JPS6145512A - Flexible coaxial cable and method of producing same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to coaxial cables, and in particular, but not exclusively, to radio frequency flexible coaxial cables.

The amount of attenuation dc due to the conductors (center and outer coaxial) of a flexible coaxial cable is given by the following equation, assuming that both ends are made of the same material and the outside is braided.

Here, ε: Permittivity of dielectric ρ: Resistivity of modal body [: Frequency d: Outer diameter D of center conductor = Outer diameter of dielectric KS: Coefficient determined by physical shape of center conductor (strand coefficient) Kb Niblade coefficient, KIl is the twisting coefficient +
<If r is the filling rate, it is equal to (KIl/Kf').

In the case of a single-wire body center conductor, Ks = 1, and in the case of a 7-strand stranded center conductor in which six circular cross-section wires are twisted around a conventional circular cross-section center line, Ks = 1.25.

However, the effective electrical outer diameter of a 7-strand flexible conductor is actually 1
This is 0.939 times the actual physical outer diameter. Therefore, the coefficient KS/d for a single-core conductor is 1/(1, but 78
Relationship to conductor v1. KS/d is 1,25/ (0,9
396), which is approximately equal to 1.33/d.

Therefore, when using the conventional 7-core strand, the amount of attenuation across the conductor is approximately 33% higher than when using a single-core conductor.

Almost all conventional radio frequency flexible cables, including television downleads, require single-core circular center conductors or longer flex life and more reliable terminations than can be obtained with single-core conductors. In this case, a conventional 7-strand stranded conductor was used.

While the flexible conductor provided by conventional seven-strand stranded conductors is desirable, the resulting increased center conductor attenuation is undesirable.

One object of the present invention is to provide a flexible coaxial cable that includes a flexible and dense center conductor with minimal attenuation.

Another object of the present invention is to form a flexible central conductor by twisting a plurality of conductive elements into a twisted member, and compressing the twisted member so that all the voids are filled with the conductive element material. The present invention provides a method for manufacturing a flexible coaxial cable comprising the steps of: forming a substantially filled and compressed stranded member having a substantially circular cross section.

While the increased flexibility afforded by conventional seven-strand stranded conductors, as discussed above, is desirable, the resulting increase in center conductor attenuation is undesirable.

However, the center conductor, which has the flexibility of a conventional 7-core stranded conductor and the attenuation of a single-core conductor, has a substantially circular shape in which each strand of the conventional 7-stranded stranded conductor is in close contact with each other and almost fills the void. It can be obtained by crimping (compressing) so that it has a cross section of . FIG. 1 shows a cross section of a conventional 7-fiber stranded conductor 1, which is the same as the cross-section of a 7-fiber stranded body 2 according to the present invention before being compressed to have the TI-section shown in FIG. be. So pressure is 1? The i-conductor is dimensionally and electrically equivalent to a single-core conductor with a coefficient of 1.25/(0,939d
) becomes 1/d. Therefore, it has the same dimensional accuracy as a single-core conductor, exhibits minimum attenuation without losing flexibility, and has a center conductor of 1q.

To perform compression, a 7-strand twisted fi1 body, each strand 3 of which has a substantially circular cross section before compression, is inserted into a conventional uncompressed conductor 1.
may be drawn through a suitable mold smaller than that used to make the mold. Conductors consisting of less than seven strands, for example three or four strands, are similarly compressed. This may be advantageous because larger elementary strands (wires) can be used. As the number of strands increases, the cost of the basic wire drawing process and pretreatment for twisting/compression increases. Although configurations with seven or more strands are conceivable, the electrical advantage of using seven or more strands is minimal.

The strands 3 are preferably made of copper, but may also be made of aluminum,
It may be a copper-coated steel wire or a copper-coated aluminum wire. In the compressed center conductor 2, the insulating material 4 is made of air insulation, raw air insulation, solid or porous material, the outer conductor 5 is made of a material such as copper wire which does not necessarily have to be braided, and the outer sheath 6 is made of extruded material. Any coaxial cable (FIG. 3) made of plastic material, such as molded plastic, may be used.

The compressed center conductor 2 consists of no more than seven compressed strands and has the same flexibility and fatigue resistance as a conventional 7-strand conductor, but with the electrical characteristics at low and high frequencies of a single core. A viewable radio frequency coaxial cable is obtained having a center conductor that is identical to a circular conductor. Although the present invention is not limited to the above, the diameter is typically 0.2 mm (0.00 mm).
The present invention relates to the production of very small conductors for coaxial cable center conductors of the order of 8 inches.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional 7-strand twisted center conductor;
The figure is a cross-sectional view of a seven-strand twisted center conductor according to an embodiment of the present invention, and FIG. 3 is a cross-sectional view of a coaxial cable including the center conductor shown in FIG. 2, shown on a different scale. 1... 7-core twisted conductor (conventional), 2... 7-core twisted conductor (invention), 3... Twisted wire, 4... Insulating material, 5... 9 outside 8I tatami mats , 6... Outer covering.

Claims (8)

[Claims] (1) A flexible coaxial cable with minimal attenuation, flexibility, and a dense central conductor. (2) The coaxial cable according to claim 1, wherein the center conductor consists of six conductor elements arranged around a center conductor element. (3) The step of twisting a plurality of conductor elements together to form a twisted member to form a flexible central conductor, and compressing the twisted members so that all the voids are substantially filled with the conductor element material, resulting in a compressed twisted member. A method for manufacturing a flexible coaxial cable, comprising the steps of: forming a substantially circular cross section. (4) The manufacturing method according to claim 3, wherein six conductive elements are twisted together around a central conductive element, and all of the conductive elements have a substantially circular cross section before the compression stage. (5) The manufacturing method according to claim 3, wherein the twisted member is compressed by being passed through a mold. (6) The manufacturing method according to claim 3, wherein the amount of attenuation of the center conductor is extremely small. (7) providing a dielectric on the compressed stranded wire member; and forming a cylindrical outer conductor coaxial with the compressed stranded wire member on the dielectric. The manufacturing method described in Section 3. (8) The manufacturing method according to claim 3, further comprising the step of extruding an outer covering layer onto the outer conductor.