EP0808529A1 - Method and device for reducing rf transmission interference and use thereof in an interactive television network - Google Patents

Method and device for reducing rf transmission interference and use thereof in an interactive television network

Info

Publication number
EP0808529A1
EP0808529A1 EP96941099A EP96941099A EP0808529A1 EP 0808529 A1 EP0808529 A1 EP 0808529A1 EP 96941099 A EP96941099 A EP 96941099A EP 96941099 A EP96941099 A EP 96941099A EP 0808529 A1 EP0808529 A1 EP 0808529A1
Authority
EP
European Patent Office
Prior art keywords
signal
interfering signal
interfering
received
useful signal
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.)
Withdrawn
Application number
EP96941099A
Other languages
German (de)
French (fr)
Inventor
Pierre Kasser
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.)
Telediffusion de France ets Public de Diffusion
Original Assignee
Telediffusion de France ets Public de Diffusion
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 Telediffusion de France ets Public de Diffusion filed Critical Telediffusion de France ets Public de Diffusion
Publication of EP0808529A1 publication Critical patent/EP0808529A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • 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
    • H04B1/06—Receivers
    • H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
    • H04B1/12—Neutralising, balancing, or compensation arrangements
    • H04B1/123—Neutralising, balancing, or compensation arrangements using adaptive balancing or compensation means
    • H04B1/126—Neutralising, balancing, or compensation arrangements using adaptive balancing or compensation means having multiple inputs, e.g. auxiliary antenna for receiving interfering signal

Definitions

  • the invention relates to a method and a device for reducing interference from radio transmission in a single-frequency or multi-frequency network.
  • Transmission networks such as radio or television networks, include a source earth station from which the radio or television programs are produced, transmitted to a telecommunications satellite, this telecommunications satellite retransmitting these programs to reception-retransmission earth stations on a terrestrial radio network.
  • the terrestrial radio network comprises a plurality of retransmission stations each equipped with a satellite reception antenna AS, a receiver and a transmitter connected to a transmitting aerial covering a determined terrestrial geographical area.
  • Two retransmission stations S lr S 2 are normally spaced apart by a distance of about 150 km maximum.
  • a user placed between two re-transmission stations S ,, S 2 , is required to transmit interactive signals at a frequency F ⁇ to the nearest transmitting station in order to allow the interactive sequence of a TV program, for example with the source earth station, or any intermediate station provided for this purpose if necessary.
  • the user receives from the nearest transmitting station If the TV program has a frequency F 2 .
  • the signals transmitted by the user at the frequency F x are subjected, on the part of the distant transmitting stations S 2 , to an interference phenomenon at a frequency close to or identical, due to the transmitting power much most of these transmitting stations and the limited frequency space allocated to these terrestrial radio networks.
  • the station S 1 ( therefore receives the useful signal at the frequency F x generated by the user and an interfering signal at this same frequency Fi or at a very close frequency.
  • the station S 1 there is no no device or technique exists for ensuring a systematic reduction of the above-mentioned interference, except those which use rejection systems creating filtering in the useful frequency band received or causing rejection on the antenna pattern in the direction
  • rejector systems are however ineffective if the signal due to the jammer has a frequency bandwidth greater than that of the wanted signal or if the wanted signal comes from the same direction as the jammer. 'inconvé ⁇ deny the above.
  • Radio interference reduction device taking advantage of the fact of the simultaneous presence of the same signal, contributing to the interference signal, on two different transmission media, these signals, although generally having different spectral characteristics, nevertheless carry the same information.
  • the radio interference interference reduction method and device of a useful signal transmitted to a receiver are remarkable in that they implement, at the reception level, a first channel for receiving the useful signal in the presence of the interfering signal, delivering a useful signal received in the presence of the interfering second channel for receiving the interfering signal, generated by delayed duplication of the interfering signal transmitted by the satellite network, delivering a received interfering signal similar to the interfering signal their present in the first channel with the useful signal and means subtracting the interfering signal received from the useful signal in the presence of the interfering signal, which makes it possible to deliver a useful signal received free of interfering signal.
  • the radio interference reduction device, object of the present invention finds application in the implementation and management of radio networks or radio broadcasting of radio or television programs.
  • FIG. 2a shows a block diagram of a radio interference reduction device installed in a multi-frequency type transmission network
  • - Figure 2b shows a detail of the device, object of the present invention
  • - Figure 2c shows an illustrative diagram of implementation of the radio interference reduction method, object of the present invention
  • - Figure 3 shows, in an ampli ⁇ tude-frequency diagram the shape of the frequency spectra of the signals obtained at different test points of Figure 2b, in the case where these signals are TV signals.
  • the device, object of the present invention comprises at the reception level of the above-mentioned transmitting station S x a first channel V ⁇ for receiving the useful signal, in the presence of the interfering signal, this first channel delivering a useful signal received in the presence of the interferer and a second channel V 2 for receiving the interfering signal generated by delayed duplication of the interfering signal transmitted by the satellite network.
  • the second channel V 2 delivers a received interfering signal similar to the interfering signal present in the first channel V x with the useful signal.
  • the device, object of the invention comprises a module subtracting the interfering signal received from the useful signal in the presence of the interfering signal, which makes it possible to deliver, for example to a transmitter of the transmitting station S ! a useful signal received free of any scrambling signal for the retransmission of this useful signal received towards the source ground station, for example, or towards an intermediate station.
  • the device, object of the present invention is composed of two aerial systems, an aerial AT for reception of terrestrial radio signals receiving the signal transmitted by the user, it is i.e. the useful signal at the frequency F 1 and the signal emitted by the jammer, i.e. the signal emitted at the same frequency F x or at a frequency very close by the jammer, either by the station transmission S 2 of the same radio network, and an aerial for reception of radio signals transmitted by the satellite, the antenna AS in FIG. 2a, normally present, for example, in the installations of the transmission station S x .
  • each channel v lr V 2 also includes corresponding demodulation equipment as will be described later in the description.
  • the signals thus received by the channels V : and V 2 are demodulated in baseband, then aligned in time by a delay compensating device, calibrated exactly on the difference of the propagation time of the signals.
  • this delay is only related to time propagation and processing between the interfering transmitter site of the transmitting station S 2 and the receiving site, the transmitting station S x , due to the almost synchronous supply of the two transmitting station sites by the same satellite signal. It is indeed indicated that the distance of 150 km which separates the transmitting stations S : and S 2 is negligible compared to the distance of a satellite such as a geostationary satellite, for example, compared to the terrestrial surface.
  • the aforementioned delay for two transmitting sites or stations separated by a distance of between 100 and 150 km can be of the order of 500
  • the signal received by satellite under good propagation conditions, at the transmitting station S lr is preferably delayed because this signal is received with an optimal quality, superior to that of the signal transmitted by the terrestrial radio network.
  • each channel V x and V 2 are then temporally aligned baseband signals, which are added in phase opposition by means of a 0-u coupler, for example.
  • the first channel V ⁇ comprises, for example, advantageously, connected in cascade: the terrestrial reception antenna denoted AT, a baseband demodulator of conventional type, a device for equalization for performing an equalization treatment of conventional type, that is to say of amplitude and frequency equalization.
  • the equalization circuit is followed by a gain-inverting circuit -1.
  • the second channel comprises, connected in cascade, the satellite reception antenna AS, a demodulator of the satellite channel in baseband of conventional type, this demodulator being followed by an equalization device also making it possible to achieve an equalization processing of the demodulated signals both in amplitude and in frequency.
  • the equalization circuit is then followed by a delay circuit making it possible to compensate for the propagation time of the interfering signal transmitted and to deliver the interfering signal received.
  • a 0- ⁇ coupler receives on its input ports the interfering signal received and the interfering signal plus the useful signal delivered respectively by the second channel V 2 and the first channel V x to deliver the useful signal, that is to say the signal transmitted by the user initially.
  • This useful signal can then be delivered for example to a collection network, not shown, for transmission to the source station or to any suitable intermediate station in order to ensure the interactive progress of the TV program thus broadcast.
  • an equalization device In order to align in amplitude the received interfering signals having undergone different channel distortions, it is preferable to use an equalization device allowing an efficient alignment processing of the levels of the signals to be subtracted over the useful signal bandwidth to get back.
  • the effective gain on the interference depends strongly on the alignment in amplitude and in frequency of the received signals, as well as, of course, that of the compensation or of the time offset. operated on the interfering signal received by the satellite radio network.
  • the aforementioned alignments can advantageously be implemented with good precision thanks to the presence of the test signals, which then make it possible to calibrate the equalization and delay compensation processing perfectly.
  • the method which is the subject of the invention consists in simultaneously receiving the useful signal in the presence of the interfering signal in order to obtain a useful signal received in the presence of the jammer, receiving the interfering signal generated by delayed duplication of the interfering signal transmitted by the satellite network to obtain a received interfering signal, similar to the interfering signal present with the wanted signal.
  • the received interfering signal is subtracted from the useful signal in the presence of the interfering signal to deliver a received useful signal free of an interfering signal.
  • test points A to F have been represented, placed respectively in alphabetical order at the output of the terrestrial antenna AT, at the output of the satellite antenna AS, at the output of the terrestrial demodulator of the first channel , at the output of the gain amplifier -1 of this same first channel, at the output of the delay compensation circuit on the second channel and delivering the interfering signal received and finally, at the output of the coupler 0-r ⁇ deli ⁇ vrant the useful signal after rejection of the interfering signal received.
  • FIG 3 there is shown, by way of non-limiting example, the frequency spectrum of the signal received at the aforementioned test point A, that is to say at the output of the terrestrial antenna AT.
  • This signal is shown for a conventional terrestrial television channel, modulated in MABLR modulation for "reduced sideband modulation".
  • the spectrum of the jammer is superimposed on the spectrum of television signals for the high frequencies thereof.
  • the spectrum of the interfering signal obtained at the output of the satellite antenna AS is represented for a satellite TV channel modulated in frequency modulation.
  • the aforementioned signal is followed by a representation of the spectrum of the useful signal emitted by the user, that is to say of the useful digital signal transmitted in the band of the terrestrial TV channel at the frequency F, towards the transmitting station S :.
  • the spectrum of the video baseband signal is shown for the interfering signal plus the useful signal after phase shift of 180 °, i.e. application of a gain equal to -1, the sign - at point D in FIG. 3, symbolizing the amplification by a gain equal to -1.
  • the sum has been represented, using the 0- ⁇ coupler, an algebraic sum between the signal represented at point D and the signal represented at point E, the signal delivered at point F corresponding to that of the spectrum of the only useful signal, the digital signal cleared of the interfering TV spectrum, after subtraction, this signal then being able to be demodulated for its use or application within the framework of the broadcasting of the interactive TV program mentioned above.
  • the device, object of the present invention makes it possible to improve the spectral efficiency of a broadcasting band by making it suitable for the transmission of new services, whatever its occupation.

Abstract

A method and a device for reducing interference in the RF transmission of a wanted signal. The signal quality is reduced by an interfering signal on a terrestrial and satellite RF network. Accordingly, the method comprises and the device is used for: receiving the wanted signal in the presence of the interfering signal to provide a wanted signal received in the presence of the interfering signal, receiving the interfering signal generated by delayed duplication of the interfering signal transmitted by the satellite network to provide a received interfering signal similar to the interfering signal accompanying the wanted signal, and subtracting the received interfering signal from the wanted signal in the presence of the interfering signal to provide a received wanted signal that is free of the interfering signal. The method and device are useful for setting up and operating networks, particularly interactive television networks.

Description

PROCEDE ET DISPOSITIF DE REDUCTION DU BROUILLAGE DE TRANSMISSION HERTZIENNE ET SON UTILISATION DANS UN RESEAU TV INTERACTIFMETHOD AND DEVICE FOR REDUCING INTERFERENCE OF WIRELESS TRANSMISSION AND ITS USE IN AN INTERACTIVE TV NETWORK
L'invention concerne un procédé et un dispositif de réduction du brouillage de transmission hertzienne en réseau monofréquence ou multifréquence.The invention relates to a method and a device for reducing interference from radio transmission in a single-frequency or multi-frequency network.
Les réseaux de transmission, tels que les réseaux de radiodiffusion ou de télédiffusion comportent une station terrestre source à partir de laquelle les programπies radiodiffusés ou télédiffusés sont élaborés, transmis vers un satellite de télécommunications, ce satellite de télécom¬ munications procédant à la retransmission de ces programmes vers des stations terrestres de réception-réémission sur un réseau hertzien terrestre. Le réseau hertzien terrestre comprend une pluralité de stations de réémission équipée chacune d'une antenne de réception satellite AS, d'un récepteur et d'un émetteur relié à un aérien d'émission couvrant une zone géographique terrestre déterminée. Deux stations Sl r S2 de réémission sont normalement espacées d'une distance de l'ordre de 150 km au maximum. Dans le cas d'un réseau hertzien de télévision interactif, un usager, placé entre deux stations de réémission S,, S2, est amené à émettre des signaux interactifs à une fréquence Fλ vers la station d'émission la plus proche afin de permettre le déroule- ment interactif d'un programme TV par exemple avec la station terrestre source, ou toute station intermédiaire prévue le cas échéant à cet effet. L'usager reçoit de la station d'émission la plus proche Si le programme TV à une fréquence F2. Toutefois, les signaux transmis par l'usager à la fréquence Fx sont soumis, de la part des stations d'émission lointaines S2, à un phénomène de brouillage à une fréquence voisine ou identique, en raison de la puissance d'émission beaucoup plus importante de ces stations d'émission et de l'espace de fréquences limité attribué à ces réseaux hertziens terrestres. La station d'émission pertinente pour l'usager considéré, la station S1( reçoit donc le signal utile à la fréquence Fx engendré par l'usager et un signal brouilleur à cette même fréquence Fi ou à une fréquence très voisine. A l'heure actuelle, il n'existe pas de dispositif ou de technique permettant d'assurer une réduction systématique du brouillage précité, hormis ceux qui font appel à des systèmes réjecteurs créant un filtrage dans la bande de fréquences utile reçue ou provoquant une rejection sur le diagramme d'antenne dans la direction du brouilleur. Ces systèmes réjecteurs sont toutefois inefficaces si le signal dû au brouilleur présente une largeur de bande de fréquences supérieure à celle du signal utile ou si le signal utile provient de la même direction que le brouilleur. La présente invention vise à remédier à l'inconvé¬ nient précité.Transmission networks, such as radio or television networks, include a source earth station from which the radio or television programs are produced, transmitted to a telecommunications satellite, this telecommunications satellite retransmitting these programs to reception-retransmission earth stations on a terrestrial radio network. The terrestrial radio network comprises a plurality of retransmission stations each equipped with a satellite reception antenna AS, a receiver and a transmitter connected to a transmitting aerial covering a determined terrestrial geographical area. Two retransmission stations S lr S 2 are normally spaced apart by a distance of about 150 km maximum. In the case of an interactive radio television network, a user, placed between two re-transmission stations S ,, S 2 , is required to transmit interactive signals at a frequency F λ to the nearest transmitting station in order to allow the interactive sequence of a TV program, for example with the source earth station, or any intermediate station provided for this purpose if necessary. The user receives from the nearest transmitting station If the TV program has a frequency F 2 . However, the signals transmitted by the user at the frequency F x are subjected, on the part of the distant transmitting stations S 2 , to an interference phenomenon at a frequency close to or identical, due to the transmitting power much most of these transmitting stations and the limited frequency space allocated to these terrestrial radio networks. The relevant transmitting station for the user considered, the station S 1 ( therefore receives the useful signal at the frequency F x generated by the user and an interfering signal at this same frequency Fi or at a very close frequency. At present, there is no no device or technique exists for ensuring a systematic reduction of the above-mentioned interference, except those which use rejection systems creating filtering in the useful frequency band received or causing rejection on the antenna pattern in the direction These rejector systems are however ineffective if the signal due to the jammer has a frequency bandwidth greater than that of the wanted signal or if the wanted signal comes from the same direction as the jammer. 'inconvé¬ deny the above.
Elle a pour objet la mise en oeuvre d'un dispositif de réduction de brouillage hertzien tirant parti du fait de la présence simultanée du même signal, contribuant au signal de brouillage, sur deux supports de transmission différents, ces signaux, bien que possédant généralement des caractéris¬ tiques spectrales différentes, transportent néanmoins la même information.It relates to the implementation of a radio interference reduction device taking advantage of the fact of the simultaneous presence of the same signal, contributing to the interference signal, on two different transmission media, these signals, although generally having different spectral characteristics, nevertheless carry the same information.
Le procédé et le dispositif de réduction du brouil- lage de transmission hertzienne d'un signal utile, transmis vers un récepteur, ce signal utile étant altéré par un signal brouilleur, présent simultanément, au temps de propagation près, sur un réseau hertzien terrestre et satellitaire, objets de la présente invention, sont remar- quables en ce qu'ils mettent en oeuvre, au niveau réception, une première voie de réception du signal utile en présence du signal brouilleur, délivrant un signal utile reçu en présence du brouilleur, une deuxième voie de réception du signal brouilleur, engendré par duplication retardée du signal brouilleur transmis par le réseau satellite, déli¬ vrant un signal brouilleur reçu semblable au signal brouil- leur présent dans la première voie avec le signal utile et des moyens soustracteurs du signal brouilleur reçu du signal utile en présence du signal brouilleur, ce qui permet de délivrer un signal utile reçu exempt de signal brouilleur. Le dispositif de réduction du brouillage hertzien, objet de la présente invention, trouve application à la mise en oeuvre et à la gestion de réseaux hertziens de radio ou télédiffusion de programmes radio ou de télévision.The radio interference interference reduction method and device of a useful signal transmitted to a receiver, this useful signal being altered by an interfering signal, present simultaneously, to the nearest propagation time, on a terrestrial radio network and objects of the present invention are remarkable in that they implement, at the reception level, a first channel for receiving the useful signal in the presence of the interfering signal, delivering a useful signal received in the presence of the interfering second channel for receiving the interfering signal, generated by delayed duplication of the interfering signal transmitted by the satellite network, delivering a received interfering signal similar to the interfering signal their present in the first channel with the useful signal and means subtracting the interfering signal received from the useful signal in the presence of the interfering signal, which makes it possible to deliver a useful signal received free of interfering signal. The radio interference reduction device, object of the present invention, finds application in the implementation and management of radio networks or radio broadcasting of radio or television programs.
Ils sont mieux compris à la lecture de la descrip- tion et à l'observation des dessins dans lesquels, outre la figure 1 relative à l'art antérieur,They are better understood on reading the description and on observing the drawings in which, in addition to FIG. 1 relating to the prior art,
- la figure 2a représente un schéma synoptique d'un dispositif de réduction de brouillage hertzien implanté dans un réseau de transmission de type multifréquence ; - la figure 2b représente un détail de réalisation du dispositif, objet de la présente invention ;- Figure 2a shows a block diagram of a radio interference reduction device installed in a multi-frequency type transmission network; - Figure 2b shows a detail of the device, object of the present invention;
- la figure 2c représente un schéma illustratif de mise en oeuvre du procédé de réduction de brouillage hertzien, objet de la présente invention ; - la figure 3 représente, dans un diagramme ampli¬ tude-fréquence l'allure des spectres de fréquences des signaux obtenus en différents points de test de la figure 2b, dans le cas où ces signaux sont des signaux TV.- Figure 2c shows an illustrative diagram of implementation of the radio interference reduction method, object of the present invention; - Figure 3 shows, in an ampli¬ tude-frequency diagram the shape of the frequency spectra of the signals obtained at different test points of Figure 2b, in the case where these signals are TV signals.
Une description plus détaillée du dispositif de réduction du brouillage de transmission hertzienne d'un signal utile, ce signal étant transmis par un usager vers un récepteur d'une station d'émission, la station Si sur la figure 1, ce signal utile étant altéré par un signal brouilleur présent simultanément au temps de propagation près sur un réseau hertzien terrestre et satellitaire, ainsi que représenté sur la figure 1 précitée, sera maintenant donnée en liaison avec la figure 2a.A more detailed description of the device for reducing radio transmission interference of a useful signal, this signal being transmitted by a user to a receiver of a transmitting station, the station Si in FIG. 1, this useful signal being altered by an interfering signal present simultaneously with the near propagation time on a terrestrial and satellite hertzian network, as represented on the aforementioned figure 1, will now be given in connection with figure 2a.
Ainsi qu'on l'a représenté de manière schématique sur la figure précitée, le dispositif, objet de la présente invention, comprend au niveau réception de la station d'émission Sx précitée une première voie VΛ de réception du signal utile, en présence du signal brouilleur, cette première voie délivrant un signal utile reçu en présence du brouilleur et une deuxième voie V2 de réception du signal brouilleur engendrée par duplication retardée du signal brouilleur transmis par le réseau satellite. La deuxième voie V2 délivre un signal brouilleur reçu semblable au signal brouilleur présent dans la première voie Vx avec le signal utile.As shown schematically in the aforementioned figure, the device, object of the present invention, comprises at the reception level of the above-mentioned transmitting station S x a first channel V Λ for receiving the useful signal, in the presence of the interfering signal, this first channel delivering a useful signal received in the presence of the interferer and a second channel V 2 for receiving the interfering signal generated by delayed duplication of the interfering signal transmitted by the satellite network. The second channel V 2 delivers a received interfering signal similar to the interfering signal present in the first channel V x with the useful signal.
En outre, le dispositif, objet de l'invention, comprend un module soustracteur du signal brouilleur reçu du signal utile en présence du signal brouilleur, ce qui permet de délivrer, par exemple à un émetteur de la station d'émission S! un signal utile reçu exempt de signal brouil¬ leur en vue de la retransmission de ce signal utile reçu vers la station terrestre source, par exemple, ou vers une station intermédiaire.In addition, the device, object of the invention, comprises a module subtracting the interfering signal received from the useful signal in the presence of the interfering signal, which makes it possible to deliver, for example to a transmitter of the transmitting station S ! a useful signal received free of any scrambling signal for the retransmission of this useful signal received towards the source ground station, for example, or towards an intermediate station.
D'une manière générale, on indique que le disposi¬ tif, objet de la présente invention, est composé de deux systèmes d'aériens, un aérien AT de réception des signaux hertziens terrestres recevant le signal émis par l'usager, c'est-à-dire le signal utile à la fréquence F1 et le signal émis par le brouilleur, c'est-à-dire le signal émis à la même fréquence Fx ou à une fréquence très voisine par le brouilleur, soit par la station d'émission S2 du même réseau hertzien, et un aérien de réception des signaux hertziens transmis par le satellite, l'antenne AS sur la figure 2a, normalement présente, par exemple, dans les installations de la station d'émission Sx.In general, it is indicated that the device, object of the present invention, is composed of two aerial systems, an aerial AT for reception of terrestrial radio signals receiving the signal transmitted by the user, it is i.e. the useful signal at the frequency F 1 and the signal emitted by the jammer, i.e. the signal emitted at the same frequency F x or at a frequency very close by the jammer, either by the station transmission S 2 of the same radio network, and an aerial for reception of radio signals transmitted by the satellite, the antenna AS in FIG. 2a, normally present, for example, in the installations of the transmission station S x .
Bien entendu, chaque voie vl r V2 comporte également des équipements de démodulation correspondants ainsi qu'il sera décrit ultérieurement dans la description.Of course, each channel v lr V 2 also includes corresponding demodulation equipment as will be described later in the description.
Les signaux ainsi reçus par les voies V: et V2 sont démodulés en bande de base, puis alignés temporellement par un dispositif compensateur de retard, calé exactement sur la différence du temps de propagation des signaux.The signals thus received by the channels V : and V 2 are demodulated in baseband, then aligned in time by a delay compensating device, calibrated exactly on the difference of the propagation time of the signals.
On indique que ce retard est uniquement lié au temps de propagation et de traitement entre le site émetteur brouilleur de la station d'émission S2 et le site de réception, la station d'émission Sx, du fait de l'alimenta¬ tion quasi synchrone des deux sites de station d'émission par le même signal satellitaire. On indique en effet que la distance de 150 km qui sépare les stations d'émission S: et S2 est négligeable par rapport à la distance d'un satellite tel qu'un satellite géostationnaire, par exemple, par rapport à la surface terrestre. Le retard précité pour deux sites ou stations d'émission séparés par une distance comprise entre 100 et 150 km peut être de l'ordre de 500It is indicated that this delay is only related to time propagation and processing between the interfering transmitter site of the transmitting station S 2 and the receiving site, the transmitting station S x , due to the almost synchronous supply of the two transmitting station sites by the same satellite signal. It is indeed indicated that the distance of 150 km which separates the transmitting stations S : and S 2 is negligible compared to the distance of a satellite such as a geostationary satellite, for example, compared to the terrestrial surface. The aforementioned delay for two transmitting sites or stations separated by a distance of between 100 and 150 km can be of the order of 500
D'une manière générale, le signal reçu par satellite dans de bonnes conditions de propagation, au niveau de la station d'émission Sl r est de préférence retardé car ce signal est reçu avec une qualité optimale, supérieure à celle du signal transmis par le réseau hertzien terrestre.In general, the signal received by satellite under good propagation conditions, at the transmitting station S lr is preferably delayed because this signal is received with an optimal quality, superior to that of the signal transmitted by the terrestrial radio network.
D'une manière générale, on indique que les signaux délivrés par chaque voie Vx et V2 sont alors des signaux en bande de base alignés temporellement, lesquels sont addi¬ tionnés en opposition de phase au moyen d'un coupleur 0-u, par exemple.In general, it is indicated that the signals delivered by each channel V x and V 2 are then temporally aligned baseband signals, which are added in phase opposition by means of a 0-u coupler, for example.
Une description plus détaillée du dispositif, objet de la présente invention, constitué par la première et la deuxième voie de réception et par les moyens soustracteurs précités, sera maintenant donnée en liaison avec la figure 2b.A more detailed description of the device, object of the present invention, constituted by the first and second reception channels and by the aforementioned subtracting means, will now be given in connection with FIG. 2b.
Ainsi que représenté sur la figure précitée, la première voie Vλ comprend, par exemple, de manière avanta- geuse, connectés en cascade : l'antenne de réception terrestre notée AT, un démodulateur en bande de base de type classique, un dispositif d'égalisation permettant de réaliser un traitement d'égalisation de type classique, c'est-à-dire d'égalisation d'amplitude et de fréquence. Le circuit d'égalisation est suivi d'un circuit inverseur de gain -1. De même, la deuxième voie comprend, connectés en cascade, l'antenne de réception satellite AS, un démodula¬ teur de canal satellite en bande de base de type classique, ce démodulateur étant suivi d'un dispositif d'égalisation permettant également de réaliser un traitement d'égalisation des signaux démodulés tant en amplitude qu'en fréquence.As shown in the above-mentioned figure, the first channel V λ comprises, for example, advantageously, connected in cascade: the terrestrial reception antenna denoted AT, a baseband demodulator of conventional type, a device for equalization for performing an equalization treatment of conventional type, that is to say of amplitude and frequency equalization. The equalization circuit is followed by a gain-inverting circuit -1. Likewise, the second channel comprises, connected in cascade, the satellite reception antenna AS, a demodulator of the satellite channel in baseband of conventional type, this demodulator being followed by an equalization device also making it possible to achieve an equalization processing of the demodulated signals both in amplitude and in frequency.
Le circuit d'égalisation est alors suivi d'un circuit retardateur permettant de compenser le temps de propagation du signal brouilleur transmis et de délivrer le signal brouilleur reçu.The equalization circuit is then followed by a delay circuit making it possible to compensate for the propagation time of the interfering signal transmitted and to deliver the interfering signal received.
Un coupleur 0-π. reçoit sur ses ports d'entrée le signal brouilleur reçu et le signal brouilleur plus le signal utile délivrés respectivement par la deuxième voie V2 et la première voie Vx pour délivrer le signal utile, c'est- à-dire le signal transmis par l'usager initialement.A 0-π coupler. receives on its input ports the interfering signal received and the interfering signal plus the useful signal delivered respectively by the second channel V 2 and the first channel V x to deliver the useful signal, that is to say the signal transmitted by the user initially.
Ce signal utile peut alors être délivré par exemple à un réseau de collecte, non représenté, en vue d'une transmission vers la station-source ou vers toute station intermédiaire adaptée afin d'assurer le déroulement interac- tif du programme TV ainsi diffusé.This useful signal can then be delivered for example to a collection network, not shown, for transmission to the source station or to any suitable intermediate station in order to ensure the interactive progress of the TV program thus broadcast.
Afin d'aligner en amplitude les signaux brouilleurs reçus ayant subi des distorsions de canal différentes, il est préférable de recourir à un dispositif d'égalisation permettant un traitement d'alignement performant des niveaux des signaux à soustraire sur la largeur de bande de signal utile à récupérer.In order to align in amplitude the received interfering signals having undergone different channel distortions, it is preferable to use an equalization device allowing an efficient alignment processing of the levels of the signals to be subtracted over the useful signal bandwidth to get back.
Le gain effectif sur le brouillage, c'est-à-dire finalement la rejection du signal de brouillage, dépend fortement de l'alignement en amplitude et en fréquence des signaux reçus, ainsi, bien entendu, que de la compensation ou du décalage temporel opéré sur le signal brouilleur reçu par le réseau hertzien satellitaire. En particulier, lorsque le réseau utilisé est un réseau de télévision de type interactif, les alignements précités peuvent avantageusement être mis en oeuvre avec une bonne précision grâce à la présence des signaux de test, lesquels permettent alors de calibrer parfaitement le traitement d'égalisation et de compensation de retard.The effective gain on the interference, that is to say ultimately the rejection of the interference signal, depends strongly on the alignment in amplitude and in frequency of the received signals, as well as, of course, that of the compensation or of the time offset. operated on the interfering signal received by the satellite radio network. In particular, when the network used is an interactive type television network, the aforementioned alignments can advantageously be implemented with good precision thanks to the presence of the test signals, which then make it possible to calibrate the equalization and delay compensation processing perfectly.
Enfin, ainsi que représenté sur la figure 2c, le procédé, objet de l'invention, consiste à, simultanément, recevoir le signal utile en présence du signal brouilleur pour obtenir un signal utile reçu en présence du brouilleur, recevoir le signal brouilleur engendré par duplication retardée du signal brouilleur transmis par le réseau satellite pour obtenir un signal brouilleur reçu, semblable au signal brouilleur présent avec le signal utile. Le signal brouilleur reçu est soustrait du signal utile en présence du signal brouilleur pour délivrer un signal utile reçu exempt de signal brouilleur.Finally, as shown in FIG. 2c, the method which is the subject of the invention consists in simultaneously receiving the useful signal in the presence of the interfering signal in order to obtain a useful signal received in the presence of the jammer, receiving the interfering signal generated by delayed duplication of the interfering signal transmitted by the satellite network to obtain a received interfering signal, similar to the interfering signal present with the wanted signal. The received interfering signal is subtracted from the useful signal in the presence of the interfering signal to deliver a received useful signal free of an interfering signal.
Sur la figure 2b, on a représenté des points de test A à F, placés respectivement dans l'ordre alphabétique en sortie de l'antenne terrestre AT, en sortie de l'antenne satellite AS, en sortie du démodulateur terrestre de la première voie, en sortie de l'amplificateur de gain -1 de cette même première voie, en sortie du circuit de compensa- tion de retard sur la deuxième voie et livrant le signal brouilleur reçu et enfin, en sortie du coupleur 0-rτ déli¬ vrant le signal utile après rejection du signal brouilleur reçu.In FIG. 2b, test points A to F have been represented, placed respectively in alphabetical order at the output of the terrestrial antenna AT, at the output of the satellite antenna AS, at the output of the terrestrial demodulator of the first channel , at the output of the gain amplifier -1 of this same first channel, at the output of the delay compensation circuit on the second channel and delivering the interfering signal received and finally, at the output of the coupler 0-rτ deli¬ vrant the useful signal after rejection of the interfering signal received.
Sur la figure 3, on a représenté, à titre d'exemple non limitatif, le spectre de fréquence du signal reçu au point de test A précité, c'est-à-dire en sortie de l'antenne terrestre AT. Ce signal est représenté pour un canal de télévision hertzien classique, modulé en modulation MABLR pour "modulation à bande latérale réduite". Le spectre du brouilleur est superposé au spectre des signaux de télévi¬ sion pour les fréquences hautes de celui-ci.In Figure 3, there is shown, by way of non-limiting example, the frequency spectrum of the signal received at the aforementioned test point A, that is to say at the output of the terrestrial antenna AT. This signal is shown for a conventional terrestrial television channel, modulated in MABLR modulation for "reduced sideband modulation". The spectrum of the jammer is superimposed on the spectrum of television signals for the high frequencies thereof.
Au point B, on a représenté le spectre du signal brouilleur obtenu en sortie de l'antenne satellite AS pour un canal TV satellite modulé en modulation de fréquence. Le signal précité est suivi d'une représentation du spectre du signal utile émis par l'usager, c'est-à-dire du signal numérique utile émis dans la bande du canal TV hertzien à la fréquence F, vers la station d'émission S:.At point B, the spectrum of the interfering signal obtained at the output of the satellite antenna AS is represented for a satellite TV channel modulated in frequency modulation. The aforementioned signal is followed by a representation of the spectrum of the useful signal emitted by the user, that is to say of the useful digital signal transmitted in the band of the terrestrial TV channel at the frequency F, towards the transmitting station S :.
Au point C, on a représenté la superposition des spectres des signaux du canal numérique utile dans le spectre du canal TV hertzien après démodulation en bande de base, le spectre global correspondant à la superposition des spectres des signaux au point A et du signal utile émis par 1'usager.At point C, the superposition of the spectra of the signals of the useful digital channel in the spectrum of the terrestrial TV channel has been shown after demodulation in baseband, the global spectrum corresponding to the superposition of the spectra of the signals at point A and of the useful signal transmitted by the user.
Au point D, on a représenté le spectre du signal en bande de base vidéo pour le signal brouilleur plus le signal utile après déphasage de 180°, c'est-à-dire application d'un gain égal à -1, le signe - au point D de la figure 3, symbolisant l'amplification par un gain égal à -1.At point D, the spectrum of the video baseband signal is shown for the interfering signal plus the useful signal after phase shift of 180 °, i.e. application of a gain equal to -1, the sign - at point D in FIG. 3, symbolizing the amplification by a gain equal to -1.
Au point E, on a représenté le spectre du signal brouilleur reçu après compensation du retard et, bien entendu, démodulation en bande de base vidéo, un tel signal, en l'absence d'un gain négatif égal à -1 correspondant au signal changé de signe obtenu au point D pour le signal brouilleur et pour cette raison, portant symboliquement le signe +, ce signal étant obtenu après démodulation FM, bien entendu.At point E, the spectrum of the interfering signal received after compensation for the delay and, of course, demodulation in video baseband, such a signal, in the absence of a negative gain equal to -1 corresponding to the changed signal, is shown. of sign obtained at point D for the interfering signal and for this reason, symbolically carrying the sign +, this signal being obtained after FM demodulation, of course.
Au point F, on a représenté la somme, grâce au coupleur 0-τι, somme algébrique entre le signal représenté au point D et le signal représenté au point E, le signal délivré au point F correspondant à celui du spectre du seul signal utile, le signal numérique débarrassé du spectre TV brouilleur, après soustraction, ce signal pouvant alors être démodulé pour son utilisation ou application dans le cadre de la diffusion du programme TV interactif précédemment cité.At point F, the sum has been represented, using the 0-τι coupler, an algebraic sum between the signal represented at point D and the signal represented at point E, the signal delivered at point F corresponding to that of the spectrum of the only useful signal, the digital signal cleared of the interfering TV spectrum, after subtraction, this signal then being able to be demodulated for its use or application within the framework of the broadcasting of the interactive TV program mentioned above.
On a ainsi décrit un dispositif de réduction du brouillage de transmission hertzienne d'un signal utile dans un réseau tel qu'un réseau TV interactif, par exemple, dans lequel, grâce à la démodulation de chaque signal radiofré- quence reçu dans sa norme et sa modulation d'origine, à l'alignement en temps et en amplitude des signaux obtenus en bande de base, suite à cette démodulation, puis à la sous¬ traction des signaux ainsi obtenus, le signal brouilleur peut ainsi être sensiblement atténué ou éliminé. Au contrai¬ re, tout signal utile superposé dans le spectre de l'un des canaux reçus n'est pas supprimé par la soustraction ainsi opérée et peut être récupéré pour des applications ultérieu¬ res.We have thus described a device for reducing the interference of radio transmission of a useful signal in a network such as an interactive TV network, for example, in which, by virtue of the demodulation of each radiofrequency signal received in its standard and its original modulation, in time and amplitude alignment of the signals obtained in baseband, following this demodulation, and then under the pulling of the signals thus obtained, the interfering signal can thus be substantially attenuated or eliminated. On the contrary, any useful signal superimposed in the spectrum of one of the channels received is not deleted by the subtraction thus operated and can be recovered for later applications.
Le dispositif, objet de la présente invention, permet d'améliorer l'efficacité spectrale d'une bande de radiodiffusion en rendant celle-ci apte à la transmission de nouveaux services, quelle qu'en soit son occupation. The device, object of the present invention, makes it possible to improve the spectral efficiency of a broadcasting band by making it suitable for the transmission of new services, whatever its occupation.

Claims

REVENDICATIONS
1. Dispositif de réduction du brouillage de trans¬ mission hertzienne d'un signal utile, transmis vers un récepteur, ce signal utile étant altéré par un signal brouilleur présent simultanément, au temps de propagation près, sur un réseau hertzien terrestre et satellitaire, caractérisé en ce que ce dispositif comprend, au niveau réception :1. Device for reducing interference from radio transmission of a useful signal transmitted to a receiver, this useful signal being altered by an interfering signal present simultaneously, to the nearest propagation time, on a terrestrial and satellite radio network, characterized in that this device comprises, at the reception level:
- une première voie de réception du signal utile en présence du signal brouilleur délivrant un signal utile reçu en présence du brouilleur ;- A first channel for receiving the useful signal in the presence of the interfering signal delivering a useful signal received in the presence of the interferer;
- une deuxième voie de réception du signal brouil¬ leur engendré par duplication retardée du signal brouilleur transmis par le réseau satellite, délivrant un signal brouilleur reçu semblable au signal brouilleur présent avec le signal utile dans la première voie ;- A second channel for receiving the scrambled signal generated by delayed duplication of the interfering signal transmitted by the satellite network, delivering a received interfering signal similar to the interfering signal present with the useful signal in the first channel;
- des moyens soustracteurs du signal brouilleur reçu du signal utile en présence du signal brouilleur, ce qui permet de délivrer un signal utile reçu exempt de signal brouilleur.means for subtracting the interfering signal received from the useful signal in the presence of the interfering signal, which makes it possible to deliver a useful signal received free of an interfering signal.
2. Dispositif selon la revendication 1, caractérisé en ce que ladite première voie comprend, connectés en cascade :2. Device according to claim 1, characterized in that said first channel comprises, connected in cascade:
- une antenne de réception terrestre, - un démodulateur en bande de base,- a terrestrial reception antenna, - a baseband demodulator,
- un dispositif d'égalisation,- an equalization device,
- un circuit inverseur de gain -1.- a gain-inverting circuit -1.
3. Dispositif selon la revendication 1 ou 2, caractérisé en ce que, au niveau réception, ladite deuxième voie comprend, connectés en cascade :3. Device according to claim 1 or 2, characterized in that, at the reception level, said second channel comprises, connected in cascade:
- une antenne de réception satellite,- a satellite reception antenna,
- un démodulateur de canal satellite en bande de base;- a baseband satellite channel demodulator;
- un dispositif d'égalisation, - un circuit retardateur permettant de compenser le temps de propagation du signal brouilleur transmis et de délivrer le signal brouilleur reçu.- an equalization device, - a delay circuit making it possible to compensate for the propagation time of the interfering signal transmitted and for deliver the received interfering signal.
4. Procédé de réduction du brouillage de transmis¬ sion intervenue d'un signal utile transmis vers un récepteur et altéré par un signal brouilleur présent simultanément au temps de propagation près sur un réseau hertzien terrestre et satellitaire, caractérisé en ce qu'il consiste simultané¬ ment :4. Method for reducing interference from transmission of a useful signal transmitted to a receiver and altered by an interfering signal present simultaneously to the nearest propagation time on a terrestrial and satellite radio network, characterized in that it consists of simultaneous ¬:
- à recevoir le signal utile en présence du signal brouilleur pour délivrer un signal utile reçu en présence du brouilleur ;- receiving the useful signal in the presence of the interfering signal to deliver a useful signal received in the presence of the interfering;
- à recevoir par duplication retardée le signal brouilleur transmis par le réseau satellite pour délivrer un signal brouilleur reçu semblable au signal brouilleur présent avec le signal utile ; et - à soustraire le signal brouilleur reçu du signal utile en présence du signal brouilleur, ce qui permet de délivrer un signal utile reçu exempt de signal brouilleur.- to receive by delayed duplication the interfering signal transmitted by the satellite network to deliver a received interfering signal similar to the interfering signal present with the useful signal; and - subtracting the interfering signal received from the useful signal in the presence of the interfering signal, which makes it possible to deliver a useful signal received free of an interfering signal.
5. Utilisation d'un dispositif de réduction du brouillage de transmission hertzienne d'un signal utile, notamment dans un réseau TV interactif, le signal utile engendré par un usager au cours de la diffusion d'un programme TV interactif étant régénéré au niveau d'une station d'environ pour la transmission vers une station terrestre source ou intermédiaire. 5. Use of a device for reducing interference from radio transmission of a useful signal, in particular in an interactive TV network, the useful signal generated by a user during the broadcasting of an interactive TV program being regenerated at level d '' a station of about for transmission to a source or intermediate earth station.
EP96941099A 1995-12-06 1996-12-03 Method and device for reducing rf transmission interference and use thereof in an interactive television network Withdrawn EP0808529A1 (en)

Applications Claiming Priority (3)

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FR9514417A FR2742283B1 (en) 1995-12-06 1995-12-06 METHOD AND DEVICE FOR REDUCING INTERFERENCE OF A WIRELESS TRANSMISSION IN A NETWORK
FR9514417 1995-12-06
PCT/FR1996/001917 WO1997021277A1 (en) 1995-12-06 1996-12-03 Method and device for reducing rf transmission interference and use thereof in an interactive television network

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FR2742283A1 (en) 1997-06-13

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