WO1987000712A1

WO1987000712A1 - Transmission system

Info

Publication number: WO1987000712A1
Application number: PCT/DE1986/000288
Authority: WO
Inventors: Fritz Haberl
Original assignee: Messerschmitt-Bölkow-Blohm Gmbh
Priority date: 1985-07-17
Filing date: 1986-07-16
Publication date: 1987-01-29
Also published as: EP0227759A1; JPS63500348A; DE3525519A1

Abstract

Transmission system (1) comprising at least one transmitter (2) and one receiver (3), which are connected by means of data lines (4) originating from signal and reference lines or earth lines (4s, 4r). In order to attenuate in a simple manner interference signals inherent in the circuit, which are produced during the transmission of asymmetric signals, for example steeply-rising signals or digital signals, at least one 1:1 transformer (6) with the heighest possible coupling coefficient (K) is inserted in each possible signal communication path between any transmitter (2) and any receiver (3). The primary side (5) of the transformer is connected to the reference line (4r), and the secondary side (7) is connected to the corresponding section of the signal line (4s).

Description

Transmission system

The invention relates to a transmission system according to the preamble of claim 1.

Such transmission or bus systems have at least one transmitter and one receiver, which are connected to one another via data lines from signal and reference or ground lines. Only one transmitter may be active at any one time. Such bus systems are used, for example, in multiplex systems with a high transmission rate, ie also for the transmission of asymmetrical signals, for example pulse or digital signals. The transmission of unbalanced signals on a bus system is particularly susceptible to interference if it concerns signals with steep edges, for example when using electronic components of the digital Schottky TTL series. Interference signals are caused during the transmission by interference signal currents if they generate a voltage drop at the supply lines and feed points of transmitters and receivers. These interference signals are particularly strong when the bus system is a synchronous system in which several electronic assemblies are switched over to a clock pulse edge and supply capacities are reloaded. Clock pulse lines and asynchronous set and reset lines are particularly at risk of interference. The ^'spurious signals sen in the form of Nadelimpul¬ or spikes occur can reach amplitudes in the order of one to two volts, thus levels which may significantly interfere with such a bus system with larger bus systems, for example, from ten boards.

Disturbances on unbalanced lines of a bus system can be avoided by using coaxial cables Suppress the suppression if you ground the outer conductor of both the transmitter and the receiver. However, in high-speed systems, these cables require their own line drivers with relatively complicated driver circuits that consume additional power. In addition, these cables are expensive and relatively difficult to process.

The object of the invention is to achieve interference immunity in transmission systems of the type in question with simple measures.

This object is achieved according to the invention by the features specified in the characterizing part of patent claim 1. Accordingly, in the bus system, a transformer with a relatively high, one-way coupling factor is switched in each connection path between transmitter and receiver. If an interference voltage can be measured between the transmitter and receiver reference, then a voltage U_ with respect to the receiver references ^, which is composed of the transmitter signal U _ς and the interference voltage, is measured at the receiver input. If the ground points of the transmitter reference and receiver reference are connected to the primary side of a 1: 1 transformer, and if the secondary side is connected to the signal line, the interference component is reduced by the injected value, ie by the factor (1-k) , where k is the coupling factor of the transformer. If a transformer is used with a high degree of coupling, for example better than 0.9, the interference is reduced to 10% of the original value. It is possible to switch on an unloaded 1: 1 transformer between the transmitter and the receiver because the receivers generally have a high input impedance of the order of a few kilohms. The reason that the transmission signal is not influenced is that the transformer acts as short-circuited for the transmission signal, specifically via the interference Voltage U _N , and thus no voltage drop in the signal line along the secondary side. It is important that the degree of coupling of the transformer is chosen to be as high as possible, ie against one. In addition, the coupling factors of all 1: 1 transformers used in the bus system should be as equal as possible.

The invention enables simple, but very effective suppression of interference signals generated internally in the circuit. The invention is advantageously applicable to fast asymmetrical bus systems. The invention eliminates the need for expensive wiring with coaxial cables, rather it is sufficient to simply twist the line pairs within the transmission system. Instead of expensive active cable drivers with correspondingly complicated circuits, inexpensive, passive 1: 1 transformers, e.g. Ferrite transformers used. In addition, normal components such as gates, flip-flops etc. can be used as drivers in the transmission systems according to the invention without special adaptation to the bus system.

Further embodiments of the invention emerge from the subclaims.

The invention is explained in more detail in two exemplary embodiments with reference to the drawing. In the drawing:

Figure 1 is a schematic representation of a transmission system according to the invention with several

Transmitters and receivers;

FIG. 2 shows a further transmission system according to the invention; FIG. 3 shows an equivalent circuit diagram of a transmitter / receiver circuit to explain the invention.

FIG. 3 shows a transmission system 1 with a transmitter 2 and a receiver 3, which are connected to one another via a data line 4. The data line 4 is a line pair of a signal line 4s and a reference line 4r. A primary winding 5 of a 1: 1 transformer 6 is connected in the reference line 4r between the ground points of the transmitter reference Ref-S and the receiver reference Ref-E. The secondary winding 7 of the transformer 6 lies in the signal line 4s.

The transmitter 2 transmits a transmission signal U corresponding to the voltage between the signal and reference line. The receiver 3 receives a received signal U. In this case, it is assumed that an interference signal U is additionally fed in at the reference reference Ref-S. This interference signal is transmitted from the primary side of the transformer to the secondary side in accordance with the coupling factor k of the transformer. The following then applies to the received signal U_:

u _E = u _{s +} (1 - k) U _N (1)

If the coupling factor k of the transformer is 0.9, for example, the interference is reduced to 10% of the original value. The transmission signal U is practically not influenced, since for this signal the transformer acts as short-circuited via the generator U _N shown in the equivalent circuit diagram in FIG. 3.

FIG. 1 shows a transmission or bus system 1 ′ with a plurality of transmitters 2 ′ and a plurality of receivers 3 ″, which are connected to one another via a main data line 4 ¹ comprising a signal line 4 ′ and a reference line 4 ′ r. Two transmitters 2'-1, 2 * -2 and two receivers 3'-1, 3'-2 are shown for the transmission system. The arrangement of transmitters and receivers is exemplary.

The transmitter references Ref-Sl, Ref-S2 and receiver references Ref-El, Ref-E2 are shown for the transmitters and receivers. Between the two transmitters, the second transmitter and the first receiver and between the two Empfän¬ like is in the data main line 4 ¹ each represent a l: l-6 Trans- turned on 'in the manner described above. Accordingly, at least one transformer is located in any transmission path between one of the transmitters and one of the receivers, so that any interference signals corresponding to the coupling factor of the transformer are suppressed on this transmission path. Accordingly, three transformers 6 'are located in the transmission path between the first transmitter _? - 1 and the second receiver 3-2 in the diagram according to FIG. Assuming that interference signals are generated at the reference point of the first transmitter or at other reference points of other transmitters, the receiver 3 '-2 receives the undamped transmission signal and additive interference components. These interference components are the original interference signals which are multiplicatively damped by the factors (1-ki) or (kj-km); i, j and m are the numbers of the transformers in the signal path. It can be seen that good interference suppression is achieved if all the coupling factors are as equal as possible, ie if the difference between ki and kj is small or even zero, and if all the transformers are also firmly coupled, ie the coupling factor is as close as possible to one.

FIG. 2 shows a further exemplary embodiment of a bus system 1 ". While in the transmission system 1 'according to FIG. 1, the transformers 6' are in series in of the main data line 4 ', in the exemplary embodiment according to FIG. 2 the 1: 1 transformers 6 "are arranged in line sections 8" which are each located between the transmitter 2 "or receiver 3" and the main data line 4 " Arrangement of the transformers in this way can therefore be referred to as a parallel arrangement. The transmission signal transmitted by any transmitter and received by any receiver thus always passes through the secondary windings of two 1: 1 transformers no transformers arranged themselves. To the ^{'interference} heights to er¬, the signal line 4' s and the reference line 4 "r twisted together. The transformer windings should be run from the same ^'reason bifilar and possible comparable drills.

Claims

Transmission system patent claims

1. Transmission system with at least one transmitter and one receiver, which are connected to one another via data lines from signal and 3 reference or ground lines (bus system), only one transmitter being allowed to be active at any time, characterized thereby that at least one primary winding (5) of a 1: 1 transformer (6) is connected between any transmitter (2) and receiver (3) in the associated signal connection path ö along the data line (4) in the reference line (4r) that the secondary winding (7) of the transformer (6) is arranged in the associated section of the signal line (4s) and that the coupling factors (k) of the transformers (6) are as large as possible.

2. Transmission system according to claim 1, characterized in that the coupling factors (k) of all transformers (6) in the transmission system (1) are as identical as possible.

3. Transmission system according to claim 1 or 2, characterized ge indicates that the transformers (6 ') in the 5 common data line (4') are connected. 1 4. Transmission system according to claim 1 or 2, characterized ge indicates that each transmitter (2 ") and each receiver (3") is assigned a transformer (6 "), each in a common data main line (4th ")

1 leading line section (8 ") are arranged.

5. Transmission system according to one of the preceding claims, characterized in that the data line (4) from the signal and reference line (4s, 4r) is designed as a twisted pair of lines.

6. Transmission system according to one of the preceding claims, characterized in that the transformators (6) have bifilar and twisted windings " ^j (5, 7).

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