Broadband low-loss leaky coaxial cable

Abstract

The application discloses a wide-band low-loss leak coaxial cable, which comprises a spiral corrugated copper tube inner conductor layer, a high-physical-foaming insulation layer, a slotted hole outer conductor layer, a tape layer and a flame-retardant outer protective layer which are coaxially arranged from inside to outside; the spiral corrugated copper tube inner conductor layer is formed by longitudinally wrapping and welding high-purity red copper strips into a smooth copper tube and then rolling the smooth copper tube into a spiral corrugated copper tube by a corrugating machine; the high-physical-foaming insulation layer is coaxially nested on the outer side of the spiral corrugated copper tube inner conductor layer, and the high-physical-foaming insulation layer is formed by injecting a mixture of carbon dioxide and octafluorocyclobutane into molten polyethylene insulation material with azodicarbonamide as a nucleating agent. The application breaks through the traditional leak cable TEM single-mode transmission cutoff limit by matching the high-foaming low-loss insulation with the composite gradually-changing rectangular slot array structure, effectively offsets the TE high-order harmonic interference, eliminates the high-frequency band attenuation resonance peak, greatly reduces the transmission loss and can stably bear full-mode mobile communication signals.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and in particular to a wideband, low-loss, leaky coaxial cable. Background Technology

[0002] Currently, leaky coaxial cables are mainly used in enclosed environments such as subways, high-speed railways, highway tunnels, large underground stadiums, and mines. They function as both transmission lines and antennas, evenly radiating wireless signals, making them the optimal choice for wireless coverage in tunnel scenarios. With the implementation of the national "5G Application 'Sailing' Action Plan" and the Ministry of Industry and Information Technology's "Signal Upgrading" special action, 5G-A deep coverage construction is being comprehensively promoted in subway and high-speed railway tunnels across China. The 4.9GHz band, with its ultra-large bandwidth of 160MHz, has been designated as a key spectrum for expansion to improve user communication speeds and capacity.

[0003] Under current technology, the leaky coaxial cable used for wireless coverage in rail transit tunnels can only support signals up to 3.5GHz. At higher 5G frequency bands, the attenuation curve has obvious resonance peaks and high-order mode interference, resulting in large transmission attenuation over 100 meters and coupling loss fluctuations exceeding 10dB. This cannot meet the requirements for implementation in rail transit projects, and there is a significant technological gap in the industry. Therefore, it cannot support 5G higher frequency band communication services.

[0004] Against this backdrop, there is an urgent need for a new type of wideband, low-loss leaky coaxial cable that extends the frequency of existing leaky coaxial cables used in public mobile communications to 5GHz, while also accommodating the full frequency band signals of 1.8G / 2.6G / 3.5G / 4.9G for 5G mobile communications by operators. This would fill a gap in the industry and solve the problem of high-capacity 5G-A wireless coverage in subways and high-speed rail tunnels. Summary of the Invention

[0005] The purpose of this invention is to provide a wideband, low-loss, leaky coaxial cable that can meet the requirements of 3.5GHz signals and simultaneously support higher frequency 5G communication services, thereby improving signal coverage.

[0006] The technical solution adopted in this invention is as follows:

[0007] A broadband low-loss leaky coaxial cable includes a spiral corrugated copper tube inner conductor layer, a high physical foam insulation layer, a slotted outer conductor layer, a wrapping layer, and a flame-retardant outer sheath layer arranged coaxially from the inside to the outside.

[0008] The inner conductor layer of the spiral corrugated copper tube is made of high-purity copper strip longitudinally wrapped and welded into a smooth copper tube, and then rolled into a spiral corrugated copper tube by a corrugating machine.

[0009] The high physical foam insulation layer is coaxially nested on the outside of the inner conductor layer of the spiral corrugated copper tube. The high physical foam insulation layer uses azodicarbonamide as a nucleating agent and injects a mixture of carbon dioxide and octafluorocyclobutane into the molten polyethylene insulation material to form an insulation layer with high strength, high foaming degree, and uniform fine cell structure, with a foaming degree of over 83%.

[0010] The ratio of the azodicarbonamide nucleating agent to the foamed polyethylene insulation material is 1-2:100. The foamed polyethylene insulation material is composed of high-density foamed polyethylene and low-density foamed polyethylene, and the ratio of high-density foamed polyethylene to low-density foamed polyethylene is 55-75:25-45.

[0011] The ratio of carbon dioxide to octafluorocyclobutane gas is 50-70:30-50.

[0012] The slotted outer conductor layer is longitudinally wrapped around the outer surface of the insulation layer, specifically comprising a high-purity copper strip. The copper strip has slots formed on it, and these slots are composed of several groups of slots arranged in an array with a period P along the cable length and perpendicular to the cable axis. The range of the array period P is:

[0013] ;

[0014] in, The equivalent relative permittivity of the insulating layer is... For the period of the slot array, It is a non-zero positive integer. The speed at which light travels in a vacuum; The minimum operating frequency for a leaky coaxial cable.

[0015] The slot group consists of multiple rectangular slot groups of unequal lengths arranged along the cable axis and perpendicular to the cable length direction. The unequal length rectangular slot groups include a first unequal length rectangular slot group and a second unequal length rectangular slot group that is symmetrically transformed from the center of the first unequal length rectangular slot group. The center interval between the first unequal length rectangular slot group and the second unequal length rectangular slot group is 2P / 3. The first unequal length rectangular slot group consists of a long rectangular slot group and a short rectangular slot group, and the long rectangular slot group and the short rectangular slot group are arranged vertically and intersecting each other. The vertical interval between the center of the long rectangular slot group and the center of the short rectangular slot group is P / 10.

[0016] The center-to-center distance between the first and second slots in the long rectangular slot group is P / 12, the center-to-center distance between the second and third slots is P / 24, and the center-to-center distance between the third and fourth slots is P / 8; the center-to-center distance between the first and second slots in the short rectangular slot group is P / 12, the center-to-center distance between the second and third slots is P / 24, and the center-to-center distance between the third and fourth slots is P / 8.

[0017] The long rectangular slots are 9-15mm long and 2-4mm wide, the short rectangular slots are 5-8mm long and 2-4mm wide, and the gap between all groups of long rectangular slots and groups of short rectangular slots is 2-4mm.

[0018] The four corners of the long rectangular slot and the short rectangular slot are rounded, and the radius of the rounded corner can be 0.5-1.5mm.

[0019] Electromagnetic wave signals are transmitted in the broadband low-loss leaky coaxial cable in conventional TEM mode and high-order TE mode, at frequencies lower than [missing information]. At that time, it transmits in TEM mode at a frequency higher than [previous frequency]. At that time, transmission is performed in TE mode. The time can be obtained from the following formula:

[0020]

[0021] in, The equivalent diameter of the outer conductor layer. The equivalent diameter of the inner conductor layer. is the equivalent relative permittivity of the insulating layer.

[0022] The flame-retardant outer sheath is provided with slot markings to facilitate the installation and laying of the leaky cable. The slot markings are located at a position 180° relative to the slots on the outer surface of the outer sheath, with the raised sheath ribs serving as marking lines. There may be one or two marking lines.

[0023] This invention overcomes the traditional leaky cable's TEM single-mode transmission cutoff limitation by combining high-foaming, low-loss insulation with a composite gradient rectangular slot array structure. It effectively cancels TE high-order harmonic interference and eliminates high-frequency attenuation resonance spikes, significantly reducing transmission loss. It can stably carry 1.8G / 2.6G / 3.5G / 4.9GHz full-mode mobile communication signals, addressing the pain point that existing leaky cables only support 3.5GHz and below frequency bands and cannot adapt to the ultra-large bandwidth expansion spectrum of 5G. Furthermore, this invention employs a cross-arrangement structure of long and short rectangular slots, allowing for gradual adjustment of slot length and width parameters along the cable length. Simultaneously optimizing the center spacing of the transverse and longitudinal slots to match harmonic suppression theory, it can control the overall coupling loss fluctuation within 5dB, far superior to the fluctuation index of over 10dB in existing leaky cables. Furthermore, the insulation layer uses high-density and low-density polyethylene, combined with a two-component mixed foaming gas, achieving a foaming degree of over 83%. The foam cells are fine and uniform, with a stable and controllable equivalent dielectric constant, which can mitigate the additional losses caused by high-frequency electric field distortion. Simultaneously, it improves the mechanical strength and extrusion resistance of the insulation, resulting in a longer service life. Finally, the rounded corners of the rectangular grooves in this invention reduce the stress during copper strip grooving, minimizing outer conductor cracking and deformation, and improving mass production yield and long-term cable reliability. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0026] Figure 2 This is a schematic diagram of the slot arrangement within a single slot array cycle as described in this invention;

[0027] Figure 3 This is a schematic diagram of a group of rectangular slots of unequal length within a period of a slot array as described in this invention;

[0028] Figure 4 This is a schematic diagram of a group of rectangular slots of unequal length within a period of a slot array as described in this invention;

[0029] Figure 5 This is a system loss curve of a 300-meter leaky coaxial cable in Embodiment 1 of the present invention at 4.9 GHz;

[0030] Figure 6This is a system loss curve of a 300-meter leaky coaxial cable in Embodiment 2 of the present invention at 4.9 GHz. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] like Figure 1 , 2 As shown in Figure 3, in Embodiment 1, the present invention comprises, from the inside out, a spiral corrugated copper tube inner conductor layer 1, a high-physical-foamed insulation layer 2, a slotted outer conductor layer 3, a wrapping layer 4, and a flame-retardant outer sheath 5, arranged coaxially. Specifically, the leaky coaxial cable provided in this embodiment innovatively adopts two major modules: a high-physical-foamed low-loss dielectric insulation system and a composite gradient slotted array outer conductor, coupled with a high-precision laser continuous slotting fabrication process. The overall structural dimensions meet industry standards and can directly replace existing leaky cables used in tunnels.

[0033] Specifically, in this embodiment, the inner conductor layer 1 of the spiral corrugated copper tube is made by longitudinally welding high-purity copper strips into a smooth copper tube, and then rolling it into a spiral corrugated copper tube by a corrugating machine.

[0034] In this embodiment, the high physical foaming insulation layer 2 is coaxially nested on the outside of the inner conductor 1. The insulation layer 2 uses azodicarbonamide as a nucleating agent, and carbon dioxide and octafluorocyclobutane are mixed and injected into the molten polyethylene insulation material to form an insulation layer 2 with high strength, high foaming degree, and uniform fine cell structure. Its foaming degree can reach more than 83%.

[0035] The azodicarbonamide nucleating agent is mixed with the foamed polyethylene insulation material in a ratio of 1-2:100. The foamed polyethylene insulation material is composed of high-density foamed polyethylene and low-density foamed polyethylene, with an optional ratio of 55-75:25-45. The ratio of carbon dioxide and octafluorocyclobutane gas is 50-70:30-50. Traditionally, a single carbon dioxide foaming method is used, which is easier to achieve in terms of cell formation and lower cost. However, the rapid gas diffusion rate can easily lead to uneven cell size, thus affecting high-frequency standing wave stability. This patent provides a foaming method using a mixture of carbon dioxide and octafluorocyclobutane gases, which effectively inhibits cell growth and merging, resulting in more uniform and finer cells, a more stable equivalent dielectric constant, and a significantly higher degree of foaming compared to traditional methods, thus significantly reducing dielectric loss at high frequencies. In this embodiment, the ratio of azodicarbonamide (nucleating agent) to foamed polyethylene insulation material is 1.5:100. The foamed polyethylene insulation material is composed of high-density foamed polyethylene and low-density foamed polyethylene, with a ratio of 70:30. Optionally, the ratio of carbon dioxide and octafluorocyclobutane gas is 55:45.

[0036] like Figure 2 The slotted outer conductor layer 3 provided in this embodiment is made of high-purity copper strip longitudinally wrapped around the outer surface of the insulation layer 2 after passing through slots 30. The slots 30 are composed of a plurality of slot groups 31 arrayed along the cable length direction with a period P. The range of the array period P of the slot group 31 is:

[0037] ;

[0038] in, The equivalent relative permittivity of insulating layer 2 is given in this embodiment. The range is 1.2 to 1.25. For the 31-slot array period, It is a non-zero positive integer. The speed at which light travels in a vacuum; The minimum operating frequency for a leaky coaxial cable.

[0039] like Figure 2 In this embodiment, the slot group 31 is composed of multiple rectangular slot groups of unequal lengths with axes perpendicular to the cable length direction. The unequal-length rectangular slot groups consist of a first unequal-length rectangular slot group 311 and a second unequal-length rectangular slot group 312, with a center-to-center spacing of 2P / 3 between the first unequal-length rectangular slot group 311 and the second unequal-length rectangular slot group 312. This spacing can stagger the harmonic radiation phase of the two sets of slots, suppress resonant attenuation spikes, and improve the voltage standing wave ratio (VSWR) across the entire frequency band.

[0040] like Figure 3In this embodiment, the first unequal-length rectangular slot group 311 is composed of a long rectangular slot group 3111 and a short rectangular slot group 3112. The center-to-center spacing between the first and second slots in the long rectangular slot group 3111 is P / 12, between the second and third slots is P / 24, and between the third and fourth slots is P / 8. Similarly, the center-to-center spacing between the first and second slots in the short rectangular slot group 3112 is P / 12, between the second and third slots is P / 24, and between the third and fourth slots is P / 8. This non-uniformly spaced slot center-to-center spacing can suppress high-order harmonic components generated by the slot array itself, broaden the effective operating bandwidth, weaken inter-mode coupling interference in the high-frequency band, and balance low-frequency radiation efficiency with optimized high-frequency radiation uniformity.

[0041] like Figure 4 In this embodiment, the second unequal-length rectangular slot group 312 is composed of a short rectangular slot group 3121 and a long rectangular slot group 3122. The center-to-center spacing between the first and second slots in the short rectangular slot group 3121 is P / 8, between the second and third slots is P / 24, and between the third and fourth slots is P / 12. Similarly, the center-to-center spacing between the first and second slots in the long rectangular slot group 3122 is P / 8, between the second and third slots is P / 24, and between the third and fourth slots is P / 12. This slot spacing is phase-complementary to the first unequal-length rectangular slot group, further canceling array harmonics, widening the operating bandwidth, and reducing coupling loss fluctuations with frequency.

[0042] In this embodiment, the long rectangular slot group and the short rectangular slot group of the first unequal length rectangular slot group 311 and the second unequal length rectangular slot group 312 are arranged vertically and horizontally, which can avoid the local strength reduction of the outer conductor caused by the same side arrangement, and at the same time, the radiation field is more evenly distributed in the circumferential direction of the cable.

[0043] In this embodiment, the vertical spacing between the centers of the long rectangular slot group 311 and the short rectangular slot group 312 is P / 10. This allows for adjustment of the mutual coupling effect between the slots, balancing coupling loss and transmission loss, and further suppressing high-order resonances generated by the slots.

[0044] In this patent, all elongated rectangular slots in the slot group have a length of 9–15 mm and a width of 2–4 mm. All short rectangular slots in the slot group have a length of 5–8 mm and a width of 2–4 mm. Specifically, in this embodiment, all elongated rectangular slots in slot group 31 have a length of 10 mm and a width of 2.5 mm, and all short rectangular slots in slot group 31 have a length of 6 mm and a width of 3 mm. The slot dimensions provided in this embodiment exhibit low field strength fluctuations and stable signals within the high-frequency range of 3300MHz–4900MHz, demonstrating excellent overall loss. The combination of long and short slots balances low-frequency coupling efficiency and low-frequency attenuation performance within an ultra-wideband range.

[0045] Optionally, in the slot group, the gap between all long rectangular slot groups and short rectangular slot groups is 2-4 mm. In this embodiment, the gap between the top and bottom of all long rectangular slot groups and short rectangular slot groups in the slot group 31 is 2.5 mm. This gap ensures that the outer conductor of the copper strip retains sufficient mechanical connection strength after slotting, preventing breakage at the slotting position, and at the same time, it can adjust the electromagnetic coupling and attenuation degree between slots.

[0046] In this embodiment, the four corners of the long rectangular slot and the short rectangular slot are rounded with a radius of 1mm. The rounded corners can eliminate stress concentration points at the four corners of the rectangular slot, reduce copper strip cracking and warping defects after laser grooving, and improve the mass production qualification rate.

[0047] In this embodiment, the electromagnetic wave signal is transmitted in the broadband low-loss leaky coaxial cable in conventional TEM mode and high-order TE mode, with a frequency lower than [missing information]. At that time, it transmits in TEM mode at a frequency higher than [previous frequency]. At that time, transmission is performed in TE mode. It can be derived from the following formula:

[0048]

[0049] in, The equivalent diameter of the outer conductor layer 3 is given. The equivalent diameter of inner conductor layer 1 is given. is the equivalent relative permittivity of insulating layer 2.

[0050] The wrapping layer 4 is disposed between the outer conductor layer 3 and the outer sheath layer 5. Optionally, the wrapping layer can be non-woven fabric, mica tape, fiberglass tape, etc.

[0051] The flame-retardant outer sheath 5 is uniformly extruded over the wrapping layer 4. The flame-retardant rating of the outer sheath can be adjusted according to user requirements, achieving ordinary single-strand flame retardancy, Class B flame retardancy, or B1 flame retardancy. The flame-retardant outer sheath 5 is provided with slot markings 6 to facilitate the installation and laying of the leaky cable. Optionally, the slot markings 6 can be located at a 180° angle to the slots 30 on the outer surface of the outer sheath 5, using raised sheath ribs as marking lines. There can be one or two marking lines 6. Alternatively, the slot markings can be located at the slots 30 on the outer sheath surface, with marking strips of a different color than the sheath.

[0052] The length of the long / short rectangular slots can be gradually varied along the length of the leaky coaxial cable as needed. The number of variations and the amplitude of these variations are set according to the laying length of the leaky coaxial cable and the signal coverage strength. This significantly reduces high-frequency signal attenuation in the high-order mode transmission frequency band, increases communication distance, and results in small fluctuations in the radiated electromagnetic field strength and a uniform and stable signal.

[0053] Example 2:

[0054] This embodiment differs from Embodiment 1 in that the lengths of all long / short rectangular slots in the slot group 31 are gradually varied along the length of the leaky coaxial cable. Specifically, the lengths of all long rectangular slots gradually increase along the length of the leaky coaxial cable, while the lengths of all short rectangular slots gradually decrease. The combined length of the long and short rectangular slots gradually increases along the length of the leaky coaxial cable. The length variation range of all long rectangular slots is 9–13 mm, with a variation increment of 1 mm, and the length variation range of all short rectangular slots is 7.5–5.5 mm, with a variation increment of 0.5 mm. In this embodiment, the number of gradual changes is 5. Compared to Embodiment 1, as... Figure 5 The graph shows the system loss curve of a 300-meter leaky coaxial cable in Example 1 at 4.9 GHz, for comparison. Figure 6 The system loss curve of the 300-meter leaky coaxial cable in Example 2 at 4.9GHz is shown in the comparison. It can be seen that the signal strength along the leaky coaxial cable provided in Example 2 is more uniform and stable. Especially in the high-order mode transmission frequency band, the overall loss of high-frequency signals is greatly reduced, the communication distance is increased, and the radiated electromagnetic field strength fluctuates less and the signal is more stable.

[0055] In the description of this invention, it should be noted that directional terms such as "center", "lateral", "longitudinal", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", and "counterclockwise" indicate the orientation and 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 device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. They should not be construed as limiting the specific protection scope of this invention.

[0056] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0057] Note that the above description is merely a preferred embodiment and application of the technical principles of the present invention. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the specific embodiments described herein, and may include many other effective embodiments without departing from the concept of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. A broadband, low-loss, leaky coaxial cable, characterized in that: It includes a spiral corrugated copper tube inner conductor layer, a high physical foam insulation layer, a slotted outer conductor layer, a wrapping layer, and a flame-retardant outer sheath layer arranged coaxially from the inside to the outside; The inner conductor layer of the spiral corrugated copper tube is made of high-purity copper strip longitudinally wrapped and welded into a smooth copper tube, and then rolled into a spiral corrugated copper tube by a corrugating machine. The high physical foam insulation layer is coaxially nested on the outside of the inner conductor layer of the spiral corrugated copper tube. The high physical foam insulation layer uses azodicarbonamide as a nucleating agent and injects a mixture of carbon dioxide and octafluorocyclobutane into the molten polyethylene insulation material to form an insulation layer with high strength, high foaming degree, and uniform fine cell structure, with a foaming degree of over 83%.

2. The broadband low-loss leaky coaxial cable according to claim 1, characterized in that: The ratio of the azodicarbonamide nucleating agent to the foamed polyethylene insulation material is 1-2:

100. The foamed polyethylene insulation material is composed of high-density foamed polyethylene and low-density foamed polyethylene, and the ratio of high-density foamed polyethylene to low-density foamed polyethylene is 55-75:25-45.

3. The broadband low-loss leaky coaxial cable according to claim 1, characterized in that: The ratio of carbon dioxide to octafluorocyclobutane gas is 50-70:30-50.

4. The broadband low-loss leaky coaxial cable according to claim 1, characterized in that: The slotted outer conductor layer is longitudinally wrapped around the outer surface of the insulation layer, specifically comprising a high-purity copper strip. The copper strip has slots formed on it, and these slots are composed of several groups of slots arranged in a period P along the cable length and perpendicular to the cable axis. The range of the slot group array period P is: ； in, denoted as the equivalent relative permittivity of the insulating layer, p is the period of the slot array, n is a non-zero positive integer, and c is the speed of light in a vacuum. The minimum operating frequency for a leaky coaxial cable.

5. The broadband low-loss leaky coaxial cable according to claim 4, characterized in that: The slot group consists of multiple rectangular slot groups of unequal lengths arranged along the cable axis and perpendicular to the cable length direction. The unequal length rectangular slot groups include a first unequal length rectangular slot group and a second unequal length rectangular slot group that is symmetrically transformed from the center of the first unequal length rectangular slot group. The center interval between the first unequal length rectangular slot group and the second unequal length rectangular slot group is 2P / 3. The first unequal length rectangular slot group consists of a long rectangular slot group and a short rectangular slot group, and the long rectangular slot group and the short rectangular slot group are arranged vertically and intersecting each other. The vertical interval between the center of the long rectangular slot group and the center of the short rectangular slot group is P / 10.

6. The broadband low-loss leaky coaxial cable according to claim 5, characterized in that: The center-to-center distance between the first and second slots in the long rectangular slot group is P / 12, the center-to-center distance between the second and third slots is P / 24, and the center-to-center distance between the third and fourth slots is P / 8; the center-to-center distance between the first and second slots in the short rectangular slot group is P / 12, the center-to-center distance between the second and third slots is P / 24, and the center-to-center distance between the third and fourth slots is P / 8.

7. The broadband low-loss leaky coaxial cable according to claim 6, characterized in that: The long rectangular slots are 9-15mm long and 2-4mm wide, the short rectangular slots are 5-8mm long and 2-4mm wide, and the gap between all groups of long rectangular slots and groups of short rectangular slots is 2-4mm.

8. The broadband low-loss leaky coaxial cable according to claim 6, characterized in that: The four corners of the long rectangular slot and the short rectangular slot are rounded, and the radius of the rounded corner can be 0.5-1.5mm.

9. The broadband low-loss leaky coaxial cable according to claim 1, characterized in that: Electromagnetic wave signals are transmitted in the broadband low-loss leaky coaxial cable in conventional TEM mode and high-order TE mode, at frequencies lower than [missing information]. At that time, it transmits in TEM mode at a frequency higher than [previous frequency]. At that time, transmission is performed in TE mode. The time can be obtained from the following formula: ; Where D is the equivalent diameter of the outer conductor layer, and d is the equivalent diameter of the inner conductor layer. is the equivalent relative permittivity of the insulating layer.

10. The broadband low-loss leaky coaxial cable according to claim 1, characterized in that: The flame-retardant outer sheath is provided with slot markings to facilitate the installation and laying of the leaky cable. The slot markings are located at a position 180° relative to the slots on the outer surface of the outer sheath, with the raised sheath ribs serving as marking lines. There may be one or two marking lines.

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