[0144] The testing method of the present invention is suitable for the installation inspection test of urban rail transit vehicle-mounted antennas. It can verify whether the antenna installation meets business requirements. The test is performed after the first train is detrained, effectively avoiding the situation where the vehicle needs to be modified after problems are discovered later. The method can also verify the feasibility of some special installation schemes, such as roof shark fin antennas and body side antennas, which can also be tested and verified with reference to this scheme.

[0145] The shark fin antenna on the roof and the antenna on the outer side of the car body do not need to be tested normally. Only when there is indeed obstruction, a simulation test can be performed according to the designed trackside limit installation situation. The test method is similar to the flat antenna inside the roof. Among them, the measurement points of the shark fin antenna on the roof and the antenna on the outer side of the car body can be selected from the trackside leaky cable or the position where the trackside antenna installation point is opposite to the vehicle-mounted antenna for testing. For example, the position of the trackside antenna is ±3 meters on the x-axis and 0 meters on the y-axis, and the test antenna height is the antenna height in the actual limit. When the result error of the antenna gain test is ±1dB, it is considered that the installation meets the requirements.

[0146] In summary, the vehicle-mounted antenna gain test method provided by the present invention has clear installation inspection steps, a simple test method, strong operability, and the test results can directly feedback whether the antenna installation meets the performance requirements, thereby ensuring that the train antenna is well installed and that there is good communication between the train and the trackside radio system, and there are no problems with the installation position or installation environment that affect the antenna transmission performance.

[0147] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A vehicle-mounted antenna gain test method, characterized in that: When the vehicle antenna gain test is performed at the set test point, the RF signal generated by the signal generator is transmitted to the vehicle antenna installed on the train via the RF jumper to be emitted outward, and then received by the test antenna set at the test point and transmitted to the spectrum analyzer via the RF feeder to record the received power; Calculate the calculated value G of the vehicle antenna gain according to the first formula Train : G Train =P r -P t -L Feeder -G Trackside -L FS P t is the actual transmission power of the signal generator; the actual transmission power of the signal generator is obtained by subtracting the cable loss of the RF jumper from the transmission power set by the signal generator; P r The received power recorded by the spectrum analyzer; L Feeder is the feeder loss; G Trackside To test the front lobe gain of the antenna; L FS is the free space loss; Compare the calculated value of the vehicle-mounted antenna gain with the theoretical value of the vehicle-mounted antenna gain, and determine whether the vehicle-mounted antenna installation meets the requirements based on the comparison result.

2. The vehicle-mounted antenna gain testing method according to claim 1, characterized in that: When comparing the calculated value of the vehicle-mounted antenna gain with the theoretical value of the vehicle-mounted antenna gain, further calculating the difference between the calculated value and the theoretical value, and determining whether the difference is within a threshold range; If the difference is within the threshold range, it is determined that the vehicle-mounted antenna installation meets the requirements; If the difference is not within the threshold range, it is determined that the vehicle-mounted antenna installation does not meet the requirements.

3. The vehicle-mounted antenna gain testing method as claimed in claim 2, characterized in that: When the difference between the test value and the theoretical value of the vehicle-mounted antenna gain does not exceed ±1 dB, it is considered that the vehicle-mounted antenna installation meets the requirements.

4. The vehicle-mounted antenna gain testing method according to claim 1, characterized in that: Calculate the free space loss L according to the second formula FS : Where λ is the wavelength and d is the distance between the vehicle antenna and the test antenna.

5. The vehicle-mounted antenna gain testing method according to claim 1, characterized in that: Before testing the gain of a vehicle antenna, perform the following checks: Checking the installation position of the vehicle-mounted antenna; after the installation position check is completed, the train is powered on and all wireless systems on the train are turned on; and, Perform standing wave measurement to check whether the standing wave ratio of the vehicle-mounted antenna is normal.

6. The vehicle-mounted antenna gain testing method according to any one of claims 1 to 5, characterized in that: The vehicle-mounted antenna is a flat-panel antenna; The test points include a position located directly in front of the vehicle antenna and at a set distance from the vehicle antenna, and a position located 30 degrees in front of the vehicle antenna and at a set distance from the vehicle antenna; Performing a gain test on each operating frequency point selected by the flat antenna at each test point; The test antenna is a trackside antenna arranged at a test point, and the height of the test antenna is the same as that of the vehicle-mounted antenna.

7. The vehicle-mounted antenna gain testing method as claimed in claim 5, characterized in that: The flat panel antenna includes a left antenna and a right antenna; before performing a gain test on the vehicle-mounted antenna, the installation position of the flat panel antenna is also checked to determine that the left antenna and the right antenna are respectively installed on both sides above the cab inside the train.

8. The vehicle-mounted antenna gain testing method as claimed in claim 6, characterized in that: Checking the installation position of the flat panel antenna also includes confirming whether it meets the following requirements: The flat panel antenna is installed vertically, with its front side facing the front of the train head, so that the polarization direction of the flat panel antenna is consistent with that of the trackside antenna; The flat panel antenna is fixed on a bracket having a conductive surface; The flat antenna and its bracket are considered as a whole, and a clearance of at least 5 to 10 cm is required around them; There is no metal area within 30 degrees in front of the flat antenna.

9. The vehicle-mounted antenna gain testing method according to claim 7, characterized in that: The test points corresponding to the right antenna include: A first position directly in front of the right antenna, with a distance of 3L from the right antenna; A second position on the right side of the first position and spaced apart from the first position by a distance L; Among them, L is the set unit distance; The second position corresponds to 30 degrees to the right front of the right antenna; when performing a gain test at the second position, the orientation of the right antenna is adjusted to be directly opposite the test antenna at the second position, and the result of the gain test at the second position is used to analyze the metal condition within 30 degrees of the right antenna.

10. The vehicle-mounted antenna gain testing method according to claim 8, characterized in that: The test points corresponding to the left antenna include: A third position directly in front of the left antenna and with a distance of 3L from the left antenna; A fourth position on the left side of the third position and spaced apart from the third position by a distance L; The fourth position corresponds to 30 degrees to the left front of the left antenna; when performing a gain test at the fourth position, the orientation of the left antenna is adjusted to be directly opposite the test antenna at the fourth position, and the gain test result at the fourth position is used to further analyze the metal situation within 30 degrees of the left antenna.

11. The vehicle-mounted antenna gain testing method according to claim 10, characterized in that: The test points corresponding to the right antenna further include: A fifth position directly in front of the right antenna and spaced L from the right antenna; A sixth position directly in front of the right antenna and with a distance of 2L from the right antenna; The test points corresponding to the left antenna further include: The seventh position is directly in front of the left antenna and is spaced L from the left antenna; The eighth position is directly in front of the left antenna and is 2L away from the left antenna.

12. The vehicle-mounted antenna gain testing method according to any one of claims 1 to 5, characterized in that: The vehicle-mounted antenna is a roof shark fin antenna or a vehicle body exterior side antenna; The measuring point is the position where the trackside leaky cable or trackside antenna installation point is directly opposite to the vehicle-mounted antenna; the test antenna height is the antenna height within the actual limit.

13. The vehicle-mounted antenna gain testing method according to any one of claims 1 to 5, characterized in that: The vehicle-mounted antenna gain test method is applicable to urban rail transit vehicle-mounted antennas and is implemented when the vehicle factory conducts installation inspection on the first train.

14. A vehicle-mounted antenna gain test system, used in the vehicle-mounted antenna gain test method according to any one of claims 1 to 13, characterized in that: The vehicle-mounted antenna gain test system comprises: A signal generator, used for generating a radio frequency signal; A radio frequency jumper, connecting the signal generator to the vehicle-mounted antenna, and used to transmit the radio frequency signal to the vehicle-mounted antenna; A test antenna, located at a set test point, for receiving the radio frequency signal emitted by the vehicle-mounted antenna; A radio frequency feeder, connecting the test antenna to a spectrum analyzer and used to transmit the radio frequency signal to the spectrum analyzer; The spectrum analyzer is used to record the received power; A processor, configured to receive the input parameters and calculate the calculated value G of the vehicle-mounted antenna gain according to the first formula Train : G Train =P r -P t -L Feeder -G Trackside -L FS The parameters include: The spectrum analyzer records the received power P r ; Feeder loss L Feeder ; Test the front lobe gain G of the antenna Trackside ; Free space loss L FS ; The processor is used to subtract the cable loss of the RF jumper from the transmission power set by the signal generator to obtain the actual transmission power P of the signal generator. t ; The processor is also used to receive a theoretical value of the vehicle-mounted antenna gain, and compare the calculated value of the vehicle-mounted antenna gain with the theoretical value, and determine whether the vehicle-mounted antenna installation meets the requirements according to the comparison result.

15. The vehicle-mounted antenna gain test system according to claim 14, characterized in that: The test antenna is installed via an antenna pole, and is set to the same height as the vehicle-mounted antenna.

16. The vehicle-mounted antenna gain test system according to claim 14, characterized in that: The processor is further used to calculate the difference between the calculated value and the theoretical value of the vehicle-mounted antenna gain, and determine whether the difference is within a threshold range; If the difference is within the threshold range, it is determined that the vehicle-mounted antenna installation meets the requirements; If the difference is not within the threshold range, it is determined that the vehicle-mounted antenna installation does not meet the requirements.

17. The vehicle-mounted antenna gain test system according to claim 14, characterized in that: The processor is also used to receive the wavelength λ, the distance d between the vehicle antenna and the test antenna, and calculate the free space loss L according to the second formula FS : The processor then converts the obtained free space loss L FS A calculated value used to calculate the gain of the vehicle-mounted antenna.

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