EP0845873A1 - Méthode de commutation vers des fréquences alternatives pendant les pauses dans le programme diffusé dans un récepteur de radiodiffusion - Google Patents

Méthode de commutation vers des fréquences alternatives pendant les pauses dans le programme diffusé dans un récepteur de radiodiffusion Download PDF

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Publication number
EP0845873A1
EP0845873A1 EP96830601A EP96830601A EP0845873A1 EP 0845873 A1 EP0845873 A1 EP 0845873A1 EP 96830601 A EP96830601 A EP 96830601A EP 96830601 A EP96830601 A EP 96830601A EP 0845873 A1 EP0845873 A1 EP 0845873A1
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EP
European Patent Office
Prior art keywords
radio
receiver
threshold value
frequency
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Withdrawn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
EP96830601A
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German (de)
English (en)
Inventor
Maurizio Tonella
Carlo Boisio
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.)
STMicroelectronics SRL
Original Assignee
STMicroelectronics SRL
SGS Thomson Microelectronics SRL
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 STMicroelectronics SRL, SGS Thomson Microelectronics SRL filed Critical STMicroelectronics SRL
Priority to EP96830601A priority Critical patent/EP0845873A1/fr
Publication of EP0845873A1 publication Critical patent/EP0845873A1/fr
Withdrawn legal-status Critical Current

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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 method and to a device for switching frequencies in a radio receiver and, in particular, to a method according to the preamble to the main claim.
  • Radio receivers can reconstruct audio information contained in a modulated signal having a carrier frequency equal to a selected frequency to which the receiver is tuned.
  • Known receivers for example, those included in car radios, commonly switch briefly to alternative frequencies periodically in order to perform management operations; in particular, the radio receiver disables the sound output, switches to an alternative frequency, performs the necessary operations, resets the previous frequency and then re-enables the sound. If the duration of the period in which the sound is disabled is short enough, the interruption is not noticed by listener since the human ear is insensitive to sound blanks of a duration shorter than about 8 ms.
  • a problem with known radio receivers is that these systems generate interference (noise) during frequency switchings. In particular, they may generate a slight crack (pop) when the sound is interrupted. In fact, the level of the signal at the moment when the sound is switched on again is generally different from that at the moment when it was interrupted, so that this difference is perceived by the listener in the form of a slight sound discontinuity.
  • the object of the present invention is to prevent the aforementioned problems.
  • a method as described in the main claim is provided.
  • the method according to the present invention reduces the noise generated in the course of frequency switchings.
  • Statistical analyses have in fact shown a very high probability that, after the detection of a pause, the signal will remain in that condition for a period long enough for the frequency switching.
  • the level of the signal at the moment when the sound is switched on again and at the moment when it is interrupted are therefore generally both at a low level so that no discontinuity of sound is noticed by the listener.
  • this shows a radio receiver 100 and, in particular, an RDS (Radio Data System), AF (alternative frequencies), frequency-modulated (FM) radio receiver; the present invention can also, however, be implemented with the use of radio receivers of other types, for example, receivers which are not of the RDS type, or receivers with amplitude modulation (AM), and the like.
  • the RDS system is used by radio stations which serve various transmitters at different frequencies in order to cover a certain territory.
  • An RDS radio station transmits a list of alternative frequencies corresponding to the various transmitters and this list is stored in the radio receiver when it is tuned to a frequency of that station.
  • the radio receiver which, typically, is included in a car radio, moves from an area covered by one transmitter to another area covered by a transmitter transmitting at a different frequency, it detects a worsening in the quality of the signal received and automatically selects the frequency of the new emitter from the list of alternative frequencies to enable the same radio station to be received in the best possible manner.
  • the radio receiver 100 is generally connected to an aerial 110 which can receive radio waves present in the environment and supply corresponding modulated radio signals to the receiver 100.
  • the radio receiver 100 includes a tuner 120 which, of the various modulated radio signals supplied by the aerial 110, can receive that signal which has a carrier frequency corresponding to a selected frequency of a preselected radio station. Tuning to the selected frequency is carried out with the use of a phase-locked loop (or PLL) 130 coupled to the tuner 120; the PLL 130 is preferably of the rapid stabilization type (with a stabilization time of the order of a few hundreds of ⁇ s) constituted, for example, by the circuit TDA7427 manufactured by SGS-Thomson Microelectronics S.r.l.
  • the radio signal selected which is constituted by a multiplexed baseband signal (MPX) is supplied to an audio processor 140, for example, constituted by the circuit TDA7340G manufactured by SGS-Thomson Microelectronics S.r.l., which outputs an audio signal; the audio signal is amplified by means of a suitable low-frequency amplifier 150 constituted, for example, by the circuit TDA7385 manufactured by SGS-Thomson Microelectronics S.r.l., which sets in operation one or more output actuators (loud speakers) 160 which transform the electrical data received into sound waves.
  • MPX multiplexed baseband signal
  • the radio signal selected is also supplied to an RDS processor 170, for example, constituted by the circuit ST728X manufactured by SGS-Thomson Microelectronics S.r.l.; alternatively, a microprocessor is provided and controls a separate RDS device (constituted, for example, by the circuit TDA7330B manufactured by SGS-Thomson Microelectronics S.r.l.), or equivalent logic means.
  • the RDS processor 170 also receives from the tuner 120 a signal (Q) containing tuning parameters indicative of the quality of the signal received.
  • the RDS processor 170 is associated with a memory 180 and can send control signals to the audio processor 140 and to the PLL 130.
  • this is a flow chart of the switching method 200 according to the present invention.
  • the method 200 is carried out continuously during normal listening to the radio station and starts at box 205 in which the RDS processor 170 monitors the level of the radio signal selected in order to detect a pause, that is, a condition in which the level of the radio signal selected remains below a threshold value for a period of time having a duration greater than a further threshold value;
  • the signal-level threshold value is typically between a few tens and a few hundreds of mV, and the period-duration threshold value varies from a few hundreds of ⁇ s to a few tens of ms.
  • this monitoring is effected, for example, with the use of a pause terminal of the audio processor 140 which outputs a logic value 1 (typically equal to the supply voltage, for example, 5V relative to a reference value or earth) when the level of the radio signal selected is below the threshold value or, otherwise, a logic value 0 (typically 0V).
  • a logic value 1 typically equal to the supply voltage, for example, 5V relative to a reference value or earth
  • a logic value 0 typically 0V
  • the RDS processor 170 monitors the value of the voltage at the terminals of the capacitor and detects the pause condition when the voltage exceeds a threshold value corresponding to logic level 1 (for example, 2.5 V).
  • the charge time of the capacitor is directly proportional to the RC constant of the circuit which includes it. If the value of R (for example 50 k ⁇ ) is known, the period-duration threshold value can be set by suitable dimensioning of the capacitor; typically, it has a capacitance of between a few tens and a few hundreds of nF.
  • the pause condition is detected by means of dedicated circuitry which measures directly the level of the radio signal selected.
  • the RDS processor 170 If the RDS processor 170 detects a pause, it switches the radio receiver 100 one or more times in order to perform management operations. In particular, the method goes to box 210 in which the radio receiver 100 disables the production of the audio signal (audio muting). In box 220, the RDS processor 170 sends a suitable command to the PLL 130 so as to switch the tuner 120 to a different alternative frequency in order to perform various management operations in box 225.
  • these operations are constituted by measurements of tuning parameters, for example, a parameter indicative of the strength of the antenna field (S meter), a parameter which indicates if the signal received is direct or reflected (multipath), a parameter indicative of the noise level (noise detector), a parameter which indicates if the station is tuned or not (stop station), or other parameters indicative of the quality of the signal received; these measurements are, for example, applied to the alternative frequencies of a station transmitting in RDS in order to speed up the search for the frequency of a new transmitter.
  • these management operations consist in the detection of management signals transmitted on a predetermined frequency, and the like.
  • a frequency corresponding to the station selected is reset in box 230.
  • this frequency corresponds to the selected frequency stored in the memory 180; in an RDS system in which the measurement of the tuning parameters of an alternative frequency of the radio station has detected that that frequency is better than the one currently selected, the alternative frequency is adopted as the new frequency of the radio station.
  • the audio signal is re-established (unmuting) in box 235. The method then returns to box 205 in order to repeat the monitoring of the radio-signal level continuously.
  • the present invention can therefore be implemented without boxes 210 (audio muting) and 235 (unmuting).
  • the method goes to box 240 in which the RDS processor 170 checks if a "time-out" condition, in which the time elapsed from the last frequency switching has exceeded a certain threshold value, typically of the order of a few ms, has arisen.
  • a certain threshold value typically of the order of a few ms
  • box 240 If the box 240 detects a time-out condition, it forces a frequency switch by going to box 210 described above; otherwise, the method returns directly to box 205.
  • This optional feature offers the advantage of preventing the frequency of the switchings from becoming too low, for example, if a radio signal with few pauses is selected.
  • the method 200 further comprises the step of dynamically varying the signal-level and/or period-duration threshold values in dependence on the frequency of the pauses. For example, the method increases a suitable counter value (initially zero) each time a pause (not forced by a time-out) is detected. Periodically, for example every 10 seconds, the method checks the counter value; if the value is low (for example, a few units) the signal-level and/or period-duration threshold value is reduced, whereas if the value is high (for example, greater than a hundred) the signal-level and/or period-duration threshold value is increased.
  • a suitable counter value initially zero
  • the method checks the counter value; if the value is low (for example, a few units) the signal-level and/or period-duration threshold value is reduced, whereas if the value is high (for example, greater than a hundred) the signal-level and/or period-duration threshold value is increased.
  • This optional feature enables the frequency of the frequency switchings to be adapted to audio signals of different types; for example, in the case of a very high mean radio-signal level, such as in rock music, it is also possible to detect pause conditions in which the signal level remains below a value which, although it is quite high in absolute terms, is quite low in relation to the mean signal level.
  • the signal-level threshold value is modified by suitable programming of the audio processor 140; the processor of the embodiment illustrated in fact allows various threshold values (for example, 20, 40, 80 and 160 mV) used for determining the value output at the pause terminal to be selected by means of a suitable control signal.
  • the radio receiver 100 also enables the period-duration threshold value to be modified, however, with the use of dedicated circuitry (including, essentially, transistors and capacitors) which can selectively vary the value of the capacitance connected to the pause terminal.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Circuits Of Receivers In General (AREA)
EP96830601A 1996-11-29 1996-11-29 Méthode de commutation vers des fréquences alternatives pendant les pauses dans le programme diffusé dans un récepteur de radiodiffusion Withdrawn EP0845873A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP96830601A EP0845873A1 (fr) 1996-11-29 1996-11-29 Méthode de commutation vers des fréquences alternatives pendant les pauses dans le programme diffusé dans un récepteur de radiodiffusion

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP96830601A EP0845873A1 (fr) 1996-11-29 1996-11-29 Méthode de commutation vers des fréquences alternatives pendant les pauses dans le programme diffusé dans un récepteur de radiodiffusion

Publications (1)

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EP0845873A1 true EP0845873A1 (fr) 1998-06-03

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EP96830601A Withdrawn EP0845873A1 (fr) 1996-11-29 1996-11-29 Méthode de commutation vers des fréquences alternatives pendant les pauses dans le programme diffusé dans un récepteur de radiodiffusion

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001056178A2 (fr) * 2000-01-29 2001-08-02 Robert Bosch Gmbh Procede pour cacher des interruptions de reproduction de signaux de radiodiffusion reçus
EP1271816A3 (fr) * 2001-06-21 2007-01-03 Harman Becker Automotive Systems GmbH Procédé de recherche d'une fréquence dans un récepteur radio
EP1867077A1 (fr) * 2005-04-05 2007-12-19 Nokia Corporation Procede et dispositif d'emission en modulation de frequence de donnees audio a destination d'un recepteur radio mf a fonctionnalite srd
WO2009120165A1 (fr) 2008-03-27 2009-10-01 Panasonic Automotive Systems Company Of America Division Of Panasonic Corporation Of North America Procédé et appareil permettant d'adapter de façon dynamique la sensibilité d'un syntoniseur fm à un environnement local dans le cadre d'un système à syntoniseur unique
US20090247099A1 (en) * 2008-03-27 2009-10-01 Panasonic Automotive Systems Company Of America, Division Of Panasonic Corporation Of North America Method and apparatus for dynamically adapting FM tuner sensitivity to a local environment for a single-tuner system
US8774860B2 (en) 2005-04-05 2014-07-08 Nokia Corporation Method and device for low-power FM transmission of audio data to RDS capable FM radio receiver

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0497115A2 (fr) * 1991-02-01 1992-08-05 Blaupunkt-Werke GmbH Récepteur de radiodiffusion avec RDS
DE4304179A1 (en) * 1992-02-25 1993-08-26 Volkswagen Ag Radio data signal receiver for car radio - uses stored reception signals for supplying reproduction circuit during switching between different signals to maintain reception quality.
DE4233758C1 (de) * 1992-10-07 1994-01-27 Blaupunkt Werke Gmbh Rundfunkempfänger
EP0597492A1 (fr) * 1992-11-13 1994-05-18 CLARION Co., Ltd. Récepteur pour radiodiffusion RDS

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0497115A2 (fr) * 1991-02-01 1992-08-05 Blaupunkt-Werke GmbH Récepteur de radiodiffusion avec RDS
DE4304179A1 (en) * 1992-02-25 1993-08-26 Volkswagen Ag Radio data signal receiver for car radio - uses stored reception signals for supplying reproduction circuit during switching between different signals to maintain reception quality.
DE4233758C1 (de) * 1992-10-07 1994-01-27 Blaupunkt Werke Gmbh Rundfunkempfänger
EP0597492A1 (fr) * 1992-11-13 1994-05-18 CLARION Co., Ltd. Récepteur pour radiodiffusion RDS

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001056178A3 (fr) * 2000-01-29 2002-04-25 Klaus-Erwin Groeger Procede pour cacher des interruptions de reproduction de signaux de radiodiffusion reçus
US6961548B2 (en) 2000-01-29 2005-11-01 Robert Bosch Gmbh Method for masking interruptions on playback of received radio signals
WO2001056178A2 (fr) * 2000-01-29 2001-08-02 Robert Bosch Gmbh Procede pour cacher des interruptions de reproduction de signaux de radiodiffusion reçus
EP1271816A3 (fr) * 2001-06-21 2007-01-03 Harman Becker Automotive Systems GmbH Procédé de recherche d'une fréquence dans un récepteur radio
EP1867077A4 (fr) * 2005-04-05 2010-10-13 Nokia Corp Procede et dispositif d'emission en modulation de frequence de donnees audio a destination d'un recepteur radio mf a fonctionnalite srd
EP1867077A1 (fr) * 2005-04-05 2007-12-19 Nokia Corporation Procede et dispositif d'emission en modulation de frequence de donnees audio a destination d'un recepteur radio mf a fonctionnalite srd
US8774860B2 (en) 2005-04-05 2014-07-08 Nokia Corporation Method and device for low-power FM transmission of audio data to RDS capable FM radio receiver
US20090247099A1 (en) * 2008-03-27 2009-10-01 Panasonic Automotive Systems Company Of America, Division Of Panasonic Corporation Of North America Method and apparatus for dynamically adapting FM tuner sensitivity to a local environment for a single-tuner system
EP2258060A1 (fr) * 2008-03-27 2010-12-08 Panasonic Automotive Systems Company of America Division of Panasonic Corporation of North America Procédé et appareil permettant d'adapter de façon dynamique la sensibilité d'un syntoniseur fm à un environnement local dans le cadre d'un système à syntoniseur unique
EP2258060A4 (fr) * 2008-03-27 2011-09-21 Panasonic Automotive Systems Co America Division Of Panasonic Corp North America Procédé et appareil permettant d'adapter de façon dynamique la sensibilité d'un syntoniseur fm à un environnement local dans le cadre d'un système à syntoniseur unique
US8406715B2 (en) 2008-03-27 2013-03-26 Panasonic Automotive Systems of America, division of Panasonic Corporation of North America Method and apparatus for dynamically adapting FM tuner sensitivity to a local environment for a single-tuner system
US20130165065A1 (en) * 2008-03-27 2013-06-27 Panasonic Automotive Systems Company Of America, Division Of Panasonic Corporation Of North America Method and apparatus for dynamically adapting fm tuner sensitivity to a local environment for a single-tuner system
CN101911550B (zh) * 2008-03-27 2014-01-08 松下北美公司美国分部松下汽车系统公司 用于单调谐器系统的使fm调谐器灵敏度动态适应于本地环境的方法
WO2009120165A1 (fr) 2008-03-27 2009-10-01 Panasonic Automotive Systems Company Of America Division Of Panasonic Corporation Of North America Procédé et appareil permettant d'adapter de façon dynamique la sensibilité d'un syntoniseur fm à un environnement local dans le cadre d'un système à syntoniseur unique
US9577609B2 (en) * 2008-03-27 2017-02-21 Panasonic Automotive Systems Company Of America, Division Of Panasonic Corporation Of North America Method and apparatus for dynamically adapting FM tuner sensitivity to a local environment for a single-tuner system

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