Method for analyzing characteristics of a leaky cable channel of a vacuum maglev train based on multi-source geometry

Abstract

The application provides a kind of vacuum maglev train leakage cable channel characteristic analysis method based on multi-source geometry.The method comprises: the gap of the leakage cable of the vacuum maglev train is equivalent to a magnetic dipole antenna, based on the radiation electric field distribution characteristics of the gap of the leakage cable of the magnetic dipole antenna, the LoSLoS radial electric field intensity and the NLoSLoS radial electric field intensity of the radiation electric field of the gap of the leakage cable are obtained;According to the LoS radial electric field intensity and the NLoS radial electric field intensity, the multi-source channel of the leakage cable is modeled, the channel impulse response expression of a single magnetic dipole antenna under LoS and NLoS conditions is obtained, the channel impulse responses of the gap equivalent magnetic dipole antenna under LoS and NLoS conditions are superimposed, and the complete leakage cable channel impulse response expression form under the running scene of the vacuum maglev train is obtained.The application constructs the electric field distribution under the running scene of the vacuum maglev train, and deduces the complete leakage cable channel impulse response expression form under the running scene of the vacuum maglev train.

Description

Technical Field

[0001] This invention relates to the field of vacuum maglev train technology, and in particular to a method for analyzing the channel characteristics of leaky cables in vacuum maglev trains based on multi-source geometry. Background Technology

[0002] While traditional wheel-rail high-speed rail is developing rapidly in China, the development of ultra-high-speed rail—the vacuum tube maglev train, known as the "fifth mode of transportation"—is also gradually coming into people's view. The vacuum tube maglev train is a new type of rail transportation that operates without onboard power in a low-mechanical-friction, low-aerodynamic-resistance, and low-noise mode. It achieves ultra-high-speed rail transport exceeding 1000 km / h by constructing a sealed tube above or below ground and using a vacuum pump to extract air into the tube, creating a vacuum or partial vacuum state inside.

[0003] In recent years, the research and development of vacuum tube maglev trains has accelerated both domestically and internationally. In China, in 2014, Southwest Jiaotong University built a prototype test platform for a 6-meter-radius vacuum tube ultra-high-speed maglev train, with the model train capable of reaching a maximum operating speed of 50 km / h. In May 2020, Southwest Jiaotong University launched the "Multi-Mode Coupled Rail Transit Dynamic Test Platform" project, which will construct a 1620-meter-long elevated vacuum tube high-temperature superconducting maglev transportation comprehensive research and test platform with a designed maximum test speed of 1500 km / h.

[0004] The safe and efficient operation of vacuum tube maglev trains relies on the support and guarantee of a stable and reliable wireless communication system. As the foundation of wireless communication system design, an accurate wireless channel provides crucial guidance for technical evaluation, system simulation, and network coverage planning during system design.

[0005] The vacuum tube system in existing technologies is still in the testing and verification stage, and research on its actual wireless channel measurement and modeling remains limited; therefore, theoretical simulation can be used to simulate the vacuum tube environment. Previous studies have used some theoretical methods to conduct preliminary research on vehicle-to-ground wireless communication. Existing technologies include schemes that use propagation graph theory to model the wireless channel in the vacuum tube scenario and analyze the relevant location-based wireless channel characteristics. Other existing technologies have developed a 3D non-stationary millimeter-wave (mmWave) GBSM model to explore the channel characteristics in the vacuum tube scenario and studied several key time-varying channel statistical characteristics, comparing them with existing HST and tunnel channels. Furthermore, existing technologies have proposed a novel integrated sensing and communication GBSM channel model combining forward and backscattering and studied the correlation between the sensing and communication channels. Finally, existing technologies have used a new deterministic model based on three-dimensional non-stationary geometry to analyze the effective scattering of wireless communication between the hyperloop train and the distribution characteristics of azimuth and elevation angles. Existing technologies and methods also employ ray tracing to simulate the radio wave propagation characteristics in a 3.5 GHz vacuum tube environment and analyze path loss under different deployment configurations. Other existing technologies and methods use ray tracing to study the wireless channel characteristics of Hyperloops in four different millimeter-wave frequency bands and analyze large-scale and small-scale channel characteristics, including path loss, shadowing fading, delay spread, and angular spread. There are also some vacuum tube channel modeling methods based on hybrid models.

[0006] Using leaky coaxial cables (LCXs) in high-speed railway tunnels can reduce the impact of complex channel characteristics on signal transmission, while improving the reliability, stability, and efficiency of signal transmission. Due to the structural similarities between railway tunnels and vacuum tubes, existing research on tunnel-based wireless channel modeling can serve as a reference. Utilizing the electric field distribution of leaky cables, existing technologies have derived the CIR function of communication channel models in high-speed railway tunnel scenarios and developed a geometry-based single-bounce multiple-input multiple-output (GBSB-MIMO) channel model for high-speed railway communication systems. Other existing technologies propose an improved geometry-based GBSB-MIMO channel model, considering the Doppler spread effect, and study its time-domain statistics through numerical simulation. Furthermore, the impact of different factors (including cable trench spacing and the number and location of LCXs) on 5G system-level performance is analyzed. Finally, existing technologies have developed a 3D non-stationary MIMO leaky cable channel model for high-mobility wireless communication systems in high-speed railway tunnel scenarios, considering the 1.8 GHz band and a high-speed railway operating speed of 360 km / h.

[0007] Currently, existing methods for studying the propagation characteristics of electromagnetic waves in confined spaces include ray tracing, waveguide theory, and finite-difference electromagnetic theory calculations. Ray tracing, however, struggles to statistically identify all electromagnetic wave propagation paths, involves significant computational costs, and is not adept at accurately describing tunnel propagation characteristics. Waveguide theory directly approximates a tunnel as a large-scale waveguide and uses related theories to describe the propagation patterns of electromagnetic waves within it. Its limitation lies in the fact that tunnels lack the shape and regularity of waveguides, thus restricting this approximation. Finite-difference electromagnetic theory calculations primarily model the propagation process of electromagnetic waves starting from the emission source based on Maxwell's equations. This method offers high modeling accuracy, but even using a simplified version of the vector parabolic equation method, the computational load remains substantial. Summary of the Invention

[0008] This invention provides a method for analyzing the channel characteristics of leaky cables in vacuum maglev trains based on multi-source geometry, so as to effectively analyze the non-stationary channel characteristics in the scenario of leaky cables in vacuum maglev trains.

[0009] To achieve the above objectives, the present invention adopts the following technical solution.

[0010] A method for analyzing the channel characteristics of leaky cables in vacuum maglev trains based on multi-source geometry, comprising: The leaky cable gap of the vacuum maglev train is equivalent to a magnetic dipole antenna. Starting from the electromagnetic wave propagation mechanism, the characteristics of the radiated electric field distribution of the magnetic dipole antenna in the leaky cable gap in the confined narrow pipe are analyzed. Based on the electric field distribution characteristics of the leaky cable gap of the magnetic dipole antenna, the LoS-radiated electric field intensity and NLoS-radiated electric field intensity of the leaky cable gap are obtained. The multi-source channel of the leaky cable is modeled based on the LoS and NLoS electric field strengths. The channel impulse response expressions of a single magnetic dipole antenna under LoS and NLoS conditions are obtained. The channel impulse responses of the slot equivalent magnetic dipole antenna under LoS and NLoS conditions are superimposed to obtain the complete channel impulse response expression form of the leaky cable under the operation scenario of a vacuum maglev train.

[0011] Preferably, the method of equating the leaky cable gap of the vacuum maglev train with a magnetic dipole antenna, and analyzing the radiated electric field distribution characteristics of the magnetic dipole antenna in the leaky cable gap within a confined narrow pipe based on the electromagnetic wave propagation mechanism, includes: The slotting methods of the leakage cable of the vacuum maglev train are divided into vertical slotting, inclined slotting and symmetrical inclined slotting. The polarization mode of the vertical slotted leakage cable is horizontal polarization, while the polarization mode of the inclined slotted and symmetrical inclined slotted leakage cables is vertical polarization. The total electric field intensity of the vertical slotted leakage cable is expressed as the vector superposition of the electric field intensity components along the axial direction and the circumferential direction along the leakage cable. The gaps in the leaky cable of the vacuum maglev train are equivalent to magnetic dipole antennas, and the electric field strength of a single slot in the leaky cable is expressed as:

[0012] in The electric field strength at point m in the leaky cable tray opening is given. This represents the distance from the opening of the leaky cable tray to the position within the electromagnetic field radiated from the tray opening. This indicates the angle between the line connecting this location to the slot opening and the axial direction of the leaky cable in the electromagnetic field. Let be the propagation constant of electromagnetic waves in free space, expressed as:

[0013] in The wavelength of electromagnetic waves; There are also losses during the transmission of electrical signals inside the leaky cable. Let the electric field strength at the feed end be... Then the first The electric field strength at each slot is:

[0014] In the formula, Indicates the leakage cable number The attenuation coefficient of the signal from each slot to the signal feed end is expressed as:

[0015] in, For the first The attenuation of the electric field intensity amplitude at each slot, For the first The phase change of the electric field intensity at each slot, based on the electrical characteristics of the leaky cable, the power attenuation constant inside the leaky cable is... The amplitude attenuation and phase change of the signal at the m-th slot are expressed as:

[0016] in, and These represent the signal amplitude attenuation and signal phase change between adjacent slots inside the leaky cable, respectively. For the slot cycle, The propagation constant inside a leaky cable is expressed as:

[0017] in, It is the relative permittivity of the medium inside the leaking cable.

[0018] Preferably, the method of obtaining the LoS-radiated electric field intensity and NLoS-radiated electric field intensity of the leaky cable gap based on the electric field distribution characteristics of the magnetic dipole antenna includes: The electromagnetic field radiation path of the leaky cable of the vacuum maglev train is divided into LoS ​​path and NLoS path. The leaky cable has M slots, and the vacuum tube wall has N scatterers. The electric field strength at the receiving end of the leaky cable is expressed as:

[0019] in, and These are the electric field levels along the LoS and NLoS paths of the receiving antenna, respectively. The electric field strength along the LoS path from the m-th slot of the leaky cable to the receiving antenna on the vacuum maglev train is expressed as:

[0020] in, To reduce the electric field strength at the cable tray opening, This represents the LoS path distance from the m-th slot of the leaky cable to the slot in the radiated electromagnetic field. This indicates the angle between the line connecting the receiving antenna position to the m-th slot and the axial direction of the leaky cable. Based on the signal attenuation characteristics within a leaky cable:

[0021] Substituting equation (10) into equation (9), we obtain the electric field intensity of the LoS radius as follows:

[0022] in, The electric field strength at the feed end, and These represent the signal amplitude attenuation and signal phase change at the m-th slot of the leaky cable, respectively. Let L be the distance from the m-th slot of the leaky cable to the receiving point (LoS). This indicates the angle between the line connecting the receiving antenna position to the m-th slot and the axial direction of the leaky cable. The radiation field at the m-th slot of the leaky cable is reflected or scattered by a reflector or scatterer. The expression for the NLoS electric field strength reaching the receiving antenna is:

[0023] in scattering body The expression for the electric field intensity at that location, Let be the distance from the scatterer to the receiving antenna. The derivation process is based on the LoS radius electric field strength. The calculation formula is as follows:

[0024] in The distance from the slot opening m to the scatterer. Substituting equation (13) into equation (12), we get:

[0025] in and From slot m to the scatterer scatterer Distance to the receiving antenna scattering body The angle between the line connecting the slot m and the axial direction of the leaky cable; Substituting equation (10) into equation (14), we get:

[0026] in, The electric field strength at the feed end, This indicates signal amplitude attenuation between adjacent slots inside the leaky cable. For the slot cycle, This represents the propagation constant inside a leaky cable. Represents the propagation constant within the pipe. and From slot m to the scatterer scatterer Distance to the receiving antenna scattering body The angle between the line connecting the slot m and the axial direction of the leaky cable.

[0027] Preferably, the process of modeling the multi-source channel of the leaky cable based on the LoS and NLoS electric field strengths, obtaining the channel impulse response expression of a single magnetic dipole antenna under LoS and NLoS conditions, and superimposing the channel impulse responses of the slot-equivalent magnetic dipole antenna under LoS and NLoS conditions to obtain the complete leaky cable channel impulse response expression form under the operation scenario of a vacuum maglev train includes: In a vacuum tube channel environment, taking the channel from the p-th of the leaky cable to the q-th of the receiving antenna as an example, the channel impulse response of a single magnetic dipole antenna is expressed as:

[0028] 1) Superimpose the channel impulse responses of the slot-equivalent magnetic dipole antenna in the LoS path component to obtain the complete LoS path channel impulse response of the leaky cable in the operation scenario of a vacuum maglev train. :

[0029] In the above formula, For leaky cables to receiving antenna Total energy of the link This is the Rice K-factor of the link. At time t, The first leaky cable The slot reaches the receiving antenna. The Loss path distance, This represents the LoS path channel impulse response of the m-th gap in the leaky cable;

[0030] in, and Let be the coordinates of the m-th gap between the receiving antenna q and the leaky cable p, respectively. and These refer to the spacing between the leaky cables at the transmitting end and the spacing between the antennas at the receiving end. and These are the transmitter and receiver heights, The angle of the receiving antenna array. For the period of leakage cable gap; At time t, the leaking cable No. The slot reaches the receiving antenna. The normalized amplitude value of the Loss path channel impulse response, derived above, is calculated as follows:

[0031] In the above formula, At time t, the receiving antenna With leaky cables No. The angle between the line connecting the slots and the axial direction of the leaky cable; This indicates signal amplitude attenuation between adjacent slots inside the leaky cable. Let M be the LoS path distance from the m-th gap in the leaky cable p to the receiving antenna q, where M is the total number of gaps in the leaky cable. At time t, the leaking cable No. The slot reaches the receiving antenna. LoS path Doppler frequency offset; Let the direction vector of the Loss path be _____. For velocity vectors, Let LoS be the path distance from the m-th gap in the leaky cable p to the receiving antenna q. 2) Superimpose the channel impulse responses of the slot-equivalent magnetic dipole antenna in the NLoS path component to obtain the complete NLoS path channel impulse response of the leaky cable in the operation scenario of the vacuum maglev train. The method for calculating the channel impulse response of a single magnetic dipole antenna in the NLoS radial component is as follows: (twenty three)

[0032] in and At time t, the leaking cable No. The slot reaches the scattering point Scattering points Reaching the receiving antenna NL0S path distance, For leaky cables to receiving antenna Total energy of the link Here, M is the Rice K-factor of the link, M is the total number of leaky cable gaps, and N is the total number of scattering elements. This represents the propagation constant inside a leaky cable. Represents the propagation constant within the pipe. For the initial phase, This represents the NLoS path channel impulse response of the m-th gap in the leaky cable via the scatterer n.

[0033] As can be seen from the technical solutions provided by the embodiments of the present invention above, the embodiments of the present invention treat the leaky cable gap as equivalent to a magnetic dipole antenna, analyze the electric field distribution of the magnetic dipole antenna in the leaky cable in a confined narrow pipe, and construct the complete electric field distribution under the operation scenario of a vacuum maglev train by superimposing multiple gaps, and derive the expression form of the complete leaky cable channel impulse response under the operation scenario of a vacuum maglev train.

[0034] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and will become apparent from the description or may be learned by practice of the invention. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 A schematic diagram illustrating the implementation principle of a method for analyzing the channel characteristics of a leaky cable in a vacuum maglev train based on multi-source geometry, provided in an embodiment of the present invention. Figure 2 The flowchart illustrates a method for analyzing the channel characteristics of a leaky cable in a vacuum maglev train based on multi-source geometry, as provided in this embodiment of the invention. Detailed Implementation

[0037] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0038] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein can include wireless connections or couplings. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0039] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0040] To facilitate understanding of the embodiments of the present invention, the following will provide further explanation and description with reference to the accompanying drawings and several specific embodiments. These embodiments do not constitute a limitation on the embodiments of the present invention.

[0041] Leaky cable: A coaxial communication cable with periodically slotted outer conductor, possessing both electromagnetic wave transmission and radiation capabilities. Multi-source geometry: By treating the slots in the leaky cable as equivalent to magnetic dipole antennas, and using geometry-based random channel modeling for each magnetic dipole antenna and superimposing them, the entire leaky cable channel is modeled.

[0042] This invention designs a method for modeling the channel of a leaky cable in a vacuum maglev train based on multi-source geometry. By equating the gaps in the leaky cable with magnetic dipole antennas, and starting from the radio wave propagation mechanism, it analyzes the electric field distribution of the magnetic dipole antenna in the leaky cable within a confined, narrow pipe. Through the superposition of multiple gaps, a complete electric field distribution under the operating scenario of the vacuum maglev train is constructed. Based on the above electric field distribution, this invention employs a geometry-based random channel modeling method to analyze the channel impulse response expressions of a single magnetic dipole antenna under LoS (Line of Sight) and NLoS (Non-Line of Sight) conditions. By superimposing the impulse responses of multiple sources, the expression form of the complete leaky cable channel impulse response under the operating scenario of the vacuum maglev train is further derived. LoS refers to the unobstructed direct propagation path between the transmitter and receiver, while NLoS refers to the indirect propagation path between the transmitter and receiver through reflection from scatterers.

[0043] Based on the above channel impulse response expression and combined with the scattering point distribution function of the confined narrow pipe wall, the space-time correlation function expressions of the LoS path and NLoS path of the complete leaky cable channel are derived, and the non-stationary channel characteristics in the scenario of leaky cable in vacuum maglev train are analyzed.

[0044] The implementation principle of the method for analyzing the channel characteristics of leaky cables in vacuum maglev trains based on multi-source geometry provided in this invention is as follows: Figure 1 As shown, the specific processing flow is as follows: Figure 2 As shown, the processing steps include the following: Step S10: Treat the leaky cable gap of the vacuum maglev train as an equivalent magnetic dipole antenna, and analyze the characteristics of the radiated electric field distribution of the magnetic dipole antenna in the leaky cable gap within a confined narrow pipe, starting from the electromagnetic wave propagation mechanism.

[0045] Step S20: Based on the electric field distribution characteristics of the leaky cable gap of the above magnetic dipole antenna, obtain the LoS path and NLoS path of the electric field radiation of the leaky cable gap.

[0046] Step S30: Model the multi-source channel of the leaky cable based on the above LoS and NLoS radiation paths, and obtain the channel impulse response expression of a single magnetic dipole antenna under LoS and NLoS conditions.

[0047] Step S40: Based on the channel impulse response expression of a single magnetic dipole antenna in LoS and NLoS conditions, the multi-source channel impulse response is superimposed to derive the expression form of the complete leaky cable channel impulse response in the operation scenario of vacuum maglev train.

[0048] Step S10 above includes: The internal electric field analysis of the leaky cable of the vacuum maglev train in this embodiment of the invention is as follows: According to the slotting method of the leaky cable, it is mainly divided into vertical slotting, inclined slotting, and symmetrical inclined slotting. According to the electrical characteristics of the leaky cable, the polarization mode of the vertical slotted leaky cable is horizontal polarization, and the polarization mode of the inclined slotted and symmetrical inclined slotted leaky cables is vertical polarization.

[0049] This invention studies the vertically slotted leaky cable in the vacuum tube scenario of a vacuum maglev train. The total electric field intensity of the vertically slotted leaky cable can be expressed as the vector superposition of the axial and circumferential electric field intensity components along the cable. The vertically slotted leaky cable only exhibits an electric field along its axial direction. Based on its electromagnetic field radiation pattern, the electric field intensity distribution at the slot opening of the leaky cable shows many similarities to that of a half-wave magnetic dipole antenna; therefore, the slot opening of the leaky cable can be considered equivalent to a magnetic dipole antenna.

[0050] This invention equates the gaps in the leaky cable of a vacuum maglev train to a magnetic dipole antenna. Based on the electrical characteristics of the vertically slotted leaky cable and the electric field distribution of the equivalent magnetic dipole antenna, the electric field strength of a single slot in the leaky cable is expressed as follows:

[0051] in The electric field strength at point m in the leaky cable tray opening is given. It represents the distance from the opening of the leaky cable trench to the position in the electromagnetic field radiated from the trench opening. This indicates the angle between the line connecting this location to the slot opening and the axial direction of the leaky cable in the electromagnetic field. Let be the propagation constant of electromagnetic waves in free space, which can be expressed as:

[0052] in The wavelength of electromagnetic waves.

[0053] There are also losses during the transmission of electrical signals inside the leaky cable. Let the electric field strength at the feed end be... Then the first The electric field strength at each slot is:

[0054] In the formula, Indicates the leakage cable number The attenuation coefficient of the signal from each slot to the signal feed end can be specifically expressed as:

[0055] in, For the first The attenuation of the electric field intensity amplitude at each slot, For the first The phase change of the electric field intensity at each slot. Based on the electrical characteristics of the leaky cable, the power attenuation constant inside the leaky cable is... [dB / 100m], the amplitude attenuation and phase change of the signal at the m-th slot can be expressed as:

[0056] in, and These represent the signal amplitude attenuation and signal phase change between adjacent slots inside the leaky cable, respectively. For the slot cycle, The propagation constant inside a leaky cable can be expressed as:

[0057] in, It is the relative permittivity of the medium inside the leaking cable.

[0058] Step S20 above includes: analysis of the electric field along the radiation path of the leaky cable gap.

[0059] In the vacuum tube scenario, the electromagnetic field radiation path of the leaky cable can be divided into the LosS path and the NLoS path. Consider that in the simulation scenario, the leaky cable has M slots, and the vacuum tube wall has N scatterers. The electric field strength at the receiving end can be denoted as:

[0060] 1) LoS path radiation path

[0061] The electric field strength along the LoS path from the m-th slot of the leaky cable to the receiving antenna on the vacuum maglev train can be expressed as:

[0062] in, To reduce the electric field strength at the cable tray opening, This represents the LoS path distance from the m-th slot of the leaky cable to the electromagnetic field radiated from the slot. This indicates the angle between the line connecting the receiving antenna position to the m-th slot and the axial direction of the leaky cable.

[0063] Based on the signal attenuation characteristics within the leaky cable, it can be obtained that...

[0064] Substituting the above equation, we can obtain the electric field intensity of the LoS path as follows:

[0065] 2) NLoS path radiation path

[0066] The radiation field of the m-th slot of the leaky cable is reflected or scattered by a reflector or scatterer. The expression for the NLoS electric field intensity at the receiving antenna is:

[0067] in scattering body The expression for the electric field intensity at that location, Let be the distance from the scatterer to the receiving antenna. Based on the derivation process of the LoS radius electric field intensity, the scatterer... The electric field strength at that point can be calculated as follows:

[0068] in The distance from the slot opening m to the scatterer. Substituting the values, we get:

[0069] in and From slot m to the scatterer scatterer Distance to the receiving antenna scattering body The angle between the line connecting the slot m and the axial direction of the leaky cable.

[0070] Similar to the Loss of Signal (LoS) case, the signal attenuation characteristics within the leaky cable can be incorporated to obtain...

[0071] Step S30 above includes: Multi-source channel modeling of leaky cables In a vacuum tube channel environment, taking the channel from the p-th of the leaky cable to the q-th of the receiving antenna as an example, its channel impulse response can be expressed as:

[0072] 1) LoS path component

[0073] In the above formula, For leaky cables to receiving antenna Total energy of the link This is the Rice K-factor of the link. At time t, The first leaky cable The slot reaches the receiving antenna. The Loss distance.

[0074] At time t, the leaking cable No. The slot reaches the receiving antenna. The normalized amplitude value of the Loss path channel impulse response. Based on the above derivation, its calculation is as follows:

[0075] In the above formula, At time t, the receiving antenna With leaky cables No. The angle between the line connecting the slots and the axial direction of the leaky cable.

[0076] At time t, the leaking cable No. The slot reaches the receiving antenna. The LoS path Doppler frequency offset.

[0077]

[0078] 2) NLoS path component: (twenty three)

[0079] in and At time t, the leaking cable No. The slot reaches the scattering point Scattering points Reaching the receiving antenna The NL0S path distance.

[0080] At time t, the leaking cable No. The slot reaches the receiving antenna. The normalized amplitude value of the NLoS path channel impulse response. Based on the above derivation, its calculation is as follows:

[0081] In the above formula, At time t, the scatterer With leaky cables The angle between the line connecting the m-th slot and the axial direction of the leaky cable.

[0082] At time t, the leaking cable No. The NLoS path Doppler frequency offset of the slot reaches the receiving antenna.

[0083]

[0084] The coordinates of the scattering point are determined by the horizontal and vertical angles of the transmitting and receiving ends. Based on geometric relationships, the following coordinate representation of the scattering point can be derived:

[0085] (4) Correlation analysis

[0086] Correlation analysis is conducted to evaluate channel performance after obtaining the CIR using the aforementioned channel modeling method. The correlation results are used to evaluate the characteristics and non-stationarity of the wireless channel in this scenario, serving as a verification and comparison of the channel modeling results.

[0087] and To conduct correlation analysis, the channel impulse response from the first leaky cable to the first receiving antenna and the channel impulse response from the second leaky cable to the second receiving antenna are used as examples to derive the channel correlation function. This can also be extended to other channels.

[0088] By derivation and The correlation function expression is as follows. To simplify the theoretical derivation of the channel correlation function, only the correlation between the corresponding slots of the two leaky cables is considered. Its space-time correlation function can be expressed as follows:

[0089] Here we assume Based on the above analysis, the spatiotemporal correlation function between the LoS path and the NLoS path can be obtained.

[0090] 1) LoS component correlation function

[0091] 2) LoS component correlation function

[0092] Considering the scattering distribution in the vacuum pipe, we will refer to the von Mises distribution for description, which is suitable for describing the local scattering distribution (AOA) in an isotropic scattering environment. We assume that the diffuse reflection component follows a von Mises distribution. and It is the distribution of the elevation and horizontal angles at the receiving end:

[0093] Cosine distribution:

[0094] in It is the average angle. It is the absolute value of the maximum elevation angle.

[0095] Therefore, the NLoS related functions can be further expressed as:

[0096] In the formula

[0097] In summary, the embodiments of the present invention reduce the computational complexity of electric field distribution in a confined, narrow pipe by treating each leaking cable gap in the vacuum maglev train operation scenario as an equivalent magnetic dipole antenna and analyzing the radiation characteristics of each magnetic dipole antenna.

[0098] Based on the radiated electric field intensity of the magnetic dipole antenna, the impulse response expression of the complete vacuum maglev train channel was derived, and the space-time correlation function expression was further derived by combining the scattering point distribution characteristics of the vacuum pipe. While ensuring the modeling accuracy, the computational complexity of channel modeling was further reduced.

[0099] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of one embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing the present invention.

[0100] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that the present invention can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of the present invention.

[0101] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for apparatus or system embodiments, since they are basically similar to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. The apparatus and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0102] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for analyzing the channel characteristics of leaky cables in vacuum maglev trains based on multi-source geometry, characterized in that, include: The leaky cable gap of the vacuum maglev train is equivalent to a magnetic dipole antenna. Starting from the electromagnetic wave propagation mechanism, the characteristics of the radiated electric field distribution of the magnetic dipole antenna in the leaky cable gap in the confined narrow pipe are analyzed. Based on the electric field distribution characteristics of the leaky cable gap of the magnetic dipole antenna, the LoS-radiated electric field intensity and NLoS-radiated electric field intensity of the leaky cable gap are obtained. The multi-source channel of the leaky cable is modeled based on the LoS and NLoS electric field strengths. The channel impulse response expressions of a single magnetic dipole antenna under LoS and NLoS conditions are obtained. The channel impulse responses of the slot equivalent magnetic dipole antenna under LoS and NLoS conditions are superimposed to obtain the complete channel impulse response expression form of the leaky cable under the operation scenario of a vacuum maglev train.

2. The method according to claim 1, characterized in that, The method of equating the leaky cable gap of a vacuum maglev train with a magnetic dipole antenna, and analyzing the radiated electric field distribution characteristics of the magnetic dipole antenna in the leaky cable gap within a confined, narrow pipe based on the radio wave propagation mechanism, includes: The slotting methods of the leakage cable of the vacuum maglev train are divided into vertical slotting, inclined slotting and symmetrical inclined slotting. The polarization mode of the vertical slotted leakage cable is horizontal polarization, while the polarization mode of the inclined slotted and symmetrical inclined slotted leakage cables is vertical polarization. The total electric field intensity of the vertical slotted leakage cable is expressed as the vector superposition of the electric field intensity components along the axial direction and the circumferential direction along the leakage cable. The gaps in the leaky cable of the vacuum maglev train are equivalent to magnetic dipole antennas, and the electric field strength of a single slot in the leaky cable is expressed as: in The electric field strength at point m in the leaky cable tray opening is given. This represents the distance from the opening of the leaky cable tray to the position within the electromagnetic field radiated from the tray opening. This indicates the angle between the line connecting this location to the slot opening and the axial direction of the leaky cable in the electromagnetic field. Let be the propagation constant of electromagnetic waves in free space, expressed as: in The wavelength of electromagnetic waves; There are also losses during the transmission of electrical signals inside the leaky cable. Let the electric field strength at the feed end be... Then the first The electric field strength at each slot is: In the formula, Indicates the leakage cable number The attenuation coefficient of the signal from each slot to the signal feed end is expressed as: in, For the first The attenuation of the electric field intensity amplitude at each slot, For the first The phase change of the electric field intensity at each slot, based on the electrical characteristics of the leaky cable, the power attenuation constant inside the leaky cable is... The amplitude attenuation and phase change of the signal at the m-th slot are expressed as: in, and These represent the signal amplitude attenuation and signal phase change between adjacent slots inside the leaky cable, respectively. For the slot cycle, The propagation constant inside a leaky cable is expressed as: in, It is the relative permittivity of the medium inside the leaking cable.

3. The method according to claim 2, characterized in that, The method for obtaining the LoS-radiated electric field intensity and NLoS-radiated electric field intensity of the leaky cable gap based on the magnetic dipole antenna includes: The electromagnetic field radiation path of the leaky cable of the vacuum maglev train is divided into LoS ​​path and NLoS path. The leaky cable has M slots, and the vacuum tube wall has N scatterers. The electric field strength at the receiving end of the leaky cable is expressed as: in, and These are the electric field levels along the LoS and NLoS paths of the receiving antenna, respectively. The electric field strength along the LoS path from the m-th slot of the leaky cable to the receiving antenna on the vacuum maglev train is expressed as: in, To reduce the electric field strength at the cable tray opening, This represents the LoS path distance from the m-th slot of the leaky cable to the slot in the radiated electromagnetic field. This indicates the angle between the line connecting the receiving antenna position to the m-th slot and the axial direction of the leaky cable. Based on the signal attenuation characteristics within a leaky cable: Substituting equation (10) into equation (9), we obtain the electric field intensity of the LoS radius as follows: in, The electric field strength at the feed end, and These represent the signal amplitude attenuation and signal phase change at the m-th slot of the leaky cable, respectively. Let L be the distance from the m-th slot of the leaky cable to the receiving point (LoS). This indicates the angle between the line connecting the receiving antenna position to the m-th slot and the axial direction of the leaky cable. The radiation field at the m-th slot of the leaky cable is reflected or scattered by a reflector or scatterer. The expression for the NLoS electric field strength reaching the receiving antenna is: in scattering body The expression for the electric field intensity at that location, Let be the distance from the scatterer to the receiving antenna. The derivation process is based on the LoS radius electric field strength. The calculation formula is as follows: in The distance from the slot opening m to the scatterer. Substituting equation (13) into equation (12), we get: in and From slot m to the scatterer scatterer Distance to the receiving antenna scattering body The angle between the line connecting the slot m and the axial direction of the leaky cable; Substituting equation (10) into equation (14), we get: in, The electric field strength at the feed end, This indicates signal amplitude attenuation between adjacent slots inside the leaky cable. For the slot cycle, This represents the propagation constant inside a leaky cable. Represents the propagation constant within the pipe. and From slot m to the scatterer scatterer Distance to the receiving antenna scattering body The angle between the line connecting the slot m and the axial direction of the leaky cable.

4. The method according to claim 3, characterized in that, The method described above involves modeling the multi-source channel of the leaky cable based on the LoS and NLoS radial electric field strengths, obtaining the channel impulse response expressions of a single magnetic dipole antenna under LoS and NLoS conditions, and superimposing the channel impulse responses of the slot-equivalent magnetic dipole antenna under LoS and NLoS conditions to obtain the complete channel impulse response expression form of the leaky cable in the operation scenario of a vacuum maglev train, including: In a vacuum tube channel environment, taking the channel from the p-th of the leaky cable to the q-th of the receiving antenna as an example, the channel impulse response of a single magnetic dipole antenna is expressed as: 1) Superimpose the channel impulse responses of the slot-equivalent magnetic dipole antenna in the LoS path component to obtain the complete LoS path channel impulse response of the leaky cable in the operation scenario of a vacuum maglev train. : In the above formula, For leaky cables to receiving antenna Total energy of the link This is the Rice K-factor of the link. At time t, The first leaky cable The slot reaches the receiving antenna. The Loss path distance, This represents the LoS path channel impulse response of the m-th gap in the leaky cable; in, and Let be the coordinates of the m-th gap between the receiving antenna q and the leaky cable p, respectively. and These refer to the spacing between the leaky cables at the transmitting end and the spacing between the antennas at the receiving end. and These are the transmitter and receiver heights, The angle of the receiving antenna array. For the period of leakage cable gaps; At time t, the leaking cable No. The slot reaches the receiving antenna. The normalized amplitude value of the Loss path channel impulse response, derived above, is calculated as follows: In the above formula, At time t, the receiving antenna With leaky cables No. The angle between the line connecting the slots and the axial direction of the leaky cable; This indicates signal amplitude attenuation between adjacent slots inside the leaky cable. Let M be the LoS path distance from the m-th gap in the leaky cable p to the receiving antenna q, where M is the total number of gaps in the leaky cable. At time t, the leaking cable No. The slot reaches the receiving antenna. LoS path Doppler frequency offset; Let the direction vector of the Loss path be . For velocity vector, Let LoS be the path distance from the m-th gap in the leaky cable p to the receiving antenna q. 2) Superimpose the channel impulse responses of the slot-equivalent magnetic dipole antenna in the NLoS path component to obtain the complete NLoS path channel impulse response of the leaky cable in the operation scenario of the vacuum maglev train. The method for calculating the channel impulse response of a single magnetic dipole antenna in the NLoS radial component is as follows: （23） in and At time t, the leaking cable No. The slot reaches the scattering point Scattering points Reaching the receiving antenna NL0S path distance, For leaky cables to receiving antenna Total energy of the link Here, M is the Rice K-factor of the link, M is the total number of leaky cable gaps, and N is the total number of scattering elements. This represents the propagation constant inside a leaky cable. Represents the propagation constant within the pipe. For the initial phase, This represents the NLoS path channel impulse response of the m-th gap in the leaky cable via the scatterer n.

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