WO1994013061A1 - Dispositif isolant un couplage c.c. d'un circuit c.a. exigeant une symetrie - Google Patents

Dispositif isolant un couplage c.c. d'un circuit c.a. exigeant une symetrie Download PDF

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Publication number
WO1994013061A1
WO1994013061A1 PCT/FI1993/000508 FI9300508W WO9413061A1 WO 1994013061 A1 WO1994013061 A1 WO 1994013061A1 FI 9300508 W FI9300508 W FI 9300508W WO 9413061 A1 WO9413061 A1 WO 9413061A1
Authority
WO
WIPO (PCT)
Prior art keywords
arrangement
coupling
connection
symmetry
additional inductance
Prior art date
Legal status (The legal status 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 status listed.)
Ceased
Application number
PCT/FI1993/000508
Other languages
English (en)
Inventor
Jarmo Loukusa
Kauko Varanka
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nokia Oyj
Original Assignee
Nokia Telecommunications Oy
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 Nokia Telecommunications Oy filed Critical Nokia Telecommunications Oy
Priority to DE4396118T priority Critical patent/DE4396118T1/de
Priority to GB9510894A priority patent/GB2288516B/en
Priority to AU55645/94A priority patent/AU5564594A/en
Publication of WO1994013061A1 publication Critical patent/WO1994013061A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/42—Networks for transforming balanced signals into unbalanced signals and vice versa, e.g. baluns
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q1/00—Details of selecting apparatus or arrangements
    • H04Q1/18—Electrical details
    • H04Q1/30—Signalling arrangements; Manipulation of signalling currents

Definitions

  • the invention relates to an arrangement for isolating a DC coupling from a symmetry requiring AC circuit, said arrangement comprising connection lines which are to be symmetrized and which are connected between the DC coupling and the AC circuit, each of said connection lines comprising at least one inductive iso- lation choke coupled in series on said connection line.
  • An application may be, for instance, the isolation of DC signalling from voice channels in analog telephone channels.
  • the implementation of DC signalling must, however, not reduce the symmetry of a voice channel. What is meant by the symmetry of a voice channel is that, in a symmetrical situation, the impedance of voice conductors in a voice channel against ground potential is of the same order.
  • Analog exchanges are provided with signalling equipment for the formation of speech.
  • the signalling equipment may be, for example, of the type DC 2W, i.e. two-wire DC signalling.
  • the signalling equipment is used to supply direct current through two connection lines by means of resistance switches with different resistances to a voice channel, i.e. to voice conductors. If the resistors were directly connected to the voice conductors, the different resist- ances of the resistors would also be detected by the voice conductors, which would render the voice con ⁇ ductors asymmetric.
  • the current which is generated by common-mode voltage in the voice channel is different in the two connection lines, whereby the common-mode voltage is detrimentally con ⁇ verted into transverse voltage.
  • the use of a plurality of capacitors also retards voltage transmissions in signalling. If, in the known solutions, the first con ⁇ nection line is high-ohmic, the DC coupling is not sym ⁇ metric with respect to the voice conductors, i.e. the voice channel; a higher current would flow through this line than through the other one, as the inductances in the isolation chokes are of the same order but the resistances to be coupled are of a different order.
  • the object of the invention is to provide a new type of arrangement for isolating a DC coupling from a symmetry requiring AC circuit, which arrangement obviates the problems pertaining to the known solutions.
  • the arrangement of the invention is based on the idea that a symmetry improving additional inductance compensates for the higher impedance of the higher-ohmic connection line irrespective of which connection line is the higher-ohmic one. Between the connection lines there is thus provided a symmetrization winding which, on account of being in an opposite phase connection, causes the impedance of the higher-ohmic line to be reduced.
  • the arrangement of the invention has several advantages. Considerably better symmetry attenuation is achieved with the present arrangement than with the known solutions, which are not provided with a symmetrization winding, i.e. additional inductance. As a result of the enhanced symmetry attenuation, the quality of voice transmission is improved.
  • FIG. 1 is a switch diagram of the arrangement of the invention
  • Figure 2 shows the resistor coupling of the arrangement according to the invention when the first connection line is high-ohmic
  • Figure 3 shows the resistor coupling of the arrangement according to the invention when the second connection line is high-ohmic
  • Figure 4 is a symmetry attenuation graph.
  • the arrangement according to the invention is connected between an AC circuit, i.e. voice conductors 1 and 2, and a DC coupling 3.
  • the DC coupling comprises switching means 3a and 3b, which in practice couple resistors 4 and 5, which are shown in Figures 2 and 3, and which are of a different order.
  • a connection is thus formed from the voice channel 1 and 2 to ground plane, or ground potential, and it is possible to supply DC signalling pulses to the voice channel, or voice conductors 1 and 2.
  • the DC coupling 3 may consist of signalling equipment of an analog exchange, by means of which DC signalling pulses are supplied to the voice conductors of the analog exchange.
  • the arrangement - or in practice the isolation circuit - comprises a first connection line a, and a second connection line b, which is parallel to the first connection line a.
  • Figure 1 also shows a voice trans ⁇ former 6, which generates a speech signal to be further processed in the voice conductors.
  • the voice conductors 1 and 2 carry a speech signal 7, among which DC signalling pulses are supplied by means of DC signalling equipment, i.e. the DC signalling coupling 3, 3a, 3b.
  • the arrangement comprises a first isolation choke LI, coupled in series on the first con ⁇ nection line a . , and a second isolation choke L2, coupled in series on the second connection line b.
  • the arrangement further comprises an additional inductance L3 which is coupled between the connection lines a and b, provided with the isolation chokes LI and L2, and which is in an opposite phase connection with respect to the isolation chokes.
  • the additional inductance is a symmetry improving symmetrization winding.
  • the arrange ⁇ ment also comprises a ferromagnetic core 11, on which both the actual isolation chokes LI and L2 and the addi- tional inductance L3 of the invention are preferable mounted; the mutual inductance between the chokes LI and L2 and the additional inductance L3 is thus high, and the structure comprising the chokes and the additional inductance is, on the one hand, sufficiently small and, on the other hand, inexpensive to manufacture.
  • the arrangement further comprises a capacitance Cl.
  • the additional inductance L3 between the connection lines a and b to be symmetrized, and thus also between the actual isolation chokes LI and L2, is coupled in series with the capacitance Cl, preferably a capacitor.
  • the capacitance Cl forms thus a barrier to the direct current and part of the impedance between the connection lines a and b. Since the aim is to achieve symmetry, the inductances of the actual isolation chokes LI and L2 are designed to be at least approximately identical, for instance in such a manner that the inductances are of the order of 1.2 H (henry).
  • Figure 2 illustrates the resistor coupling of the arrangement according to the invention when the first connection line a is high-ohmic, e.g. 50 kohm in the resistance, i.e. the resistor 4, which corresponds to the open position of the switching means 3a shown in Figure 1.
  • the second connection line b is low-ohmic, e.g. 1 kohm in the resistor 5, which corres ⁇ ponds to the almost closed position of the switching means 3b shown in Figure 1.
  • Figure 3 illustrates the resistor coupling of the arrangement according to the invention when the high-ohmic connec- tion line is the second connection line b.
  • the resistor coupling according to Figure 2 operates in such a manner that in the higher-ohmic con ⁇ nection line a the current flows from the voice con ⁇ ductor 1 to the isolation choke LI on the connection line a, and further through the capacitor Cl and the additional inductance L3, which is in an opposite phas- e connection in accordance with the invention, and through the low-ohmic resistance 5 to ground potential.
  • the isolation choke LI and the additional inductance L3, i.e. a symmetrization winding or an auxiliary wind ⁇ ing are in an opposite phase connection, i.e.
  • the current flowing through the choke LI, the capacitor Cl and the additional inductance L3 encounters a lower inductance and impedance on this route than on the second connection line b (the induct- ances of the isolation chokes LI and L2 being identical on account of the desired symmetry).
  • the additional inductance L3 compensates for the inductance of the isolation choke LI, i.e. L3 reduces the impedance of the higher-ohmic or more resistive connection line, in this case the connection line a, measured against the ground.
  • Figure 3 illustrates the resistor coupling of the arrangement of the invention when the connection line b is high-ohmic, in which case, contrary to the above, the second resistance 5 is e.g. 50 kohm.
  • the current flows to ground potential along the route from the voice conductor 2 to the second connection line b, and further through the second isolation choke L2 and the additional inductance L3, which is in an opposite phase connection with respect to L2, and Cl, coupled in series, to the resistance 4, which in this case is low- ohmic (1 kohm).
  • the second isolation choke L2 and the additional inductance L3 are in an opposite phase connection, i.e. coupled in opposite polarity, they compensate for each other's inductances, whereby the inductance and thus also the impedance of the second connection line b, in this case the higher-ohmic one, is reduced.
  • the additional induct ⁇ ance i.e. the symmetrization winding L3, thus compens- ates for, or reduces, the impedance of the higher-ohmic connection line.
  • the number of turns of the winding L3 which forms the addi ⁇ tional inductance is clearly smaller than that of the actual isolation chokes LI and L2.
  • the number of turns of L3 and the capacitance of the capacitor Cl, coupled in series, are preferably selected in such a manner that, in accordance with the symmetry attenuation graph shown in Figure 4, the attenuation is highest when the frequency of the sound spectrum is of the order of 300 Hz.
  • the numbers of turns are preferably selected in such a manner that those of the isolation chokes LI and L2 are at least approximately of the same order, e.g. ca 1700 turns, and that of the additional winding L3 is ca 100.
  • the addi ⁇ tional inductance L3 is preferably connected between the isolation chokes LI and L2 and the DC coupling 3, 3a, 3b; this embodiment brings out the advantages of the invention in the best possible manner.
  • the topmost curve is preferably connected between the isolation chokes LI and L2 and the DC coupling 3, 3a, 3b; this embodiment brings out the advantages of the invention in the best possible manner.
  • the symmetrization winding, or additional inductance L3 can essentially improve the attenuation at low frequencies in the vicinity of 300 Hz. If both of the connection lines should be low- ohmic, no voltage is generated between the connection lines, and the additional inductance, i.e. the addi ⁇ tional winding L3, does not operate at all. In a symmet ⁇ rical situation, the additional inductance winding L3 does therefore not weaken the operation of the coupling.
  • the additional inductance L3 is in an opposite phase connec ⁇ tion between the DC isolation chokes LI and L2 in series with the capacitor Cl.
  • LI and L2 are also in an opposite phase connection with respect to each other towards the conductors 1 and 2.
  • the voltage generated over the auxiliary winding L3 and the capacitor Cl, coupled in series provides a symmetrization current, which equalizes the impedance detected by the AC conductors, i.e. the voice conductors 1 and 2.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Filters And Equalizers (AREA)
  • Coils Or Transformers For Communication (AREA)
  • Coupling Device And Connection With Printed Circuit (AREA)

Abstract

L'invention a trait à un dispositif isolant un couplage c.c. d'un circuit c.a. exigeant une symétrie. Ce dispositif comprend des lignes de connexion (a et b) qui doivent être rendues symétriques et sont montées entre le couplage c.c. (3) et le circuit c.a. (1 et 2), chacune de ces lignes comprenant au moins une bobine d'isolation inductive (L1 et L2) montée en série sur elle. Ce dispositif comprend une inductance supplémentaire (L3) qui est connectée en opposition de phase entre les lignes de connexion (a et b) dotées des bobines d'isolation (L1 et L2).
PCT/FI1993/000508 1992-11-30 1993-11-30 Dispositif isolant un couplage c.c. d'un circuit c.a. exigeant une symetrie Ceased WO1994013061A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
DE4396118T DE4396118T1 (de) 1992-11-30 1993-11-30 Anordnung zum Trennen einer Gleichstromkopplung von einer Symmetrie fordernden Wechselstromschaltung
GB9510894A GB2288516B (en) 1992-11-30 1993-11-30 Arrangement for isolating a DC coupling from a symmetry requiring AC circuit
AU55645/94A AU5564594A (en) 1992-11-30 1993-11-30 Arrangement for isolating a dc coupling from a symmetry requiring ac circuit

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI925451A FI95183C (fi) 1992-11-30 1992-11-30 Sovitelma tasavirtakytkennän erottamiseksi symmetriaa vaativasta vaihtovirtapiiristä
FI925451 1992-11-30

Publications (1)

Publication Number Publication Date
WO1994013061A1 true WO1994013061A1 (fr) 1994-06-09

Family

ID=8536299

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI1993/000508 Ceased WO1994013061A1 (fr) 1992-11-30 1993-11-30 Dispositif isolant un couplage c.c. d'un circuit c.a. exigeant une symetrie

Country Status (5)

Country Link
AU (1) AU5564594A (fr)
DE (1) DE4396118T1 (fr)
FI (1) FI95183C (fr)
GB (1) GB2288516B (fr)
WO (1) WO1994013061A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0286795A2 (fr) * 1987-04-14 1988-10-19 Telenorma Gmbh Circuit pour la connexion du courant de sonnerie dans des centraux de télécommunications, spécialement dans des centraux téléphoniques
GB2224909A (en) * 1988-11-11 1990-05-16 Stc Plc Balanced constant current feed for subscriber lines
EP0379902A1 (fr) * 1989-01-27 1990-08-01 Siemens Aktiengesellschaft Dispositif de traitement d'informations à couplage inductif
EP0489194A1 (fr) * 1990-12-05 1992-06-10 Siemens Aktiengesellschaft Agencement de circuit

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0286795A2 (fr) * 1987-04-14 1988-10-19 Telenorma Gmbh Circuit pour la connexion du courant de sonnerie dans des centraux de télécommunications, spécialement dans des centraux téléphoniques
GB2224909A (en) * 1988-11-11 1990-05-16 Stc Plc Balanced constant current feed for subscriber lines
EP0379902A1 (fr) * 1989-01-27 1990-08-01 Siemens Aktiengesellschaft Dispositif de traitement d'informations à couplage inductif
EP0489194A1 (fr) * 1990-12-05 1992-06-10 Siemens Aktiengesellschaft Agencement de circuit

Also Published As

Publication number Publication date
GB2288516A (en) 1995-10-18
GB2288516B (en) 1996-06-05
FI925451A0 (fi) 1992-11-30
FI925451L (fi) 1994-05-31
DE4396118T1 (de) 1995-11-23
GB9510894D0 (en) 1995-08-02
AU5564594A (en) 1994-06-22
FI95183B (fi) 1995-09-15
FI95183C (fi) 1995-12-27

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