CN112526224A - Passive performance test method for vehicle-mounted V2X PC5 communication antenna - Google Patents
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Abstract
The invention provides a passive performance test method for a vehicle-mounted V2X PC5 communication antenna, which comprises the following steps: s1, placing the test vehicle in a darkroom for experimental environment test; s2, cable calibration and space attenuation calibration are carried out on the antenna performance test; and S3, testing the performance of the antenna to obtain a test result. The method provided by the invention aims at the characteristics of large volume and heavy weight of the automobile, and provides a method for testing the passive performance of a V2X PC5 communication antenna suitable for the whole automobile.
Description
Technical Field
The invention belongs to the technical field of antenna testing, and particularly relates to a passive performance testing method for a vehicle-mounted V2X PC5 communication antenna.
Background
With the continuous progress of the intelligent networking automobile technology, the information interaction between the automobile and the outside is more frequent, and as a necessary interface for wireless information interaction, the performance requirement of the antenna directly influences the safety and reliability of the intelligent networking function. With the loading application of a series of intelligent networking systems such as a satellite navigation system, a 4G communication system, a 5G communication system, an automatic driving system and a C-V2X, more and more antenna devices and communication devices are installed on the intelligent networking vehicle, and because the working purposes and the working frequencies of the antennas of the systems are different, the installation positions of the antennas are distributed all over the vehicle body, so that accurate measurement of the performance of the vehicle-mounted antenna system becomes very important for ensuring the wireless information interaction capability of the vehicle.
With the deep development of the intelligent networked automobile, the automobile wireless communication is used as a basic element of Vehicle intellectualization, networking and automatic driving, the realization of the related functions of the intelligent networked automobile is influenced to a great extent by the wireless communication performance, and the V2X (Vehicle to evolution) communication technology is used as an information interaction key technology in the intelligent networked automobile and is mainly used for realizing the communication guarantee of workshop information sharing and cooperative control. The V2X PC5 antenna realizes a V2V communication function in vehicle networking information interaction and is related to the driving safety of intelligent networking vehicles, so that the passive performance test of the vehicle-mounted V2X PC5 communication antenna is particularly important.
Disclosure of Invention
In view of the above, the invention aims to provide a passive performance testing method for a vehicle-mounted V2X PC5 communication antenna, so as to solve the problem that an intelligent internet vehicle LTE-V2X antenna has a shielding effect on the antenna performance and the vehicle body has an influence on the antenna performance testing.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
a passive performance test method for a vehicle-mounted V2X PC5 communication antenna comprises the following steps:
s1, placing the test vehicle in a darkroom for experimental environment test;
s2, cable calibration and space attenuation calibration are carried out on the antenna performance test;
and S3, testing the performance of the antenna to obtain a test result.
Further, the darkroom in the step S1 is a darkroom without electromagnetic wave reflection.
Further, the cable calibration process in step S1 is as follows: because the coaxial cable III connected to the outside of the darkroom below the center of the turntable can not be directly connected to two ends of the network analyzer for measurement, another coaxial cable I is needed as a reference, the attenuation of the coaxial cable I is measured firstly as a normalization process, then the coaxial cable III and the coaxial cable are connected together, and then the coaxial cable III under the turntable is connected to be calibrated.
Further, the spatial attenuation calibration procedure in step S1 is as follows: a standard gain horn antenna was used as the reference antenna. Placing the reference antenna on a wooden table with the height of 1.5m, and enabling the distance between the reference antenna and the test antenna to be 1.5 m;
after a vertical cable and a horizontal polarization cable outside a darkroom are connected with a cable under a rotary table to form a total cable, two ends of the total cable are connected to two ends of a network analyzer, the attenuation sum of the vertical cable and the horizontal polarization cable is respectively recorded as a normalization process, then the cable under the rotary table is connected to a reference antenna to be used as a transmitting end, the vertical cable and the horizontal polarization cable are respectively connected to a test antenna to be used as a receiving end, and the space attenuation size under the vertical polarization and the horizontal polarization is recorded.
Further, the process of testing the antenna performance in step S4 is as follows:
step S3, disconnecting the tested antenna of the vehicle from the vehicle-mounted terminal, connecting the tested antenna with the port 1 of the network analyzer, and connecting the testing antenna with the port 2 of the network analyzer;
step 4, keeping the vertical angle of the antenna probe unchanged, and rotating in the horizontal direction for testing;
and 5, connecting the tested antenna with the port 1 of the network analyzer, and repeating the step 4 to obtain the horizontal and vertical polarization directional diagram of the antenna.
Compared with the prior art, the passive performance testing method for the vehicle-mounted V2X PC5 communication antenna has the following advantages:
(1) the method provided by the invention aims at the characteristics of large volume and heavy weight of the automobile, and provides a method for testing the passive performance of a V2X PC5 communication antenna applicable to the whole automobile.
(2) The method of the invention evaluates parameters such as a directional diagram, a maximum gain, a linear average gain and the like.
(3) The method provided by the invention provides a method for evaluating average gain in horizontal direction by regions aiming at the communication characteristics of V2X antenna, and puts emphasis on requirements on the front and the rear of a vehicle
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic diagram of a spherical coordinate system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a circular cone cutting positioning system according to an embodiment of the present invention;
FIG. 3 is a schematic diagram illustrating sample point distribution during a testing process according to an embodiment of the present invention;
FIG. 4 is a schematic view of a cable calibration according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of spatial attenuation calibration according to an embodiment of the present invention;
FIG. 6 is a schematic diagram illustrating a test of an antenna of a vehicle according to an embodiment of the present invention;
FIG. 7 is a diagram of a complete vehicle and single antenna pattern in accordance with an embodiment of the present invention;
fig. 8 is a schematic diagram of vehicle region division according to an embodiment of the present invention.
Detailed Description
It should be noted that the embodiments and features of the embodiments of the present invention may be combined with each other without conflict.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
As shown in fig. 1 to 8, a passive performance testing method for a vehicle-mounted V2X PC5 communication antenna includes the following steps:
s1, placing the test vehicle in a darkroom for experimental environment test;
s2, cable calibration and space attenuation calibration are carried out on the antenna performance test;
and S3, testing the performance of the antenna to obtain a test result.
The darkroom in the step S1 is a darkroom without electromagnetic wave reflection.
The cable calibration process in step S1 is as follows: because the coaxial cable III connected to the outside of the darkroom below the center of the turntable can not be directly connected to two ends of the network analyzer for measurement, another coaxial cable I is needed as a reference, the attenuation of the coaxial cable I is measured firstly as a normalization process, then the coaxial cable III and the coaxial cable I are connected together, and then the coaxial cable III under the turntable is connected to be calibrated.
The spatial attenuation calibration procedure in step S1 is as follows: a standard gain horn antenna was used as the reference antenna. Placing the reference antenna on a wood desk with the height of 1.5m, and enabling the distance between the reference antenna and the test antenna to be 1.5 m;
after a vertical cable and a horizontal polarization cable outside a darkroom are connected with a cable under a rotary table to form a total cable, two ends of the total cable are connected to two ends of a network analyzer, the attenuation sum of the vertical cable and the horizontal polarization cable is respectively recorded as a normalization process, then the cable under the rotary table is connected to a reference antenna to be used as a transmitting end, the vertical cable and the horizontal polarization cable are respectively connected to a test antenna to be used as a receiving end, and the space attenuation size under the vertical polarization and the horizontal polarization is recorded.
The process of testing the antenna performance in step S4 is as follows:
step S3, disconnecting the tested antenna of the vehicle from the vehicle-mounted terminal, connecting the tested antenna with the port 1 of the network analyzer, and connecting the testing antenna with the port 2 of the network analyzer;
step 4, keeping the vertical angle of the antenna probe unchanged, and rotating in the horizontal direction for testing;
and 5, connecting the tested antenna with the port 1 of the network analyzer, and repeating the step 4 to obtain the horizontal and vertical polarization directional diagram of the antenna.
The specific introduction is as follows:
the invention introduces the minimum far field test distance and the spherical near field test theory, and can obtain the feasibility of using the spherical near field technology in the automobile antenna test through analysis.
By referring to the particularity of the vehicle-mounted antenna of the automobile, the test environment requirement, the test equipment requirement, the calibration method, the test arrangement method and the passive performance test flow for the vehicle-mounted antenna of the automobile are further provided, and the LTE-V2X antenna is actually tested in the whole automobile environment and the single body simulation whole automobile environment respectively. In the comparison of test results, parameters such as a directional diagram, maximum gain, linear average gain, half-power beam width, gain flatness and the like are selected to compare the performance of the antenna under the single simulation whole vehicle and the actual whole vehicle environment.
Due to the particularity of the V2X antenna communication, the communication quality in front of and behind the vehicle is emphasized more in the actual road state, and the requirement on the side communication quality is not high. The vehicle is divided into 4 sections in the horizontal direction, and the angular range is shown in fig. 8. The test result shows that the average gain values of the head part and the tail part are close, but the average gain values of the two sides of the vehicle are smaller than those of the head part and the tail part, and the expected function requirements of V2X communication are met.
At present, the automobile industry is basically in a blank state aiming at the performance test of a whole automobile-level automobile antenna, however, the rapid development of the intelligent networking automobile requires that the communication between the automobile and the outside is reliable and stable, the antenna is used as a medium in the communication process, and the performance of the antenna determines the functional application of the intelligent networking automobile. Mature antenna test methods are concentrated in the mobile communication industry, but the characteristics of large volume and heavy weight of an automobile lead the performance test method of the automobile antenna to be different from that of a mobile communication terminal; therefore, the invention takes the LTE-V2X antenna as an example, and researches the passive performance test method of the automobile antenna.
Minimum far field distance:
when the automobile antenna test is carried out, the minimum far-field measurement distance needs to be considered, so that whether the test data is a far-field result or a near-field result is judged. The far field minimum test distance R is defined as the distance from the center of rotation of the object under test to the center of the phase of the measuring antenna. The minimum far field test distance per frequency band is
Wherein D is the maximum size of the object to be measured; λ is the wavelength of the electromagnetic wave of a specific frequency in free space.
Since the transmission speed of electromagnetic wave is the same as the speed of light, the frequency of electromagnetic wave has a wavelength relationship of
λ＝c/f (2)
Wherein f is the frequency of the electromagnetic wave; c is the propagation velocity of light, and has a value of 3X 108 m/s.
The frequency relationship between the minimum far-field measurement distance and the electromagnetic wave can be obtained by substituting the formula (2) into the formula (1)
Considering that the length of the body of a conventional automobile is generally close to 5m, if the whole automobile is regarded as a measured object, the far-field minimum test distance obtained according to equation (3) is shown in table 1.
TABLE 1 minimum far-field test distance
As can be seen from table 1, when the antenna is a radio antenna, i.e. the frequency is around 100MHz, the far field measurement distance is about 17 meters. However, when the antenna frequency is at 6GHz, the far field distance is up to 1000 m. This means that if the far-field test method is still used, it is difficult to select a test site that meets the test requirements, and in addition, the test signal is substantially attenuated and disappears at a longer distance, and no practical result can be detected. The minimum measurement distance between the measurement antenna and the automobile is about 1.5m according to the vehicle volume and the test method reasonableness.
Spherical near-field testing technology
Electromagnetic waves propagate energy outwards in the form of spherical waves, and when transmitted to infinity, electromagnetic energy received by a point can be relatively single and equivalently regarded as uniform plane waves, so that a specific electromagnetic wave can be naturally decomposed into a plurality of plane electromagnetic waves transmitted outwards from a source in the radial direction. On the basis, as long as the theoretical expressions of the plane electromagnetic waves are obtained, the spherical wave expression of the electromagnetic waves can be obtained through accumulation by adopting a mathematical method. The method for solving the planar wave expansion of each mode of the spherical wave is called a spherical wave mode expansion theory.
The spherical wave Spread (SWE) of the electric field radiated by the antenna into free space can be defined as a weighted sum of spherical vector wave functions.
In the formula, QsmnFor complex expansion coefficients, k is the wavenumber, k is 2 pi/λ, λ is the wavelength, η is the free space admittance, (r, θ, φ) is the spherical coordinate angle.
The triple sum in formula (4) is understood to be
The following formula is provided for determining the maximum modulus N of the spherical wave mode expansion coefficient
N＝[krt]+10 (6)
In the formula, rtIs the effective spherical radius that represents the complete coverage of the target antenna.
In the test sampling, the value range in the theta direction is generally 0-theta < pi due to the self-symmetry. Therefore, in the theta direction, the sampling interval delta theta is pi/N, a zero point is calculated, and the number of sampling points is N + 1; in the phi direction, the value range is generally as follows for accurate measurement
And in the phi direction, the sampling interval delta phi is pi/N, and the number of the last sampling points added with the zero point is 2N + 1.
Spherical vector wave function
Can be defined as:
in the formula, we assume and compress the time dependency e-iωtIn formulae (7) and (8)
The first spherical Hankel function, corresponding to outward propagation,
is a normalized correlation Legendre function, in this representation any single radiating spherical wave with unit amplitude will radiate 0.5 watts of power. Thus, the above expansion is referred to as power normalized spherical wave expansion, in which the wave function
Is dimensionless and extends the coefficient QsmnIs changed into [ watt ]]1/2. Then, the total power radiated from the test antenna becomes
The feasibility of using the spherical near-field technology in the automobile antenna test can be obtained through the analysis, and in addition, the sampling precision is specified in the theory so as to ensure that the far-field result can be accurately calculated through near-field and far-field conversion.
Due to the characteristics of large volume and heavy weight of the automobile and the limitation of the size of a darkroom, the antenna test of the whole automobile adopts a near-field measurement technology. In addition, the spherical near-field test technology is a simpler scheme in terms of test implementation difficulty and support of the antenna to be tested.
In practical engineering, the whole spherical near-field test system is divided into the following subsystems: the system comprises a mechanical system, a radio frequency system, a data acquisition and control system and a data processing system. The measurement system completes the sampling and data conversion processing of the near field data through the division and cooperation of different subsystems.
A spherical near-field test coordinate system and polarization relation are shown in FIG. 1, and the coordinate system is expressed by using a spherical coordinate system, namely, a spherical coordinate system
To represent the test angles, the test antenna at each angle can be divided into two cross-polarizations: theta polarization and phi polarization.
The three-dimensional scanning mode selects a cone cutting method. Wherein, the device to be tested is placed on the turntable and rotates 360 degrees along the horizontal direction. The antenna bracket drives the test antenna to rotate in the vertical direction, and the antenna performance of a plurality of positions is measured from top to bottom. As shown in fig. 2.
Considering the use condition of the automobile, in the range of theta of 0-90 degrees, namely the upper part of the turntable above the ground, the test is necessary, namely the upper hemisphere test is met at minimum. Furthermore, the origin (sphere center) of the test system must be above the turntable. The distribution diagram of the specific sampling points is shown in fig. 3.
Automobile antenna performance test method
The test method of the automobile antenna performance test under the environment of the whole automobile and the single body simulation whole automobile is similar, and the test arrangement is slightly different. The following describes the test equipment and the detailed test method.
(1) Test environment
Because the purpose of the vehicle-mounted antenna performance test is to obtain the direct transmission performance of the vehicle-mounted antenna under the whole vehicle working condition, the vehicle needs to be placed in an environment without electromagnetic wave reflection, and a full-electric wave darkroom is recommended.
(2) Test apparatus
Because a three-dimensional directional diagram needs to be obtained in the performance test of the vehicle-mounted antenna, a rotary table needs to be installed in the anechoic chamber, the rotation in the horizontal direction is realized, and the precision of the rotary table needs to reach 0.1 degree. The rotation in the vertical direction is realized by driving the test antenna by the cone cutting positioning system.
The transmission and the reception of the antenna performance test signals are completed by the network analyzer, the transmission and the reception are reciprocal because the passive performance of the antenna is tested, and the vehicle-mounted antenna is used for transmitting and testing the antenna for receiving in the test. The test antenna is a cross-polarized antenna.
(3) Calibration method
The calibration before the antenna performance test is divided into two steps: cable calibration and spatial attenuation calibration.
As shown in fig. 4, cable calibration is performed first. Because the coaxial cable L3 connected to the outside of the darkroom under the center of the turntable cannot be directly connected to two ends of the network analyzer for measurement, another coaxial cable L0 is needed as a reference, the attenuation of the L0 cable is measured firstly as a normalization process, then the L3 and the L0 are connected together, and the cable L3 under the turntable is calibrated.
A standard gain horn antenna was used as the reference antenna in the spatial attenuation calibration as shown in fig. 5. The reference antenna was placed on a wooden table 1.5m high, with a distance of 1.5m between the reference antenna and the test antenna.
After connecting L1 or L2 and L3 to one cable, respectively, both ends of the cable were connected to both ends of a network analyzer, and the sum of the attenuations of the two cables, which are vertically and horizontally polarized, was recorded as a normalization process. L3 was then connected to the reference antenna as the transmit side, L1 and L2 were connected to the test antenna as the receive side, respectively, and the magnitudes of the spatial attenuations in the vertical and horizontal polarizations were recorded.
(4) Test procedure
Since the main communication environment of the V2X antenna is around the horizontal plane, limited by the mechanical accuracy of the scanning gantry, the test antenna and the vehicle antenna are adjusted to be consistent in height and should be aligned.
When the test is carried out in the whole vehicle environment, the center of the vehicle is aligned to the center of the turntable, the distance between the test antenna and the vehicle-mounted antenna is adjusted to be 1.5m, and then the center of the test antenna is aligned to the center of the vehicle-mounted antenna. In addition, the vehicle should be in a power-off state, and the antenna and the vehicle-mounted terminal are disconnected. The vehicle antenna test layout is shown in fig. 6.
When the test under the single-body simulation whole vehicle environment is carried out, a proper wood table is selected according to the height of the vehicle roof, a round aluminum plate with a small hole formed in the center is placed on the wood table, the vehicle-mounted antenna is placed in the center of the aluminum plate, the antenna support is adjusted to enable the test antenna and the vehicle-mounted antenna to be located on the same horizontal plane, the distance between the test antenna and the vehicle-mounted antenna is adjusted to be 1.5m, and then the center of the test antenna is aligned to the center of the vehicle-.
The test flow of the vehicle-mounted antenna is similar in the whole vehicle environment and the single body simulation whole vehicle environment. The measured piece is defined as a whole car or a wood table with an aluminum plate at 1.5m height.
a) Placing the measured piece at the center of the rotary table, and enabling the center of the measured piece to be superposed with the center of the rotary table; taking the automobile head direction and the turntable reference angle of 0 degree as a horizontal reference starting point;
b) placing an antenna probe on the same horizontal plane with the measured antenna of the vehicle as a vertical reference starting point for measurement;
c) disconnecting the vehicle antenna to be tested from the OBU, and connecting the radio frequency interface of the antenna to be tested with the port 1 of the network analyzer to be used as a transmitting antenna; the horizontal polarization interface of the test antenna is connected with a port 2 of the network analyzer;
d) keeping the vertical angle of the antenna probe unchanged, and rotating in the horizontal direction for testing; in the test process, the rotary table rotates 360 degrees anticlockwise along the horizontal direction, and corresponding angle values and gain values are recorded to obtain a horizontal polarization directional diagram of the horizontal plane of the antenna;
e) connecting the vertical polarization interface of the test antenna with the port 1 of the network analyzer, and repeating the step d to obtain an antenna horizontal plane vertical polarization directional diagram;
comparison of test results
In the test, the vehicle-mounted antenna is a V2X antenna, the test frequency range is 5860 MHz-5960 MHz, the frequency step is 5MHz, the test angle is theta limited by independently manufacturing the antenna bracket at the present stagenAt 0 deg..
In the result comparison, parameters such as a directional diagram, maximum gain, linear average gain, half-power beam width, gain flatness and the like are selected to compare the performance of the antenna under the single simulation whole vehicle and the actual whole vehicle environment. Wherein, the comparison graph of the directional diagram is shown in fig. 7, wherein the left side of the graph is the whole vehicle part, the right side is the single part, and the comparison of other parameters is listed in table 2.
TABLE 2 passive performance comparison table for whole vehicle and single antenna
The influence of the shape of the roof of the whole vehicle is received, the vehicle-mounted antenna is not free from shielding and reflecting phenomena, the shape of a directional diagram also shows that the burrs in the directional diagram under the single environment are obviously smaller than those under the whole vehicle environment. In addition, the maximum gain of the vehicle-mounted antenna under the whole vehicle environment is about 10% smaller than that under the single environment, and the average gain is about 20% smaller than that under the single environment; the shapes of directional diagrams in two environments are greatly different, so that the half-power beam width has little contrast significance; and the gain flatness under the whole vehicle environment is worse than that under the monomer condition, and the difference is about 10%.
Due to the particularity of the V2X antenna communication, the communication quality in front of and behind the vehicle is emphasized more in the actual road state, and the requirement on the side communication quality is not high. Thus dividing the vehicle into 4 sections around the vehicle, the angular range is shown in fig. 8. The average gain is solved according to the area for the gain data under the whole vehicle environment, and the obtained result is shown in table 3.
TABLE 3 comparison table of average gain of each region
From the results in table 3, it can be seen that the average gain values of the front and rear portions are similar, but the average gain values of both sides of the vehicle are smaller than those of the front and rear portions, and meet the expected functional requirements of V2X communication.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (5)
1. A passive performance test method for a vehicle-mounted V2X PC5 communication antenna is characterized by comprising the following steps:
s1, placing the test vehicle in a darkroom for experimental environment test;
s2, cable calibration and space attenuation calibration are carried out on the antenna performance test;
and S3, testing the performance of the antenna to obtain a test result.
2. The passive performance test method of the vehicle-mounted V2X PC5 communication antenna of claim 1, characterized in that: the darkroom in the step S1 is a darkroom without electromagnetic wave reflection.
3. The passive performance test method of the vehicle-mounted V2X PC5 communication antenna of claim 1, characterized in that: the cable calibration process in step S2 is as follows: because the coaxial cable III connected to the outside of the darkroom below the center of the turntable can not be directly connected to two ends of the network analyzer for measurement, another coaxial cable I is needed as a reference, the attenuation of the coaxial cable I is measured firstly as a normalization process, then the coaxial cable III and the coaxial cable are connected together, and then the coaxial cable III under the turntable is connected to be calibrated.
4. The passive performance test method of the vehicle-mounted V2X PC5 communication antenna of claim 1, characterized in that: the spatial attenuation calibration procedure in step S2 is as follows: a standard gain horn antenna was used as the reference antenna. Placing the reference antenna on a wooden table with the height of 1.5m, and enabling the distance between the reference antenna and the test antenna to be 1.5 m;
after a vertical cable and a horizontal polarization cable outside a darkroom are connected with a cable under a rotary table to form a total cable, two ends of the total cable are connected to two ends of a network analyzer, the attenuation sum of the vertical cable and the horizontal polarization cable is respectively recorded as a normalization process, then the cable under the rotary table is connected to a reference antenna to be used as a transmitting end, the vertical cable and the horizontal polarization cable are respectively connected to a test antenna to be used as a receiving end, and the space attenuation size under the vertical polarization and the horizontal polarization is recorded.
5. The passive performance test method of the vehicle-mounted V2X PC5 communication antenna of claim 1, characterized in that: the process of testing the antenna performance in step S3 is as follows:
step 1, placing a vehicle on a rotating platform installed in an environment without electromagnetic wave reflection, enabling the center of the vehicle to coincide with the center of the rotating platform, and enabling the direction of a vehicle head and the reference angle of the rotating platform to be 0 degree to serve as a horizontal reference starting point;
step 2, placing the test antenna probe on the same horizontal plane of the tested antenna of the vehicle to be used as a vertical reference starting point of the vehicle;
step S3, disconnecting the tested antenna of the vehicle from the vehicle-mounted terminal, connecting the tested antenna with the port 1 of the network analyzer, and connecting the testing antenna with the port 2 of the network analyzer;
step 4, keeping the vertical angle of the antenna probe unchanged, and rotating in the horizontal direction for testing;
and 5, connecting the tested antenna with the port 1 of the network analyzer, and repeating the step 4 to obtain the horizontal and vertical polarization directional diagram of the antenna.
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