EP0688061A1 - Radiating high frequency coaxial cable - Google Patents

Abstract

The cable includes an inner conductor (1) with an isolating, helically wound circular section (2) around it. The helical section holds an inner dielectric sleeve (3) in place. A number of isolated longitudinal wires (4A,4B) are placed along the sleeve with circular isolating separators (5). An outer sleeve (6) is extruded onto the outer longitudinal wires. Insulating tape (7) is helically wound along the length of the isolated longitudinal wires and the isolating separators.

Description

The present invention relates to a high frequency radiating coaxial cable, comprising an internal conductor, an internal dielectric sheath surrounding the internal conductor, an external conductor itself comprising a plurality of external conductive elements spaced from one another and arranged in a layer. coaxial around the internal sheath, and an insulating external sheath.

A radiating cable of this type is described in document GB-A-2 094 065. The external conductive elements are retained spaced from each other by the external sheath. To this end, it is provided with recesses for receiving and positioning the external conductive elements. As a variant, the internal sheath has recesses for at least partially receiving these external conductive elements, which are then retained in position by the external sheath.

The realization of such a cable is long and not easy. Indeed, it is necessary for each cable to provide recesses in the outer sheath and / or the inner sheath and to place therein the various external conductive elements. From one cable to another, the number and the section of the recesses must be adapted to the number and the section of the external conductive elements adopted.

For ease of making a cable of this type, it is possible, as a variant with respect to this document, to extrude the external sheath on the external conductive elements previously arranged and suitably spaced from one another on the periphery of the internal sheath. These elements are then embedded in the extruded outer sheath which holds them.

Such a variant of realization is also not entirely satisfactory. Indeed the external conductive elements can move relative to one another during the extrusion of the external sheath and then no longer have the spacing that they had between them before the extrusion of this outer sheath. The characteristics of the radiating cable is thereby modified.

The present invention aims to avoid these problems, by facilitating the production of this type of radiating cable and improving its transmission characteristics, in particular the power radiated along the cable.

It relates to a high frequency radiating coaxial cable, comprising an internal conductor, an internal dielectric sheath surrounding the internal conductor, an external conductor itself comprising a plurality of external conductive elements spaced from each other and arranged in a coaxial layer around the internal sheath, and an external insulating sheath, characterized in that it further comprises a plurality of insulating elements alternating and contiguous with said external conductive elements, by separating them from each other in said layer made continuous on the periphery of said internal sheath and thus covered by said external sheath.

• lesdits éléments conducteurs extérieurs et lesdits éléments isolants sont sensiblement de même diamètre,
• lesdits éléments conducteurs extérieurs comportent une âme conductrice revêtue d'une isolation individuelle;
• ladite gaine externe est une gaine de serrage uniforme des éléments conducteurs extérieurs et des éléments isolants les uns contre les autres et sur la périphérie de ladite gaine interne, en particulier une gaine extrudée en pression;
• le câble comporte en outre un jonc diélectrique, enroulé hélicoïdalement à pas dit long sur ledit conducteur intérieur et recouvert par ladite gaine interne rendue d'épaisseur réduite pour un diamètre extérieur voulu.

This cable advantageously also has at least one of the following additional characteristics:

• said external conductive elements and said insulating elements are of substantially the same diameter,
• said external conductive elements comprise a conductive core coated with individual insulation;
• said outer sheath is a uniform clamping sheath of the outer conductive elements and of the insulating elements against each other and on the periphery of said inner sheath, in particular a sheath extruded under pressure;
• the cable further comprises a dielectric rod, helically wound in a so-called long pitch on said internal conductor and covered by said internal sheath made of reduced thickness for a desired external diameter.

The characteristics and advantages of the present invention will emerge from the description given below of a preferred embodiment, given by way of nonlimiting example and illustrated in the single figure of the attached drawing.

This single figure shows in cross section a high frequency radiating coaxial cable according to the present invention.

• un conducteur intérieur 1,
• un jonc isolant 2 enroulé hélicoïdalement sur la périphérie du conducteur intérieur,
• une gaine cylindrique interne 3, en matériau diélectrique, extrudée sur le jonc 2,
• une pluralité d'éléments ou fils conducteurs extérieurs 4 et d'éléments ou fils isolants 5, alternés les uns avec les autres et assemblés jointivement en une couche cylindrique coaxiale avec le conducteur intérieur sur la gaine interne, et
• une gaine extérieure isolante 6, extrudée sur la couche de fils 4 et 5.

This cable includes:

• an inner conductor 1,
• an insulating rod 2 wound helically on the periphery of the inner conductor,
• an internal cylindrical sheath 3, made of dielectric material, extruded on the rod 2,
• a plurality of external conductive elements or wires 4 and insulating elements or wires 5, alternated with one another and joined together in a cylindrical layer coaxial with the internal conductor on the internal sheath, and
• an insulating outer sheath 6, extruded on the layer of wires 4 and 5.

The outer conductor wires, spaced from each other by the insulating wires, define the outer conductor of the cable and allow the radiation to the exterior of the high frequency signals transmitted by the inner conductor.

The rod 2, the internal sheath 3 and the insulating wires 5 are in particular made of polyethylene. The rod 2 makes it possible to obtain an air dielectric, of the same thickness as it, around the internal conductor and the spacing of the internal sheath of the internal conductor, for a reduction in thickness and a desired external diameter of this internal sheath .

The outer sheath protects the cable and is in particular made of polyvinyl chloride. It is colored in the mass to make the covered elements invisible from the outside. It is preferably extruded under pressure for uniform tightening, without deformation, of the wires 4 and 5 between them and on the internal sheath. It simultaneously ensures a possible resumption of assembly of the wires 4 and 5 on the internal sheath.

An insulating tape 7, of reduced thickness, in particular made of polyester, is preferably but not necessarily wound helically with a so-called long pitch on the layer of wires 4 and 5, for their perfect retention during the extrusion of the external sheath .

The wires 4 and 5 are preferably themselves assembled on the internal sheath with a very long winding pitch, markedly greater than that of the ribbon. The winding of the ribbon 7 and that of the wires 4 and 5 are in opposite directions.

These wires 4 and 5 are each of substantially identical diameter.

The wires 4 and 5 cover the entire periphery of the internal sheath 2. The insulating wires 5 in the gap between the conductive wires ensure the removal with regular spacing of the conductive wires and their subsequent equidistant maintenance. The number of wires 4 and 5 and their section are calculated for the continuity of this overlap and for an outside diameter of the resulting coaxial layer.

The outer conductive wires 4 are advantageously individually insulated and as identical as possible from each other. Each is formed by a solid conductive core 4A or in a multi-strand variant, in particular in copper or in a variant in another conductive metal or alloy, and a peripheral insulation 4B on the core, in particular in preferably non-colored polyethylene.

The insulating wires 5 are also as identical as possible to each other. They are solid and in particular made of preferably colored polyethylene and having a color analogous to that of the outer sheath, or as a variant comprise a central synthetic or textile filament, single-strand or multi-strand, which is coated with insulating plastic.

This coaxial cable is of comparable operation and improved performance compared to those of an outer conductor cable provided with a set of continuous and parallel slots along its length, or of an outer conductor cable formed by a plurality of conductive elements or wires spaced from each other to define the radiating slots therebetween.

It is faster and easier to produce. The constancy of the spacing between its practically identical external conducting wires, which is obtained by the insulating and practically identical insulating wires, leads to obtaining radiating slots having strictly the same width. Compared to known radiating cables of the same section and having the same number of continuous radiating slots, and in particular compared to the cable with multiple and spaced external conductors without insulating insulating wires, it allows a gain in radiated power which can reach of the order by 30%, at frequencies of notably 170 MHz and 450 MHz.

The width of the radiating slots defined by the insulating wires and the possible insulation of the conducting wires is easy to adjust from one cable to another, depending on the frequency of the signals to be transmitted. It is in particular obtained at the desired value by the choice of the section of the conductive cores 4A and / or the thickness of the individual peripheral insulation 4B of the conductive wires.

Claims (10)

1 - High frequency radiating coaxial cable, comprising an internal conductor, an internal dielectric sheath surrounding the internal conductor, an external conductor itself comprising a plurality of external conductive elements spaced from one another and arranged in a coaxial layer around the internal sheath, and an external insulating sheath, characterized in that it further comprises a plurality of insulating elements (5) alternating and contiguous with said external conductive elements (4), separating them from each other in said layer thus made continuous on the periphery of said internal sheath (3) and covered by said external sheath (6). 2 - Coaxial cable according to claim 1, characterized in that said external conductive elements (4) and said insulating elements (5) are substantially of the same diameter. 3 - Coaxial cable according to one of claims 1 and 2, characterized in that said external conductive elements (4) comprise a conductive core (4A) coated with individual insulation (4B). 4 - Cable according to claim 3, characterized in that said conductive elements (4) comprise a solid conductive wire. 5 - Cable according to one of claims 1 to 4, characterized in that it further comprises an insulating tape (7), of reduced thickness, helically wound in said long pitch on the layer of external conductive elements (4 ) and insulating elements (5), alternating and contiguous with each other. 6) coaxial cable according to one of claims 1 to 5, characterized in that said external sheath (6) is a sheath for uniformly clamping the external conductive elements (4) and the insulating elements (5) against one another and on the periphery of said internal sheath (3). 7) Coaxial cable according to claim 6, characterized in that said outer sheath (6) is a sheath extruded under pressure. 8) Cable according to one of claims 1 to 7, characterized in that said outer sheath (6) is non-transparent, and is in particular colored for this purpose. 9) Cable according to one of claims 1 to 8, characterized in that it further comprises a dielectric rod (2), wound helically with said long pitch on said inner conductor (1) and covered by said internal sheath (3 ) made of reduced thickness for a desired external diameter. 10) Cable according to one of claims 1 to 10, characterized in that said external conductive elements (4) and said insulating elements (5) are assembled at a relatively small angle with the axial direction of said cable.

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