Positioning of conductors in doublet cables

Abstract

Method for the determination of a spacing (S) between at least a first and a second conductor at least partially, preferably fully, embedded in an embedding material, the method comprising the steps: a) obtaining at least a first outer dimension (d1), preferably a diameter, of the first conductor and a second outer dimension (d2), preferably a diameter, of the second conductor, in a first direction; b) measuring a width (W) of the embedding material in the first direction; c) measuring a first distance (D1) and a second distance (D2) between the closest point of an outer perimeter of the embedding material and the first and second conductors respectively, in the first direction; d) determining the spacing (S) between the first and second conductor in the first direction by subtracting the first distance, the second distance, the first outer dimension and the second outer dimension from the width according to the formula S=W-(D1+D2+d1+d2) and / or determining the pitch (P) between the first and second conductor in the first direction, according to the formula P=W - D1 -D2 -d1 / 2- d2 / 2.

Description

[0001] Positioning of Conductors in Doublet Cables

[0002] Description

[0003] Twin conductor insulated wires, also known as "Doublet cables", are increasingly used as a cost-efficient solution for high-performance communication over shorter distances. Doublet cables are cables in which two conductors run parallel to each other along the length of the cable and are placed within a insulation material. Typically, the insulation material into which the conductors are embedded can have an elliptic shape, a dumbbell-type, a dog-bone, or a figure-8 shape.

[0004] Among the numerous applications for the employment of doublet cables are for example high performance computing and 5G data transmission, in which highspeed communication must be guaranteed over distances of less than a couple of meters.

[0005] In order to achieve the necessary performance in transmission speed and quality, the production process must reliably produce cables within very tight specifications with respect to the material, the geometry, insulation properties, and the shape stability. Such specifications should preferably be continuously checked during the production process (in-line), which allows a timely correction of deviation from the expected results, thus reducing waste and cost.

[0006] In particular, the specifications relating to the geometry are critical for the quality of the product, as these relate to numerous electrical properties, such as the capacitance between the conductors, which in turn affect cross-talk and signal transmission speed and quality. The relevant quantities are the spacing between the conductors, the distance of the two conductors from the insulation at the two extremities or the distance of the conductors from the upper and lower parts of the embedding material.

[0007] The spacing between the two conductors is understood as the distance between the two conductors, i.e. the shortest distance between the two conductor surfaces. An alternative but equivalent metric is the pitch, , i.e. the distance between the axes of the two conductors. In all embodiments, the pitch may therefore be used as an alternative to the spacing.

[0008] The measurement of these quantities presents several difficulties. The embedding material may be foam-like, containing numerous small gas-filled chambers, which presents serious difficulties for measurements using ultrasound, as the ultrasound is absorbed and scattered too rapidly to reach the necessary penetration. Furthermore, embedding material can be non-transparent, making the measurement with optical means (i.e. measurement with visible or infrared light) impossible. Also, the shape may be different for each production run. In general it is preferable to use a measurement technique which is adapted to the materials used, i.e. to use optical measurements for transparent materials and for example ultrasound for opaque or non-transparent materials.

[0009] Typically, measurements to obtain the position of conductors in the doublet cables use ultrasound. As stated, this method is unsatisfactory e.g. in foam-like materials, where ultrasound signals are absorbed, so that other principles are necessary, like X-rays. X-Rays provide the necessary penetration, however, the use of X-rays comes at a certain health risk, thus requiring adequate protection measures, and increasing costs substantially. Alternatively, it is known to use Tera-Hertz signals, which can also penetrate foam materials.

[0010] Preferably, the measurement of distances may also be performed by interferometric means, sometimes also referred to as optical interference measurement. Optical interference measurement is a technique for obtaining subsurface images of translucent or transparent materials. Like in ultrasound methods signal reflected from within the material are processed to provide cross- sectional images.

[0011] In any case, a direct measurement of the spacing between the two conductors is not straightforward. Optical interference, ultrasound and Tera-Hertz technologies have a limited lateral resolution, which does not allow a precise measurement of the spacing between two wires, which are in close proximity. Also, the shape of the cable affects the path the optical interference, ultrasound or Tera-Hertz signals travel in the cable insulator. X-Ray systems can potentially measure directly the distance between the conductors, but are not well-accepted in industry because of safety concerns as well as cost. There is therefore a need to provide a way by which the spacing between the conductors (wires) in a doublet cable may be measured, which is both sufficiently accurate and does not involve unnecessary health risks and / or costs.

[0012] This problem is solved by the method according to claim 1. Further, this problem is solved by the system according to claim 11.

[0013] In particular, the problem is solved by a method for the determination of a spacing (S) between at least a first and a second conductor at least partially, preferably fully, embedded in an embedding material, the method comprising the steps: a) obtaining at least a first outer dimension (dl), preferably a diameter, of the first conductor and a second outer dimension (d2), preferably a diameter, of the second conductor, in a first direction; b) measuring a width (W) of the embedding material in the first direction; c) measuring a first distance (Dl) and a second distance (D2) between the closest point of an outer perimeter of the embedding material and the first and second conductors respectively, in the first direction; d) determining the spacing (S) between the first and second conductor in the first direction by subtracting the first distance, the second distance, the first outer dimension and the second outer dimension from the width according to the formula S=W-(Dl + D2+dl+d2) and / or determining the pitch (P) between the first and second conductor in the first direction, according to the formula P=W - Dl -D2 -d 1 / 2- d2 / 2.

[0014] It is a key idea of the present invention that the measurement of the spacing or pitch between the conductors relies on an indirect measurement. It is further preferred to use substantially reflection measurements. Reflection measurements refer to such measurements where a signal is reflected along the direction of transmission, after being transmitted, at least at the surface to be measured, and the reflected signal is then detected.

[0015] Reflection measurements in this sense can be understood as measurements, which measure, particular distances, predominantly along a predefined direction. In particular, reflection measurements only provide very limited lateral resolution. The advantage of relying on reflection measurements lies in the fact that optical interference, ultrasound and Tera-Hertz measurements provide only a very limited lateral resolution, but are highly accurate for distance measurements along a predefined axis. By using only such reflection measurements, the overall accuracy of the determination of a spacing between the conductors can therefore be improved, without the need for more complicated or costly imaging techniques. Specifically, known geometric features of the cable construction can be utilized in order to determine the spacing between the conductors more accurately.

[0016] According to the invention, only distances between the outer perimeter of the embedding material and the closest point on the outer circumference of one of the conductors is measured at a time, obviating the need for high lateral resolution in favor of point like, preferably reflection measurements.

[0017] These are performed in a first direction, wherein the first direction is substantially parallel to the spacing between the conductors. Preferably, the first direction may be a horizontal direction.

[0018] In this way a known relationship between the overall width (outer diameter) of the embedding material, the width (diameter) of the conductors in said first direction and the spacing can be used to measure said spacing in directly.

[0019] Obviously, a direct measurement of the spacing between the conductors is not possible (substantially) using reflection measurements, as the conductors themselves get in the way of a "down the line" measurement. Tera-Herz measurements are masked by the conductive materials of the conductor. The difference in the sound speed propagation properties of the insulator and of the conductor materials make it difficult to obtain direct measurements of the spacing using ultrasound signals. Alternatively, a direct measurement could be accomplished from a "bird's eye perspective", however this would necessitate a measurement method with high lateral resolution, which bears the aforementioned disadvantages.

[0020] By measuring the spacing and / or pitch between the conductors indirectly, a high degree of accuracy can be obtained, using only measurements along the first direction (i.e. reflection measurements). Furthermore, by only measuring from the outer perimeter of the embedding material to the closest point on the closest conductor, the overall distances across which measurements are performed are reduced, which further increases accuracy, as the amount of absorption and / or scattering is lower the shorter the distances measured. In particular, first and second distances respectively correspond to the depth of the conductors from the cable surfaces on the two respective sides.

[0021] Then, the Spacing S between the two conductors can be computed as

[0022] S =IV - Di -D2- dt - d2

[0023] Alternatively, the so-called pitch, i.e. the distance between the axes of the two conductors can be determined, which can be computed for symmetrical conductors to be

[0024] P= S + d, / 2 + d2 / 2 = W- Di -02-di / 2- d2 / 2.

[0025] The distance of the conductors from the upper and lower surfaces can be assessed with a reflection measurement by using Optical interference, Tera-Hertz or Ultrasound signals, which delivers a sufficiently precise estimate for the production process.

[0026] In preferred embodiments, the spacing and / or pitch between the conductors will lie between 0.010 and 2.000mm, further preferred between 0.500 and 1.500mm. A preferred accuracy for the determination of the spacing is between plus / minus 0.005mm and plus / minus 0.010mm

[0027] In a preferred embodiment, the first outer dimension and the second outer dimension are obtained by optical measurement and / or by specification, preferably before the embedding of the conductors into the embedding material.

[0028] In determining the outer dimensions of the first and second conductors optically or by specification, the determination of the spacing can be performed faster and more accurately.

[0029] Specifically, if the measurement is performed before the embedding of the conductors into the embedding material, the optical measurement of the conductor outer dimension (diameter) is very efficient.

[0030] In particular, as the conductors themselves may change only very little in diameter across the length of the wire, it can be assumed that the conductor outer dimensions (which can be thought of as their diameter, at least in the first direction) are known. This can either be a priori, by obtaining specifications from the manufacturer of the conductors, or by an additional measurement, in particular optical measurement, of the two conductor diameters preferably before the extrusion of the (insulation) embedding material (embedding into the embedding material).

[0031] In preferred embodiments, the conductors are rotationally symmetric about the length direction, making the outer dimension coincide with their diameter. The diameters are preferred to lie between 0.200 and 0.500 mm, or further preferred to lie between 0.250 and 0.405mm.

[0032] In a further preferred embodiment, the width (W) is measured optically.

[0033] As the embedding material itself is openly accessible, optical determination of the width may be performed very quickly and accurately.

[0034] In preferred embodiments the width will lie between 0.500 and 5.00 mm, further preferred to lie between 1.000mm and 2.000mm, with a preferred accuracy of plus / minus 0.018mm.

[0035] The width in this context refers to the (in particular largest) total diameter from one side of the perimeter of the embedding material to the other side in the first direction.

[0036] According to a preferred embodiment the measurement of the first and / or second distance is performed using a reflection measurement, preferably optical interference measurement, ultrasound measurement, Tera-Hertz measurement.

[0037] Depending on the embedding material, different measurement techniques may be more or less adequate, as the embedding material exhibits different absorption and scattering properties at different wavelengths and / or with respect to different waveforms (acoustic / electromagnetic). It is further preferred to utilize Tera-Hertz measurements for foam-like embedding materials and optical interference or ultrasound otherwise. As stated before, this is preferable because Tera-Hertz measurements have a better penetration performance in foam-like materials. According to a further preferred embodiment, the measurement method may therefore be chosen according to the anticipated magnitude of the first and / or second distance, in particular to minimize absorption.

[0038] The method according to one of the preceding claims, wherein all measurements, are reflection measurements.

[0039] The use of reflection measurements is advantageous, in particular if they are performed with optical interference, Tera-Hertz or ultrasound signals, as the requirements for lateral resolution are reduced. It is further preferred to at least rely on reflection measurements for all those distances that can or should not be determined by optical measurement from images or shadows, as such optical measurements provide a better lateral resolution.

[0040] Another aspect of the invention is a method for the production of a doublet cable comprising a first and a second conductor at least partially, preferably fully, embedded in an embedding material, wherein the first and / or second conductors are positioned within the embedding material using the steps: a) controlling a first distance (DI) and a second distance (D2) between the closest point of an outer perimeter of the embedding material and the first and second conductors respectively, in a first direction, b) controlling a third distance (Tl) and / or a fourth (T3) distance between the closest point of a width of the embedding material and the first conductor in a second direction, wherein the third and fourth distances are measured from opposite outer sides of the first conductor; c) controlling a fifth distance (T2) and / or a sixth (T4) distance between the closest point of an outer perimeter of the embedding material and the second conductor in a second direction, wherein the third and fourth distances are measured from opposite outer sides of the second conductor; wherein the first and second direction are orthogonal to each other and mutually orthogonal to a length direction of the doublet cable, the method further comprising the steps: d) determining the spacing (S) and / or pitch between the first and second conductor according to the above method; e) adjusting a setting of one or more of the first, second, third, fourth, fifth and sixth distances, based on the spacing measured in step d), preferably to achieve a spacing and / or pitch closer to a predetermined spacing; wherein the steps a) to e) are repeated iteratively, preferably in real-time.

[0041] In such a way, the indirect measurement of the spacing can be used to create a feedback loop, in order to help to achieve that quality standards are met throughout the manufacturing process.

[0042] In particular, an ideal spacing between the two conductors may be predetermined ahead of time, and the measurement of the actual spacing measured between the conductors can be used to achieve said predetermined spacing in-line during production.

[0043] Generally, the spacing and / or pitch of the conductors will depend on the first and second distances most directly. While the third to sixth distances also influence the spacing to some degree, this may often be neglected, such that a controlfeedback loop between the measured spacing of the conductors and the controlling of the first and / or second distances can be sufficient to achieve the necessary quality control.

[0044] Once it is determined that the spacing deviates from a predetermined value by more than a given amount, the first and / or second distances may be varied appropriately, in order to correct the spacing and / or pitch, preferably continuously during production.

[0045] The second direction is defined as the perpendicular direction to the first direction, in a plane, which is normal to the length direction of the wire. Preferably, the second direction is a vertical direction. In other words, the first and second direction span the plane, to which the length direction of the wire is normal. According to yet another preferred embodiment, the spacing (S) and / or pitch is adjusted in order to achieve a predetermined capacitance between the conductors.

[0046] As the distance between the conductors will have a major impact on the capacitance of the cable, it is an easy and straightforward way to manipulate the spacing to achieve a desired capacitance.

[0047] In a further preferred embodiment, the embedding material is an insulating and / or a foam-like material.

[0048] Such materials provide the necessary flexibility and insulation properties, in order to withstand deformations, while keeping the wires insulated.

[0049] In a further preferred embodiment, the method comprises a step of measuring at least one of the third, fourth, fifth or sixth distances, preferably by optical interference and / or Tera-Hertz and / or ultrasound signals, and controlling them to lie closer to a predetermined value.

[0050] By controlling the third, fourth, fifth or sixth distances the conductors can be centered more accurately in the embedding material, which increases the overall precision of the spacing between the two conductors.

[0051] In a further preferred embodiment measurement result of at least one of the third, fourth, fifth or sixth distances is used in the determination of the spacing (S) and / or pitch.

[0052] While generally the first and second distances have the greatest impact on the spacing and / or pitch between the conductors, further accuracy improvements can be made by incorporating the third, fourth, fifth or sixth distances into the determination of the spacing. In general, this will result in incorporating a deviation in the second direction from the horizontal between the two conductors in the first direction. This can be achieved straightforwardly through the employment of the Pythagorean theorem. In these cases, it may be assumed that the first and second conductors are rotationally symmetric around the length axis, such that an width in the second direction is equal to that in the first direction, to find the closest distance between two points on the first and second conductors.

[0053] The problem is further solved by a system comprising an extruder, a measurement unit, and a control unit, wherein the control unit is configured to control the extruder based on a measurement signal from the measurement unit, to perform the method described above.

[0054] In most applications, the doublet cables are manufactured through extrusion techniques. In these cases the inventive idea of an indirect measurement of the spacing and / or the creation of a feedback loop can be employed by controlling the extrusion process. In particular the extruder may be configured to control the first to sixth distances, in order to place the conductors within the embedding material.

[0055] The measurement unit may then measure the appropriate distances, in order to indirectly infer the spacing between the conductors. In addition thereto, the measurement unit may transmit the measurements to a control unit, which then determines the spacing. To this end, the control unit may comprise at least one processor. If the measured spacing deviates from the desired spacing, the control unit can adjust the extruder settings, in order to move the spacing closer to the desired value.

[0056] According to a further preferred embodiment the measurement unit comprises one or more of the following: optical measurement device, preferably a camera or a laser scanner, optical interference measuring device, ultrasound measuring device, Tera-Hertz measuring device, X-ray imaging device.

[0057] Optical measurement device may be used to acquire the width of the embedding material and / or the outer dimensions of the conductors, while the remaining imaging techniques may be employed to measure the first to sixth distances using a reflected signal.

[0058] The problem is also solved by a computer readable medium, configured to cause a processor of a control unit to control a system according to the above to perform a method as described above. In the following the invention is described further with respect to the figures.

[0059] Figure 1 shows a cross-section of an approximately elliptical doublet cable.

[0060] Figure 2 shows a cross-section of a dumbbell-shaped or figure-8-shaped doublet cable.

[0061] Figure 3 shows a schematic representation of a system comprising an extruder, a measurement unit and a control unit.

[0062] Figure 1 shows a typical doublet cable 1 with an elliptical shape. In the shown orientation, the first direction can be thought of as the direction connecting the two conductors 2 and 3, which is essentially a horizontal direction. In figure 1, the first conductor 2 and second conductor 3 are already embedded within the embedding material 4. As can be seen, the first distance Di corresponds to the depth of the first conductor 2 beneath the surface or outer perimeter of the embedding material 4. More specifically, the first distance Di measures a distance from the surface of the first conductor 2 to the closest point on the outer perimeter of the embedding material 4 in the first direction.

[0063] Similarly, the second distance D2measures the depth of the second conductor 3 beneath the surface or outer perimeter of the embedding material 4. More specifically, the second distance D2measures a distance from the surface of the second conductor 3 to the closest point on the outer perimeter of the embedding material 4 in the first direction. In this case, the closest point is to the right of the second conductor 3.

[0064] According to the invention, the spacing S between the two conductors 2,3 can be measured indirectly as follows. The overall width of the embedding material W (in the first direction) can be measured, preferably optically. Then, the first and second distances DI,D2can be measured, preferably using reflected signals (that is from the left and right respectively, given the orientation shown). The first and second outer dimension (again in the first direction) di,d2of the first and second conductors 2,3 can then either be measured as well, in particular beforehand, or is obtained from the specifications of the manufacturer. As most conductors 2,3 will be rotationally symmetric around their length axis, the first and second outer dimension (in the first direction) di,d2will typically coincide with the diameter of the conductors 2,3.

[0065] As can be seen, the spacing S can then be computed indirectly from the formula S=W-(Di+D2+di+d2). The (vertical) shift in the second direction, which corresponds to the up / down direction in figure 1, may have a small influence on the spacing S, if the first and second conductor 2,3 are not centred and / or positioned within the embedding material in the second direction. For generally symmetrical embedding perimeters, this will result in an inequality of the ratio between the third and fourth distance Ti, T3and the fifth and sixth distance T2, T4. Usually, the control of the third to sixth distances Ti, T3, T2, T4is sufficient to ensure the required accuracy of the spacing S. However, the calculation of the spacing S may be altered in straightforward trigonometric fashion, to include these distances.

[0066] It may be assumed that the extruder 103, which may be used for the production of the doublet cable, is capable of controlling at least some of the first to sixth distances, based on the input of the control unit 101.

[0067] Figure 2 shows essentially the same features as figure 1, albeit with a different perimeter shape of the embedding material 4.

[0068] Figure 3 shows a schematic diagram of a system 100 according to the invention. The control unit 101 controls the extruder 103 to produce a doublet cable with a given setting of the first to sixth distances Di, D2, Ti, T3, T2, T4. The resulting doublet cable is measured by the measurement unit 102 to obtain the necessary distances, which are then fed back to the control unit 101. The control unit 101 then determines the spacing S indirectly according to the method of the invention and (if necessary) adjusts the control settings of the extruder 103, in order to achieve a desired spacing S.

[0069] It is pointed out that the aim of this disclosure is to achieve the broadest possible scope of protection. In this respect, the disclosure contained in the claims can also be specified by features that are described with further features (even without these further features necessarily being included). It is explicitly pointed out that round brackets and the term "in particular" are intended to emphasize the optionality of features in the respective context (which does not mean, conversely, that a feature is to be regarded as mandatory in the corresponding context without such identification). The term "element / element" is preferably intended to characterize a respective coherent structure (or assembly), which in turn can be connected to at least one other structure (to form a possibly one- piece and / or non-movable overall structure) or can be delimited from all other structures.

[0070] List of Reference Signs

[0071] 1 Doublet Cable

[0072] 2 First Conductor

[0073] 3 Second Conductor

[0074] 4 Embedding Material

[0075] W width

[0076] 5 Spacing

[0077] Di First Distance

[0078] D2Second Distance

[0079] Ti Third Distance

[0080] T3Fourth Distance

[0081] T4Fifth Distance

[0082] T2Sixth Distance di First Outer Dimension d2Second Outer Dimension

[0083] 100 System

[0084] 101 Control Unit

[0085] 102 Measurement Unit

[0086] 103 Extruder

Claims

Positioning of Conductors in Doublet CablesClaims1. Method for the determination of a spacing (S) between at least a first and a second conductor at least partially, preferably fully, embedded in an embedding material, the method comprising the steps: a) obtaining at least a first outer dimension (dl), preferably a diameter, of the first conductor and a second outer dimension (d2), preferably a diameter, of the second conductor, in a first direction; b) measuring a width (W) of the embedding material in the first direction; c) measuring a first distance (Dl) and a second distance (D2) between the closest point of an outer perimeter of the embedding material and the first and second conductors respectively, in the first direction; d) determining the spacing (S) between the first and second conductor in the first direction by subtracting the first distance, the second distance, the first outer dimension and the second outer dimension from the width according to the formula S=W-(Dl + D2+dl+d2) and / or determining the pitch (P) between the first and second conductor in the first direction, according to the formulaP=W - Dl -D2 -dl / 2- d2 / 2.

2. The method according to claim 1, wherein the first outer dimension and the second outer dimension are obtained by optical measurement or by specification, preferably before the embedding of the conductors into the embedding material.

3. The method according to claims 1 or 2, wherein the width (W) is measured optically.

4. The method according to one of the preceding claims, wherein the measurement of the first and / or second distance is performed using one of X-ray measurement, optical interference measurement, ultrasound measurement, Tera-Hertz measurement.

5. The method according to one of the preceding claims, wherein all measurements are reflection measurements.

6. Method for the production of a doublet cable comprising a first and a second conductor at least partially, preferably fully, embedded in an embedding material, wherein the first and / or second conductors are positioned within the embedding material using the steps: a) controlling a first distance (DI) and a second distance (D2) between the closest point of an outer perimeter of the embedding material and the first and second conductors respectively, in a first direction, b) controlling a third distance (Tl) and / or a fourth (T3) distance between the closest point of an outer perimeter of the embedding material and the first conductor in a second direction, wherein the third and fourth distances are measured from opposite outer sides of the first conductor; c) controlling a fifth distance (T2) and / or a sixth (T4) distance between the closest point of an outer perimeter of the embedding material and the second conductor in a second direction, wherein the third and fourth distances are measured from opposite outer sides of the second conductor; wherein the first and second direction are orthogonal to each other and mutually orthogonal to a length direction of the doublet cable, the method further comprising the steps: d) determining the spacing (S) and / or pitch (P) between the first and second conductor according to the method of claim 1;e) adjusting a setting of one or more of the first, second, third, fourth, fifth and sixth distances, based on the spacing measured in step d), preferably to achieve a spacing (S) and / or pitch (P) closer to a predetermined spacing (S) and / or pitch (P); wherein the steps a) to e) are repeated iteratively, preferably in real-time.

7. The method according to one of the preceding claims, in particular claim 6, wherein the spacing (S) and / or pitch (P) is adjusted in order to achieve a predetermined capacitance between the conductors.

8. The method according to one of the preceding claims, in particular claim 6 or 7, wherein the embedding material is an insulating and / or a foam-like material.

9. The method according to one of the preceding claims, in particular claims 6 to 8, further comprising a step of measuring at least one of the third, fourth, fifth or sixth distances, preferably by optical interference, TeraHertz and / or Ultrasound signals, and controlling them to lie closer to a predetermined value.

10. The method according to one of the preceding claims, in particular claim 9, wherein a measurement result of at least one of the third, fourth, fifth or sixth distances is used in the determination of the spacing (S) and / or pitch (P).

11. System comprising an extruder, a measurement unit, and a control unit, wherein the control unit is configured to control the extruder based on a measurement signal from the measurement unit, to perform the method of one of the claims 6 to 10.

12. The System according to claim 11, wherein the measurement unit comprises one or more of the following: optical measurement device, preferably a camera or a laser scanner, optical interference measuring device, ultrasound measuring device, Tera-Hertz measuring device, X-ray imaging device.

13. Computer readable medium, configured to cause a processor of a control unit to control a system according to claim 11 to perform the method according to claims 1 to 10.

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