DIELECTRIC WAVEGUIDE

Abstract

Disclosed is a dielectric waveguide. A fibre core of the dielectric waveguide is formed by a first fibre core and a second fibre core. The first fibre core and the second fibre core have an intersection in the cross-section of the dielectric waveguide.

Claims

1. Dielectric waveguide, in which the fibre core is formed by a first fibre core and a second fibre core, the first fibre core and the second fibre core having an intersection in the cross-section of the dielectric waveguide.

2. Dielectric waveguide according to claim 1, the first fibre core and the second fibre core running substantially parallel along the dielectric waveguide.

3. Dielectric waveguide according to claim 1, the first fibre core and the second fibre core each being substantially circular and having substantially identical diameters.

4. Dielectric waveguide according to claim 1, centre points of the respective cross-sections of the first fibre core and the second fibre core having a spacing that is greater than half a diameter of one of the first fibre core and the second fibre core and smaller than the diameter of one of the first fibre core and the second fibre core.

5. Dielectric waveguide according to claim 1, further having a sheath around the fibre core along the dielectric waveguide, the sheath having a permittivity that is smaller than the permittivity of the fibre core, and the sheath having a diameter that is at least twice as great compared with one of the diameters of the first fibre core and the second fibre core.

6. Dielectric waveguide according to claim 5, further having a foil screen around the sheath along the dielectric waveguide.

7. Dielectric waveguide according to claim 6, further having an outer sleeve around the foil screen or the sheath along the dielectric waveguide.

8. Dielectric waveguide according to claim 1, permittivities of sheath to fibre core having a ratio of 1:2.

9. Dielectric waveguide according to claim 1, further having a first tensile thread for the first fibre core and a second tensile thread for the second fibre core, the first fibre core taking up a space around the first tensile thread along the dielectric waveguide and the second fibre core taking up a space around the second tensile thread along the dielectric waveguide.

10. Dielectric waveguide according to claim 1, the first fibre core and the second fibre core having a diameter of approximately 0.5 mm to 1.6 mm.

Description

[0043] Further objectives, features, advantages and application possibilities result from the following description of exemplary embodiments, which are not to be understood as restrictive, with reference to the associated drawings. The same or identical components or elements are always provided with the same or similar reference characters. In the description of the present disclosure, detailed explanations of known connected functions or constructions are dispensed with if these deviate unnecessarily from the sense of the present disclosure. Here all features described and/or depicted show by themselves or in any combination the subject matter disclosed here, even independently of their grouping in the claims or their references. The dimensions and proportions of the components shown in the figures are not necessarily to scale in this case; they may diverge from what is shown here in embodiments to be implemented. In particular, the thickness of the lines, layers and/or regions may be exaggerated or understated in the figures for the sake of clarity.

[0044] FIG. 1 shows a schematic depiction of a dielectric waveguide with fibre core and tensile threads;

[0045] FIG. 2 shows a schematic depiction of a dielectric waveguide with further layers around the fibre core;

[0046] FIG. 3 shows a schematic depiction of attenuation of a dielectric waveguide without sheath;

[0047] FIG. 4 shows a schematic depiction of an attenuation increase of a dielectric waveguide without sheath depending on a distance from an absorber; and

[0048] FIG. 5 shows a schematic depiction of attenuation of a dielectric waveguide with sheath depending on a distance from an absorber.

[0049] The dielectric waveguide is now described on the basis of exemplary embodiments.

[0050] FIG. 1 shows a schematic depiction of a dielectric waveguide 100 with fibre core 105 and tensile threads 115 and 125. The fibre core 105 comprises two fibre cores 110 and 120. The fibre cores 110 and 120 form the common fibre core 105 of the dielectric waveguide 100. By way of example, a tensile thread 115 or 125, which are required in production, is shown per fibre core 110 and 120 in FIG. 1. In the case of FIG. 1, air can be located in the environment of the fibre core 105. Likewise, the fibre core 105 in FIG. 2 can be used. The tensile threads 115 and 125 are spaced apart from one another (see spacing d.sub.3). Here d.sub.3 describes the spacing between the centre points of both fibre cores 110 and 120. The tensile threads 115 and 125 are each located centrally in the two fibre cores 110 and 120.

[0051] The two fibre cores 110 and 120 are melted here (seen in cross-section) along their longitudinal direction such that the distance d.sub.3 corresponds maximally to a sum of the radii of the fibre cores 110 and 120 (d.sub.1/2+d.sub.2/2).

[0052] It is clear that the fibre cores 110 and 120 form the fibre core 105 such that due to the melting, the two fibre cores 110 and 120 do not assume an exactly circular shape, but transition into one another in an overlap area, see here the transition area A in FIG. 1. The transition area A can be formed by a smooth transition (in the form of a curve similar to splines) from a surface of the fibre core 110 to a surface of the fibre core 120. Thus a smooth hollow or trough can be formed between the two fibre cores 110 and 120 in transition area A. The fibre core 105 can thus have a concave structure in cross-section. The structure of the fibre core 105 can have two lateral areas and a central area. The lateral areas can each be circular in this case (see the two fibre cores 110 and 120 for this). The central area can be concave here (see transition area A for this) or have concave sections.

[0053] In particular, the spacing d.sub.3 can be smaller than d.sub.1/2+d.sub.2/2. The spacing d.sub.3, shown schematically in FIG. 1, of the tensile threads 115 and 125 thus represents the maximum. Due to the fact that the two fibre cores 110 and 120 are melted into one fibre core 105, the cross-sections of the fibre cores 110 and 120 can overlap. It is thus possible for spacing d.sub.3=d.sub.1/4+d.sub.2/4, for example. In particular, it can be provided that d.sub.1/4+d.sub.2/4<d.sub.3<d.sub.1/2+d.sub.2/2. Also, as shown in FIG. 1, the diameters of both fibre cores 110 and 120 can be identical (d.sub.1=d.sub.2). This yields the following result for the spacing of the centre points of the fibre cores 110 and 120: d.sub.1/2<d.sub.3<d.sub.1. For example, the spacing d.sub.3 of the centre points of the fibre cores 110 and 120 can lie in a range between 6*d.sub.1/10<d.sub.3<9*d.sub.1/10. In particular, the spacing d.sub.3 of the centre points of both fibre cores 110 and 120 can be greater than 6*d.sub.1/10 (or 7*d.sub.1/10 or 8*d.sub.1/10 or 9*d.sub.1/10). The spacing d.sub.3 of the centre points of both fibre cores 110 and 120 can also be smaller than 9*d.sub.1/10 (or 8*d.sub.1/10 or 7*d.sub.1/10 or 6*d.sub.1/10).

[0054] For example, the diameters d.sub.1 and d.sub.2 lie in a range between 1 mm and 1.6 mm. In particular, the diameters d.sub.1 and d.sub.2 can each be greater than 1.1 mm (or 1.2 mm or 1.3 mm). In particular, the diameters d.sub.1 and d.sub.2 can each be smaller than 1.7 mm (or 1.6 mm or 1.5 mm or 1.4 mm). The tensile threads 115 and 125 can likewise have the same or similar dimensions. The diameter d.sub.4 of the tensile threads 115 and 125 can lie in a range from 0.05 mm to 0.4 mm, in particular 0.1 mm (or 0.2 mm, or 0.3 mm).

[0055] The double-circumference geometry shown in FIG. 1 of the fibre core 105 of the dielectric waveguide 100 can have a better insertion loss than a dielectric waveguide with a rectangular cross-section. This is due to the fact that in the area of maximal active-power density, less dielectric material and accordingly fewer dielectric losses act on the field.

[0056] For example, the material used for the fibre core 105 can be a weakly branched polymer chain, for example high-density polyethylene (HDPE). HDPE has a permittivity ε.sub.r=2.25 and a loss factor of tan δ=5*10.sup.−4. This material cannot comply with various requirements in the automotive sector, however. For this reason, basic polypropylene (PP) with a permittivity of ε.sub.r=2.26 and a loss factor of tan δ=7*10.sup.−4 can also be used for the fibre core 105. This material very closely resembles the dielectric properties of HDPE. The transmission characteristic of the dielectric waveguide 100 made of basic PP is poorer in contrast to HDPE, however.

[0057] To ensure long line lengths, the manufacture of the dielectric line 100 can be based on the extrusion of a dielectric material (of the fibre cores 110 and 120) around a carrier or tensile thread 115 and 125. The respective tensile thread 115 and 125 can be made of polyethylene terephthalate (PET) (ε.sub.r=2.91 and tan δ=1*10.sup.−2 at f=77 GHz) in this case.

[0058] Further details and aspects are mentioned in connection with the exemplary embodiments described above or below. The exemplary embodiment shown in FIG. 1 can have one or more optional additional features, which correspond to one or more aspects mentioned in connection with the proposed concept or exemplary embodiment and variants described below with reference to FIG. 2.

[0059] FIG. 2 shows a schematic depiction of a dielectric waveguide 200 with further layers 230, 240 and 250 around the fibre core 105. The dielectric waveguide 200 represents an expansion of the concept from FIG. 1 and can be supplemented by the features described in FIG. 1. Relative to the dielectric waveguide 100 presented from FIG. 1, a dielectric waveguide 200 is shown in FIG. 2 that has further elements to the fibre core 105, namely sheath 230, foil screen 240 and outer sleeve 250. In FIG. 2, the sheath 230 encloses the fibre core 105, which is formed jointly by the two fibre cores 110 and 120 by melting. It is to be seen in FIG. 2 that the two fibre cores 110 and 120 can overlap. The degree of overlapping can correspond to FIG. 1. The sheath 230 can be described or used here as spacer 230.

[0060] The material of the spacer can be a material with low dielectric losses, for example. Furthermore, the material can have a low dielectric constant. The diameter of this spacer 230 (b.sub.1*2) can also be dimensioned such that the field intensity outside of the spacer 230 has decayed to the extent that it cannot be influenced from outside. In particular, the diameter b.sub.1*2 can depend in this case on the permittivity of the fibre core 105 and of the spacer 230 as well as of the frequency range used. For example, the spacer 230 can have a radius b.sub.1 in the range of 1 mm to 5 mm. In particular, b.sub.1 can be greater than 2 mm (or 3 mm or 4 mm or 4.5 mm or 4.75 mm or 4.8 mm). The spacer 230 can thus enclose the fibre core 105 of the dielectric waveguide 200 to protect it from environmental influences. In particular, care can be taken to ensure that the spacer 230 creates a space as large as possible around the fibre core 105. For example, such a distance (shortest distance between outer boundary of the spacer 230 and fibre core 105) b can be greater than 2 mm (or 3 mm or 4 mm or 5 mm or 6 mm). The amount of spacer material can represent a trade-off between environmental influences and material.

[0061] One option for realising the spacer 230 is a foam extrusion. The cross-section in this case is circular (see also FIG. 2). The degree of foaming can be selected in the extrusion process such that the ratio of dielectric constants (fibre core 105 to spacer 230) substantially corresponds to the target ratio 1/2. For most materials, this means selecting a degree of foaming that is as high as possible. To prevent melting between fibre core 105 and spacer 230, a separating foil 260 can optionally be located between these two elements. Possible materials for the foam material are polyethylene (PE) and polypropylene (PP). Foamed PP has a permittivity of ε.sub.r=1.5 and a loss factor of tan δ=5.5*10.sup.−4.

[0062] Another possibility for realising the spacer 230 is strapping with expanded polytetrafluorethylene (ePTFE).

[0063] For EMC reasons, it can be sensible depending on the application to enclose the spacer 230 with a conductive foil screen 240. The line is thus shielded electrically from the environment. A thickness b.sub.2 of the foil screen 240 can be less than 0.2 mm (or 0.15 mm or 0.1 mm or 0.05 mm).

[0064] To protect the dielectric waveguide from environmental influences (UV radiation or chemical processes), an outer sleeve 250 in the form of a jacket, for example made of PVC, can be provided depending on the application. A thickness b.sub.3 of the outer sleeve can be less than 0.5 mm (or 0.45 mm or 0.4 mm or 0.35 mm) here. A thickness b.sub.3 of the outer sleeve 250 can be greater than 0.2 mm (or 0.25 mm or 0.3 mm or 0.35 mm) here. Furthermore, the outer sleeve 250 can be a dissipative layer. An adequate shielding effect can thus be achieved by losses in this layer. The outer sleeve 250 can consist of a slightly conductive PVC material or have a slightly conductive PVC material.

[0065] Further details and aspects are mentioned in connection with the exemplary embodiment described above and its variants. The exemplary embodiment shown in FIG. 2 can have one or more optional additional features, which correspond to one or more aspects mentioned in connection with the proposed concept or the exemplary embodiment described above (e.g. FIG. 1) and its variants.

[0066] FIG. 3 shows a schematic depiction of attenuation of a dielectric waveguide without sheath. FIG. 4 shows a schematic depiction of a dielectric waveguide without sheath depending on a distance from an absorber. The absorber can be provided in the form of the outer sleeve, as described in FIG. 2. FIG. 5 shows a schematic depiction of a dielectric waveguide with sheath depending on a distance from the absorber.

[0067] The aspects described here can be provided for broadband and robust signal guidance, in particular in cars in the course of automation.

[0068] The aspects and features that were mentioned and described together with one or more of the examples and figures described in detail above can also be combined as with one or more of the other examples to replace a similar feature of the other example or to introduce the feature additionally into the other example.

[0069] Furthermore, the following claims are incorporated hereby into the detailed description, where each claim can stand as a separate example on its own. If each claim can stand as a separate example on its own, it should be noted that, although a dependent claim in the claims can refer to a particular combination with one or more other claims, other exemplary embodiments can also include a combination of the dependent claim with the subject matter of any other dependent or independent claim. These combinations are proposed here unless it is indicated that a certain combination is not intended. Furthermore, features of a claim are also to be included for any other independent claim, even if this claim is not made directly dependent on the independent claim.