FR3040248A1 - ADJUSTING THE IMPEDANCE OF ACCESS COST OF CARRIER FREQUENCIES OF TELECOMMUNICATION EQUIPMENT BY CURRENT CARRIERS ONLINE - Google Patents

Abstract

Device for adjusting the access impedance of the carrier frequencies of a line carrier telecommunication equipment (1), characterized in that it comprises a means for measuring the module of the impedance of the line ( ZL) to which the equipment is intended to be connected, and means (20) for adjusting the access impedance (Za) of the equipment at the carrier frequencies, so that the module of the impedance of access is substantially equal to the measured module of the impedance of the line.

Description

ADJUSTING THE IMPEDANCE OF ACCESS COST OF CARRIER FREQUENCIES OF TELECOMMUNICATION EQUIPMENT BY CURRENT CARRIERS ONLINE

DESCRIPTION

TECHNICAL AREA

The present invention generally relates to the field of in-line carrier currents (CPL) which make it possible to constitute a telecommunications network on an electrical network.

It relates more specifically to the adjustment of the impedance of the access side of the carrier frequencies, that is to say on the carrier side, of a telecommunications equipment carrier line.

STATE OF THE PRIOR ART

In the following, we are more specifically interested in the CPL equipment that is intended to be connected to a high-voltage line, and to the access of these equipments on power lines. The latest generation equipment using digital modulation.

Different types of modulations are usable. Some modulations, such as Orthogonal Frequency Division Multiplexing (OFDM), use two distinct frequency bands for one direction of data transmission and the other direction, respectively. Other modulations, such as Quadrature Amplitude Modulation (QAM), can use the same frequency band for both directions of data transmission. This is called the superimposed transmission mode.

The CPL devices are connected to the high-voltage line through a capacitor called a coupling capacitor, and a device called a coupling unit comprising protection devices and making it possible to achieve a coarse impedance matching between the line and equipment.

One of the main characteristics of power transmission systems is that it does not control the impedance of the support. This poses a particular problem when the line used is a high-voltage line of a transmission network. The impedance presented by the line and the coupling members can be very different from the nominal impedance of the access of the equipment. In addition, the impedance of the line varies over time, depending, in particular, on atmospheric conditions.

This mismatch of the impedance of the line with respect to the impedance of the equipment access impedes the transfer of energy from the transmitter to the line.

Currently, powerline telecommunication equipment in line has fixed access impedances that can be chosen by hardware configuration. The possible values of the impedance of access are generally to be chosen among the values 50Ω and 75Ω for an asymmetrical access or 120 Ω and 150Ω for a symmetric access. This configuration is usually done in the factory on customer specification.

During the commissioning of the PLC link, a rough adaptation of the access impedance of the transmission / reception equipment is performed thanks to the coupling group, without it being possible to know the degree of maladjustment. impedance of access. Under these conditions, the energy transfer of the CPL signal is generally not optimal.

In addition, when the equipment is put into service or when it is used, the constraints of the ground rarely allow a precise adjustment of its access impedance, because of the high-voltage electrical environment which makes it impossible to carry out the operations. measures under appropriate conditions.

DISCLOSURE OF THE INVENTION The invention aims to solve the problems of the prior art by providing a device for adjusting the access impedance on the carrier frequencies of an in-line carrier communication equipment, characterized in that 'it comprises

Means for measuring the module of the impedance of the line to which the equipment is intended to be connected, and

A means of adjusting the access impedance of the equipment side of the carrier frequencies, so that the module of the access impedance is substantially equal to the measured module of the impedance of the line.

To optimize the power transfer of the PLT signal, the impedance of the line and the impedance of access at the side of the carrier frequencies of the equipment should be equal at all times, or at least this equality is achieved at the time of commissioning. This perfect equality is not achievable because the impedance of the line is complex and in practice, it is not known how to accurately measure it during the commissioning of line power equipment. The invention makes it possible to equal the modules of the impedance of the line and of the access impedance of the equipment with a sufficient degree of accuracy.

Thanks to the invention, the adjustment of the access impedance on the side of the carrier frequencies of the equipment and therefore of the transfer of the transmitted signal is optimized when the PLC link is put into service, provided that a rough adjustment of the group coupling has been performed.

In addition, the proposed solution minimizes the equipment needed when commissioning the equipment.

According to a preferred characteristic, the module measuring means of the impedance of the line comprises:

Means for determining the value of a compensation impedance corresponding to a minimum of power of a transmission signal reinjected into the reception chain, and

A means for determining the value of the module of the impedance of the line as a function of the value of the determined compensation impedance.

These means are inexpensive in hardware and simple to use.

According to a preferred characteristic, the access impedance adjustment means comprises a plug-in transformer associated with controlled switches.

According to a preferred alternative to the preceding feature, the access impedance setting means comprises a tapped autotransformer associated with controlled switches.

It should be noted that in the context of the invention, various embodiments of controlled switches are possible, static relay, electromechanical relay, switching MOS transistor, for example.

These embodiments are simple to implement.

According to a preferred characteristic, the means for determining the value of a compensation impedance is adapted to determine another compensation impedance value corresponding to another minimum power of a transmission signal reinjected into the reception chain. after the access impedance setting means is configured to define an access impedance.

The determination of the compensation impedance can be repeated over time.

Thus, the transfer of energy is optimal at all times. The invention also relates to an in-line carrier communication equipment characterized in that it comprises a device for adjusting the access impedance side of the carrier frequencies as previously presented. The invention also relates to a method for adjusting the access impedance on the carrier frequencies of a carrier line telecommunication equipment, characterized in that it comprises steps of: measuring the module of the impedance of the line to which the equipment is to be connected, and adjustment of the access impedance of the equipment side of the carrier frequencies, so that the module of the access impedance is substantially equal to the module measured the impedance of the line. The equipment and process have advantages similar to those previously presented. The LC equipment according to the invention has an automatic adjustment device of the access impedance, adjustable from the on-board software of the equipment.

In a particular embodiment, the steps of the method according to the invention are implemented by computer program instructions.

Consequently, the invention also relates to a computer program on an information medium, this program being capable of being implemented in a computer, this program comprising instructions adapted to the implementation of the steps of a process as described above.

This program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in any other form desirable shape. The invention also relates to a computer readable information medium, and comprising computer program instructions suitable for implementing the steps of a method as described above.

The information carrier may be any entity or device capable of storing the program. For example, the medium may comprise storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or a magnetic recording means, for example a diskette or a hard disk. On the other hand, the information medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means. The program according to the invention can be downloaded in particular on an Internet type network.

Alternatively, the information carrier may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in carrying out the method according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Other characteristics and advantages will appear on reading the following description of a preferred embodiment, given by way of non-limiting example, described with reference to the figures in which:

FIG. 1 represents the high frequency part of a carrier line telecommunication equipment intended to be connected to a high-voltage line, according to one embodiment of the invention,

FIG. 2 represents a schematic example of frequency distribution of signals transmitted and received by an in-line carrier telecommunication equipment,

FIG. 3 represents a method for adjusting the access impedance on the carrier frequencies of an in-line carrier communication equipment according to one embodiment of the present invention,

FIG. 4 represents a circuit for adjusting the access impedance of the equipment, according to a first embodiment of the present invention,

FIG. 5 represents a circuit for adjusting the access impedance of the equipment, according to a second embodiment of the present invention, and

Fig. 6 shows a variable compensation impedance adjusting circuit according to an embodiment of the present invention.

According to a preferred embodiment and represented in FIG. 1, an in-line carrier communication equipment 1 is intended to be connected to a high-voltage line L.

Only the elements useful for understanding the invention are described below. The equipment 1 comprises for the data transmission part a digital-to-analog converter 10 for receiving data to be transmitted. The converter 10 forms an analog signal from the data it receives.

The output of the digital-to-analog converter 10 is connected to the input of a power amplifier 11. The converter 10 transmits the analog signal that it has formed to the power amplifier 11 whose purpose is to amplify the signal he receives.

The output of the power amplifier 11 is connected to the input of a transmission filter 12 which performs a bandpass filtering of the signal it receives. The filtered signal is thus in the transmission frequency band of the equipment. In addition, the transmit filter 12 has a fixed output impedance in the frequency band used.

The output of the transmission filter 12 is connected to the input of a two-wire / four-wire converter 13 whose function is to link the data transmission channel and the data reception chain to the line L.

The two-wire / four-wire converter 13 is an asymmetrical differential transformer, or hybrid transformer.

The output of the two-wire / four-wire converter 13 is connected to the input of a circuit 20 for adjusting the access impedance on the carrier frequencies. The circuit 20 makes it possible to determine an access impedance Za. The circuit 20 will be detailed later.

The output of the access impedance adjustment circuit 20 is connected to the input of a coupling unit 21 comprising protection devices and making it possible to carry out a coarse impedance matching between the line L and the equipment. 1.

The output of the coupling group 21 is connected to the line L via a coupling capacitor 22.

For the data receiving part, the equipment 1 comprises from the high voltage line L the coupling capacitor 22, the coupling group 21, the access impedance adjusting circuit 20 and the two-wire converter. four sons 13 that have just been presented.

The output of the two-wire / four-wire converter 13 is connected to the input of a reception filter 14 which performs a band-pass filtering of the reception signal. The filtered signal is thus in the receiving frequency band of the equipment.

The output of the reception filter 14 is connected to the input of an attenuator 15 which corrects the amplitude of the signal applied to it.

The output of the attenuator 15 is connected to the input of an analog / digital converter 16 to receive the reception signal after filtering and attenuation. The converter 16 extracts data from the analog signal it receives.

The two-wire / four-wire converter 13 is imperfect because part of the transmitted signal is fed back into the reception chain. The signal thus reinjected has a power level generally much higher than the signals coming from a remote device. The reinjected signal thus constitutes a disturbance in the reception chain, in particular if the transmit and receive frequency bands are merged.

To illustrate this, FIG. 2 represents a schematic example of frequency distribution of the signals in a case where the transmission and reception frequency bands are merged.

A transmitting carrier frequency Ctx and a receiving carrier frequency Crx are separated by a frequency band in which the modulated signals are located.

If the reception and transmission frequency bands are not confused, the implementation of the invention requires that the reception filter 14 cover all of the two frequency bands.

According to the present invention, the telecommunication equipment 1 comprises firstly a variable compensation impedance adjusting circuit 18 connected between the two-wire / four-wire converter 13 and the ground.

The variable compensation impedance adjusting circuit 18 has a resistive portion and a capacitive portion. More specifically, the circuit 18 comprises, for example, resistors switched by controlled switches, such as electromechanical or static relays and capacitors of different values, also switched by controlled switches, such as electromechanical or static relays. These elements are connected in series or in parallel by controlled switches, such as electromechanical or static relays. The controlled switches can also be made based on switching MOS transistor for example.

Alternatively, the circuit 18 further comprises at least one digital potentiometer.

In the second variant, the digital potentiometer of the circuit 18 is replaced by a photoresistor coupled to a light-emitting diode, this device making it possible to obtain a variable resistance.

In all cases, the circuit 18 makes it possible to define a compensation impedance Zc. An exemplary embodiment of a variable compensation impedance adjusting circuit 18 is described below.

According to the present invention, the telecommunication equipment 1 also comprises the circuit 20 for adjusting the access impedance Za, previously presented.

A control circuit 19 controls, on the one hand, the transmission and reception of data proper. The control circuit 19 is therefore connected to the digital-to-analog converter 10 and the analog-to-digital converter 16.

The control circuit 19 is also connected to the variable compensation impedance adjusting circuit 18 and to the access impedance adjusting circuit on the side of the carrier frequencies 20. The control circuit 19 thus controls the operation of the control circuit variable compensation impedance 18 and the access impedance adjustment circuit 20.

FIG. 3 shows the operation of the variable compensation impedance adjusting circuit 18 and the access impedance adjusting circuit 20, controlled by the control circuit 19, in the form of a flow chart comprising steps E at E4. Step E1 is an initialization which is carried out after powering on the equipment 1 and an adjustment of the gains made by an automatic earnings control system, conventional in itself and not described in the present application. The initialization comprises the transmission via the equipment 1 of a predetermined sinusoidal signal and the search for the minimum power of the reinjected signal.

The search for the minimum power of the reinjected signal is performed by varying the impedance Zc of the circuit 18 and measuring the power of the reinjected signal for each impedance value Zc tested.

Thus, the control circuit 19 imposes on the circuit 18 a given impedance value Zc. For this given impedance value, the signal present on the band of the reception filter, and more particularly the power of the transmitted signal, is measured. For this, the digital signal at the output of the analog / digital converter 16 is demodulated to bring it back to baseband. A narrow bandpass filter around the Ctx carrier is performed. Finally, the power level is determined by squaring followed by integration. These operations are performed by a microprocessor, a DSP or an FPGA.

A number of impedance values Zc are tested. Step E1 results in an initial value of the Zci compensation impedance which minimizes the power of the re-injected Tx carrier to a PCtxi value. The next step E2 is the determination of the line impedance ZL seen by the PLC equipment. This value is directly related to the modulus of the compensation impedance Zci by a linear relation of the type: I ZL | = oi | Zci | where a is a real coefficient dependent on the arrangement of the windings of the two-wire / four-wire converter 13. The next step E3 is the setting of the access impedance Za by the access impedance adjustment circuit 20, so that the module of the access impedance Za is as close as possible to the value of the line impedance module ZL calculated in step E2.

According to a first embodiment shown in FIG. 4, the access impedance adjustment circuit 20 comprises a tap-type transformer 201. The primary circuit of the transformer 201 is connected to the converter 13 and the secondary circuit of the transformer 201 is connected to the circuit 21.

The control circuit 19 is connected, through an isolation barrier 202, to controlled switches, for example relays Ru and R12 · The relay Ru is connected to an intermediate tap of the primary circuit of the transformer 201 and the relay R12 is connected to an end socket of the primary circuit of the transformer 201. Thus, the relays Ru and R12 are controlled by the control circuit 19 to configure the primary circuit of the transformer 201.

The control circuit 19 is also connected, through the isolation barrier 202, to controlled switches, for example relays R21 to R28. The relays R21 to R28 are respectively connected to intermediate sockets of the secondary of the transformer 201. , the relays R21 to R28 are controlled by the control circuit 19 to configure the secondary of the transformer 201. Of course, the number of relays is given as an example.

Control of the relays of the access impedance adjustment circuit 20 makes it possible to select an access impedance value Za from among a range of possible values, each possible value corresponding to a combination of positions of the relays Ru and R12, and R21 to R28 · The access impedance value Za is selected so that the access impedance module Za is as close as possible to the value of the line impedance module ZL.

According to a second embodiment shown in FIG. 5, the access impedance adjustment circuit 20 comprises a tap-take autotransformer 210 associated with an isolation transformer 211. The winding of the tap-changer autotransformer 202 is connected to the converter 13. It is also connected to the primary circuit of the isolation transformer 211 via controlled switches, for example relays R31 to R38. The secondary circuit of the isolating transformer 211 is connected to the circuit 21.

The control circuit 19 is connected to the relays R31 to R38. The relays R3i to R38 are respectively connected to intermediate sockets of the winding of the autotransformer 210. Thus, the relays R3i to R38 are controlled to configure the autotransformer 210. Of course, here again, the number of relays n ' is given as an example.

The control of the relays of the access impedance adjustment circuit 20 makes it possible to select an access impedance value Za from among a range of possible values, each possible value corresponding to a combination of positions of the relays R31 to R38. The access impedance value Za is selected so that the module of the access impedance Za is as close as possible to the value of the line impedance module ZL.

According to an embodiment shown in FIG. 6, the variable compensation impedance adjusting circuit 18 comprises capacitors Ci to C4 connected in parallel between the connection to the converter 13 and the ground. Each capacitor is further connected in series with a respective controlled switch, for example a relay R41, R42, R43 and R44, controlled by the control circuit 19 via the isolation barrier 202.

The variable compensation impedance adjusting circuit 18 also comprises resistors Ri to R4 and a digital potentiometer P connected in series between the connection to the converter 13 and the ground. Each resistor R2 to R4 is further connected in parallel with a respective controlled switch, for example a relay R45, R46 and R47, controlled by the control circuit 19 via the isolation barrier 202.

The digital potentiometer P is controlled by the control circuit 19 via the isolation barrier 202.

Resistances Ri to R4 switched by relay allow a rough adjustment of resistance. The digital potentiometer P has a large number of adjustment steps, for example 4096, and allows a fine adjustment of the resistance. Thus the circuit 18 allows fine resistance adjustment over a wide range of values.

Referring back to FIG. 3, step E3 may be followed by an optional step E4 of recalculating the value of the compensation impedance Zci. This step is similar to step El previously described. The value of the compensation impedance Zci which is calculated takes into account the value of the access impedance Za fixed by the circuit 20.

The compensation impedance values Zci and access impedance Za are then used for a phase of initialization and synchronization of the communication. This phase is conventional and known to those skilled in the art. It will not be described here.

Once this phase of initialization and synchronization of the communication is finished, communication is established with these values.

The access impedance setting described above can be restarted over time to ensure optimal energy transfer at all times. Thus, it is possible to adjust the access impedance periodically, for example every minute, or when the measured value of the power of the reinjected signal comes out of a range of predefined values.

Claims (9)

1. Device for adjusting the access impedance on the carrier frequencies of an in-line carrier communication equipment (1), characterized in that it comprises a means for measuring the module of the impedance of the line (ZL) to which the equipment is to be connected, and means (20) for adjusting the access impedance (Za) of the equipment side of the carrier frequencies, so that the module of the access impedance is substantially equal to the measured module of the impedance of the line. 2. Device for adjusting the access impedance on the carrier frequencies of an in-line carrier communication equipment according to claim 1, characterized in that the means for measuring the module of the impedance of the line comprises : Means (18) for determining the value of a compensation impedance (Zc) corresponding to a minimum of power of a transmission signal fed back into the reception chain, and means (19) for determining the value of the impedance module of the line as a function of the value of the determined compensation impedance. 3. Device for adjusting the access impedance on the carrier frequencies of an in-line carrier communication equipment according to claim 1 or 2, characterized in that the means (20) for adjusting the impedance of access (Za) comprises a plug-in transformer (201) associated with controlled switches. 4. Device for adjusting the access impedance on the carrier frequencies of a line carrier communication equipment according to claim 1 or 2, characterized in that the means (20) for adjusting the impedance of access (Za) comprises a plug-in autotransformer (210) associated with controlled switches. 5. Device for adjusting the access impedance on the carrier frequencies of an in-line carrier communication equipment according to claim 2, characterized in that the means (18) for determining the value of an impedance compensation circuit (Zc) is adapted to determine another compensation impedance value corresponding to another power minimum of a transmission signal reinjected into the reception chain, after the access impedance setting means configured to define an access impedance. 6. Equipment (1) for carrier communication in line characterized in that it comprises a device for adjusting the access impedance side of the carrier frequencies according to any one of claims 1 to 5. 7. A method for adjusting the access impedance on the carrier frequencies of a carrier line telecommunication equipment, characterized in that it comprises steps of: measuring (E1, E2) of the module of the impedance of the line to which the equipment is to be connected, and - setting (E3) of the equipment access impedance (Za) on the carrier side, so that the impedance module of access is substantially equal to the measured module of the impedance of the line. A computer program comprising instructions for performing the steps of the method of claim 7 when said program is executed by a computer. 9. A computer-readable recording medium on which is recorded a computer program comprising instructions for performing the steps of the method according to claim 7.