JP2008054100A - Signal transmission device and signal transmission method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a communication quality regarding a signal transmission device and a signal transmission method which transmit an electrical signal to a vehicle mounted equipment mounted on a vehicle such as automobile. <P>SOLUTION: When signals with a plurality of pulse widths are transmitted from a transmission side 10 to a receiving side 14 through twist pair lines of lines 11, 13 and an intermediate connector 12 which are transmission lines 11A, a reflected wave 11b which occurs because of reflection of a travelling wave 11a of a signal by a reflected wave delay portion 15 as a reflected wave delay means formed on the line 11 is delayed so as to be λ/4 of a minimum pulse width of the travelling wave 11a, an influence of the reflected wave 11b which generates disturbance of waveforms for the travelling wave 11a is reduced, and a time difference between a positive amplitude of a composit wave 11c and a negative amplitude in each cycle (half cycle) is reduced, so that jitter of the composit wave 11c is reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a signal transmission device and a signal transmission method for transmitting an electrical signal to an in-vehicle device mounted on a vehicle such as an automobile.

  As a signal transmission device that transmits an electrical signal to an in-vehicle device, a twisted pair wire obtained by twisting a pair of covered wires is widely used. The twisted pair wire is less susceptible to electromagnetic noise due to electromagnetic induction and has higher communication reliability than a parallel wire in which a pair of covered wires are arranged in parallel or substantially in parallel.

  As a signal transmission device using such a twisted pair wire, for example, there are three pairs of twisted pair wires connected to a terminal inserted into a terminal receiving chamber of the connector at the tip, and the twisted pair wires on the terminal side are each 1/3 pitch. Some are twisted back so that the phase is shifted.

  However, in such a signal transmission device, when the twisted pair wires connected to the connector are untwisted, the induced electromotive forces are added to each other, the noise voltage increases, the capacitance increases, the noise current increases, and the electromagnetic current increases. There is a risk that noise due to induction and electrostatic induction may occur, causing in-vehicle devices to malfunction.

  In addition, when there are a plurality of twisted pair wires connected to the connector, adjacent twisted pair wires must be colored for identification, and there is a problem that the types of electric wires increase and the cost increases.

In order to solve such a problem, in Patent Document 1, a twist-back portion for connecting to a connector is formed on at least one side of a twisted pair wire formed by twisting a plurality of electric wires, and a plurality of twist-back portions are provided in the twist-back portion. A twisted pair wire is proposed in which shrink members for bundling the wires are attached and the colors of the respective shrink members are different.
JP 2004-103396 A

  By the way, in the twisted pair wire in Patent Document 1 described above, the plurality of electric wires in the untwisted portion are bundled by the contraction member, and the distance between the electric wires is prevented from being separated, thereby reducing the impedance of the transmission line. Radiation noise can be reduced, and adjacent twisted pair wires can be identified without coloring by contracting members of different colors.

  However, in such a configuration, when an impedance mismatch occurs in a transmission line such as a twisted pair wire, a traveling wave is reflected at that point, and a problem due to the generation of a reflected wave occurs.

  That is, as shown in FIG. 8, it is assumed that a signal having a plurality of pulse widths is transmitted from the transmission side 1 to the reception side 5 via lines 2 and 4 such as twisted pair wires and the intermediate connector 3. Here, the lines 2 and 4 and the intermediate connector 3 between the transmission side 1 and the reception side 5 are the transmission path 2A. In addition, the code | symbol 3a, 3b in the figure has shown the twist back part (or opening).

  Here, if there is no impedance mismatch in the transmission lines 2A, that is, the lines 2 and 4 and the intermediate connector 3, a signal having a waveform as shown in FIG. 9A is transmitted from the transmission side 1 to the reception side 5. The Further, the eye pattern of the signal in the case where no impedance mismatch occurs is represented by a waveform with good quality without any waveform disturbance as shown in FIG. 9B.

  However, when the impedance mismatch 3A occurs in the portion surrounded by the dotted line in the drawing by the untwisted portions 3a and 3b shown in FIG. 8, the traveling wave a from the transmission side 1 is reflected at that point, and the reflected wave b is generated. To do. The reflected wave b travels in the opposite direction to the traveling wave a and travels toward the transmitting side 1. At this time, if impedance matching is established at the transmission end of the transmission side 1, the reflected wave b is absorbed by the transmission side 1.

  On the other hand, if impedance matching is not achieved at the transmitting end of the transmitting side 1, the reflected wave b is further reflected at the transmitting end of the transmitting side 1 and reflected to the traveling wave a as shown in FIG. The resultant wave c is a combination of the waves b. The eye pattern in this case is represented by a waveform having a poor quality due to a disturbance in the waveform as shown in FIG.

  This is because the phase of the reflected wave b reflected by the impedance mismatch 3A portion is synthesized with an arbitrary time shift from the phase of the traveling wave a, so that each of the positive amplitude and the negative amplitude of the synthesized wave c is combined. This is because there is a time difference in the period (half period), and this becomes jitter, resulting in a poor quality waveform. Therefore, when the jitter of the synthesized wave c increases, there is a problem that communication quality is deteriorated and normal communication from the transmission side 1 to the reception side 5 may not be performed.

  The present invention has been made in view of such a situation, and an object thereof is to provide a signal transmission device and a signal transmission method capable of solving the above-described problems.

The signal transmission device of the present invention is a signal transmission device that transmits a signal having a plurality of pulse widths from the transmission side to the reception side via a transmission line composed of a twisted pair wire, and the signal is transmitted to the transmission line. Reflected wave delay means for delaying a wave by a predetermined time and reflecting it to the transmitting side is formed.
Further, the reflected wave delay means may be an inductor inserted into the transmission line.
Further, the reflected wave delay means may be formed of a twisted space having a predetermined width.
The reflection delay time may be λ / 4 of the minimum pulse width among the plurality of pulse widths.
Further, the reflection may be caused by impedance mismatch caused by untwisting of the twisted-pair wire at least at a relay connector provided in the transmission line.
The signal transmission method of the present invention is a signal transmission method for transmitting a signal having a plurality of pulse widths from the transmission side to the reception side via a transmission path composed of twisted pair wires, and a reflected wave formed in the transmission path The traveling wave of the signal is delayed by a predetermined time by the delay means and reflected to the transmission side.
Further, the reflected wave delay means may be an inductor inserted into the transmission line.
Further, the reflected wave delay means may be formed of a twisted space having a predetermined width.
The reflection delay time may be λ / 4 of the minimum pulse width among the plurality of pulse widths.
Further, the reflection may be caused by impedance mismatch caused by untwisting of the twisted-pair wire at least at a relay connector provided in the transmission line.
In the signal transmission device and the signal transmission method of the present invention, when a signal having a plurality of pulse widths from the transmission side is transmitted to the reception side via the transmission line composed of a twisted pair line, reflected wave delay means formed in the transmission line By delaying the traveling wave of the signal for a predetermined time and reflecting it to the transmission side, the phase of the reflected wave waveform is shifted by a predetermined time from the phase of the traveling wave waveform, and the traveling wave and the reflected wave are combined. The time difference in each cycle (half cycle) of the positive amplitude and the negative amplitude of the wave is reduced, and the jitter of the synthesized wave is reduced.

  According to the signal transmission apparatus and the signal transmission method of the present invention, since the jitter of the synthesized wave is reduced, the communication quality can be improved.

  In this embodiment, when a signal having a plurality of pulse widths from the transmission side is transmitted to the reception side via a transmission path composed of a twisted pair line, the traveling wave of the signal is reflected by the reflected wave delay means formed in the transmission path. Reflected to the transmitting side after a predetermined time delay, the phase of the reflected wave is shifted by a predetermined time from the phase of the traveling wave, and the positive and negative amplitudes of the combined wave of the traveling wave and the reflected wave The quality of communication is improved by reducing the time difference in each cycle (half cycle) and reducing the jitter of the synthesized wave.

  Details of the embodiments of the present invention will be described below. FIG. 1 is a diagram for explaining an embodiment of a signal transmission apparatus of the present invention.

  As shown in the figure, the signal transmission device is configured such that a signal having a plurality of pulse widths is transmitted from the transmission side 10 to the reception side 14 via the line 11, the intermediate connector 12 and the line 13. Here, the line 11, the intermediate connector 12, and the line 13 between the transmission side 10 and the reception side 14 are transmission lines 11A. The lines 11 and 13 are formed of twisted pair wires. The line 11 is formed with a reflected wave delay unit 15 as reflected wave delay means. In addition, the code | symbol 12a, 12b in the figure has shown the twist back part (or opening) of a twisted pair wire.

  Reference numeral 11a is a traveling wave of the signal from the transmission side 10, and reference numeral 11b is a reflected wave reflected by the transmission side 10 after the traveling wave of the signal from the transmission side 10 is delayed by a predetermined time by the reflected wave delay unit 15. It is. Further, the reflected wave 11b includes a wave reflected by the transmission end of the transmission side 10. Reference numeral 11c is a composite wave in which the reflected wave 11b overlaps the traveling wave 11a.

  Here, the reflected wave delay unit 15 delays the above-described reflected wave 11b by λ / 4 time of the minimum pulse width of the traveling wave 11a, as will be described later. When such a reflected wave delay unit 15 is formed, a method of inserting an inductor (L) in the line 11 of the transmission line 11A or a twisted space having a predetermined width is formed in the line 11 of the transmission line 11A as described below. There are methods.

  FIG. 2 is a diagram for explaining a method of inserting an inductor (L) into the line 11 of the transmission line 11A. First, as the inductor (L), for example, an FB (ferrite bead) 15a can be used as shown in FIG. Here, when the FB (ferrite bead) 15a is inserted into the line 11 of the transmission line 11A, the middle of the line 11 is cut, and the FB (ferrite bead) 15a is inserted into the cut portion.

  Further, as shown in FIG. 2B, an FB (ferrite bead) 15b is clamped from above the line 11 of the transmission line 11A.

  FIG. 3 is a diagram for explaining a method of forming a twisted space having a predetermined width in the line 11 of the transmission line 11A. As shown in the figure, the twisted space in the case of forming the reflected wave delay unit 15 is preferably as large as possible. However, in practical use, a sufficient effect can be obtained with about 25 to 35 mm.

  In addition, as shown in FIG. 4, when the intermediate connector 15c is provided at a place where the reflected wave delay portion 15 of the line 11 of the transmission line 11A is necessary, an inductor 15d may be inserted into the intermediate connector 15c.

  FIG. 5 is a diagram for explaining the characteristics of the reflected wave delay unit 15 formed on the line 11 of the transmission line 11A. That is, FIG. 5A shows a combined wave 11c of the traveling wave 11a and the reflected wave 11b. Here, the reflected wave 11b is delayed by the reflected wave delay unit 15 so as to be λ / 4 time of the minimum pulse width of the traveling wave 11a, as shown in FIG. .

  As a result, the phase of the waveform of the reflected wave 11b is shifted by λ / 4 time with respect to the phase of the waveform of the traveling wave 11a, so that the influence of the reflected wave 11b that causes the waveform disturbance to the traveling wave 11a is reduced. Since the positive amplitude and the negative amplitude of the composite wave 11c are uniformly increased, the slope of the waveform of the composite wave 11c becomes steep. And the time difference in each period (half cycle) of the positive amplitude and negative amplitude of the synthetic wave 11c becomes small, and the jitter of the synthetic wave 11c decreases. As a result, as shown in FIG. 6, the eye pattern is represented by a waveform having a good quality with no waveform disturbance.

  Next, a signal transmission method will be described. First, as shown in FIG. 7, a signal having a plurality of pulse widths from the transmission side 10 is output to the line 11 of the transmission line 11A (step S1). At this time, the traveling wave 11a from the transmission side 10 is normally reflected at the point 11b due to the impedance mismatch 12A by the untwisting portions 12a and 12b, and returns to the transmission side 10. The reflected wave 11b is also reflected at the transmission end of the transmission side 10, and the reflected wave 11b is overlapped with the traveling wave 11a to become a combined wave 11c.

  However, in the present embodiment, the traveling wave 11a is reflected by the reflected wave delay unit 15 provided in the line 11 in front of the untwisted portions 12a and 12b in the transmission line 11A. The reflected wave 11b resulting from this reflection is delayed by the reflected wave delay unit 15 by λ / 4 time of the minimum pulse width of the traveling wave 11a.

  As a result, the reflected wave 11b from the reflected wave delay unit 15 is delayed by the reflected wave delay unit 15 by λ / 4 time of the minimum pulse width of the traveling wave 11a (step S2), so that the phase of the waveform of the reflected wave 11b is The phase of the waveform of the traveling wave 11a is shifted by λ / 4 time, and the influence of the reflected wave 11b causing the waveform disturbance to the traveling wave 11a is reduced, and the positive amplitude and the negative amplitude of the synthesized wave 11c are reduced. The time difference in each cycle (half cycle) is reduced, and the jitter of the synthesized wave 11c is reduced. As a result, unlike the eye pattern shown in FIG. 6, there is no waveform disturbance and a good quality waveform is obtained (step S3).

  As described above, in this embodiment, when a signal having a plurality of pulse widths from the transmission side 10 is transmitted to the reception side 14 via the twisted pair line 11 and 13 and the intermediate connector 12 as the transmission line 11A, The reflected wave 11b generated by reflecting the traveling wave 11a of the signal by the reflected wave delaying part 15 as the reflected wave delaying means formed on the line 11 is set to λ / 4 time of the minimum pulse width of the traveling wave 11a. Was delayed.

  As a result, the influence of the reflected wave 11b that causes the waveform disturbance to the traveling wave 11a is reduced, and the positive amplitude and the negative amplitude of the synthesized wave 11c are equally enhanced, so that the slope of the waveform of the synthesized wave 11c is increased. Becomes steep, the time difference in each cycle (half cycle) of the positive amplitude and the negative amplitude of the synthesized wave 11c is reduced, so that the jitter of the synthesized wave 11c can be reduced, and the communication quality can be reduced. Can be improved.

  In the present embodiment, the case where the delay time of the reflected wave 11b by the reflected wave delay unit 15 is set to λ / 4 of the minimum pulse width of the traveling wave 11a has been described. The minimum pulse width is not limited to λ / 4. That is, for example, if it is extremely smaller than λ / 4, the waveform of the traveling wave 11a may be distorted by multiple reflection or the like, but in the range close to λ / 4, the same effect as λ / 4 can be obtained. This is because the results are known. However, since the delay time of the reflected wave 11b by the reflected wave delay unit 15 varies depending on the characteristics of the transmission path 11A and the like, it is preferably set as appropriate according to the characteristics of the transmission path 11A.

  The present invention can be applied not only to a vehicle but also to a system that performs data communication.

It is a figure for demonstrating one Example of the signal transmission apparatus of this invention. It is a figure for demonstrating the method of inserting an inductor (L) in the transmission line of FIG. It is a figure for demonstrating the method of forming the twist space of a predetermined width in the transmission line of FIG. FIG. 3 is a diagram for explaining a case where an inductor is inserted into an intermediate connector when the intermediate connector is provided at a position where a reflected wave delay unit of the transmission line in FIG. 1 is required. It is a figure for demonstrating the characteristic of the reflected wave delay part of FIG. It is a figure which shows the eye pattern by the reflected wave delay part of FIG. 2 is a flowchart for explaining a signal transmission method by the signal transmission apparatus of FIG. 1. It is a figure which shows an example of the conventional signal transmission apparatus. It is a figure for demonstrating the case where the impedance mismatch does not arise in the signal transmission apparatus of FIG. It is a figure for demonstrating the case where impedance mismatching has arisen in the signal transmission apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission side 2,4 Line 2A Transmission path 3 Intermediate connector 3A Impedance mismatch 3a, 3b Untwisted part (or opening)
5 Reception side 10 Transmission side 11, 13 Line 11A Transmission path a, 11a Traveling wave b, 11b Reflected wave c, 11c Composite wave 12 Intermediate connector 12A Impedance mismatch 12a, 12b Untwisted part (or open)
14 Receiving side 15 Reflected wave delay unit (reflected wave delay means)
15c Intermediate connector 15d Inductor

Claims (10)

A signal transmission device for transmitting a signal having a plurality of pulse widths from a transmission side to a reception side via a transmission path composed of a twisted pair line,
Reflection wave delay means for delaying a traveling wave of the signal for a predetermined time and reflecting it to the transmission side is formed in the transmission line.   The signal transmission device according to claim 1, wherein the reflected wave delay unit is an inductor inserted into the transmission path.   2. The signal transmission device according to claim 1, wherein the reflected wave delay means is formed of a twisted space having a predetermined width.   The signal transmission device according to claim 1, wherein the reflection delay time is λ / 4 of a minimum pulse width among the plurality of pulse widths.   5. The signal transmission device according to claim 1, wherein the reflection is caused by impedance mismatch caused by twisting back of the twisted pair wire at least at a relay connector provided in the transmission line. . A signal transmission method for transmitting a signal having a plurality of pulse widths from a transmission side to a reception side via a transmission path composed of a twisted pair line,
A signal transmission method, wherein the traveling wave of the signal is delayed by a predetermined time by the reflected wave delay means formed in the transmission path and reflected to the transmission side.   The signal transmission method according to claim 6, wherein the reflected wave delay means is an inductor inserted into the transmission path.   The signal transmission method according to claim 6, wherein the reflected wave delay means is formed of a twisted space having a predetermined width.   9. The signal transmission method according to claim 6, wherein the reflection delay time is λ / 4 of a minimum pulse width among the plurality of pulse widths. 10. The signal transmission method according to claim 6, wherein the reflection is caused by impedance mismatch caused by twisting back of the twisted pair wire at least at a relay connector provided in the transmission line. .

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