JPH0237048B2 - FURATSUTOKEEBURU - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to an improvement of a flat cable, and more particularly to an improvement in flat cables that can obtain good crosstalk characteristics and reduce restrictions on the mounting position of a pressure welding connector. This is related to a flat cable that can be used.

Prior Art and Problems In a flat cable in which a plurality of signal lines are arranged in a flat configuration, it is important to reduce the amount of crosstalk between the signal lines.

Figure 1 is a configuration diagram showing an example of a conventional flat cable, in which a twisted pair part a where signal wires are twisted pair by pair and a parallel part b where six signal wires are arranged in parallel are arranged alternately. It is provided. This flat cable is designed to improve the crosstalk characteristics between signal lines by providing a twisted pair part a, and to make it possible to easily attach a pressure welding connector by providing a parallel part b. , it had the following drawbacks: That is, in order to achieve high crosstalk characteristics, the length of the twisted pair part a must be long (usually 500 mm or more), and for this reason,
This has the drawback that the length between the parallel parts b to which the pressure welding connector can be attached becomes long, and the mounting position of the pressure welding connector is restricted. Moreover, since the flat cable shown in FIG. 1 is constructed using a signal line in which only an insulating layer is provided on a conductor, it has the disadvantage that it is easily influenced by external noise.

Furthermore, FIGS. 2A and 2B are cross-sectional views of other conventional examples, showing cross sections in the short and long directions of the flat cable, respectively.

The flat cable shown in Figures A and B has an insulating layer 2 on the outer periphery of each metal conductor 1, and a semiconducting layer 3 on the upper half of each insulating layer 2 intermittently and at a constant rate along the longitudinal direction. They are provided in pitches and covered all at once with an insulating layer 4. Here, the semiconducting layer 3
are conductive plastics with different specific resistances, for example, each type of conductive plastic manufactured by Dainippon Ink Co., Ltd. has a specific resistance of 10 ⁴ to 10 ⁵
TX1036 with Ω-cm or resistivity of 10 ² Ω-cm
It is formed using L2101 etc.

With such a configuration, crosstalk can be reduced for the reasons described below.

Now, as shown in Fig. 3, the capacitance between the metal conductors 1a to 1e is 1/2C, the capacitance between the metal conductors 1b and 1d is C _bd , and the metal conductors 1a, 1c, and 1e are connected to the ground wire and the metal If the conductors 1b and 1d are used as signal lines, the equivalent circuit will be as shown in FIG. In FIG. 4, R is a terminating resistor, which is equal to the characteristic impedance _Z0 . Also, L _bd is the metal conductor 1b, 1
The inductance between d, L _b and L _d is the metal conductor 1b,
The inductance is 1d, and since the flat cable is a symmetrical circuit, L _b =L _d =L.

The far end crosstalk voltage V _d (l,
t) as a function of the input voltage V _IN (t) as follows:
(1) is obtained.

V _d (l, t) = 1/2V _IN (t-l/u) +Z _p /Z _p +Z _e V _IN (t-l/v) ...(1) However, For normal flat cables, C>C _bd , L>L _bd
Therefore, the following equation (6) can be obtained.

Further, if a pulse signal with a rise time of T ₁ is output from the signal source E, the equation (1) becomes as shown in the following equation (7).

V _d (l, t) = 1/2Δtd/dtV _IN (t-l/u)...
…(7) However, Δt=l/u−l/v≒l(−L _bd /Z _p +C _bd Z _p )…
...(8) Also, _the maximum voltage V _d (l,
t) _nax is shown in the following equation (9).

V _d (l, t) _nax =Δt/2T ₁ (9) Here, the far-end crosstalk K _f (%) is expressed by the following equation (10).

K _f = [V _d (l, t)/V _IN (t)] _nax ×100……(10
) Therefore, in order to reduce the far-end crosstalk K _{f ,} it is sufficient to reduce V _d (l, t) _nax shown in equation (9). Here, V _d (l, t) _nax is proportional to the cable length l and the term (-L _bd /Z _p +C _bd Z _p ),
It is inversely proportional to the signal rise time T ₁ , but since l and T ₁ are constants, the far-end crosstalk K _f is (−
L _bd /Z _p + C _bd Z _p ).

In a normal flat cable, since there is air with a small dielectric constant in the outer space, C _bd becomes small,
L _bd /Z _p > C _bd Z _p . Therefore, in order to reduce the far-end crosstalk K _f , it is sufficient to increase the capacitance C _bd between the metal conductors 1 b and 1 d.

Since the flat cable shown in FIGS. 2A and 2B is provided with a semiconducting layer 3, the capacitance between each metal conductor 1 can be increased, and therefore, far-end crosstalk K _f can be reduced. In addition, the flat cables shown in Figures A and B do not require a twisted pair portion unlike the conventional flat cable shown in Figure 1, so there are no restrictions on the mounting position of the insulation displacement connector. It disappears.

However, the flat cables shown in FIGS. 2A and 2B had the following drawbacks. That is, it has the drawback of being easily influenced by external noise and the drawback of not being able to obtain sufficient near-end crosstalk.

Purpose of the Invention The present invention is to improve the above-mentioned drawbacks, and its purpose is to obtain good crosstalk characteristics, be less susceptible to external noise, and have fewer restrictions on the mounting position of the pressure welding connector. The purpose of this invention is to provide a flat cable that can be used as a flat cable. Examples will be described in detail below.

Embodiment of the Invention FIG. 5 is a sectional view of an embodiment of the invention, showing a cross section of a flat cable in the short direction. In this figure, 5 is a shield made of metal mesh tape, metal foil, composite tape of metal foil and plastic film, etc., and 6 is a sheath, and the same reference numerals as in other figures A and B represent the same parts. There is.

Since this embodiment also includes the semiconducting layer 3 as in the conventional example shown in FIGS. 2A and 2B, far-end crosstalk can be made good, and the Since there is no need to provide a twisted pair portion as in the conventional example shown in FIG. 1, the pressure welding connector can be easily attached to any position.
Further, in this embodiment, since a shield 5 is provided, the influence of external noise can be eliminated.

FIG. 6 is a diagram showing the relationship between the far end crosstalk K _f and the space factor of the flat cables shown in FIGS. 2A and B and FIG. 5, and the vertical axis is the far end crosstalk K _f , and the horizontal axis shows the occupancy factor. still,
As shown in FIG. 7, the space factor is calculated as follows: a is the length in the longitudinal direction of the part where the semiconducting layer 3 is not provided, and a is the length in the longitudinal direction of the part where the semiconducting layer 3 is provided. b
Then, it is expressed as b/a+b×100 (%). In addition, solid lines a and b indicate the conductive plastic TX1036, the semiconductive layer 3 of which was exemplified above, respectively.
This shows the far end crosstalk K _f of the flat cables shown in Figures 2A and B with L2101, and the dotted lines c,
d is the far end crosstalk of the flat cable in Fig. 5 with semiconducting layer 3 of TX1036 and L2101, respectively.
This shows K _f .

Moreover, FIG. 8 is a diagram showing the relationship between the near-end crosstalk K _n and the space factor of the flat cables shown in FIGS. 2A and B and FIG. 5, and the vertical axis is the near-end crosstalk. K _o is shown, and the horizontal axis shows the space factor.
Furthermore, solid lines a and b indicate the near-end crosstalk _{K o} of the flat cables shown in FIGS. 2A and B in which the semiconducting layer 3 is made of the conductive plastics TX1036 and L2101, respectively, as exemplified above, and the dotted line c , d are the fifth layers with semiconducting layer 3 of TX1036 and L2101, respectively.
The figure shows the near-end crosstalk K _o of a flat cable.

As can be seen from Figure 6, the far end crosstalk K _f is
By appropriately setting the space factor, the near-end crosstalk K _o can be reduced to zero by providing the shield 5, as shown in Figure 8.
This can be reduced compared to the conventional examples shown in Figures A and B.

The flat cable shown in FIG. 5 is manufactured, for example, as follows. That is, a metal conductor provided with an insulating layer is used as a composite film consisting of a semiconducting film 8 with holes 7 formed at a constant pitch P and an insulating plastic film 9, as shown in FIG. 9, and an insulating plastic film. It is constructed by heat-pressing these in between and then providing a shield and a sheath.

Effects of the Invention As explained above, in the present invention, a semiconducting layer is intermittently provided on the outer periphery of the first insulating layer (insulating layer 2 in the embodiment), so far-end crosstalk can be prevented. Furthermore, since there is no need to provide a twisted pair portion, there is an advantage in that there are no restrictions on the mounting position of the pressure welding connector. Furthermore, since the present invention is provided with a shield, it has the advantage of being less susceptible to external noise and also has the advantage of improving near-end crosstalk.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a conventional example, Fig. 2 A and B are cross-sectional views of other conventional examples, Fig. 3 is a section showing the capacitance between metal conductors, and Fig. 4 is an equivalent circuit of Fig. 3. , FIG. 5 is a cross-sectional view of an embodiment of the present invention, FIG. 6 is a diagram showing the relationship between far-end crosstalk and space factor, FIG. 7 is an explanatory diagram of space factor, and FIG. 8 is a diagram showing the relationship between far-end crosstalk and space factor. FIG. 9 is a diagram showing the relationship between crosstalk and space factor, and is a perspective view of a composite film used in manufacturing the flat cable shown in FIG. 5. 1, 1a to 1e are metal conductors, 2, 4 are insulating layers,
5 is a shield, and 6 is a sheath.

Claims (1)

[Claims] 1 A plurality of metal conductors arranged in parallel, a first insulating layer provided on the outer periphery of each of the metal conductors, and a first insulating layer provided intermittently along the longitudinal direction on the outer periphery of the first insulating layer. What is claimed is: 1. A flat cable comprising: a semi-conductive layer, a second insulating layer that collectively covers these layers, and a shield that covers the second insulating layer.