A spread spectrum leaky cable compatible with overcutoff frequency transmission tasks

Abstract

This invention provides a spread spectrum leaky cable compatible with over-cutoff frequency transmission tasks, comprising an inner conductor, an insulating layer, and an outer conductor coaxially nested from the inside out. The outer conductor has multiple slot arrays, each containing multiple rows of slot groups. Each row of slot groups consists of multiple pairs of radially arranged slots symmetrical about the same axial axis. The two slots forming any given pair have the same shape and size. The major axis length of the slot pairs in any row of slot groups gradually increases radially from both ends towards the axis of symmetry. By setting multiple pairs of slots radially symmetrical about the same axial axis and by setting the major axis length to increase radially from both ends towards the axis of symmetry, the instability problem of higher-order modes during over-cutoff frequency transmission is effectively mitigated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of communication cable, and particularly relates to a spread spectrum leaky cable compatible with super cut-off frequency transmission task. BACKGROUND

[0002] Leaky coaxial cable (referred to as leaky cable) is a composite communication medium with signal transmission and wireless transceiver functions. The leaky cable can realize directional radiation of electromagnetic wave energy and environmental signal reception through the periodic slotted structure preset on the outer conductor surface, thereby completing bidirectional information interaction. At present, the leaky cable technology has been maturely applied in the field of rail transit (such as subway tunnels, railway tunnels and other enclosed spaces) to provide stable mobile communication coverage for train passengers and on-board devices.

[0003] The existing leaky cable products for 4G and below medium and low frequency bands (such as 2.6GHz and below) mostly adopt a 13 / 8 type structure, and the theoretical cut-off frequency thereof is about 2.8GHz. The critical frequency (Cut-off Frequency) of the leaky cable refers to the highest frequency threshold at which the leaky cable maintains signal integrity in a single mode transmission state. When the frequency of the actual transmission signal exceeds this critical value, the leaky cable will cause multi-path interference and energy loss due to the excitation of high-order modes, resulting in deterioration of the communication link quality, which is difficult to meet the stringent communication requirements of low latency and high reliability in tunnel scenarios. Therefore, when facing the super cut-off frequency transmission task of 5G communication signals with a frequency of 3.5GHz and above, the 13 / 8 type leaky cable will cause signal degradation due to the excitation of high-order modes. Especially in the super-long tunnel environment where the 13 / 8 type leaky cable has been widely deployed, the existing infrastructure cannot directly adapt to the communication requirements of 5G high frequency bands, which becomes a technical bottleneck restricting 5G coverage in rail transit scenarios.

[0004] At present, when facing the above-mentioned super cut-off frequency transmission task, a down-conversion method is mostly used to convert the high-frequency 5G signal into a medium-frequency signal with a frequency lower than the cut-off frequency of the leaky cable, and then the leaky cable is used to transmit the medium-frequency signal, and then the on-board relay device of the train carriage running in the tunnel is used to up-convert the medium-frequency signal into a high-frequency signal with a target operating frequency, so as to use the existing leaky cable for 5G mobile communication transmission. However, although this scheme can temporarily solve the high-frequency support problem of the existing leaky cable, it has multiple limitations. The scheme needs to additionally configure a base station end down-converter and a vehicle-mounted relay up-conversion device, which not only greatly increases the hardware cost and volume, but also causes signal quality degradation due to the phase noise and frequency offset error introduced by the frequency conversion link, especially affecting the transmission accuracy of high-order modulation signals. The microsecond-level delay accumulated in the bidirectional frequency conversion process is also difficult to meet the demand of 5G ultra-low latency communication scenarios, and the method of compressing the bandwidth of the medium frequency band directly sacrifices the spectral utilization rate of the high-frequency signal, resulting in a decrease in network capacity. In addition, the train end relay device relies on the vehicle-mounted power supply and installation space, and has poor compatibility with old vehicles, lacking sustainability. SUMMARY

[0005] This invention provides a spread spectrum leaky cable compatible with over-cutoff frequency transmission tasks, which solves the defects of the prior art in transmitting high-frequency signals through down-conversion technology, which leads to increased hardware costs and interference with transmission accuracy and efficiency due to frequency conversion.

[0006] This invention provides a spread spectrum leaky cable compatible with overcutoff frequency transmission tasks, comprising an inner conductor, an insulating layer, and an outer conductor coaxially nested from the inside out;

[0007] The outer conductor is provided with an array of multiple slots;

[0008] Any slot array contains multiple rows of slot groups, each row of slot groups consists of multiple pairs of slots arranged radially and symmetrical about the same axial axis; the two slots that make up any slot pair have the same shape and size, and the length of the major axis of the slot pair in any row of slot groups gradually increases radially from both ends toward the axis of symmetry.

[0009] According to the present invention, a spread spectrum leaky cable compatible with overcutoff frequency transmission tasks is provided, wherein the total length of the slots in any column of slots in any slot array is less than half the circumference of the outer conductor; the total length of the slots in any column of slots is composed of the slot length of each slot in the column of slots and the slot gap length between adjacent slots.

[0010] According to the spread spectrum leaky cable compatible with over-cutoff frequency transmission tasks provided by the present invention, the slot length of the slots in any column of slots satisfies the following condition:

[0011] c / (12f(e r ) 1 / 2 ) <l i <c / (4f(e r ) 1 / 2 )-(iδ) / n

[0012] Where c is the propagation speed of electromagnetic waves in free space, f is the center frequency, and e r l is the relative permittivity of the insulating layer. i Let be the length of slot i, and δ be a correction factor, ranging from 0.5 to 10 mm.

[0013] According to the present invention, a spread spectrum leaky cable compatible with overcutoff frequency transmission tasks is provided, wherein the farther any slot array is from the signal transmitter, the longer the total length of the slots in any slot array group.

[0014] According to the present invention, a spread spectrum leaky cable compatible with over-cutoff frequency transmission tasks is provided, wherein the spacing between adjacent slot groups in any slot array satisfies the following condition:

[0015] Pdif =P / m(ξ+1)

[0016] Among them, P dif ξ is the spacing between adjacent slot groups in any slot array; P is the spacing between adjacent slot arrays; ξ is the number of slot groups in any slot array; m is the order of the target higher-order mode, which is the interference higher-order mode caused by the leaky cable when transmitting signals at over-cutoff frequencies.

[0017] The number of slot groups in any slot array is determined based on the following method:

[0018] Based on the current number of tests of slot groups in any slot array, the spacing between adjacent slot groups in the slot array is determined, and the standing wave ratio (SWR) at each leaky cable transmission frequency is calculated based on the current number of tests of slot groups in the slot array and the spacing between adjacent slot groups; the current number of tests of slot groups in the slot array is increased until the SWR at each leaky cable transmission frequency reaches the preset requirement, and the current number of tests of slot groups in the slot array is determined as the number of slot groups in the slot array.

[0019] According to the present invention, a spread spectrum leaky cable compatible with overcutoff frequency transmission tasks is provided, wherein the slots in any slot array are arranged at an angle relative to the axial direction; the inner conductor surface is provided with non-through cuts corresponding to each slot array; the axial width of the non-through cuts is the same as the total axial width of the corresponding slot array.

[0020] According to the present invention, a spread spectrum leaky cable compatible with overcutoff frequency transmission tasks is provided, wherein the opening direction of the non-through cut is at an angle of 0 degrees and / or 180 degrees to the opening direction of the central slot pair of the corresponding slot array.

[0021] According to the present invention, a spread spectrum leaky cable compatible with overcutoff frequency transmission tasks is provided, wherein the opening direction of the non-through cut is at an angle of 90 degrees and 270 degrees to the opening direction of the central slot pair of the corresponding slot array.

[0022] According to the present invention, a spread spectrum leaky cable compatible with overcutoff frequency transmission tasks is provided. When the opening direction of the non-penetrating cut is at a 0-degree angle to the opening direction of the central slot pair of the corresponding slot array, the length, width, and depth of the non-penetrating cut satisfy the condition that the inductance change of the region of the inner conductor where the non-penetrating cut is added is equal to the inductance change of the region of the outer conductor where the corresponding slot array is set. The inductance change of any slot array region is the sum of the inductance changes corresponding to all slots in the slot array. The inductance change corresponding to any slot is determined based on the angle of the slot relative to the axial direction, the slot length of the slot, the characteristic impedance per unit length of the leaky cable, the current propagation speed, and the radius of the outer conductor.

[0023] According to the present invention, a spread spectrum leaky cable compatible with overcutoff frequency transmission tasks is provided, wherein any slot array contains multiple rows of slot groups with different numbers of slots, and the slot groups with different numbers of slots are alternately arranged on the outer conductor.

[0024] This invention provides a spread spectrum leaky cable compatible with over-cutoff frequency transmission tasks, comprising an inner conductor, an insulating layer, and an outer conductor coaxially nested from the inside out. The outer conductor has multiple slot arrays, each containing multiple rows of slot groups. Each row of slot groups consists of multiple pairs of radially arranged slots symmetrical about the same axial axis. The two slots forming any given slot pair have the same shape and size. The major axis length of the slot pairs in any row of slot groups gradually increases radially from both ends towards the axis of symmetry. By setting multiple pairs of slots radially symmetrical about the same axial axis and by setting the major axis length to increase radially from both ends towards the axis of symmetry, the instability problem of higher-order modes during over-cutoff frequency transmission is effectively mitigated. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This is one of the schematic diagrams of the slot layout after the outer conductor is unfolded in the circumferential direction, provided by the present invention;

[0027] Figure 2 This is the second schematic diagram of the slot layout after the outer conductor is unfolded in the circumferential direction according to the present invention.

[0028] Figure 3 One of the cross-sectional schematic diagrams of the leaky cable provided by the present invention;

[0029] Figure 4 A second schematic cross-sectional view of the leaky cable provided by the present invention;

[0030] Figure 5 A schematic diagram of a slot structure provided for the prior art;

[0031] Figure 6 A schematic diagram of the attenuation curve of a leaky cable provided for existing technology;

[0032] Figure 7 A schematic diagram of the attenuation curve of the leaky cable provided by the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0034] Existing leaky cable products for 4G and below low-to-mid frequency bands (such as 2.6GHz and below) mostly adopt a 13 / 8 type structure, with a theoretical cutoff frequency of approximately 2.8GHz. When the actual transmission signal frequency exceeds this critical value, multipath interference and energy loss occur inside the leaky cable due to the excitation of higher-order modes, leading to a deterioration in communication link quality and making it difficult to meet the stringent communication requirements of low latency and high reliability in tunnel scenarios. Therefore, when facing the transmission of 5G communication signals above the cutoff frequency in the 3.5GHz and above frequency bands, this type of leaky cable will cause signal degradation due to the induction of higher-order modes. Especially in ultra-long tunnel environments where 13 / 8 type leaky cables have been deployed on a large scale, the existing infrastructure cannot directly adapt to the communication requirements of 5G high-frequency bands, becoming a technical bottleneck restricting 5G coverage in rail transit scenarios.

[0035] Currently, when facing the aforementioned transmission tasks above the cutoff frequency, the common approach is to downconvert the high-frequency 5G signal to an intermediate frequency (IF) signal with a frequency lower than the leaky cable cutoff frequency. This IF signal is then transmitted via the leaky cable, and subsequently, onboard relay equipment in the train carriages traveling through the tunnel upconverts the IF signal back to the target high-frequency signal, thus enabling 5G mobile communication transmission using the existing leaky cable. However, while this solution temporarily solves the high-frequency support problem of existing leaky cables, it has several limitations. This solution requires additional configuration of a downconverter at the base station and upconverter equipment on the onboard relay, significantly increasing hardware costs and size. Furthermore, the phase noise and frequency offset errors introduced during the conversion process degrade signal quality, particularly affecting the transmission accuracy of high-order modulation signals. The microsecond-level latency accumulated during the bidirectional conversion process is also insufficient to meet the requirements of 5G ultra-low latency communication scenarios. Compressing the IF band bandwidth directly sacrifices the spectrum utilization of high-frequency signals, leading to a decrease in network capacity. In addition, the train-side relay equipment relies on onboard power and installation space, has poor compatibility with older train models, and lacks sustainability.

[0036] To address this issue, this invention provides a spread spectrum leaky cable compatible with over-cutoff frequency transmission tasks, capable of effectively transmitting signals within and exceeding the cutoff frequency range. This improved leaky cable, through optimized outer conductor slot and inner conductor structures, can directly transmit high-frequency signals exceeding the current leaky cable's cutoff frequency. This solution stabilizes the high-order modes excited during over-cutoff frequency transmission by adjusting the outer conductor slot size gradient and distribution pattern, eliminating the need for external frequency conversion equipment and fundamentally eliminating noise superposition and delay accumulation problems caused by signal conversion, thus matching high real-time scenarios. Simultaneously, the leaky cable's direct transmission of native high-frequency signals maximizes spectral efficiency, providing greater communication capacity for tunnel environments. More importantly, this structural improvement only requires modification of the existing leaky cable itself, without upgrading train equipment, providing a smooth upgrade path of "one cable for multiple uses" for the evolution of rail transit communication systems.

[0037] Specifically, the leaky cable includes an inner conductor, an insulation layer, and an outer conductor that are coaxially nested from the inside out. Figure 1 This is one of the schematic diagrams of the slot layout after the outer conductor is unfolded in the circumferential direction, as provided by the present invention. Figure 1 As shown, the outer conductor 110 has a plurality of slot arrays 120.

[0038] Each slot array 120 contains multiple rows of slot groups 130, and each row of slot group 130 consists of multiple pairs of radially arranged slots that are symmetrical about the same axial direction (i.e., the leaky cable axial direction). For example... Figure 1As shown, the two slots that make up each slot pair 131, 132, 133, and 134 have the same shape and size; that is, slots 1311 and 1312 have the same shape and size, slots 1321 and 1322 have the same shape and size, slots 1331 and 1332 have the same shape and size, and slots 1341 and 1342 have the same shape and size. Furthermore, the two slots that make up each slot pair 131, 132, 133, and 134 are all symmetrical about the axial axis of symmetry Y. In addition, the length of the major axis of each slot pair in any row of slot groups 130 gradually increases radially from both ends towards the axis of symmetry. Taking slot pairs 131, 132, 133, and 134 as examples, the major axis lengths of slots 1311 and 1312 are less than the major axis lengths of slots 1321 and 1322, which are less than the major axis lengths of slots 1331 and 1332. Furthermore, the major axis lengths of slots 1331 and 1332 are less than the major axis lengths of slots 1341 and 1342. It should be noted that the angle between the major axis and the radial direction of the slot is smaller than the angle between the minor axis and the radial direction.

[0039] In some specific embodiments, the centers of the two slots in a slot pair may be slightly offset to the left or right in the radial direction, with an offset distance not exceeding 8mm.

[0040] Compared to Figure 5 The slot structure commonly used in the prior art shown in the figure is compared with... Figure 6 and Figure 7 ( Figure 6 and Figure 7In the diagram (where the horizontal axis represents frequency and the vertical axis represents attenuation), it can be seen that the embodiments of the present invention employ two complementary slot arrangement methods: first, by setting multiple pairs of slots radially symmetrical about the same axial axis; and second, by setting the length of the major axis to gradually increase radially from both ends towards the symmetrical axis. This results in a smoother attenuation curve compared to existing technologies. Therefore, the leaky cable provided by the embodiments of the present invention effectively alleviates the instability problem of higher-order modes during transmission above the cutoff frequency. Firstly, the slots on the outer conductor are arranged radially and symmetrically about the same axial axis. This symmetrical layout is equivalent to setting a perturbation structure to fix the electric field direction of higher-order modes, ensuring the stability of the cutting current in the circumferential direction. Symmetrical slot pairs enable a balanced distribution of the electromagnetic field in all directions, reducing excessive or insufficient local electromagnetic fields caused by asymmetry, thereby reducing unnecessary interference and coupling between higher-order modes. This balanced field distribution helps suppress higher-order modes that easily induce standing waves and local resonances, making the overall transmission more stable. Furthermore, the design incorporates slot pairs with their major axis length gradually increasing radially from both ends towards the axis of symmetry. This gradient design effectively creates a "trapezoidal" leakage characteristic on the leaky cable surface, causing the signal to converge towards the center, strengthening the signal intensity in the middle, and improving coverage. Simultaneously, the smaller slots at both ends appropriately limit high-frequency signal leakage, preventing premature attenuation; while the larger slots in the middle enhance leakage efficiency in the desired areas, resulting in a smoother axial energy distribution of the high-frequency signal within the leaky cable. This size gradient makes the signal leakage process more continuous and gradual, avoiding problems such as local impedance mismatch and excessive excitation of higher-order modes caused by abrupt changes in slot size.

[0041] More importantly, when these two settings are combined, they can exert a more significant control effect on higher-order modes. The radially symmetrical slot arrangement ensures the balance of the overall field distribution, while the gradual change in the major axis length allows the leakage characteristics to transition smoothly in different regions. This reduces local resonance phenomena and can selectively enhance or suppress leakage of specific modes. As a result, when the leaky cable transmits high-frequency signals such as 3.5G, which are higher than its cutoff frequency, the instability of higher-order modes is effectively controlled, and the signal transmission is more uniform and stable, while also meeting the coverage requirements of the entire frequency band.

[0042] In some optional embodiments, the total length of the slots in any column of slot groups 130 of any slot array 120 is less than half the circumference of the outer conductor. The total length of the slots in any column of slot groups 130 is composed of the lengths of the individual slots 1311, 1312, 1321, 1322, 1331, 1332, 1341, and 1342 in that slot group 130 (i.e., the length of the major axis of the slot) and the gap length between adjacent slots. Here, because the distribution of the electromagnetic field may have a specific symmetry in higher-order mode states, if the slot arrangement exceeds half the circumference of the outer conductor (and may also exceed half the wavelength), it may cover regions with opposite electric field directions, causing radiated or coupled electric fields to cancel each other out, thereby weakening the signal. Specifically, when the total length of the slots exceeds half the circumference, the phase of the electric field may be different at different positions along the circumferential direction. If the slot covers more than half the circumference, some slots may be located in the positive direction of the electric field, while others may be located in the negative direction, causing the radiation fields to cancel each other out and weakening the overall signal. Therefore, to avoid signal attenuation in higher-order modes, all slots in the slot group 130 of the slot array 120 are arranged within the half-circumference of the outer conductor. By limiting the total length of the slots to less than half the circumference, it can be ensured that all slots are located in a region with consistent electric field phase, thereby enhancing the radiation efficiency of the signal.

[0043] In some specific embodiments, in order to ensure signal combining degree and signal radiation efficiency, the slot length of slot i in any column of slots satisfies the following condition:

[0044] c / (12f(e r ) 1 / 2 ) <l i <c / (4f(e r ) 1 / 2 )-(iδ) / n(1)

[0045] Where c is the propagation speed of electromagnetic waves in free space, f is the center frequency, and e r l is the relative permittivity of the insulating layer. i Let be the length of slot i, and δ be a correction factor ranging from 0.1 to 10 mm.

[0046] In some optional embodiments, to determine the slot length of each slot in any row of slot groups, the total slot length of the slot group and the slot gap length between adjacent slots can be set first. Based on the already set total slot length and slot gap length of the slot group, the slot length of each slot pair can be determined sequentially radially from both ends towards the axis of symmetry. Taking slot pairs 131, 132, 133, and 134 as an example, the slot lengths of slots 1311 and 1312, slots 1321 and 1322, slots 1331 and 1332, and slots 1341 and 1342 are determined sequentially. The effective total length of the slots (the sum of the slot lengths of each corresponding slot) can be determined based on the total slot length of the slot group and the slot gap length between adjacent slots. When determining the slot length of the current slot-aligned slot, the upper and lower limits of the slot length of the slot-aligned slot can be determined based on equation (1). Combining the effective total length of the slot and the known slot length of the slot-aligned slot, a suitable value can be selected from the upper and lower limits as the slot length of the current slot-aligned slot.

[0047] In other specific embodiments, the length of a single slot along its minor axis (referred to as the slot width) is 0.5-8 mm.

[0048] In some alternative embodiments, such as Figure 2 As shown, the farther any slot array is from the signal transmitter, the longer the total length of the slots in the slot array group. Since the system loss of high-frequency signals is aggravated in higher-order mode states, this design can be used to balance the system loss of high-frequency signals during transmission in leaky cables, thereby improving signal transmission performance.

[0049] In some alternative embodiments, the spacing between adjacent slot groups in any slot array satisfies the following condition:

[0050] P dif = P / m(ξ+1) (2)

[0051] Among them, P dif Let ξ be the spacing between adjacent slot groups in the slot array; P be the spacing between adjacent slot arrays; ξ be the number of slot groups in the slot array; and m be the order of the target higher-order mode. This target higher-order mode is an interference higher-order mode caused by the leaky cable transmitting signals above the cutoff frequency, i.e., a higher-order mode that interferes with and is detrimental to high-frequency signal transmission, such as the -2nd order mode. By determining the spacing between adjacent slot groups in the slot array in this way, higher-order modes that are detrimental to high-frequency signal transmission can be suppressed, further improving the stability of higher-order modes.

[0052] In some specific embodiments, the number of slot groups in any slot array can be determined based on the following method:

[0053] Based on the current number of tests of slot groups in any slot array, the spacing between adjacent slot groups in the slot array is determined using equation (2), and the standing wave ratio (SWR) at each leaky cable transmission frequency is calculated based on the current number of tests of slot groups in the slot array and the spacing between adjacent slot groups. Then, the current number of tests of slot groups in the slot array is increased, and the SWR at each leaky cable transmission frequency is calculated according to the above steps until the SWR at each leaky cable transmission frequency reaches the preset requirement. At this time, the current number of tests of slot groups in the slot array can be determined as the number of slot groups in the slot array.

[0054] When leaky cables transmit high-frequency signals above the cutoff frequency, higher-order modes are inevitably excited. These higher-order modes are excited and propagate strongly on the smooth inner conductor surface, causing local standing waves or resonances in certain areas. This results in uneven signal energy distribution and degrades the voltage standing wave ratio (VSWR). Furthermore, the uniformity of the inner conductor surface easily leads to strong interference and coupling between higher-order modes. This instability of higher-order modes causes uneven signal transmission, affecting the coverage and reliability of the communication system.

[0055] Therefore, in some optional embodiments, the slots in the slot array 120 are inclined relative to the axial direction, that is, the angle between the long axis of the slot and the axial direction of the leaky cable is greater than 0 degrees and less than 180 degrees. Based on this, the inner conductor surface is provided with non-through cuts corresponding to each slot array. The axial width of the non-through cut is the same as the total axial width of the corresponding slot array. By providing non-through cuts corresponding to each slot array on the inner conductor surface, perturbations are added, which helps to stably excite higher-order modes during signal transmission above the cutoff frequency.

[0056] Specifically, in an uncut inner conductor, the current is distributed uniformly along the conductor. When a non-penetrating notch is added to the surface of the inner conductor, this notch can be understood as a radially non-through groove formed on the surface of the inner conductor. This notch disturbs the local current and magnetic field distributions. This disturbance is usually small and can therefore be considered a perturbation of the system. On the one hand, the non-penetrating notch forms a local groove on the surface of the inner conductor, allowing the current to bypass in that region, thereby changing the original uniform current distribution. This bypassing effect can interrupt or weaken the over-excitation of higher-order modes in specific regions, reduce local impedance abrupt changes and reflection phenomena, and thus make the energy distribution of higher-order modes in the overall transmission more uniform and smoother. Simultaneously, the perturbation introduced by the non-penetrating notch can change the local electromagnetic field distribution, reduce the interaction between certain modes, and make it less likely for strong coupling and interference to occur between different higher-order modes. On the other hand, by setting non-penetrating cuts on the surface of the inner conductor, the micro-perturbations brought about by the cuts can break the continuity of the inner conductor surface, thereby disrupting the resonance conditions of higher-order modes and making the excitation of higher-order modes more dispersed and stable.

[0057] In some specific embodiments, Figure 3 One of the cross-sectional schematic diagrams of the leaky cable provided by the present invention is shown below. Figure 3 As shown, the opening direction of the non-through cut 310 forms an angle of 0 degrees and / or 180 degrees with the opening direction of the central slot pair 320 of the corresponding slot array. Wherein, as... Figure 3 As shown in the schematic diagram on the left, from the perspective of the cross-section of the leaky cable, a non-through cut 310 can be made at the position of the inner conductor directly opposite the central slot pair 320 of the slot array, such that the opening direction of the non-through cut 310 forms a 0-degree angle with the opening direction of the corresponding central slot pair 320 of the slot array; for example Figure 3 As shown in the middle schematic diagram, from the cross-sectional perspective of the leaky cable, a non-through cut 310 can be made at the position of the central slot pair 320 of the slot array opposite to the inner conductor, such that the opening direction of the non-through cut 310 forms a 180-degree angle with the opening direction of the corresponding central slot pair 320 of the slot array; for example Figure 3 As shown in the schematic diagram on the right, from the perspective of the cross-section of the leaky cable, non-penetrating cuts 310 can be made at the positions of the central slot pair 320 of the slot array facing the inner conductor and facing away from it, respectively, so that the opening directions of the two non-penetrating cuts 310 form angles of 0 degrees and 180 degrees with the opening directions of the central slot pair 320 of the corresponding slot array, respectively.

[0058] In other specific embodiments, Figure 4 This is the second schematic diagram of the cross-section of the leaky cable, as shown below. Figure 4As shown, the opening direction of the non-penetrating cut 410 forms angles of 90 degrees and 270 degrees with the opening direction of the central slot pair 420 of the corresponding slot array. That is, from the perspective of the cross-section of the leaky cable, a non-penetrating cut 410 can be set on the side of the inner conductor, such that the opening directions of the two non-penetrating cuts 410 form angles of 90 degrees and 270 degrees with the opening direction of the central slot pair 420 of the corresponding slot array, respectively. The field distribution of higher-order modes will exhibit changes in circumferential current and electric field under different modes. By setting non-penetrating cuts with opening directions forming angles of 90 degrees and 270 degrees with the opening direction of the central slot pair 420 of the corresponding slot array, the resonance conditions of these modes can be disrupted, thereby reducing the standing wave effect and making the mode distribution more uniform, thus reducing the instability of higher-order mode transmission. In addition, under higher-order modes, certain specific resonant modes can lead to local accumulation of signal energy, resulting in unnecessary mode interference and loss. This cutting method can disrupt the formation of these resonant modes, reduce signal loss, and improve transmission efficiency.

[0059] For cases where the opening direction of the non-through cut is at a 0-degree angle to the opening direction of the central slot pair of the corresponding slot array, the problem of local standing waves and voltage standing wave ratio deterioration in higher-order modes requires further setting of the cut size (radial length and depth relative to the inner conductor surface) to suppress reflected waves generated at each slot position and optimize the voltage standing wave ratio.

[0060] Specifically, due to the angled slots, the current on the outer conductor experiences a longer current path and increased inductance as it passes through the slot array, causing characteristic impedance interference in each slot. This interference can degrade the voltage standing wave ratio (VSWR) at the slot. Considering that the current bypasses the slot after the non-through-slot is installed, the increased bypass path is equivalent to adding an additional inductance, which can be considered a series inductance, affecting the overall transmission characteristics. Therefore, the size of the non-through-slot can be adjusted so that the additional inductance added by the inner conductor current bypassing the slot cancels out the inductance added by the outer conductor current passing through the slot, thus eliminating characteristic impedance interference in the slot. Specifically, the length, width, and depth of the non-through-slot must satisfy the following condition: the change in inductance in the area of ​​the inner conductor with the added non-through-slot is equal to the change in inductance in the area of ​​the outer conductor with the corresponding slot array.

[0061] The inductance change of any region in the slot array is the sum of the inductance changes of all slots in the array. The inductance change of any single slot is determined based on the slot's angle relative to the axis, the slot length, the characteristic impedance per unit length of the leaky cable, the current propagation velocity, and the radius of the outer conductor. The inductance change of any single slot can be calculated using the following formula:

[0062]

[0063] Where ΔC is the capacitance change corresponding to the slot, ΔL is the inductance change corresponding to the slot, S is the slot length, θ is the angle between the slot and the axis, Z0 is the characteristic impedance per unit length of the leaky cable, and V c Let r be the velocity of current propagation and r be the radius of the outer conductor.

[0064] Those skilled in the art should understand that, in the disclosure of this invention, the terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the system or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0065] In the description of this specification, references to "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A spread spectrum leaky cable compatible with a super cutoff frequency transmission task, characterized in that, The coaxial cable comprises an inner conductor, an insulation layer and an outer conductor which are coaxially nested from inside to outside; The outer conductor is provided with a plurality of slot hole arrays; Each slot hole array comprises a plurality of slot hole groups, and each slot hole group comprises a plurality of slot hole pairs which are radially arranged along the length direction and axially symmetric about the same leaky cable axial symmetry axis; the two slot holes of each slot hole pair are of the same shape and size, and the long axis length of the slot hole pairs in each slot hole group gradually increases from both ends to the axial symmetry axis direction.

2. The spread spectrum leaky cable compatible with transmission tasks of ultra- cutoff frequency according to claim 1, characterized in that, The total length of the slot holes in any slot hole group of any slot hole array is less than half of the circumference of the outer conductor; the total length of the slot holes in the slot hole group is composed of the slot hole length of each slot hole in the slot hole group and the slot hole gap length between adjacent slot holes.

3. A spread spectrum leaky cable compatible with transmission tasks of ultra- cutoff frequency according to claim 2, characterized in that, The farther the distance between any slot hole array and the signal transmitting end, the longer the total length of the slot holes in the slot hole group of the slot hole array.

4. A spread spectrum leaky cable compatible with transmission tasks of ultra- cutoff frequency according to claim 1, characterized in that, The distance between adjacent slot hole groups in any slot hole array satisfies the following condition: P dif = P / m(ξ+1) wherein P dif is the pitch between adjacent groups of slots in any of the slot arrays; P is the pitch of adjacent slot arrays; ξ is the number of groups of slots in any of the slot arrays; m is the order of a target high-order mode, the target high-order mode being an interfering high-order mode induced by the leaky cable when transmitting an over-cutoff frequency signal; The number of slot hole groups in any slot hole array is determined in the following manner: Based on the current test number of slot hole groups in any slot hole array, the distance between adjacent slot hole groups in the slot hole array is determined, and the standing wave ratio under each leaky cable transmission frequency is calculated based on the current test number of slot hole groups in the slot hole array and the distance between adjacent slot hole groups; the current test number of slot hole groups in the slot hole array is increased until the standing wave ratio under each leaky cable transmission frequency meets the preset requirement, and the current test number of slot hole groups in the slot hole array is determined as the number of slot hole groups in the slot hole array.

5. The spread spectrum leaky cable compatible with transmission tasks of ultra- cutoff frequency according to claim 1, characterized in that, The slot holes in any slot hole array are arranged obliquely relative to the axial direction; the inner conductor surface is provided with a non-through cut corresponding to each slot hole array.

6. A spread spectrum leaky cable compatible with transmission tasks of ultra- cutoff frequency according to claim 5, characterized in that, The opening direction of the non-through cut forms an angle of 0 degrees and / or 180 degrees with the opening direction of the central slot hole pair of the corresponding slot hole array; wherein the non-through cut is arranged at the position of the inner conductor directly opposite the central slot hole pair of the corresponding slot hole array, so that the opening direction of the non-through cut forms an angle of 0 degrees with the opening direction of the central slot hole pair of the corresponding slot hole array; the non-through cut is arranged at the position of the inner conductor away from the central slot hole pair of the corresponding slot hole array, so that the opening direction of the non-through cut forms an angle of 180 degrees with the opening direction of the central slot hole pair of the corresponding slot hole array.

7. A spread spectrum leaky cable compatible with transmission tasks of ultra- cutoff frequency according to claim 5, characterized in that, The opening direction of the non-through cut forms an angle of 90 degrees and / or 270 degrees with the opening direction of the central slot hole pair of the corresponding slot hole array; wherein one non-through cut is arranged on each side of the inner conductor, so that the opening direction of the two non-through cuts forms an angle of 90 degrees and / or 270 degrees with the opening direction of the central slot hole pair of the corresponding slot hole array, respectively.

8. A spread spectrum leaky cable compatible with transmission tasks of ultra- cutoff frequency according to claim 6, characterized in that, When the opening direction of the non-through cut forms a 0-degree angle with the opening direction of a corresponding central slot hole pair of the slot hole array, the length, width, and depth of the non-through cut satisfy the condition that the inductance variation of the region where the inner conductor is additionally provided with the non-through cut is equal to the inductance variation of the region where the outer conductor is provided with the corresponding slot hole array; the inductance variation of the region of any slot hole array is the sum of the inductance variations corresponding to all slot holes in the any slot hole array, and the inductance variation corresponding to any slot hole is determined based on the angle of the any slot hole relative to the axial direction, the slot hole length of the any slot hole, the characteristic impedance and current propagation speed of the leaky cable per unit length, and the radius of the outer conductor.

9. The spread spectrum leaky cable compatible with transmission tasks of ultra- cutoff frequency according to claim 1, characterized in that, The any slot hole array includes slot hole groups with different numbers of slot holes in different columns, and the slot hole groups with different numbers of slot holes are alternately arranged on the outer conductor.

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