WO1999039433A1 - Active impedance converter - Google Patents

Active impedance converter Download PDF

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Publication number
WO1999039433A1
WO1999039433A1 PCT/SE1999/000036 SE9900036W WO9939433A1 WO 1999039433 A1 WO1999039433 A1 WO 1999039433A1 SE 9900036 W SE9900036 W SE 9900036W WO 9939433 A1 WO9939433 A1 WO 9939433A1
Authority
WO
WIPO (PCT)
Prior art keywords
amplifier
resistor
impedance
subscriber line
signals
Prior art date
Application number
PCT/SE1999/000036
Other languages
French (fr)
Inventor
Mats Bladh
Original Assignee
Telefonaktiebolaget Lm Ericsson (Publ)
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Telefonaktiebolaget Lm Ericsson (Publ) filed Critical Telefonaktiebolaget Lm Ericsson (Publ)
Priority to AU23040/99A priority Critical patent/AU2304099A/en
Priority to AT0901399A priority patent/AT410384B/en
Publication of WO1999039433A1 publication Critical patent/WO1999039433A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M11/00—Telephonic communication systems specially adapted for combination with other electrical systems
    • H04M11/06—Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors
    • H04M11/062—Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors using different frequency bands for speech and other data
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H11/00—Networks using active elements
    • H03H11/02—Multiple-port networks
    • H03H11/40—Impedance converters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/12—Compensating for variations in line impedance
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
    • H04B1/40—Circuits
    • H04B1/54—Circuits using the same frequency for two directions of communication
    • H04B1/58—Hybrid arrangements, i.e. arrangements for transition from single-path two-direction transmission to single-direction transmission on each of two paths or vice versa
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0264—Arrangements for coupling to transmission lines
    • H04L25/0272—Arrangements for coupling to multiple lines, e.g. for differential transmission
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0264—Arrangements for coupling to transmission lines
    • H04L25/0298—Arrangement for terminating transmission lines

Definitions

  • the present invention relates to an active impedance converter circuit with a first side with complex impedance and a second side with complex/resistive impedance.
  • the present invention also relates to a splitter for splitting a subscriber line into a first transmission branch including a low pass filter for providing telephone service signal transmissions along said subscriber line and a second transmission branch including a high pass filter for attenuating said telephone service signals and for providing high rate digital data transmissions along said subscriber line.
  • the invention also relates to a termination of a twisted pair telephone transmission line for delivering two-way service including low frequency band telephone signals and high frequency band digital subscriber line signals.
  • the telephony signals are separated from the ADSL signals by means of a pair of splitters, one in the central office and one at the customer's premises.
  • the splitters provides the filtering required to separate the POTS and the ADSL bands before being input to their respective transceivers. Normally there is a low pass filter between the telephone and the line, and a high pass filter between the ADSL transceiver and the line.
  • the insulation generated by the splitter is important for power limiting and for the removal of transients.
  • POTS uses complex, i.e. capacitive impedances for termination and balance in the transmission bridges at telephone and central office.
  • the introduction of the ADSL technique into POTS will not be successful if it involves a reduced quality in the transmission of speech or if the digital signals are influenced by transients in the POTS.
  • the speech quality may be impaired by echo, sidetone or transmission loss.
  • the digital signals may be influenced by the low frequency POTS signalling voltages.
  • a passive inductance-capacitance filter within each respective passband has an almost entirely resistive impedance. This necessitates some form of impedance conversion, to meet demands from the operator that operational damping and reflection damping should be measured against a complex impedance.
  • the impedance for POTS signalling frequencies must be high for an unterminated filter. Usually, the impedance converter function of the impedance converters is 1 for this frequency, and therefore the impedance of the low pass filter must be high.
  • a splitter having an active impedance converter is described in "ADSL and VADSL Splitter Design and Telephony Performance", by John Cook and Phil Sheppard, IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 13, NO. 9, DECEMBER 1995.
  • This impedance converter is provided with an amplifier which has more gain for low frequencies than for high frequencies .
  • a high inductance transformer is needed which causes problems with a high leakage inductance for high frequencies .
  • a separate filter is needed for frequencies below 300 Hz in order to quench the 25 Hz POTS ringing signals, or the 50 or 60 Hz electric power supply transients.
  • the impedance for the filters will be too low so that the parallel capacitances will load ringing signals and impulsing for POTS excessively.
  • One object of the invention is therefore to provide a simple and efficient active impedance converter which reduces the above described problems.
  • an active impedance converter circuit with a first side with complex impedance and a second side with complex/resistive impedance, which circuit is characterized in an amplifier which is connected to said first side of the circuit, and which amplifier is adapted to provide low gain for low frequency signals and to change over to provide more gain for high frequency signals.
  • the amplifier comprises a capacitor, a first resistor, an operational amplifier and a second resistor.
  • the capacitor is connected in series with the first resistor and said first resistor is connected in series with the operational amplifier which is connected in parallel with the second resistor.
  • the capacitor acts as a block for direct current, and secondly it is dimensioned to function as a provider of reactance.
  • the amplifier is connected to a subscriber line via a transmission line bridge comprising three co-operating transformer inductor coils which are connected to said subscriber line for providing a balancing impedance.
  • This version of the invention is a simple and efficient means for providing balance damping as well as damping of longitudinal interferences.
  • the amplifier is complemented by an additional amplifier.
  • This version of the invention provides efficient means for driving the transformer inductor coils.
  • a preferred embodiment of the invention is used for separating ADSL signals from mixed ADSL and POTS signal transmissions along a twisted pair telephone transmission line.
  • the splitter comprises an active impedance converter circuit with a first side with complex impedance and a second side with complex/resistive impedance, and is characterized in that the impedance converter circuit comprises an amplifier which is connected to said first side of the circuit, and which amplifier is adapted to provide a low gain for low frequency signals and to change over to provide more gain for high frequency signals.
  • the termination in accordance with the invention comprises a splitter for splitting a subscriber line into a first transmission branch including a low pass filter for providing telephone service signal transmissions along said subscriber line and a second transmission branch including a high pass filter for attenuating said telephone service signals and for providing high rate digital data transmissions along said subscriber line, said splitter comprising an active impedance converter circuit with a first side with complex impedance and a second side with complex/resistive impedance.
  • the impedance converter circuit comprises an amplifier which is connected to said first side of the circuit, and which amplifier is adapted to provide a low gain for low frequency signals and to change over to providing more gain by means of high frequency signals.
  • Fig. 1 is a circuit diagram showing the active impedance converter circuit according to a first embodiment of the invention
  • Fig. 2 shows a graph of the input signal/frequency, associated with the impedance converter of Fig. 1,
  • Fig. 3 is a circuit diagram showing the active impedance converter circuit according to the second embodiment of the invention
  • Fig. 4 is a circuit diagram showing the active impedance converter according to the third embodiment of the invention.
  • Fig. 5 schematically illustrates a realized version of the impedance converter circuit of Fig. 4.
  • the active impedance converter circuit according to the present invention is included in the termination of a telephone subscriber line which presents both complex and resistive impedance.
  • the circuit may for example be used in an ADSL splitter where the line is specified as complex for low frequencies like POTS (0.3 - 3.4 kHz) and complex or resistive for ADSL frequencies (30 - 1100 kHz) as well as the associated high pass and low pass filters.
  • the circuit is designed for so called twisted pair telephone transmission lines for delivering two-way service.
  • the circuit diagram in Fig. 1 shows a theoretical model of a first unbalanced version of the impedance converter.
  • the telephone or the line is represented by an AC generator 10 where one of the generator outputs is connected to ground via two resistors 11 and 12 and a capacitor 13 in parallel with said resistor 12 which represents the specified complex impedance.
  • the other generator output is connected via a first branch of the circuit to one end of a first transformer inductor coil 14.
  • a second branch of the circuit is connected to an amplifier comprising a capacitor 15 which is connected in series with a resistor 16 to the inverting input of an operational amplifier 17. This side of the circuit with said two branches constitutes the complex net side of the circuit.
  • the other end of the coil 14 is connected to ground via a resistor 18.
  • This side of the circuit represents the resistive net side of the circuit, e.g. the high pass and the low pass filters.
  • the amplifier also comprises a resistor 19 which is connected in parallel with the operational amplifier 17, the output of which is connected via a resistor 20 to one end of a second transformer inductor coil 21.
  • the other end of the coil 21 is connected directly to ground.
  • the two transformer inductor coils 14 and 21 co-operate to form a 1:1 transformer.
  • R 2 +- j ⁇ C ⁇ where R x is the resistor 19, N is the transformer ratio 1:1, R 2 is the resistor 16 and C 7 is the capacitor 15.
  • R, +- l Jc C ⁇ ) Z IN has an equivalent impedance network built with one capacitor C s in serial with a resistor R s and both in parallel with a resistor R p .
  • Fig. 2 illustrates the amplitude of the IN-signal (V IN+ ) which is about 1 Volt from 0.3 kHz to 1100 kHz.
  • V IN+ the IN-signal
  • the IN-impedance is equal to the impedance of the generator 11-13. Because the load 18 is resistive the gain increases by frequency and the circuit characteristics is dimensioned so that the above described impedance converter acts as a controller by manipulating the voltage over the transformer 14, 21, so that the electric current in the loop becomes similar to the electric current for a complex termination in accordance with the generator impedance.
  • Fig. 3 illustrates a theoretical model of a second, balanced version of the impedance converter.
  • the same reference numbers have been used for similar components, as in the impedance converter in accordance with Fig. 1.
  • the telephone or the line is again represented by the AC generator 10.
  • the most significant difference lies in that a balancing impedance has been provided for the IN- signal by means of a third co-operating inductor coil 22 and the amplifier.
  • the IN+ voltage of the generator output is, as in Fig. 1, connected via the first branch of the circuit to the end of the first transformer inductor coil 1 .
  • the second branch of the circuit is connected to an amplifier comprising the capacitor 15a which is connected in series with the resistor 16a to the inverting input of the operational amplifier 17a.
  • the other end of the coil 14 is connected to OUT+ via the load resistor 18b.
  • the amplifier also comprises the resistor 19a which is connected in parallel with the operational amplifier 17a, the output of which is connected via the resistor 20 to one end of a second transformer inductor coil 21. The other end of the coil 21 is connected to ground.
  • the three transformer inductor coils 14, 21 and 22 co-operate to form a 2:1:1 transformer.
  • the IN- impedance 11-13 of the generator output is connected to one end of the balancing inductor coil 22.
  • the other end of the coil 22 is connected to OUT- and the load resistor 18a.
  • the IN- impedance of the generator 10 is also connected to the amplifier via a capacitor 15b and a resistor 16b to the non-inverting input of the operational amplifier 17.
  • a resistor 19b is connected in parallel with the operational amplifier 17.
  • Fig. 4 illustrates a theoretical model of a third, balanced version of the impedance converter.
  • the same reference numbers have been used for similar components, as in the impedance converter in accordance with Fig. 1 and 3.
  • the telephone or the line is again represented by the AC generator 10.
  • the most significant difference with reference to the previously described embodiment according to Fig. 3, lies in the addition of a second operational amplifier 17b.
  • the IN+ voltage of the generator output is, as in Fig. 3, connected via the first branch of the circuit to the end of the first transformer inductor coil 14.
  • the second branch of the circuit is connected to the first amplifier comprising the 10
  • the amplifier also comprises the resistor 19a which is connected in parallel with the operational amplifier 17a, the output of which is connected via the resistor 20 to one end of a second transformer inductor coil 21.
  • the other end of the coil 21 is connected to the output of the second operational amplifier 17b.
  • the three transformer inductor coils 14, 21 and 22 co-operate to form a 2:1:1 transformer.
  • the IN- impedance 11-13 of the generator output is connected to one end of the balancing inductor coil 22.
  • the other end of the coil 22 is connected to OUT- and the load resistor 18a.
  • the IN- impedance of the generator 10 is also connected to the second amplifier comprising the capacitor 15b which is connected in series with the resistor 16b to the inverting input of the second operational amplifier 17b.
  • a resistor 19b is connected in parallel with the second operational amplifier 17b.
  • Fig. 5 illustrates the realized version of the impedance converter circuit of Fig. 4.
  • the three transformer inductor coils 14, 21 and 22 co-operate to form a 1:1:1 transformer.

Abstract

The invention relates to an active impedance converter circuit with a first side with complex impedance and a second side with complex/resistive impedance. The impedance converter is provided with an amplifier (15, 16, 17, 19; 15a, 15b, 16a, 16b, 17a, 17b, 19) which input is connected to said first side of the circuit. The amplifier is adapted to provide low gain for low frequency signals and to change over to provide more gain for high frequency signals. The invention also relates to a splitter for splitting a subscriber line into a first transmission branch including a low pass filter and a second transmission branch including a high pass filter. The invention also comprises a termination of a twisted pair telephone transmission line for delivering two-way service including low frequency band telephone signals and high frequency band digital subscriber line signals.

Description

Title:
ACTIVE . IMPEDANCE CONVERTER
TECHNICAL FIELD
The present invention relates to an active impedance converter circuit with a first side with complex impedance and a second side with complex/resistive impedance. The present invention also relates to a splitter for splitting a subscriber line into a first transmission branch including a low pass filter for providing telephone service signal transmissions along said subscriber line and a second transmission branch including a high pass filter for attenuating said telephone service signals and for providing high rate digital data transmissions along said subscriber line. The invention also relates to a termination of a twisted pair telephone transmission line for delivering two-way service including low frequency band telephone signals and high frequency band digital subscriber line signals.
STATE OF THE ART
In the field of conventional twisted pair telephone transmission lines for delivering two-way service, there is a growing worldwide interest in providing high rate digital transmission over the copper access network (POTS) . This is due in part to the desire to take advantage of the large installation base that already exists, without the need to wait for the deployment of fibre lines in the access network. Examples of such systems include Asymmetric Digital Subscriber Line (ADSL) and a very high speed version (VADSL) . A vital part of this technology lies in its ability to simultaneously support secure telephony while delivering the broadband service. This facility obviates any need for extra copper pairs which would otherwise destroy the big advantage over fibre installation. To enable this, the telephony signals are separated from the ADSL signals by means of a pair of splitters, one in the central office and one at the customer's premises. Thus, the splitters provides the filtering required to separate the POTS and the ADSL bands before being input to their respective transceivers. Normally there is a low pass filter between the telephone and the line, and a high pass filter between the ADSL transceiver and the line. The insulation generated by the splitter is important for power limiting and for the removal of transients.
In many countries, POTS uses complex, i.e. capacitive impedances for termination and balance in the transmission bridges at telephone and central office. The introduction of the ADSL technique into POTS will not be successful if it involves a reduced quality in the transmission of speech or if the digital signals are influenced by transients in the POTS. For example, the speech quality may be impaired by echo, sidetone or transmission loss. On the other hand, the digital signals may be influenced by the low frequency POTS signalling voltages.
A passive inductance-capacitance filter within each respective passband has an almost entirely resistive impedance. This necessitates some form of impedance conversion, to meet demands from the operator that operational damping and reflection damping should be measured against a complex impedance. The impedance for POTS signalling frequencies must be high for an unterminated filter. Usually, the impedance converter function of the impedance converters is 1 for this frequency, and therefore the impedance of the low pass filter must be high.
A splitter having an active impedance converter is described in "ADSL and VADSL Splitter Design and Telephony Performance", by John Cook and Phil Sheppard, IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 13, NO. 9, DECEMBER 1995. This impedance converter is provided with an amplifier which has more gain for low frequencies than for high frequencies . As a consequence of this, a high inductance transformer is needed which causes problems with a high leakage inductance for high frequencies . A separate filter is needed for frequencies below 300 Hz in order to quench the 25 Hz POTS ringing signals, or the 50 or 60 Hz electric power supply transients. The impedance for the filters will be too low so that the parallel capacitances will load ringing signals and impulsing for POTS excessively.
SUMMARY OF THE INVENTION
One object of the invention is therefore to provide a simple and efficient active impedance converter which reduces the above described problems.
According to the invention, this is accomplished by means of an active impedance converter circuit with a first side with complex impedance and a second side with complex/resistive impedance, which circuit is characterized in an amplifier which is connected to said first side of the circuit, and which amplifier is adapted to provide low gain for low frequency signals and to change over to provide more gain for high frequency signals. In a particular embodiment of the invention, the amplifier comprises a capacitor, a first resistor, an operational amplifier and a second resistor.
According to another embodiment of the invention, the capacitor is connected in series with the first resistor and said first resistor is connected in series with the operational amplifier which is connected in parallel with the second resistor.
Preferably, first the capacitor acts as a block for direct current, and secondly it is dimensioned to function as a provider of reactance.
According to still another embodiment of the invention, the amplifier is connected to a subscriber line via a transmission line bridge comprising three co-operating transformer inductor coils which are connected to said subscriber line for providing a balancing impedance. This version of the invention is a simple and efficient means for providing balance damping as well as damping of longitudinal interferences.
Preferably, the amplifier is complemented by an additional amplifier. This version of the invention provides efficient means for driving the transformer inductor coils.
A preferred embodiment of the invention is used for separating ADSL signals from mixed ADSL and POTS signal transmissions along a twisted pair telephone transmission line.
The splitter according to the invention comprises an active impedance converter circuit with a first side with complex impedance and a second side with complex/resistive impedance, and is characterized in that the impedance converter circuit comprises an amplifier which is connected to said first side of the circuit, and which amplifier is adapted to provide a low gain for low frequency signals and to change over to provide more gain for high frequency signals.
The termination in accordance with the invention comprises a splitter for splitting a subscriber line into a first transmission branch including a low pass filter for providing telephone service signal transmissions along said subscriber line and a second transmission branch including a high pass filter for attenuating said telephone service signals and for providing high rate digital data transmissions along said subscriber line, said splitter comprising an active impedance converter circuit with a first side with complex impedance and a second side with complex/resistive impedance. This termination is characterized in that the impedance converter circuit comprises an amplifier which is connected to said first side of the circuit, and which amplifier is adapted to provide a low gain for low frequency signals and to change over to providing more gain by means of high frequency signals.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will in the following be further described in a non- limiting way with reference to the accompanying drawings in which: Fig. 1 is a circuit diagram showing the active impedance converter circuit according to a first embodiment of the invention, Fig. 2 shows a graph of the input signal/frequency, associated with the impedance converter of Fig. 1,
Fig. 3 is a circuit diagram showing the active impedance converter circuit according to the second embodiment of the invention, Fig. 4 is a circuit diagram showing the active impedance converter according to the third embodiment of the invention, and
Fig. 5 schematically illustrates a realized version of the impedance converter circuit of Fig. 4.
DESCRIPTION OF PREFERRED EMBODIMENTS The active impedance converter circuit according to the present invention is included in the termination of a telephone subscriber line which presents both complex and resistive impedance.
The circuit may for example be used in an ADSL splitter where the line is specified as complex for low frequencies like POTS (0.3 - 3.4 kHz) and complex or resistive for ADSL frequencies (30 - 1100 kHz) as well as the associated high pass and low pass filters. The circuit is designed for so called twisted pair telephone transmission lines for delivering two-way service.
The circuit diagram in Fig. 1 shows a theoretical model of a first unbalanced version of the impedance converter. At the left side of the diagram, the telephone or the line is represented by an AC generator 10 where one of the generator outputs is connected to ground via two resistors 11 and 12 and a capacitor 13 in parallel with said resistor 12 which represents the specified complex impedance. The other generator output is connected via a first branch of the circuit to one end of a first transformer inductor coil 14. A second branch of the circuit is connected to an amplifier comprising a capacitor 15 which is connected in series with a resistor 16 to the inverting input of an operational amplifier 17. This side of the circuit with said two branches constitutes the complex net side of the circuit.
The other end of the coil 14 is connected to ground via a resistor 18. This side of the circuit represents the resistive net side of the circuit, e.g. the high pass and the low pass filters.
The amplifier also comprises a resistor 19 which is connected in parallel with the operational amplifier 17, the output of which is connected via a resistor 20 to one end of a second transformer inductor coil 21. The other end of the coil 21 is connected directly to ground. The two transformer inductor coils 14 and 21 co-operate to form a 1:1 transformer.
R - N
The amplifier 15, 16, 17 and 19 provides a gain f = '
R2 +- jωCη where Rx is the resistor 19, N is the transformer ratio 1:1, R2 is the resistor 16 and C7 is the capacitor 15.
R
IN = - R,, + 12
1 + jωRv x Cv
R. - Η
Accordingly, the impedance Z ouτ+ 1 +
R, +- l Jc Cη ) ZIN has an equivalent impedance network built with one capacitor Cs in serial with a resistor Rs and both in parallel with a resistor Rp. This network with a serial network Cs has the same relationship between the component values, if N=l, as the invention feedback network Rx, R2, and C7.
Fig. 2 illustrates the amplitude of the IN-signal (VIN+) which is about 1 Volt from 0.3 kHz to 1100 kHz. Thus, the IN-impedance is equal to the impedance of the generator 11-13. Because the load 18 is resistive the gain increases by frequency and the circuit characteristics is dimensioned so that the above described impedance converter acts as a controller by manipulating the voltage over the transformer 14, 21, so that the electric current in the loop becomes similar to the electric current for a complex termination in accordance with the generator impedance.
Fig. 3 illustrates a theoretical model of a second, balanced version of the impedance converter. The same reference numbers have been used for similar components, as in the impedance converter in accordance with Fig. 1. At the left side of the diagram, the telephone or the line is again represented by the AC generator 10. The most significant difference lies in that a balancing impedance has been provided for the IN- signal by means of a third co-operating inductor coil 22 and the amplifier.
The IN+ voltage of the generator output is, as in Fig. 1, connected via the first branch of the circuit to the end of the first transformer inductor coil 1 . The second branch of the circuit is connected to an amplifier comprising the capacitor 15a which is connected in series with the resistor 16a to the inverting input of the operational amplifier 17a. The other end of the coil 14 is connected to OUT+ via the load resistor 18b.
The amplifier also comprises the resistor 19a which is connected in parallel with the operational amplifier 17a, the output of which is connected via the resistor 20 to one end of a second transformer inductor coil 21. The other end of the coil 21 is connected to ground. The three transformer inductor coils 14, 21 and 22 co-operate to form a 2:1:1 transformer.
The IN- impedance 11-13 of the generator output is connected to one end of the balancing inductor coil 22. The other end of the coil 22 is connected to OUT- and the load resistor 18a. The IN- impedance of the generator 10 is also connected to the amplifier via a capacitor 15b and a resistor 16b to the non-inverting input of the operational amplifier 17. A resistor 19b is connected in parallel with the operational amplifier 17.
Fig. 4 illustrates a theoretical model of a third, balanced version of the impedance converter. The same reference numbers have been used for similar components, as in the impedance converter in accordance with Fig. 1 and 3. At the left side of the diagram, the telephone or the line is again represented by the AC generator 10. The most significant difference with reference to the previously described embodiment according to Fig. 3, lies in the addition of a second operational amplifier 17b.
The IN+ voltage of the generator output is, as in Fig. 3, connected via the first branch of the circuit to the end of the first transformer inductor coil 14. The second branch of the circuit is connected to the first amplifier comprising the 10
capacitor 15a which is connected in series with the resistor 16a to the inverting input of the first operational amplifier 17a. The other end of the coil 14 is connected to OUT+ via the load resistor 18b.
The amplifier also comprises the resistor 19a which is connected in parallel with the operational amplifier 17a, the output of which is connected via the resistor 20 to one end of a second transformer inductor coil 21. The other end of the coil 21 is connected to the output of the second operational amplifier 17b. The three transformer inductor coils 14, 21 and 22 co-operate to form a 2:1:1 transformer.
The IN- impedance 11-13 of the generator output is connected to one end of the balancing inductor coil 22. The other end of the coil 22 is connected to OUT- and the load resistor 18a. The IN- impedance of the generator 10 is also connected to the second amplifier comprising the capacitor 15b which is connected in series with the resistor 16b to the inverting input of the second operational amplifier 17b. A resistor 19b is connected in parallel with the second operational amplifier 17b.
Fig. 5 illustrates the realized version of the impedance converter circuit of Fig. 4. The three transformer inductor coils 14, 21 and 22 co-operate to form a 1:1:1 transformer.
The invention is not limited to the above described embodiments, instead several modifications may be made within the scope of the invention.

Claims

11CLAIMS
1. An active impedance converter circuit with a first side with complex impedance and a second side with complex/resistive impedance , c h a r a c t e r i z e d in an amplifier (15, 16, 17, 19; 15a, 15b, 16a, 16b, 17a, 17b, 19) which is connected to said first side of the circuit, and which amplifier is adapted to provide low gain for low frequency signals and to change over to provide more gain for high frequency signals.
2. A circuit according to claim 1, c h a r a c t e r i z e d in that the amplifier comprises a capacitor (15; 15a, 15b), a first resistor (16; 16a, 16b), an operational amplifier (17; 17a, 17b) and a second resistor (19; 19a, 19b) .
3. A circuit according to claim 2, c h a r a c t e r i z e d in that the capacitor (15; 15a, 15b) is connected in series with the first resistor (16; 16a, 16b), and that said first resistor is connected in series with the operational amplifier (17; 17a, 17b) which is connected in parallel with the second resistor (19; 19a, 19b) .
4. A circuit according to claim 2 or 3 , c h a r a c t e r i z e d in that the capacitor (15; 15a, 15b) first acts as a block for direct current, and secondly it is dimensioned to function as a provider of reactance.
5. A circuit according to any one of claims 1 to 4 , 12
c h a r a c t e r i z e d in that the amplifier is connected to a subscriber line via a transmission line bridge comprising three co-operating transformer inductor coils (14, 21, 22) for providing balancing impedance to said subscriber line.
6. A circuit according to any one of claims 1 to 5, c h a r a c t e r i z e d in that the amplifier (15a, 16a, 17a, 19a) is complemented by an additional amplifier (15b, 16b, 17b, 19b) .
7. Use of a circuit according to any of the above claims for separating ADSL signals from mixed ADSL and POTS signal transmissions along a twisted pair telephone transmission line.
8. A splitter for splitting a subscriber line into a first transmission branch including a low pass filter (18; 18a, 18b) for providing telephone service signal transmissions along said subscriber line and a second transmission branch including a high pass filter (18; 18a, 18b) for attenuating said telephone service signals and for providing high rate digital data transmissions along said subscriber line, said splitter comprising an active impedance converter circuit with a first side with complex impedance and a second side with complex/resistive impedance, c h a r a c t e r i z e d in an amplifier (15, 16, 17, 19; 15a, 15b, 16a, 16b, 17a, 17b, 19) which is connected to said first side of the circuit, and which amplifier is adapted to provide low gain for low frequency signals and to change over to provide more gain for high frequency signals.
9. A splitter according to claim 8, 13
c h a r a c t e r i z e d in that the amplifier comprises a capacitor (15; 15a, 15b), a first resistor (16; 16a, 16b), an operational amplifier (17; 17a, 17b) and a second resistor (19; 19a, 19b) .
10. A splitter according to claim 9, c h a r a c t e r i z e d in that the capacitor (15; 15a, 15b) is connected in series with the first resistor (16; 16a, 16b), and that said first resistor is connected in series with the operational amplifier (17; 17a, 17b) which is connected in parallel with the second resistor (19; 19a, 19b) .
11. A splitter according to claim 9 or 10, c h a r a c t e r i z e d in that the capacitor (15; 15a, 15b) first acts as a block for direct current, and secondly it is dimensioned to function as a provider of reactance.
12. A splitter according to any one of claims 8 to 11, c h a r a c t e r i z e d in that the amplifier is connected to a subscriber line via a transmission line bridge comprising three co-operating transformer inductor coils (14, 21, 22) for providing balancing impedance to said subscriber line.
13. A splitter according to any one of claims 8 to 12, c h a r a c t e r i z e d in that the amplifier (15a, 16a, 17a, 19a) is complemented by an additional amplifier (15b, 16b, 17b, 19b) .
14. Use of a splitter according to any one of claims 8 to 12, for separating ADSL signals from mixed ADSL and POTS signal transmissions along a twisted pair telephone transmission line. 14
15. A termination of a twisted pair telephone transmission line for delivering two-way service including low frequency band telephone signals and high frequency band digital subscriber line signals, said termination comprising a splitter for splitting a subscriber line into a first transmission branch including a low pass filter (18; 18a, 18b) for providing telephone service signal transmissions along said subscriber line and a second transmission branch including a high pass filter (18; 18a, 18b) for attenuating said telephone service signals and for providing high rate digital data transmissions along said subscriber line, said splitter comprising an active impedance converter circuit with a first side with complex impedance and a second side with complex/resistive impedance , c h a r a c t e r i z e d in an amplifier (15, 16, 17, 19; 15a, 15b, 16a, 16b, 17a, 17b, 19) which is connected to said first side of the circuit, and which amplifier is adapted to provide low gain for low frequency signals and to change over to provide more gain for high frequency signals.
16. A termination according to claim 15, c h a r a c t e r i z e d in that the amplifier comprises a capacitor (15; 15a, 15b), a first resistor (16; 16a, 16b), an operational amplifier (17; 17a, 17b) and second resistor (19; 19a, 19b) .
17. A termination according to claim 16, c h a r a c t e r i z e d in that the capacitor (15; 15a, 15b) is connected in series with the first resistor (16; 16a, 16b), and that said first resistor is connected in series with the 15
operational amplifier (17; 17a, 17b) which is connected in parallel with the second resistor (19; 19a, 19b) .
18. A termination according to claim 16 or 17, c h a r a c t e r i z e d in that the capacitor (15; 15a, 15b) first acts as a block for direct current, and secondly it is dimensioned to function as a provider of reactance.
19. A termination according to any one of claims 15 to 18, c h a r a c t e r i z e d in that the amplifier is connected to a subscriber line via a transmission line bridge comprising three co-operating transformer inductor coils (14, 21, 22) for providing balancing impedance to said subscriber line.
20. A termination according to any one of claims 15 to 19, c h a r a c t e r i z e d in that the amplifier (15a, 16a, 17a, 19a) is complemented by an additional amplifier (15b, 16b, 17b, 19b) .
21. Use of a termination according to any one of claims 11 to 14, for separating ADSL signals from mixed ADSL and POTS signal transmissions along a twisted pair telephone transmission line.
PCT/SE1999/000036 1998-01-29 1999-01-14 Active impedance converter WO1999039433A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU23040/99A AU2304099A (en) 1998-01-29 1999-01-14 Active impedance converter
AT0901399A AT410384B (en) 1998-01-29 1999-01-14 ACTIVE IMPEDANCE CONVERTER CIRCUIT ARRANGEMENT / SPLITTER FILTER

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9800240-5 1998-01-29
SE9800240A SE511316C2 (en) 1998-01-29 1998-01-29 Active impedance converter

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WO1999039433A1 true WO1999039433A1 (en) 1999-08-05

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AU (1) AU2304099A (en)
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WO (1) WO1999039433A1 (en)

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EP1176775A1 (en) * 2000-07-24 2002-01-30 Alcatel Low voltage broadband line driver
EP1549037A1 (en) * 2003-12-22 2005-06-29 STMicroelectronics S.r.l. An active impedance synthesis circuit, for example for XDSL splitters
CN101056094B (en) * 2007-04-06 2010-04-21 鞍山吉兆电子有限公司 Coaxial high-power low-pass filtering-impedance converter
EP2493168A4 (en) * 2009-10-20 2017-01-18 Telefónica, S.A. Active microfilter for vdsl2 communication standard

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EP0678979A2 (en) * 1994-04-20 1995-10-25 AT&T Corp. Coupler communication systems which utilize more than one frequency band
US5623543A (en) * 1994-02-01 1997-04-22 British Telecommunications Public Limited Company Two port signalling voltages filter arrangement
WO1997020396A2 (en) * 1995-11-27 1997-06-05 Analog Devices, Inc. Pots splitter assembly with improved transhybrid loss for digital subscriber loop transmission

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Publication number Priority date Publication date Assignee Title
US5623543A (en) * 1994-02-01 1997-04-22 British Telecommunications Public Limited Company Two port signalling voltages filter arrangement
EP0678979A2 (en) * 1994-04-20 1995-10-25 AT&T Corp. Coupler communication systems which utilize more than one frequency band
WO1997020396A2 (en) * 1995-11-27 1997-06-05 Analog Devices, Inc. Pots splitter assembly with improved transhybrid loss for digital subscriber loop transmission

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1176775A1 (en) * 2000-07-24 2002-01-30 Alcatel Low voltage broadband line driver
US6985578B2 (en) 2000-07-24 2006-01-10 Alcatel Low voltage broadband line driver
EP1549037A1 (en) * 2003-12-22 2005-06-29 STMicroelectronics S.r.l. An active impedance synthesis circuit, for example for XDSL splitters
WO2005064911A1 (en) * 2003-12-22 2005-07-14 Stmicroelectronics S.R.L. An active impedance synthesis circuit, for example for xdsl splitters
US8406391B2 (en) 2003-12-22 2013-03-26 Stmicroelectronics S.R.L. Active impedance synthesis circuit, for example for XDSL splitters
CN101056094B (en) * 2007-04-06 2010-04-21 鞍山吉兆电子有限公司 Coaxial high-power low-pass filtering-impedance converter
EP2493168A4 (en) * 2009-10-20 2017-01-18 Telefónica, S.A. Active microfilter for vdsl2 communication standard

Also Published As

Publication number Publication date
AT410384B (en) 2003-04-25
ATA901399A (en) 2002-08-15
SE9800240L (en) 1999-07-30
SE511316C2 (en) 1999-09-13
SE9800240D0 (en) 1998-01-29
AU2304099A (en) 1999-08-16

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