A multi-directional narrow-beam directional leaky cable

Abstract

The present application relates to a multi-directional narrow-beam directional leaky cable. The leaky cable includes a cable body, a wide-band signal generator, and a signal receiver. Among them, the cable body includes a plurality of reflectors, each reflector is connected to the outer conductor, and is evenly distributed at equal intervals along the axial direction of the cable body, and is configured to generate resonance when receiving a target frequency signal, the reflectivity is greater than the lower limit of the target threshold range, and the target frequencies corresponding to the resonance generated by each reflector have a difference. The wide-band signal generator is connected to the cable body and can emit signals covering the resonance frequencies of each reflector. The signal receiver is connected to the cable body, and can receive the signals entering the cable body in real time and record the spectral characteristics. Through the collaborative work of multiple reflectors, a wide-band signal generator, and a signal receiver, this technical solution realizes the accurate analysis of the frequency characteristics of the leaky cable signals. Especially in a complex environment, it can accurately locate distributed fault points with high precision, improving the efficiency and accuracy of fault detection.

Description

Technical Field

[0001] The present invention relates to a leaky cable, and more particularly 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 railway lines. These environments usually have complex installation conditions and high requirements for signal transmission. Due to the characteristics of leaky cables, they can provide continuous and uniform signal coverage for wireless communication in enclosed environments such as tunnels and subways. Leaky cables not only have advantages in high-frequency signal transmission, but also their ability to adapt to complex environments has enabled them to be 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 manner, making it difficult to directly observe and repair. Coupled with the influence of harsh environmental factors such as humidity and temperature, the faults of leaky cables often appear relatively concealed and may spread to the entire system as moisture seeps in.

[0003] Currently, most leaky cable designs adopt the distributed radiation principle, radiating signals through gaps or holes on the outer conductor, and achieving signal coverage by continuously leaking signals on the surface of the leaky cable. Since the signal leakage is distributed, leaky cables can achieve wide signal coverage through long-distance transmission. Currently, the commonly used detection methods for leaky cables include standing wave ratio testing and time domain reflectometry. The former is mainly used to detect the integrity of leaky cables, and the latter can locate impedance discontinuity points in the cable.

[0004] However, since the faults of leaky cables may be distributed (such as the expansion of fault points caused by the entry of moisture), traditional fault detection technologies (such as standing wave ratio testing, time domain reflectometry, etc.) cannot accurately locate multi-point faults and lack comprehensive monitoring means for leaky cable signals in complex environmental conditions. Specifically, standing wave ratio testing is mainly used to detect the overall performance of leaky cables and cannot provide high-precision fault point location; although time domain reflectometry can locate impedance discontinuity points in the cable, its applicability in devices with distributed radiation characteristics such as leaky cables 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 for leaky cable fault location to improve the efficiency and accuracy of fault troubleshooting. Therefore, it is necessary to propose a new direction narrow-beam directional leaky cable to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a multi-directional narrow-beam directional leaky cable with an optimized design based on traditional leaky cables to improve the fault diagnosis and location 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:

[0007] The cable body includes:

[0008] Inner conductor;

[0009] An insulating layer is coaxially sleeved outside the inner conductor;

[0010] An outer conductor, coaxially sleeved outside the inner conductor;

[0011] A sheath, covering the outer surface of the outer conductor;

[0012] 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.

[0013] 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.

[0014] 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.

[0015] Preferably, the reflector comprises:

[0016] substrate;

[0017] A rectangular copper foil is arranged on one side of the substrate;

[0018] 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.

[0019] 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.

[0020] 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.

[0021] Preferably, the reflector is disposed in the sheath such that the reflector bears the pressure applied by the sheath towards the axis of the inner conductor, and the copper layer is connected to the outer conductor by conductive adhesive.

[0022] 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 to apply a wrapping force to the reflector towards the axis of the inner conductor.

[0023] Preferably, the rectangular copper foil covers at least one of the slots.

[0024] Preferably, the length direction of the rectangular copper foil is parallel to the axial direction of the leaky cable.

[0025] Preferably, the leaky cable includes a first end and a second end, and the direction from the first end to the second end is defined as the first direction. The reflectors are arranged at equal intervals along the first direction to divide the leaky cable into several segments. Each reflector corresponds to one segment of the leaky cable, and the target frequencies corresponding to the resonance of each reflector increase or decrease in sequence along the first direction.

[0026] Advantages of the embodiments in the present invention:

[0027] Due to the technical solution including a plurality of reflectors, a broadband signal generator, and a signal receiver, the reflector can achieve high-precision signal reflection through the resonance of the target frequency signal, and the broadband signal generator can cover the resonance frequencies of multiple reflectors. Therefore, more accurate frequency characteristic analysis can be provided during the transmission of the leaky cable signal. This design effectively solves the problem in the prior art that distributed fault points cannot be located, especially for the precise detection of high-frequency signals and the location of multi-point faults in complex environments. In addition, through the spectral characteristics recorded by the signal receiver, more comprehensive and dynamic signal monitoring can be provided, further improving the efficiency and accuracy of leaky cable fault detection. Furthermore, high-precision positioning and real-time monitoring of leaky cable faults are achieved, effectively improving the efficiency of fault troubleshooting and ensuring the stability and reliability of the leaky cable signal in a complex installation environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Shows a schematic structural diagram of a leaky cable in an embodiment of the present invention.

[0029] Figure 2 Shows a schematic radial cross-sectional view of the leaky cable when the rectangular copper foil is arranged towards the inner conductor in an embodiment of the present invention.

[0030] Figure 3 Shows a schematic radial cross-sectional view of the leaky cable when the rectangular copper foil is arranged away from the inner conductor in an embodiment of the present invention.

[0031] 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.

[0032] Figure 5 The flowchart of the method for detecting a leaky cable in one embodiment of the present invention is shown.

[0033] 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

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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 long and narrow channel. The target scenarios of the leaky cable include tunnels, subways, etc., and are particularly suitable for scenarios such as curved sections of tunnels (requiring multi-directional coverage) and subway platforms (requiring directional coverage) to ensure uniform distribution of signals in complex paths.

[0038] A multi-directional narrow-beam directional leaky cable includes a cable body 10. Among them, the cable body 10 includes an inner conductor 110, an insulating layer 120, an outer conductor 130, and a sheath 140. Among them, 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 on the outer surface of the outer conductor 130.

[0039] Specifically, the inner conductor 110 can be made of copper-clad aluminum material, which can be embodied as high-purity oxygen-free copper in a specific manner and is used to transmit high-frequency signals.

[0040] The insulating layer 120 is coaxially coated outside the inner conductor 110, and a material with a lower dielectric constant can be selected, which can be embodied as made of foamed polyethylene in a specific manner (dielectric constant ε = 1.5 - 1.6) to reduce signal loss during transmission, which can be embodied as attenuation < 0.1 dB / m @ 28 GHz in a specific manner.

[0041] The outer conductor 130 can be made of corrugated copper pipe, and two rows of orthogonally distributed rectangular slot holes 131 are axially opened on the surface. The distance between each row of slot holes 131 is half a wavelength, where the wavelength is the wavelength corresponding to the signal to be transmitted by the leaky cable. The included angle between the center line of the two rows of slot holes 131 and the axis of the inner conductor 110 is at most 90°, so as to form a multi-directional radiation beam. Among them, the two rows of orthogonal slot holes 131 form independent radiation beams in the horizontal and vertical directions to achieve multi-directional coverage (such as bi-directional radiation within the tunnel cross-section).

[0042] In some embodiments, the slot hole 131 forms a conductive pipe cavity with a gradually shrinking size in the direction away from the axis of the inner conductor 110, which is embodied as an inverted trumpet-shaped slot hole 131 or an inverted conical slot hole 131 in a specific manner. The tapered structure of the slot hole 131 restricts the radiation angle of electromagnetic waves, and a narrow-beam radiation can be formed at the closed end to reduce signal leakage. Further, silver can be plated on the inner wall of the slot hole 131 (thickness 0.1 μm) to reduce the surface resistance and improve the high-frequency signal transmission efficiency.

[0043] The sheath 140 can be made of polyethylene materials, such as low-density polyethylene materials and flame-retardant polyvinyl chloride materials. The sheath 140 wraps the outside of the outer conductor 130 and has the characteristics of waterproof, flame-retardant, and anti-ultraviolet.

[0044] 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 scenarios such as tunnels, a new multi-directional narrow-beam directional leaky cable suitable for quickly locating the damaged fault point is required. The cable body 10 further includes a number of reflectors 20. And, the leaky cable includes a detection state for detecting its own fault point. When the leaky cable is in the detection state, a broadband signal generator and a signal receiver are respectively connected to both ends of the cable body 10. The broadband signal generator sequentially emits signals that can cover the resonant frequencies of the reflectors 20. The signal receiver sequentially receives the signals entering the cable body 10 and records the spectral characteristics of the signals. Among them, a number of reflectors 20 are all connected to the outer conductor 130, and the reflectors 20 are equidistantly distributed along the axial direction of the cable body 10. The reflector 20 is configured to resonate 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 are differences in the target frequencies corresponding to the resonances of the reflectors 20.

[0045] Specifically:

[0046] The reflector 20 can be embodied as a patch antenna and a slot antenna in a specific manner. 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 produce resonant units of different sizes through standard PCB processes, with low cost and easy mass production.

[0047] In some embodiments, the reflector 20 is composed of a substrate 210, a rectangular copper foil 220, and a copper layer 230. As Figure 2 or Figure 3 shown, the rectangular copper foil 220 is disposed on one side of the substrate 210, and the copper layer 230 is installed on the side of the substrate 210 facing away from the rectangular copper foil 220. The copper layer 230 is also electrically connected to the outer conductor 130. The reflector 20 can specifically use a standard PCB process to make an epoxy resin substrate 210, with double-sided copper plating, and etch the rectangular copper foil 220 on the top layer through chemical or engraving machines, and retain the bottom copper layer 230 as a ground plane.

[0048] Among them, the rectangular copper foil 220 is a resonant unit. The copper layer 230 is a complete surface layer, which can be attached to the outer conductor 130 or connected to the outer conductor 130 through a conductive member. The substrate 210 can be made of epoxy resin, and its size needs to be adapted to 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 realizing frequency differentiation in this application, which is related to whether there will be missed judgments or misjudgments during fault detection. And the length of the rectangular copper foil 220 is the key parameter determining the resonant frequency and the rectangular copper foil 220 It can be obtained through the following formula:

[0049] wherein, , 0.95 is a correction factor considering the edge effect.

[0050] The design of the rectangular copper foil 220 is based on half - wavelength resonance and resonance reflection. Among them, half - wavelength resonance means that when the length of the rectangular copper foil 220 in the reflector 20 is approximately half - wavelength, standing waves are formed at both ends of the rectangular copper foil 220 in the length direction, achieving the maximum radiation efficiency. Resonance reflection means that when the frequency of the incident electromagnetic wave matches the resonance frequency of the rectangular copper foil 220, the rectangular copper foil 220 absorbs energy and reflects it efficiently, and the reflected signal is injected 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 ± allowable deviation value displayed on the spectrum recorded by the signal receiver when the leaky cable receives the reflected signal from the reflector 20, where the allowable deviation value can be obtained through repeated tests. The resonance frequency means that each reflector 20 is designed to resonate at a specific frequency (such as ), which means that when the frequency of the incident electromagnetic wave is equal to the resonance frequency of the reflector 20, the reflector 20 will exhibit the maximum reflection efficiency. And the edge - effect correction means that the effective length of the actual rectangular copper foil 220 is slightly less than the theoretical value, and it 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 relatively low.

[0051] In summary, the differential design of the rectangular copper foil 220 based on the resonance frequency plays a role in this application by designing reflectors 20 with different sizes so that they resonate at different frequencies. When a certain section of the leaky cable fails, the reflected signal of the reflector 20 in 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.

[0052] The size design of the rectangular copper foil 220 can be carried out in the following order in a specific way:

[0053] First, determine the target frequency band, for example, select 2.4 GHz - 2.5 GHz (Wi - Fi frequency band, which is convenient for testing).

[0054] Then calculate the length of the rectangular copper foil 220:

[0055]

[0056] For every 50 MHz increase in frequency, the length decreases by approximately 0.6 mm.

[0057] "The electrical connection between the copper layer 230 and the outer conductor 130" is to form a complete RF loop. Otherwise, the reflection efficiency will be significantly reduced. The specific principle is as follows:

[0058] First, "the electrical connection between the copper layer 230 and 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. Such a 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 the copper layer 230 is not electrically connected to the outer conductor 130, the copper layer 230 is not conducting with the outer conductor 130, and the surface current cannot return, resulting in the dissipation of energy in the form of electromagnetic radiation near the rectangular copper foil 220, and the reflection efficiency is significantly reduced.

[0059] Second, to maintain impedance matching, the transmission of RF signals requires the continuity of the characteristic impedance. Otherwise, signal reflection (increase in standing wave ratio) will occur. 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, a capacitive impedance will be formed between the copper foil and the outer conductor 130 of the leaky cable, resulting in partial reflection of the signal at the interface.

[0060] The connection feature of "the electrical connection between the copper layer 230 and the outer conductor 130" can enhance the reflection efficiency, suppress the divergence loss of electromagnetic waves, improve the signal coupling efficiency, and improve the anti-interference ability for the signal reflected after the resonance of the rectangular copper foil 220. Specifically:

[0061] Enhancing the reflection efficiency is reflected in the directional reflection of the 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. 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, due to the sudden interruption (or change) of the current path at the slot 131, the current density changes, thereby exciting electromagnetic waves. This electromagnetic wave is directionally coupled back into the leaky cable through the slot 131 of the outer conductor 130 of the leaky cable, rather than diverging into free space.

[0062] The suppression of electromagnetic wave divergence loss is reflected in the constraint on the electromagnetic field. After the copper layer 230 is electrically connected to the outer conductor 130, a structure similar to the "mirror effect" is formed, which confines 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. The physical mechanism is that the copper layer 230 serves as a reference ground plane and jointly forms a waveguide structure with the leaky cable outer conductor 130 to guide the electromagnetic wave to propagate along the surface of the leaky cable.

[0063] The improvement of signal coupling efficiency is reflected in the excitation of current at the slot hole 131. The return current transmitted by the copper layer 230 flows on the surface of the leaky cable outer conductor 130. When the current flows through the slot hole 131, electromagnetic radiation is generated due to the sudden change of the current path (the radiation principle of the slot hole 131), thereby re-injecting the reflected signal into the leaky cable. According to the formula, the electric field strength radiated by the slot hole 131 is proportional to the surface current density: , where is the current density on the surface of the outer conductor 130.

[0064] The improvement of anti-interference ability 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 interfering electromagnetic waves and reduce the influence of noise on the reflected signal.

[0065] Therefore, if the grounding connection is cancelled, the reflection efficiency will drop significantly, and the system is vulnerable to external interference and cannot meet the high-precision detection requirements. Therefore, the grounding design is the core guarantee for the reflector 20 to achieve efficient signal reflection.

[0066] The statement "a plurality of reflectors 20 are equidistantly distributed along the axial direction of the cable body 10" is specifically embodied as segmenting the leaky cable. It can be set that each segment is 10 m long, and there are 100 segments in total (total length 1 km). One reflector 20 is installed on the surface of each segment 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.

[0067] The distribution method of the resonant frequency corresponding to the reflector 20 on each segment of the leaky cable can be distributed as follows:

[0068] The first segment: corresponding frequency , the length of the rectangular copper foil 220 .

[0069] The second segment: corresponding frequency , the length of the rectangular copper foil 220 . ...

[0071] The 100th segment: corresponding frequency , the length of the rectangular copper foil 220 .

[0072] Where is the wavelength of the corresponding signal. The resonant frequencies of the reflectors 20 on each section of the leaky cable are different, and the lengths L of the rectangular copper foils 220 on the reflectors 20 are also different.

[0073] It should be noted that the resonant frequencies corresponding to the above-mentioned reflectors 20 are only for illustration and are difficult to be directly used as a real basis.

[0074] 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 reflectors 20 and the power is adjustable.

[0075] Furthermore, the broadband signal generator can transmit signals to the leaky cable according to the order of the resonant frequencies of the reflectors 20.

[0076] The signal receiver is a vector network analyzer (VNA) or a portable spectrum analyzer, which is built-in with a high-speed ADC module (sampling rate 10GS / s), can collect the spectrum of the reflected signal in real time, supports FFT analysis, and 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 spectral characteristics of the reflected signal, the system can detect whether there is signal attenuation or abnormal change in frequency characteristics, so as to judge the state of each section of the leaky cable. For example: if the characteristic frequency of the reflected signal of a certain section does not appear in the detected spectrum, or its peak intensity is lower than the threshold range, it is determined that there may be a fault in this section of the leaky cable.

[0077] Furthermore, the resonant frequencies of the reflectors 20 increase or decrease in turn along the first direction of the leaky cable, so that it can be quickly determined which section of the leaky cable the reflector 20 corresponding to the resonant frequency is specifically located in.

[0078] When detecting whether there is a fault of breakage or water ingress in the leaky cable of this embodiment, first, connect the broadband signal generator and the signal receiver to both ends of the leaky cable respectively, then inject a swept-frequency signal from one end of the leaky cable through the broadband signal generator, and receive the reflected signal sequentially through the signal receiver, and record the reflection spectrum of the corresponding signal.

[0079] Under normal circumstances, 100 peaks are displayed in the spectrum, corresponding to the resonant frequencies of 100 reflectors 20.

[0080] In case of a fault, when a certain section of the reflector 20 fails or the signal strength decreases, the peak corresponding to its frequency disappears or decreases (such as a fault in the 5th section, the peak disappears or decreases). At this time, it can be determined which reflector 20's reflected signal has a problem through the frequency peak corresponding to the signal in the reflection spectrum, so as to determine the specific position of the section of the leaky cable corresponding to the reflector 20 in the whole leaky cable.

[0081] In this embodiment, due to the collaborative work of multiple reflectors 20, a broadband signal generator, and a signal receiver, the present invention can achieve accurate leaky cable fault location and signal monitoring. By matching each reflector 20 with its specific resonance 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, it can improve the efficiency and accuracy of fault troubleshooting, thereby enhancing the reliability and stability of the leaky cable system.

[0082] Furthermore, considering the complex and variable actual application scenarios of leaky cables, the following three installation methods of the reflector 20 and design methods of resonance frequencies are proposed:

[0083] Narrow interval design: The difference in resonance frequencies between adjacent reflectors 20 is between 5 - 10 MHz. For example, the frequency interval is 5 MHz, the single-segment frequency range is from 1.8 to 2.3 GHz (a total bandwidth of 500 MHz). When the number of reflectors 20 in a single-segment leaky cable is 100, the covered length can be 1 km. When the length of the leaky cable exceeds 1 km, for example, if the leaky cable is 2 km long, 2 segments of the leaky cable are required, and the frequency is reused 2 times.

[0084] Each 10 m interval corresponds to a unique frequency label (such as 1.800 GHz, 1.805 GHz...), and the fault location resolution reaches ±5 m (no need for segment coding). A 2 km leaky cable only requires a 500 MHz bandwidth (1.8 - 2.3 GHz), which saves more frequency resources.

[0085] At this time, the signal generator needs to support a 5 MHz step accuracy (phase noise ≤ -100 dBc / Hz @ 1 kHz offset), and the receiver spectrum resolution ≤ 1 MHz.

[0086] Medium interval design: The difference in resonance frequencies between adjacent reflectors 20 is between 10 - 20 MHz. For example, the frequency interval is 20 MHz, the single-segment frequency range is from 1.8 to 2.78 GHz (a total bandwidth of 980 MHz). When the number of reflectors 20 in a single-segment is 50 (with a 20 MHz interval), the covered length can be 500 m. For a 2 km leaky cable, 4 segments are required, and the frequency is reused 4 times.

[0087] At this time, it is suitable for a general sweep signal source (step accuracy 20 MHz, phase noise ≤ -90 dBc / Hz), and the receiver resolution ≤ 10 MHz is sufficient.

[0088] It should be noted that 4 - segment frequency reuse requires additional coding (such as segment identification codes), which increases the complexity of the signal processing algorithm.

[0089] Hybrid interval design, i.e., dynamically adjustable difference value. For example, in the low-frequency band from 1.8 to 2.0 GHz, the interval is 5 MHz (40 frequencies), and in the high-frequency band from 2.0 to 3.0 GHz, the interval is 20 MHz (50 frequencies). At this time, the total bandwidth is 1.2 GHz (from 1.8 to 3.0 GHz), which can cover a length of 90 reflectors, 20×10m = 900m. For a 2km leaky cable, 3 segments are required, and the frequency needs to be multiplexed 3 times.

[0090] Among them, the low-frequency band (with a 5 MHz interval) is used for high-precision positioning areas (such as tunnel intersections), and the high-frequency band (with a 20 MHz interval) is used for straight sections. And the overall bandwidth requirement is moderate (1.2 GHz), and the positioning accuracy is stratified (±5m / ±20m). It should be noted that the signal generator frequency band needs to be dynamically switched, and the receiver needs to support multi-band joint analysis.

[0091] In summary, the frequency difference between adjacent reflectors 20 can be selected as 5 - 20 MHz according to the scenario requirements. A 5 MHz interval is suitable for short-distance and high-precision positioning, but requires high-spectrum-resolution hardware. A 20 MHz interval is suitable for long-distance and low-cost deployment, and the frequency multiplexing problem is solved by segmented coding. The hybrid 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:

[0092]

[0093] Table 1

[0094] In some embodiments, the signal receiver records the amplitude-frequency curve of the reflected signal, and the fault type can also be judged by the spectral peak (corresponding to the resonant frequency) and amplitude mutation (such as a 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 >150 MHz (for example, from 2.0 GHz to 1.85 GHz); physical damage, when the slot 131 of the outer conductor 130 is deformed or broken, the reflectivity of a specific reflector 20 drops suddenly (from 95% to <80%).

[0095] Furthermore, it is also necessary to clearly illustrate the connection method between the reflector 20 and the cable body 10. However, there are various connection methods between the reflector 20 and the cable body 10. Taking two of them as examples, the specific details are as follows:

[0096] The first connection method, in some embodiments, such as Figure 2As shown, a communication groove 141 is formed on the surface of the sheath 140, and the reflector 20 is disposed in the communication groove 141. The side of the rectangular copper foil 220 facing away from the substrate 210 faces the outer conductor 130, and a gap is left between the rectangular copper foil 220 and the outer conductor 130. Moreover, after the reflector 20 is installed at the communication groove 141, a partial protective layer such as a partial sheath 140 (not shown in the figure) is further provided outside the leaky cable where the reflector 20 is installed, covering the reflector 20 and the leaky cable as a whole, and restoring the closed state at the communication groove 141 of the leaky cable, so as to ensure that the internal environment of the leaky cable is isolated from the outside world.

[0097] Specifically, the reflector 20 is a substrate 210 with double-sided copper cladding. The rectangular copper foil 220 is located on the side of the substrate 210 close to the leaky cable, and the copper layer 230 is located on the side of the substrate 210 away from the leaky cable. The reflector 20 can connect the copper layer 230 to the outer conductor 130 of the leaky cable by punching holes at the edge or specific positions of the substrate 210 and cooperating with a conductive material (such as a copper pillar 30 or conductive adhesive). Taking the copper pillar 30 as an example, one end of the copper pillar 30 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 adhesive or clamping mechanism), so as to realize the conduction between the copper layer 230 and the outer conductor 130 of the leaky cable. It should be noted that when the copper pillar 30 passes through the hole, it does not contact the edge of the rectangular copper foil 220. If necessary, an insulating kit can be provided between the two to insulate and separate the edge of the copper pillar 30 from the rectangular copper foil 220.

[0098] Furthermore, as Figure 2 shown, when using the copper pillar 30 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.

[0099] The second connection method. In some other embodiments, as Figure 3 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 such that the reflector 20 bears the pressure applied by the sheath 140 towards the axis of the inner conductor 110, and the copper layer 230 is connected to the outer conductor 130 by conductive adhesive.

[0100] Specifically, the copper layer 230 is fixed on the surface of the outer conductor 130 via a conductive adhesive. At this time, the inner wall of the sheath 140 abuts against one side of the reflector 20 (the side provided with the rectangular copper foil 220) to apply a pressure to the reflector 20 pointing to the inner conductor 110. Thus, in cooperation with the conductive adhesive, the reflector 20 is fixed at a specific position on the outer conductor 130 to prevent the reflector 20 from being displaced during transportation or laying. It can be understood that in 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, so as to prevent 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. Then, the rectangular copper foil 220 undergoes electromagnetic coupling with the transmitted signal. The rectangular copper foil 220 resonates at the signal of this specific frequency (the resonant frequency of the rectangular copper foil 220), and a surface alternating current is generated due to the resonance. The alternating current will cause an induced current in the copper layer 230. The induced current is transmitted to the outer conductor 130 through the conductive adhesive. After that, the induced current will conduct along the outer conductor 130 to the slot 131 to generate an electromagnetic wave signal of a specific frequency (corresponding to the resonant frequency of the rectangular copper foil 220 on the reflector 20). This electromagnetic wave signal will be radiated back into the leaky cable through the slot 131, thus realizing signal reflection.

[0101] Compared with the first connection method between the reflector 20 and the leaky cable, although the reflected signal is weaker, the second connection method can achieve 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 via a conductive adhesive. And after the conductive adhesive is cured, a coating layer 150 (without shielding effect) can be formed by braiding on the outer surface of the outer conductor 130, specifically as Figure 4 shown, the reflector 20 and the outer conductor 130 are coated as a whole. At this time, the coating layer 150 will apply a coating force to the reflector 20 pointing to the inner conductor 110, so as to prevent the reflector 20 from undergoing relative displacement during subsequent extrusion or plastic coating processes. Finally, the sheath 140 is coated outside the outer conductor 130 through processes such as extrusion or plastic coating. Therefore, compared with the first connection method, the leaky cable of the second connection method is more suitable for large-scale production.

[0102] In some embodiments, the rectangular copper foil 220 covers at least one of the slots 131.

[0103] Specifically, the orthographic projection of the rectangular copper foil 220 needs to completely cover at least one slot 131 on the leaky cable outer conductor 130 to ensure that the electromagnetic waves radiated by the leaky cable can be effectively coupled to the rectangular copper foil 220. Moreover, 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 needs to be ≥ 2 mm.

[0104] The reason for "the rectangular copper foil 220 covers at least one of the slots 131" is to ensure that the electromagnetic waves radiated by the slot 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 slot 131, a strong coupling region is formed between the slot 131 and the rectangular copper foil 220, reducing the leakage of energy into free space and improving the coupling efficiency.

[0105] 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 impedance mutation. The coupling between the rectangular copper foil 220 and the slot 131 ensures the stability of the resonant frequency, avoiding frequency shift caused by gaps or misalignments.

[0106] In this embodiment, through the design of covering at least one slot 131 with the rectangular copper foil 220, energy loss is reduced through direct coupling, achieving the purpose of improving the signal reflection efficiency. Moreover, the intensity of the reflected signal and the positioning accuracy are also improved, thereby enhancing the fault detection sensitivity. Additionally, it can effectively reduce external interference and intrusion risks. This design significantly optimizes the performance of the leaky cable system, especially outstanding in applications in the 5G high-frequency band (such as 28 GHz).

[0107] In some embodiments, the length direction of the rectangular copper foil 220 is parallel to the axial direction of the leaky cable.

[0108] Specifically, this design is mainly to achieve electromagnetic wave polarization matching and radiation direction matching, where:

[0109] Electromagnetic wave polarization matching lies in the polarization characteristics of the rectangular copper foil 220 and the characteristics of the electromagnetic waves emitted by the leaky cable.

[0110] The radiated electromagnetic waves of the rectangular copper foil 220 are linearly polarized, and its 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, maximizing the signal coupling efficiency.

[0111] 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.

[0112] The radiation direction matching lies in the radiation direction of the rectangular copper foil 220 and the radiation pattern of the leaky cable.

[0113] The maximum radiation direction of the rectangular copper foil 220 is perpendicular to the plane of the rectangular copper foil 220 (i.e., 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.

[0114] The electromagnetic wave energy of the leaky cable mainly propagates along the axial direction and radiates outward through the slot holes 131. The radiation direction of the rectangular copper foil 220 needs to match the electromagnetic wave propagation direction of the leaky cable to effectively reflect the signal.

[0115] Therefore, when the reflector 20 is installed 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.

[0116] On the contrary, if the long side of the rectangular copper foil 220 is inclined or perpendicular to the axial direction of the leaky cable, polarization mismatch will occur, resulting in inconsistent polarization directions between the reflector 20 and the leaky cable, and a decrease in signal reflection efficiency; it will cause the radiation direction to shift, the maximum radiation direction of the rectangular copper foil 220 to deviate from the electromagnetic wave propagation direction of the leaky cable, and a decrease in coupling efficiency; moreover, it will also cause the resonant frequency to shift. When the size of the rectangular copper foil 220 does not match the surface curvature of the leaky cable, it may slightly affect the resonant frequency.

[0117] 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 the reflection efficiency and detection sensitivity and achieving high-reliability fault location.

[0118] In some embodiments, the leaky cable includes a first end and a second end, and the direction from the first end pointing to the second end is defined as the first direction. Each of the reflectors 20 is arranged at equal intervals along the first direction to divide the leaky cable into several segments. Each of the reflectors 20 corresponds to each segment of the leaky cable one by one, and the target frequencies corresponding to each of the reflectors 20 when resonating increase or decrease in sequence along the first direction.

[0119] Specifically:

[0120] The two ends of the leaky cable are defined as the first end and the second end. The direction from the first end to the second end is defined as the first direction, and this direction determines the arrangement order of the reflectors 20 and the signal propagation path.

[0121] A number of reflectors 20 are evenly distributed at equal intervals along the first direction of the leaky cable, and each reflector 20 corresponds one by one to each section of the leaky cable. In this way, the reflector 20 of each section of the leaky cable plays a role in signal reflection and generates resonance when the signal arrives.

[0122] The resonance frequencies of each reflector 20 increase or decrease sequentially along the first direction, that is, as the position of the reflector 20 changes, their resonance frequencies also change regularly.

[0123] When the reflector 20 receives a signal matching its resonance frequency, it will generate resonance, thereby increasing the reflectivity of the signal at that frequency, and effectively improving the signal reflection effect.

[0124] The segmented design of the leaky cable makes the leaky cable naturally divided into several sections because the reflector 20 corresponds one by one to the sections of the leaky cable. This design can effectively improve the signal monitoring accuracy and fault detection ability of the leaky cable. The signal reflection efficiency of each section is closely related to the corresponding reflector 20, making the fault location more accurate.

[0125] In order to further improve the detection effect of the water ingress fault point of the above-mentioned leaky cable, as Figure 5 shown, a detection method for the above-mentioned multi-directional narrow-beam directional leaky cable is specifically proposed, including:

[0126] Step S100: Obtain the reflectors 20 of the corresponding sections of the leaky cable and the resonance frequency sequences corresponding to the reflectors 20, where the resonance frequencies are monotonically increasing or decreasing along the first direction.

[0127] Step S200: Sequentially transmit detection signals matching the resonance frequencies of the reflectors 20 to the leaky cable through the broadband signal generator according to the arrangement order of the resonance frequency sequences.

[0128] Step S300: When each detection signal reaches the reflector 20 of the corresponding section, the reflector 20 of the corresponding section is excited to resonate through the electromagnetic coupling effect between the rectangular copper foil 220 and the slot hole 131, so that the reflector 20 of the corresponding section generates a reflected signal with a characteristic frequency and transmits it reversely back to the cable body 10.

[0129] Step S400: The signal receiver monitors the reflected signals in the cable body 10 in real time, samples and analyzes the spectrum of each reflected signal, and records the signal peak intensity at each characteristic frequency.

[0130] 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 there is a fault in that section of the leaky cable; wherein, the detection spectrum is a mapping table of each reflector 20 and the corresponding resonance frequency, and the threshold range is the allowable change range of the peak value of the reflected signal corresponding to each reflector 20 under the normal state of the leaky cable.

[0131] Specifically:

[0132] "Step S100: Obtain 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" This step is for the acquisition and calibration of the resonance frequency sequence.

[0133] In this step, according to the structural design of the leaky cable, the position and corresponding resonance frequency of each reflector 20 need to be obtained. Each reflector 20 corresponds to a certain section of the leaky cable. The resonance frequency of the reflector 20 is the frequency at which it can generate the maximum reflection when receiving a signal. The resonance frequency sequence of the reflector 20 should be monotonically increasing or decreasing along the first direction of the leaky cable. This step depends on the resonance frequency arrangement during the design of the leaky cable to ensure that when the signal is transmitted and received, the resonance frequencies of each reflector 20 can be covered. The key point is that the monotonic change of the resonance 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.

[0134] Step S100 specifically includes the following steps:

[0135] Before the leaky cable leaves the factory, use a vector network analyzer to calibrate the resonance frequency of each reflector 20 one by one, record its corresponding position (such as the number of meters from the starting end of the leaky cable) and the resonance frequency value. And establish a reflector 20 position-frequency mapping table, which is stored in the database of the detection system as a reference.

[0136] Then, before the on-site calibration detection, set a reference reflector 20 (known fixed frequency) at the first end or the second end of the leaky cable, and regularly transmit signals of the corresponding frequency. If the peak shift of the received signal exceeds ±1 MHz, trigger a full-band fast sweep (step 1 MHz) to recalibrate the frequencies of all reflectors 20.

[0137] "Step S200: Sequentially transmit detection signals matching the resonance frequencies of each reflector 20 to the leaky cable through the broadband signal generator according to the arrangement order of the resonance frequency sequence" This step is for the control of the transmission of detection signals.

[0138] In this step, a broadband signal generator is used to sequentially transmit detection signals matching the resonant frequencies of each reflector 20 to the leaky cable in the order of the resonant frequencies of the reflector 20. The frequency of the signal generator changes gradually 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 frequencies of each reflector 20 are accurately excited, thereby generating corresponding reflection signals.

[0139] Step S200 specifically includes the following steps:

[0140] Determine the sequential transmission mode of the detection signals, and sequentially transmit continuous wave signals matching their resonant frequencies in the order of the positions of the reflectors 20 (from the proximal end to the distal end). It should be noted that each frequency needs to dwell for a target time Δt, and this target time needs to ensure that the signal propagates to the most distal reflector 20 (for example, the propagation delay of a 1 km leaky cable is about 5 μs), and the target time can be obtained through calculation or detection.

[0141] Furthermore, dynamically adjust the transmission power according to the length of the leaky cable (for example, +20 dBm for a 1 km leaky cable and +30 dBm for a 2 km leaky cable) to avoid misjudgment caused by signal attenuation at the distal end.

[0142] Even further, a low-frequency modulation (such as a 1 kHz square wave) can be superimposed on the continuous wave signal, and the direct signal and the reflection signal can be distinguished through envelope detection, thereby suppressing noise interference. Specifically, the noise interference can be reduced by adopting time-domain gating technology, and only the reflection signals within a specific time window (such as the propagation time corresponding to ±5 m at the corresponding position) after the transmission signal is received are received.

[0143] "Step S300: When each of the detection signals reaches the reflector 20 of the corresponding section, the reflector 20 of the corresponding section is excited to resonate through the electromagnetic coupling effect between the rectangular copper foil 220 and the slot hole 131, so that the reflector 20 of the corresponding section generates a reflection signal with a characteristic frequency and transmits it reversely back to the cable body 10." Among them, the characteristic frequency should be approximately the resonant frequency of the reflector 20.

[0144] 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, exciting the reflector 20 to resonate. Since each reflector 20 has a specific resonance frequency, it will reflect a specific signal frequency and transmit this reflected signal back to the main body of the leaky cable in the reverse direction. 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 between the rectangular copper foil 220 and the slot 131) ensures the effective reflection of the signal. The dimensions and positions of the copper foil and the slot 131 need to be precisely controlled to ensure the correct resonance is excited on each reflector 20.

[0145] "Step S400: The signal receiver monitors the reflected signals in the cable main body 10 in real time, samples and analyzes the spectrum of each reflected signal, and records the signal peak intensity at each characteristic frequency." This step is for the acquisition and analysis of the reflected signals.

[0146] In this step, the reflected signals are monitored in real time by the signal receiver. The signal receiver captures and records the reflected signals transmitted in the leaky cable. Through a spectrum analyzer, the spectrum of the reflected signals is sampled in real time, especially recording the signal peak intensity at the characteristic frequencies corresponding to each reflector 20. The reflected signal of each reflector 20 has specific frequency characteristics, 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 points of the leaky cable be effectively detected. The spectrum analysis method should be able to distinguish the signal peak intensities at different frequencies.

[0147] Step S400 specifically includes the following steps:

[0148] The signal receiver acquires the reflected signals at a target sampling rate (e.g., ≥10 GS / s) and generates a spectrogram through fast Fourier transform. It should be noted that the frequency resolution ≤1 MHz.

[0149] Set a monitoring bandwidth (such as ±5 MHz) for the characteristic frequencies corresponding to each reflector 20 and extract the peak intensity within this frequency band.

[0150] Furthermore, the peak intensity can be normalized, and path loss compensation can be performed on the received signal intensity. The compensation formula is as follows:

[0151]

[0152] Where:

[0153] : The compensated received signal strength (normalized signal strength), which represents the signal strength value after considering path loss.

[0154] : The original received signal strength, which represents the received signal strength without path loss compensation.

[0155] : The actual propagation distance of the received signal, in meters (m), that is, the actual distance from the signal transmitter to the receiving point.

[0156] : The reference distance (usually the spacing value between two adjacent reflectors 20), that is, the signal strength received at this distance is used as a benchmark for normalization.

[0157] : The 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 reflected in logarithmic form.

[0158] The above formula is based on the logarithmic path loss model, considering that the signal will gradually attenuate as the distance increases during propagation. The logarithmic model enables the path loss to reasonably reflect the attenuation law in actual communication. In most wireless communication applications, the relationship between signal strength and distance shows logarithmic characteristics, that is, the signal strength decreases inversely with the square of the distance. For unified comparison or calculation, the received signal strength is usually normalized to eliminate the influence of distance.

[0159] Through path loss compensation, the above formula can convert the signal strengths at different distances into unified normalized signal strengths, which can more conveniently compare the signal strengths in different positions and environments. Moreover, the formula accurately reflects the law of signal attenuation with increasing distance in logarithmic form, which conforms to the actual situation of wireless propagation.

[0160] In summary, 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 normalized, facilitating subsequent analysis and processing.

[0161] "Step S500: If the characteristic frequency of a certain segment 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 there is a fault in that segment of the leaky cable; where the detection spectrum is the mapping relationship table between each reflector 20 and the corresponding resonant frequency, and the threshold range is the allowable change range of the peak value of the reflected signal corresponding to each reflector 20 in the normal state of the leaky cable." This step is for fault determination and location.

[0162] In this step, the measured reflection signal spectrum is compared with a preset standard spectrum (i.e., the spectrum under normal conditions). If the characteristic frequency of a certain section of the reflection signal does not appear in the detection spectrum, or its signal peak intensity is lower than the threshold range, it is determined that there may be a fault in that section of the leaky cable. The threshold range is set by the allowable change range of the reflection signal peak under normal leaky cable conditions. The key point is that the spectral characteristics under normal conditions and the changes under fault conditions can be determined by establishing a threshold range. The setting of the threshold range depends on the standard working conditions of the leaky cable, such as signal intensity, spectral distribution, etc. Through comparison with known fault types, accurate fault determination can be carried out.

[0163] Step S500 specifically includes the following steps:

[0164] If a certain characteristic frequency does not appear in the detection spectrum (such as the peak not being detected after multiple consecutive scans), mark that section as "suspected fault"; if the peak intensity is lower than the lower threshold, mark it as "attenuation fault".

[0165] Furthermore, the frequency of the adjacent reflector 20 can also be emitted to the suspected fault section to verify whether it is a frequency offset fault (such as the resonant frequency drifting due to water infiltration). Specific fault type identification can refer to Table 2.

[0166]

[0167] Table 2

[0168] Furthermore, it can also be optimized according to the corresponding application scenarios. For example:

[0169] In a tunnel environment, an anti-moisture design is added. The substrate 210 of the reflector 20 can use ceramic materials to reduce the influence of water vapor on the resonant frequency. And the detection signal emission interval is shortened to 5 ms to adapt to the multi-path reflection environment in the tunnel.

[0170] In a subway platform, narrow interval frequency allocation (5 MHz) is adopted, with a positioning accuracy of ±2 m, and it cooperates with the platform monitoring camera to quickly locate the fault point. And the leaky cable detection system can also be integrated with the BIM model to achieve three-dimensional visualization of the fault section.

[0171] Through the above 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.

[0172] In summary, the frequency of the reflector 20 should increase or decrease along the first direction of the leaky cable, providing an accurate reference for signal detection and fault location. The frequency scheduling function of the broadband 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 generating the reflected signal, ensuring the effective reflection of the signal. Precise spectrum analysis and signal peak intensity measurement can quickly identify leaky cable faults and determine the fault point by comparing with the standard spectrum.

[0173] The above content described in this specification is only an example of the present invention. Those skilled in the art to which the present invention pertains can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, as long as they do not deviate from the content of this specification of the present invention or exceed the scope defined by this claims, they should 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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