Radiation coaxial cable

Abstract

The present disclosure relates to a radiating coaxial cable. A radiating coaxial cable is disclosed, which includes an inner conductor, an insulating layer surrounding the inner conductor, a conductive shielding layer surrounding the insulating layer, and an outer jacket surrounding the shielding layer. The conductive shielding layer includes a radiating longitudinal shielding portion having radiating holes and a non-radiating longitudinal shielding portion without radiating holes. The outer jacket includes a first outer jacket portion facing the radiating shielding portion and a second outer jacket portion facing the non-radiating shielding portion. The first outer jacket portion is thicker than the second outer jacket portion. In this way, the cable can be more protected from the harmful effects of metal objects close to the radiating side of the cable or in contact with the radiating side of the cable.

Description

Technical Field

[0001] The present disclosure relates to the field of coaxial cables. Specifically, the present disclosure relates to radiating coaxial cables and processes for manufacturing radiating coaxial cables. Background Art

[0002] As is known, a radiating coaxial cable (also known as a "leaky coaxial cable") is a coaxial cable configured to transmit and receive radio waves at a specific radio frequency or within a specific radio frequency range so as to be used as an extended antenna. Radiating coaxial cables are typically used to provide uniform radio frequency coverage (e.g., mobile coverage) for extended and confined indoor environments such as tunnels (subway, railway, and road tunnels), buildings (e.g., office corridors, shopping malls, or parking lots), mines, or vessels.

[0003] Known coaxial cables include an inner conductor surrounded by an insulating layer, a tubular conductive shielding layer (also known as the "outer conductor"), and an outer jacket which is typically the outermost cable layer. In a radiating coaxial cable, a plurality of holes (such as slots or holes) are made in the shielding layer to allow radio waves to leak in and out of the cable along the length of the cable. The holes can be longitudinally aligned along the cable shielding layer. A single straight line of radiation holes can be provided in the cable shielding layer such that the coaxial cable has a single radiation side. Alternatively, two or more diametrically opposed straight lines of radiation holes can be provided in the cable shielding layer such that the coaxial cable has two opposed radiation sides.

[0004] The performance of a radiating coaxial cable is measured in terms of several parameters including return loss, attenuation, and coupling loss. Specifically, return loss is the power loss of a signal that is returned / reflected due to discontinuities in the cable. Most applications of radiating coaxial cables require that the return loss (measured on a 100 m straight cable) not exceed a maximum threshold of -18 dB. Higher return loss may interfere with the normal operation of a transmitter or may even damage the transmitter.

[0005] Metal objects placed close to a radiating coaxial cable on the radiation side of the radiating coaxial cable may affect the performance of the radiating coaxial cable in terms of return loss and attenuation. A metal object close to the cable on the radiation side of the cable effectively acts as a resonant element which reflects radio frequency signals and ultimately increases its return loss and attenuation.

[0006] The installation of a radiating coaxial cable in a tunnel or a building typically utilizes a suitable fixture configured to fix the cable to a support surface such as a wall or a ceiling. Such a fixture is typically made of plastic so as not to affect the cable performance as discussed above. The fixture includes an annular portion whose diameter substantially matches the outer diameter of the radiating coaxial cable so as to accommodate the cable and hold the cable firmly. The coaxial cable is typically accommodated in the annular portion of the fixture where the radiation side of the coaxial cable points away from the support surface.

[0007] In order to securely fix a length of radiating coaxial cable to a supporting surface, multiple plastic clamps should be used evenly distributed along the length of the cable. Typically, a clamp installation spacing of 1-3 meters is used to obtain a secure fix.

[0008] However, in some cases, the plastic clamp alone cannot ensure a secure installation of the radiating coaxial cable.

[0009] "Installation Guidelines" retrieved from http: / / products.rfsworld.com / / userfiles / instruction_sheets / radiaflex_installation_guideline_edition_j_2.pdf Cables, Edition J" (2012) discloses the use of fire-resistant clamps, which were developed for situations where the cables are required to remain functional for as long as possible in the event of a fire. In fact, in such situations, the cables should not become detached from the wall or ceiling and, in doing so, could also block escape routes. Such fire-resistant clamps are made of stainless steel and should be used in addition to plastic clamps. The recommended installation spacing for these fire-resistant clamps is about 8-10 meters. Similar to the plastic clamps, the fire-resistant clamps also include an annular portion, the diameter of which substantially matches the outer diameter of the radiating coaxial cable in order to accommodate the cable and securely fix it. Summary of the invention

[0010] Applicants have noted that refractory clamps are metal objects that surround and contact the outer jacket of a radiating coaxial cable during installation. As such, they may act as resonant elements, thereby increasing the return loss or attenuation of the cable, as discussed above.

[0011] The Applicant has thus faced the problem of providing a radiating coaxial cable that overcomes the above-mentioned disadvantages.

[0012] Generally speaking, applicants have addressed the problem of providing a radiating coaxial cable that is less susceptible to adverse effects caused by metal objects (such as, refractory clamps) in contact with or near the radiating side(s) of the radiating coaxial cable.

[0013] According to an embodiment of the present disclosure, the above problems are solved by a radiating coaxial cable, the conductive shielding layer of which includes at least one radiating longitudinal portion in which a plurality of radiating holes are present and at least one non-radiating longitudinal portion without holes. An outer jacket surrounds the conductive shielding layer. The outer jacket has a varying thickness. Specifically, the portion of the outer jacket facing the radiating portion of the conductive shielding layer is thicker than the portion of the outer jacket facing the non-radiating portion of the conductive shielding layer.

[0014] The greater thickness of the portion of the outer jacket facing the radiating shielding portion advantageously increases the distance between the radiating shielding portion and any object (e.g., a metallic object such as a metallic clamp) on the radiating side of the cable that is close to or in contact with the outer surface of the radiating coaxial cable.

[0015] The applicant has actually conducted some tests and found that when a metallic object is in contact with the coaxial cable on the radiating side of the coaxial cable, its return loss peaks at several resonant frequencies, and at these peaks, the return loss value (measured on a straight cable with a length of 100 m) is higher than the maximum threshold of -18 dB. However, if the metallic object is placed at a certain distance from the coaxial cable, then the return loss decreases. The applicant has observed that within the entire operating frequency range of the coaxial cable, a distance of 2 - 12 mm is sufficient to keep the return loss below the maximum threshold of -18 dB.

[0016] By performing these tests, the applicant has realized that since the thickness of the outermost jacket of the radiating coaxial cable is generally in the range of 1 mm to 6 mm, it is possible to achieve the above-mentioned reduction of the return loss (below -18 dB) by increasing the thickness of the portion of the jacket on the radiating side of the cable (i.e., the portion of the jacket facing the holes in the cable shielding layer).

[0017] Therefore, when the cable is installed by (also) using a metallic clamp (which is shaped to surround and contact the outer jacket of the radiating coaxial cable in order to firmly hold the cable), since the metallic clamp is held at an increased distance from the radiating portion of the shielding layer, the interference effect of the metallic clamp is advantageously reduced in terms of return loss and / or attenuation.

[0018] Then the installation spacing of the fire-resistant metallic clamp can be reduced from 8 - 10 meters to 2 - 3 meters, thereby allowing the avoidance of using plastic clamps. Using a single type of clamp (metallic clamp) advantageously makes the cable easier to install, reduces the installation cost, and improves safety in the event of a fire.

[0019] Therefore, according to a first aspect, the present disclosure provides a radiating coaxial cable, which includes:

[0020] - an inner conductor;

[0021] - An insulating layer that surrounds the inner conductor and is in direct contact with the inner conductor;

[0022] - A conductive shielding layer that surrounds the insulating layer and includes at least one radiating longitudinal shielding portion in which a plurality of radiation holes are present and at least one non - radiating longitudinal shielding portion in which there are no radiation holes; and

[0023] - A jacket that surrounds the conductive shielding layer and includes at least one first jacket portion facing the radiating shielding portion and at least one second jacket portion facing the non - radiating shielding portion,

[0024] wherein the first jacket portion is thicker than the second jacket portion.

[0025] The radiating coaxial cable according to the present disclosure has a jacket, and the cross - section of the jacket has a substantially circular inner profile and a substantially elliptical outer profile.

[0026] In an embodiment, the cross - section of the jacket may have an outer profile concentric with the conductive shielding layer. In an alternative embodiment, the cross - section of the jacket may have an outer profile eccentric with respect to the conductive shielding layer.

[0027] In an embodiment of the present disclosure, the first jacket portion includes a cavity extending longitudinally along at least one length of the radiating coaxial cable. Such a cavity may be empty or at least partially filled with a filling material. The filling material may be a solid or a foamed material, such as a foamed polymer that may be the same as or different from the jacket.

[0028] In an embodiment, when the cavity is empty, it can accommodate an optical fiber. The optical fiber may be provided during the manufacturing process of the cable or inserted into the cable cavity after deploying the cable, for example, by blowing.

[0029] In an embodiment, the thickness of the first jacket portion is in the range of 2 mm to 20 mm. In an embodiment, the thickness of the second jacket portion is in the range of 1 mm to 6 mm.

[0030] In an embodiment, a mica tape may be interposed between the conductive shielding layer and the insulating layer that would otherwise be in direct contact with each other.

[0031] In an embodiment, a mica tape or other fire - resistant barrier, fiber tape, PET (polyethylene terephthalate) tape, or paper tape or foil may be interposed between the jacket and the conductive shielding layer that would otherwise be in direct contact with each other.

[0032] According to a second aspect, the present disclosure relates to a process for manufacturing a radiating coaxial cable, the process comprising:

[0033] - Providing an inner conductor;

[0034] - Provide an insulating layer that surrounds the inner conductor and is in direct contact with the inner conductor;

[0035] - Provide a conductive shielding layer that surrounds the insulating layer and includes at least one radiating longitudinal shielding portion in which there are a plurality of radiation holes and at least one non-radiating longitudinal shielding portion without radiation holes; and

[0036] - Provide a jacket that surrounds the conductive shielding layer and includes at least one first jacket portion facing the radiating shielding portion and at least one second jacket portion facing the non-radiating shielding portion,

[0037] wherein the first jacket portion is thicker than the second jacket portion.

[0038] In this specification and the claims, the "thickness" of the cable jacket means the distance between two points generated by the intersection of a ray originating from the center of the conductive shielding layer and the inner and outer surfaces of the cable jacket in the transverse plane of the cable.

[0039] For the purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing quantities, amounts, percentages, etc. should be understood to be modified in all instances by the term "about". Moreover, all ranges include any combination of the disclosed maximum and minimum points, and include any intermediate ranges that may or may not be specifically enumerated herein.

[0040] In at least one of the foregoing aspects, the present disclosure may be implemented according to one or more of the following embodiments, optionally in combination.

[0041] For the purposes of this specification and the appended claims, the word "a" or "an" shall be construed to include one or at least one, and the singular also includes the plural, unless clearly indicated otherwise. This is done merely for convenience and to give a general sense of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] With reference to the accompanying drawings, the present disclosure will become fully apparent after reading the following detailed description given by way of example and not by way of limitation, wherein:

[0043] - Figure 1 A side view of a radiating coaxial cable according to a first embodiment of the present disclosure is schematically shown;

[0044] - Figure 2a and Figure 2b A radiating coaxial cable according to a first embodiment of the present disclosure and its variations are schematically shown;

[0045] - Figure 3a and Figure 3bSchematically shows a radiating coaxial cable according to a second embodiment of the present disclosure and its variants;

[0046] - Figure 4a and Figure 4b Schematically shows a radiating coaxial cable according to a third embodiment of the present disclosure and its variants.

[0047] - Figure 5a and Figure 5b Are respectively the return loss versus frequency curve and the attenuation versus frequency curve showing the test results made by the applicant. Detailed Description

[0048] The reference numerals used in all the figures shall be the same for equivalent cables and cable parts.

[0049] Figure 1 Shows a side view of a radiating coaxial cable 10 according to a first embodiment of the present disclosure.

[0050] The cable 10 includes an inner conductor 2 surrounded by an insulating layer 3, a tubular conductive shielding layer 4, and an outer jacket 5. The outer jacket 5 can be the outermost layer of the cable 10. The cable 10 may also include other layers (e.g., a fire barrier or a wrapping tape between the shielding layer 4 and the outer jacket 5 and / or between the insulating layer 3 and the shielding layer 4), which are not shown in the figures and will not be described hereinafter.

[0051] The inner conductor 2 can be hollow or solid. In the case of a hollow conductor, it can be in the form of a corrugated welded tube. The inner conductor 2 is made of a conductive metal such as copper, aluminum, or a composite material thereof. The inner conductor 2 may have an outer diameter ranging between 1 mm and 25 mm.

[0052] The insulating layer 3 can be made of polyethylene (optionally foamed polyethylene) or other suitable electrical insulating materials. The insulating layer 3 may have an outer diameter ranging between 5 mm and 55 mm and a thickness ranging between 1 mm and 20 mm.

[0053] The conductive shielding layer 4 is made of a conductive metal such as copper, aluminum, or a composite material thereof. The shielding layer 4 can be either smooth or corrugated. The shielding layer 4 can be either welded or folded. The shielding layer 4 may have an outer diameter ranging between 5 mm and 60 mm and a thickness ranging between 0.03 mm and 4 mm (including the corrugations, if any).

[0054] According to the first embodiment, the shielding layer 4 includes a radiating portion 40 that extends longitudinally along the length of the cable. The radiating portion 40 of the shielding layer 4 has a plurality of radiating holes 42 that penetrate through the thickness of the shielding layer to allow radio waves to leak in and out of the cable 10, which accordingly acts as an antenna. The remaining portion of the shielding layer 4 without radiating holes will hereinafter be referred to as the "non-radiating portion" of the shielding layer 4 and is denoted by the reference numeral 41.

[0055] The jacket 5 is made of a polymeric material such as polyethylene. Optionally, the jacket 5 may have flame retardant properties. For example, the jacket 5 may be made of a halogen-free flame retardant thermoplastic material.

[0056] The jacket 5 has an uneven thickness. Specifically, a first jacket portion 50 facing the radiating portion 40 of the shielding layer 4 is thicker than the remaining portion of the jacket 5 (i.e., a second jacket portion 51 facing the non-radiating shielding portion 41).

[0057] Figure 2a A cross-sectional view of Figure 1 the radiating coaxial cable 10 is shown.

[0058] As Figure 2a shown, the first jacket portion 50 facing the radiating portion 40 of the shielding layer 4 is the jacket portion enclosed between two rays R and R' that originate from the center of the shielding layer 4 and intersect the opposite edges of the holes 42 in the radiating portion 40 of the shielding layer 4. "Thicker" means that at least one thickness of the first jacket portion 50 is greater than all thicknesses of the second jacket portion 51.

[0059] As Figure 2a shown, a first ray R1 originating from the center of the shielding layer 4 passes through the first jacket portion 50 and defines two points P11 and P12 at the intersections with the inner and outer surfaces of the jacket 5 respectively. While a second ray R2 originating from the center of the shielding layer 4 passes through the second jacket portion 51 at an angular position, thus defining two points P21 and P22 at the intersections with the inner and outer surfaces of the jacket 5 respectively. According to the present invention, for at least one ray R1 passing through the first jacket portion 50 and for each ray R2 passing through the second jacket portion 51 at any angular position, the distance P11 - P12 is greater than the distance P21 - P22.

[0060] Although the thickness of the second jacket portion 51 may be in the range of 1 mm to 6 mm, the thickness of the first jacket portion 50 may alternatively be in the range of 2 mm to 20 mm, such as 5 mm to 15 mm.

[0061] For example, the cross-section of the jacket 5 may have a substantially circular inner profile and an oval or substantially elliptical outer profile, as Figure 2aAs shown. According to the first embodiment, the outer jacket 5 is shaped such that the center of the outer contour of its cross-section is located at an intermediate position (eccentric arrangement) between the center of the shielding layer 4 and the radiating portion 40 of the shielding layer 4. This eccentric arrangement results in the first outer jacket portion 50 being thicker than the second outer jacket portion 51.

[0062] Other shapes of the outer jacket cross-section can be envisioned as long as the first outer jacket portion 50 facing the radiating portion 40 of the shielding layer 4 is thicker than the second outer jacket portion 51 facing the non-radiating portion 41 of the shielding layer 4.

[0063] Figure 2b A cross-sectional view of a radiating coaxial cable 11 according to a variant of the first embodiment is shown. The radiating coaxial cable 11 is the same as the cable 10, except that the first outer jacket portion 50 facing the radiating portion 40 of the shielding layer 4 includes a cavity 52 extending at least longitudinally along the length of the cable 11.

[0064] On the one hand, the shape and size of the cross-section of the cavity 52 can be selected so as to maximize the protection of the radiating portion 40 from interference by metal objects placed close to or in contact with the radiating coaxial cable 11, and, on the other hand, to maintain the mechanical robustness of the cable 11 by preventing the first outer jacket portion 50 from collapsing when the cable 11 is bent or subjected to mechanical stress. As Figure 2b The shape and size of the cavity 52 shown are merely exemplary.

[0065] The cavity 52 can either be empty (i.e., filled with air) or at least partially filled with an optionally foamed material, thereby improving the mechanical strength of the cable 11 and enhancing the protection of the radiating portion 40 from interference by metal objects placed close to or in contact with the radiating side of the coaxial cable 11. For example, foam can be used to fill the cavity 52.

[0066] The material for at least partially filling the cavity 52 can be, for example, polyethylene or a low-smoke zero-halogen (LS0H) compound, such as including ethylene vinyl acetate (EVA). The material can be foamed by techniques familiar to those skilled in the art (such as by adding a foaming agent to the polymer) and then extruded. Alternatively, a gas such as nitrogen or carbon dioxide or other gases is mixed with the particles of the filling material to release pressure out of the crosshead of the extruder, which causes the filling material to foam.

[0067] If the cavity 52 is empty, then it can accommodate one or more optical fibers (not shown in Figure 2b )

[0068] As described above, according to the first embodiment, the shielding layer 4 is bent at its radiating portion 40, and the jacket 5 is shaped to be eccentric with respect to the shielding layer 4. According to the second embodiment, the holes 42 impart a substantially flat shape to the radiating portion 40 of the shielding layer 4, such that a thicker first jacket portion 50 can be obtained by either a concentric or an eccentric arrangement of the jacket 5.

[0069] Figure 3a Fig. shows a cross-sectional view of a radiating coaxial cable 12 according to a second embodiment of the present invention. According to the second embodiment, the presence of the radiating holes 42 gives the radiating portion 40 of the shielding layer 4 a flat cross-sectional appearance.

[0070] For example, the cross-section of the jacket 5 can have a substantially circular inner profile (except for one or more flat portions in contact with one or more of the holes 42 of the radiating portion 40 of the shielding layer 4) and an oval or substantially elliptical outer profile, as Figure 3a depicted in.

[0071] As Figure 3a shown in, the jacket 5 can be shaped such that the center of its cross-sectional outer profile is at an intermediate position between the center of the shielding layer 4 and the radiating portion 40 of the shielding layer 4 (eccentric arrangement). Thus, due to the flat shape of the radiating portion 40, the outer dimensions of the jacket 5 (and thus the outer dimensions of the entire cable 12) that are substantially equal to the outer dimensions of the cable 10 according to the first embodiment result in a thicker first jacket portion 50 facing the radiating portion 40 of the shielding layer 4. Accordingly, according to the second embodiment, the radiating portion 40 of the shielding layer 4 is even more protected from interference by metal objects placed near or in contact with the radiating side of the coaxial cable 12.

[0072] Alternatively, the jacket 5 can be shaped such that the center of its cross-sectional outer profile substantially coincides with the center of the shielding layer 4 (concentric arrangement, not shown in the figures). Even if the arrangement is concentric, at least due to the flat shape of the radiating portion 40 of the shielding layer 4, the result is that the first jacket portion 50 is still thicker than the second jacket portion 51.

[0073] Other shapes of the jacket cross-section can be envisaged, as long as the first jacket portion 50 facing the radiating portion 40 of the shielding layer 4 is thicker than the second jacket portion 51 facing the non-radiating portion 41 of the shielding layer 4.

[0074] To further increase the protection of the radiating portion 40, according to a variant of the second embodiment, the first jacket portion 50 facing the radiating portion 40 of the shielding layer 4 includes a cavity 52 extending longitudinally along at least one length of the cable, as in the cable 13 Figure 3b depicted in. This applies to both the case of an eccentric jacket arrangement and the case of a concentric jacket arrangement.

[0075] As described above in connection with the first embodiment, also in the radiating coaxial cable 13 of this variant according to the second embodiment, on the one hand, the shape and dimensions of the cross-section of the cavity 52 can be selected so as to maximize the protection of the radiating part 40 from interference by metal objects placed close to or in contact with the radiating coaxial cable 13, and, on the other hand, to maintain the mechanical robustness of the cable 13 by preventing the first jacket part 50 from folding up when the cable 13 is bent or subjected to mechanical stress. As Figure 3b The shape and dimensions of the cavity 52 shown are merely exemplary.

[0076] Moreover, according to the second embodiment, the cavity 52 can either be empty (i.e., filled with air) or at least partially filled with a suitable material, as discussed above.

[0077] According to the above first and second embodiments, the shielding layer 4 of the coaxial cable includes a single radiating part 40, i.e., the cable has only one radiating side. However, the present invention can also be applied to coaxial cables having two or more radiating sides.

[0078] Figure 4a A cross-sectional view of a coaxial cable 14 according to a third embodiment of the present invention is shown, the shielding layer 4 of which includes two radially opposite radiating parts 40a, 40b extending longitudinally along the length of the cable. As described above, each radiating part 40a, 40b has a corresponding plurality of radiating holes. Optionally, the presence of the radiating holes can give the radiating parts 40a, 40b of the shielding layer 4 a partially flat cross-sectional appearance, as Figure 4a and Figure 4b depicted. Thus, according to the third embodiment, the shielding layer 4 includes two radially opposite non-radiating parts 41a, 41b, which are complementary to the radiating parts 40a, 40b and have no radiating holes. The radiating parts 40a, 40b can have different dimensions relative to each other.

[0079] Moreover, according to the third embodiment, the jacket 5 has an uneven thickness. Specifically, the first jacket parts 50a, 50b facing the radiating parts 40a, 40b of the shielding layer 4 are thicker than the rest of the jacket 5 (i.e., the second jacket parts 51a, 51b that are complementary to the jacket parts 50a, 50b and face the non-radiating parts 41a, 41b of the shielding layer 4).

[0080] As Figure 4aAs shown in [reference], the first jacket portion 50a (50b) facing the radiating portion 40a (40b) of the shielding layer 4 is the jacket portion enclosed between two rays Ra (Rb) and Ra' (Rb') that originate from the center of the shielding layer 4 and intersect the opposite edges of the radiation holes of the radiating portion 40a (40b) of the shielding layer 4. The above definitions of "thicker" and "thickness" still apply.

[0081] Moreover, according to the third embodiment, the cross-section of the jacket 5 may have an oval or elliptical outer contour and a substantially circular inner contour (except for one or more flat portions in contact with one or more holes 42 of the radiating portions 40a, 40b of the shielding layer 4), as Figure 4a shown in [reference]. According to the third embodiment, the jacket 5 is shaped such that the center of the outer contour of its cross-section is substantially coincident with the center of the shielding layer 4 (concentric arrangement). Other shapes of the cross-section of the jacket can be envisioned as long as the first jacket portions 50a, 50b facing the radiating portions 40a, 40b of the shielding layer 4 are thicker than the second jacket portions 51a, 51b facing the non-radiating portions 41a, 41b of the shielding layer 4.

[0082] To further enhance the protection of the radiating portions 40a, 40b from interference by metal objects placed close to or in contact with the radiating side of the coaxial cable, according to a variant of the third embodiment, at least one of the first jacket portions 50a, 50b facing the radiating portions 40a, 40b of the shielding layer 4 includes cavities 52a, 52b that extend longitudinally along at least one length of the cable, as Figure 4b shown in the cable 15 in [reference].

[0083] As described above in connection with the first and second embodiments, also in the radiating coaxial cable 15 according to this variant of the third embodiment, on the one hand, the shape and size of the cross-section of the cavities 52a, 52b can be selected to maximize the protection of the radiating portions 40a, 40b of the shielding layer 4 from interference by metal objects placed close to or in contact with the radiating coaxial cable 15, and, on the other hand, to maintain the mechanical robustness of the cable 15 by preventing the first jacket portions 50a, 50b from folding when the cable 15 is bent or subjected to mechanical stress. As Figure 4b shown in [reference], the shape and size of the cavities 52a, 52b are merely exemplary.

[0084] Also according to the third embodiment, the cavities 52a, 52b can be either empty (air) or at least partially filled with a suitable material, as discussed above. If the cavities 52a, 52b are empty, then they can accommodate at least one optical fiber.

[0085] In all of the above embodiments, the greater thickness of the (one or more) first jacket portions facing the (one or more) radiation shielding portions advantageously increases the distance between the radiation shielding portions and any object (e.g., a metallic object such as a metal clamp) that contacts the outer surface of the radiating coaxial cable on the radiating side of the cable outside the cable.

[0086] The Applicant has carried out a number of tests, the results of which are shown in Figure 5a and Figure 5b wherein the return loss and attenuation values are shown on the ordinate and the frequency is shown on the abscissa.

[0087] These values have been measured on a 100 m long straight radiating coaxial cable before and after positioning metallic elements at different distances from the cable.

[0088] Figure 5a Illustrates the return loss in a cable according to the prior art (i.e., without a thicker jacket corresponding to the radiating portion). The return loss is expressed in -dB on the ordinate and the frequency is in the range from 50 to 4000 MHz on the abscissa. The grey peaks represent cables without metallic objects at distances shorter than 15 mm and the peak height thereof remains below the maximum threshold of -18 dB over the entire operating frequency range. The black peaks represent cables having a metallic object (50 cm long) at a distance of about 5 mm from the cable jacket. The increase in return loss is clear and, in particular, the presence of the metallic object renders the cable unusable in the frequency band from about 2200 - 4000 MHz. In the case where a 50 cm long metallic object is in direct contact with the cable jacket (not shown), it has been found that the cable is unusable in the frequency band from about 1000 - 4000 MHz.

[0089] Figure 5b Illustrates the attenuation in a cable according to the prior art (i.e., without a thicker jacket corresponding to the radiating portion). On the ordinate, this graph shows the percentage increase in attenuation in a cable having a metallic object (915 mm long) in the vicinity (4 mm) relative to a cable without metallic objects at distances closer than 15 mm. On the abscissa, the frequency ranges from 50 to 4000 MHz. Over most of the frequency band (from about 800 to about 2600 MHz), the percentage increase in attenuation exceeds 30%. The return loss has also been measured on this cable (not shown) and it has been found that this cable (with a 915 mm long metallic object at 4 mm from the cable jacket) is unusable in the frequency band from about 1200 - 3000 MHz.

[0090] According to the above embodiments of the present disclosure, the reduction in the above-mentioned return loss and attenuation is achieved by increasing the thickness of the jacket portion (i.e., the jacket portion facing the holes in the cable shielding layer) on the (one or more) radiating sides of the cable.

[0091] Thus, when installing a cable according to any one of the above embodiments of the present disclosure by also using a metal clamp (which is shaped to surround and contact the outer jacket of the radiating coaxial cable in order to firmly hold the cable), since the metal clamp is held at an increased distance from the radiating portion of the shielding layer, the interference effect of the metal clamp is advantageously reduced in terms of return loss.

[0092] Then the installation spacing of the fire-resistant metal clamp can be reduced from 8 - 10 meters to 2 - 3 meters, thus allowing the avoidance of using plastic clamps. Using a single type of clamp (metal clamp) advantageously makes the cable easier to install and reduces the installation cost.

Claims

1. A radiating coaxial cable (10, 11, 12, 13, 14, 15), comprising: - an inner conductor (2); - an insulating layer (3) surrounding the inner conductor (2) and in direct contact with the inner conductor (2); - a conductive shielding layer (4) surrounding the insulating layer (3) and including at least one radiating longitudinal shielding portion (40; 40a, 40b) in which a plurality of radiating holes (42) are present and at least one non-radiating longitudinal shielding portion (41; 41a, 41b) without radiating holes; and - a jacket (5) surrounding the conductive shielding layer (4) and including at least one first jacket portion (50; 50a, 50b) facing the radiating longitudinal shielding portion (40; 40a, 40b) and at least one second jacket portion (51; 51a, 51b) facing the non-radiating longitudinal shielding portion (41; 41, 41b), wherein the first jacket portion (50; 50a, 50b) is thicker than the second jacket portion (51; 51a, 51b), and wherein the cross-section of the jacket (5) has a substantially circular inner profile and a substantially elliptical outer profile. The cross-section of the jacket (5) has an outer profile concentric with the conductive shielding layer (4). The cross-section of the jacket (5) has an outer profile eccentric with respect to the conductive shielding layer (4). The first jacket portion (50; 50a, 50b) includes a cavity (52; 52a, 52b) extending longitudinally along at least one length of the radiating coaxial cable (11, 13, 15).

2. The radiating coaxial cable (10, 11, 14, 15) according to claim 1, wherein, The cavity (52; 52a, 52b) is empty.

3. The radiating coaxial cable (12, 13) according to claim 1, wherein, The cavity (52; 52a, 52b) is at least partially filled with a filling material.

4. The radiating coaxial cable (11, 13, 15) according to claim 1, wherein, The cavity (52; 52a, 52b) houses at least one optical fiber.

5. The radiating coaxial cable (11, 13, 15) according to claim 4, wherein, The thickness of the first jacket portion (50; 50a, 50b) is in the range of 2 mm to 20 mm.

6. The radiating coaxial cable (11, 13, 15) according to claim 4, wherein, The thickness of the second jacket portion (51; 51a, 51b) is in the range of 1 mm to 6 mm.

7. The coaxial radiation cable (11, 13, 15) according to claim 5, wherein, A mica tape is interposed between the conductive shielding layer (4) and the insulating layer (3).

8. The radiating coaxial cable (10, 11, 12, 13, 14, 15) according to claim 1, wherein, A mica tape or a fiber tape or a PET tape or a paper tape or a foil is interposed between the jacket (5) and the conductive shielding layer (4).

9. The radiating coaxial cable (10, 11, 12, 13, 14, 15) according to claim 1, wherein, 12. A process for manufacturing a radiating coaxial cable (10, 11, 12, 13, 14, 15), the process comprising:

10. The radiating coaxial cable (10, 11, 12, 13, 14, 15) according to claim 1, wherein, - providing an inner conductor (2); 11. The radiating coaxial cable (10, 11, 12, 13, 14, 15) according to claim 1, wherein, - providing an insulating layer (3) surrounding the inner conductor (2) and in direct contact with the inner conductor (2); - providing a conductive shielding layer (4) surrounding the insulating layer (3) and including at least one radiating longitudinal shielding portion (40; 40a, 40b) in which a plurality of radiating holes (42) are present and at least one non-radiating longitudinal shielding portion (41; 41a, 41b); and - providing a jacket (5) surrounding the conductive shielding layer (4) and including a portion facing the radiating longitudinal shielding portion (40; ​ ​ ​ at least one first jacket part (50; 50a, 50b) of (40a, 40b) and at least one second jacket part (51, 51a, 51b) facing the non-radiating longitudinal shielding part (41; 41, 41b), wherein the first jacket part (50; 50a, 50b) is thicker than the second jacket part (51; 51a, 51b), and wherein the cross-section of the jacket (5) has a substantially circular inner contour and a substantially elliptical outer contour.

Images