CS275808B6 - Coaxial cable for fast computer networks - Google Patents

Abstract

The subject matter of the invention is a radio-frequency coaxial cable for transmitting digital signals, e.g. in fast computer networks. On its foamed insulation (2) centrally surrounding the inner conductor (1), the coaxial cable has at least one groove (21), running in the form of a helical line, whose minimum depth is 10% of the diameter of the insulation (2) and whose pitch should amount to at least three times the width of the groove (21). <IMAGE>

Description

The invention relates to an improvement in the construction of a high-frequency coaxial cable suitable for the transmission of high-speed digital signals. The purpose of the solution is to achieve a high and at the same time guaranteed speed of electromagnetic pulse propagation in the cable, which will significantly reduce the possibility of error messages when evaluating control pulses in the computer network.

Various types of core insulation are used in existing RF coaxial cable designs. The technologically simplest construction of a coaxial cable that spins the requirements for higher transmission speed is a construction with foam insulation. Most commonly, chemically foamed polyethylene insulation is used, allowing the electromagnetic pulse propagation to be accelerated from 66 up to 81% compared to the vacuum propagation rate. However, for use in even faster local computer networks, an acceleration of up to 87% is required, which is no longer achievable by this design. Newer types of high-frequency coaxial cables are already manufactured with foam insulation with injection foam, which allows to achieve a propagation speed of up to 90%, but is inhomogeneous and technologically more demanding. The most widespread are coaxial cables with insulation consisting of a combination of wrapped thicker polyethylene tape, so-called. a cord around the inner core and the sealed tube which provides the insulation with the desired cylindrical shape required for the application of conventional outer cores, most often formed by a braid or a combination of foil and braid. The advantage of such solutions is the possibility to achieve a spreading rate of up to 90%, but their disadvantage is that the size of the spreading rate is given by the pitch of the cord wrap and the thickness of the tube. definitely determined and cannot be changed. The cable thus produced has a relatively large dispersion of this most important parameter. Another disadvantage of this type of cable is its increased rigidity. The pipe must be made of hard material, so that the round cross section of the cable does not change to oval. The cord keeps the center of the inner core permanently centered, but it does not prevent flattening of the tube. The more widely known air constructions for coaxial cable and disk and balloon insulations allow to achieve a propagation speed of up to 90%, but they cannot be braided or wrapped with foils. Tubular Balloon and so-called. bamboo insulation, on the other hand, is not feasible up to diameters above 3.7 mm insulation from the dimensional range of cables, which is required due to the connector technology used.

The above-mentioned disadvantages of existing high-frequency coaxial cable designs are overcome by the cable solution according to the invention, which consists in that the centrically molded foam insulation of the coaxial cable is provided with one or more helical selections of different shape over the entire surface. The depth of the recesses shall be at least 10% of the diameter per d of insulation and the pitch shall be at least three times the width of the recesses.

The advantages of the proposed solution are manifested in particular in the fact that the cable insulation achieves a larger, but above all precisely adjustable amount of air, and with its increasing part in the insulation thus produced the speed of propagation of the electromagnetic pulse in the coaxial cable increases. This speed can be adjusted very sensitively by the depth and number of recesses, their shape and pitch. With a variable air / foam insulation ratio, the unit can be set to a thousandth of a percent by varying the air / foam insulation ratio after an in-process inspection to determine the exact size of the propagation rate while pressing the foam insulation exactly according to customer requirements. A significant advantage of the solution is also a flicker increase in the flexibility of the coaxial cable.

As a result of the helical recesses in the insulation, its surface stiffness is disrupted and the overall stiffness of the coaxial cable is reduced by a slight relative displacement on both the inner and outer side of the bent insulation in the air recesses, and the slight inhomogeneities negligible.

The principle of the solution is illustrated in the attached drawing, where in FIG. 1 is a schematic sectional view of a coaxial cable with modified insulation. On the inside

i.

The core 11 is a foam insulation 8, with a spiral recess 21. Above the insulation is an outer core 6 and a sheath 4.

The solution is further illustrated by examples of particular embodiments of the high-frequency coaxial cables of the invention.

Example 1

A coaxial cable with an inner core 1 of copper wire 0.55 mm in diameter, chemically foamed with 3.7 mm diameter insulation pressed centrally to form a regular circle and provided with a spiral recess 21 of a semicircular section with a 13 mm pitch. The recess depth is 1.10 mm. For insulation 6, the outer core 3 is formed of yard plated metal foils facing each other and tinned copper tines placed therebetween. A plasticized PVC sheath 4 is circumferentially molded on the outer core thus formed.

Example 2

Coaxial cable with inner core JL of copper-plated steel wire 0.643 mm diameter, chemically foamed insulation 3.75 mm diameter, center-pressed and provided with court surface spiral recesses 21, with the same orientation and inclination 23 mm, located on opposite sides of the insulation surface have a semicircle cross-sectional shape of 1.5 mm in diameter. In the insulation 2 thus treated, the outer core 6 is formed of a dense braid of tinned copper wires and a circumferentially molded PVC sheath 4 for a total cable diameter of 6.15 mm.

Example 3

Coaxial cable with an inner core JL of 0.45 mm copper wire, chemically foamed with centric centrally pressed insulation 2.95 mm diameter, provided with yard surface recesses 21 of rectangular cross-section with a recess depth of 1.1 mm and a width of 0.6 mm extending along cable axis in a 9 mm spiral. Their positioning remains on opposite sides of the insulation surface 6 and the spiral recesses 21 have the same orientation. Above the treated insulation is an outer core 3 formed longitudinally overlaid with a metallized plastic foil and a thin braid of tinned copper wire, followed by a circumferentially molded sheath 4 of stabilized polyurethane.

Coaxial cables with modified insulation will find application especially in local computer networks with high speed of electromagnetic pulse propagation. Their high and at the same time exact value of the wave shortening factor ensures reliability of even the most demanding transmissions.

Claims (3)

PATENT CLAIMS Coaxial cable for fast computer networks with an inner core, foam insulation, over which there is an outer core and a sheath, characterized in that the inner core (1) has a centrally pressed foam insulation (2) · has at least one longitudinally spiral-shaped over its entire surface a recess (21) having a minimum depth of 10% of the diameter above the insulation and a pitch of at least three times the width of the recess (21).