EP2912671B1 - Microwave cable and method for producing and using such a microwave cable - Google Patents

Description

TECHNICAL AREA

The present invention relates to the field of microwave technology. It relates to a microwave cable according to the preamble of claim 1. It also relates to a method for manufacturing and the use of such a microwave cable.

STATE OF THE ART

A large number of solutions are known from the technology of cables as to how such a cable, if it comprises an inner conductor and an outer conductor, can be constructed.

In the document U.S. 2,691,698 For example, a telephone cable is described which, in addition to a large number of inner conductors, has two outer conductors that are insulated from one another and constructed as bandings made of a metal foil. The outer conductors are used for separate transmission of signals.

From the pamphlet U.S. 2,447,168 a high-frequency cable is known in which two inner conductors are enclosed by a dielectric and two bands of metallized paper are applied one on top of the other to the dielectric.

From the pamphlet U.S. 5,214,243 a coaxial cable is known with a central inner conductor, a dielectric, a layer of wrapped PTFE tape applied to it, a metal wire braid applied over it, and a layer applied over it Braid made of polyamide fibers, and finally two oppositely overlapping tapes made of PTFE tape.

Finally, the publication shows U.S. 6,201,190 a coaxial cable in which the dielectric surrounding the inner conductor is enclosed by two foil strips lying on top of one another. The foil strips are designed as aluminum-polyester-aluminum laminates.

Out DE 618646 C a telecommunication cable or an antenna feed line with conductors or groups of conductors shielded by metal screens in the form of tape windings is known, the screens consisting of a single or multiple tape winding being designed to be inductance-free or low-inductance. A rubber sleeve is placed between the conductor (s) and the screens. According to one embodiment of the telecommunication cable, the screens consist of two conductive strips which are arranged one above the other and wound in opposite directions.

Especially in the microwave frequency range at frequencies of 40 GHz and more, these solutions have the disadvantage that no prefabricated (coaxial) cables with optimal electrical parameters are feasible.

In the case of a single-wound tape, the insertion loss becomes unstable during bending or twisting, because the windings of the tape shift or loosen. In addition, a (coaxial) plug connector attached to the cable end can only be adapted to such a cable to a limited extent because the tape can loosen after stripping the cable end and therefore no longer fits tightly.

A detachment of the winding (banding) can be largely prevented at one end of the cable if the band is wrapped in an overlapping manner, because at the end of the cable, from which the winding proceeds in the longitudinal direction of the cable, the end of the tape is fixed by the overlap. At the other end of the cable, however, there is no such fixation, so that the banding loosens or even comes off there.

The HF adaptation to the connector is impaired as a result, and the stability of this cable section with a loosened strap is also impaired.

DISCLOSURE OF THE INVENTION

It is therefore an object of the invention to create a microwave cable which avoids the disadvantages of known cables in a simple manner and can in particular be made up without deterioration of the mechanical and electrical properties. It is also an object of the invention to specify a method for producing such a cable and to propose an application.

The aim is to demonstrate an economical solution for making an equipped flexible coaxial cable insensitive to instability of the insertion loss in the event of bending or torsion. In addition to optimal electrical parameters in the microwave range, good mechanical flexibility is a prerequisite.

These and other objects are achieved by the features of claims 1, 11 and 14.

The microwave cable according to the invention is defined in claim 1.

According to one embodiment of the microwave cable according to the invention, the bandings are wound with opposite directions of rotation.

According to another embodiment of the microwave cable according to the invention, a concentric wire mesh is arranged between the outer conductor and the sheathing.

Another embodiment of the invention is characterized in that the bandings are each made up of a metal band.

In particular, the metal strips have the same width and the same thickness.

For applications in which many microwave cables have to be used in a confined space, such as test setups for microprocessors or other highly integrated circuits with high clock frequencies, an embodiment of the invention is advantageous in which the microwave cable has an outer diameter of a few millimeters, in particular about 1, 5 mm, the metal strips each have a width of a few millimeters, in particular about 1.5 mm, and the thickness of the metal strips each a few 1/100 mm, in particular about 0.035 mm.

Another embodiment of the invention is characterized in that the metal strips consist of the same material.

In particular, the metal strips consist of copper and are silver-plated on the surface.

According to another embodiment of the microwave cable according to the invention, the metal strips are each wound with an overlap of about 45% and an offset per revolution of about 0.8 mm.

Yet another embodiment is characterized in that the sheathing consists of FEP.

• Bereitstellen einer Ausgangsanordnung aus dem vom Dielektrikum umgebenen Innenleiter, welche Ausgangsanordnung sich mit einer vorgegebenen Länge zwischen einem ersten Kabelende und einem zweiten Kabelende erstreckt;
• Aufbringen der ersten Bandierung durch überlappendes Umwickeln der Ausgangsanordnung mit einem ersten Metallband, beginnend am ersten Kabelende und fortschreitend zum zweiten Kabelende;
• Aufbringen der zweiten Bandierung durch überlappendes Umwickeln der mit der ersten Bandierung versehenen Ausgangsanordnung mit einem zweiten Metallband, beginnend am zweiten Kabelende und fortschreitend zum ersten Kabelende; und
• Aufbringen der Ummantelung auf die mit den beiden Bandierungen versehene Ausgangsanordnung.

The method according to the invention for producing a microwave cable according to the invention comprises the following steps:

• Providing an output arrangement from the inner conductor surrounded by the dielectric, which output arrangement extends with a predetermined length between a first cable end and a second cable end;
• Applying the first banding by overlapping the output arrangement with a first metal band, starting at the first cable end and progressing to the second cable end;
• Applying the second banding by overlapping wrapping of the output arrangement provided with the first banding with a second metal band, beginning at the second cable end and progressing to the first cable end; and
• Applying the sheathing to the output arrangement provided with the two bandings.

An embodiment of the method according to the invention is characterized in that the first banding is applied with a first direction of rotation, and that the second banding is applied with a second direction of rotation opposite to the first direction of rotation.

Another embodiment is characterized in that before the last step, the output arrangement provided with the two bandings is wrapped with a concentric wire mesh.

According to the invention, the microwave cable is used in a connection cable which has a coaxial connector at each end, the outer conductor of which is connected in an electrically conductive manner to the exposed outer conductor of the microwave cable.

According to one embodiment, the outer conductors of the coaxial connectors are each soldered to the outer conductor of the microwave cable.

In particular, if a concentric wire mesh is arranged between the outer conductor and the sheathing in the microwave cable, the outer conductors of the coaxial connectors are each soldered to the outer conductor of the microwave cable through the wire mesh.

BRIEF EXPLANATION OF THE FIGURES

Fig. 1

den Querschnitt durch ein Mikrowellenkabel gemäss einem Ausführungsbeispiel der Erfindung;

Fig. 2

ein Verbindungskabel mit einem Mikrowellenkabel nach der Erfindung und an den Kabelenden angebrachten koaxialen Verbindern;

Fig. 3A-C

verschiedene Schritte bei der Herstellung eines Mikrowellenkabels gemäss einem Ausführungsbeispiel der Erfindung;

Fig. 4

in einem Ausschnitt die für eine Bandierung beim erfindungsgemässen Mikrowellenkabel massgebenden Parameter; und

Fig. 5

den Stabilisierungseffekt der erfindungsgemässen Bandierungen beim Konfektionieren bzw. Ablängen des Mikrowellenkabels an beiden Enden.

The invention is to be explained in more detail below using exemplary embodiments in connection with the drawing. Show it:

Fig. 1

the cross section through a microwave cable according to an embodiment of the invention;

Fig. 2

a connection cable with a microwave cable according to the invention and attached to the cable ends coaxial connectors;

Figures 3A-C

various steps in the manufacture of a microwave cable according to an embodiment of the invention;

Fig. 4

in a section the parameters which are decisive for banding in the microwave cable according to the invention; and

Fig. 5

the stabilizing effect of the bandings according to the invention when assembling or cutting the microwave cable to length at both ends.

WAYS OF CARRYING OUT THE INVENTION

Fig. 1 shows the cross section through a microwave cable 10 according to an embodiment of the invention. In the center of the microwave cable 10, a central inner conductor 11 is arranged, which can for example consist of a silver-plated Cu wire. The inner conductor 11 is concentrically surrounded by a dielectric 12, for which the materials customary in HF technology, for example PTFE, can be used. The dielectric 12 is concentrically enclosed one after the other in the radial direction by a first banding 13 and a second banding 14, which will be discussed in more detail below. This is followed by a concentric wire mesh 15 that is made up, for example, of silver-plated Cu wire. This concentric layer arrangement is finally enclosed on the outside by a protective casing 16, which preferably consists of an FEP (fluorinated ethylene propylene).

The bandings 13, 14 are each made of a metal band 21, 22 (see Fig. 3 ) built up. The two metal strips 21, 22 can fundamentally be designed differently in terms of material, thickness and width. However, they preferably have the same width B (see Fig. 4 ) and the same thickness. In particular, the metal strips 21, 22 also consist of the same material, preferably copper, which is silver-plated on the surface.

For complex and compact applications in which small dimensions of the cable are particularly important, the microwave cable 10 can have an outside diameter D (see Fig. 2 ) of a few millimeters, in particular about 1.5 mm. The metal bands 21, 22 for the bandings 13 and 14 then preferably each have a width B of a few millimeters, in particular approximately 1.5 mm. The thickness of the metal strips 21, 22 is then in each case a few 1/100 mm, in particular approximately 0.035 mm.

In such a (miniaturized) microwave cable, the metal strips 21, 22 in the bandings 13 and 14 are shown in FIG Fig. 4 each wound with an overlap of about 45% (overlap area 23) and with an offset per revolution (step width w) of about 0.8 mm.

According to the invention, the decisive difference to previous cable forms is that the overlapping wound tapes 13 and 14 are wound progressively in opposite directions with respect to the cable, as shown in FIG Fig. 3 clearly evident.

The in Figures 3A-C The illustrated process steps are first provided an output arrangement from the inner conductor 11 surrounded by the dielectric 12 ( Figure 3A ), which extends with a predetermined length L, which can be several kilometers, for example, between a first cable end 19 and a second cable end 20.

This output arrangement 11, 12 according to Figure 3B the lower, first banding 13 is applied by wrapping the output arrangement 11, 12 with a first metal band 21, starting at the first cable end 19 and progressing (see directional arrow) to the second cable end 20, in an overlapping manner. The sense of rotation when wrapping is counterclockwise in the example shown in the direction of the arrow.

Once the first banding 13 has been completely applied, according to FIG Figure 3C the second banding 14 is applied by overlapping the output arrangement 11, 12 provided with the first banding 13 with a second metal band 21, starting at the second cable end 20 and progressing (see directional arrow) to the first cable end 19. The direction of rotation when wrapping is shown in the illustration Example clockwise seen in the direction of the arrow.

The microwave cable 10 can then be completed by applying further layers (wire mesh 15, sheathing 16).

In principle, it is conceivable to choose the same direction of rotation when applying the two bandings. However, the stability of the cable is even greater if the second banding 14 is applied with a direction of rotation opposite to the direction of rotation of the first banding 13.

The metal strips 21, 22 are preferably made of the same material (silver-plated Cu foil), have the same width B and have the same thickness. With an outer diameter D of the microwave cable of a few millimeters, in particular approximately 1.5 mm, the metal strips 21, 22 preferably each have a width B of a few millimeters, in particular approximately 1.5 mm. Their thickness is preferably a few 1/100 mm, in particular about 0.035 mm.

It has been proven in practice to wind the metal strips 21, 22 each with an overlap of approximately 45% and with an offset per revolution of approximately 0.8 mm.

The effect of double and opposing banding during assembly can be seen in the illustration in Figures 5 and 6 recognize: If the microwave cable is cut to length at one cable end 20a ( Fig. 5 ) and for attaching a coaxial connector (e.g. 18 in Fig. 2 ), the second, outer banding 14 is exposed over a section by shortening the sheathing 16 and the wire mesh 15. Through the (in Fig. 5 However, the overlapping winding of the banding 14 progressing to the left effectively prevents the metal band of the banding 14 from being able to unwind or peel off by itself. In this way, however, the first banding 13 located below is also fixed at the same time and its detachment is prevented.

If the microwave cable is cut to length at the other end of the cable 19a ( Fig. 6 ) and for attaching a coaxial connector (e.g. 17 in Fig. 2 ), the second, outer banding 14 is again exposed over a section by shortening the sheathing 16 and the wire mesh 15. In this case, the metal band of the second banding can unwind because it is not fixed by the overlap at this end. However, this does not apply to the first banding 13 below: Here, due to the opposite winding direction, the same fixing effect occurs due to the overlap as with banding 14 on the other cable end 20a. Since the electrical properties of the cable are essentially determined by the inner first banding 13, the detachment of the banding 14 at the cable end 19a is not critical.

Overall, due to the specially wound tapes 13 and 14 at both ends, the microwave cable 10 can be tailored or cut to length and provided with a plug connector without unwanted deterioration of the properties due to the unwinding of the inner tape 13 which determines the electrical properties.

• Der Kabelaussenleiter besteht aus zwei jeweils überlappenden Metallbändern, welche nicht nur gegensinnig gewickelt, sondern im Vergleich zum Stand der Technik auch in Wickelrichtung umgedreht sind. Die Wicklung der zweiten Bandierung beginnt am Kabelende der ersten Bandierung (vorwärts/rückwärts gewickelt).
• Diese Konstruktion bietet Unempfindlichkeit der Einfügedämpfung beim Biegen, sowie guten Schutz gegen Hochfrequenz Abstrahlung. Zudem ist die Voraussetzung geschaffen für eine optimale Hochfrequenz-Anpassung zwischen Kabel und Verbinder: Der Durchmesser-Unterschied zwischen der Kabeleinführung des Steckverbinders und dem Aussenleiter des Kabels (=Doppelband) kann auf ein Minimum reduziert werden. Dies ermöglicht eine gute Einführung sowie Zentrierung des Kabels zum Verbinder. Das reduziert HF Reflektionen (Rückflussdämpfung) weil Impedanz-Abweichungen so minimiert werden.
• Die gegensinnig gewickelten Bandierungen (Doppelband) mit entgegengesetzter Wickelrichtung bringen Vorteile beim Konfektionieren: bei beiden Kabelenden ist immer eine Wicklung aufgrund der Überlappung selbstfixierend. Bei gleicher Wickelrichtung oder Einfachband wäre dagegen immer nur ein Kabelende selbstfixierend. Ohne diese Selbstfixierung geht beim Ablängen des Kabels die Bandierung auf, der Durchmesser wird also grösser. Eine Verbinderbestückung ist dann nur unter der Bedingung möglich, dass die Kabeleinführung des Verbinders einen genügend grossen Durchmesser aufweist. Dann ist jedoch die Zentrierung des Kabels im Verbinder über das Band nicht mehr gegeben, was zu Impedanzabweichungen und somit HF-Reflexionen führen kann. Zudem stellt der grössere Innendurchmesser der aufgegangenen Bandierung ebenfalls eine elektrische HF-Störstelle (Impedanzabweichung) dar, was zu HF-Reflexionen führt. Das gelockerte Band kann ausserdem Instabilitäten der Einfügedämpfung verursachen.
• Das Doppelband bringt ausserdem wesentlich mehr (mechanische) Stabilität als ein Polymer-Skin über dem Band.
• Das Doppelband aus Metall hat gegenüber einer Fixierung mittels isolierendem Band (z.B. aus Kapton®) bei der Verbinderbestückung den Vorteil der wesentlich einfacheren Konfektionierung (Lötung). Beide Metallbänder werden zusammen verlötet. Ein Kapton®-Band oder Polymer-Skin hingegen müsste in einem separaten Vorgang (per Hand oder mittels Laser) zuerst abisoliert werden, damit das darunter liegende Metallband verlötet werden kann.
• Das Mikrowellenkabel kann z.B. bei Kabel-Assemblies für Test & Measurement eingesetzt werden, insbesondere im Zusammenhang mit Mehrfach-Koaxialverbindern, wie sie in der Druckschrift WO 2009/111895 A1 beschrieben sind.
• Insgesamt ergibt sich mit der Erfindung ein HF-Koaxialkabel mit hohen Anforderungen an Stabilität der Einfügedämpfung, optimale HF-Anpassung zum Verbinder, wirtschaftliche Konfektionierbarkeit und sehr gute Schirmdämpfung.

Overall, the peculiarities and advantages of the invention can be summarized as follows:

• The outer cable conductor consists of two overlapping metal strips, which are not only wound in opposite directions, but are also reversed in the winding direction compared to the prior art. The winding of the second banding begins at the cable end of the first banding (wound forwards / backwards).
• This construction offers insensitivity to the insertion loss when bending, as well as good protection against high frequency radiation. In addition, the prerequisites for an optimal high-frequency adjustment between cable and connector are created: The difference in diameter between the cable entry of the connector and the outer conductor of the cable (= double band) can be reduced to a minimum. This enables a good introduction and centering of the cable to the connector. This reduces HF reflections (return loss) because impedance deviations are minimized.
• The bandings wound in opposite directions (double band) with opposite winding direction have advantages during assembly: with both cable ends, one winding is always self-locking due to the overlap. With the same winding direction or single tape, however, only one end of the cable would always be self-fixing. Without this self-fixation, the banding opens when the cable is cut to length, so the diameter becomes larger. A connector assembly is then only possible under the condition that the cable entry of the connector has a sufficiently large diameter. Then, however, the centering of the cable in the connector via the tape is no longer given, which can lead to impedance deviations and thus RF reflections. In addition, the larger inside diameter of the broken banding also represents an electrical HF interference point (impedance deviation), which leads to HF reflections. The loosened band can also cause instabilities in the insertion loss.
• The double band also provides significantly more (mechanical) stability than a polymer skin over the band.
• The double band made of metal has the advantage of considerably simpler assembly (soldering) compared to fixing by means of an insulating band (e.g. made of Kapton®) when assembling the connectors. Both metal bands are soldered together. A Kapton® tape or polymer skin, on the other hand, would first have to be stripped in a separate process (by hand or using a laser) so that the metal tape underneath can be soldered.
• The microwave cable can be used, for example, in cable assemblies for test & measurement, in particular in connection with multiple coaxial connectors, as described in the publication WO 2009/111895 A1 are described.
• Overall, the invention results in an RF coaxial cable with high requirements for stability of the insertion loss, optimal RF adaptation to the connector, economical assembly and very good shielding attenuation.

List of reference symbols

10

Microwave cables

11

Inner conductor

12

dielectric

13.14

Banding

15th

wire mesh

16

Sheathing

17.18

Coaxial connector

19.20

Cable end

19a, 20a

Cable end

21.22

Metal band

23

Overlap area

24

connection cable

B.

width

D.

Outer diameter

L.

length

w

Increment

Claims (16)

1. Microwave cable (10) for a frequency range from 0 Hz to at least some 10s of GHz, comprising a central inner conductor (11), a dielectric (12) concentrically surrounding the inner conductor, an outer conductor (13, 14) concentrically enveloping the dielectric (12), and a sheathing (16) concentrically enclosing the microwave cable (10) on the outside, wherein the outer conductor comprises two electrically conductive bandings (13, 14), wound one on top of the other, and the bandings (13, 14) are in each case wound in an overlapping manner, characterised in that, a first banding (13) of the two bandings (13, 14) is applied, starting at a first cable end (19) and proceeding to a second cable end (20), and a second banding (14) of the two bandings (13, 14) is applied, starting at the second cable end (20) and proceeding to the first cable end (19).
2. Microwave cable according to Claim 1, characterised in that the bandings (13, 14) are wound with opposite directions of rotation.
3. Microwave cable according to Claim 1, characterised in that a concentric wire mesh (15) is arranged between the outer conductor (13, 14) and the sheathing (16).
4. Microwave cable according to one of the Claims 1 - 3, characterised in that, the bandings (13, 14) are in each case composed of a metal tape (21, 22).
5. Microwave cable according to Claim 4, characterised in that, the metal tapes (21, 22) have the same width (B) and the same thickness.
6. Microwave cable according to Claim 5, characterised in that the microwave cable (10) has an external diameter (D) of a few millimetres, in particular approx. 1.5 mm, in that, the metal tapes (21, 22) each have a width (B) of a few millimetres, in particular approx. 1.5 mm, and in that, the thickness of the metal tapes (21, 22) is in each case a few 1/100 mm, in particular approx. 0.035 mm.
7. Microwave cable according to Claim 4, characterised in that the metal tapes (21, 22) consist of the same material.
8. Microwave cable according to Claim 7, characterised in that the metal tapes (21, 22) consist of copper and are silver-plated on the surface.
9. Microwave cable according to Claim 6, characterised in that the metal tapes (21, 22) are in each case wound with an overlap of approx. 45% and with an offset per revolution of approx. 0.8 mm.
10. Microwave cable according to Claim 1, characterised in that, the sheathing (16) consists of FEP (fluorinated ethylene propylene).
11. Method for the manufacture of a microwave cable (10) according to Claim 1, comprising the following steps:

    a) Provision of an output arrangement (11, 12) of an inner conductor (11) surrounded by a dielectric (12), which output arrangement (11, 12) extends with a prescribed length (L) between a first cable end (19) and a second cable end (20);

    b) Application of a first banding (13) by means of an overlapping wrapping of the output arrangement (11, 12), with a first metal tape (21), starting at the first cable end (19) and proceeding to the second cable end (20);

    c) Application of a second banding (14) by means of an overlapping wrapping of the output arrangement (11, 12) provided with the first banding (13), with a second metal banding (21), starting at the second cable end (20) and proceeding to the first cable end (19); and

    d) Application of a sheathing (16) onto the output arrangement (11, 12) provided with the two bandings (13, 14).
12. Method according to Claim 11, characterised in that the first banding (13) is applied with a first direction of rotation and in that the second banding (14) is applied with a second direction of rotation that is opposed to the first direction of rotation.
13. Method according to Claim 11 or 12, characterised in that before the last step (d), the output arrangement (11, 12) provided with the two bandings (13, 14) is enveloped with a concentric wire mesh (15).
14. Application of the microwave cable (10) according to Claim 1 in a connecting cable (24), which has a coaxial connector (17, 18) at each end, characterised in that the outer conductor of the coaxial connector is electrically conductively connected to the exposed outer conductor (13, 14) of the microwave cable (10).
15. Application according to Claim 14, characterised in that the outer conductors of the coaxial connectors (17, 18) are in each case soldered to the outer conductor (13, 14) of the microwave cable (10).
16. Application according to Claim 15, characterised in that in the microwave cable (10), a concentric wire mesh (15) is arranged between the outer conductor (13, 14) and the sheathing (16), and in that, the outer conductors of the coaxial connectors (17, 18) are in each case soldered to the outer conductor (13, 14) of the microwave cable (10) through the wire mesh (15).

Images