RU2419969C2 - Method to reduce crosstalk in four-wire electric data transfer lines - Google Patents

Abstract

FIELD: information technologies.

SUBSTANCE: groups of copper strand pairs are used so that data is sent along data transfer lines accordingly from two transmitting devices and two receiving ones, the input and output of the four-wire communication line are connected to a single-type device, which comprises the following components: a transformer, on each of two cores of which there is an input winding, the first and the second output windings. Besides, the first output windings of cores are connected in series, the second output windings of cores are connected oppositely, and reactive resistances of the input windings are equal and are twice more than the reactive resistances of the output windings.

EFFECT: reduced crosstalk in any electric transfer lines.

2 cl, 1 dwg

Description

The present solution, in General, relates to methods with improved performance and, in particular, designed to transmit data having internal shielding to reduce crosstalk.

The prior art device for determining single-phase earth faults in air networks with isolated neutral (patent RU 2255404), comprising a voltage transformer, a phase comparison unit for each protected connection, an Executive unit connected to the output of the phase comparison unit, a zero sequence current transformer for installation in a cell with an air outlet, including measuring current transformers, bushing insulators and a high-voltage switch, characterized in that the input pre a browser and a control unit, the inputs of the input converter being connected to the terminals of the secondary winding of the voltage transformer, and the output connected to the first input of each phase comparison unit and to the input of the control unit, the first and second outputs of which are connected respectively to the second and third inputs of the phase comparison units, the third the output of the control unit is connected to the control input of the executive unit, and cable transformers installed in the cable are used as zero-sequence current transformers I am waiting for a cell with an air outlet using a special design of three flexible wires in isolation, the terminals of the secondary windings of which are connected to the fourth inputs of the corresponding phase comparison units, and the primary winding of the zero-sequence current transformer is formed by wires of phases A, B, C, drawn through the core window, some ends of which are connected to the contacts of the high-voltage circuit-breaker of the cell with an air outlet, and the other ends are connected to the corresponding bushing insulators: in phase B directly, and in phase A and C - through measuring current transformers.

The solution is intended only for signaling and protection in three-phase circuits, but not for data transmission.

In the prior art, a SCREENED CONNECTOR FOR DATA TRANSFER is known (patent RU 2313179). The invention relates to an electrical connector, in particular to a data plug with internal shielding to reduce crosstalk and intended for use with a cable having multiple wires arranged in multiple pairs. The plug comprises a housing and a loading bar mounted inside the housing. In the boot bar set the wires in a certain position relative to each other. A shielding element is also installed in the housing, which is electrically conductive and shields the first pair of wires, the second pair of wires, the third pair of wires and the fourth pair of wires. A first recess is made in the shielding element, having dimensions that allow monitoring the level of crosstalk between the first pair of wires and the second pair of wires. The technical result is an increase in data transfer rate.

This solution allows to reduce crosstalk only at the near (transmitting) end (PPBK, NEXT).

From patent US 5970088, for example, a compensation method is known for a pool of N identical logical modems for digital subscriber lines of the MDSL type. It serves to compensate for crosstalk at the near end (PPBC). Modem transmitters are synchronized via a clock. The signals received by N modems after reception are freed from interference using a compensation circuit. The compensation circuit consists of N subunits, each of which is associated with a corresponding modem. The subunit includes N adaptive filters, the output signal of which serves to correct a signal that has already been received by the modem and converted to digital form. As a reference signal for adaptive filters, there is a transmission signal transmitted by the corresponding one of the N modems. The output signals of all adaptive filters of the subunit are combined and used to correct an already received signal.

The compensation method described in this solution requires N identical modems and N adaptive filters and only for digital subscriber lines such as MDSL and therefore is not suitable for suppressing interference in any system.

The closest analogue is a DEVICE FOR INCREASING THE CAPACITY OF A GROUP OF ELECTRIC DATA TRANSMISSION LINES AND A SYSTEM FOR DATA TRANSMISSION (patent RU 2313179), in particular a group of copper pairs of conductors, by suppressing crosstalk, the data being transmitted from one or more data lines, respectively transmitting devices, comprising an electronic circuit connected between two terminals, the electronic circuit comprising at least one adaptive filter that generates an output signal to correct the signal transmitted along the first data line, the reference signal for the adaptive filter is at least one signal and / or an external signal output from the second transmission line, and the error signal for the adaptive filter is the corrected signal transmitted through the first data line, while one terminal is used to connect to the external group of the above data lines, and the other terminal is used to connect to the other external group of the above lines data or to one or more transmitting devices.

In this solution, the effect of crosstalk in the analogs was reduced by suppressing interference between the lines. To this end, the device contains adaptive filters, which suppresses interference in the signal transmitted along the transmission lines.

Disadvantages: 1) to suppress crosstalk, an a priori knowledge of the characteristics of the undistorted transmitted signal is required (which is not always possible), since adaptive filters to reduce or compensate for noise of an unknown nature in the transmission line generate a compensation signal, which is formed by subtracting the undistorted signal from the received signal; 2) for the formation of the reference signal requires an additional (idle) transmission line; 3) an antenna is required to form the reference signal; 3) suppression of crosstalk in twisted cable cores is preferably carried out within only one star-shaped four or main group; 4) the use of adaptive filters complicates transmission systems; 5) the appearance of crosstalk is always accompanied by a loss of energy of the transmitted signals, and their suppression - by an additional loss of energy; 6) is suitable for suppressing interference only in digital electric transmission lines.

The aim of the invention is to eliminate the disadvantages inherent in the prototype.

Effect: provides increased signal stealth; to suppress crosstalk, a priori knowledge of the characteristics of the undistorted transmitted signal is not required; no reference signal is needed, therefore an additional (idle) transmission line is not required; an antenna is not required to form a reference signal; the ability to reduce crosstalk in any electrical transmission lines.

The claimed technical result is achieved due to the fact that the method of reducing crosstalk in four-wire electrical data lines, characterized by the use of a group of copper pairs of wires so that data is transmitted on the above data lines, respectively, from two transmitting devices and two receiving, characterized in that the input and the output of the four-wire communication line is connected to the same device, which contains:

a transformer, on each of the two cores of which the input winding is located, the first and second output windings, the first output windings of the cores being connected in series, the second output windings of the cores turned on in the opposite direction, and the reactance of the input windings being equal to and twice the reactance of the output windings, input and output reactances of the same type of devices are made equal to each other;

sources and / or signal receivers are connected to the transformer through the input windings, the first twisted pair is connected in series to the output windings, and the second twisted pair is connected to the output windings turned on, and one wire of each pair is grounded;

when signals arrive at the transformer inputs on the output windings, the total and difference signals corresponding to the “even” and “odd” type of modes are formed, which are then transmitted via twisted pairs to the outputs of another transformer.

In addition, the transformer cores are made of ferromagnetic materials.

For electric (copper) cables based on two twisted pairs of wires, the transformer contains (see transformer diagram for electric (copper) cables based on two twisted pairs of wires in the drawing) two cores made of ferromagnetic materials, each of which contains, respectively, input windings 1 and 2, two output windings 3, 4 and 5, 6, output windings 3, 6 of the core included in the opposite direction, output windings 4, 5 are connected in series, and the reactance of the input windings 1, 2 is equal to and twice as reactivethe resistance of the output windings 3, 4, 5, 6. The input and output reactance of the transformer is chosen equal to each other. Sources and / or signal receivers are connected to the transformer through the input windings 1 and 2, and one twisted pair is connected to the output windings 3, 6, and another twisted pair is connected to the output windings 4, 5. In the drawing, 7 is a four-wire communication line, 8 is the signal source / receiver. The claimed solution does not use suppression or compensation, which require the consumption of additional energy, the complexity of circuit decisions, the introduction of active elements. Signal transmission is carried out on different types (modes) of transverse (TEM waves) electromagnetic waves arising in an N-wire system. The property of electromagnetic waves is used to propagate along the conductors, generating an electric current in them. This follows from Maxwell's equations. It follows from them that in the N-wire system there are N-1 types (modes) of transverse electromagnetic waves that excite coupled currents in these conductors. Each type (mode) of electromagnetic waves excites its own combination of coupled currents. In each conductor, the current is the sum of the connected currents. Therefore, if a specified combination of amplitudes and phases of coupled currents is called in the conductors, then the specified type (mode) of transverse electromagnetic waves is excited. Moreover, these modes do not exchange energy, do not interact with each other.

When a signal from one source enters the transformer, the signal excites only one type of mode in four-wire electrical data lines. At the output of four-wire electrical data lines, a transformer converts the electromagnetic waves of this mode into a signal from one receiver, there will be no signal from another receiver.

In four-wire electrical data transmission lines, two types of electromagnetic waves can be excited - “even” and “odd”, differing from each other only in the directions of the currents excited by them in the conductors due to the symmetry of the design of such lines. The third type of electromagnetic waves is suppressed by grounding one conductor of each pair. The “even” type of waves gives rise in two conductors to the movement of currents in one direction. The “odd” type of waves gives rise to countercurrent currents in these conductors. But the amplitudes of these currents will be the same, since all the conductors in the four-wire electrical data lines are the same.

At the input, a transformer and a four-wire electrical data line are connected in series. The signal arriving at the first input of the transformer causes one direction of currents at two outputs, which excites only the “even” type of mode in the connected four-wire electrical data line. The signal arriving at the second input of the transformer causes the opposite direction of the currents at the two outputs, which excites only the “odd” type of mode in the connected four-wire electrical data line. As a result, two types of modes that do not interact with each other propagate in a four-wire electrical data line.

At the output, a four-wire electrical data line and a transformer are turned on in counter. The signals of the 1st and 2nd twisted pair in the transformer at the 1st input are summed up and the "even" type of mode is converted by the transformer into the signal of the 1st input, and at the 2nd input there will be no signal. The signals of the 1st and 2nd twisted pair in the transformer at the 2nd input are subtracted and the "odd" type of mode the transformer converts to the signal of the 2nd input, and at the 1st input there will be no signal.

The present invention addresses the case of transmission over a 4-wire transmission line such as two twisted pairs. If the number of twisted pairs is 3, 4, 5 ... or if you consider asymmetric multi-wire transmission lines, then the connection and the output windings themselves will be different (other transformation ratios for current and voltage are needed). This is quite difficult technically feasible and therefore is not considered in this application.

In multiply connected systems, in particular in multi-wire communication lines, many types of electromagnetic waves are excited. But only TEM waves (transverse) can propagate (transfer energy). But due to the fact that they are not completely “flat”, they are called quasi-T-waves. Different types of T-waves occur in multi-wire communication lines when transmitting signals even on one line. This is due to the existence of a distributed electrical and magnetic connection between the lines. This fact is well known (see, for example, [4]).

It was shown in [1] that in multi-wire communication lines (cables), coupled types of transverse electromagnetic waves (modes) propagate, which can be called quasi-T waves (quasi-TEN waves). These modes are simultaneously excited at one end of the lines and propagate, passing (induced) from one line to another. In [2], the excitation conditions of each type of mode are shown.

These modes do not interact with each other. Therefore, the transmission of signals on connected types of waves in multi-wire lines will significantly reduce crosstalk and loss. In [3], the theoretical possibility of signal transmission on each type of mode is given. To transmit signals on related types of modes, signal sources and receivers are connected to multi-wire communication lines through transformers.

In [1], it was proved that in multi-wire lines, energy is transferred by different (called “coupled”) types of electromagnetic waves (modes), theoretical and experimental results are presented that confirm this. In the general case, the propagation velocity and the ratio between the electric and magnetic components (wave impedance) are different for different types of waves. Also in [1], expressions were obtained for calculating the elements of the transmission matrix [a] of multi-wire lines connecting the input and output currents and voltages in these lines.

It was shown in [2, 3] that the total incident power along the multi-wire line does not change and remains constant, but the total power oscillates (oscillates) during propagation, flowing from one line to another and vice versa. This is because the signal energy is distributed between the modes, and the propagation path of each mode has its own. The mode propagation paths, the length of the oscillation period are determined by the linear parameters of the multi-wire lines and the excitation conditions (this is determined by the ratio between the voltages at the line inputs).

Mods do not interact with each other. This is explained as follows. It was shown in [2, 3] that the transmission matrix [a] of multi-wire lines describes the cascade connection of terminal (terminal) transformers and unconnected long lines. Each such long line spreads its own type of waves (its own mode), and transformers convert the input and output currents and voltages into the connected currents and voltages of these modes. In fact, each long line is the way this mode spreads. This path may not coincide with the geometric path.

If two terminal transformers described by transfer matrices [a] _T and [a] _T ^{-1 are} connected in series, respectively, then the transmission coefficient of this system by voltage and current will be 1, the input voltage and current will be equal to the output voltage and current (operation of one transformer compensated for another) (see, for example, [3]).

For electric (copper) cables based on two twisted pairs of wires, the elements of the transfer matrices [a] _{T of the} terminal transformer are written as follows, [2]:

To transmit signals on related types of modes, signal sources and receivers should be connected to multi-wire communication lines through terminal transformers. Then, if the input and output of the multi-wire line are loaded with terminal transformers connected in the opposite direction, which compensate for the electrical and magnetic coupling between them, then the input and output of the multi-wire line will be connected directly by unconnected long lines.

Signal transmission on coupled wave types in multi-wire lines will significantly reduce crosstalk. This is explained by the following. In multi-wire communication lines, crosstalk increases with increasing line lengths. So, cables like UTP-3, DTP-5 are not used, as a rule, at distances of more than 100 m. If the input and output of such multi-wire lines are connected by unconnected lines, we exclude crosstalk at any length.

In the claimed invention uses a line containing four identical wires (two connected lines, cable type UTP-3).

Consider two twisted pairs of wires (for example, a UTP-3 cable). This is a symmetrical cable with four conductors, in which the linear parameters of all wires are the same. If one wire of each pair is grounded, then according to (1) in any section (including at the ends of the lines) the voltage U ₁ in the first line is equal to the sum of the modes “even” U _e and “odd” U _o , and voltage U ₂ in the second line is equal to the difference of these modes, respectively:

It follows from (1) that

Therefore, the “even” mode is equal to the sum of the line voltages at the input, and the “odd” mode is equal to the difference of these voltages. The currents of these voltages are associated with voltages through wave resistances, also “even” and “odd”:

Therefore, it is convenient to use transformers for voltage conversion.

Ferromagnetic cores are needed for magnetic coupling between the input and output windings in the high frequency region. Two cores are needed to eliminate the coupling between inputs 1 and 2 (see drawing) in magnetic flux.

The sequential inclusion of output windings 4 and 5 allows you to excite the "even" type of mode in the lines according to (3).

The counter inclusion of windings 3 and 6 makes it possible to excite the “odd” type of mode in the lines according to (4).

The reactance of the input windings 1, 2 is made equal because the linear parameters of all wires are the same [1, 2, 3]. The reactance of the inputs is twice as large as the output windings to ensure relations (3) and (4).

The composition of the device at the input of the four-wire transmission line: transformers with cores, their number is equal to the number of inputs; the cores are not necessarily ferrite, but they are preferable for transmitting high-frequency signals; the number of input windings is equal to the number of inputs; the number of output windings of each core is equal to the number of modes; conductors (transmission lines between which we reduce spurious connection), their number is equal to twice the number of inputs, because every second wire is reverse or ground. To reduce spurious connections, it is necessary to include at the input and output of the transmission line two identical devices implemented by the invention, connected in series and in the opposite direction. As a result, the invention can be used to increase stealth, as Signals are transmitted simultaneously on all transmission lines, and it is quite difficult to isolate any one signal if the number of conductors is large (tens, hundreds).

In the device for suppressing crosstalk, a priori knowledge of the characteristics of the undistorted transmitted signal is not required, and an additional (idle) transmission line is not required to form the reference signal. To generate a reference signal in the claimed device does not require an antenna.

As a consequence of the foregoing, the device is suitable for reducing crosstalk in any electrical transmission lines.

The principle of the method is as follows.

A four-wire communication line is connected to two transmitters and two receivers via transformers. When signals are received at the inputs 1 and 2 of the transformer, windings 4, 5 and 3, 6 produce a total and difference signal corresponding to the “even” and “odd” type of modes, which are then transmitted through twisted pairs 1 and 2. Other ends of these twisted pairs connected to the output of the same transformer. Signals from twisted pairs 1 and 2 go to the output windings 5, 6 and 3, 4, are added and subtracted, and go to inputs 1 and 2. Thanks to the double summation and double subtraction of the signals, signal distortions due to the influence of crosstalk are eliminated.

Information sources

1. Vorobyov P.A., Malyutin N.D., Fedorov V.N. Quasi-T-waves in devices on coupled strip lines with unbalanced electromagnetic coupling // Radio Engineering and Electronics, 1982. V.27. N 9. S.1711-1718.

2. Fedorov V.N. The study of wave processes in coupled strip lines and the development on their basis of high-speed attenuators and dynamic correctors: Dis. Cand. tech. sciences. Tomsk: TUSUR, 1999, 172 p.

3. Fedorov V.N. Bound Waves in Information and Telecommunication Systems / INTERMATIC - 2006 // Materials of the International Scientific and Technical Conference "Fundamental Problems of Radioelectronic Instrumentation", October 24-28, 2006, Moscow. - M .: MIREA, 2006, part 2. - p. 7-10.

4. Grigoriev A.D. Electrodynamics and microwave technology: Textbook. 2nd ed., Ext. - SPb .: Doe, 2007 .-- 704 p.

Claims (2)

1. A method of reducing crosstalk in four-wire electrical data lines, characterized by using a group of copper pairs of cores so that the data is transmitted through said data lines from two transmitting devices and two receiving, respectively, characterized in that the input and output of the four-wire communication line are connected to a device of the same type, which comprises: a transformer, on each of two cores of which an input winding is placed, a first and second output winding, the first output windings cores are connected in series, the second output windings of the cores are turned on in the opposite direction, and the reactance of the input windings is equal to and twice as large as the reactance of the output windings, the input and output reactances of the same devices being made equal to each other; sources and / or signal receivers are connected to the transformer through the input windings, the first twisted pair is connected to the output windings connected in series, and the second twisted pair is connected to the output windings connected in the opposite direction, and one wire of each pair is grounded; when signals arrive at the transformer inputs on the output windings, the total and difference signals corresponding to the “even” and “odd” type of modes are formed, which are then transmitted via twisted pairs to the outputs of another transformer. 2. A method of reducing crosstalk in four-wire electrical data lines according to claim 1, characterized in that the transformer cores are made of ferromagnetic materials.