EP0837574A1 - Method for selecting channels in a RDS receiver - Google Patents

Method for selecting channels in a RDS receiver Download PDF

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Publication number
EP0837574A1
EP0837574A1 EP97410092A EP97410092A EP0837574A1 EP 0837574 A1 EP0837574 A1 EP 0837574A1 EP 97410092 A EP97410092 A EP 97410092A EP 97410092 A EP97410092 A EP 97410092A EP 0837574 A1 EP0837574 A1 EP 0837574A1
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EP
European Patent Office
Prior art keywords
frequency
station
signal
level
frequencies
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EP97410092A
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German (de)
French (fr)
Inventor
Franck Roche
Maurizio Tonella
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STMicroelectronics SA
STMicroelectronics SRL
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STMicroelectronics SA
SGS Thomson Microelectronics SA
STMicroelectronics SRL
SGS Thomson Microelectronics SRL
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Publication of EP0837574A1 publication Critical patent/EP0837574A1/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04H—BROADCAST COMMUNICATION
    • H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
    • H04H20/20—Arrangements for broadcast or distribution of identical information via plural systems
    • H04H20/22—Arrangements for broadcast of identical information via plural broadcast systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04H—BROADCAST COMMUNICATION
    • H04H2201/00—Aspects of broadcast communication
    • H04H2201/10—Aspects of broadcast communication characterised by the type of broadcast system
    • H04H2201/13—Aspects of broadcast communication characterised by the type of broadcast system radio data system/radio broadcast data system [RDS/RBDS]

Definitions

  • the present invention relates to a conforming receiver standards for data transmission by radio RDS ("Radio Data
  • the invention relates more particularly to a method selection of the best frequency among several frequencies alternatives provided by a station.
  • the RDS system is used in particular by stations radio transmitting in frequency modulation (FM) which, to be able cover a territory, require several transmitters suitably distributed. Generally, these transmitters spread use different frequencies. Such a radio station transmits by RDS a list of alternative frequencies corresponding at the frequencies of the transmitters covering the territory. So a RDS receiver that moves outside the area covered by a first transmitter to enter the area covered by a second transmitter can automatically select frequency of the second transmitter in order to continue receiving the same station in good conditions.
  • FM frequency modulation
  • FIG. 1 shows a simplified architecture of classic RDS receiver.
  • This receiver includes a tuner to frequency modulation 10 which cooperates with a loop phase lock 12 to lock onto a frequency corresponding to a selected station.
  • Tuner 10 provides an MPX "multiplex" signal to a decoding circuit 14 stereo and audio processing.
  • This circuit 14 which can be made from the TDA7340G circuit manufactured by the company SGS-Thomson Microelectronics, provides the final audio signal.
  • a RDS 16 processor which can be realized from circuits of the ST728X family manufactured by SGS-Thomson Microelectronics, receives the MPX signal from tuner 10 in order to extract the RDS information, and a Q signal (for example "S-Meter") indicative of the quality of the signal received.
  • the processor RDS 16 is associated with a memory 17 and is provided for controlling circuit 14 and phase locked loop 12 of the as described below.
  • Figure 2 shows a flowchart illustrating the execution of a classic program executed by the processor RDS 16 to select the best frequency reception of a predetermined RDS station.
  • the processor 16 receives regularly by RDS the alternative frequencies and a station identifier listened to. These alternative frequencies and the identifier are stored in the memory 17.
  • the processor 16 checks in the level of the signal received using the Q signals. 100, when the signal level becomes bad, the processor 16 runs a frequency readjustment program. In 102, the sound is suppressed at audio circuit 14 so that the various frequency changes that will take place do not disturb not the user.
  • the signal level is checked. If the level is bad, which happens of course the first time, we select in 106 an alternative frequency in the table in memory 17, on which the tuner 10 is adjusted. then again at 104 the signal level. If he is still bad, we select the following alternative frequency at 106, and this until the signal level is good at 104. So, in 108, we try to synchronize on the RDS signal which should be carried by the new frequency. If the attempt fails, it means that the selected frequency corresponds to a station that does not broadcast in RDS, and therefore that this station is not the station the user was listening to. So in 106, we select the next frequency in the table and we check again the level of the signal received at 104.
  • reception of the station listened to cannot be improved because the reception conditions are bad.
  • the station identifier in the data transmitted by RDS by comparing it to the identifier of the station listened to, stored in the memory 17. If the identifier is not correct, which corresponds to the case where the selected station transmits well in RDS but does not correspond not at the station that the user was listening to, we select in 106 the next frequency in the table. However, if the identifier is good, we found the new frequency corresponding to the station listened to. So processor 16 hands over the sound in 112 and starts to wait for a bad signal level in 100.
  • An object of the present invention is to reduce the duration of the alternative frequency search process.
  • a frequency selection method of an RDS receiver comprising the steps of monitoring the level of the signal received for a station being listened to, and when the signal level becomes bad, to select, from a group of frequencies alternatives stored in a table, the frequency that provides the maximum signal level for the station being listened to.
  • the process further includes the consistent step even if the signal level received for the station listened to is good, to be selected regularly a successive frequency of the table in order to measure the level of the corresponding received signal, this selection taking place temporarily and briefly enough to do not audibly disturb the signal received for the station listened to.
  • highest measured levels are assigned to frequencies corresponding to the table, the method further comprising the step consisting, when the level of the signal received for the listened to station becomes bad, select a frequency successive of the table in descending order of the measured levels until the corresponding received signal carries RDS information corresponding to the station being listened to.
  • the levels are assigned to the frequencies of the table in reordering frequencies in the table by levels decreasing.
  • the receiver output signal is suppressed before performing a frequency selection.
  • the present invention is based on a pre-research of the best alternative frequencies while listening normal of a station, this pre-search being carried out without disturb the user. So when the signal becomes bad, we already know the best alternative frequencies, so you only need to check them to find the one corresponding to the station listened to, instead of browsing the whole table. This results in a noticeable reduction in time necessary for the final frequency finding process alternative.
  • FIG. 3A represents a flowchart illustrating the best alternative frequency pre-search process according to the present invention. This pre-search process is put implemented periodically by the RDS 16 processor, even if the received signal level is good.
  • the processor measures the signal level and assigns this level to the selected alternative frequency. Of preferably, this assignment is achieved by reordering the frequencies in the table in descending order of levels.
  • the duration of the sound suppression must be less than about 8 ms. Indeed, the human ear is insensitive to sound suppressions of this duration. this is fully achievable using a locking loop phase based on the TDA7327 circuit which has a time of typical stabilization of 400 ⁇ s and 800 ⁇ s in the worst case.
  • stabilization at the selected alternative frequency in 206 then stabilization again at the frequency listened to in 210 lasts at most 2 ms, while measuring the signal level and assigning the measurement to the selected frequency are software operations that do not last longer than 1 ms.
  • FIG. 3B represents a flowchart illustrating a final search process for the best frequency alternative using the pre-research described in relation to Figure 3A.
  • the flowchart in Figure 3B is similar to that of FIG. 2, and similar operations are indicated by the same references.
  • the processor 16 While periodically performing the pre-search according to the flow diagram of FIG. 3A, the processor 16 checks in signal level permanently at 100. When the level becomes bad, we delete the sound at 102 and, according to the invention, we selects in 104 'the affected frequency of the maximum level. This frequency was previously found during the pre-search operations. If, as mentioned previously, the levels are assigned by reordering frequencies in the table, just 104 'select the frequency which is at the first address of the table. With such an assignment of levels, the frequency providing the maximum level is found immediately. However, if level assignment was done by storing levels in the table with their respective frequencies, these levels should be read and compared to each other to find the maximum level.
  • the first frequency alternative i.e. the one for which we found the maximum level
  • the operation will have lasted at least the stabilization time of the phase locked loop on new frequency selected in 104 'and the signal synchronization time RDS in 108.
  • the synchronization operation is the longest; it can last 100 ms in a conventional receiver. So the sound suppression time is around 100 ms, which is audible but is much less annoyance than if the removal had been of the order of a second.
  • the first frequency selected in 104 'does not correspond to the station listened to, this which is detected in 108 or 110. So, in 106 ', we select the affected alternate frequency of the level immediately lower than that of the previously selected frequency. A such selection is made by selecting the following address from the table in case the frequencies have been reordered in depending on the levels assigned to them.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Circuits Of Receivers In General (AREA)
  • Channel Selection Circuits, Automatic Tuning Circuits (AREA)

Abstract

The method involves monitoring the level of a received signal. An alternative tuning frequency can be selected from among a group of frequencies stored in a table according to the received signal level. Even if the received signal level is of good quality, a successive frequency from the table is regularly selected in order to measure the corresponding received signal level. This selection is temporary and sufficiently short to not disturb the audible quality of the received signal. When the signal level deteriorates, successive frequencies are selected in order of decreasing signal strength and used for data transmission.

Description

La présente invention concerne un récepteur conforme aux normes de transmission de données par radio RDS ("Radio Data System"). L'invention concerne plus particulièrement un procédé de sélection de la meilleure fréquence parmi plusieurs fréquences alternatives fournies par une station.The present invention relates to a conforming receiver standards for data transmission by radio RDS ("Radio Data The invention relates more particularly to a method selection of the best frequency among several frequencies alternatives provided by a station.

Le système RDS est utilisé notamment par des stations radio émettant en modulation de fréquence (FM) qui, pour pouvoir couvrir un territoire, nécessitent plusieurs émetteurs convenablement répartis. Généralement, ces émetteurs répartis utilisent des fréquences différentes. Une telle station radio émet par RDS une liste de fréquences alternatives correspondant aux fréquences des émetteurs couvrant le territoire. Ainsi, un récepteur RDS qui se déplace hors de la zone couverte par un premier émetteur pour pénétrer dans la zone couverte par un deuxième émetteur peut automatiquement sélectionner la fréquence du deuxième émetteur afin de continuer à recevoir la même station dans de bonnes conditions.The RDS system is used in particular by stations radio transmitting in frequency modulation (FM) which, to be able cover a territory, require several transmitters suitably distributed. Generally, these transmitters spread use different frequencies. Such a radio station transmits by RDS a list of alternative frequencies corresponding at the frequencies of the transmitters covering the territory. So a RDS receiver that moves outside the area covered by a first transmitter to enter the area covered by a second transmitter can automatically select frequency of the second transmitter in order to continue receiving the same station in good conditions.

La figure 1 représente une architecture simplifiée de récepteur RDS classique. Ce récepteur comprend un syntoniseur à modulation de fréquence 10 qui coopère avec une boucle à verrouillage de phase 12 pour se caler sur une fréquence correspondant à une station sélectionnée. Le syntoniseur 10 fournit un signal "multiplex" MPX à un circuit 14 de décodage stéréo et de traitement audio. Ce circuit 14, qui peut être réalisé à partir du circuit TDA7340G fabriqué par la société SGS-Thomson Microelectronics, fournit le signal audio final. Un processeur RDS 16, qui peut être réalisé à partir de circuits de la famille ST728X fabriqués par la société SGS-Thomson Microelectronics, reçoit du syntoniseur 10 le signal MPX afin d'en extraire les informations RDS, et un signal Q (par exemple "S-Meter") indicatif de la qualité du signal reçu. Le processeur RDS 16 est associé à une mémoire 17 et est prévu pour commander le circuit 14 et la boucle à verrouillage de phase 12 de la manière décrite ci-après.Figure 1 shows a simplified architecture of classic RDS receiver. This receiver includes a tuner to frequency modulation 10 which cooperates with a loop phase lock 12 to lock onto a frequency corresponding to a selected station. Tuner 10 provides an MPX "multiplex" signal to a decoding circuit 14 stereo and audio processing. This circuit 14, which can be made from the TDA7340G circuit manufactured by the company SGS-Thomson Microelectronics, provides the final audio signal. A RDS 16 processor, which can be realized from circuits of the ST728X family manufactured by SGS-Thomson Microelectronics, receives the MPX signal from tuner 10 in order to extract the RDS information, and a Q signal (for example "S-Meter") indicative of the quality of the signal received. The processor RDS 16 is associated with a memory 17 and is provided for controlling circuit 14 and phase locked loop 12 of the as described below.

La figure 2 représente un organigramme illustrant le déroulement d'un programme classique exécuté par le processeur RDS 16 permettant de sélectionner la meilleure fréquence de réception d'une station RDS prédéterminée.Figure 2 shows a flowchart illustrating the execution of a classic program executed by the processor RDS 16 to select the best frequency reception of a predetermined RDS station.

Le processeur 16 reçoit régulièrement par RDS les fréquences alternatives et un identificateur de la station écoutée. Ces fréquences alternatives et l'identificateur sont stockées dans la mémoire 17. Le processeur 16 vérifie en permanence le niveau du signal reçu à l'aide des signaux Q. En 100, lorsque le niveau du signal devient mauvais, le processeur 16 exécute un programme de réajustement de fréquence. En 102, le son est supprimé au niveau du circuit audio 14 de sorte que les divers changements de fréquence qui vont s'opérer ne perturbent pas l'utilisateur.The processor 16 receives regularly by RDS the alternative frequencies and a station identifier listened to. These alternative frequencies and the identifier are stored in the memory 17. The processor 16 checks in the level of the signal received using the Q signals. 100, when the signal level becomes bad, the processor 16 runs a frequency readjustment program. In 102, the sound is suppressed at audio circuit 14 so that the various frequency changes that will take place do not disturb not the user.

En 104, le niveau du signal est vérifié. Si le niveau est mauvais, ce qui se produit bien entendu la première fois, on sélectionne en 106 une fréquence alternative dans la table en mémoire 17, sur laquelle se règle le syntoniseur 10. On vérifie alors de nouveau en 104 le niveau du signal. S'il est encore mauvais, on sélectionne la fréquence alternative suivante en 106, et ceci jusqu'à ce que le niveau du signal soit bon en 104. Alors, en 108, on tente de se synchroniser sur le signal RDS qui devrait être véhiculé par la nouvelle fréquence. Si la tentative échoue, cela signifie que la fréquence sélectionnée correspond à une station qui n'émet pas en RDS, et donc que cette station n'est pas la station que l'utilisateur écoutait. Alors, en 106, on sélectionne la fréquence suivante dans la table et on vérifie de nouveau le niveau du signal reçu en 104.At 104, the signal level is checked. If the level is bad, which happens of course the first time, we select in 106 an alternative frequency in the table in memory 17, on which the tuner 10 is adjusted. then again at 104 the signal level. If he is still bad, we select the following alternative frequency at 106, and this until the signal level is good at 104. So, in 108, we try to synchronize on the RDS signal which should be carried by the new frequency. If the attempt fails, it means that the selected frequency corresponds to a station that does not broadcast in RDS, and therefore that this station is not the station the user was listening to. So in 106, we select the next frequency in the table and we check again the level of the signal received at 104.

Si la liste de fréquences alternatives est épuisée en 106, la réception de la station écoutée ne peut être améliorée car les conditions de réception sont mauvaises. On peut alors prendre diverses mesures, telles que rétablir la fréquence initiale et fixer un délai avant de mesurer de nouveau le niveau du signal en 100.If the list of alternative frequencies is exhausted in 106, reception of the station listened to cannot be improved because the reception conditions are bad. We can then take various measures, such as restoring the frequency initial and set a time limit before re-measuring the level of the signal in 100.

En 110, si le niveau du signal est bon et que la station émet en RDS, on vérifie l'identificateur de la station dans les données transmises par RDS en le comparant à l'identificateur de la station écoutée, stocké dans la mémoire 17. Si l'identificateur n'est pas bon, ce qui correspond au cas où la station sélectionnée émet bien en RDS mais ne correspond pas à la station que l'utilisateur écoutait, on sélectionne en 106 la fréquence suivante dans la table. Par contre, si l'identificateur est bon, on a trouvé la nouvelle fréquence correspondant à la station écoutée. Alors, le processeur 16 remet le son en 112 et se met à attendre un niveau de signal mauvais en 100.In 110, if the signal level is good and the station transmits in RDS, we check the station identifier in the data transmitted by RDS by comparing it to the identifier of the station listened to, stored in the memory 17. If the identifier is not correct, which corresponds to the case where the selected station transmits well in RDS but does not correspond not at the station that the user was listening to, we select in 106 the next frequency in the table. However, if the identifier is good, we found the new frequency corresponding to the station listened to. So processor 16 hands over the sound in 112 and starts to wait for a bad signal level in 100.

Pendant le processus de recherche de fréquence de la figure 2, l'utilisateur ne peut pas écouter la station. Or, ce processus peut se révéler long (de l'ordre de la seconde) dans le cas où la bonne fréquence n'est pas parmi les premières fréquences de la table. Cette lenteur de la recherche est essentiellement due au fait qu'il faut attendre la stabilisation de la boucle à verrouillage de phase 12 à chaque sélection d'une nouvelle fréquence avant de pouvoir continuer le processus. La durée de recherche n'est pas significativement réduite, même si l'on utilise une boucle à verrouillage de phase à stabilisation rapide, telle que celle qui peut être réalisée à partir du circuit TDA7327 fabriqué par la société SGS-Thomson Microelectronics.During the frequency search process of the Figure 2, the user cannot listen to the station. Now, this process can be long (in the order of a second) in the if the right frequency is not among the first table frequencies. This slowness of research is essentially due to the fact that we have to wait for stabilization of the phase-locked loop 12 each time a new frequency before you can continue the process. The search time is not significantly reduced, even if a stabilized phase locked loop is used fast, such as can be done from TDA7327 circuit manufactured by SGS-Thomson Microelectronics.

Un objet de la présente invention est de réduire la durée du processus de recherche de fréquence alternative.An object of the present invention is to reduce the duration of the alternative frequency search process.

Cet objet est atteint selon l'invention grâce à un procédé de sélection de fréquence d'un récepteur RDS, comprenant les étapes consistant à surveiller le niveau du signal reçu pour une station écoutée et, lorsque le niveau du signal devient mauvais, à sélectionner, parmi un groupe de fréquences alternatives stockées dans une table, la fréquence qui fournit le niveau de signal maximal pour la station écoutée. Le procédé comprend en outre l'étape consistant, même si le niveau du signal reçu pour la station écoutée est bon, à sélectionner régulièrement une fréquence successive de la table afin de mesurer le niveau du signal reçu correspondant, cette sélection s'effectuant temporairement et de manière suffisamment brève pour ne pas perturber de manière audible le signal reçu pour la station écoutée.This object is achieved according to the invention thanks to a frequency selection method of an RDS receiver, comprising the steps of monitoring the level of the signal received for a station being listened to, and when the signal level becomes bad, to select, from a group of frequencies alternatives stored in a table, the frequency that provides the maximum signal level for the station being listened to. The process further includes the consistent step even if the signal level received for the station listened to is good, to be selected regularly a successive frequency of the table in order to measure the level of the corresponding received signal, this selection taking place temporarily and briefly enough to do not audibly disturb the signal received for the station listened to.

Selon un mode de réalisation de la présente invention, les niveaux mesurés les plus élevés sont affectés aux fréquences correspondantes de la table, le procédé comprenant en outre l'étape consistant, lorsque le niveau du signal reçu pour la station écoutée devient mauvais, à sélectionner une fréquence successive de la table par ordre décroissant des niveaux mesurés jusqu'à ce que le signal reçu correspondant véhicule des informations RDS correspondant à la station écoutée.According to an embodiment of the present invention, highest measured levels are assigned to frequencies corresponding to the table, the method further comprising the step consisting, when the level of the signal received for the listened to station becomes bad, select a frequency successive of the table in descending order of the measured levels until the corresponding received signal carries RDS information corresponding to the station being listened to.

Selon un mode de réalisation de la présente invention, les niveaux sont affectés aux fréquences de la table en réordonnant les fréquences dans la table par niveaux décroissants.According to an embodiment of the present invention, the levels are assigned to the frequencies of the table in reordering frequencies in the table by levels decreasing.

Selon un mode de réalisation de la présente invention, le signal de sortie du récepteur est supprimé avant d'opérer une sélection de fréquence.According to an embodiment of the present invention, the receiver output signal is suppressed before performing a frequency selection.

Ces objets, caractéristiques et avantages, ainsi que d'autres de la présente invention seront exposés en détail dans la description suivante de modes de réalisation particuliers faite à titre non-limitatif en relation avec les figures jointes parmi lesquelles :

  • les figures 1 et 2, précédemment décrites sont destinées à illustrer l'état de la technique et le problème que vise à résoudre la présente invention ; et
  • les figures 3A et 3B représentent des organigrammes illustrant le procédé de recherche de fréquence alternative selon la présente invention.
    • These objects, characteristics and advantages, as well as others of the present invention will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:
  • Figures 1 and 2, previously described are intended to illustrate the state of the art and the problem which the present invention seeks to solve; and
  • FIGS. 3A and 3B represent flowcharts illustrating the method of finding an alternative frequency according to the present invention.

    • La présente invention est basée sur une prérecherche régulière des meilleures fréquences alternatives pendant l'écoute normale d'une station, cette prérecherche s'effectuant sans perturber l'utilisateur. Ainsi, lorsque le signal devient mauvais, on connaít déjà les meilleures fréquences alternatives, de sorte qu'il suffit seulement de les vérifier pour trouver celle qui correspond à la station écoutée, au lieu de parcourir toute la table. Il en résulte une réduction notable du temps nécessaire au processus de recherche finale de la fréquence alternative.The present invention is based on a pre-research of the best alternative frequencies while listening normal of a station, this pre-search being carried out without disturb the user. So when the signal becomes bad, we already know the best alternative frequencies, so you only need to check them to find the one corresponding to the station listened to, instead of browsing the whole table. This results in a noticeable reduction in time necessary for the final frequency finding process alternative.

    La figure 3A représente un organigramme illustrant le procédé de prérecherche de la meilleure fréquence alternative selon la présente invention. Ce processus de prérecherche est mis en oeuvre périodiquement par le processeur RDS 16, même si le niveau du signal reçu est bon.FIG. 3A represents a flowchart illustrating the best alternative frequency pre-search process according to the present invention. This pre-search process is put implemented periodically by the RDS 16 processor, even if the received signal level is good.

    En 200, on attend une nouvelle période de prérecherche. Lorsque cette période est atteinte, le processeur 16 sauvegarde en 202 la fréquence écoutée, supprime le son en 204 et sélectionne l'une des fréquences alternatives dans la table en 206. A chaque nouvelle période, le processeur sélectionne une nouvelle fréquence alternative de la table en 206, de manière à parcourir régulièrement, à raison d'une fréquence alternative par période, toutes les fréquences de la table.In 200, we await a new period of pre-research. When this period is reached, the processor 16 saves in 202 the frequency listened to, suppresses the sound in 204 and select one of the alternative frequencies in the table by 206. At each new period, the processor selects a new alternative frequency of the table in 206, so that browse regularly, at an alternative frequency by period, all frequencies of the table.

    En 208, le processeur mesure le niveau du signal et affecte ce niveau à la fréquence alternative sélectionnée. De préférence, cette affectation est réalisée en réordonnant les fréquences dans la table par ordre décroissant de niveaux.In 208, the processor measures the signal level and assigns this level to the selected alternative frequency. Of preferably, this assignment is achieved by reordering the frequencies in the table in descending order of levels.

    En 210, la fréquence écoutée précédemment sauvegardée est rétablie et on rétablit le son en 212 après la stabilisation de la boucle à verrouillage de phase 12.In 210, the frequency listened to previously saved is restored and the sound is restored at 212 after stabilization phase lock loop 12.

    Pour pouvoir procéder de cette manière sans gêner l'utilisateur, il faut que la durée de la suppression du son soit inférieure à environ 8 ms. En effet, l'oreille humaine est insensible à des suppressions de son de cette durée. Ceci est tout à fait réalisable en utilisant une boucle à verrouillage de phase à base du circuit TDA7327 qui présente un temps de stabilisation typique de 400 µs et de 800 µs dans le pire cas. Ainsi, la stabilisation à la fréquence alternative sélectionnée en 206 puis la stabilisation de nouveau à la fréquence écoutée en 210 dure au plus 2 ms, tandis que la mesure du niveau du signal et l'affectation de la mesure à la fréquence sélectionnée sont des opérations logicielles qui ne durent pas plus de 1 ms.To be able to proceed in this way without hindering user, the duration of the sound suppression must be less than about 8 ms. Indeed, the human ear is insensitive to sound suppressions of this duration. this is fully achievable using a locking loop phase based on the TDA7327 circuit which has a time of typical stabilization of 400 µs and 800 µs in the worst case. Thus, stabilization at the selected alternative frequency in 206 then stabilization again at the frequency listened to in 210 lasts at most 2 ms, while measuring the signal level and assigning the measurement to the selected frequency are software operations that do not last longer than 1 ms.

    La figure 3B représente un organigramme illustrant un processus de recherche finale de la meilleure fréquence alternative exploitant la prérecherche décrite en relation avec la figure 3A. L'organigramme de la figure 3B est similaire à celui de la figure 2, et des opérations similaires sont indiquées par des mêmes références.FIG. 3B represents a flowchart illustrating a final search process for the best frequency alternative using the pre-research described in relation to Figure 3A. The flowchart in Figure 3B is similar to that of FIG. 2, and similar operations are indicated by the same references.

    Tout en effectuant périodiquement la prérecherche selon l'organigramme de la figure 3A, le processeur 16 vérifie en permanence le niveau du signal en 100. Lorsque le niveau devient mauvais, on supprime le son en 102 et, selon l'invention, on sélectionne en 104' la fréquence affectée du niveau maximal. Cette fréquence a été trouvée préalablement au cours des opérations de prérecherche. Si, comme on l'a mentionné précédemment, l'affectation des niveaux s'opère en réordonnant les fréquences dans la table, il suffit en 104' de sélectionner la fréquence qui se trouve à la première adresse de la table. Avec une telle affectation des niveaux, la fréquence fournissant le niveau maximal est trouvée immédiatement. Par contre, si l'affectation des niveaux était effectuée en stockant les niveaux dans la table avec leurs fréquences respectives, ces niveaux devraient être lus et comparés les uns aux autres pour trouver le niveau maximal.While periodically performing the pre-search according to the flow diagram of FIG. 3A, the processor 16 checks in signal level permanently at 100. When the level becomes bad, we delete the sound at 102 and, according to the invention, we selects in 104 'the affected frequency of the maximum level. This frequency was previously found during the pre-search operations. If, as mentioned previously, the levels are assigned by reordering frequencies in the table, just 104 'select the frequency which is at the first address of the table. With such an assignment of levels, the frequency providing the maximum level is found immediately. However, if level assignment was done by storing levels in the table with their respective frequencies, these levels should be read and compared to each other to find the maximum level.

    Comme précédemment, on vérifie successivement en 108 s'il existe bien un signal RDS à la fréquence sélectionnée et en 110 si ce signal RDS véhicule bien l'identificateur correspondant à la station écoutée. Si c'est le cas, la fréquence sélectionnée est la bonne et on remet le son en 112.As before, we successively check at 108 if there is an RDS signal at the selected frequency and 110 if this RDS signal conveys the corresponding identifier to the station being listened to. If so, the selected frequency is the right one and we put the sound back to 112.

    Dans la plupart des cas, la première fréquence alternative, c'est-à-dire celle pour laquelle on a trouvé le niveau maximal, correspondra à la station écoutée. Dans ce cas, l'opération aura duré au moins le temps de stabilisation de la boucle à verrouillage de phase sur la nouvelle fréquence sélectionnée en 104' et le temps de synchronisation sur le signal RDS en 108. L'opération de synchronisation est la plus longue ; elle peut durer 100 ms dans un récepteur classique. Ainsi, la durée de suppression du son est de l'ordre de 100 ms, ce qui est audible mais constitue une gêne beaucoup moins importante que si la suppression avait été de l'ordre de la seconde.In most cases, the first frequency alternative, i.e. the one for which we found the maximum level, will correspond to the station listened to. In that case, the operation will have lasted at least the stabilization time of the phase locked loop on new frequency selected in 104 'and the signal synchronization time RDS in 108. The synchronization operation is the longest; it can last 100 ms in a conventional receiver. So the sound suppression time is around 100 ms, which is audible but is much less annoyance than if the removal had been of the order of a second.

    Dans un cas moins probable, la première fréquence sélectionnée en 104' ne correspond pas à la station écoutée, ce qui est détecté en 108 ou en 110. Alors, en 106', on sélectionne la fréquence alternative affectée du niveau immédiatement inférieur à celui de la fréquence précédemment sélectionnée. Une telle sélection s'opère en sélectionnant l'adresse suivante de la table dans le cas où les fréquences ont été réordonnées en fonction des niveaux qui leur ont été affectés.In a less likely case, the first frequency selected in 104 'does not correspond to the station listened to, this which is detected in 108 or 110. So, in 106 ', we select the affected alternate frequency of the level immediately lower than that of the previously selected frequency. A such selection is made by selecting the following address from the table in case the frequencies have been reordered in depending on the levels assigned to them.

    Après la stabilisation de la boucle à verrouillage de phase sur la fréquence sélectionnée en 106', on vérifie de nouveau si cette fréquence correspond à la station écoutée en 108 et en 110. Si ce n'est pas le cas, on sélectionne une troisième fréquence en 106', et ainsi de suite.After stabilization of the locking loop phase on the frequency selected in 106 ', we check again if this frequency corresponds to the station listened to in 108 and in 110. If this is not the case, we select a third frequency in 106 ', and so on.

    En pratique, il est inutile d'affecter des niveaux à toutes les fréquences de la table. Il suffit d'affecter des niveaux à seulement deux ou trois fréquences car la probabilité pour que la bonne fréquence ne soit pas parmi les deux ou trois fréquences qui fournissent les meilleurs niveaux est infime.In practice, there is no point in assigning levels to all frequencies of the table. Just assign levels at only two or three frequencies because the probability so that the right frequency is not among the two or three frequencies that provide the best levels is miniscule.

    Si exceptionnellement la bonne fréquence ne se trouve pas parmi celles qui fournissent les meilleurs niveaux, on procède, pour les fréquences alternatives restantes, de manière classique (figure 2) jusqu'à la fin de la liste.If exceptionally the right frequency is not found not among those that provide the best levels, we proceed, for the remaining alternative frequencies, so classic (Figure 2) until the end of the list.

    Claims (4)

    Procédé de sélection de fréquence d'un récepteur RDS, comprenant les étapes consistant à surveiller (100) le niveau du signal reçu pour une station écoutée et, lorsque le niveau du signal devient mauvais, à sélectionner (106, 104', 106'), parmi un groupe de fréquences alternatives stockées dans une table (17), la fréquence qui fournit le niveau de signal maximal pour la station écoutée ; caractérisé en ce qu'il comprend l'étape consistant, même si le niveau du signal reçu pour la station écoutée est bon, à sélectionner régulièrement (206) une fréquence successive de la table afin de mesurer le niveau du signal reçu correspondant, cette sélection s'effectuant temporairement et de manière suffisamment brève pour ne pas perturber de manière audible le signal reçu pour la station écoutée.Frequency selection method of a receiver RDS, comprising the steps of monitoring (100) the signal level received for a station being listened to, and when the signal level becomes bad, select (106, 104 ', 106 '), among a group of alternative frequencies stored in a table (17), the frequency which provides the signal level maximum for the station listened to; characterized in that it includes the consistent step even if the level of the received signal for the station listened to is good, to be selected regularly (206) a successive frequency of the table in order to measure the level of the corresponding received signal, this selection being made temporarily and briefly enough so as not to audibly disturb the signal received for the station listened to. Procédé selon la revendication 1, caractérisé en ce que les niveaux mesurés les plus élevés sont affectés (208) aux fréquences correspondantes de la table, le procédé comprenant en outre l'étape consistant, lorsque le niveau du signal reçu pour la station écoutée devient mauvais, à sélectionner (106') une fréquence successive de la table par ordre décroissant des niveaux mesurés jusqu'à ce que le signal reçu correspondant véhicule des informations RDS correspondant à la station écoutée (108, 110).Method according to claim 1, characterized in that that the highest measured levels are assigned (208) to corresponding frequencies of the table, the method comprising in in addition to the consistent step, when the level of the signal received for the station listened to becomes bad, select (106 ') a successive frequency of the table in descending order of measured levels until the corresponding received signal conveys RDS information corresponding to the station being listened to (108, 110). Procédé selon la revendication 2, caractérisé en ce que les niveaux sont affectés aux fréquences de la table en réordonnant les fréquences dans la table par niveaux décroissants.Method according to claim 2, characterized in that that the levels are assigned to the frequencies of the table in reordering frequencies in the table by levels decreasing. Procédé selon l'une quelconque des revendications 1 à 3, caractérisé en ce que le signal de sortie du récepteur est supprimé (204, 102) avant d'opérer une sélection de fréquence.Method according to any of claims 1 to 3, characterized in that the output signal from the receiver is deleted (204, 102) before making a frequency selection.
    EP97410092A 1996-08-30 1997-08-26 Method for selecting channels in a RDS receiver Withdrawn EP0837574A1 (en)

    Applications Claiming Priority (2)

    Application Number Priority Date Filing Date Title
    FR9610801 1996-08-30
    FR9610801A FR2753021B1 (en) 1996-08-30 1996-08-30 METHOD FOR SELECTING FREQUENCY IN AN RDS RECEIVER

    Publications (1)

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    EP0837574A1 true EP0837574A1 (en) 1998-04-22

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    EP (1) EP0837574A1 (en)
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    Citations (4)

    * Cited by examiner, † Cited by third party
    Publication number Priority date Publication date Assignee Title
    WO1988004862A1 (en) * 1986-12-19 1988-06-30 Telefunken Fernseh Und Rundfunk Gmbh Process for transmitting and/or evaluating on the receiver side information inside a radio signal
    EP0484246A1 (en) * 1990-10-31 1992-05-06 Lg Electronics Inc. High speed method for searching an alternative frequency in a radio system
    EP0502500A1 (en) * 1991-03-04 1992-09-09 BECKER GmbH Method for tuning of a radio receiver, using RDS-data
    EP0507096A2 (en) * 1991-03-29 1992-10-07 Pioneer Electronic Corporation A RDS receiver

    Patent Citations (4)

    * Cited by examiner, † Cited by third party
    Publication number Priority date Publication date Assignee Title
    WO1988004862A1 (en) * 1986-12-19 1988-06-30 Telefunken Fernseh Und Rundfunk Gmbh Process for transmitting and/or evaluating on the receiver side information inside a radio signal
    EP0484246A1 (en) * 1990-10-31 1992-05-06 Lg Electronics Inc. High speed method for searching an alternative frequency in a radio system
    EP0502500A1 (en) * 1991-03-04 1992-09-09 BECKER GmbH Method for tuning of a radio receiver, using RDS-data
    EP0507096A2 (en) * 1991-03-29 1992-10-07 Pioneer Electronic Corporation A RDS receiver

    Also Published As

    Publication number Publication date
    FR2753021A1 (en) 1998-03-06
    JPH10190503A (en) 1998-07-21
    FR2753021B1 (en) 1998-11-27

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