JPS62136706A - Low noise coaxial cable - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a low-noise coaxial cable used for audio, medical, measuring equipment, etc.

Figure 1 shows the structure of a general coaxial cable (shielded cable). In the figure, 1 is a core wire, and 2 is an insulating material covering the core wire 1, such as polyethylene, foam, etc. polyethylene,
With vinyl chloride, Teflon, etc.

be. 3 is a braided structure arranged around the insulator 2;

The conductor is made of a coiled copper pipe or the like, and 4 is an insulating sheath. In a coaxial cable with such a structure, when vibration or bending is applied to the cable, the surface of the insulator is charged due to friction between the insulator 2 and the conductor 1 or 3, and this charged charge is transferred to the conductor. It is generally well known that the particles move and appear as noise on the output side. Such noise can cause abnormal malfunctions in, for example, high-input impedance full-circle meters, highly sensitive measuring instruments, and electronic equipment, so electric wires are used that take various countermeasures.

Figure 2 shows an example of an electric wire that has taken such measures.
The same numbers as in FIG. 1 indicate the same contents. In the figure, conductive plastic 5 is placed inside and outside the insulator 2.
6 is provided to prevent the conductors 1 and 3 from directly touching the insulator 2, and the conductive plastic 5.6 is tightly coated to minimize the amount of charge.

In addition, in the case of Fig. 3, the conductive plastic 7 is tightly coated only on the outside of the insulator 2, and although it is less effective than the case of Fig. 2, it has lower noise than the case of Fig. 1. Effects can be obtained.

Furthermore, in order to prevent static electricity, an antistatic agent is mixed into or applied to the insulator 2 shown in FIG. 1 or on its surface.

However, all of these methods either provide a conductive substance between the insulator and the conductor, or mix or coat an antistatic agent with poor insulation properties in or on the insulator, resulting in poor performance as an insulator. 6 Also, when a high-fidelity signal such as audio is applied to a coaxial cable with the structure shown in Figure 1, a force acts between the conductors due to the signal current. Vibration occurs, resulting in charge build-up, and the applied signals cause the charge remaining on the surface of the insulator to move irregularly or in response to the signal, resulting in deterioration of sound quality. In addition, when used for wiring high amplification parts such as players, when a shock is applied to the cable, noise may be emitted from the speaker as audio, which is not only unpleasant but can also damage the speaker. .

■-1 The present invention has been made in view of the above circumstances, and it is possible to reduce vibrations and
It is not affected by the transfer of electrical charges to the conductor due to friction such as bending, and is less likely to cause vibrations due to signal current.
This was done with the aim of providing a coaxial cable that is less likely to generate noise.

Configuration The low noise coaxial cable of the present invention includes a first insulating material coated around a first conductor that is a center conductor, a second conductor covering the first insulating material, and a second conductor covering the first insulating material. around the conductor of
a third conductor covering the second insulator, a third insulator covering the third conductor, and a third conductor covering the third conductor; Only one terminal is connected between the conductors by an impedance element, and the first conductor is the center electrode.
It has a configuration in which the third conductor is a surrounding electrode.

With this configuration, the current caused by the charged charges has almost no effect on the load.

FIG. 4 is a diagram showing an embodiment of the coaxial structure shielded cable of the present invention, in which 10 is a first conductor constituting the center electrode, and 11 is an insulator coated around the first conductor. ,1
2 is a second conductor (shield) coated around the insulator 11, 13 is an insulator coated around the second conductor 12, and 14 is a third conductor (shield) that constitutes the peripheral electrode. (shield), 15 is an insulator that covers the third conductor, and the first conductor 1o and the second conductor 10 are connected to each other at one end with an impedance of −6.

In the shielded wire shown in FIG. 4, the conductor 12 is connected to the conductor 10 at one end via an impedance 16,
Since the other ends are open, the conductors 10 and 12 have the same potential, and the movement of charged charges due to the influence of the signal applied to the conductor 10 is less likely to occur, and furthermore, there is no closed circuit between the conductors 10 and 12. Therefore, since there is no part through which the charged charges flow, it is less likely to affect the load. In addition, since it is difficult for the signal current to flow through the conductor 12, the force acting between the conductors 12 and 14 is weak, and the vibration of the conductor due to the signal current is small, so that static electricity is generated due to frictional electricity and noise is generated. Hateful.

Figures 5 and 6 are diagrams for explaining why the coaxial cable according to the present invention is less likely to generate noise. Figure 5 is a schematic diagram of the cable in Figure 4, and 10° 12.14.16 is ,
Figure 6 is a schematic diagram of the cable in Figure 1, 1 and 3 indicate the same conductors as in Figure 1, and e , L indicate a signal source and a load, respectively.

First, in the conventional coaxial cable shown in FIG. 6, when a heavy charge flows between the conductors 1 and 3, the current flows to the load through the path shown by arrow 1, causing noise. On the other hand, in the case of the present invention shown in FIG.
Arrow j) indicates that the conductors are open at the terminals, so there is no closed circuit, and it is difficult to affect the load, and the conductor 12.1
The charged electric charge flow (arrow k) generated between 4 forms a closed circuit passing through the impedance 16 and the central conductor 10, but by setting the impedance to an appropriate value (for example, 100Ω to 50Ω), the load This can be done to the extent that it has almost no effect on the

Next, using the measurement circuit shown in FIG. 7, the voltage generated by the impact in the cable shown in FIGS. 1 to 4 was measured, and Table 1 shows the results. In FIG. 7, the reference numeral 20 indicates a measuring device, and the reference numeral 22 indicates a 100 g weight which is dropped from a height of 30 mm above the cable to apply an impact to the cable.

As is clear from Table 1, the cable of FIG. 4 generates a smaller voltage than the conventional cables of FIGS. 1 to 3.

FIG. 8 is a diagram showing an example of an audio signal cord with a pin plug using the cable shown in FIG. 4. The same numbers as in FIG. 4 indicate the same contents, and 17 is a pin plug.

The total length is 1.5 m, the center conductor 10 is connected to the center of the pin plug 17, and the impedance 16 is a pure resistance 2.
2 is connected to Ω, and a shield portion 14 is connected to the ground portion of the pin plug.

An embodiment of the present invention has been described above, but if a litz wire is used as the conductor in order to further reduce the influence of the skin effect of the conductor, the sound quality can be improved, especially as an audio hi-fi cord. In this case, the effect can be further enhanced by using a resin having higher insulation properties such as Teflon than the commonly used polyurethane resin.

Effects As described above, according to the present invention, the surface skin of the insulator does not cause the insulation deterioration that occurs when a conductive substance or antistatic agent is used inside, and fiFffi charges are generated. Furthermore, it is possible to obtain a cable that is less likely to generate noise due to the generated electrical charges.

[Brief explanation of drawings]

Figures 1 to 3 are diagrams showing conventional coaxial cables;
5 is a schematic diagram of the coaxial cable of FIG. 4, and FIG. 6 is a diagram of the coaxial cable of FIG.
Figure 7 is a schematic diagram of a coaxial cable, Figure 7 is a diagram showing a cable measurement circuit, and Figure 8 is a diagram showing a pin-plug size audio signal cord using the cable according to the present invention. 10... Central horse body, 11.13... Insulator, 12.
...4 bodies, 14...surrounding electrode, 15...insulator (sheath), 16...impedance. Patent applicant: Daisho Electric Industry Co., Ltd. mI Figure 2 Figure 3 Figure 4 Figure 8 Figure 5 Figure 6 Figure 7

Claims (3)

[Claims] (1) A first insulator is coated around the first conductor, which is the center conductor, a second conductor is coated around the first insulator, and a second conductor is coated around the second conductor. cover the second insulator with a third conductor, cover the third conductor with a third insulator, and create an impedance between the first conductor and the second conductor. A low-noise coaxial cable in which only one end is connected by an element, the first conductor is the center electrode, and the third conductor is the peripheral electrode. (2) A low-noise coaxial cable according to claim (1), which uses a Litz wire as a conductor. (3) A low-noise coaxial cable according to claim (2), wherein the insulating material is a highly insulating material such as Teflon.