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WO2003039125A1 - Procede et dispositif destine au filtrage passe-bas - Google Patents

Procede et dispositif destine au filtrage passe-bas Download PDF

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Publication number
WO2003039125A1
WO2003039125A1 PCT/EP2002/011220 EP0211220W WO03039125A1 WO 2003039125 A1 WO2003039125 A1 WO 2003039125A1 EP 0211220 W EP0211220 W EP 0211220W WO 03039125 A1 WO03039125 A1 WO 03039125A1
Authority
WO
WIPO (PCT)
Prior art keywords
signal
low
transformer
tapped
pass
Prior art date
Application number
PCT/EP2002/011220
Other languages
German (de)
English (en)
Inventor
Peter Caldera
Herbert Zojer
Original Assignee
Infineon Technologies Ag
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 Infineon Technologies Ag filed Critical Infineon Technologies Ag
Publication of WO2003039125A1 publication Critical patent/WO2003039125A1/fr

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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

Definitions

  • the present invention relates to a method and a
  • Low-pass filtering can be used to dampen or block higher-frequency components of a signal. This is used in particular in communications technology in order to be able to transmit different signals simultaneously via one line. Different signals are transmitted in different frequency ranges, the different signals all having to be separated on the transmitter and receiver side with filters.
  • Data signals are transmitted.
  • the phone signals must be limited to a certain frequency band so that the phone signals and the data signals do not interfere with each other. Conversely, the data signals must be kept away from the devices for transmitting the telephone signals in order not to cause interference in them.
  • a feature of the conventional analog transmission of telephone signals is that the transmission line must have a very low resistance, since a current flows through the line which is used to operate the conventional telephone devices.
  • certain filters or splitters are known which feed the data signals into a conventional telephone line and also couple them out again, whereby it must be ensured that the data signals do not reach devices for processing the telephone signals. These are, in particular, a telephone device on the subscriber side and the devices of the telephone service provider for transmitting and receiving the telephone signals on the distributor side.
  • splitters are made up of analog elements. They either consist of passive components or contain active elements such as operational amplifiers. All of these solutions are specially tailored to the impedance of the telecommunications line and the method used to transmit the telephone and data signals. Programming can only be done to a limited extent, e.g. B. by using relays.
  • the present invention is based on the object of providing a method and a device for low-pass filtering of signals transmitted via a telecommunication line, with which a broad range of applications can be achieved largely independently of the impedance requirements of the telecommunication line and of the method used for the transmission.
  • a signal is tapped on the telecommunication line on which the low-pass filtering signal is transmitted, this is high-pass filtered and inverted as compensation signals via a transformer Telecommunications line coupled. Due to the previous inversion, the injected signal is subtracted from the original signal on the telecommunication line. Since the low-frequency components of the tapped signal were removed during high-pass filtering, there is no change in the original signal on the telecommunications line in this frequency band. However, the high-frequency signal components cancel each other out through this inversion.
  • This type of filtering has the particular advantage that the electrical properties of the telecommunications line are only influenced by the transformer.
  • This method is particularly suitable for very low-resistance telecommunication lines.
  • a transformer with a first low-resistance winding can be used, which is looped into the telecommunications line.
  • the inverted signal is coupled in via a second winding inductively coupled to the first winding. Due to the low resistance of the first winding, the impedance of the telecommunications line is changed only very slightly or not, so that this type of low-pass filtering can also be used in different countries with different impedance requirements.
  • the method according to the invention is particularly suitable for
  • the telecommunication line has a very low resistance and flows a current that is used by a connected telephone to operate it. This current flow causes a lot with conventional filters high effort, which is avoided in the inventive method.
  • An essential feature of the present invention is that the low-pass filtering occurs only in the direction of transmission from the tapping point at which the signals coupled in after high-pass filtering and inversion are tapped to the transformer. A different transfer function results in the other transfer direction.
  • a second tapping point can be provided on the side of the transformer opposite a first tapping point, at which a signal is also tapped, high-pass filtered and, after inversion, coupled into the telecommunications line by means of the transformer.
  • a symmetrical filter can be achieved which has a low-pass filter effect in both transmission directions.
  • two separate transformers can also be used, with the coupling of the two signals using a single transformer representing less effort.
  • the signals can be tapped via capacitors or a transformer.
  • a digital filter is particularly suitable for low-pass filtering, since it is particularly easy to program and its filtering effect can be changed.
  • the signal must be digitized at the tap with an analog / digital converter and fed to the digital filter.
  • the digital signal processing chain which can also include inversion, the signal must be converted back into an analog signal by means of a digital / analog converter. All digital signal processing operations can advantageously be carried out in a digital signal processor.
  • the filter functions and counter if necessary, the inversion function for both signal sections can also be carried out by a single processor.
  • either two analog / digital converters can be provided, or an analog / digital converter with an analog multiplexer or with two inputs can be used.
  • the signal tapped at a tap can advantageously also be used to obtain data transmitted on the telecommunications line.
  • the tapped signal can be demodulated or fed directly to a decision maker who extracts the data from the signal.
  • a signal is tapped, high-pass filtered and inverted according to the invention - Coupled back in via the transformer.
  • the telephone signal together with the data signal are on the telecommunications line.
  • a signal is also tapped on the mixed signal side, on which telephone signals and data signals are present, and after
  • Inverted high-pass filtering coupled in via the transformer.
  • the signal tapped on the mixed signal side is simultaneously demodulated, so that the tapped signal is used both for obtaining the data and for filtering the data signals.
  • the signal is tapped on the telephone signal side using an inexpensive capacitor and on the mixed signal side using a transformer.
  • the tap on the mixed signal side by means of a transformer has the advantage that data transformers on the mixed signal side can also be fed into the telecommunication line via this transformer.
  • the data fed in can advantageously also be taken into account in the filter circuit in order to block the data signals coupled in at the tapping point on the mixed signal side on the transformer. In this way, both the data signals arriving on the mixed signal side and the signals fed in there can be blocked on the transformer and prevented from spreading on the telephone signal side.
  • a control circuit can be provided, in particular to compensate for non-linearities of the transformer.
  • the signal tapped from the telecommunications line at a tapping point is compared with a control signal tapped at the other side of the transformer.
  • the signal obtained at the tap corresponds to the signal on the telecommunication line before filtering, whereas the control signal corresponds to the filtered signal.
  • the signal components that should be removed by means of low-pass filtering or that are the result of high-pass filtering must result. If the desired filter effect does not appear, this can be done by comparing the difference between the signal at the tap and the control signal and the high pass filter obtained at the tap. th signal can be recognized. This information can be used to optimize the filter effect and in particular to compensate for non-linearities of the transformer.
  • the control loop can also be implemented digitally in the signal processor.
  • FIG. 1 shows the structure of a low-pass filter according to a first exemplary embodiment of the present invention
  • FIG. 2 shows a symmetrical low-pass filter according to a second embodiment of the present invention
  • FIG. 3 shows a two-sided low-pass filter for receiving data according to a third exemplary embodiment of the present invention
  • FIG. 4 shows a low-pass filter with devices for transmitting and receiving data and a correction control according to a fourth exemplary embodiment of the present invention
  • FIG. 5 shows a low-pass filter with a device for sending data and a correction control according to a fifth exemplary embodiment of the present invention.
  • the telecommunications line consists of a telephone signal section 2, into which a provider of a telephone service feeds the telephone signal, and a transmission section 3, which corresponds to the line to the end user.
  • the circuit arrangement shown in Figure 1 is intended for use on the service provider side.
  • the signal fed into the telephone signal section 2 comprises, in addition to the low-frequency telephone useful signal, also higher-frequency interference components and is low-resistance. A not inconsiderable current flows via the telecommunication line 2, 3 and is used on the end user side to operate a telephone.
  • the telephone signal section 2 is separated from the transmission section 3 by means of a transformer 1, the low-resistance secondary winding of which is looped into the telecommunication line 2, 3.
  • the secondary winding has a low resistance and has a resistance of 0.3 to 0.4 ohms, for example.
  • Two capacitors 4 for tapping a signal are connected to the telephone signal section 2.
  • An analog / digital converter 6 is connected to the capacitors 4, the output of which converts with the input of a digital
  • Filters 7 is connected.
  • the digital filter 7 which is implemented by means of a digital signal processor, the signal tapped off by means of the capacitors 4 on the telephone signal section 2 is high-pass filtered. The desired spectral components of the telephone signals are removed from the signal, so that the higher-frequency interference signals to be removed are at the output of the digital filter 7.
  • the output of the digital filter 7 is connected to a digital / analog converter 8, in which the signal is additionally inverted.
  • the output of the digital / analog converter 8 is connected to a driver 9, which in turn is connected to a primary winding of the transformer 1.
  • FIG. 2 A low-pass filter according to a second embodiment is shown in FIG. In this embodiment, the low-pass filter effect is achieved in both transmission directions.
  • the low-pass filter according to FIG. 2 has a second pair of tapping capacitors 5, which are connected to a second analog / digital converter 10.
  • the second analog / digital converter 10 is followed by a second high-pass filter 11, the output of which is connected to a second digital / analog converter 12.
  • the second tapping capacitors 5 are connected to the transmission section of the telecommunication line.
  • a signal is tapped from the telecommunications line, digitized, high-pass filtered, and coupled in in an inverted analog manner by means of the transformer 1.
  • This symmetrical structure results in the same transmission characteristic in both directions of transmission or a low-pass filter effect is achieved in both directions of transmission.
  • the two analog / digital converters 6, 10, the two high-pass filters 7, 11 and the two digital / analog converters 8, 12 are each to be understood as function blocks, which can also be combined depending on the desired circuit structure.
  • the two high-pass filters 7, 11 can be implemented with a single signal processor.
  • the filter shown in FIG. 2 different transmission characteristics can be achieved for the two high-pass filters 7, 11 by programming the two high-pass filters 7, 11 differently. If, for example, such a low-pass filter is used as a splitter in a telecommunications network to separate data signals and telephone signals, the filter can be designed in such a way that the undesired high-frequency components of the telephone signal are removed in the transmission direction from the telephone signal section 2 to the transmission section 3 and the data signals in the opposite direction be removed. In this case, an additional device (not shown) must be used to ensure that the data signals are tapped at the transmission section 3 or are coupled in there.
  • the low-pass filter shown in FIG. 3 is used to remove undesired high-frequency interference signals from a telephone signal in one transmission direction and to tap data signals in accordance with the DSL standard in the other transmission direction and to remove them in the telecommunications line 2, 3.
  • a transformer 1 with its low-resistance secondary winding is looped in again between the telephone signal section and the transmission section 3.
  • a signal is tapped off from the telephone signal section 2 by means of two tapping capacitors 4.
  • the tapped signal is high-pass filtered and inverted in a signal processing chain with an analog / digital converter 6, a digital high pass 7 and a digital / analog converter 8 as described above.
  • the output signal of the digital / analog converter 8 is fed into the primary winding of the transformer 1 via a driver 9.
  • This structure corresponds to the low-pass filter according to the first embodiment and effects low-pass filtering in the transmission direction from the telephone signal section 2 to the transmission section 3 in order to remove the undesired higher-frequency interference signals of the telephone signal.
  • a DSL transformer 13 is connected to the transmission section 3 and is used for tapping data.
  • the output of the DSL transformer 13 is connected to an amplifier 14, the output of which is connected to an analog / digital converter 15.
  • the data signal tapped by the transmission section 3 is present as a DSL signal.
  • the DSL signal 16 is fed to the high pass 7 in the same way as the signal tapped at the telephone signal section 2. This means that the trans- formators 1, the high-pass filtered DSL signal 16 is also coupled inverted. In this way, the data signals are blocked by means of the transformer 1 and cannot spread into the telephone signal section 2.
  • this low-pass filter has the same components as the low-pass filter according to the first embodiment in FIG. 1.
  • a low-pass filter effect in the transmission direction from the telephone signal section 2 to the transmission section 3 is achieved with the aid of the signal tapped at the telephone signal section 2 by means of the capacitors 4, which is then coupled in again in a high-pass filter and inverted by means of the transformer 1. to keep undesired higher-frequency interference components of the telephone signal away from the transmission section 3.
  • a correction amplifier 18 which receives as input signals, on the one hand, the signal picked up by the capacitors 4 on the telephone signal section 2 and, on the other hand, a control signal picked up on the transmission section 3 via second capacitors 5.
  • the correction amplifier 18 forms the
  • the signal difference formed by the correction amplifier 18 corresponds to the output signal of the high-pass filter 7. If, particularly due to non-linearities of the transformer 1, the higher-frequency interference signals of the telephone signal have not been completely removed by the signals fed in by means of the transformer 1, the signal difference formed by the correction amplifier 18 differs from the output of the high pass filter 7. Depending on the signal difference formed and the output signal of the high-pass filter 7, the correction amplifier 18 generates a correction signal which is connected to the connection path between the digital / analog converter 8 and the driver 9.
  • the correction signal is formed in such a way that the signal difference corresponds as closely as possible to the output signal of the high-pass filter 7 or that the desired low-pass filter effect is established.
  • a DSL signal 17 is applied to the input of the high-pass filter 7.
  • This DSL signal 17 is provided for transmission via the transmission section 3 and is to be coupled in by means of the transformer 1. Since this signal lies in a frequency band above the frequency band of the telephone signals, it passes through the high-pass filter 7 and, after inversion, is coupled into the telecommunication line 2, 3 by means of the driver 9 and the transformer 1.
  • the separate DSL transformer for coupling the DSL signal is advantageously omitted.
  • FIG. 5 shows a low-pass filter according to a fifth embodiment, in which DSL data 17 are to be transmitted via the transmission section 3 in addition to the low-pass filtering with control function.
  • the low-pass filter is designed by means of the signal processing chain comprising an analog / digital converter 6, high-pass filter 7, inverting digital / analog converter 8, driver 9 and transformer 1, the input of the analog / digital converter 6 using two tapping capacitors 4 is connected to the telephone signal section 2.
  • a correction amplifier 18 is provided which, as in the fourth embodiment, Example described the function of the low-pass filter optimized.
  • the low-pass filter shown in FIG. 5 has a DSL transformer 13, the secondary winding of which is looped into the transmission section 3 of the telecommunications line.
  • the primary winding of the DSL transformer 13 is connected to a DSL driver 19, which is acted upon by the DSL signal 17 to be transmitted.
  • the DSL signal 17 is thus coupled into the transmission section 3 after the transformer 1.
  • the DSL signal 17 is simultaneously switched to the input of the high-pass filter 7.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Telephone Function (AREA)
  • Telephonic Communication Services (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)

Abstract

En particulier dans les réseaux de télécommunication, il est nécessaire de séparer les signaux de différentes gammes de fréquences notamment à l'aide de filtres passe-bas. Dans le cas d'un filtre passe-bas selon l'invention, un signal est prélevé dans un point de prélèvement d'une ligne de télécommunication (2, 3), notamment filtré passe-bas par voie numérique puis injecté dans la ligne de télécommunication (2, 3) après inversion à l'aide d'un transformateur (1). L'inversion effectuée permet de soustraire le signal injecté du signal d'origine. Les fractions basse fréquence étant supprimées lors du filtrage passe-bas, le signal d'origine ne subit aucune modification dans cette bande de fréquences. Toutefois, les fractions de signaux haute fréquence s'annulent par l'inversion. Le transformateur (1) peut avantageusement être réalisé à basse impédance de telle façon que l'impédance de la ligne de télécommunication (2, 3) soit peu modifiée. On utilise un filtre passe-bas fonctionnant selon ce principe notamment pour séparer les signaux téléphoniques des signaux de données au niveau du fournisseur de services.
PCT/EP2002/011220 2001-10-31 2002-10-07 Procede et dispositif destine au filtrage passe-bas WO2003039125A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE10153740.9 2001-10-31
DE2001153740 DE10153740B4 (de) 2001-10-31 2001-10-31 Verfahren und Vorrichtung zur Tiefpassfilterung

Publications (1)

Publication Number Publication Date
WO2003039125A1 true WO2003039125A1 (fr) 2003-05-08

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WO (1) WO2003039125A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5982785A (en) * 1996-04-23 1999-11-09 Siemens Aktiengesellschaft Combination conventional telephony and high-bit-rate digital channel transmission system comprising high pass filters which comprise both first order and second order high pass filters
WO2000030336A1 (fr) * 1998-11-16 2000-05-25 Conexant Systems, Inc. Dispositif multifonctions d'acces aux donnees
US6263077B1 (en) * 1997-10-03 2001-07-17 Conexant Systems, Inc. Digital subscriber line modem utilizing echo cancellation to reduce near-end cross-talk noise

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2304216A1 (fr) * 1975-03-10 1976-10-08 Foret Jacques Procede et dispositif de filtrage a plusieurs voies de sortie
DE3337291A1 (de) * 1983-10-13 1985-06-13 Peter Dipl.-Ing. 7550 Rastatt Lawo Schaltungsanordnung eines aktiven filters
FI106682B (fi) * 1999-02-15 2001-03-15 Nokia Networks Oy Kapea- ja laajakaistaisten palvelujen erotus siirtoyhteydellä

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5982785A (en) * 1996-04-23 1999-11-09 Siemens Aktiengesellschaft Combination conventional telephony and high-bit-rate digital channel transmission system comprising high pass filters which comprise both first order and second order high pass filters
US6263077B1 (en) * 1997-10-03 2001-07-17 Conexant Systems, Inc. Digital subscriber line modem utilizing echo cancellation to reduce near-end cross-talk noise
WO2000030336A1 (fr) * 1998-11-16 2000-05-25 Conexant Systems, Inc. Dispositif multifonctions d'acces aux donnees

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
CIOFFI J ET AL: "Digital subscriber lines", COMPUTER NETWORKS, ELSEVIER SCIENCE PUBLISHERS B.V., AMSTERDAM, NL, vol. 31, no. 4, 25 February 1999 (1999-02-25), pages 283 - 311, XP004304484, ISSN: 1389-1286 *
LIN D W ET AL: "A tutorial on digital subscriber line transceiver for ISDN", ISCAS 88, XP010069678 *

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Publication number Publication date
DE10153740B4 (de) 2006-05-24
DE10153740A1 (de) 2003-05-28

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