CABLE FOR TRANSMITTING ELECTRICAL SIGNALS

Abstract

The invention relates to a cable for transmitting electrical signals, comprising an outer casing made of an electrically insulating material and at least N lines n with N2 and N|N, which are arranged inside the outer casing, wherein each line m has a total of M wires made of an electrically conductive material with M1 and M|N, wherein the wire m with [1,M], m|N of the line n with n[1,N], n|N is surrounded by a dielectric having a predetermined value for the relative permittivity r(m,n)>1. The following applies for at least two different lines: n=j and n=(j+s) r(m,j)=r(m,j+s)k(s) with m[1,M], m|N, j[1,N1], j|N, s[1, Nj], s|N, wherein k(s) and k(s)[2.0, 0,01] and k(s)[0.01,2.0].

Claims

1. A cable for transmitting electrical signals with an outer casing made of an electrically insulating material and at least N lines n with N2 and N which are arranged within the outer casing, wherein each line n with n[1,N] has a total of M wires made of an electrically conductive material with M1 and M, wherein the wire m with m[1, M], m, of the line n with n[1,N], n is surrounded by a dielectric with a predetermined value for the relative permittivity .sub.r(m,n)>1, wherein for each line n the value for the relative permittivity of the dielectrics of the wires of this line n is identical, except for deviations resulting from the manufacturing process, so that .sub.r(p,n)=.sub.r(p+q,n), where q[1,Mp], q, p[1,M1], p, such that the following applies for at least two different lines n=j and n=(j+s): .sub.r(m,j)=.sub.r(m,j+s)k(s) with m[1,M], m, j[1, N1], j, s[1, Nj], s, where k(s) and k(s)[2.0, 0,01] and k(s)[0.01,2.0], wherein the cable is a star quad cable with M=2 and N=2, in which the four wires of the two lines are twisted with one another in a cruciform manner.

2. (canceled)

3. (canceled)

4. The cable of claim 1, wherein the dielectric of the wires of at least one line is made of the material polypropylene (PP) and the dielectric of the wires of at least one different line is made of the material polyethylene (PE).

5. The cable of claim 1, wherein the dielectric of the wires of at least one line is built up of a concentric layered structure of two or more dielectric materials with different values for the relative permittivity .sub.r.

6. The cable of claim 1, wherein in the case of the wires of at least one line, a space between the wires of this line and the outer casing facing the wires of this line is filled with a dielectric material which has a different value for the relative permittivity .sub.r than that of the dielectric surrounding the wires of this line.

7. The cable of claim 1, wherein a coating with an additional dielectric is provided on an inner side of the outer casing which faces the wires of a line which has a different value for the relative permittivity .sub.r than that of the dielectric surrounding the wires of this line.

8. The cable of claim 7, wherein the additional dielectric is structured as a sequence of layers of dielectric materials, each case having a different value for the relative permittivity .sub.r.

9. The cable of claim 1, wherein the dielectric of at least one wire is arranged in a space between the wire and the outer casing such that, viewed in the cross section of the cable, this space is delimited from the adjacent wires in parabolic form.

10. The cable of claim 1, wherein k[u,w] and k[w,u], are defined where w=0.01, 0.03, 0.1, 0.2, 0.3, 0.5, 0.7, 0.9, 1.0, 1.2, 1.4 or 1.6 and u=0.03, 0.1, 0.2, 0.3, 0.5, 0.7, 0.9, 1.0, 1.2, 1.4, 1.6 or 1.8 and |w|<|u|.

11. The cable of claim 1, wherein in addition, a shielding casing made of an electrically conductive material is provided within which the lines are arranged.

12. The cable of claim 11, wherein the shielding casing is arranged radially outside of or within the outer casing.

13. The cable of claim 11, wherein the shielding casing is integrated in the outer casing.

14. The cable of claim 4, wherein the dielectric of the wires of at least one line is built up of a concentric layered structure of two or more dielectric materials with different values for the relative permittivity .sub.r.

15. The cable of claim 14, wherein k[u,w] and k[w,u], are defined where w=0.01, 0.03, 0.1, 0.2, 0.3, 0.5, 0.7, 0.9, 1.0, 1.2, 1.4 or 1.6 and u=0.03, 0.1, 0.2, 0.3, 0.5, 0.7, 0.9, 1.0, 1.2, 1.4, 1.6 or 1.8 and |w|<|u|.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The features of the invention believed to be novel and the elements characteristic of the invention are set forth with particularity in the appended claims. The figures are for illustration purposes only and are not drawn to scale. The invention itself, however, both as to organization and method of operation, may best be understood by reference to the detailed description which follows taken in conjunction with the accompanying drawings in which:

[0023] FIG. 1 shows a first preferred embodiment of a cable according to the invention in a perspective sectional view;

[0024] FIG. 2 shows a cable according to the invention cable as a four-port;

[0025] FIG. 3 shows a graphic representation of the arithmetical determination of the crosstalk of an electrical signal from one line into another line with different values for k(s) on the basis of a cable model;

[0026] FIG. 4 shows a second preferred embodiment of a cable according to the invention in a sectional view;

[0027] FIG. 5 shows a third preferred embodiment of a cable according to the invention in a sectional view;

[0028] FIG. 6 shows a fourth preferred embodiment of a cable according to the invention in a sectional view;

[0029] FIG. 7 shows a fifth preferred embodiment of a cable according to the invention in a sectional view; and

[0030] FIG. 8 shows a sixth preferred embodiment of a cable according to the invention in a sectional view.

DESCRIPTION OF THE EMBODIMENT(S)

[0031] In describing the embodiment of the present invention, reference will be made herein to FIGS. 1-8 of the drawings in which like numerals refer to like features of the invention.

[0032] In a cable of the aforementioned type, according to the invention the following applies for at least two different lines: .sub.r(m,j)=.sub.r(m,j+s)k(s) with m[1, M], m, j[1, N1], j, s[1, Nj], s, where k(s) and k(s)[2.0, 0,01] and k(s)[0.01,2.0]. In other words, the dielectrics of the wires of one line have a value for the relative permittivity .sub.r of the dielectrics surrounding the respective wires differing by |k(s)| between 0.01 to 2.0 in comparison with the wires of a different line. This results in different propagation speeds for electrical signals on these lines with different dielectrics around the wires. The value for k(s) is for example different for different values for s (k(1)k(2) . . . k(Nj)); however, alternatively the values for k(s) can also be identical for some or all values for s (k(1)=k(2)= . . . =k(Nj)). The values of k(s) can also be identical for several partial quantities of values for s in the range from 1 to (Nj), so that for example three or more identical values for k(s) are present within a cable (if N is greater than or equal to 4), wherein the values for k(s) are different for different partial quantities. In a cable. different lines may have a different number M of wires. In this case the value for M would be a function of n: M(n), wherein the cable (10) is a star quad cable with M=2 and N=2 in which the four wires (16, 18, 20, 22) of the two conductors are twisted with one another in a cruciform manner.

[0033] This has the advantage that, surprisingly, the different propagation speeds of the electrical signals in the two lines with different values for the permittivity of the dielectrics of the respective wires leads to a reduced crosstalk of signals from one line into the other line.

[0034] A different value for the relative permittivity .sub.r(m,n) of the dielectric of the wires of different lines with a value |k| of around 0.3 is achieved in a manner which is particularly simple and economical to manufacture in that the dielectric of the wires of at least one line is made of the material polypropylene (PP; .sub.r2.1) and the dielectric of the wires of at least one different line is made of the material polyethylene (PE, .sub.r2.4).

[0035] A, in total, differing value for the relative permittivity .sub.r of the dielectric of the wires of a line with specific adjustment of a value for k for the deviation of the value for the relative permittivity .sub.r of the dielectric of the wires of a different line is achieved in a simple manner in that the dielectric of the wires of at least one line is built up of a concentric layered structure of two or more dielectric materials with different values for the relative permittivity .sub.r.

[0036] A particularly advantageous adjustment of the value for the relative permittivity .sub.r of the dielectric of the wires of a line with high efficiency is achieved in that, in the case of the wires of at least one line, a space between the wires of this line and the outer casing facing the wires of this line is filled with an additional dielectric material which has a different value for the relative permittivity .sub.r than that of the dielectric surrounding the wires of this line. The dielectric used for filling is thereby located in the region of high field strength densities and is therefore particularly effective.

[0037] An alternative possibility for changing the relative permittivity .sub.r of the wires of individual lines, without needing to change the mechanical structure of the individual wires, is achieved in that a coating with an additional dielectric is provided on an inner side of the outer casing which faces the wires of a line which has a different value for the relative permittivity .sub.r than that of the dielectric surrounding the wires of this line.

[0038] A particularly pronounced influencing of the resulting relative permittivity .sub.r for individual wires is achieved in that the additional dielectric is structured as a sequence of layers of dielectric materials, in each case having a different value for the relative permittivity .sub.r.

[0039] A high efficiency of the dielectric is achieved in that the dielectric of at least one wire is arranged in a space between the wire and the outer casing such that, viewed in the cross section of the cable, this space is delimited from the adjacent wires in parabolic form. As a result, the dielectric fills a space with high field line density.

[0040] The following is preferred for possible value ranges of k(s): k(s)[u, w] and k(s)[w, u], where w=0.01, 0.03, 0.1, 0.2, 0.3, 0.5, 0.7, 0.9, 1.0, 1.2, 1.4 or 1.6 and u=0.1, 0.2, 0.3, 0.5, 0.7, 0.9, 1.0, 1.2, 1.4, 1.6 or 1.8 and |w|<|u|. For example, 0.01<k(s)<1.0; 0.03<k(s)<0.3 or 0.1<k(s)<0.2.

[0041] An additional electromagnetic shielding is achieved in that, in addition, a shielding casing made of an electrically conductive material is provided within which the lines are arranged. This shielding casing is for example arranged radially outside of or within the outer casing or is integrated in the outer casing.

[0042] The invention is explained in more detail in the following with references to the drawings.

[0043] For the purpose of signal transmission in multi-conductor cables or cables with several wires, in order to achieve fast data transmission, signal transmission with differential pairs of lines or differential conductor pairs is preferably used. A typical cable used for such an application is the star quad cable.

[0044] Generally, a cable used for electrical signal transmission has a tubular outer casing made of an electrically insulating material. A shielding casing made of an electrically conductive material is also for example provided, wherein this is surrounded coaxially by the outer casing. Alternatively, the shielding casing is integrated in the outer casing. N lines with N2 and N are arranged radially within the shielding casing, wherein each line n with n[1, N] comprises a total of M wires made of an electrically conductive material with M1 and M. The wire m with m[1, M], m of the line n with n[1, N], n is surrounded by a dielectric with a predetermined value for the relative permittivity .sub.r(m,n)>1. It is hereby preferable if the dielectrics of the different wires are produced in different colours, so that it is possible to clearly identify the wires at each end of the cable. The M wires of a line n are thereby in each case surrounded by a dielectric, wherein all dielectrics of the M wires of a line n should have a substantially identical value for the relative permittivity .sub.r(m,n) with m=1, . . . M. However, as a result of deviations resulting from the manufacturing process and also as a result of the colouring, slightly different values result for the values for the relative permittivity .sub.r(m,n) of the dielectrics of the M wires of a line. These deviations usually lie within the region of 5/1000 and, while actually undesirable, are unavoidable.

[0045] In other words, for each line n the value for the relative permittivity .sub.r of the dielectrics of the M wires of this line n is identical except for deviations resulting from the manufacturing process, so that .sub.r(p,n)=.sub.r(p+q,n), where p[1, M1], p and q[1, Mp], q. In other words, the running index p runs from 1 to (M1) and is a whole number greater than zero and the running index q runs from 1 to (Mp) and is a whole number greater than zero. This means that, in each case, for each line n with n=1 to N:

[00002]$.Math.n=1.Math.\text{:}.Math..Math.{\mathrm{.Math.}}_r\left(1,1\right)={\mathrm{.Math.}}_r\left(2,1\right)=\mathrm{.Math.}={\mathrm{.Math.}}_r\left(M-1,1\right)={\mathrm{.Math.}}_r\left(M,1\right)$$.Math.n=2.Math.\text{:}.Math..Math.{\mathrm{.Math.}}_r\left(1,2\right)={\mathrm{.Math.}}_r\left(2,2\right)=\mathrm{.Math.}={\mathrm{.Math.}}_r\left(M-1,2\right)={\mathrm{.Math.}}_r\left(M,2\right)$$.Math.\mathrm{.Math.}$$n=N-1.Math.\text{:}.Math..Math.{\mathrm{.Math.}}_r\left(1,N-1\right)={\mathrm{.Math.}}_r\left(2,N-1\right)=\mathrm{.Math.}={\mathrm{.Math.}}_r\left(M-1,N-1\right)={\mathrm{.Math.}}_r\left(M,N-1\right)$$.Math.n=N.Math.\text{:}.Math..Math.{\mathrm{.Math.}}_r\left(1,N\right)={\mathrm{.Math.}}_r\left(2,N\right)=\mathrm{.Math.}={\mathrm{.Math.}}_r\left(M-1,N\right)={\mathrm{.Math.}}_r\left(M,N\right)$

[0046] According to the invention, the value for the relative permittivity .sub.r of the dielectrics of the total of M wires of a line j differs by a value k(s) from a value for the relative permittivity .sub.r of the dielectrics of the M wires of at least one different line (j+s), for example the line (j+1). For at least two different lines, the following thereby applies: .sub.r(m,j)=.sub.r(m,j+s)k(s) with m[1, M], m, j[1,N1], j, s[1, Nj], s, where k(s) and k(s)[2.0, 0,01] and k(s)[0.01,2.0], or the index m for the wire runs from 1 to M and is a whole number greater than zero, the index j for the line j runs from 1 to (N1) and is a whole number greater than zero, the index s for the line (j+s) runs from 1 to (Nj) and is a whole number greater than zero. Written out, this means that, for example for the lines 1 and 2 (j=1; s=1) for the M wires with m=1 to M:

[00003]$m=1.Math.\text{:}.Math..Math.{\mathrm{.Math.}}_r\left(1,1\right)={\mathrm{.Math.}}_r\left(1,2\right)-k\left(1\right)$$m=2.Math.\text{:}.Math..Math.{\mathrm{.Math.}}_r\left(2,1\right)={\mathrm{.Math.}}_r\left(2,2\right)-k\left(1\right)$$\mathrm{.Math.}$$m=M-1.Math.\text{:}.Math..Math.{\mathrm{.Math.}}_r\left(M-1,1\right)={\mathrm{.Math.}}_r\left(M-1,2\right)-k\left(1\right)$$m=M.Math.\text{:}.Math..Math.{\mathrm{.Math.}}_r\left(M,1\right)={\mathrm{.Math.}}_r\left(M,2\right)-k\left(1\right)$

[0047] The value k(1) is hereby a number the amount of which |k(1)| is greater than the aforementioned undesired deviation of for example 5/1000 between the values of relative permittivities .sub.r which should be substantially identical. At the same time, the value of k(s) for two different lines (different value for s) can be different or identical. Preferred values for |k(s)| are for example 0.01, 0.03, 0.1, 0.2, 0.3, 0.5, 0.7, 0.9, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0.

[0048] FIG. 1 shows an exemplary embodiment of a cable 10 according to the invention with N=2 and M=2 in the form of a star quad arrangement, wherein the four wires of the two lines are twisted with one another in a cruciform manner. The cable 10 has an outer casing 12 made of an electrically insulating material, a shielding casing 14 made of an electrical conductive material as well as a first wire 16, made of an electrically conductive material, of a first line (m=1, n=1), a second wire 18, made of an electrically conductive material, of the first line (m=2, n=1), a first wire 20, made of an electrically conductive material, of a second line (m=1, n=2) and a second wire 22, made of an electrically conductive material, of the second line (m=2, n=2). The first wire 16 (m=1) of the first line (n=1) is surrounded by a first dielectric 24 with a relative permittivity .sub.r(1,1), wherein here and in the following the numbers in brackets following the term .sub.r represent indices, in this case the indices m and n. The second wire 18 (m=2) of the first line (n=1) is encased by a second dielectric 26 with a relative permittivity .sub.r(2,1). The first wire 20 (m=1) of the second line (n=2) is encased by a third dielectric 28 with a relative permittivity .sub.r(1,2). The second wire 22 (m=2) of the second line (n=2) is encased by a fourth dielectric 30 with a relative permittivity .sub.r(2,2).

[0049] The wires 16, 18 also form a first pair of lines or the first line and the wires 20, 22 form a second pair of lines or the second line.

[0050] Viewed in the cross section of the cable, a first straight line 32 runs through the center point of the wires 16 and 18 of the first line and a second straight line 34 runs through center points of the wires 20, 22 of the second line. The two straight lines 32, 34 run perpendicular to one another at each point in a sectional plane parallel to the representation or the drawing plane in FIG. 1.

[0051] Each wire 16, 18, 20, 22 forms a conductor with the associated dielectric 24, 26, 28, 30. The conductors 16/24, 18/26, 20/28, 22/30 are twisted or stranded with one another in an axial direction in a cruciform manner such that the known star quad arrangement results. The conductors 16/24, 18/26, 20/28, 22/30 are twisted with one another around a central core 36.

[0052] For this example of the star quad cable (M=2, N=2), the above equations for the relative permittivity .sub.r(m,n) of the dielectrics 24, 26, 28, 30 of the wires 16, 18, 20, 22 with m=1, 2 and n=1, 2 and j=1 and s=1 are as follows:

n=1:.sub.r(1,1)=.sub.r(2,1)

n=2:.sub.r(1,2)=.sub.r(2,2)

and

m=1:.sub.r(1,1)=.sub.r(1,2)k(1)

m=2:.sub.r(2,1)=.sub.r(2,2)k(1)

[0053] FIG. 2 shows the star quad cable as a 4-port with a first end 38 and a second end 40. The first line with the wires 16, 18 and the dielectrics 24, 26 (FIG. 1) form a first differential port 42 at the first end 38 and a third differential port 46 at the second end. The second line with the wires 20, 22 and the dielectrics 28, 30 (FIG. 1) forms a second differential port 44 at the first end 38 and a fourth differential port 48 at the second end.

[0054] If a wave is now fed in at the first end 38 at the first port 42 of the first line with the wires 16, 18, then a part of the wave is measurable at the second, third and fourth port 44, 46, 48. The wave component measurable at the third port 46 is a transmission. The wave component measurable at the second port 44 is a so-called crosstalk at the near end 38 NEXT (Near End Crosstalk), i.e. this is a crosstalk from the first line with the wires 16, 18 into the second line with the wires 20, 22 which is reflected back to the first end 38. The wave component measurable at the fourth port is a so-called crosstalk at the far end 40 FEXT (Far End Crosstalk), i.e. this is a crosstalk from the first line with the wires 16, 18 into the second line with the wires 20, 22 which is transmitted to the second end 40. This FEXT is an undesired effect which is to be prevented. Accordingly, a reduction in this wave component FEXT improves the transmission properties of the cable 10 at the second end 40.

[0055] In order to test whether the difference in the relative permittivities .sub.r(m,n) results in an improvement in terms of the FEXT, this FEXT was calculated for a star quad cable designed according to the invention, as described above, using a cable model. The result is shown in FIG. 3. In FIG. 3, 50 identifies a vertical axis on which the FEXT is entered in [dB]. 52 identifies a horizontal axis on which a frequency f of the input signal at the first port 42 (FIG. 2) is entered in [MHz].

[0056] A first graph 54 shows the curve of the FEXT over the frequency in a conventional star quad cable, as actually measured.

[0057] A second graph 56 shows the curve of the FEXT over the frequency in a conventional star quad cable, as calculated from the cable model with k(1)=0. In the calculation by means of the cable model, the following values were assumed for the relative permittivities .sub.r(m,n) of the dielectrics 24, 26, 28, 30:

.sub.r(1,1)=2.235

.sub.r(2,1)=2.240

.sub.r(1,2)=2.235

.sub.r(2,2)=2.240

[0058] For the relative permittivities .sub.r(m,n) of the dielectrics 24, 26, 28, 30, a scattering of the values due to inaccuracies in manufacture and influences resulting from the colouring of the dielectrics with a deviation of 5/1000 is assumed. The curve of the second graph 56 following close to the first graph 54 confirms that that the cable model is serviceable.

[0059] A third graph 58 shows the curve of the FEXT over the frequency in a star quad cable according to the invention, as calculated from the cable model with k(1)=0.1. In the calculation by means of the cable model, the following values were assumed for the relative permittivity .sub.r(m,n) of the dielectrics 24, 26, 28, 30:

.sub.r(1,1)=2.235

.sub.r(2,1)=2.240

.sub.r(1,2)=2.135

.sub.r(2,2)=2.140

[0060] A fourth graph 60 shows the curve of the FEXT over the frequency in a star quad cable according to the invention, as calculated from the cable model with k(1)=0.3. In the calculation by means of the cable model, the following values were assumed for the relative permittivity .sub.r(m,n) of the dielectrics 24, 26, 28, 30:

.sub.r(1,1)=2.235

.sub.r(2,1)=2.240

.sub.r(1,2)=1.935

.sub.r(2,2)=1.940

[0061] A fifth graph 62 shows the curve of the FEXT over the frequency in a star quad cable according to the invention, as calculated from the cable model with k(1)=0.5. In the calculation by means of the cable model, the following values were assumed for the relative permittivity .sub.r(m,n) of the dielectrics 24, 26, 28, 30:

.sub.r(1,1)=2.235

.sub.r(2,1)=2.240

.sub.r(1,2)=1.735

.sub.r(2,2)=1.740

[0062] A sixth graph 64 shows the curve of the FEXT over the frequency in a star quad cable according to the invention, as calculated from the cable model with k(1)=0.7. In the calculation by means of the cable model, the following values were assumed for the relative permittivity .sub.r(m,n) of the dielectrics 24, 26, 28, 30:

.sub.r(1,1)=2.235

.sub.r(2,1)=2.240

.sub.r(1,2)=1.535

.sub.r(2,2)=1.540

[0063] A seventh graph 66 shows the curve of the FEXT over the frequency in a star quad cable according to the invention, as calculated from the cable model with k(1)=0.9. In the calculation by means of the cable model, the following values were assumed for the relative permittivity .sub.r(m,n) of the dielectrics 24, 26, 28, 30:

.sub.r(1,1)=2.235

.sub.r(2,1)=2.240

.sub.r(1,2)=1.335

.sub.r(2,2)=1.340

[0064] The more the nominal value for the relative permittivity .sub.r(m,n) differs between the two lines, the lower the crosstalk (FEXT) in the other line. Thus, the transmission properties of the cable 10 can be improved, in a surprising manner, through a difference k(s) in the relative permittivity .sub.r(m,n) of the dielectrics 24, 26, 28, 30, without this requiring an additional shielding casing for each individual pair of lines 16, 18 and 20, 22.

[0065] FIG. 4 shows a second preferred embodiment of a cable 10 according to the invention, wherein parts with the same function are identified with the same reference symbols as in FIG. 1, so that regarding their explanation reference is made to the above description relating to FIG. 1. In FIG. 4, different hatchings or fillings of the dielectrics 24, 26, 28, 30 show different values for the relative permittivity .sub.r(m,n). An outer casing is not represented in FIG. 4. Thus, it can be seen that the dielectrics 24, 26, 28, 30 are fundamentally produced with the same value for the relative permittivity .sub.r(m,n); however, the dielectrics 24 and 26 are structured in two parts, in each case with two materials with different relative permittivity .sub.r. A first material with the same relative permittivity .sub.r as the dielectrics 28 and 30 encases the wires 16, 18; however, in addition a second material 70 with a different value for the relative permittivity .sub.r is arranged radially between the wires 16, 18 and the first material, so that the dielectrics 24, 26 effectively have a different value for the relative permittivity .sub.r than the dielectrics 28 and 30. The first and second dielectric materials are arranged concentrically to one another and to the respective wires 16, 18.

[0066] FIG. 5 shows a third preferred embodiment of a cable 10 according to the invention, wherein parts with the same function are identified with the same reference symbols as in FIGS. 1 and 4, so that regarding their explanation reference is made to the above description relating to FIGS. 1 and 4. In FIG. 5, different hatchings or fillings show different values for the relative permittivity .sub.r. An outer casing is not represented in FIG. 5. In this embodiment, the wires 16, 18, 20, 22 are surrounded by identical dielectrics, so that their relative permittivity .sub.r is substantially identical. However, in addition, respective spaces between the lines 16/24, 18/26, 20/28 and 22/30 and the shielding casing 14 are filled with a further first dielectric 72 and a further second dielectric 74 which in each case have values for the relative permittivity .sub.r which differ from the dielectrics 24, 26, 28, 30 and also from one another. In this way, the effective values for the relative permittivity .sub.r(m,n) of the line with the wires 16, 18 differ from the value for the relative permittivity .sub.r(m,n) of the line with the wires 20, 22. The filling with the further first and second dielectrics 72 and 74 is such that, viewed in cross section, these fill a region delimited, in parabolic form, by the adjacent lines 16/24, 18/26, 20/28 and 22/30. In this way, the further dielectrics 72 and 74 are located precisely in regions with increased field line density and thus have a great effect.

[0067] FIG. 6 shows a fourth preferred embodiment of a cable 10 according to the invention, wherein parts with the same function are identified with the same reference symbols as in FIGS. 1, 4 and 5, so that regarding their explanation reference is made to the above description relating to FIGS. 1, 4 and 5. In FIG. 6, different hatchings or fillings show different values for the relative permittivity .sub.r. An outer casing is not represented in FIG. 6. In this embodiment, the wires 16, 18, 20, 22 are surrounded by identical dielectrics 24, 26, 28, 30, so that their relative permittivity .sub.r is substantially identical. The additional dielectrics 72 and 74 are arranged on the inner side of the shielding casing 14, in each case such that these are each located between a dielectric 24, 26, 28, 30 of the wires 16, 18, 20, 22 and the shielding casing 14. In this way, the effective values for the relative permittivity .sub.r(m,n) of the line with the wires 16, 18 differ from the value for the relative permittivity .sub.r(m,n) of the line with the wires 20, 22.

[0068] FIG. 7 shows a fifth preferred embodiment of a cable 10 according to the invention, wherein parts with the same function are identified with the same reference symbols as in FIGS. 1, 4, 5 and 6, so that regarding their explanation reference is made to the above description relating to FIGS. 1, 4, 5 and 6. In FIG. 7, different hatchings or fillings show different values for the relative permittivity .sub.r. An outer casing is not represented in FIG. 7. In this embodiment, the wires 16, 18, 20, 22 are surrounded by identical dielectrics 24, 26, 28, 30, so that their relative permittivity .sub.r is substantially identical. The additional dielectrics 72 and 74 are arranged on the inner side of the shielding casing 14, in each case such that these are each located between a dielectric 24, 26, 28, 30 of the wires 16, 18, 20, 22 and the shielding casing 14. In contrast to the fourth embodiment shown in FIG. 6, the additional dielectrics 72 and 74 are built up in layers with the further dielectric 70. In this way, the effective values for the relative permittivity .sub.r(m,n) of the line with the wires 16, 18 differ from the value for the relative permittivity .sub.r(m,n) of the line with the wires 20, 22.

[0069] FIG. 8 shows a sixth preferred embodiment of a cable 10 according to the invention, wherein parts with the same function are identified with the same reference symbols as in FIGS. 1, 4, 5, 6 and 7, so that regarding their explanation reference is made to the above description relating to FIGS. 1, 4, 5, 6 and 7. In FIG. 8, different hatchings or fillings show different values for the relative permittivity .sub.r. An outer casing is not represented in FIG. 8. In this embodiment, the wires 16, 18, 20, 22 are exclusively surrounded by the further dielectric 72 to 74 and the dielectric 72, 74 in each case extends, analogously to the second embodiment according to FIG. 4, from the wires 16, 18, 20, 22 up to the shielding casing 14 and thereby in each case fills a space delimited, in cross section, in parabolic form. In this way, the effective values for the relative permittivity .sub.r(m,n) of the line with the wires 16, 18 differ from the value for the relative permittivity .sub.r(m,n) of the line with the wires 20, 22, and the dielectrics 72, 74 fill precisely that space within the shielding casing 14 in which the highest field line density occurs.

[0070] The invention covers all combinations of the features in each case disclosed in the description, the features in each case claimed in the claims and the features in each case illustrated in the figures of the drawing, insofar as these are technically expedient.

[0071] While the present invention has been particularly described, in conjunction with one or more specific embodiments, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. It is therefore contemplated that the appended claims will embrace any such alternatives, modifications and variations as falling within the true scope and spirit of the present invention.

[0072] Thus, having described the invention, what is claimed is: