JP2003092031A - Coaxial cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coaxial cable and a multi-core coaxial cable that are improved in shielding effect and crosstalk characteristics. SOLUTION: This is a coaxial cable in which a dielectric layer 2 is provided on the outer circumference of a center conductor 1 and a laterally-wound shield layer 3 made by winding spirally a plurality of conductive element wires is provided on the outer circumference of this dielectric layer, and further, a protection covering layer 4 is provided on the outer circumference of this laterally-wound shield layer. The winding angle θ with which the element wires of the above laterally-wound shield layer is wound on the dielectric layer is in the range, 8 degrees <=θ<=19 degrees, and a multi-core coaxial cable comprising a plurality of this coaxial cables is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coaxial cable provided with a horizontal winding shield layer as an outer conductor layer, and particularly to a coaxial cable and a multi-core cable having improved electrical characteristics such as a shield effect and crosstalk characteristics in a high frequency band. It concerns a coaxial cable.

[0002]

2. Description of the Related Art Conventionally, coaxial cables have been widely used as internal wiring and external wiring of various information devices such as computers and communication devices or probe cables of medical devices such as ultrasonic diagnostic equipment. Such a coaxial cable is provided with an outer conductor layer for shielding noise generated from inside and outside the coaxial cable and for preventing crosstalk between adjacent coaxial cables, and prevents malfunction of information equipment or medical equipment. We are aiming for higher performance.

Recently, with the further improvement in performance of these devices, the signal frequency for transmitting a coaxial cable is, for example, 1 MH.
It can reach high frequencies from z to several GHz. When such high frequency signal transmission is performed, it is necessary to provide an outer conductor layer having a high shielding effect in order to effectively improve the shielding effect for shielding noise and prevent crosstalk. There is a case where a braided shield layer is provided on the coaxial cable as an outer conductor layer having a high shielding effect according to such a need. However, the coaxial cable provided with the braided shield layer does not have sufficient flexibility. When a plurality of coaxial cables are bundled or twisted together like a cable, there is a problem that handling is difficult.

On the other hand, in order to have flexibility and good handleability, a plurality of conductive wires are used as an outer conductor layer around the outer periphery of the dielectric layer of the coaxial cable at a predetermined winding angle. In the case of providing a horizontally wound shield layer formed by spirally winding (generally, about 20 degrees with respect to the axis of the central conductor from the viewpoint of productivity), such horizontally wound shield layer is provided. Compared with a coaxial cable provided with a braided shield layer, the coaxial cable has characteristics that it is rich in flexibility, it is easy to thin the coaxial cable, and it is excellent in terms of easiness of terminal processing and weight reduction. ing.

However, in the case where the horizontal shield layer is provided on the coaxial cable, while having the above-mentioned characteristics, when the signal frequency to be transmitted reaches the high frequency of, for example, 1 MHz to several GHz as described above. The above-mentioned coaxial cable having the horizontally wound shield layer has a problem that it is not sufficient from the viewpoint of improving the shield effect and preventing crosstalk.

[0006]

Therefore, the present invention is
In view of the above-mentioned problems, the inventors of the present application have conducted extensive studies, and as a result, in a coaxial cable provided with a horizontal winding shield layer as an outer conductor layer, horizontal winding using a plurality of conductive strands. The present invention has been found out that by setting the winding angle of the shield within a predetermined range, the coaxial cable has good shielding characteristics and good electrical characteristics such as crosstalk.

That is, an object of the present invention is to provide a coaxial cable and a multi-core coaxial cable having improved shield effect and crosstalk characteristics.

[0008]

To achieve the above object, in a coaxial cable according to the present invention, a dielectric layer is provided on the outer periphery of a center conductor, and a plurality of conductive strands are provided on the outer periphery of the dielectric layer. Providing a horizontal winding shield layer formed by spirally winding,
Further, in the coaxial cable in which the protective coating layer is provided on the outer circumference of the horizontal shield layer, the winding angle θ at which the strand of the horizontal shield layer is wound around the dielectric layer is 8 with respect to the axis of the central conductor. The configuration is such that the range of degrees ≦ θ ≦ 19 degrees is satisfied.

As another gist, a dielectric layer is provided on the outer periphery of the center conductor, and a horizontal winding shield layer formed by spirally winding a plurality of conductive wires is provided on the outer periphery of the dielectric layer. ,
Further, in the coaxial cable in which the protective coating layer is provided on the outer circumference of the horizontal shield layer, the winding angle θ at which the strand of the horizontal shield layer is wound around the dielectric layer is 8 with respect to the axis of the central conductor. A multi-core coaxial cable including a plurality of coaxial cables having a range of degrees ≤ θ ≤ 19 degrees is configured.

[0010]

According to the present invention, as an outer conductor layer of a coaxial cable, a plurality of conductive wires are spirally wound around an axis of a central conductor at an angle θ of 8 ° ≦ θ ≦ 19 °. By using the horizontally wound shield layer formed by winding, it is possible to obtain a coaxial cable and a multi-core coaxial cable which are excellent in electrical characteristics such as a shielding effect or crosstalk characteristics.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments with reference to the accompanying drawings.

Examples 1 to 5 FEP (Tetra), which is one kind of fluororesin, is used as the dielectric layer 2 on the outer periphery of the central conductor 1 formed by twisting seven silver-plated steel covered wires having an outer diameter of 0.102 mm. A fluoroethylene-hexafluoropropylene copolymer) was extruded and coated to have an outer diameter of 0.88 mm. Next, 27 strands 3a made of a silver-plated annealed copper wire having an outer diameter of 0.1 mm are spirally wound around the outer circumference of the dielectric layer 2 at a winding angle θ of 8 degrees to form the horizontal winding shield layer 3. Formed. Further, a coaxial cable 5 (see FIG. 1) was prepared by extruding FEP as a protective coating layer 4 with a thickness of 0.1 mm on the outer periphery of the horizontal winding shield layer 3 to form the coaxial cable 5. And Furthermore, the horizontal winding shield layer 3 of the coaxial cable 5
The winding angle θ of the wire 3a is 10.8
Degree, 13.3 degrees, 17 degrees and 19 degrees, and the other examples
In the same manner as above, the coaxial cables 5 were produced, and the respective coaxial cables 5 were referred to as Examples 2 to 5. The winding angle θ described above means the winding angle of the strand 3a with respect to the axis of the central conductor 1 (see FIG. 2).

Comparative Examples 1 to 4 The winding angle θ of the coaxial cable 5 is 5 degrees,
The coaxial cables 5 were made in the same manner as in Example 1 except that the coaxial cables 5 were set to 7 degrees, 20 degrees, and 25.3 degrees, and the respective coaxial cables 5 were designated as Comparative Examples 1 to 4.

Comparative tests of the shield effect were carried out on the coaxial cables 5 of Examples 1 to 5 and Comparative Examples 1 to 4. This comparative test is based on the absorption clamp method (C
ISPR (Commit International S)
personal des Perturbations R
abioelectrics) Publicat
The size of the signal inserted into the coaxial cable 5 adjusted to have a length of 3 m according to the ion 16) is detected by using an RF (Radio Frequency) network analyzer. Table 1 shows the measurement result of the shield effect at each frequency of 50 MHz, 200 MHz and 1000 MHz and the result of the appearance evaluation of the coaxial cable 5.

[0014]

[Table 1]

Further, Examples 1 to 5 shown in Table 1
3 is a graph in which the values of the shield effect measurement results of the coaxial cables 5 in Comparative Examples 1 to 4 are plotted on the coordinates with the winding angle θ as the horizontal axis and the shield effect as the vertical axis. From FIG. 3, the winding angle θ is 8
It can be seen that the shielding effect is improved as the winding angle θ is decreased in the range of 2 degrees to 25.3 degrees.

On the other hand, if the winding angle is reduced to 7 degrees or less, the wires of the horizontal shield may overlap with each other,
A phenomenon occurs in which a gap is created between the wires, or when the coaxial cable is twisted or buckled, the wires tend to sag.Therefore, there is no improvement in the shielding effect. The appearance of the coaxial cable deteriorated due to overlapping or gaps between the wires, or slack of the wires.

Embodiments 6 to 10 Two coaxial cables 5 of the embodiment 1 are prepared, and the two coaxial cables 5 are juxtaposed to prepare a two-core coaxial cable 6 (see FIG. 4). The cable 6 is referred to as Example 6. Furthermore, each coaxial cable 5 of the second to fifth embodiments
2 pieces each, and these two coaxial cables 5 each,
The two-core coaxial cables 6 are prepared in the same manner as in the sixth embodiment, and the respective two-core coaxial cables 6 are used in the seventh to tenth embodiments.
And

Comparative Examples 5 to 8 Two coaxial cables 5 of Comparative Examples 1 to 4 are prepared, and two coaxial cables 5 are used to form a two-core coaxial cable 6 in the same manner as in Example 6. The two-core coaxial cables 6 produced were referred to as Comparative Examples 5 to 8.

In the two-core coaxial cables 6 of Examples 6 to 10 and Comparative Examples 5 to 8, the far-end cross between the two coaxial cables 5 forming each two-core coaxial cable 6 is performed. Talk and near-end crosstalk were measured.

The crosstalk is measured by a pulse pattern generator (MP1650A manufactured by Anritsu Corporation).
With the pulse signal generated by
The signal is input to one coaxial cable 5 of the two-core coaxial cable 6 adjusted to m, and the signals generated on the near end side and the far end side of the other coaxial cable 5 are used as detection signals, and the strength of this detection signal is digitally sampled. -The measurement was performed using an oscilloscope (CSA803 manufactured by Sony Tektronix Co., Ltd.).

Crosstalk (%) is the peak of the input signal--
It was calculated from the peak voltage and the peak-peak voltage of the detection signal by the following equation 1. Crosstalk (%) = 100 × (peak-peak voltage of detection signal) ÷ (peak-peak voltage of input signal) ······ Equation 1

Table 2 shows the far-end crosstalk and near-end crosstalk measurement results of the two-core coaxial cables 6 in Examples 6 to 10 and Comparative Examples 5 to 8.

[0023]

[Table 2]

Further, Examples 6 to 1 shown in Table 2
0 and the values of the crosstalk measurement results of the two-core coaxial cables 6 in Comparative Examples 5 to 8 are plotted on a coordinate system with the winding angle θ as the horizontal axis and the crosstalk (%) as the vertical axis. As shown in FIG. From FIG. 5, when the winding angle θ of the horizontal shield is in the range of 8 degrees to 25.3 degrees, the far-end crosstalk and the near-end crosstalk of the two-core coaxial cable 6 become smaller as the winding angle θ becomes smaller. It can be seen that there is a tendency.

As described above, in the coaxial cable 5, the winding angle θ with respect to the axis of the central conductor of the strand 3a of the horizontal winding shield is set in the range of 8 degrees to 19 degrees, so that the conventional winding angle (about 20 degrees). The shield characteristics are improved as compared with the coaxial cable according to (1), and in the two-core coaxial cable 6 formed by arranging two of these coaxial cables 5 side by side, crosstalk between the adjacent coaxial cables 5 also occurs. Get smaller.

The two-core coaxial cables of the sixth to tenth embodiments are those in which the coaxial cables 5 are parallel to each other, but two or more coaxial cables 5 are twisted together. However, these may be combined into a composite. Also, the winding angle θ is 8
If the angle is ≤ θ ≤ 19 degrees, it may be a multi-core coaxial cable including coaxial cables having horizontal winding shield layers with the same winding angle, or coaxial with horizontal winding shield layers having different winding angles. Even in the case of a multi-core coaxial cable having cables, the effect of reducing crosstalk according to the present invention can be obtained, and, of course, its modification and change are possible.

[0027]

As described above, in the coaxial cable according to the present invention, a plurality of conductive wires are wound around the outer periphery of the dielectric layer with respect to the axis of the central conductor, and the angle θ is 8 ° ≦ θ.
By forming a laterally wound shield layer as an outer conductor layer by winding the wire within a range of ≤19 degrees, it is possible to improve electrical characteristics such as a shield effect and to provide a multi-core coaxial cable including a plurality of coaxial cables. When used as a cable, crosstalk between adjacent coaxial cables can be sufficiently small.

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment of a coaxial cable according to the present invention.

FIG. 2 is a diagram showing a winding angle θ in a horizontal winding shield layer of a coaxial cable according to the present invention.

FIG. 3 is a diagram showing the relationship of the shield effect with the winding angle in the coaxial cables of Examples 1 to 5 and Comparative Examples 1 to 4 according to the present invention.

FIG. 4 is a perspective view of an embodiment of a two-core coaxial cable according to the present invention.

FIG. 5 is a diagram showing a relationship between a far-end crosstalk and a near-end crosstalk with respect to a winding angle in the two-core coaxial cables of Examples 6 to 10 and Comparative Examples 5 to 8 according to the present invention.

[Explanation of symbols]

1: center conductor, 2: dielectric layer, 3: horizontal winding shield layer, 3
a: strand wire, 4: protective coating layer 5: coaxial cable, 6: two-core coaxial cable, θ: winding angle

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masayo Emori             20 Jun 96, Fukuda, Kasama City, Ibaraki Prefecture Jun Co., Ltd.             In-house F term (reference) 5G319 FA03 FA04 FC19 FC34

Claims (2)

[Claims] 1. A dielectric layer is provided on the outer circumference of a center conductor, and a horizontal winding shield layer is provided on the outer circumference of the dielectric layer. The horizontal winding shield layer is formed by spirally winding a plurality of conductive wires. In a coaxial cable with a protective coating layer on the outer circumference of the shield layer,
The winding angle θ around which the strand of the horizontally wound shield layer is wound around the dielectric layer is 8 ° ≦ θ with respect to the axis of the central conductor.
A coaxial cable characterized by a range of ≤19 degrees. 2. A dielectric layer is provided on the outer circumference of a center conductor, and a horizontal winding shield layer is provided on the outer circumference of the dielectric layer. The horizontal winding shield layer is formed by spirally winding a plurality of conductive wires. In a coaxial cable with a protective coating layer on the outer circumference of the shield layer,
The winding angle θ around which the strand of the horizontally wound shield layer is wound around the dielectric layer is 8 ° ≦ θ with respect to the axis of the central conductor.
A multi-core coaxial cable including a plurality of coaxial cables in the range of ≤19 degrees.