DE1490479A1 - Head for high frequency currents - Google Patents

Description

DR. MÜLLER-BORi DIPL.-ΙΝΘ. GRALFS 1490479

DIPL.-PHYS. DR. MANITZ DIPL.-CHEM. DR. DEUFEL

PATENT LAWYERS

P 14 90 47911 Munich, £ 3, Aug. '»368

Bol / pa - S 492

SUBMARINE CABLES LIMITED
London WC 1, England

Conductor for high frequency currents

ΓΙΟ CD

The invention relates to an electrical conductor for _o

High frequency currents and a process for producing the «

Head. <°

The invention provides a conductor for telecommunication purposes that has superior electrical properties over a frequency range of a few megahertz. Due to the improved performance, such a conductor is particularly suitable for use in Undersea cable systems with repeaters where there is a heavy cable or a short distance between them the intermediate amplifiers practical difficulties entail.

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The invention practically enables the creation of additional subsea television channels and carrier-stream telephony circuits or when broadband operation is not required can be a much thinner cable than the usual cable or it can have fewer repeaters can be used without reducing the overall performance will. Although the invention is particularly suitable for use with coaxial cables in submarine cable systems, its scope is not limited to such use.

The invention therefore provides an electrical conductor for high-frequency currents, the outer surface of which coincides at least in part with an imaginary circumscribing cylindrical surface which is coaxial runs to the ladder. The conductor consists of several parallel-connected and separately insulated Metal cores that are systematically twisted or superimposed so that the individual cores essentially lead the same currents. The cores are dimensioned so that the skin effect is small at the highest operating frequency. The number of within the circumscribing cylindrical surface provided veins is much smaller than that due to the geometry possible maximum and is selected so that the conductor

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resistance at or near the highest operating frequency is between two and 1.63 times a "base resistance" described later, which depends only on the frequency, the thickness of the wire and the diameter of the circumscribing cylindrical surface. The conductor resistance has a minimum value in relation to the number of wires at or near the highest operating frequency and its temperature coefficient essentially disappears at the frequency of the minimum resistance.

Essentially the entire space available within the circumscribing cylindrical surface can be filled by a multi-core wire strand or the like, the reduction in the number of cores below the number possible due to the geometry being achieved by the "space factor" described later "is increased beyond what is usual in conventional practice. Preferably, only part of the available space within the circumscribing cylindrical surface is filled by veins, arranged in the form of a dioht-matched hollow Alinders, the radial diameter of which is large, with a penetration depth of 4 high frequencies flowing into the metal in which the veins exist.

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It can be seen that if the veins consist of ribbons, their width is oriented in the circumferential direction have to be and only present their thickness and not their width to the circumferential magnetic field which is generated by one in the Conductor flowing current was generated. The process for Arranging the ribbons in this manner forms a further part of the invention.

In the conductor according to the invention, the temperature coefficient of the high frequency resistance becomes zero at or near the highest frequency of the transmitted band. Ee may occur naturally, a temperature coefficient of attenuation of the ladders erfindungsgemäfl not produced by other stems such. B. by an outer conductor of a coaxial cable or of changes in the capacitance and the dissipation dee Dielektrikumsj this * effects, however, are quite small. Near the höohsten transmitted frequency is a frequency still be standing, "hen the temperature coefficient of damping wind be zero, and range over a substantial frequency it will be small.

The group delay varies much less in the transmitted frequency band than is the case with herktfaallohsn cables with solid or solid tubular conductors

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is. This is extremely important in television broadcasts and other telecommunications systems where it is undesirable to have transient effects on change based on the group delay. This advantage is due to the fact that the current distribution in the conductors of a cable according to the invention. At high frequency, essentially the same as for direct current is. This point is explained in more detail below.

A substantial reduction in the weight of the cable can be achieved, not only because the conductor according to the invention is unusually light, but because if desired, it is possible to use a given attenuation value with a cable according to the invention a much smaller cable than with known types of cable.

When applying the invention to submarine cables, the main tensioning part of the cable can be made of a non-metallic Material consist, in contrast to conventional clamping parts made of steel, in the form of a reinforcement or a middle steel core executed bind. It consist of For electrical reasons, objections to metallic clamping parts, as will be explained below, in particular i © last case; however, their use is not common to all

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Applications excluded. Such non-metallic clamping parts can consist of an enclosing the outer conductor Outer sheath made of polyethylene terephthalate with oriented molecules or a rope made of polyethylene terephthalate, Polystyrene or fiberglass within the core that supports the inner conductor, or both, i.e. H. a sheath and a rope. These materials are suggested as suitable, but any non-metallic material of the same type can also be used, including the prerequisite that it has a high tensile strength and a Young's modulus that of the metallic Components of the cable is comparable. (It should be noted that the Young modulus for a woven metal part, for example in rope, considerably may differ from that of the solid metal from which it is made). It may be necessary to use plastic materials certain mechanical processes, such as B. cold drawing, subject to an appropriate value of Young's modulus through suitable orientation of the molecular chains to reach. In general, such a process also becomes that of the environment Wear on the cladding is reduced.

The resistance of the conductive wires can be increased by using a stronger material

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of lower conductivity, such as B. polyethylene terephthalate tape or glass fibers are reinforced. the Cores can be connected to the reinforcement material by gluing or a hot rolling process to be described below will.

If the veins are made of wires, the reinforcement will be It is best done so that a few glass fiber strands are braided in when twisting the wires, or that they are inserted into the spaces between the wire strands. Even if the veins consist of ribbons, it is possible to use reinforcing fiberglass strands lh to introduce the spaces. As will be explained later, the wires must be isolated individually, namely preferably by enamelling in order to avoid eddy currents between the cores. You can, however, in proportion long distances so that a small number of broken wires is not too large Loss of conductivity with the corresponding unfavorable Effect on the performance, not only at high frequencies, but also at the zero frequency quenz. Bsi submarine cables usually carry these also the energy required for the Zwisohsnvsrstarkksr. The cable resistance not only has to be low, it has to be do not have to waver as little as possible. To that

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To facilitate connection by means of soldering, a polyurethane coating is preferred because it does not remove the wires needs to be removed. If the wires are made of aluminum, anodized aluminum oxide is preferred as insulation. This oxide breaks down Pressure and therefore does not prevent cold pressure welding. The outer conductor of a coaxial cable can be made in the same way as the inner conductor, and of several insulated twisted cores consisting of wires or tapes, whereby reinforcement can also be provided. The achievable advantage of let however relatively small and both the mechanical durability and the electrical shielding would be reduced Suffer losses. Also, such a cable is weeentlioh more expensive than a cable in which only the inner conductor was a conductor made up of cores according to the invention.

When applying the invention to deep-sea cables, the multi-core inner conductor can be impregnated with a pluidum in front of the strand preparation. Fluid can remain in the viscous state, or it can be thermosetting or thermoplastic, in the latter case with a high Sohmelpunkt. This feature is more important in the event that the conductor consists of wires, al · if he insists on Bandarn. There is a need for you,

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Avoid breakdowns in the core insulation caused by the hydrostatic pressure. Ee is understandable that in the spaces between there are cavities in the veins; if these are not filled with a less compressible medium, the external hydrostatic pressure will ultimately be taken up by the veins and the insulation and possibly even the wires will be cut at the points where they cross. It is known that the The hydrostatic pressure exerted on the inner conductor of the insulation is considerably greater than the outer hydrostatic pressure static druok, which is insulated by the army water is exposed. Due to the pressure equalization caused by the impregnation fluid, the damping changes during and after laying not in an unforeseen way.

In principle, the invention is also applicable to non-coaxial £ abel applicable, e. B. to those in the form of a shielded pair are formed. In this application, care must be taken to ensure that the wires are arranged in such a manner that, considering the shape of the magnetic field, the least possible eddy current loss occurs. Ribbon-shaped ^ Cores must therefore be arranged on the circumference with respect to each conductor and not with respect to the cable shield.

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It is known, however, that for a given outer diameter cables of the coaxial construction have the greatest bandwidth have and that the coaxial design has great advantages in terms of mechanical strength and resistance to Have twists during the laying and picking up of submarine cables. Because of this, the coaxial Construction preferred unless there is some exceptional reason for using a different shape.

Further advantages and details of the invention emerge from the following description of exemplary embodiments with reference to the drawing; in this show:

1 shows a cross section of an embodiment of a Cable according to the invention, in which the arrangement of the inner conductor is shown, the armouring but is not shown as it is not always required

Fig. 1a shows another embodiment of the cable core, at which has a clamping part installed,

Fig. 2 shows a cross section of a cable according to the second embodiment of the invention, in which instead of the fine wires shown in Fig. 1, tapes are used that

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2a, 2b and 2c show the method for offsetting or superimposing the bands according to FIG. 2,

Fig. 2d shows another method of offsetting or superimposing the bands which

Figures 3 and 3a show the notations used in the mathematical treatise,

4 shows a somewhat complicated factor F as a function the dimensions of the cavity occupied by the inner conductor, which justifies a certain approximation to the mathematical part of the To simplify the treatise,

5 shows the change in conductor resistance as a function the number of strands, the resistance value of the Metal (taking into account the temperature) and the geometry of the cable, and

Fig. 6 is a graph useful for numerical Solutions of equation (36) mentioned later.

According to Fig. 1, the core of the cable is preferably made up of polythene (polyethylene) rod 1, which has a meoha

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Niche support for an inner conductor 2 forms. The latter consists of a number of strands 3, for example twenty, which are arranged in one layer. Every Stranded wire can consist of 100 to 200 fine, enamelled copper wires, each with a diameter of is about 0.023 mm (0.001 inches). The strands can consist of ordinary stranded wire and be formed by successive twisting of three units, or a combination of so-called bundled conductors and stranded wire can be used. The structure could for example start with bundles of seven wires that have been twisted arbitrarily and instead of individual ones Wires are used, with which the usual stranded wire begins. The strands can include reinforcement such as fiberglass.

The gaps in the inner conductor can be filled with a connector 4 leg, which is made with polyethylene and Paint is compatible, such as those commercially available under the trademark "Telcompound"; or it can be a thermosetting or a thermoplastic compound with a high melting point or a monomer with an accelerator to aid polymerization can be used. In addition, a part of the space between the The strands are filled with glass fibers, which are used as bridles

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be used. The compound can either be introduced in a separate operation or shortly before it enters the machine which is extruding the polythene insulation 5. The outer conductor 6 is over the insulation attached in its position. It can be of the conventional type and consist of copper or aluminum tapes attached in one long lay are; it can also consist of a layer of copper or aluminum strip material in the form of a drill is bent. The pipe can be welded along the seam and then pulled down onto the polythene, as shown in British Patent Specification 884,747. On the other hand, the longitudinal tape can overlap and not welded, provided that suitable means are provided to prevent the overlap from opening when the cable is bent. It Other metals, in particular alloys, can also be used.

An outer casing 8 made of plastic can be placed over everything. This is essential for submarine cables, if the return conductor 6 is made of aluminum or another metal easily corroded by seawater. In In this case, a corrosion protection 7 can be applied to the aluminum before wrapping, in the usual way

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wise in the form of an impregnated textile tape. Wrapping may also be required under other circumstances be e.g. B. as a binder for a non-welded longitudinal band made of copper. If the outer conductor is made of copper or another semi-precious metal, it can remain in contact with the seawater; this is absolutely common when the cable is to be reinforced.

The outer casing 8 can be made of polythene. However, it may depend on the environmental conditions or other materials can be chosen for mechanical reasons, as will be explained below.

The invention is not primarily concerned with the mechanical properties of the cable, in particular with its tensile strength, its weight and its torsional properties. These properties may be of little importance even for some applications. When used underwater however, it is necessary to provide heavy armor to keep the cable from moving or to protect against chafing in shallow water. On the other hand, tensile stress and torsional properties may be required so that the cable can be placed in deep water and picked up again. Around Achieving these goals are at different times

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various procedures over the past century has been proposed. Some of these techniques are typically applied to traditional cables. However, not all of the known methods can be applied to the cable according to the invention; they can even be opposed to are one of the main objectives of the invention, namely the transmission of television signals. That is why it is necessary to set up some guiding principles that will help with the mechanical structure of the inventive cable must be taken into account. These are as follows:

a) If the constancy of the group delay is important, it is not permissible to use a non-superimposed metallic To attach train part in the space occupied by the soul 1. There are no concerns about carrier telephony. The change in the group delay results from this ^ that the tension member signal current at low frequency conducts, but not at high. This change in current distribution is associated with a change in inductance of the circuit connected, which is formed by the multi-core conductor and the tension member connected in parallel. This inductive change in turn causes a change in the running time.

b) Because fine wires are only stretched a few percent

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before they tear, it is important that their elastic limit is not significantly exceeded. Fortunately, the twisting of the conductors according to the invention results in a certain Lowckerung, so that some stretching of the strand is possible before the strands themselves are stretched.

c) The core on which the inner conductor is arranged, must have a smooth surface which is impervious to the bonding compound and water to eat in order to avoid abrasion to avoid the penetration of the connecting compound 4 if it remains liquid, and the possible penetration of sea water between the insulated wires in the Falb of an error '.

What was said above under a) also applies in principle to external metal clamping parts, namely in those cases where where a multi-core conductor is used and the group delay must be kept constant. In present However, it is definitely from Seewaeser or Eide probable that there is a guiding path | there is usually an outer shield so that the additional change in the group running time, which is carried out by the outer metallic clamping part caused fdrd, from is of little importance for this reason.

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The possibility of using non-metallic clamping parts, is limited by the statements made under b) above and by the following considerations:

In the case of an assembled structure, as in the case of the cable according to the invention, all parts must stretch by the same amount under a tensile force. If now f and f. The voltages in some parts of the cable, e.g. B. are in the conductor or in the tensioning part if F and F ^ are the corresponding stresses at their corresponding elasticity limits, and if E_ and E ₄ . are the moduli of elasticity (Young's modules), then according to Hooke's law:

Elongation = F _c / E _c = f / E ₄ .

If K _Q » ^F c / ^E ₀ ^{and K} t ^{= P} t / ^E t are ^{the Dennun} 8 ^{s at the} elastic limit, we get:

^K c ^f c / ^p

If K _- and K ₄ . are of the same order of magnitude, then

C w

there are no difficulties whatsoever, and the cable component and the tensioning part both reach their elasticity limits with the same tensile force and elongation, ie

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In the case of a large number of non-metallic materials, however, the value of K ^ is often very different from the corresponding one Value of metals, possibly by two orders of magnitude. This would inevitably become a very lead disadvantageous design, in which the tension part is only stressed to a small fraction of F.

There are at least three materials whose properties appear suitable for use as fixtures let, namely glass, polystyrene and polyethylene terephthalate; the latter material is e.g. B. under the trademarks "Terylene", "Dacron", "Melinex", "Mylar" are known. Glass fibers can be used as a twist-free rope may be used provided that they are suitably protected from moisture. the end for this reason they are suitable as part of the core of the cable, as shown in Fig. 1a. As a non-metallic However, polyethylene terephthalate is preferred for the clamping part. It can be used in the form of oriented fibers or strips and for this reason are used as part of the soul or as an outer covering or for both. In current practice, a tape would be used as an outer wrapper by means of Seam welding has been brought into pipe form. With the use of advanced procedures, there is hope

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to be able to use this material in the form of seamless tubing, as is currently the case with polystyrene and others is possible. For this purpose, a thick casing is first produced by means of extrusion, the one slightly larger in diameter than the outer diameter of the outer conductor and other external elements. The cable is fed through the middle of the extruder nozzle. The envelope has a very loose fit on the Cable. The casing is then stretched in the radial direction by means of a mechanical stretching device or by means of air pressure stretched. Then the sheath is pulled in the longitudinal direction, due to the fact that the cable speed is several times larger than that of the large diameter pipe. The wrapping is thereby subjected to a stretch of about 500 # and thus sits tight on the cable. Such a covering is tough, light and free from torsion effects.

If the outer conductor is of the usual kind, he can leg formed so that it serves as a tensioning part. British patent specification 892 281 describes, for example, the Use of copper zirconium alloys in submarine cables; these alloys have both a high conductivity as well as a high tensile strength. Copper beryllium, copper cadmium and copper tellurium can also be used

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be used. British patent specification 884,747 describes the manufacture of a metal envelope from strip material by means of argon arc welding, the Sheath is then pulled onto the cable. Copper-coated steel and aluminum alloys coated with pure aluminum are other metals that combine high tensile strength with good conductivity at high frequencies. It should be noted that the effective modulus of elasticity for the outer conductor can be significantly higher than that of the inner conductor, due to the twisting, to which the latter is necessarily subject. It can therefore easily happen that the outer conductor, although this is more pliable than the part turns out welohee most likely to be damaged by tension. This point must be taken into account when using a nonmetallic Clamping part is used.

In summary, it can be seen from the above considerations that the required tensile strength for deep-sea cables can be achieved in very different ways. In this case, the outer conductor may be modified to the extent 6, that a strip is used made of a special alloy or a bimetal, or daft an additional clamping part either in the position 9 of Fig. 1a, or provided outside of the outer conductor.

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In the latter case, the clamping part can be made of metal or

consist of a non-metallic material and advantageously be of a twist-free nature. However, a sheath 8 made of polyethylene terephthalate is preferred.

If - as in some cases - the transmission level is very low, it can come from the outer conductor and from the seawater The shielding effected will not be sufficient to avoid a noise as a result of atmospheric and by human To prevent interference caused by interference. In such a case, an additional Shielding provided over a short distance, namely in the form of a BI jacket or a highly permeable one Ribbons or both. In addition, the necessary mechanical protection against wear and tear by tidal currents is then Surf, and ice provided. Such a procedure is also applicable to the cable according to the invention applicable, and thus requires additional measures to the basic elements shown in FIG.

In Figs. 2 and 2a to 2c, another embodiment of the invention is shown in which the inner conductor consists of several ribbons instead of wires. The tapes are in knots consisting of two stacks 21 and 22

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units arranged as shown in detail in Fig. 2a. Each band is twisted in turn at intervals from the top of one stack 21 to the top of the other stack 22 and from the bottom of 22 to the bottom of 21 or vice versa. As a result of this measure, each band takes up each radial position in turn, and its width is always oriented in the same circumferential direction. The stacks 21 and 22 are shown flat in FIG. 2a for the sake of clarity, but in practice they will be slightly bent in order to adapt to the cylindrical shape of the carrier 1. The tapes can be insulated with lacquer or with layers of tape-shaped insulating material and, in order to achieve greater mechanical strength, can be connected with a suitable adhesive. Where narrow bands are used, the twists can be achieved by bending over the edge and allowing a certain amount of wrinkling on the inner edge of the bend. Alternatively, as shown at 23 and 24, two diagonal pleats can be folded into the tape. Each inner conductor preferably consists of two stacks each comprising a half cylinder. The strips are preferably made of copper about 0.025 mm (0.001 inches) thick or less and can be reinforced in the manner mentioned above or by means of the hot rolling process described below. There can be about 10 tape thicknesses in each stack,

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so that in the semi-cylindrical arrangement described, the number of wires can be reduced from about 2,500 in the first embodiment to 20 in the second. From the From an electrical point of view, the two embodiments are qualitatively similar. A tape measuring 3 mm χ 0.025 mm (0.12 χ 0.001 inches) has approximately the same properties as 120 side-by-side wires of 0.025 mm (0.001 inchee). However, the space factor will be less, d. H. the veins would be more tightly packed. So there are advantages in terms of reducing the Number of parts and improvement in electrical properties. Because of this, it became its own device Developed for laying tapes in the manner described. This device is therefore also part of the Invention.

The device required can be based on

a strand machine with reverse rotation are built, which carries, for example, 20 reels of tape in such a way that the axes of the reels are always in the same transverse direction, for example in the horizontal, this machine would produce the belts in the form shown in Fig. 2b place. By passing the bundle of ribbons through appropriately shaped nozzles, the circular shape shown in Fig. 2b can be gradually transformed into the shape shown in Fig. 2c be transferred. This would be wound around the soul.

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The laying of the folded tapes on the core can be done in a separate operation, or the two operations can be combined, with the machine folding the belts as a whole the soul would rotate. Other equivalent machine arrangements are known to those skilled in the art, such as, for example the series connection of the first machine with a strand machine in tandem. With such a combination it may be desirable to deviate somewhat from the above-mentioned arrangement with reverse rotation, the the ribbon-forming nozzles and the transverse axes of the spools rotate slowly to remove twists in the finished product Bring tape before it enters the axial tube of the strand machine, which the twisted tape and the core collapses.

The process of folding the ribbons is considered new, but not the process of wrapping the ribbons around the soul} Me unless, the operations would be combined in the manner noted above. It should be noted that it is temporary it was common practice to use a stranded conductor for submarine cables to reduce the risk of breakage, Some bare copper tapes were wrapped around a middle bare copper wire. The tapes were getting there applied with a braid without twisting back,

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which she - as in the second step described above - twisted when hanging up.

In order to facilitate the formation of the conductor, a small spacer element 25 (Fig. 2b) can be inserted. This would consist of a plastic or fiberglass cord running through the center of the tape-braiding machine to be led. One can also insert insulating tape between the conductor tapes by adding a second set of coils with reverse rotation provided for this purpose, or by simply putting the conductor tape and electrical tape together wound on the same bobbins.

The following is another method of twisting thin ribbons and joining them into one Structure described with acceptable mechanical strength,

In principle, the metal band or bands are applied to a hollow, elliptical or cylindrical, tubular base made of a thin insulating material, which is slidably mounted on a metal mandrel of the same shape. The hollow insulating base can consist of one or more thin strips of a thermoplastic material, which are preferably provided with an adhesive on one side and helically with the adhesive side outwards on the metal mandrel

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are wound so that a thin-walled tube is formed. This tube is made of as it is being formed the Βοχη deducted, the mandrel preferably lightly is tapered and suitably shaped at the end to facilitate this process. On the other hand, the Tubes can also be produced by extrusion in a die placed close behind the mandrel, as in the known processes for the production of polystyrene films.

While the tube is still stored on the mandrel, metal straps are helically attached to the one with the adhesive provided outer surface attached, preferably in a single layer with a catch through Overlap or braid. If more than one layer of tapes is applied by overlapping, or if If multiple braiding is used, one of the twisting methods described above must be used, otherwise the advantage based on the use of a thin tape can be forfeited.

It is also possible to use metallic longitudinal tape or tapes in plastic tapes provided with adhesive insert so that the above two operations are combined, i.e. H. the plastic tape will formed into a tube with the same blow as the metal band.

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The hollow plastic base comes along with the daruaf attached metal straps are peeled off the mandrel and gradually flattened, this is the end of the dome shaped to facilitate this process. The flattened tube obtained in this way may have some Include longitudinal reinforcements, such as fiberglass, fed through the central portion of the dome during the operations described above will. The flattened tube is heated and pressed, preferably by passing it through heated rollers is guided so that the plastic base flows into the spaces between the metal bands and connects them to each other and to the reinforcing glass fibers, if these are provided, whereby a wide composite band is created, the width of which is, for example, more than ten times the Umfangeθ of the core can.

The composite tape produced in this way is attached to the soul by stretching it in a fine length Beat is overlapped so that it envelops the soul in several turns, for example ten or more. Because of this structure, the path of the belt or one leads of each band, if several are provided, from the outer edge of the flattened tube across it the turns until it is the inner edge of the flattened

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Reaches the tube that is in contact with the soul, and then returns on the other side to the outer edge back so that it adopts each radial position in turn.

Alternatively, the flattened tube can be folded in the longitudinal direction, for example in accordion fashion, namely after or preferably before the hot rolling process, so that a thicker, stronger and narrower composite strip is created which can be attached more easily in one long blow to the soul.

It is not necessary that the tapes be made of a solid metal. By so-called "printed circuit method", metallic lamellae can be produced on the insulating base in various ways, for example by printing the surface with an "ink", which contains a silver compound, which by a reduction process or by heating to metallic β Silver is reduced. The conductor can also be duroh through electrolysis, through evaporation of a metal in a vacuum Atomization, such as B. in the production of Waohsplattan for records, or by metal spraying and others Process are produced. Obgleioh such · methods

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already used in connection with the commercial production of capacitors is the quality of the Metal film, unfortunately, is not yet completely satisfactory in terms of its electrical and mechanical properties Properties. However, this concerns details and not the fundamentals; it is to be expected that the printed circuit process did eventually are practically and economically feasible for the purposes mentioned above. Your application would be in that The scope of the invention are.

Pig. Figure 2d shows one form of the above-mentioned flattened tube method. On one with an adhesive provided plastic tape 26 is a conductive part 27 either by gluing a metal tape or metal strips or attached by printed circuit processes. The metallized tape is formed into a mandrel 28a through which glass fibers 29 are passed elliptical tube 28 rolled up. The security is deported and flattened by hot rolling, removing excess plastic material if so is required.

If there are several separate metallized strips on the plastic tape by printed circuitry the same process can be used

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-.3 0-to connect them to each other at intervals.

It was pointed out that the wires forming the cable according to the invention are electrically connected to one another should be in order to keep the effect of fractures as small as possible. If no such connection is carried out would, and for example 50 band breaks would occur in one amplifier section, it would be very probably that no vein would be without a break. With regard to the DC power supply to the amplifiers and this would be highly undesirable for fault localization. For this reason it is necessary that a sufficiently large number of connections is made so that, for example, not more than one ribbon or $ 1 of all wire cores on 100 cores or more probably T.vifiohHi any two connections faulty can be. On the other hand, the connections must be far enough apart so that a large number of overlaps between two connections. Because the connections are a possible source are for weak spots, an excessive number must be avoided.

The compounds themselves can be in a known manner, for example through copper wires coated with polyurethane, the connections through

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Soldering together with Löteinn can be made. If they are made of aluminum, cold pressure welding is used. If the anodizing is strong enough, it tends to they tend to break during the process so that pure aluminum can flow through the break points and thus creates good welded joints.

In the following, the mathematical aspects of the multi-core cable according to the invention are examined, it being shown that a low attenuation constant is achieved and that over a considerable frequency band the temperature coefficient eliminates attenuation can be. The reasons for a reduction in the difference in group delay over the transmitted Volume are also explained.

Summary of the propagation formula

For the sake of convenience, some relationships between the damping constant and the Phase constants and their dependence on the so-called Primary constants summarized.

It is known that the transmission constant F for tine transmission line with uniform properties given the following equation:

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P ² = U + iß) ² = (R + J ^ oL) (G + j £ iC) (1) where is ty

οί. = Attenuation constant (neper per unit of length) = Phase constant (angle in radians per length

unit;

R = resistance (ohms per unit length) L = inductance (henry per unit length) G = conductance (Siemens per unit of length) C = capacity (Fara'd per unit of length)

ίο β 2 ~ H f ■ Angular velocity (angle in radians per second) f «Frequency (Hertz)

The separation of equation (1) into the real and imaginary parts results in ι

(Kf ² - / i ² ) «RG -C» ² LC (2)

(3)

The following expression for the damping B constant is obtained from (3):

Since the phase speed V = (O / ^), and the conductance value normally from the VerletfAktor CTe O / (& jC) for

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- 33 - · the dielectric is derived, one obtains:

^ = \ VCR + \ VOCaLC (4)

The end. (2) the following expression can also be derived for the phase velocity:

- (W ² ) = (RG / fc ² ) - LC ² = LC / 1 (R ^ / & iL) 7 + (ot / Co) ²

or (1 / V ² = LC / 1 - (R ^ / & iL) -7 + (ot / Co) ² (5)

Since with the usual cables at high frequencies and are small, especially the latter value,

-4
which can be around 10, the following expression can be used for V with a negligible reduction in accuracy:

(1 / V) ² = LC ₊ U / w) ² (6)

In the case of the types of cables to which these documents refer, ie large cables with low attenuation that operate at high frequencies, it again turns out that the expression (^ / cj) becomes very small and that the change in attenuation with frequency is a Changes in speed with frequency causes a negligible part of the total

BATH ORIGINAL

9098 03/0957

represents change in speed with frequency. This overall change in speed will therefore caused almost exclusively by the change in inductance, since the capacitance is invariant. The change in the speed causes a change in the group delay, d ß / d Oo, which for example is important when the cable is used to transmit television signals. A feature of the invention is that the change in group delay with frequency is reduced, mainly due to a decrease in the change in inductance with frequency.

When using the approximation for (1 / V) from the equation (6), one obtains for equation (4):

The approximation in the derivation of the second term of this expression is comparatively unimportant, since the second link in any case only represents a very insignificant part of the total attenuation. Except for very specific ones The following approximate expression is sufficient for work:

- J

J CEV (7a)

9098 0 3/0957 bathroom original

* H90479

The above can be summarized in that a reduction in attenuation can only be achieved by reducing the product C R, since it is it is known that the speed at high frequency is mainly determined by the dielectric constant and the permeability of the dielectric is determined and therefore regarded as a constant in a first approximation can be.

It is also evidently advantageous that the damping changes as little as possible with the temperature should change} this could be achieved by reducing the temperature coefficient of R, since C and V do not depend too much on the temperature.

The constancy of the phase delay as a function of the frequency is achieved essentially in that L is independent of the frequency.

Eddy current losses in multi-core stranded wire conductors with a core

In the following consideration, a distinction is made between two types of multi-core conductors, depending on whether they have a core or none, in order to avoid confusion with conventional, non-core conductor types

3AD ORIGINAL

80980 3/095 7

- 36 - the latter can be referred to as "tubular" or "solid".

The resistance of Litzendrahtleitera without a soul and with circular cross-section has already been calculated and the results have been published. The problem is facilitated by the assumption that the magnetic flux is not changed by the eddy currents which it does generated in the strands. In the present example, this assumption can be made for wire cores. Indeed, if the veins get so large that they invalidate this assumption, they would have an unusable one high resistance. The assumption is less reliable with regard to ribbon-shaped cores, but it leads to an overestimation of the high frequency resistance.

The following is a derivative of the resistance multi-core conductor with core specified, in which the type without core appears as a special case in which the Radius of the soul becomes zero.

In the first case it is assumed that the wires are round wires. Ribbon-shaped cores, which are only for conductors with Soul suitability are covered in a later section.

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It is shown, however, that the formulas for tapes differ from those for wires only in relation to the numerical Distinguish constants.

First, it is proposed to calculate the root mean square value of the internal magnetic field over the cross section to determine the current-carrying conductor according to the invention. Then, using the known formulas, the The eddy current loss caused by the field is calculated and the high-frequency resistance of the conductor is derived from this. The high frequency resistance can be reduced to a minimum and its temperature coefficient can be reduced by a suitable selection of the number of wires go through zero. For leaders without a soul, the space factor is considered independent Considered changeable, while for leaders with soul the space factor is fixed due to practical considerations and the diameter ratio is taken as an independent variable. The latter method is preferred.

The magnetic field lying in the circumferential direction is everywhere perpendicular to the direction of the wires, if it is assumed that the strands are not too short. In this Case it can be shown that the power W lost in each wire due to the eddy currents is as follows:

W = H ² jf ³ f ² d _f ⁴ / (32f) erg / cm see.

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The derivation of this equation is briefly repeated below in the discussion of the ribbon-shaped cores. if the specific resistance is fin ohms cm and W in watts expresses, one obtains:

W = H ² fi ³ f ² d _f ⁴ (1O " ¹⁶ ) / (32 ^) (8)

In these expressions is:

H = peak value of the magnetic field (Oersted) and df = wire diameter ip c «.

Ί ■ - ν

In order to be able to calculate the resistance of the entire Xöiter,

ρ
the value of H is required over the entire cross-section.

Since all wires are forced to carry the same current, the current distribution is uniform, as in a massive one Conductor at low frequencies. In addition, the veins are so thin that the skin effect is practically non-existent. A current density I / A can be defined, where I is the total current and A is the cross-sectional area of the hollow cylinder which is filled by the cores, where:

A = F (R ₂ ² - R ₁ ² ) *
Rp = outer radius,
R ₁ = inner radius, i.e. that of the soul (see Fig. 3)

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ORIGINAL INSPECTED

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Thus, the current flowing in an elementary cylindrical shell with a radial thickness dx and a radius χ is dlt

dl = (l / A) -2 7x * dx = 2 I χ dx / (Rg ² - R ₁ ² ) (9)

The contribution dH to the field H is corresponding to this current element ar shell at a radius r greater than x:

dH = 2 dl / r = 4 (1/4) χ dx / (R ₂ ² - R ₁ ² ) (10)

where I is measured in the cgs system (e.m.uj. If r is smaller than x, then dH = 0.

Hence is

H = (4I / r) (R ₂ ² - R ₁ ² ) - ¹ J χ dx,

^R 1

= 2 (I / r) (r ² - R ₁ ² V (R ₂ ² - R ₁ ² ) for I in cgs (, 11) = 0.2 (I / r) (r ² - R ₁ ² V (R ₂ ² - R ₁ ² ) for I in Amp. (11a)

ρ
The mean value H_ of the square of the field is given by:

R ₂

(1 / A) ( H ² x 2 Xr x ^dr

^R 1

R ₂

(0.2) ² (I ² / T) (R ₂ ² - R ₁ ² ) " ³ ((r ² - R ₁ ² ) ^2. (27 (/ r) dr,

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1A90479

R ₂ = 0.08 I ² (R ₂ ² - R ₁ ² ) " ³ Γ (1 ^ -2R ₁ ² r + R ^ / r) dr _t

= 0.08 I ² (R ₂ ² - R ₁ ² ) " ³ [i / 4 (R ₂ ⁴ - R ₁ ⁴ ) - R ₁ ² (R ₂ - R ₁ ² ) + R / log _e (R

Hence, H _m ² = 0.08 I ² F / d ^ (12)

whereby: = 4d ₂ ² (d ₂ ² - c (^ 4 ^ d ₁ ) - <3 F. CVJ log (d, / I ₁ ²⁾ "L ^{2 1/4} . (d ² - t 'd,) l (13)

In the above expressions Bind d «and d ₁ the outer and inner diameter of the hollow cylindrical space, which corresponds to _{the radii R 2} and R _1;

4 shows the variation of F as a function of dj. It fluctuates between the value 1 for d .. = 0 (conductor without core) and two thirds for a thin-walled conductor with a core (d .. almost equal to d ₂ ). It can be seen that if the wall is not too thick, a good approximation is given by the following expression:

F = 1.046 - 0.38 d ^ dg (14)

909803/09 5 7

H90A79

ρ
Substituting the value of H into equation (8) results in the same current loss per cm in each wire as:

W = Ff ³ l ² f ² d _f ⁴ (iO " ⁱ⁸ ) / (rd ₂ ² P) watt / cm (15) = (l ² R ^e ) / (2 n) (16)

there is:

η = number of cores in the conductor,
I = peak current in the conductor, in amperes,
R = increase in resistance due to eddy currents.

Pollich is:

R = (T ³ nf ² d ⁴ F) (10 ~ ⁱ⁸ ) / (2d _o ² ?) (17)

e ι c. \

However, the direct current resistance R _Q is given by the expression:

• R ₀ = (4j) / (nTd _f ² ) Ohm / cm (18)

The effective resistance R _{f of} the conductor is polar
at a frequency f given by:

R _f / R _o = 1 + R ₃ A ₀ = 1 + (7 ⁴ n ² f ² d _f ⁶ F) (i (T ⁱ⁸ ) / (8} ² d ₂ ² )

(19) 1 + (k ₁ n ² f ² d _f ² Fj / (d ₂ ² ) (20)

909803/09 5 7 PHKMNal inspected

- 42 is:

K ₁ -r ⁴ do- ¹⁸ ) '/ (ö ^ ² )

= 4.21 (10) for copper wires, where = 1.7 (10 ~ ⁶ ) Ohm * cm at 20 ° C.

If the dimensions are given in thousandths of an inch and the frequency in megahertz, the following applies:

k ₁ = 1,752 (10 " ⁴ ).

ρ
It can be seen that s! appears in the denominator. This indicates that a temperature coefficient of zero can be achieved.

Calculation of the optimum values for a multi-core stranded wire conductor without a core

The space factor S is now introduced. It is the ratio of the direct current resistance of the vein-shaped Conductor defined as that of a solid wire or pipe conductor that takes up the same space. Under; he neglect the effect of the strand layers is the space factor for a conventional stranded wire or bundled wire Head without core with a total diameter dgt

9GMÖ3 / 09 5 7

ORJGiNALlNSPECTEO

S = (1 / n) (d ₂ / d _f ) ² (21)

= 2.2 for commercial products.

The space factor shows remarkably small fluctuations in practice.

One usually strives to obtain as low a space factor as possible; this applies to the one treated here Use case, however, does not necessarily apply.

Purely conventional stranded wire where F = 1, i.e. H. where there is no soul, the following applies:

R _f = (a / n) (1 + bn ² ) (22)

Here a and b are constants, as indicated in equation (20), since, as you can remember, R is reversed is proportional to the number of wires (see equation (18))

For dR _f / dn * 0, η * b "" ¹ ' ² .

The optimal value for n, for example n _Q , is thus given

1/2 3

1 / n ₀ «χ k ₁ fd _f / d ₂ (23)

909 803/095 7

and the corresponding minimal value of R », for example R »is given by:

R _f0 = 2 R ₀ (24)

For other values of η, i V ^R fo - (V ²ⁿ⁾ I ^{1 + <n} / ⁿ o> ^{2] (2} 5)

Pig. 5 shows the variations of Rf / R _fo as a function of n / n _Q. Since η is always assigned to the number 1 / f in equations (17) to (20), it follows that this figure can be used to calculate RfZRf ₀ for variations of P /? to show where? is the resistivity on which the determination of the optimum is based. For this reason it also describes the effect of the temperature changes, which can be regarded as the equivalent of the changes in ο . Therefore, when the effective resistance is reduced to a minimum, the temperature coefficient of the resistance is zero and it changes sign at that point.

If the optimum value d _{f is} changed, but the ratio d _f / d ₂ remains constant (ie constant space factor and η = n _Q ), the same curve would be more similar

Way apply to changes in (d ^ / d-), where dx. corresponds to the optimal value.

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It is known from equation (24) that R _f = 2 R.

From equations (18) and (23) which R _Q and η

1/2 , and by introducing the value of k ₁ '

from (19) and (20), namely

= T ² (1O " ⁹ ) / (8 ^1/2 5) (26)

the following ' expression is obtained: ^R fo' (

8 ^1/2 f _(f d / d ₂₎ (1 (T ⁹⁾ ohms / cm (27)

= 1649 f (df / dg) ohms per nautical mile, where

f is expressed in megahertz. . (27a)

In practice, the space factor S must be increased by about 4 # to do justice to the stranded layers. This increase also applies to the DC resistance and the Eddy current resistance Taking this into account Fact becomes equation (27a)

R _f0 = 1715 f (d _f / d ₂ ) ohms per nautical mile (27b)

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It can be seen that this result is independent of the specific contradiction
is chosen speaking.

the specific resistance <of the metal, if η is

It was believed that the optimal number of wires can always be obtained. Although there are of course cases where this is impossible, in the Practice no serious restriction.

The space factor S corresponding to η is given by

fd _f d ₂ (28)

The advantage of a multi-core conductor can be seen by comparing the resistance of a stranded wire conductor without a core that of a solid wire of the same diameter can be shown.

The resistance R ~ of a solid wire at high Frequency is by the following known approximation formula given:

R _f8 = 6080 f ¹ ^ Vd ₂ ohms per nautical mile at 20 ° C (29)

_f8

whereby:

f = ■ frequency in megahertz,
dp - outer diameter of the inner conductor in

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Thousandths of an inch, ie it corresponds to d _? in the above treatise and is unrelated to the diameter of the return conductor aa. Therefore:

R _fo / R _fe = 0.282 f ^1/2 d _f (30)

The f is measured in megahertz and d »in milli-inches in the same units as dp * So can For example, a conductor made up of 1.6 mil (46 SWG) wires, about half the resistance of one solid conductor of the same outer diameter at 1.2 megahertz, but dg must be greater than 90 milli-inches, otherwise the space factor S cannot be obtained (see equations (26) and (21)). This This point is discussed further below.

Determination of the optimal values for multi-core Stranded wire conductor with a soul

The consideration for the case of a multi-core conductor according to the invention with a core is more complicated; however, the difference is more quantitative than qualitative. It will be shown that F has a value of about 0.8 rather than 1 and that the optimum resistance approximately 90 i "of that is of a conventional stranded wire without a soul. One can also advantageously do something

909803/0957

use a lower space factor, namely the lowest possible that can be achieved.

In this case the space factor is defined as:

S = (d _o ² - d ^ Vid *. ² η) (21a)

so that

η = d ₂ ² (1 - y ² ) Z (d _f ² S) (3D

y = d

Equation (20) gives:

RfZR ₀ = 1 + (k ^ ² f ² d _f ⁶ F) Z d ₂ ² , - 1 + k ₂ (1 - y ² ) ² <1.046 - Ο.38 y) (32)

using the approximation for F from equation (14) and introducing k ₂ , where j

k ₂ = (k ₁ f ² d _f ² ) ZS ² (33)

From equation (18) we now get}

R ₀ = 4 5Z (^ cIf ² n).
Substituting η from equation (31) gives mant

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H90473

R ₀ = 4 Sy / [rd ₂ ² (1 - y ² )] (34)

= kyO - y ² ) ', (34a)

where ^k 3 ^{= 4} ? 3 / (Td ₂ ).

It follows from (32):

_f = k ₃ / (1 - y ² ) + k ₂ k ₃ (1 - y ² ) (1.046 - O.38y) (35)

The factors k "and k-> do not contain y and can therefore be treated as a constant in the next step j

(iA ₃ ) dR _f / dy = 2y (1 - y ² ) " ² - k ₂ [2y (1.046 - 0.38 y) +

0.38 (1 - y ² )], = 0 for a minimum (36)

It follows:

(1 - Y ₀ ² J * * ₀ + 0.38 (1 - y _o ² ) d / 2y _o ) (36ä)

Here, y ^ P- and dii Optimüiwerte of Y and F. In relation to έίέ relationship "wipe y _Q and F ₀ sieHi Gleichuhgih (1y) and (U) and Fig. 4.

The equation (23j χΜ. (2Ö) show that for din fall Original inspected

H90479

of a conductor without a core an optimal number of cores η and thus an optimal space factor S was determined to give a minimum resistance R ~. In the present However, in the case of a similar reason, an optimum value y of the diameter ratio d-j / dp becomes chosen. These pre-fermentors can be viewed as alternative means for the same end use. It will, however stated that optimizing y is the effective method and that it is therefore more advantageous to <3en technically possible achievable minimum value for S to be used, d. H. the veins as tightly as possible in the hollow cylinder space to arrange. Thus, in the equation (36a), kg, which depends on η and S, becomes due to technical Considerations taken as fixed and the equation used to determine y_ and F. Therefor Fig. 6, in which equation (36a) is graphed, will prove useful.

Substituting kg into equation (32) gives:

^Ο · ^{38 (1} - O < ² V> ~ I "

2 for y ₀ = 1,

1 .8 for y ₀ = 0.6

909§Ö3 / 09Sl ORfGINALtNSPECTED

The approximation used for F and dP / dy in equations (32), (35), (36) and (36a) does not apply to y = O. Aus
However, it is already known from equation (24) that when y = 0, η = n _Q and S = S _Q , then Rf _o / R _o = 2.

It is concluded that Rf _o / R _Q is not

far from 2. This leads to an appropriate approximation for equation (32).

Equation (34a) can be written in the following form:

(1 - y ² ) = k _e / R ₀ (34b)

Using this relationship, (32) becomes:

- 1 = k ₃ ² k ₂ F / R _o ² (32b)

By pulling the square root on both sides and
Multiplying by R- gives:

(k ₂ F) ^{i / 2} u / (u - 1) ^1/2 (32c)

whereby

u = Rf / ^R ₀

909803/0957

Under optimal conditions one can write: u _o = 2 - h,

where h is small. With an extension of

-1/2
(1 - h) ~ ' by the binomial theorem we have shown that the expression ^u _o / ( ^u _o - Ό very closely approximates 2. Under all practical conditions the error does not exceed 1 $. Hence, the following result can be obtained:

R _f0 = 2 k ₃ (k ₂ F ₀ ) ^1/2 (27c)

It is convenient to define a "base resistance" R _Q0 , the DC resistance when y = 0 and F = 1, where:

^R oo - ^k 3 ^k 2 ^{i / 2 (27d)}

The following applies to wire cores:

R ₀₀ = ^{2 1/2} f _(f d / d ₂₎ 10 ~ ⁹ Ohm / cm (27e)

Hence:

R _f0 = 2 F _o ^1/2 R ₀₀ Ohm / cm (27f)

(For a conductor without a core, which is set up for the optimal number of cores and space factor , R. and R.

ο oo

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identical, since in this case k is ₉ m 1 under optimal conditions.)

The equations (27), (27a) and (27b) can therefore also be applied to conductors with core and wire cores,

1/2

if the value of R- thus obtained is multiplied _{by ^ 0.} This also proves that it is more effective to use a coreed conductor than to space the wires using a high space factor.

Eddy current losses in multi-core ribbon conductors

The theoretical treatment of ribbon conductors differs from that of stranded wire conductors only with respect to certain numerical factors, apart from the fact that a ribbon conductor without a core is impractical for obvious mechanical reasons.

Two elementary disks of the band-shaped wire are considered, with a width b _f and a thickness dz, both of which are arranged at a distance ζ from the center line, to which they run parallel, see FIG. 3a.

The resistance R-, which is formed by these two disks in series, is:

Β. * 2 ./(bf 4s) Ohe / cm.

90öaO3 / 0957

The maximum induced voltage V _T per cm is: V _L = 2 ζ H (10 ~ ⁸ ) volts / cm.

The mean energy loss dW per cm is:

dW = 1/2 V _L ² / R _L = 1/2 (b _f / 2 ί) 4 « ² H ² (10" ¹⁶ ) z ² dz,

iö H ² (i0 " ⁱ⁶ ) z ² dz watt / cm.

By integrating ζ ■ 0 into ζ = 1/2 t ~, where t _{f represents} the thickness of the wire, the following equation is obtained, which is also used for losses in magnetic cores:

i / 2t _f to ² H ² O (T ¹⁶ ) (■ ζ ² dz,

³ (1O " ¹⁶

t _f ³ (1O " ¹⁶ ) (8a)

Equation (8) can be set up in a similar way by writing:

b _f = 2 (1/4 d _f ² - z ^{2) 1/2,}

and integrated from 0 to 1/2 d ~. It is easy to see that the difference between (8) and (8a) is only Lich that the maximum thickness d _f in the case of a wire occurs only at the median plane, and that

003603/0957

the loss therefore decreases rapidly towards each side. The effective thickness is therefore considerably less than d _f .

Comparing the equations (8) and (8a) is to be noted that the cross-sectional areas for a round wire Tfäf 1/4 and for a band b ~ t _f. The loss per cm and per unit of metal area is therefore:

(1 / 24P) & 3 ² H ² t _f ² (10 " ¹⁶ ) for a ribbon, '(1/32 ^) Cc ² H ² t _f ² (10" ¹⁶ ) for a wire.

Palis a wire is flattened by rolling, even if it is so small that its width does not exceed the original diameter, the ribbon thus formed will already show less loss than the wire. It will be appreciated that the rolling process can proceed substantially further so that there is considerable benefit to a strip for a given metal cross-section. Another advantage of the tape is the lower space factor.

It can be seen that has been tacitly assumed in the derivation of the above equations (8) and (8a) and also in the equation (12), in that the permeability of the medium is equal to 1 and dimensionless iet, in compliance

909803/0957

Mood with the cgs system. The resistance per unit length has the same physical dimension as the frequency, see equations (27), (27a), (27b) ... (27h).

2
If one introduces H from equation (12) into equation (8a), one gets the following result:

W = 8 I ² (F / d ₂ ² ) ^ ² t _f ³ (b _f / 24 ^) (10 ~ ¹⁰ ), = 4Ii ² FI ² f ² t _f ³ b _f - (1O " ⁱ⁸ ) / ( 3 d ₂ ² ^), (15a)

2
= 1/2 I ² R _e (1 / n) (16)

R ₀ = (.2n / l ² ) (4T ² FI ² f ² t _f ³ b _f ) (1O ~ ⁱ = 8T ² η F f ² t _f ³ b _f (1O " ⁱ⁸ ) / (3 d ,, ² ^) (17a)

however, R _Q = / (nb _f t _f ) (18a)

= 1 + (ö7 ² n ² F f ² t _f ⁴ b _f ² ) (10- ¹⁸ ) /

(3 d ₂ ² ^ ² ) (19a)

= 1 + (k ₁ n ² f ² t _f ⁴ b _f ² F) d ₂ ² (20a)

where k ₁ = 8 ^ T ² (10 " ⁱ⁸ ) / (3 e ² ) for a band, compared to:

k- | = Tf ⁴ (10 ~ ⁱ⁸ ) / (8 ^ ² ) for a wire.

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ORIGINAL INSPECTEO

H9Ö479

The space factor S is now:

S = (i / n) (i / 4fd ₂ ² ) (1 - y ² ) / (b _f t _f ) η = (1 / S) (1 / 4Td ₂ ² ) (1 - y ² ) / (b _f t _f )

Substituting η into equation (19a) using equation (31a) one gets:

(21 b) (31 a)

R _f / R _o = 1 + k ₂ (i -

however:

compared to:

y ² ) ² F.

O0 " ¹⁸ ) / (6

(32)

for a band (33a)

^{for one}

As before you get:

R ₀ = k ₃ / (1 - y ² )

however

(34a)

2
k, = 4P S / (xd ₂ ) on the one in equation (21b)

given value of S must be based.
The following applies:

_f / d ₂

) (27g)

ti

o ^r öo

" ⁹

(t _f / d ₂ ) (10 " ⁹ )

(27h)

ORIGINAL INSPECTED

H90479

Equations (27), (27a) and (27b) can also be used in this Pall if the value of R _fQ thus obtained is multiplied by (4F _Q / 3) 'and if t _f is substituted for d _f . The equation (27b) contains a loss amount of 4 ° ^f » . This amount may need to be increased slightly for a tape, depending on the particular twisting method used, as will be understood by those skilled in the art.

Comparison with a common ladder

It is known in the art that the resistance R- at high frequency, when there is a high amount of skin effect, is given by the following formula, which refers to a Copper conductor at 20 ° C. The same result is obtained regardless of whether it is hollow or solid, under the prerequisite that the radial thickness is much greater than the skin depth.

R = 6080 _fs f ^1/2 / d ₂ ohms per nautical mile, (29)

_fs

where f = frequency in megahertz

dp = outer diameter of the conductor in thousandths of an inch.

If one compares this equation with equation (27b) and equations (27e), (27f), (27g) and (2? h) in

900003/0957

Taking into account, one obtains the following results:

^R fo / ^R fs ^{= k} w ^p ₀ ^{1 // 2f1 // 2} d _f for wire-shaped cores (30a). . . _T = k f _o ^1/2 f ^1/2 _f t for tape-shaped wires (37)

there is:

k _w = (1715/6080) = O.282 for an amount of

4 "Α for the injury,

k _t = (2000/6080) = O.329 for an amount of

5 % for loosing

where f is given in megahertz and d ~ and t _f in thousandths of an inch, like dp in equation (37).

These numbers show that it is apparently possible to set the high frequency resistance to any desired number Reduce with the help of appropriately chosen cores. In the technical literature it is stated that a loser Conductors may have half the resistance of a solid conductor of the same diameter mentioned this task only in the form of a goal which has not yet been achieved. The possibility of a high frequency resistor to achieve that is less than half the resistance of a solid conductor is not known, although some references to the use of

909803/0957 ° * k * inal wspected

stranded ladders were given. This is not surprising as all previous attempts have stranded conductors based on empirical procedures, and for this reason the optimal solution was not found. -.

Inductance of a wire-shaped conductor

If the skin effect has a strong effect, as in a solid conductor, then the reactance corresponding to the internal inductance is equal to the high-frequency resistance, so that the internal inductance with.; the square root of the frequency becomes smaller. This is the case because the conductor, which is viewed as a medium in which electromagnetic waves propagate radially, can be viewed as such a transmission line that has only an inductance L * and a conductance G ¹ , so that the impedance Z * is given by the following expression:

Z = [(JWL ') / G'] ^1/2 (38)

Thus, as is known in the art, the real and imaginary parts of Z * are the same. So they are the high-frequency resistance or the internal reactance CJ L ^. Since the reactance (AL ^ changes directly with the square root of the frequency, the inductance L ^ inve rs changes with the square root of the frequency.

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ORIGINAL INSPECTED. * '

U90479

After the current distribution of a multicore conductor is uniform at all frequencies, and after none Skin effect works, the internal inductance is always the same as the low frequency value. This is of particular importance for the transmission properties for television signals and the like, as this helps to reduce the group delay difference and the attenuation.

The internal inductance L ^ of a multi-core conductor without Soul is 1/2 cgs units per cm; however, it is considerably lower for a leader with a soul, such as will be shown below.

The energy stored in a magnetic field is H / 8Y "erg / cm- *. The value of H is in the equations (12) and (13). This gives the total energy E in the field within that taken up by the conductor Space for a direct current I as follows

E - (1/8 · Τ) (8 I ² F / d ₂ ² ) (1 / 4TMd ₂ ² - A, ² ) erg / om length,

where I is given in cgs units. However, this energy is equal to 1/2 L ₄ I ² .

Consequently applies »

L ₁ «1/2 F (1 .- y ² ) ogs / cm (39)

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The value I ^ thus varies between 1/2 cgs units / cm and a slightly lower value depending on the diameter ratio y of the conductor.

Calculation of the optimal diameter ratio of inner conductor and return conductor

If the inner conductor of a coaxial cable is a multi-core conductor according to the invention, but the outer - or return conductor - is of a conventional type, then it differs the optimal ratio between inner and outer diameter is somewhat different from that of conventional cables; it is this in fact a further subordinate feature of the invention. This is for the sake of simplicity with respect to a Head depicted without a soul.

Equation (27b) gives: R _f = 1715 f dj / dg = p / d ₂ (e.g.) (27k)

For a return pipe of conventional design, the resistance R _{r is given} by the following equation:

R _r = 6080 f ^V VD = q / D (e.g.) (40)

, 1/2 where D is the inner diameter of the tube.

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The damping is then approximately proportional to:

(p / d ₂ + q / D) / [log _e (D / d ₂ )] (41)

By differentiating with respect to dp one obtains a minimum if: log _e (D / d ₂ ) = 1 + ((i / p) (d ₂ / D) (42)

This gives the correct proportions for a damping minimum for a given overall diameter, but not for given costs. The latter is quite difficult and requires a thorough knowledge of the various costs the materials and procedures; however, the above paper gives at least a rough idea. For a typical design, the diameter ratio is approximately 4.2; the ratio is slightly larger for minimal cost. This represents a further subordinate feature of the invention.

Change in group delay

It is now proposed to discuss the change in the group delay. When discussing the equation (6) it was shown that the phase velocity V is given approximately by:

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It has already been mentioned that L changes with frequency in solid cables. L can be viewed as if it were made up of a fixed part L and a variable part

Part Lj ^ would exist, the value of which is determined by the skin effect . As shown in (38), the high frequency resistance of the inner conductor is equal to its internal reactance; a similar consideration also applies to the return conductor.

Thus: 63L _± = R = 2 0C ₀ Z (W) (43)

Where ^. the part of the attenuation contributed by the conductor under consideration , see equation (7a)

Hence applies

LC = c [l _o + (2tf _c V {cVC)] (44)

If one sets (1 / V) = L _Q C, where V _{Q is} the speed at an infinite frequency , one obtains!

LC = (W ₀ ² ) f 1 + (2 * _C V _O ² ) / («V) J or in a first approximation:

(1 / V ² ) = LC = (1 / V _O ² ) [i + (ZO ^ V / m)] (45)

Differentiating to 0), one obtains: - (1 / V ³ ) (dV / du>) = (VV ^ d / wXdtf ^ / dCa) - ς / θ ² 7 (46)

_C V _O J

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Now β = co / V is set so that the group delay is results in:

OO - '(1A) -

(1A _O ) (1 - 2 0C ₀ V ₀ Za ₄ ) ^ ² + (V / V _o )

If one applies the binomial theorem to the first term in equation (47), and one sets in the second term V = V. the following result is obtained:

d ^ / dfc m 1 / V _O + d ^^ dco (48)

1/2 Since ν xs κ ca ', where K is a constant , the following applies:

⁼ V2 K / oO ^1/2 = ^1/2 ας / £? (49)

This last equation thus gives the difference in the group delay compared with that for infinitely high frequency. The difference is inversely proportional to J ¹ '*.

In the case of a multi-core cable according to the invention, the inner conductor does not change the. Group delay, but the outer conductor does its smaller part of the change. For invoices with typical Cables has been shown for cables with the same total diameter that with the help of the invention, the change in

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H90479

Group delay is reduced by a factor of about 5.5. However, if you want to achieve with the invention, a reduction in the diameter of the cable, in order to obtain the same attenuation, improving with respect to reducing the group delay changes in 5 _f 5 to 3, but this is still a significant improvement.

Patent claims:

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Claims (1)

H90479 - 67 patent claims: 1. Conductor for high-frequency currents, the outer surface of which coincides at least partially with an imaginary circumscribing cylindrical surface running coaxially to the conductor and which consists of several parallel-connected, separately insulated metal cores with an insignificant skin effect, the metal cores being systematically twisted or superimposed, characterized that the number of wires provided within the circumscribing surface is significantly less than the maximum possible due to the geometry, the wires being arranged so that the conductor resistance at or near the highest operating frequency is between two and 1.63 times the base resistance R ₀₀ is located. 2. The ladder of claim 1, wherein substantially all of Space within the cylindrical surface of a strand of wire such as stranded wire Or the like. Is taken, characterized in that the reduction in the number of wires below the number possible due to the geometry is achieved in that the space factor over the normally usual addition is increased so that the number 9 0 98 03 / Ö 9 5 7 U90479. - - 60 - i Cores per unit area is reduced, and that the High-frequency resistance at or near the highest operating frequency is approximately twice the "base resistance", which in this case is equal to the direct current resistance of the electrical conductor with the specified number of wires. 3. Head according to claim 1, in which only ü ** »T * ¹ -! * · ^{Β ν} · ^Γ ~ joinable space within the circumscribing zy-lindri- , see surface is occupied by veins, which are arranged in the form of a densely packed hollow cylinder, the radial thickness of which is large compared to the one- Penetration depth of the high-frequency currents into the metal from which the wires are made, characterized in that the ratio of the diameter of the hollow cylinder. is chosen so that the high frequency resistance is between two and 1.63 times the "base resistance", the first number for a greater radial thickness and the last number for a smaller radial thickness applies. 4. A ladder according to claim 3, characterized in that the diameter ratio y _Q de · hollow cylinder according to equation (36) or Figure 6 of the Constant kg is determined, and that the ratio of the 1/2 High frequency resistance to the "base resistance" 2F ' ORIGINAL INSPECTED 909803/0957 H9Q479 is, where F using equation (13) or Figure 4 of y _{Q and} 'the "base resistance" is determined from equation (27d). 5. Head naoh one of the preceding claims, characterized in that the high frequency A resistance at the highest operating frequency by one 'Factor of 0.5 or less is less than that of a' solid conductor with the same external diameter. . 6. conductor NaOH Anspruoh 5, characterized gekennzeioh- \ net, DAFL the ratio of its high frequency resistance to that of a solid conductor with the same Auflendurohmeeser is given by the equation (30a) in the case of wire conductors, or by the equation (37) In the case of tape wires. 7. Head naoh Anspruoh 3 or 4, characterized in that the hollow cylinder space of one Layer of strands of fine wires in the form of stranded wire or the like is taken. 8. Head naoh Anspruoh 3 or 4, characterized in that the hollow cylinder space of several traditional metal strips or lamellas 80 9 8 α ^3/0 9 S 7 ° RIOIN * ^L '* sp _ecTeo the width of which is substantially in a circumferential direction and the thickness of which is substantially in a circumferential direction radial direction are arranged so that they are aligned with their edges to the magnetic field generated by a current flowing in the conductor would. 9. A ladder according to claim 8, characterized in that the strips or lamellas are arranged in units each consisting of two stacks, which each correspond to the shape of the hollow cylinder space, with each β band or each lamella in sequence at intervals along the conductor from the top of a first stack to the top of a second stack and from the bottom of the second stack to the bottom of the first stack so that each Tape or each lamella in turn occupies each radial position along the conductor. 10. A ladder according to claim S _9, characterized in that only two stacks are provided, each of which thus occupies one half of the beginning of the conductor. 11. Head according to claim 8, characterized in that the bands or metal lamellae are helical or braided on a thin cylindrical 909803/0957 or elliptical insulating support with a large diameter, which is then flattened and several times with a long blow around a central support or core is wound, so that a hollow cylinder is formed. 12. Head according to claim 11, characterized in that the cylindrical or elliptical The carrier consists of a thermoplastic material and during or after the flattening is subjected to a hot rolling process, whereby excess carrier material is removed and the remainder flows into the interstices of the strips or lamellas, so that these are connected to one another. 13. A ladder according to claim 11 or 12, characterized in that the flattened tube is folded like a harmonica before it is wrapped around the central support part. H. A ladder according to one of claims 11, 12 or 13, characterized in that each of the metal lamellas is in the form of a spiral by means of one of the known Process for the production of metal foils is produced by deposition. 909803/0957 H90479 15 · Ladder according to one of claims 11, 12, 13 or 14, characterized in that the metal strips or metal slats in the longitudinal direction be applied to a thermoplastic adhesive tape, which helically overlaps around a temporary mandrel is wound so that a tubular insulating support is formed, which of is withdrawn from the mandrel while it is being formed. 16. A ladder according to any one of the preceding claims, in addition to claim 2, characterized in that that the cavity is occupied by a core or a core, which or which comprises a clamping part. 17. A ladder according to claim 16, characterized in that the clamping part consists of a metal »eil bed ent, which is provided with a plastic cover. .Ladder according to claim 16, characterized in that the tensioning part consists of a non-conductor, which has a relatively high modulus of elasticity and a high tensile strength. 19. Head according to one of the preceding claims, characterized marked that the conductive veins 909803/0957 ■ H90479 - 73 - with a reinforcement made of a non-conductive material are provided, which increases the strength of the veins that are mechanically connected to the reinforcement. 20. Head according to one of the preceding claims, characterized in that the non-conductive reinforcing tape he or LUden stranded with the conductive wires are. 21. A ladder according to one of the preceding claims, characterized in that the non-conductive thread as snaffles are inserted into the spaces between the veins. 22. Head to one of the Aneprüohe 11 to 15, thereby marked, high tensile strength threads, for example glass fibers, in the cement of the cylindrical or elliptical carrier old large Durohmesser . be introduced while this is being formed, and that these fibers then by flattening the carrier and subsequent hot rolling with the metal strips or Slats are connected. 23. Electric cable * ae with a conductor after a djr preceding claims, characterized by an outer non-metallic envelope, which as Clamping part is used. 909803/0957 24. Cable or conductor according to one of the preceding claims, characterized by at least one tensioning or reinforcing part, which is made of polyethylene terephthalate exists, which has previously been subjected to a cold drawing process. 25. Cable or conductor according to one of claims 1 to 23, characterized by at least one Tensioning or reinforcing part, which consists of a strand of glass fibers. 26. Cable for the transmission of electrical high-frequency ■ signals, characterized by at least a conductor according to one of the preceding claims. 27. Cable according to claim 26, characterized in that the variation of the group delay occurs the transmitted frequency band is lower than Alt in a cable with similar attenuation, welohes aneteil β des claimed conductor has a solid tubular conductor with a larger diameter. 28. Cable according to claim 23, characterized in that the outer polyethylene terephthalate Umhüllunf is in the form of a seamless tube with a thick Enclosure with a durometer larger than the outer one 909803/0957 H90479 Diameter of the uncovered cable, first with the help is extruded in a die and the uncovered cable is passed through the center of the die, and wherein the envelope is then expanded radially only by a mechanical device or by air pressure is, while the cable is being pulled through, at such a rate that the expanded Wrap is stretched by about $ 500 so that it shrinks in diameter and is therefore firmly attached to the Cable sits in such a way that it has a high modulus of elasticity. 29. A coaxial cable, wherein the inner conductor comprises a conductor according to any one of claims 1 to 25, characterized characterized in that the outer conductor is made from metal strips that are much thicker are considered to be the penetration depth of the high-frequency currents the highest operating frequency, and that the outer conductor is made of a metal with high electrical conductivity and great tensile strength and forms a tensioning part. 30. Coaxial cable according to claim 29, characterized in that the outer conductor consists of a high tensile strength metal, which with a metal of higher conductivity is plated. 909803/0957 31. Device for folding the bands during manufacture a conductor according to one of the preceding claims in addition to claims 2 or 7, characterized by a litz wire machine with reverse rotation, means being provided through which the tapes after they have been placed in a circle suitable matrices are passed so that the circular shape gradually changes to an elliptical shape and eventually becomes flattened. 32. Apparatus according to claim 31, characterized duroh means to wrap the applied tape around a central supporting core, so that the conductor is formed is, wherein the core is passed axially through the device. 33. Apparatus according to claim 32, characterized by means for rotating the axis of the band-forming ends Matrices and the transverse axes of the tape-carrying reels, so that the finished tapes are twisted can if they are applied to the soul in one operation. 34. Submarine cable with a ladder according to one of the claims * 1 to 25, characterized in that the 9098 03/09 5 7 ^^ _{| NSPeC} TEO Gaps between the fields with a connection are filled, do to prevent breakage of the veins by hydrostatic bridge. ORIGINAL INSPECTED