Multidirectional narrow-beam directional leaky coaxial cable

Abstract

The invention relates to a multidirectional narrow-beam directional leaky coaxial cable, which comprises a cable main body, a broadband signal generator and a signal receiver, and is characterized in that the cable main body comprises a plurality of reflectors, and the reflectors are connected with an outer conductor, are distributed at equal intervals along the axial direction of the cable main body, and are configured to generate resonance when receiving a target frequency signal; the reflectivity is larger than the lower limit of a target threshold range, the corresponding target frequencies have difference values when the reflectors generate resonance, the broadband signal generator is connected with the cable main body and can emit signals covering the resonance frequencies of the reflectors, and the signal receiver is connected with the cable main body and receives signals entering the cable main body in real time and records spectral characteristics. According to the technical scheme, through cooperative work of the multiple reflectors, the broadband signal generator and the signal receiver, accurate analysis of signal frequency characteristics of the leaky coaxial cable is achieved, particularly, distributed fault points can be positioned in a high-precision mode in a complex environment, and fault detection efficiency and accuracy are improved.

Description

Technical Field

[0001] The invention relates to a leaky cable, in particular to a multi-directional narrow beam directional leaky cable. Background Art

[0002] Leaky cables are widely used in long-distance wireless signal coverage scenarios such as tunnels, subways, and along railways. These environments usually have complex installation conditions and high-demand signal transmission requirements. Due to the characteristics of leaky cables, they can provide continuous and uniform signal coverage for wireless communications in closed environments such as tunnels and subways. Leaky cables not only have advantages in high-frequency signal transmission, but also have the ability to adapt to complex environments, which makes them widely used in special places such as high-speed railways and underground pipelines. However, the complexity and concealment of these environments pose high challenges to the installation, maintenance and fault detection of leaky cables. In these environments, leaky cables are usually installed in a concealed state, making them difficult to observe and repair directly. In addition, due to the influence of harsh environmental factors such as humidity and temperature, the faults of leaky cables are often more concealed and may spread to the entire system with the infiltration of water vapor.

[0003] The current leaky cable design mostly adopts the principle of distributed radiation, radiating signals through gaps or holes on the outer conductor, and using the continuous leakage of signals on the surface of the leaky cable to achieve signal coverage. Since its signal leakage is distributed, the leaky cable can achieve wide signal coverage through long-distance transmission. The commonly used detection methods for leaky cables include standing wave ratio test and time domain reflectometer. The former is mainly used to detect the integrity of the leaky cable, and the latter can locate impedance discontinuities in the cable.

[0004] However, since leaky cable faults may be distributed (for example, the expansion of fault points caused by the entry of water vapor), traditional fault detection technologies (such as standing wave ratio test, time domain reflectometry, etc.) cannot accurately locate multi-point faults, and lack comprehensive monitoring methods for leaky cable signals under complex environmental conditions. Specifically, the standing wave ratio test is mainly used to detect the overall performance of the leaky cable, but cannot provide high-precision fault point location; although the time domain reflectometry can locate impedance discontinuities in the cable, its applicability in leaky cables, which have distributed radiation characteristics, is limited, and it lacks sufficient accuracy and sensitivity for the detection and reflection characteristics of high-frequency signals. This makes it urgent to improve the technical means of leaky cable fault location to improve the efficiency and accuracy of fault detection. Therefore, it is necessary to propose a new directional narrow beam directional leaky cable to solve the above problems. Summary of the invention

[0005] The object of the present invention is to provide a multi-directional narrow-beam directional leaky cable which is optimized in design based on a traditional leaky cable to improve the fault diagnosis and positioning capabilities.

[0006] The technical solution adopted by the present invention to solve the above problems is: a multi-directional narrow beam directional leaky cable, comprising: The cable body includes: Inner conductor; An insulating layer is coaxially sleeved outside the inner conductor; An outer conductor, coaxially sleeved outside the inner conductor; A sheath, covering the outer surface of the outer conductor; A plurality of reflectors are connected to the outer conductor, and each of the reflectors is evenly spaced along the axial direction of the cable body. The reflectors are configured to generate resonance when receiving a signal of a target frequency, so that the reflectivity of the reflector to the signal of the target frequency is greater than the lower limit of the target threshold range, and there is a difference in the target frequency corresponding to each of the reflectors when the resonance occurs.

[0007] Wherein, the leaky cable includes a detection state for detecting its own fault point. When the leaky cable is in the detection state, the two ends of the cable body are respectively connected to a wideband signal generator and a signal receiver. The wideband signal generator sequentially transmits signals that can cover the resonant frequency of each reflector, and the signal receiver sequentially receives each signal entering the cable body and records the spectrum characteristics of the signal.

[0008] Preferably, the outer conductor surface is provided with two rows of orthogonally distributed slots along its own axial direction, and the angle between the centers of the two rows of slots and the axis of the inner conductor is at most 90°, and the slots form a conductive tube cavity with a gradually shrinking size along the direction away from the axis of the inner conductor.

[0009] Preferably, the reflector comprises: substrate; A rectangular copper foil is arranged on one side of the substrate; The copper layer is arranged on a side of the substrate away from the rectangular copper foil, and the copper layer is electrically connected to the outer conductor.

[0010] Preferably, a connecting groove is provided on the surface of the sheath, the reflector is arranged at the connecting groove, the side of the rectangular copper foil facing away from the substrate is arranged toward the outer conductor, and a gap is left between the side of the rectangular copper foil facing the outer conductor and the outer conductor.

[0011] Preferably, an orthographic projection area of ​​the copper layer on the side surface of the substrate is smaller than an orthographic projection area of ​​the rectangular copper foil on the side surface of the substrate.

[0012] Preferably, the reflector is arranged in the sheath so that the reflector bears the pressure applied by the sheath and directed toward the axis of the inner conductor, and the copper layer is connected to the outer conductor through a conductive adhesive.

[0013] Preferably, a coating layer is provided on the outer surface of the outer conductor, and the inner side of the coating layer abuts against the reflector so as to apply a coating force directed toward the axis of the inner conductor to the reflector.

[0014] Preferably, the rectangular copper foil covers at least one of the slots.

[0015] Preferably, the length direction of the rectangular copper foil is parallel to the axial direction of the leakage cable.

[0016] Preferably, the leaky cable comprises a first end and a second end, the direction from the first end to the second end is defined as a first direction, the reflectors are arranged equidistantly along the first direction to divide the leaky cable into a plurality of sections, the reflectors correspond one-to-one to each section of the leaky cable, and the corresponding target frequencies of the reflectors when resonating increase or decrease successively along the first direction.

[0017] The beneficial effects of each embodiment of the present invention are as follows: Due to the adoption of a technical solution including multiple reflectors, a wideband signal generator and a signal receiver, the reflector can achieve high-precision signal reflection by resonating the target frequency signal, and the wideband signal generator can cover the resonant frequency of multiple reflectors, so it can provide a more accurate frequency characteristic analysis during the transmission of the leaky cable signal. This design effectively solves the problem that the existing technology cannot locate distributed fault points, especially the accurate detection of high-frequency signals and the location of multi-point faults in complex environments. In addition, through the spectrum characteristics recorded by the signal receiver, a more comprehensive and dynamic signal monitoring can be provided, further improving the efficiency and accuracy of leaky cable fault detection. In this way, high-precision positioning and real-time monitoring of leaky cable faults are achieved, which effectively improves the efficiency of troubleshooting and ensures the stability and reliability of leaky cable signals in complex installation environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic structural diagram of a leaky cable in one embodiment of the present invention is shown.

[0019] Figure 2 A schematic radial cross-sectional view of a leaky cable is shown when a rectangular copper foil is arranged toward the inner conductor in an embodiment of the present invention.

[0020] Figure 3 A schematic radial cross-sectional view of a leaky cable is shown when a rectangular copper foil is arranged away from the inner conductor in an embodiment of the present invention.

[0021] Figure 4 A schematic radial cross-sectional view of a leaky cable is shown when a rectangular copper foil is arranged away from the inner conductor and a coating layer is provided between the sheath and the outer conductor in an embodiment of the present invention.

[0022] Figure 5 The flowchart of the method for detecting a leaky cable in one embodiment of the present invention is shown.

[0023] Among them: 10, cable body; 110, inner conductor; 120, insulation layer; 130, outer conductor; 131, slot; 140, sheath; 141, connecting groove; 150, covering layer; 20, reflector; 210, substrate; 220, rectangular copper foil; 230, copper layer; 30, copper column. DETAILED DESCRIPTION

[0024] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0025] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description created by the present application, unless otherwise specified, "multiple" means two or more.

[0026] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0027] See also Figures 1 to 3 A preferred embodiment of the present application proposes a multi-directional narrow beam directional leaky cable for signal transmission in a narrow and long channel. The target scenes of the leaky cable include tunnels, subways, etc., and are particularly suitable for scenes such as curved sections of tunnels (requiring multi-directional coverage) and subway platforms (requiring directional coverage) to ensure that the signal is evenly distributed in complex paths.

[0028] A multi-directional narrow beam directional leaky cable includes a cable body 10. The cable body 10 includes an inner conductor 110, an insulating layer 120, an outer conductor 130 and a sheath 140, wherein the insulating layer 120 is coaxially sleeved outside the inner conductor 110, the outer conductor 130 is coaxially sleeved outside the inner conductor 110, and the sheath 140 is wrapped around the outer surface of the outer conductor 130.

[0029] Specifically, the inner conductor 110 may be made of copper-clad aluminum material, which may be high-purity oxygen-free copper in a specific manner, and is used to transmit high-frequency signals.

[0030] The insulating layer 120 is coaxially coated on the outside of the inner conductor 110, and can be made of a material with a lower dielectric constant, which can be specifically made of foamed polyethylene (dielectric constant ε=1.5-1.6) to reduce signal loss during transmission, which can be specifically reflected as attenuation <0.1dB / m@28GHz.

[0031] The outer conductor 130 may be made of a corrugated copper tube, and two rows of rectangular slots 131 are arranged in an axial direction on the surface, and the spacing between each row of slots 131 is half a wavelength, where the wavelength is the wavelength corresponding to the signal to be transmitted by the leaky cable. The angle between the center of the two rows of slots 131 and the axis of the inner conductor 110 is at most 90° to form a multi-directional radiation beam, wherein the two rows of orthogonal slots 131 form independent radiation beams in the horizontal and vertical directions to achieve multi-directional coverage (such as bidirectional radiation in the tunnel cross section).

[0032] In some embodiments, the slot 131 forms a conductive tube cavity with a gradually shrinking size along the direction away from the axial center of the inner conductor 110, which is specifically embodied as an inverted trumpet-shaped slot 131 or an inverted conical slot 131. The tapered structure of the slot 131 constrains the electromagnetic wave radiation angle, and a narrow beam radiation can be formed at the closed end to reduce signal leakage. Furthermore, the inner wall of the slot 131 can be silver-plated (thickness 0.1 μm) to reduce surface resistance and improve high-frequency signal transmission efficiency.

[0033] The sheath 140 may be made of polyethylene materials, such as low-density polyethylene materials and flame-retardant polyvinyl chloride materials. The sheath 140 wraps around the outside of the outer conductor 130 and has waterproof, flame-retardant and UV-resistant properties.

[0034] In order to quickly determine the specific location of the fault point on the leaky cable that is damaged and invaded by water vapor in scenes such as tunnels, it is necessary to provide a new multi-directional narrow beam directional leaky cable suitable for quickly locating the damaged fault point. The cable body 10 also includes a plurality of reflectors 20. In addition, the leaky cable includes a detection state for detecting its own fault point. When the leaky cable is in the detection state, the two ends of the cable body 10 are respectively connected to a wideband signal generator and a signal receiver. The wideband signal generator sequentially transmits signals that can cover the resonant frequency of each of the reflectors 20. The signal receiver sequentially receives each signal entering the cable body 10 and records the spectrum characteristics of the signal. Among them, the plurality of reflectors 20 are all connected to the outer conductor 130, and each reflector 20 is equidistantly distributed along the axial direction of the cable body 10. The reflectors 20 are configured to generate resonance when receiving a signal of a target frequency, so that the reflectivity of the reflector 20 to the signal of the target frequency is greater than the lower limit of the target threshold range, and there is a difference in the corresponding target frequency when each of the reflectors 20 generates resonance.

[0035] Specific: The reflector 20 can be specifically embodied as a patch antenna and a slot antenna. Taking the patch antenna as an example, metal patches of different lengths are designed on a printed circuit board (PCB). The metal patches of different lengths on each circuit board correspond to specific resonant frequencies. The reflector 20 can be manufactured into resonant units of different sizes through standard PCB processes, which is low-cost and easy to mass-produce.

[0036] In some embodiments, the reflector 20 is composed of a substrate 210, a rectangular copper foil 220, and a copper layer 230. Figure 2 or Figure 3 As shown, the rectangular copper foil 220 is arranged on one side of the substrate 210, and the copper layer 230 is installed on the side of the substrate 210 away from the rectangular copper foil 220, and the copper layer 230 is also electrically connected to the outer conductor 130. The reflector 20 can be specifically manufactured using a standard PCB process to manufacture an epoxy resin substrate 210, with copper cladding on both sides, and the rectangular copper foil 220 is etched out on the top layer by chemical or engraving machine, and the bottom copper layer 230 is retained as a grounding plate.

[0037] The rectangular copper foil 220 is a resonant unit. The copper layer 230 is a complete surface layer, which can be connected to the outer conductor 130 by bonding, or connected to the outer conductor 130 through a conductive member. The substrate 210 can be made of epoxy resin, and its size must be compatible with the rectangular copper foil 220 and the copper layer 230. It should be noted that the size of the rectangular copper foil 220 is the key to achieving frequency differentiation in this application, which is related to whether there will be missed or misjudged faults during fault detection. The length of the rectangular copper foil 220 is what determines the resonant frequency Key parameters of rectangular copper foil 220 It can be obtained by the following formula: .

[0038] in, , , 0.95 is the correction factor considering the edge effect.

[0039] The design of the rectangular copper foil 220 is based on half-wavelength resonance and resonant reflection, wherein half-wavelength resonance means that when the length of the rectangular copper foil 220 in the reflector 20 is approximately half a wavelength, the current forms standing waves at both ends of the length direction of the rectangular copper foil 220 to achieve maximum radiation efficiency. Resonant reflection means that when the frequency of the incident electromagnetic wave matches the resonant frequency of the rectangular copper foil 220, the rectangular copper foil 220 absorbs energy and reflects efficiently, and injects the reflected signal into the leaky cable through the slot 131 on the outer conductor 130, and, at this time, if the reflectivity of the reflector 20 to the signal of the target frequency (the frequency of the incident electromagnetic wave) is greater than the lower limit of the target threshold range, the target threshold range is the peak value ± the allowable deviation value recorded on the spectrum by the signal receiver when the leaky cable receives the reflected signal of the reflector 20, wherein the allowable deviation value can be obtained through repeated tests. The resonant frequency means that each reflector 20 is designed to be at a specific frequency (such as ), which means that when the frequency of the incident electromagnetic wave is equal to the resonant frequency of the reflector 20, the reflector 20 will show the maximum reflection efficiency. The edge effect correction means that the effective length of the actual rectangular copper foil 220 is slightly smaller than the theoretical value and needs to be multiplied by a correction factor of 0.95. It can be understood that when the rectangular copper foil 220 undergoes non-resonant reflection, the reflection efficiency of electromagnetic waves of other frequencies is low.

[0040] In summary, the role of the differentiated design of the rectangular copper foil 220 according to the resonant frequency in this application is to resonate at different frequencies by designing reflectors 20 of different sizes. When a section of the leaky cable fails, the reflected signal of the reflector 20 of this section will attenuate or disappear. By detecting the frequency loss or attenuation of the reflected signal, the corresponding faulty section can be quickly located.

[0041] The size design of the rectangular copper foil 220 can be specifically carried out in the following order: First determine the target frequency band, for example, select 2.4GHz-2.5GHz (Wi-Fi frequency band, for easy testing).

[0042] Then calculate the length of the rectangular copper foil 220: for hour: .

[0043] for hour: .

[0044] For every 50MHz increase in frequency, the length decreases by approximately 0.6mm.

[0045] The purpose of “electrically connecting the copper layer 230 to the outer conductor 130” is to form a complete RF circuit, otherwise the reflection efficiency will be greatly reduced. The specific principle is as follows: First, "the copper layer 230 is electrically connected to the outer conductor 130" provides a current return path. When the rectangular copper foil 220 is excited by electromagnetic waves of the corresponding frequency, an alternating current will be generated on its surface. This current requires a closed loop to effectively transmit energy. The electrical connection between the copper layer 230 and the outer conductor 130 provides a return path for the surface current, forming a closed loop. It can be understood that, assuming that the copper layer 230 is electrically connected to the outer conductor 130, the copper layer 230 is conductive with the outer conductor 130, and the surface current cannot return, resulting in energy dissipation in the form of electromagnetic radiation near the rectangular copper foil 220, and the reflection efficiency is greatly reduced.

[0046] Secondly, to maintain impedance matching, the transmission of RF signals needs to maintain the continuity of characteristic impedance, otherwise it will cause signal reflection (increased standing wave ratio). The connection between the copper layer 230 (ground layer) and the outer conductor 130 ensures the impedance matching between the rectangular copper foil 220 and the outer conductor 130 in the leaky cable, reducing the signal reflection loss caused by impedance mutation. For example: if the ground layer is disconnected, capacitive impedance will be formed between the copper foil and the outer conductor 130 of the leaky cable, causing the signal to be partially reflected at the interface.

[0047] The connection feature of "the copper layer 230 is electrically connected to the outer conductor 130" can enhance the reflection efficiency, suppress the electromagnetic wave divergence loss, improve the signal coupling efficiency and improve the anti-interference ability for the signal reflected after the rectangular copper foil 220 resonates. Specifically: Enhanced reflection efficiency is reflected in the directional reflection of resonant energy. When the rectangular copper foil 220 resonates, the alternating current on its surface will radiate electromagnetic waves, which will induce a current of the same frequency in the copper layer 230 through the capacitive coupling of the substrate 210, and the conduction between the copper layer 230 and the outer conductor 130 ensures that the induced current is transmitted to the outer conductor 130 of the leaky cable through the conductive adhesive, forming a closed loop. When the induced current flows through the slot 131 of the outer conductor 130 of the leaky cable, the current path at the slot 131 is suddenly interrupted (or changed), resulting in a change in current density, thereby exciting electromagnetic waves, which are directionally coupled back to the inside of the leaky cable through the slot 131 of the outer conductor 130 of the leaky cable, rather than diverging into free space.

[0048] Suppressing electromagnetic wave divergence loss is reflected in the constraint of electromagnetic field. After the copper layer 230 is connected to the outer conductor 130, a structure similar to the "mirror effect" is formed, which constrains the electromagnetic field radiated by the rectangular copper foil 220 near the surface of the leaky cable outer conductor 130, reducing the radiation loss of energy to the external space. Its physical mechanism is that the copper layer 230 serves as a reference ground plane, and together with the leaky cable outer conductor 130, it forms a waveguide structure to guide the electromagnetic wave to propagate along the surface of the leaky cable.

[0049] Improving the signal coupling efficiency is reflected in the excitation of the current at the slot 131. The return current transmitted by the copper layer 230 will flow on the surface of the outer conductor 130 of the leaky cable. When the current flows through the slot 131, electromagnetic radiation is generated due to the sudden change of the current path (radiation principle of the slot 131), thereby re-injecting the reflected signal into the leaky cable. According to the formula, the electric field intensity radiated by the slot 131 is proportional to the surface current density: ,in, is the current density on the surface of the outer conductor 130.

[0050] Improving anti-interference capability is reflected in shielding external noise. The connection between the copper layer 230 and the outer conductor 130 forms a continuous metal shielding layer, which can absorb or reflect external interference electromagnetic waves and reduce the impact of noise on the reflected signal.

[0051] Therefore, if the ground connection is cancelled, the reflection efficiency will be greatly reduced, and the system will be susceptible to external interference and cannot meet the high-precision detection requirements. Therefore, the ground design is the core guarantee for the reflector 20 to achieve efficient signal reflection.

[0052] The specific method of "a plurality of reflectors 20 are equally spaced along the axis of the cable body 10" is to divide the leaky cable into sections, which can be set to a section of 10 meters, with a total of 100 sections (total length of 1 km). A reflector 20 is installed on the surface of each section of the leaky cable, and the copper layer 230 of the reflector 20 needs to be electrically connected to the outer conductor 130 of the leaky cable.

[0053] The distribution method of the resonant frequency corresponding to the reflector 20 on each section of the leaky cable can be distributed as follows: Section 1: Corresponding frequency , rectangular copper foil 220 length .

[0054] Section 2: Corresponding frequency , rectangular copper foil 220 length . ... Section 100: Corresponding frequency , rectangular copper foil 220 length .

[0056] in, To correspond to the wavelength of the signal, the resonant frequency of the reflector 20 on each section of the leaky cable is different, and the length L of the rectangular copper foil 220 on the reflector 20 is also different.

[0057] It should be noted that the resonance frequency corresponding to the above-mentioned reflector 20 is only for illustration and cannot be directly used as a real basis.

[0058] The broadband signal generator is a broadband signal source, which can be connected to one end of the leaky cable through a coupler. The output frequency range of the broadband signal generator covers all the resonant frequencies of the reflector 20, and the power is adjustable.

[0059] Furthermore, the wideband signal generator may transmit signals to the leaky cables in sequence according to the resonant frequency of the reflector 20 .

[0060] The signal receiver is a vector network analyzer (VNA) or a portable spectrum analyzer with a built-in high-speed ADC module (sampling rate 10GS / s), which collects the reflected signal spectrum in real time and supports FFT analysis. The signal receiver is connected to the other end of the leaky cable through a coupler. The signal receiver receives and monitors the reflected signal transmitted through the leaky cable in real time. By analyzing the spectrum characteristics of the reflected signal, the system can detect whether there is signal attenuation or abnormal changes in frequency characteristics, thereby determining the status of each section of the leaky cable. For example: if the characteristic frequency of a certain section of the reflected signal does not appear in the detection spectrum, or its peak intensity is lower than the threshold range, it is determined that the section of the leaky cable may be faulty.

[0061] Furthermore, the resonance frequency of the reflector 20 increases or decreases in sequence along the first direction of the leaky cable, so that the section of the leaky cable where the reflector 20 corresponding to the resonance frequency is located can be quickly determined.

[0062] When detecting whether the leaky cable in this embodiment has a damaged electrical water ingress fault, first, the wide-band signal generator and the signal receiver are respectively connected to the two ends of the leaky cable, and then the sweep signal is injected from one end of the leaky cable through the wide-band signal generator, and the reflected signals are received in turn through the signal receiver, and the reflected spectrum of the corresponding signal is recorded.

[0063] Normally, 100 peaks are shown in the spectrum, corresponding to the resonance frequencies of 100 reflectors 20 .

[0064] When a fault occurs, a certain section of reflector 20 fails or the signal strength decreases, and the peak value of the corresponding frequency disappears or decreases (for example, if the 5th section fails, At this time, the frequency peak corresponding to the signal in the reflection spectrum can be used to determine which reflector 20 has a problem with the reflected signal, thereby determining the specific position of the leaky cable section corresponding to the reflector 20 in the entire leaky cable.

[0065] In this embodiment, due to the collaborative work of multiple reflectors 20, broadband signal generators and signal receivers, the present invention can achieve accurate leaky cable fault location and signal monitoring. By matching each reflector 20 with its specific resonant frequency, this technical solution not only solves the problem of inaccurate distributed fault location in the existing leaky cable system, but also provides dynamic and real-time signal spectrum analysis. Compared with traditional standing wave ratio testing and time domain reflectometry, this solution can more efficiently identify and locate multiple faults, especially in complex environments, and can improve the efficiency and accuracy of fault detection, thereby improving the reliability and stability of the leaky cable system.

[0066] Furthermore, the actual leaky cable application scenarios are complex and varied, so the following three installation methods of the reflector 20 and the design methods of the resonant frequency are proposed: In the narrow spacing design, the difference in the resonant frequency of adjacent reflectors 20 is between 5-10MHz, for example, the frequency spacing is 5MHz, the single-segment frequency range is 1.8 to 2.3GHz (a total bandwidth of 500MHz), and when the number of reflectors 20 of a single-segment leaky cable is 100, the coverage length is 1km. When the length of the leaky cable exceeds 1km, for example, the leaky cable is two kilometers, the leaky cable needs two segments, and the frequency is reused twice.

[0067] Every 10m interval corresponds to a unique frequency tag (such as 1.800GHz, 1.805GHz...), and the fault location resolution reaches ±5m (no segment coding is required). A 2km leaky cable only requires 500MHz bandwidth (1.8~2.3GHz), which saves more frequency resources.

[0068] At this time, the signal generator needs to support 5MHz step accuracy (phase noise ≤ -100dBc / Hz@1kHz offset) and the receiver spectrum resolution ≤ 1MHz.

[0069] In the mid-interval design, the difference in resonant frequency between adjacent reflectors 20 is between 10-20MHz. For example, the frequency interval is 20MHz, and the single-segment frequency range is between 1.8 and 2.78GHz (a total bandwidth of 980MHz). When the number of single-segment reflectors 20 is 50 (20MHz interval), the coverage length is 500m. A 2km leaky cable requires 4 segments, and the frequency is reused 4 times.

[0070] At this time, a universal frequency sweep signal source (step accuracy 20MHz, phase noise ≤-90dBc / Hz) and a receiver resolution ≤10MHz are sufficient.

[0071] It should be noted that 4-segment frequency multiplexing requires additional coding (such as segment identification code), which increases the complexity of the signal processing algorithm.

[0072] Mixed spacing design, that is, dynamically adjustable difference. For example, the low frequency band is 1.8 to 2.0 GHz, the spacing is 5 MHz (40 frequencies), and the high frequency band is 2.0 to 3.0 GHz, the spacing is 20 MHz (50 frequencies). At this time, the total bandwidth is 1.2 GHz (1.8 to 3.0 GHz) and can cover a length of 90 reflectors 20×10m=900m. A 2km leaky cable requires 3 sections, and the frequency needs to be reused 3 times.

[0073] Among them, the low frequency band (5MHz interval) is used for high-precision positioning areas (such as tunnel intersections), and the high frequency band (20MHz interval) is used for straight segments. The overall bandwidth requirement is moderate (1.2GHz), and the positioning accuracy is layered (±5m / ±20m). It should be noted that the signal generator frequency band needs to be switched dynamically, and the receiver needs to support multi-band joint analysis.

[0074] In summary, the frequency difference between adjacent reflectors can be selected from 5 to 20 MHz according to the scenario requirements. The 5 MHz interval is suitable for short-distance, high-precision positioning, but requires high spectrum resolution hardware. The 20 MHz interval is suitable for long-distance, low-cost deployment, and the frequency reuse problem is solved through segmented coding. The mixed interval is suitable for balancing performance and resources and requires customized design. The recommended values ​​of the three design schemes are shown in Table 1:

[0075] In some embodiments, the signal receiver records the amplitude-frequency curve of the reflected signal, and can also judge the fault type by the spectrum peak (corresponding to the resonant frequency) and the amplitude mutation (such as the decrease in reflectivity). For example: water vapor penetration, after the sheath 140 is damaged, the moisture causes the dielectric constant of the insulating layer 120 to increase (ε increases from 1.5 to 3.0), and the resonant frequency of the reflector 20 shifts by >150MHz (for example, 2.0GHz drops to 1.85GHz); physical damage, when the slot 131 of the outer conductor 130 is deformed or broken, the reflectivity of the specific reflector 20 drops sharply (from 95% to <80%).

[0076] Furthermore, it is necessary to clearly explain the connection method between the reflector 20 and the cable body 10. However, there are many connection methods between the reflector 20 and the cable body 10. Two of them are taken as examples, which are described as follows: The first connection method, in some embodiments, is Figure 2As shown, a connecting groove 141 is provided on the surface of the sheath 140, the reflector 20 is arranged in the connecting groove 141, the side of the rectangular copper foil 220 away from the substrate 210 is arranged toward the outer conductor 130, and a gap is left between the rectangular copper foil 220 and the outer conductor 130. In addition, after the reflector 20 is installed at the connecting groove 141, the leaky cable is further provided with a local protective layer such as a local sheath 140 (not shown in the figure) on the outside where the reflector 20 is installed, which covers the reflector 20 and the leaky cable as a whole, and restores the closed state at the connecting groove 141 of the leaky cable, thereby ensuring that the internal environment of the leaky cable is isolated from the outside.

[0077] Specifically, the reflector 20 is a substrate 210 with double-sided copper cladding, a rectangular copper foil 220 is located on the side of the substrate 210 close to the leaky cable, and a copper layer 230 is located on the side of the substrate 210 away from the leaky cable. The reflector 20 can be connected to the outer conductor 130 of the leaky cable by drilling holes at the edge or specific position of the substrate 210 and using a conductive material (such as a copper column 30 or conductive glue), wherein the conductive material takes the copper column 30 as an example, one end of which is electrically connected to the copper layer 230 (fixed connection such as welding), and the other end is electrically connected to the outer conductor 130 of the leaky cable (can be connected by conductive glue or a clamping mechanism), thereby achieving conduction between the copper layer 230 and the outer conductor 130 of the leaky cable. It should be noted that the copper column 30 does not contact the edge of the rectangular copper foil 220 when passing through the hole, and an insulating set can be set between the two if necessary to insulate and separate the edge of the copper column 30 from the rectangular copper foil 220.

[0078] Further, if Figure 2 As shown, when the copper pillar 30 is used for connection, it is necessary to ensure that the contact area between the copper pillar 30 and the copper layer 230 and the outer conductor 130 of the leaky cable is large enough to reduce the contact resistance.

[0079] The second connection method, in some other embodiments, is as follows Figure 3 As shown, the orthographic projection area of ​​the copper layer 230 on the side of the substrate 210 is smaller than the orthographic projection area of ​​the rectangular copper foil 220 on the side of the substrate 210. The reflector 20 is disposed in the sheath 140 so that the reflector 20 bears the pressure applied by the sheath 140 toward the axis of the inner conductor 110, and the copper layer 230 is connected to the outer conductor 130 through a conductive adhesive.

[0080] Specifically, the copper layer 230 is fixed to the surface of the outer conductor 130 via conductive adhesive. At this time, the inner wall of the sheath 140 is in contact with one side of the reflector 20 (the side with the rectangular copper foil 220) to apply pressure to the reflector 20 directed to the inner conductor 110, thereby fixing the reflector 20 at a specific position of the outer conductor 130 in cooperation with the conductive adhesive to prevent the reflector 20 from being displaced during transportation or laying. It can be understood that under this connection method, the rectangular copper foil 220 will be located on the side of the substrate 210 away from the leaky cable. At this time, the orthographic projection area of ​​the copper layer 230 on the side of the substrate 210 needs to be smaller than the orthographic projection area of ​​the rectangular copper foil 220 on the side of the substrate 210, thereby preventing the signal emitted from the slot 131 of the outer conductor 130 from being completely shielded by the copper layer 230, so that part of the signal can reach the rectangular copper foil 220, and then the rectangular copper foil 220 is electromagnetically coupled with the transmission signal, and the rectangular copper foil 220 is electromagnetically coupled with the transmission signal. 0 will resonate under the signal of the specific frequency (the resonant frequency of the rectangular copper foil 220), and generate surface alternating current due to the resonance, and the alternating current will cause the copper layer 230 to generate an induced current, which is transmitted to the outer conductor 130 through the conductive glue. After that, the induced current will be conducted along the outer conductor 130 to the slot 131, where it will generate an electromagnetic wave signal of a specific frequency (corresponding to the resonant frequency of the rectangular copper foil 220 on the reflector 20), and the electromagnetic wave signal will be radiated back to the inside of the leaky cable through the slot 131, thereby realizing signal reflection.

[0081] Compared with the first connection method, the second connection method of the reflector 20 and the leaky cable has a weaker reflection signal, but the second connection method can realize integrated packaging, that is, after the outer conductor 130 is sleeved on the insulating layer 120, each reflector 20 can be directly fixed on the surface of the outer conductor 130 through the conductive adhesive, and after the conductive adhesive is cured, a coating layer 150 (without shielding effect) can be formed on the outer surface of the outer conductor 130 by weaving, as shown in the following figure. Figure 4 , the reflector 20 and the outer conductor 130 are covered as one, at this time, the coating layer 150 will exert a covering force on the reflector 20 directed to the inner conductor 110, so as to prevent the reflector 20 from relative displacement in the subsequent extrusion or overmolding process, and finally, the sheath 140 is wrapped on the outside of the outer conductor 130 through extrusion or overmolding. Therefore, compared with the first connection method, the leaky cable of the second connection method is more suitable for large-scale production.

[0082] In some embodiments, the rectangular copper foil 220 covers at least one of the slots 131 .

[0083] Specifically, the orthographic projection of the rectangular copper foil 220 needs to completely cover at least one slot 131 on the outer conductor 130 of the leaky cable to ensure that the electromagnetic waves radiated by the leaky cable can be effectively coupled to the rectangular copper foil 220. In addition, the size of the rectangular copper foil 220 must be larger than the size of the slot 131. For example, if the width of the leaky cable slot 131 is 2 mm, the width of the rectangular copper foil 220 must be ≥ 2 mm.

[0084] The reason why the rectangular copper foil 220 covers at least one of the slots 131 is to ensure that the electromagnetic waves radiated by the slots 131 can be directly coupled to the surface of the rectangular copper foil 220 to excite resonance. When the rectangular copper foil 220 covers the slots 131, the electromagnetic field forms a strong coupling region between the slots 131 and the rectangular copper foil 220, reducing the leakage of energy into free space and improving the coupling efficiency.

[0085] Moreover, when the rectangular copper foil 220 covers the slot 131, the impedance transition of the electromagnetic wave from the slot 131 to the rectangular copper foil 220 is smoother, reducing the signal reflection loss caused by the impedance mutation. The coupling between the rectangular copper foil 220 and the slot 131 ensures the stability of the resonant frequency and avoids the frequency deviation caused by gap or misalignment.

[0086] In this embodiment, the rectangular copper foil 220 covers at least one slot 131, and the energy loss is reduced by direct coupling, thereby achieving the purpose of improving signal reflection efficiency, and also improving the reflected signal strength and positioning accuracy, thereby enhancing the fault detection sensitivity, and effectively reducing external interference and intrusion risks. This design significantly optimizes the performance of the leaky cable system, especially in 5G high frequency band (such as 28GHz) applications.

[0087] In some embodiments, the length direction of the rectangular copper foil 220 is parallel to the axial direction of the leakage cable.

[0088] Specifically, this design is mainly to achieve electromagnetic wave polarization matching and radiation direction matching, where: The polarization matching of the electromagnetic wave lies in the polarization characteristics of the rectangular copper foil 220 and the characteristics of the electromagnetic wave emitted by the leaky cable.

[0089] The electromagnetic waves radiated by the rectangular copper foil 220 are linearly polarized, and their polarization direction is consistent with the length direction (long side direction) of the rectangular copper foil 220. If the length direction of the rectangular copper foil 220 is parallel to the axial direction of the leaky cable, the polarization direction of the reflector 20 is consistent with the polarization direction of the electromagnetic waves radiated by the leaky cable, which can maximize the signal coupling efficiency.

[0090] The leaky cable radiates electromagnetic waves axially through the gaps or holes (slots 131) on the outer conductor 130, and its polarization direction is usually parallel to the axial direction of the leaky cable (longitudinal polarization). When the polarization direction of the reflector 20 is consistent with that of the leaky cable, the signal reflection efficiency is the highest.

[0091] The radiation direction is matched between the radiation direction of the rectangular copper foil 220 and the radiation mode of the leaky cable.

[0092] The maximum radiation direction of the rectangular copper foil 220 is perpendicular to the plane of the rectangular copper foil 220 (ie, perpendicular to the surface of the leaky cable). If the length direction of the rectangular copper foil 220 is parallel to the axial direction of the leaky cable, its radiation direction will form an effective coupling with the electromagnetic wave propagation direction (axial direction) of the leaky cable.

[0093] The electromagnetic wave energy of the leaky cable mainly propagates in the axial direction and radiates outward through the slots 131. The radiation direction of the rectangular copper foil 220 needs to match the electromagnetic wave propagation direction of the leaky cable in order to effectively reflect the signal.

[0094] Therefore, when the reflector 20 is mounted on the surface of the outer conductor 130, the length direction of the rectangular copper foil 220 must be strictly parallel to the axial direction of the leaky cable to ensure polarization matching and consistent radiation direction.

[0095] On the contrary, if the long side of the rectangular copper foil 220 is tilted or perpendicular to the axial direction of the leaky cable, polarization mismatch will occur, making the polarization direction of the reflector 20 inconsistent with that of the leaky cable, and the signal reflection efficiency will decrease; resulting in a shift in the radiation direction, the maximum radiation direction of the rectangular copper foil 220 deviates from the propagation direction of the electromagnetic wave of the leaky cable, and the coupling efficiency will decrease; and the resonant frequency will also be shifted. When the size of the rectangular copper foil 220 does not match the surface curvature of the leaky cable, the resonant frequency may be slightly affected.

[0096] In this embodiment, by strictly following the installation direction requirements, the length direction of the rectangular copper foil 220 of the reflector 20 is parallel to the axial direction of the leaky cable, ensuring polarization matching and consistent radiation direction, thereby maximizing reflection efficiency and detection sensitivity and achieving high-reliability fault location.

[0097] In some embodiments, the leaky cable includes a first end and a second end, the direction from the first end to the second end is defined as a first direction, and the reflectors 20 are arranged equidistantly along the first direction to divide the leaky cable into a plurality of sections, and each reflector 20 corresponds one-to-one to each section of the leaky cable, and the corresponding target frequency when each reflector 20 resonates increases or decreases successively along the first direction.

[0098] Specific: The two ends of the leaky cable are defined as a first end and a second end. The direction from the first end to the second end is defined as a first direction, which determines the arrangement order of the reflectors 20 and the propagation path of the signal.

[0099] A plurality of reflectors 20 are equidistantly distributed along the first direction of the leaky cable, and each reflector 20 corresponds to each section of the leaky cable one by one. In this way, the reflector 20 of each section of the leaky cable plays a role of signal reflection and generates resonance when the signal arrives.

[0100] The resonant frequency of each reflector 20 increases or decreases in sequence along the first direction, that is, as the position of the reflectors 20 changes, their resonant frequencies also change regularly.

[0101] When the reflector 20 receives a signal that matches its resonant frequency, it will resonate, thereby increasing the reflectivity of the frequency signal, thereby effectively improving the reflection effect of the signal.

[0102] The segmented design of the leaky cable makes the leaky cable naturally divided into several segments because the reflectors 20 correspond to the segments of the leaky cable one by one. This design can effectively improve the signal monitoring accuracy and fault detection capability of the leaky cable. The signal reflection efficiency of each segment is closely related to its corresponding reflector 20, making the fault location more accurate.

[0103] In order to further improve the detection effect of the water ingress fault point of the above-mentioned leaky cable, Figure 5 As shown, a detection method for the above-mentioned multi-directional narrow beam directional leaky cable is proposed, comprising: Step S100: acquiring the reflectors 20 of the corresponding sections of the leaky cable and a resonance frequency sequence corresponding to each of the reflectors 20, wherein each of the resonance frequencies is monotonically increasing or decreasing along the first direction.

[0104] Step S200: transmitting detection signals matching the resonance frequency of each reflector 20 to the leaky cable in sequence according to the arrangement order of the resonance frequency sequence by the wide-band signal generator.

[0105] Step S300: When each of the detection signals reaches the reflector 20 of the corresponding segment, the reflector 20 of the corresponding segment excites resonance through the electromagnetic coupling effect between the rectangular copper foil 220 and the slot 131, so that the reflector 20 of the corresponding segment generates a reflection signal with a characteristic frequency and transmits it back to the cable body 10.

[0106] Step S400: the signal receiver monitors the reflected signal in the cable body 10 in real time, samples and analyzes the frequency spectrum of each reflected signal, and records the signal peak strength at each characteristic frequency.

[0107] Step S500: If the characteristic frequency of a certain section of the reflected signal does not appear in the detection spectrum or the peak intensity is lower than the threshold range, it is determined that the section of the leaky cable has a fault; wherein the detection spectrum is a mapping relationship table between each of the reflectors 20 and the corresponding resonant frequency, and the threshold range is the allowable variation range of the reflected signal peak value corresponding to each of the reflectors 20 when the leaky cable is in a normal state.

[0108] Specific: “Step S100: obtaining the reflectors 20 of each corresponding section of the leaky cable and the resonance frequency sequence corresponding to each reflector 20, wherein each resonance frequency is monotonically increasing or decreasing along the first direction” is the step of obtaining and calibrating the resonance frequency sequence.

[0109] In this step, it is necessary to obtain the position and corresponding resonant frequency of each reflector 20 according to the structural design of the leaky cable. Each reflector 20 corresponds one-to-one to a certain section of the leaky cable, and the resonant frequency of the reflector 20 is the frequency at which it can produce the maximum reflection when receiving a signal. The resonant frequency sequence of the reflector 20 should be monotonically increasing or decreasing along the first direction of the leaky cable. This step needs to rely on the resonant frequency arrangement when the leaky cable is designed to ensure that the resonant frequency of each reflector 20 can be covered when the signal is transmitted and received. The key point is that the monotonic change of the resonant frequency provides a linear basis for the fault detection of the leaky cable, ensuring that the signals of different sections can be distinguished and monitored.

[0110] Step S100 specifically includes the following steps: Before the leaky cable leaves the factory, the resonant frequency of each reflector 20 is calibrated one by one by a vector network analyzer, and its corresponding position (such as the number of meters from the starting end of the leaky cable) and the resonant frequency value are recorded. A reflector 20 position-frequency mapping table is established and stored in the database of the detection system as a benchmark reference.

[0111] Then, before the on-site calibration test, a reference reflector 20 (with a known fixed frequency) is set at the first end or the second end of the leaky cable, and a signal of the corresponding frequency is periodically transmitted. If the peak deviation of the received signal exceeds ±1MHz, a full-band fast frequency sweep (step 1MHz) is triggered to recalibrate the frequencies of all reflectors 20.

[0112] The step of “step S200: transmitting detection signals matching the resonant frequencies of the reflectors 20 to the leaky cable in sequence by the wideband signal generator according to the arrangement order of the resonant frequency sequence” is detection signal transmission control.

[0113] In this step, a wideband signal generator is used to transmit a detection signal matching the resonant frequency of each reflector 20 to the leaky cable in the order of the resonant frequencies of the reflectors 20. The frequency of the signal generator changes step by step and matches the resonant frequency of each reflector 20. This process can be achieved by setting the frequency modulation function of the signal generator. The key point is that the signal generator must be able to accurately control the transmission frequency and transmit in sequence to ensure that the resonant frequency of each reflector 20 is accurately excited, thereby generating a corresponding reflection signal.

[0114] Step S200 specifically includes the following steps: Determine the sequential transmission mode of the detection signal, and transmit the continuous wave signal matching its resonant frequency in the order of the reflector 20 position (from the near end to the far end) in sequence. It should be noted that each frequency needs to stay for a target time Δt, which is required to ensure that the signal propagates to the farthest reflector 20 (e.g., the propagation delay of a 1km leaky cable is about 5μs). The target time ton can be obtained by calculation or detection.

[0115] Furthermore, the transmit power is dynamically adjusted according to the length of the leaky cable (e.g., +20dBm is used for a 1km leaky cable and +30dBm is used for a 2km cable) to avoid misjudgment due to far-end signal attenuation.

[0116] Furthermore, low-frequency modulation (such as 1kHz square wave) can be superimposed on the continuous wave signal, and the direct signal and the reflected signal can be distinguished by envelope detection to suppress noise interference. Specifically, the noise interference can be reduced by using time domain gating technology to only receive the reflected signal within a specific time window after the transmitted signal (such as the corresponding position ±5m propagation time).

[0117] “Step S300: When each of the detection signals reaches the reflector 20 of the corresponding segment, the reflector 20 of the corresponding segment excites resonance through the electromagnetic coupling effect between the rectangular copper foil 220 and the slot 131, so that the reflector 20 of the corresponding segment generates a reflection signal with a characteristic frequency which is transmitted back to the cable body 10.” The characteristic frequency should be approximately the resonant frequency of the reflector 20.

[0118] In this step, when each detection signal reaches a certain section of the leaky cable, the signal interacts with the rectangular copper foil 220 and the slot 131 on the reflector 20 through electromagnetic coupling, and excites the reflector 20 to resonate. Since each reflector 20 has a specific resonant frequency, it will reflect the specific signal frequency and transmit the reflected signal back to the main body of the leaky cable. The reflected signal will be transmitted back along the leaky cable and finally captured by the signal receiver. The key point is that the design of the reflector 20 (especially the electromagnetic coupling effect of the rectangular copper foil 220 and the slot 131) ensures the effective reflection of the signal. The size and position of the copper foil and the slot 131 need to be precisely controlled to ensure that the correct resonance is excited on each reflector 20.

[0119] “Step S400: The signal receiver monitors the reflected signal in the cable body 10 in real time, samples and analyzes the frequency spectrum of each reflected signal, and records the peak signal intensity at each characteristic frequency.” This step is for the collection and analysis of reflected signals.

[0120] In this step, the reflected signal is monitored in real time by the signal receiver. The signal receiver captures and records the reflected signal transmitted in the leaky cable. The spectrum of the reflected signal is sampled in real time by a spectrum analyzer, and in particular, the signal peak intensity at the characteristic frequency corresponding to each reflector 20 is recorded. The reflected signal of each reflector 20 has a specific frequency characteristic, so the working state of the leaky cable can be monitored based on these frequency characteristics. The key point is that the spectrum sampling accuracy of the signal receiver is crucial. Only by accurately recording the spectrum characteristics of each reflector 20 can the fault point of the leaky cable be effectively detected. The spectrum analysis method should be able to distinguish the signal peak intensity at different frequencies.

[0121] Step S400 specifically includes the following steps: The signal receiver collects the reflected signal at the target sampling rate (e.g. ≥10GS / s) and generates a spectrum through fast Fourier transform. It should be noted that the frequency resolution is ≤1MHz.

[0122] A monitoring bandwidth (eg, ±5 MHz) is set for the characteristic frequency corresponding to each reflector 20, and the peak intensity within the frequency band is extracted.

[0123] Furthermore, the peak strength can be normalized to compensate for the path loss of the received signal strength. The compensation formula is as follows: .

[0124] in: : Compensated received signal strength (standardized signal strength), which indicates the signal strength value after taking path loss into account.

[0125] : Original received signal strength, which means the received signal strength without path loss compensation.

[0126] : The actual propagation distance of the received signal, in meters (m), that is, the actual distance of the signal from the transmitting source to the receiving point.

[0127] : Reference distance (usually the distance between two adjacent reflectors 20), i.e. the signal strength received at this distance is used as a benchmark for standardization.

[0128] : Path loss compensation term, which represents the change of signal strength with distance. According to the free space path loss model, the signal strength is inversely proportional to the square of the distance, and the specific loss is expressed in logarithmic form.

[0129] The above formula is based on the logarithmic path loss model, which takes into account that the signal will gradually attenuate as the distance increases during the propagation process. The logarithmic model allows the path loss to reasonably reflect the attenuation law in actual communication. In most wireless communication applications, the relationship between signal strength and distance presents a logarithmic characteristic, that is, the signal strength decreases in inverse proportion to the square of the distance. In order to make a unified comparison or calculation, the received signal strength is usually standardized to eliminate the influence of distance.

[0130] The above formula can convert the signal strength at different distances into a unified standardized signal strength through path loss compensation, which makes it easier to compare the signal strength at different locations and in different environments. In addition, the formula also accurately reflects the law of signal attenuation as the distance increases in the form of logarithms, which is in line with the actual situation of wireless propagation.

[0131] In short, the purpose of the above formula is to eliminate the signal strength differences caused by different propagation distances so that the signal strength can be standardized, thereby facilitating subsequent analysis and processing.

[0132] "Step S500: If the characteristic frequency of a certain section of the reflected signal does not appear in the detection spectrum or the peak intensity is lower than the threshold range, it is determined that the section of the leaky cable has a fault; wherein the detection spectrum is a mapping relationship table between each of the reflectors 20 and the corresponding resonant frequencies, and the threshold range is the allowable variation range of the reflected signal peak value corresponding to each of the reflectors 20 under the normal state of the leaky cable." This step is for fault determination and location.

[0133] In this step, the measured reflected signal spectrum is compared with the preset standard spectrum (i.e., the spectrum under normal conditions). If the characteristic frequency of a certain section of the reflected signal does not appear in the detection spectrum, or its signal peak strength is lower than the threshold range, it is determined that the section of the leaky cable may have a fault. The threshold range is set by the allowable variation range of the reflected signal peak under normal leaky cable conditions. The key point is that the spectrum characteristics under normal conditions and the changes under fault conditions can be determined by establishing a threshold range. The setting of the threshold range needs to rely on the standard working conditions of the leaky cable, such as signal strength, spectrum distribution, etc. By comparing with known fault types, accurate fault judgment can be made.

[0134] Step S500 specifically includes the following steps: If a characteristic frequency does not appear in the detection spectrum (for example, no peak is detected after multiple consecutive scans), the segment is marked as a "suspected fault"; if the peak intensity is lower than the lower threshold, it is marked as an "attenuation fault".

[0135] Furthermore, the frequency of the adjacent reflector 20 may be transmitted to the suspected fault segment to verify whether it is a frequency offset fault (such as water infiltration causing resonance frequency drift). For specific fault type identification, please refer to Table 2.

[0136]

[0137] Furthermore, optimization can be performed according to the corresponding application scenarios, for example: In the tunnel environment, an anti-humidity design is added, and the substrate 210 of the reflector 20 can be made of ceramic material to reduce the influence of water vapor on the resonant frequency. In addition, the detection signal transmission interval is shortened to 5ms to adapt to the multipath reflection environment in the tunnel.

[0138] In subway platforms, narrow-interval frequency allocation (5MHz) is used, with a positioning accuracy of ±2m, and platform monitoring cameras are used to quickly locate fault points. In addition, the leakage cable detection system and BIM model can be integrated to achieve three-dimensional visualization of the fault section.

[0139] Through the above-mentioned expansion scheme, the detection method is significantly optimized in terms of accuracy, efficiency and robustness (dynamic compensation), and can adapt to the engineering application requirements in complex environments.

[0140] In summary, the frequency of the reflector 20 should increase or decrease along the first direction of the leaky cable, providing an accurate benchmark for signal detection and fault location. The frequency scheduling function of the wideband signal generator ensures that the frequency excitation of each reflector 20 matches the detection signal. The electromagnetic coupling between the rectangular copper foil 220 and the slot 131 is the key to the generation of the reflected signal, ensuring the effective reflection of the signal. Accurate spectrum analysis and signal peak strength measurement can quickly identify leaky cable faults and determine the fault point by comparing with the standard spectrum.

[0141] The above contents described in this specification are merely examples of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, as long as they do not deviate from the contents of the present specification or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A multi-directional narrow beam directional leaky cable, characterized in that: include: The cable body includes: Inner conductor; An insulating layer is coaxially sleeved outside the inner conductor; An outer conductor, coaxially sleeved outside the inner conductor; A sheath, covering the outer surface of the outer conductor; A plurality of reflectors, all connected to the outer conductor, and each of the reflectors is evenly spaced along the axial direction of the cable body, and the reflectors are configured to generate resonance when receiving a signal of a target frequency, so that the reflectivity of the reflector to the signal of the target frequency is greater than the lower limit of the target threshold range, and there is a difference in the target frequency corresponding to each of the reflectors when the resonance occurs; Wherein, the leaky cable includes a detection state for detecting its own fault point. When the leaky cable is in the detection state, the two ends of the cable body are respectively connected to a wideband signal generator and a signal receiver. The wideband signal generator sequentially transmits signals that can cover the resonant frequency of each reflector, and the signal receiver sequentially receives each signal entering the cable body and records the spectrum characteristics of the signal.

2. A multi-directional narrow beam directional leaky cable according to claim 1, characterized in that: The outer conductor surface is provided with two rows of orthogonally distributed slots along its own axis, and the angle between the centers of the two rows of slots and the axis of the inner conductor is at most 90°, and the slots form a conductive tube cavity with a gradually shrinking size along the direction away from the axis of the inner conductor.

3. A multi-directional narrow beam directional leaky cable according to claim 2, characterized in that: The reflector comprises: substrate; A rectangular copper foil is arranged on one side of the substrate; The copper layer is arranged on a side of the substrate away from the rectangular copper foil, and the copper layer is electrically connected to the outer conductor.

4. The multi-directional narrow beam directional leaky cable according to claim 3, characterized in that: A connecting groove is provided on the surface of the sheath, the reflector is arranged at the connecting groove, the side of the rectangular copper foil facing away from the substrate is arranged toward the outer conductor, and a gap is left between the rectangular copper foil and the outer conductor.

5. The multi-directional narrow beam directional leaky cable according to claim 3, characterized in that: The orthographic projection area of ​​the copper layer on the side surface of the substrate is smaller than the orthographic projection area of ​​the rectangular copper foil on the side surface of the substrate.

6. The multi-directional narrow beam directional leaky cable according to claim 5, characterized in that: The reflector is arranged in the sheath so that the reflector bears the pressure applied by the sheath and directed to the axis of the inner conductor, and the copper layer is connected to the outer conductor through a conductive adhesive.

7. The multi-directional narrow beam directional leaky cable according to claim 6, characterized in that: The outer surface of the outer conductor is provided with a coating layer, and the inner side of the coating layer abuts against the reflector so as to apply a coating force directed to the axis of the inner conductor to the reflector.

8. A multi-directional narrow beam directional leaky cable according to claim 4, 6 or 7, characterized in that: The rectangular copper foil is at least covered on one of the slots.

9. The multi-directional narrow beam directional leaky cable according to claim 8, characterized in that: The length direction of the rectangular copper foil is parallel to the axial direction of the leakage cable.

10. The multi-directional narrow beam directional leaky cable according to claim 9, characterized in that: The leaky cable includes a first end and a second end, the direction from the first end to the second end is defined as a first direction, the reflectors are arranged equidistantly along the first direction to divide the leaky cable into a plurality of sections, the reflectors correspond one-to-one to each section of the leaky cable, and the corresponding target frequencies of the reflectors when resonating increase or decrease sequentially along the first direction.

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