JP2865069B2 - Termination method of shield - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of terminating a shield, and more particularly to a method of terminating a shield of a coaxial cable having at least one central conductor or a shielded twisted pair.

[0002]

2. Description of the Related Art In a coaxial cable having at least one central conductor or a transmission line (hereinafter simply referred to as a cable) which can be either a shielded twisted pair or a coaxial cable, an outer conductor or a shielded twisted pair is used in a coaxial cable. In terminating a shield (hereinafter simply referred to as a shield), conventionally, a method shown in FIG. 4 is used.

[0003] That is, FIG. 4 (a) shows an end of a shield 2 of a cable having a pair wire or a core wire 3 depending on the center via a signal line 10 to the ground (protective or supporting conductor, building, etc.).
(The same applies hereinafter.) The method shown in FIG. 2B is a method in which the cable shield 2 is terminated by leaving the end of the shield 2 open. .

[0004]

However, in the above-described conventional method of terminating the shield, since the end of the shield of the cable is directly connected to the ground potential or opened,
If a surge or noise occurs on the ground, it will be reflected at the end of the shield, generating a standing wave or generating excessive voltage and current, which will affect nearby circuits,
It may cause malfunction or destruction.

[0005] The present invention has been made in view of the above points,
It is an object of the present invention to provide a shield termination method capable of reducing reflection of a surge or noise generated in a cable shield at a shield end.

[0006]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a shield for a cable having a twisted pair or core wire as a center conductor, the resistance of which is equal to or close to the impedance with respect to the ground. And a terminating resistor having a terminal between the terminal of the shield and the ground potential.

[0007] When noise or surge occurs in the cable shield due to external factors, it propagates toward one or both ends of the cable. After this noise or surge reaches the end of the cable, it is consumed by the terminating resistor connected between the cable shield and the ground potential, so that reflection at the end of the cable shield can be significantly reduced or eliminated. it can.

[0008]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory view of an embodiment of the present invention. As shown in the figure, a shield 2 of a cable having a twisted pair or core wire 3 of a cable as a center conductor has a terminal portion whose end is equal to or approximately equal to the impedance value of the shield 2 of the cable with respect to the ground. Is terminated by being connected to ground (ground potential) via a terminating resistor 1 having a resistance value of

Next, the operation of this embodiment will be described with reference to FIG.
It is explained together with. In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals. In FIG. 2, the noise or surge 4 generated in the shield 2 of the cable propagates toward the end of the shield 2 of the cable. When this noise or surge 4 reaches the end of the shield 2 of the cable, FIG.
As shown by, it flows into the terminating resistor 1 and is consumed by the terminating resistor 1.

As a result, the reflection at the end of the cable shield 2 is reduced, and as a result, the cable shield 2
Standing waves, excessive voltages and currents generated on the upper side are reduced.

[0012]

Next, an embodiment of the present invention will be described with reference to FIG. FIG. 3 shows a configuration diagram of an embodiment of the present invention. In the figure, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals,
The description is omitted. In FIG. 3, one end 31 and the other end 32 of the twisted pair or core wire of the cable, which is the center conductor of the shield 2 of the cable, have a resistance equal to or approximately equal to the impedance value of the shield 2 of the cable with respect to the ground. It is connected to the ground via terminating resistors 11 and 12 each having a value.

Further, one end 31 of the twisted pair or core wire is connected to the output terminal of the driver IC 7, and the other end 32 of the twisted pair wire or core wire is connected to the input terminal of the receiver IC 8 and output from the driver IC 7. A cable circuit for transmitting a signal to the receiver IC 8 by a twisted pair wire or a core wire is configured.

Next, the operation of this embodiment will be described with reference to FIG. The noise or surge generated in the shield 2 of the cable propagates toward both ends of the cable as shown by 4 and 41 in FIG. When this noise or surge 4, 41 reaches both ends of the shield 2 of the cable,
As shown by 5 and 51 in FIG. 3, they flow into the terminating resistors 12 and 11 and are consumed by the terminating resistors 12 and 11, respectively.

As a result, the reflection at both ends of the cable shield 2 is reduced, and as a result, the cable shield 2
Since standing waves, excessive voltages, and currents generated above are reduced, malfunction and destruction of nearby circuits can be significantly improved.

[0016]

As described above, according to the present invention,
When the end of the cable shield is connected to the ground potential via a terminating resistor with a value equal to or close to the impedance of the cable shield with respect to the ground, noise or surge generated in the cable shield due to external factors can be reduced. Because it is consumed by the terminating resistor and the reflection at the end of the cable shield is greatly reduced or eliminated, standing waves, excessive voltage and current generated in the shield can be significantly reduced, and malfunctions of nearby circuits Destruction can be greatly improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of one embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of one embodiment of the present invention.

FIG. 3 is a configuration diagram of one embodiment of the present invention.

FIG. 4 is an explanatory diagram of a conventional method.

[Explanation of symbols]

1, 11, 12 Terminating resistor 2 Cable shield 3, 31, 32 Cable twisted pair or coaxial cable core wire 4, 41 Noise or surge generated in cable shield 5, 51 Noise or surge flowing into terminal resistor 7 Driver 7 IC 8 Receiver IC

Claims (2)

(57) [Claims] 1. A shield of a cable having a twisted pair or a core wire as a center conductor has a terminating resistor having a resistance value equal to or close to the impedance with respect to the ground, between a terminal of the shield and a ground potential. A method for terminating a shield, comprising connecting. 2. The cable comprises a cable circuit for transmitting a signal output from a driver to a receiver via the twisted pair wire or the core wire, wherein the terminal is provided between both ends of a shield of the cable and a ground potential. 2. The method according to claim 1, wherein the resistors are connected separately.