EP0837574A1 - Procédé de sélection de fréquence dans un récepteur RDS - Google Patents
Procédé de sélection de fréquence dans un récepteur RDS Download PDFInfo
- 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
- Authority
- EP
- European Patent Office
- Prior art keywords
- frequency
- station
- signal
- level
- frequencies
- 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- Withdrawn
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Classifications
-
- 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
Description
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.
- 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).
- 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.
- 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.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR9610801 | 1996-08-30 | ||
FR9610801A FR2753021B1 (fr) | 1996-08-30 | 1996-08-30 | Procede de selection de frequence dans un recepteur rds |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0837574A1 true EP0837574A1 (fr) | 1998-04-22 |
Family
ID=9495435
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP97410092A Withdrawn EP0837574A1 (fr) | 1996-08-30 | 1997-08-26 | Procédé de sélection de fréquence dans un récepteur RDS |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0837574A1 (fr) |
JP (1) | JPH10190503A (fr) |
FR (1) | FR2753021B1 (fr) |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1988004862A1 (fr) * | 1986-12-19 | 1988-06-30 | Telefunken Fernseh Und Rundfunk Gmbh | Procede pour transmettre et/ou evaluer cote reception des informations a l'interieur d'un signal radio |
EP0484246A1 (fr) * | 1990-10-31 | 1992-05-06 | Lg Electronics Inc. | Procédé à grande vitesse de recherche d'une fréquence alternative dans un système radio |
EP0502500A1 (fr) * | 1991-03-04 | 1992-09-09 | BECKER GmbH | Méthode pour l'accord d'un récepteur radio, utilisant des information RDS |
EP0507096A2 (fr) * | 1991-03-29 | 1992-10-07 | Pioneer Electronic Corporation | Récepteur RDS |
-
1996
- 1996-08-30 FR FR9610801A patent/FR2753021B1/fr not_active Expired - Fee Related
-
1997
- 1997-08-22 JP JP24022197A patent/JPH10190503A/ja not_active Withdrawn
- 1997-08-26 EP EP97410092A patent/EP0837574A1/fr not_active Withdrawn
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1988004862A1 (fr) * | 1986-12-19 | 1988-06-30 | Telefunken Fernseh Und Rundfunk Gmbh | Procede pour transmettre et/ou evaluer cote reception des informations a l'interieur d'un signal radio |
EP0484246A1 (fr) * | 1990-10-31 | 1992-05-06 | Lg Electronics Inc. | Procédé à grande vitesse de recherche d'une fréquence alternative dans un système radio |
EP0502500A1 (fr) * | 1991-03-04 | 1992-09-09 | BECKER GmbH | Méthode pour l'accord d'un récepteur radio, utilisant des information RDS |
EP0507096A2 (fr) * | 1991-03-29 | 1992-10-07 | Pioneer Electronic Corporation | Récepteur RDS |
Also Published As
Publication number | Publication date |
---|---|
FR2753021A1 (fr) | 1998-03-06 |
FR2753021B1 (fr) | 1998-11-27 |
JPH10190503A (ja) | 1998-07-21 |
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Date | Code | Title | Description |
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PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
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RTI1 | Title (correction) | ||
RAP3 | Party data changed (applicant data changed or rights of an application transferred) |
Owner name: STMICROELECTRONICS S.R.L. Owner name: SGS-THOMSON MICROELECTRONICS S.A. |
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Effective date: 19980925 |
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